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Highly Efficient Transformation of Tar Model Compounds into Hydrogen by a Ni–Co Alloy Nanocatalyst During Tar Steam Reforming
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Download Hi-Res ImageDownload to MS-PowerPointCite This:Environ. Sci. Technol. 2024, 58, 7, 3540-3551
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Physico-Chemical Treatment and Resource Recovery

Highly Efficient Transformation of Tar Model Compounds into Hydrogen by a Ni–Co Alloy Nanocatalyst During Tar Steam Reforming
Ni-Co 合金纳米催化剂在焦油蒸汽重整过程中将焦油模型化合物高效转化为氢气
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  • Junjie Chen
    Junjie Chen
    State Key Laboratory of Urban Water Resource and Environment, National Engineering Research Center for Safe Disposal and Resources Recovery of Sludge, School of Environment, Harbin Institute of Technology, Harbin 150090, China
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  • Yongxiao Liu
    Yongxiao Liu
    State Key Laboratory of Urban Water Resource and Environment, National Engineering Research Center for Safe Disposal and Resources Recovery of Sludge, School of Environment, Harbin Institute of Technology, Harbin 150090, China
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  • Zhengrui Chen
    Zhengrui Chen
    State Key Laboratory of Urban Water Resource and Environment, National Engineering Research Center for Safe Disposal and Resources Recovery of Sludge, School of Environment, Harbin Institute of Technology, Harbin 150090, China
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  • Junrong Yue*
    Junrong Yue
    State Key Laboratory of Multi-Phase Complex System, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190, China
    *E-mail: jryue@ipe.ac.cn. Tel: (86) 010 8262 9912. Fax: (86) 010 8262 9912.
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  • Yu Tian
    Yu Tian
    State Key Laboratory of Urban Water Resource and Environment, National Engineering Research Center for Safe Disposal and Resources Recovery of Sludge, School of Environment, Harbin Institute of Technology, Harbin 150090, China
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  • Chengzhi Zheng
    Chengzhi Zheng
    Guangdong Yuehai Water Investment Co., Ltd, Shenzhen 518021, China
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  • Jun Zhang*
    Jun Zhang
    State Key Laboratory of Urban Water Resource and Environment, National Engineering Research Center for Safe Disposal and Resources Recovery of Sludge, School of Environment, Harbin Institute of Technology, Harbin 150090, China
    *E-mail: hitsunyboy@126.com. Tel: (86) 451 8628 3077. Fax: (86) 451 8628 3077.
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    Orcidhttps://orcid.org/0000-0002-5683-777X
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Environmental Science & Technology

Cite this: Environ. Sci. Technol. 2024, 58, 7, 3540–3551
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https://doi.org/10.1021/acs.est.3c08857
Published February 6, 2024
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Abstract 抽象

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Hydrogen (H2) production from coal and biomass gasification was considered a long-term and viable way to solve energy crises and global warming. Tar, generated as a hazardous byproduct, limited its large-scale applications by clogging and corroding gasification equipment. Although catalytic steam reforming technology was used to convert tar into H2, catalyst deactivation restricted its applicability. A novel nanocatalyst was first synthesized by the modified sol–gel method using activated biochar as the support, nickel (Ni) as the active component, and cobalt (Co) as the promoter for converting tar into H2. The results indicated that a high H2 yield of 263.84 g H2/kg TMCs (Tar Model Compounds) and TMC conversion of almost 100% were obtained over 6% Ni–4% Co/char, with more than 30% increase in hydrogen yield compared to traditional catalysts. Moreover, 6% Ni–4% Co/char exhibited excellent resistance to carbon deposition by removing the nucleation sites for graphite formation, forming stable Ni–Co alloy, and promoting the char gasification reaction; resistance to oxidation deactivation due to the high oxygen affinity of Co and reduction of the oxidized nickel by H2 and CO; resistance to sintering deactivation by strengthened interaction between Ni and Co, high specific surface area (920.61 m2/g), and high dispersion (7.3%) of Ni nanoparticles. This work provided a novel nanocatalyst with significant potential for long-term practical applications in the in situ conversion of tar into H2 during steam reforming.
从煤炭和生物质气化中生产氢气 （H2） 被认为是解决能源危机和全球变暖的长期可行方法。焦油作为一种有害的副产品产生，通过堵塞和腐蚀气化设备限制了其大规模应用。尽管使用催化蒸汽重整技术将焦油转化为 H2，但催化剂失活限制了其适用性。首先通过改性溶胶-凝胶法合成了一种新型纳米催化剂，以活化生物炭为载体，镍 （Ni） 为活性成分，钴 （Co） 为促进剂，将焦油转化为 H2。结果表明，在 6% Ni–4% Co/char 上，获得了 263.84 g H2/kg TMC（焦油模型化合物）的高 H2 产率和几乎 100% 的 TMC 转化率，与传统催化剂相比，氢气产率提高了 30% 以上。此外，6% Ni–4% Co/char 通过去除石墨形成的成核位点，形成稳定的 Ni-Co 合金并促进 char 气化反应，表现出优异的抗碳沉积性;由于 Co 的高氧亲和力和 H2 和 CO 还原氧化镍，抗氧化失活;通过加强 Ni 和 Co 之间的相互作用、高比表面积 （920.61 m2/g） 和 Ni 纳米颗粒的高分散性 （7.3%） 来抵抗烧结失活。这项工作提供了一种新型纳米催化剂，在蒸汽重整过程中将焦油原位转化为 H2 中具有重要的长期实际应用潜力。

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Synopsis 概要

Minimal research exists on the development of catalysts with excellent antideactivation performance for converting tar into hydrogen. This study provides reliable strategies for in situ tar conversion into hydrogen during coal and biomass gasification.
关于开发具有优异抗灭活性能的催化剂以将焦油转化为氢气的研究很少。本研究为煤和生物质气化过程中原位焦油转化为氢气提供了可靠的策略。

Introduction 介绍

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The International Energy Agency (IEA) has estimated that the world’s energy demand will rise by 30% by 2040 along with the rapid development of the global economy. (1) Addressing the energy crisis and environmental issues, such as global warming, caused by the excessive consumption of fossil fuels has become a common goal of the international community. More than 130 countries globally have proposed their own carbon neutrality goals by 2050 or 2060. (2) Hydrogen has been regarded as a potential energy vector to achieve global greenhouse gas reduction targets (3,4) due to its high gravimetric heating value of 142 MJ/kg and clean combustion product. (5) Coal and biomass energy are the main fossil fuels and the fourth largest energy resource apart from three traditional fossil fuels in the world. Moreover, a few studies have experimentally proven that hydrogen production from coal and biomass was a long-term and viable way to solve energy crises and environmental pollution. (6,7)
国际能源署 （IEA） 估计，随着全球经济的快速发展，到 2040 年，世界能源需求将增长 30%。（1） 解决因过度消耗化石燃料而引起的能源危机和全球变暖等环境问题已成为国际社会的共同目标。全球 130 多个国家/地区提出了到 2050 年或 2060 年实现碳中和的目标。（2） 氢气因其 142 MJ/kg 的高重量热值和清洁燃烧产物，一直被视为实现全球温室气体减排目标的潜在能源载体 （3,4）。（5） 煤炭和生物质能是主要的化石燃料，是除三种传统化石燃料外的世界第四大能源资源。此外，一些研究通过实验证明，从煤炭和生物质中制氢是解决能源危机和环境污染的长期可行的方法。（6,7）
Among the hydrogen production processes, gasification hydrogen production (GHP) and anaerobic hydrogen fermentation (AHF) were recognized as two economically effective approaches, providing the higher potential to become competitive on a large scale in the near future. However, GHP technology is superior to AHF technology in terms of hydrogen yield and production rate. (8,9) It is to note that the efficiency in H2 production of AHF could be easily affected by inoculants, environmental factors, and microbial community. (10,11) Previous studies indicated that the H2 yield from biomass and coal can reach 0–20 g H2/kg substrate by AHF within a few hours to days. (12,13) Compared to AHF, the H2 yield of 30–300 g H2/kg substrate can be stably obtained from biomass and coal by GHP within a few seconds to minutes. (14,15) However, there was still no significant progress in large-scale commercial applications of coal or biomass gasification. The major issue is the tar (condensing pointing <300 °C) generated as a hazardous byproduct during the process, (16) which leads to the corrosion and blocking of downstream equipment and thus causes serious impacts on the long-term operation of the gasification system. (17) In addition, aromatic compounds in tar, such as polycyclic aromatic hydrocarbons and benzene, pose environmental and toxicological risks. (18) As a consequence, the efficient removal and targeted conversion of tar into clean H2 emerge as crucial considerations for the large-scale implementation of GHP.
在制氢工艺中，气化制氢 （GHP） 和厌氧氢发酵 （AHF） 被认为是两种经济有效的方法，为在不久的将来大规模竞争提供了更大的潜力。然而，GHP 技术在氢气产量和生产率方面优于 AHF 技术。（8,9） 需要注意的是，AHF 的 H2 生产效率很容易受到接种剂、环境因素和微生物群落的影响。（10,11） 先前的研究表明，AHF 的生物质和煤的 H2 产量可以在几小时到几天内达到 0-20 g H2/kg 底物。（12,13） 与 AHF 相比，GHP 可以在几秒钟到几分钟内从生物质和煤中稳定获得 30-300 g H2/kg 底物的 H2 产量。（14,15） 然而，在煤炭或生物质气化的大规模商业应用方面仍然没有取得重大进展。主要问题是焦油（冷凝点 <300 °C) generated as a hazardous byproduct during the process, （16）），导致下游设备腐蚀和堵塞，从而对气化系统的长期运行造成严重影响。（17） 此外，焦油中的芳香族化合物，如多环芳烃和苯，会带来环境和毒理学风险。（18） 因此，有效去除焦油并有针对性地转化为清洁 H2 成为大规模实施 GHP 的关键考虑因素。
Tar catalytic reforming has been considered as a cost-effective and sustainable way for converting tar into hydrogen at a relatively low temperature (600–900 °C). (19) Natural minerals (calcined dolomites, limestones, alkali, and earth alkali metal oxides) (20,21) and nickel-based catalysts (22,23) are now being considered as the most common catalysts. Compared to natural minerals catalysts, Ni-based catalysts are more attractive due to its good catalytic performance and relatively low cost, whereas the rapid deactivation of catalysts restricted its industrial application. (22,24) In order to improve the catalytic stability of Ni-based catalysts, promoters, such as Fe, Mg, Co, and Ce, have been introduced. (25) Exemplifying this, Liang et al. prepared the 10Ni@ADM-0.1 and 10Ni1Co@ADM-0.1 catalysts for methane reforming and observed that 10Ni1Co@ADM-0.1 catalysts exhibited more stable catalytic performance and higher H2 selectivity due to the formation of Ni–Co alloy. (26) Recently, biochar, another byproduct of biomass pyrolysis, has emerged as a promising catalyst support due to its diverse physical and chemical properties. (27) Biochar itself exhibits inherent tar catalytic activity, attributed to alkaline and alkaline earth metals (AAEMs) in the biochar such as K, Mg, and Ca. (17,28) Wang et al. synthesized municipal sludge char-based catalyst (Fe–Ni/MSC) and reached a higher toluene conversion of 92.6% with a significant H2 content of 73.6% at 800 °C. (29) Despite great efforts to enhance tar catalytic reforming performance, studies on the development of catalysts with excellent antideactivation ability and a comprehensive analysis of the mechanisms underlying catalysts’ antideactivation remain limited.
焦油催化重整被认为是在相对较低的温度 （600-900 °C） 下将焦油转化为氢气的一种经济高效且可持续的方法。（19） 天然矿物（煅烧白云石、石灰石、碱和土碱金属氧化物）（20,21） 和镍基催化剂 （22,23） 现在被认为是最常见的催化剂。与天然矿物催化剂相比，镍基催化剂因其良好的催化性能和相对较低的成本而更具吸引力，而催化剂的快速失活限制了其工业应用。（22,24） 为了提高镍基催化剂的催化稳定性，已经引入了 Fe、Mg、Co 和 Ce 等促进剂。（25） 例如，Liang 等人制备了用于甲烷重整的 10Ni@ADM-0.1 和 10Ni1Co@ADM-0.1 催化剂，并观察到 10Ni1Co@ADM-0.1 催化剂由于形成 Ni-Co 合金而表现出更稳定的催化性能和更高的 H2 选择性。（26） 最近，生物炭是生物质热解的另一种副产品，由于其多样化的物理和化学性质，已成为一种很有前途的催化剂载体。（27） 生物炭本身具有固有的焦油催化活性，归因于生物炭中的碱金属和碱土金属 （AAEM），如 K、Mg 和 Ca。（17,28） Wang 等人合成了城市污泥炭基催化剂 （Fe-Ni/MSC），在 800 °C 时达到了 92.6% 的较高甲苯转化率，H2 含量为 73.6%。 （29） 尽管在提高焦油催化重整性能方面做出了巨大努力，但关于开发具有优异抗脱活能力的催化剂的研究和对催化剂抗失活机制的综合分析仍然有限。
Based on the above discussion, this paper aims to prepare a novel and low-cost nanocatalyst with excellent antideactivation ability for enhancing tar in situ conversion into green hydrogen. Various nanocatalysts were synthesized by the modified citric acid sol–gel method employing KOH-activated biochar as the support, Ni as the active component, and Fe/Co/Mg as the promoters. Toluene, naphthalene, and phenol, representing three typical light tars for alkyl aromatic tar, polycyclic aromatic hydrocarbons, and heteroatom-containing compounds, were selected as the tar model compounds for catalytic steam reforming. (28,30) The effect of reaction temperature, Co loading, and recycling times (N) on TMC conversion, H2 yield, and gas quality, such as Low Heating Value (LHV) and H2/CO, were investigated in a two-stage fixed bed reactor. Furthermore, the antideactivation mechanism of Co-modified nickel nanocatalysts as the optimal catalyst was comprehensively revealed by a series of characterization using SEM-EDS, BET, XRD, XPS, TG-DTG, and Raman. This study aims to promote the large-scale implementation of coal and biomass gasification for hydrogen production and further solve energy crises and environmental issues.
基于上述讨论，本文旨在制备一种新型、低成本、具有优异抗脱活能力的纳米催化剂，以增强焦油原位转化为绿色氢。以 KOH 活化生物炭为载体，Ni 为活性组分，Fe/Co/Mg 为促进剂，采用改性柠檬酸溶胶-凝胶法合成了各种纳米催化剂。选择甲苯、萘和苯酚作为催化蒸汽重整的焦油模型化合物，分别代表烷基芳香族焦油、多环芳烃和含杂原子化合物的 3 种典型轻质焦油。（28,30） 在两级固定床反应器中研究了反应温度、Co 负载和回收时间 （N） 对 TMC 转化率、H2 产率和气体质量（如低热值 （LHV） 和 H2/CO）的影响。此外，通过使用 SEM-EDS、BET、XRD、XPS、TG-DTG 和 Raman 的一系列表征，全面揭示了共改性镍纳米催化剂作为最佳催化剂的抗灭活机制。本研究旨在推动大规模实施煤炭和生物质气化制氢，进一步解决能源危机和环境问题。

Materials and Methods 材料和方法

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Materials 材料

Pine sawdust (PS) was chosen as a natural source of biochar, as it is one of the most representative byproducts of the wood processing industry. The main information on PS and other materials were analyzed in Text S1.
松木屑 （PS） 被选为生物炭的天然来源，因为它是木材加工业最具代表性的副产品之一。文本 S1 分析了 PS 和其他材料的主要信息。

Nanocatalysts Preparation
纳米催化剂制备

The PS was dried at 80 °C for 6 h and then calcined at 600 °C for 1 h in a tubular furnace to acquire the biochar. Biochar activated using KOH (AR) improved the surface area and porosity of biochar. (31,32) Biochar preparation and KOH activation details can be observed in Text S2. The KOH-activated biochar was designated as char. The unmodified and promoter-modified nanocatalysts were prepared by the modified citric acid sol–gel method (33) using char as the support, nickel as the active component, and Fe/Co/Mg as the promoters. The preparation process of different nanocatalysts is presented in Text S3. Based on the previous research, a mass ratio of 6% between Ni and biochar was selected as the optimal loading for nickel-based catalysts. (34) The unmodified Ni-based catalyst was designated as 6% Ni/char (6% for the Ni loading, calculated by Ni mass fraction, wt %). The promoter-modified nanocatalysts were denoted as 6% Ni–x M/char (M for Fe, Co, Mg promoter, x for the promoter contents, calculated by promoter mass fraction, wt %). The prepared catalysts were stored in a desiccator.
将 PS 在 80 °C 下干燥 6 h，然后在管式炉中在 600 °C 下煅烧 1 h，得到生物炭。使用 KOH （AR） 活化的生物炭改善了生物炭的表面积和孔隙率。（31,32） 生物炭制备和 KOH 活化细节可以在文本 S2 中观察到。KOH 活化的生物炭被指定为 char。以 char 为载体，以镍为活性组分，Fe/Co/Mg 为促进剂，采用改性柠檬酸溶胶-凝胶法 （33） 制备了未修饰和促进剂修饰的纳米催化剂。不同纳米催化剂的制备过程见文本 S3。基于以往的研究，Ni 和生物炭之间 6% 的质量比被选为镍基催化剂的最佳负载。（34） 未改性的镍基催化剂被指定为 6% Ni/char（Ni 负载为 6%，以 Ni 质量分数 wt % 计算）。促进剂修饰的纳米催化剂表示为 6% Ni-x M/char（M 代表 Fe、Co、Mg 促进剂，x 代表促进剂含量，由促进剂质量分数 wt % 计算）。将制备的催化剂储存在干燥器中。

Nanocatalysts Characterization
纳米催化剂表征

The amounts of metal concentrated in the char and the metal loading of the as-prepared nanocatalysts were measured by inductively coupled plasma optical emission spectrometer (ICP-OES, Optima 8300). The structural and textural properties of nanocatalysts were illustrated by various characterizations, such as scanning electron microscopy (SEM) and Brunauer–Emmett–Teller (BET). The amount and types of coke deposited on the spent nanocatalysts were measured by Temperature-Programmed Oxidation (TPO) and Raman spectroscopy (LabRAM HR Evolution). The dispersion and chemical states of metals loaded on the nanocatalysts were performed using X-ray diffractometer (XRD) and X-ray photoelectron spectroscopy (XPS). The details of characterization parameters are shown in Text S4.
通过电感耦合等离子体发射光谱仪 （ICP-OES， Optima 8300） 测量炭中浓缩的金属量和所制备的纳米催化剂的金属负载量。纳米催化剂的结构和结构特性通过各种表征来说明，例如扫描电子显微镜 （SEM） 和 Brunauer-Emmett-Teller （BET）。通过程序升温氧化 （TPO） 和拉曼光谱 （LabRAM HR Evolution） 测量沉积在废纳米催化剂上的焦炭的数量和类型。使用 X 射线衍射仪 （XRD） 和 X 射线光电子能谱 （XPS） 对负载在纳米催化剂上的金属的分散和化学状态进行测量。特征参数的详细信息显示在文本 S4 中。

Tar Catalytic Reforming System and Procedure
焦油催化重整系统及程序

As depicted in Figure S1, the experimental setup used for tar catalytic reforming is mainly composed of a continuous feeding system, a two-stage quartz fixed-bed system, a gas supplying system, and a production collection system. The upper stage of the reactor was heated to 300 °C for the vaporization zone, while the lower reactor was controlled from 500 to 800 °C for the catalytic reforming zone with 0.5 g catalyst. Additionally, toluene or the mixture of toluene, naphthalene, and phenol (5:2:1, w/w/w) used as TMCs and deionized water were simultaneously injected into the vaporization zone by two syringe pumps. Subsequently, the vapor entered the reforming zone with the N2 flow rate of 100 mL/min and the molar steam/carbon (S/C) ratio of 3, based on the results of our previous research. (34) Two types of tar-model compounds were assigned as T-TMC and M-TMC. The liquid and gas products were collected by three N-hexane washing bottles and a 10 L aluminum foil gas bag, respectively. Each experiment was maintained for 20 min and replicated at least twice under the same conditions to ensure the repeatability of the results. The specific experimental process is shown in Text S5.
如图 S1 所示，用于焦油催化重整的实验装置主要由连续进料系统、两级石英固定床系统、供气系统和生产收集系统组成。反应器上级的汽化区加热至 300 °C，而下级反应器的催化重整区用 0.5 g 催化剂控制在 500 至 800 °C 之间。此外，通过两个注射泵将甲苯或用作 TMC 和去离子水的甲苯或甲苯、萘和苯酚的混合物（5：2：1，w/w/w）同时注入汽化区。随后，根据我们之前的研究结果，蒸汽以 N2 流速为 100 mL/min 和摩尔蒸汽/碳 （S/C） 比为 3 进入重整区。（34） 两种类型的焦油模型化合物被指定为 T-TMC 和 M-TMC。液体和气体产品分别由 3 个 N-己烷洗涤瓶和 10 L 铝箔气袋收集。每个实验维持 20 分钟，并在相同条件下至少重复两次，以确保结果的可重复性。具体的实验过程如文本 S5 所示。

Evaluation of Tar Conversion into Hydrogen
焦油转化为氢气的评估

The gas products (H2, CO, CH4, and CO2) were calculated using a gas chromatograph (GC, Agilent 7890A) equipped with a flame ionization detector (FID) and a thermal conductivity detector (TCD). Liquid samples were analyzed at gas chromatography–mass spectrometer (GC-MS, Agilent 7890A/7000B, USA) with an HP-5MS capillary column. The TMC conversion and intermediate products were determined by GC and GC-MS, respectively. The details of the GC and GC-MS parameters are described in Text S6. TMC conversion (Conversion, %), H2 yield (H2yield, g/kg TMCs), and LHV of gas product (LHV, MJ/Nm3) were calculated according to the following equations:
使用配备火焰离子化检测器 （FID） 和热导检测器 （TCD） 的气相色谱仪（GC，Agilent 7890A）计算气体产物（H2、CO、CH4 和 CO2）。使用气相色谱-质谱仪（GC-MS，Agilent 7890A/7000B，美国）和 HP-5MS 毛细管柱分析液体样品。分别通过 GC 和 GC-MS 测定 TMC 转化率和中间产物。GC 和 GC-MS 参数的详细信息在文本 S6 中描述。TMC 转化率（转化率，%）、H2 产率（H2产量，g/kg TMC）和气体产物的 LHV（LHV，MJ/Nm3）根据以下公式计算：
conversion=mtar,in−mtar,outmtar,in100%
(1)
H2yield=massofH2obtainedmtar,in100%
(2)
LHV=4.2×(25.7×αH2+30.0×αCO+85.7×αCH4)1000
(3)
where mtar,in and mtar,out is the amount of injected and unreacted TMCs, and αH2, αCO,
其中 mtar，in 和 mtar，out 是注入和未反应的 TMC 的量，而 αH2 αCO，
and αCH4 represent the volume percent (vol %) of H2, CO, and CH4 in gas product, respectively.
和 αCH4 分别表示气体产物中 H2 、 CO 和 CH4 的体积百分比 （vol %）。

Results and Discussion 结果与讨论

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Loading Concentration, Morphology, and Particle Size Distributions of Active Particles Loading on Catalysts
催化剂负载活性颗粒的负载浓度、形态和粒径分布

Combining other metals with the active metal Ni is regarded as one of the most promising strategies to improve the catalytic activity and stability of nickel-based catalysts. (25) The low price and unique physicochemical properties of transition metals (Fe, Cu, Cr, Co, etc.) and AAEMs (Mg, Ca, Sr, Ba, etc.) make them an excellent alternative to replace the noble metals (Ru, Rh, Pt, etc.) as catalyst promoters. (35) Based on the previous research, a mass ratio of 6% between Ni/Fe/Co/Mg and biochar was selected as the metal loading for catalysts. (34) According to the ICP-OES (Table S3) and XRD analysis (Figure 1c), it can be noted that the metal content of all synthesized catalysts was close to the nominal loading, which was evidence that the modified citric acid sol–gel method was successful for catalyst synthesis. Controlling the morphology and distributions of these nonnoble metal catalysts is critical to improve their performance. (36,37) In addition, the diagram of active metal Ni0 size distribution of 6% Ni/char showed that the Ni0 particles size was concentrated at 15–16 nm in Figures 1f and S2c. Furthermore, Ni0 crystallite sizes of nickel-based catalysts (15.4 nm for 6% Ni/char, 12.1 nm for 6% Ni–6% Fe/char, 14.1 nm for 6% Ni–6% Co/char, and 11.87 nm for 6% Ni–6% Mg/char) also were calculated from the full width at half height of the Ni (111) diffraction peak at 2θ = 44.50° in the XRD using the Scherrer eq (Figure 1c). (38) The appearance of Ni0 might be owing to the higher reactivity of Ni2+ with char support (carbothermal reduction) (24,39) and the reduction of citric acid. (40,41) The Ni3Fe alloy (2θ = 44.22°), (24,42) Ni–Co alloy (2θ = 44.40°) (43), and NiO–MgO solid solution (2θ = 43.15°–43.26°) (38) were also obtained, as shown in Figure 1c. The results confirmed that promoter-modified nickel catalysts prepared by the modified citric acid sol–gel method were different morphologies of bimetallic nanocatalysts (alloy and solid solution), which enhanced the activity and stability of nickel catalysts. (44)
将其他金属与活性金属 Ni 结合被认为是提高镍基催化剂催化活性和稳定性的最有前途的策略之一。（25） 过渡金属（Fe、Cu、Cr、Co 等）和 AAEMs（Mg、Ca、Sr、Ba等）的低价格和独特的物理化学性质使其成为替代贵金属（Ru、Rh、Pt 等）作为催化剂促进剂的绝佳替代品。（35） 基于前人的研究，Ni/Fe/Co/Mg 与生物炭的质量比为 6% 被选为催化剂的金属负载量。（34） 根据 ICP-OES（表 S3）和 XRD 分析（图 1c），可以注意到所有合成催化剂的金属含量都接近标称负载量，这证明了改性柠檬酸溶胶-凝胶法在催化剂合成中是成功的。控制这些非贵金属催化剂的形态和分布对于提高其性能至关重要。（36,37） 此外，6% Ni/char 的活性金属 Ni0 粒度分布图显示，在图 1f 和 S2c 中，Ni0 粒度集中在 15-16 nm 处。此外，镍基催化剂的Ni 0 微晶尺寸（6% Ni/char 为 15.4 nm，6% Ni-6% Fe/char 为 12.1 nm，6% Ni-6% Co/char 为 14.1 nm，6% Ni-6% Co/char 为 14.1 nm，6% Ni-6% Mg/char 为 11.87 nm）也是根据 XRD 中 2θ = 44.50° 处 Ni （111） 衍射峰半峰的全宽计算的（图 1c）。（38） Ni0 的出现可能是由于 Ni2+ 与焦化负载（碳热还原）（24,39） 和柠檬酸的还原具有较高的反应性。 （40,41） 还获得了 Ni3Fe 合金 （2θ = 44.22°）、（24,42） Ni-Co 合金 （2θ = 44.40°） （43） 和 NiO-MgO 固溶体 （2θ = 43.15°–43.26°） （38），如图 1c 所示。结果证实，改性柠檬酸溶胶-凝胶法制备的促进子改性镍催化剂是双金属纳米催化剂（合金和固溶体）的不同形貌，增强了镍催化剂的活性和稳定性。（44）

Figure 1 图 1

Figure 1. Effect of different catalysts on (a) T-TMC conversion and H2 yield, (b) gas yield and composition at the reforming temperature of 700 °C, and (c) XRD patterns of different catalysts and SEM-EDS analysis of (d,e) char and (f) 6% Ni/char.
图 1.不同催化剂对 （a） T-TMC 转化率和 H2 产率的影响，（b） 700 °C 重整温度下气体产率和成分，以及 （c） 不同催化剂的 XRD 图谱以及 （d，e） char 和 （f） 6% Ni/char 的 SEM-EDS 分析。

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Effect of Different Promoter-Modified Nickel Catalysts on T-TMC Catalytic Conversion into Hydrogen
不同促进剂改性镍催化剂对T-TMC催化制氢的影响

The effect of different promoter-modified nickel catalysts on the conversion of T-TMC into H2 at the reforming temperature of 700 °C is illustrated in Figure 1a. As observed, 90.43% of T-TMC conversion and 2.35 g/kg T-TMC of H2 yield were obtained using char as the catalyst, which is much higher than the T-TMC conversion (29.42%) in the thermal cracking reaction (Figure S3). The result was attributed to the large specific surface area (945.04 m2/g) and certain content AAEMs such as 1.09 wt % of K and 0.48 wt % of Mg (Figure 1d,e and Table S3). It has been reported that the catalytic performance of char was due to the porous structure for better absorbability and AAEMs concentrated in char. (17,18) As indicated, 6% Ni/char catalyst showed a higher T-TMC conversion of 92.51% and H2 yield of 33.00 g/kg T-TMC than char. Active Ni sites on char exhibited strong ability in cleavage of C–C, O–H, and C–H bonds, which promoted the conversion of T-TMC into H2. (28,45) In addition, the prevalence of nanoscale Ni particles (15–16 nm) was conducive to amplifying reaction efficiency and mitigating catalyst sintering deactivation by augmenting the dispersion of active sites. (46) Furthermore, 6% Ni/char nanocatalysts modified by different promoters (Fe, Co, and Mg) exhibited superior catalytic activity with T-TMC conversion and H2 yields being above 94.72% and 78.30 g/kg of T-TMC, respectively. The addition of promoters decreased the Ni crystallite sizes (15.4 nm for 6% Ni/char, 12.1 nm for 6% Ni–6% Fe/char, 14.1 nm for 6% Ni–6% Co/char, and 11.87 nm for 6% Ni–6% Mg/char), improved the dispersion of Ni, increased the BET surface area to form active sites (Table S2), also formed the Ni3Fe alloy, Ni–Co alloy, and NiO–MgO solid solution, which enhanced the catalytic activity and stability. (44) The highest T-TMC conversion of 98.56% and H2 yield of 103.43 g/kg T-TMC were obtained on the 6% Ni–6% Co/char nanocatalyst. Compared to Fe and Mg, the addition of Co not only caused an increase in the dispersion of Ni but also neutralized the acidity to developing the basic site. (47,48) In addition, Co has a high affinity for oxygen-containing species (CO2 and H2O), (43,49) which also enhanced the conversion of T-TMC into H2 by promoting the catalytic reforming reactions (eqs 5–10).
图 1a 说明了在 700 °C 重整温度下，不同促进剂修饰的镍催化剂对 T-TMC 转化为 H2 的影响。据观察，使用焦炭作为催化剂获得了 90.43% 的 T-TMC 转化率和 2.35 g/kg T-TMC 的 H2 产率，远高于热裂解反应中的 T-TMC 转化率 （29.42%）（图 S3）。结果归因于大比表面积 （945.04 m2/g） 和某些含量的 AAEM，例如 1.09 wt % 的 K 和 0.48 wt % 的 Mg（图 1d，e 和表 S3）。据报道，焦炭的催化性能是由于多孔结构具有更好的吸收性和焦化物中浓缩的 AAEM。（17,18） 如图所示，6% Ni/char 催化剂的 T-TMC 转化率高达 92.51%，H2 产率为 33.00 g/kg T-TMC。焦炭上的活性 Ni 位点表现出很强的 C-C 裂解能力， O-H 和 C-H 键，促进 T-TMC 转化为 H2。（28,45） 此外，纳米级 Ni 颗粒 （15-16 nm） 的普遍存在有利于通过增加活性位点的分散来提高反应效率和减轻催化剂烧结失活。（46） 此外，经不同促进剂 （Fe、Co 和 Mg） 修饰的 6% Ni/char 纳米催化剂表现出优异的催化活性，T-TMC 转化率和 H2 产率分别高于 94.72% 和 78.30 g/kg T-TMC。添加促进剂降低了 Ni 微晶尺寸（6% Ni/char 为 15.4 nm，6% Ni-6% Fe/char 为 12.1 nm，6% Ni-6% Co/char 为 14.1 nm，以及 11。87 nm 对于 6% Ni–6% Mg/char），改善了 Ni 的分散性，增加了 BET 表面积以形成活性位点（表 S2），还形成了 Ni3Fe 合金、Ni-Co 合金和 NiO-MgO 固溶体，增强了催化活性和稳定性。（44） 在 6% Ni–6% Co/char 纳米催化剂上获得了最高的 T-TMC 转化率 98.56% 和 H2 产率 103.43 g/kg T-TMC。与 Fe 和 Mg 相比，Co 的添加不仅导致 Ni 的分散性增加，而且中和了酸度以形成碱性位点。（47,48） 此外，Co 对含氧物质（CO2 和 H2O）具有高亲和力，（43,49） 这也通过促进催化重整反应（方程 5-10）增强了 T-TMC 向 H2 的转化。
The effects of different promoter-modified nickel catalysts on gas yield, gas composition (H2, CO, CO2, and CH4), and gas quality (LHV and H2/CO) at 700 °C are displayed in Figures 1 and S4, respectively. The process of tar catalytic reforming can be divided into two main processes: (1) the catalytic cracking process, where tar was cracked into char, gases, and small molecules volatiles; (2) the catalytic reforming process, where volatiles, gases, and char were further reformed to promote the yield of gases like CO and H2 in the presence of steam. Obviously, the change in gas composition is mainly attributed to the series of reactions (eqs 5–10) involved in the catalytic reforming process. (24,25)
图 1 和 S4 分别显示了不同促进剂改性镍催化剂对 700 °C 时气体产率、气体成分（H2、CO、CO2 和 CH4）和气体质量（LHV 和 H2/CO）的影响。焦油催化重整过程可分为两个主要过程：（1）催化裂化过程，焦油裂解成焦炭、气体和小分子挥发物;（2） 催化重整过程，其中挥发物、气体和焦炭进一步重整，以提高在蒸汽存在下 CO 和 H2 等气体的产量。显然，气体成分的变化主要归因于催化重整过程中涉及的一系列反应（方程 5-10）。（24,25）
Tar cracking reaction: 焦油裂解反应：
Tar→C+CxHy+gasesΔH298K=+Q
(4)
Tar dry reforming reaction:
焦油干重整反应：
CxHy+xCO2→2xCO+(y/2)H2ΔH298K=+Q
(5)
Tar steam reforming reaction:
焦油蒸汽重整反应：
CxHy+xH2O→xCO+(x+y/2)H2ΔH298K=+Q
(6)
Methane steam reforming reaction:
甲烷蒸汽重整反应：
CH4+H2O⇌CO+3H2ΔH298K=+206.3kJ/mol
(7)
Water–gas shift reaction:
水-气变换反应：
CO+H2O⇌CO2+H2ΔH298K=−41kJ/mol
(8)
Char self-gasification reaction”
焦炭自气化反应”
C+H2O⇌CO+H2ΔH298K=+131.3kJ/mol
(9)
Boudouard reaction: 布杜阿尔反应：
C+CO2⇌2COΔH298K=+172kJ/mol
(10)
The addition of promoter (Fe, Co, or Mg) improved the gas quality in T-TMC catalytic reforming by increasing the content of H2 and CO, LHV, and H2/CO. The maximum gas yield of 1.77 N m3/ kg T-TMC and LHV of 11.53 MJ/Nm3 were attained on 6% Ni–6% Co/char with a high H2/CO of 2.63. The LHV of gas products obtained from T-TMC catalytic reforming over 6% Ni–6% Co/char was higher than that of water gas (10.38 MJ/Nm3), indicating that the gas product has a high energy utilization value to purify H2 production and synthesizing water gas. The high oxygen affinity of Co significantly improved the quality of gas products by promoting the catalytic reforming reactions (eqs 5–10), (50,51) which was consistent with the high T-TMC conversion and H2 yield of 6% Ni–6% Co/char. The effects of the reforming temperature and Co loading on T-TMC conversion into H2 were further conducted in order to obtain the optimal process parameters for hydrogen production over Co-modified nickel nanocatalysts.
添加促进剂（Fe、Co 或 Mg）通过增加 H2 和 CO、LHV 和 H2/CO 的含量，改善了 T-TMC 催化重整中的气体质量。在 1.77% Ni–6% Co/char 和 2.63 的高 H2/CO 上，实现了 11.53 NM3/kg T-TMC 的最大气体产率和 11.53 MJ/Nm3 的 LHV。T-TMC 催化重整 6% Ni–6% Co/char 以上的气体产物 LHV 高于水气 （10.38 MJ/Nm3），表明该气体产物在净化 H2 生产和合成水气方面具有很高的能源利用价值。Co 的高氧亲和力通过促进催化重整反应 （方程 5-10） （50,51） 显着提高了气体产品的质量，这与 6% Ni-6% Co/char 的高 T-TMC 转化率和 H2 产率一致。进一步研究了重整温度和 Co 负载对 T-TMC 转化为 H2 的影响，以获得通过 Co 改性镍纳米催化剂制氢的最佳工艺参数。

Effects of Catalytic Reforming Temperature and Promoter Co Loading on T-TMC Conversion into Hydrogen
催化重整温度和启动子共负载量对 T-TMC 转化为氢气的影响

The effects of catalytic reforming temperature on the conversion of T-TMC into H2 for 6% Ni–6% Co/char in the range of 500–800 °C are presented in Figure 2a. As the temperature increased from 500 to 700 °C, T-TMC conversion and H2 yield increased sharply and reached a maximum of 98.56% and 103.43 g/kg of T-TMC at 700 °C, respectively. It was worth noting that a little increase of the T-TMC conversion and decrease of the H2 yield for 6% Ni–6% Co/char were found as the temperature further increased to 800 °C. Too high temperature will not contribute to C–C and C–H bond breaking to some extent due to the sintering of active particles in the catalysts. (52) Besides, a slight decrease in H2 yield with increasing temperature was mainly because of the exothermic reaction for water–gas shift reaction (eq 6). (53)
图 2a 显示了在 500–800 °C 范围内，催化重整温度对 6% Ni–6% Co/char 将 T-TMC 转化为 H2 的影响。随着温度从 500 °C 升高到 700 °C，T-TMC 转化率和 H2 产率急剧增加，在 700 °C 时分别达到 98.56% 和 103.43 g/kg 的最高值。值得注意的是，随着温度进一步升高至 800 °C，发现 6% Ni–6% Co/char 的 T-TMC 转化率略有增加，H2 产率降低。 由于催化剂中活性颗粒的烧结，过高的温度在一定程度上不会导致 C-C 和 C-H 键断裂。（52） 此外，H2 产率随温度的升高而略有下降，主要是由于水-气变换反应的放热反应 （方程 6）。（53）

Figure 2 图 2

Figure 2. Effect of (a) catalytic reforming temperature of 6% Ni–6% Co/char and (b) promoter Co loading of the Ni–Co alloy nanocatalyst (700 °C) on T-TMC conversion and hydrogen production.
图 2.（a） 6% Ni–6% Co/char 的催化重整温度和 （b） Ni–Co 合金纳米催化剂的促进剂 Co 负载 （700 °C） 对 T-TMC 转化和制氢的影响。

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As observed in Figure S5, the vol % of H2 and CO rose sharply with the increase of temperature, while the vol % of CO2 and CH4 showed a downward trend. The tar dry reforming reaction (eq 5), tar steam reforming reaction (eq 6), and char self-gasification reaction (eq 9) were promoted at higher temperatures, resulting in the production of more H2 and CO. Simultaneously, the methane steam reforming reaction (eq 7) was enhanced, resulting in a decrease in CH4 production and a further increase in CO and H2 production. In addition, the Boudouard reaction (eq 10) and the reverse reaction of the water–gas shift reaction (eq 8) led to a decrease in CO2 production and an increase in CO production. The highest gas yield of 1.77 g/kg T-TMC and gas quality with an LHV of 11.53 MJ/Nm3 and H2/CO of 2.63 were also obtained over 6% Ni–6% Co/char at 700 °C. In consideration of the limitations of high operating costs and high-temperature sintering, 700 °C was selected as the catalytic reforming temperature of 6% Ni–x% Co/char for the following investigation.
如图 S5 所示，H2 和 CO 的体积百分比随着温度的升高而急剧上升，而 CO2 和 CH4 的体积百分比呈下降趋势。焦油干重整反应 （eq 5）、焦油蒸汽重整反应 （eq 6） 和焦炭自气化反应 （eq 9） 在较高温度下得到促进，导致产生更多的 H2 和 CO。同时，甲烷蒸汽重整反应 （eq 7） 增强，导致 CH4 产生减少，CO 和 H2 产生进一步增加。此外，布杜阿尔反应（方程 10）和水-气变换反应的逆反应（方程 8）导致 CO2 产生减少，而 CO 产生增加。在 700 °C 时，最高产气量为 1.77 g/kg T-TMC，LHV 为 11.53 MJ/Nm3，H 2/CO 为 2.63，Ni–6% Co/char 含量也超过 6%。 考虑到高运营成本和高温烧结的限制，选择 700 °C 作为 6% Ni–x% Co/char 的催化重整温度进行以下研究。
Figure 2b shows that T-TMC conversion and H2 yield increased, respectively, to 99.56% and 111.46 g/kg T-TMC at 700 °C as Co loading rose from o to 4 wt %. Meanwhile, the gas yield, LHV, and H2/CO ratio reached 1.85 g/kg T-TMC, 11.60 MJ/Nm3, and 2.63 at the Co loading of 4 wt %, respectively (Figure S6). However, T-TMC conversion and H2 yield decreased as Co loading continued to go up to 6 wt %. It might be due to higher loading of Co caused the agglomeration of active sites and the blockage of the catalyst support pores. (54) The results indicated that adding the proper loading of Co could improve the tar catalytic reforming performance of nickel-based catalyst, which was attributed to the high oxygen affinity of Co, the large specific surface area (920.61 m2/g), and the high dispersion (7.3%) of Ni nanoparticles (Table S5), and the stable Ni–Co alloy (Figure 6) of 6% Co–4% Ni/char. Thus, the optimum catalytic reforming temperature and Co loading for 6% Ni–x% Co/char were 700 °C and 4 wt % in this work, respectively.
图 2b 显示，随着 Co 负载量从 o 上升到 4 wt%，在 700 °C 时，T-TMC 转化率和 H2 产率分别提高到 99.56% 和 111.46 g/kg T-TMC。同时，在 4 wt % 的 Co 负载下，气体产率、LHV 和 H2/CO 比分别达到 1.85 g/kg T-TMC、11.60 MJ/Nm3 和 2.63（图 S6）。然而，随着 Co 负载量继续上升至 6 wt %，T-TMC 转化率和 H2 产率下降。这可能是由于 Co 负载量较高导致活性位点聚集和催化剂支撑孔堵塞。（54） 结果表明，添加适当的 Co 负载可以提高镍基催化剂的焦油催化重整性能，这归因于 Co 的高氧亲和力、大比表面积 （920.61 m2/g） 和高分散性 （7.3%） 的 Ni 纳米颗粒（表 S5）和稳定的 Ni-Co 合金（图 6） 的 6% Co–4% Ni/char。因此，在本工作中，6% Ni–x% Co/char 的最佳催化重整温度和 Co 负载分别为 700 °C 和 4 wt %。
In order to comprehensively evaluate the catalytic reforming performance for converting tar into H2, 6% Ni–4% Co/char prepared in this study was compared with other biochar-supported metal catalysts reported in the literature, and the comparison results are summarized in Table 1. It can be seen that 6% Ni–4% Co/char prepared in this work achieved the highest T-TMC conversion of 99.59% and H2 yield of 111.46 g/kg T-TMC at a relatively low temperature of 700 °C. To further analyze the potential for long-term practical applications of 6% Ni–4% Co/char, the service life of the catalyst was studied using the mixture of toluene, naphthalene, and phenol (5:2:1, w/w/w) as M-TMC. Figure 3 displays that 6% Ni–4% Co/char maintained a high M-TMC conversion of more than 85.18% and H2 yield of 242.5 g/kg M-TMC at recycling times of three. Meanwhile, the high gas quality (LHV of 10.15–10.19 MJ/Nm3 and H2/CO of 3.77–3.88) was also obtained over 6% Ni–4% Co/char (Table S4). In contrast, the catalytic activity of 6% Ni/char significantly decreased after one use, which proposed that 6% Ni/char was more prone to deactivation in comparison with 6% Ni–4% Co/char. The GC-MS analysis (Figure S7) showed that almost all of the M-TMC was converted into rich-H2 gas, and a small amount of broken M-TMC rings repolymerized to form macromolecular alkanes (4,5-dimethylnonane, 3-ethyl-3-methylheptane, etc.) with low ecological toxicity over 6% Ni–4% Co/char. (50,62) The above results indicated that 6% Ni–4% Co/char as a novel alloy nanocatalyst showed a significant advantage and great potential to convert tar in situ into high-purity H2 during coal and biomass gasification.
为了全面评价焦油转化为 H2 的催化重整性能，将本研究制备的 6% Ni–4% Co/char 与文献中报道的其他生物炭负载金属催化剂进行了比较，比较结果总结于表 1 中。可以看出，在相对较低的 700 °C 温度下，本工作制备的 6% Ni–4% Co/char 实现了最高的 T-TMC 转化率 99.59% 和 H2 产率 111.46 g/kg T-TMC。 为了进一步分析 6% Ni–4% Co/char 的长期实际应用潜力，使用甲苯、萘和苯酚的混合物 （5：2：1， w/w/w） 作为 M-TMC 研究了催化剂的使用寿命。图 3 显示，在 3 次回收时间下，6% Ni–4% Co/char 保持了超过 85.18% 的高 M-TMC 转化率和 242.5 g/kg M-TMC 的 H2 产量。同时，在 6% Ni-4% Co/char 上也获得了高气体质量（LHV 为 10.15-10.19 MJ/Nm3，H 2/CO 为 3.77-3.88）（表 S4）。相比之下，6% Ni/char 的催化活性在使用一次后显着降低，这表明与 6% Ni–4% Co/char 相比，6% Ni/char 更容易失活。GC-MS 分析（图 S7）显示，几乎所有的 M-TMC 都转化为富氢H 2 气体，少量破碎的 M-TMC 环再聚合形成大分子烷烃（4,5-二甲基壬烷、3-乙基-3-甲基庚烷等），其生态毒性低于 6% Ni-4% Co/char。（50,62） 上述结果表明，6% Ni-4% Co/char 作为一种新型合金纳米催化剂，显示出显著的优势和巨大的潜力，可以将焦油原位转化为煤和生物质气化过程中的高纯度 H2。
Table 1. Comparison of the Tar Conversion and H2 Yield of 6% Ni–4% Co/char Nanocatalyst Prepared in this Study with Other Reported Catalysts
表 1.本研究制备的 6% Ni–4% Co/char 纳米催化剂的焦油转化率和 H2 产率与其他已报道的催化剂的比较
catalysts 催化剂dosage (g) 剂量 （g）temperature (°C) 温度 （°C）conversion (%) 转化率 （%）H2 yield (g/kg) H2 产量 （g/kg）reference
NiFe2O4 OC
镍铁2O4 OC		0.285096.8381.25 (55)
Fe–Ni/CNF 铁-镍/CNF/70085.7653.58 (56)
SC@0.1Ni–Fe SC@0.1镍-铁3.060090.0725.34 (24)
Ni–Cu/ASC 镍-铜/ASC3.080093.2054.34 (57)
Ni–Fe char Ni–Fe 焦炭5.070093.0089.29 (45)
Ni-10%Co/AWSL5.0900/72.60 (48)
Fe10–Ni6/PG10.070099.5039.97 (58)
5Ni/ZSM-5a
5镍/ZSM-5安		1.030097.3039.07 (59)
BC-FeNi0.358008078.38 (60)
Co–Cu/CS 钴铜/CS2.0700/97.12 (61)
6% Ni–4% Co/char 6% 镍 - 4% 钴/碳0.570099.59111.46present 目前
a

The synergistic effects between dielectric barrier discharge (DBD) plasma and 5Ni/ZSM-5 catalyst.


a

介电势垒放电 （DBD） 等离子体和 5Ni/ZSM-5 催化剂之间的协同效应。

Figure 3 图 3

Figure 3. Effect of recycling times of (a) 6% Ni/char and (b) 6% Ni–4% Co/char on M-TMC (weight ratios of toluene:naphthalene:phenol = 5:2:1) conversion and hydrogen yield at the reforming temperature of 700 °C.
图 3.在 700 °C 的重整温度下，（a） 6% Ni/char 和 （b） 6% Ni–4% Co/char 的回收时间对 M-TMC（甲苯：萘：苯酚的重量比 = 5：2：1）转化率和氢气产率的影响。

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Anti-Carbon Deposition Deactivation of Co-Modified Nickel Catalysts
共改性镍催化剂的抗碳沉积失活

The carbon deposition on the surface of catalysts was formed through tar cracking reaction (eq 4) and the secondary polymerization of decomposition products. (63) As shown by numerous studies, carbon deposition plays an important role in nickel-based catalysts deactivation due to carbon deposition covers the active sites of catalyst and prevents the breaking of C–C and C–H bond. (64) Therefore, it is necessary to analyze the amount and types of carbon deposition on the surface of spent 6% Ni–4% Co/char through the characterizations of SEM-EDS, BET, TPO, and Raman. The fresh and spent catalysts were characterized by SEM-EDS analysis in order to ease the comparison between the morphological features of 6% Ni–4% Co/char and 6% Ni/char. The spent 6% Ni–4% Co/char catalyst exhibited similarity to the fresh catalysts after one use in Figure 4d,e, illustrating that a trace amount of carbon deposition was found and the catalytic activity was well retained. This may be due to char gasification reactions (eqs 9 and 1010) inhibiting the carbon deposition deactivation to some extent. However, when the gasification reaction rate is lower than the carbon deposition rate, the amount of carbon deposition on the surface of catalysts gradually increases. (65) For instance, the new carbon filaments (whisker carbon) covering the surface of the spent 6% Ni/char were observed in Figure 4b after one use. Moreover, the amount of deposited carbon increased gradually with the increase in the recycling times, which might be the main reason for the sharp decrease in the catalytic activity of 6% Ni/char (Figure 3a).
催化剂表面的碳沉积是通过焦油裂解反应 （eq 4） 和分解产物的二次聚合形成的。（63） 正如大量研究表明的那样，碳沉积在镍基催化剂失活中起着重要作用，因为碳沉积覆盖了催化剂的活性位点并防止 C-C 和 C-H 键断裂。（64） 因此，有必要通过 SEM-EDS、BET、TPO 和拉曼的表征来分析 6% Ni–4% Co/char 废物表面碳沉积的数量和类型。通过 SEM-EDS 分析对新鲜和废催化剂进行了表征，以简化 6% Ni–4% Co/char 和 6% Ni/char 的形态特征之间的比较。在图 4d，e 中使用一次后，用过的 6% Ni–4% Co/char 催化剂与新鲜催化剂相似，表明发现了微量的碳沉积并且催化活性得到了很好的保留。这可能是由于焦化气化反应（方程 9 和 1010）在一定程度上抑制了碳沉积失活。然而，当气化反应速率低于碳沉积速率时，催化剂表面的碳沉积量逐渐增加。（65） 例如，在使用 1 次后，图 4b 中观察到覆盖用过的 6% Ni/char 表面的新碳丝（晶须碳）。此外，随着回收时间的增加，沉积碳的数量逐渐增加，这可能是 6% Ni/char 催化活性急剧下降的主要原因（图 3a）。

Figure 4 图 4

Figure 4. SEM image and EDS pattern of (a) the fresh 6% Ni/char (N = 0); (b) the spent 6% Ni/char (N = 1); (c) the spent 6% Ni/char (N = 3); (d) the fresh 6% Ni–4% Co/char (N = 0); (e) the spent 6% Ni-4% Co/char (N = 1); (f) the spent 6% Ni–4% Co/char (N = 5). N represents the recycling times of catalysts.
图 4.（a） 新鲜的 6% Ni/char （N = 0）;（b） 用过的 6% Ni/char （N = 1）;（c） 用过的 6% Ni/char （N = 3）;（d） 新鲜的 6% Ni–4% Co/char （N = 0）;（e） 用过的 6% Ni-4% Co/char （N = 1）;（f） 用过的 6% Ni–4% Co/char （N = 5）。N 表示催化剂的回收时间。

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As can be seen from the EDS map scanning in Figure 4c,f, the amount of carbon deposition of the spent 6% Ni–4% Co/char and the spent 6% Ni/char were about 9.4 and 14.5 wt % after five- and three-time reuse, respectively, roughly calculated based on the content of carbon element in the fresh and spent catalysts. As shown in Table 2 and Figure S8, the reduction in the BET surface area of the spent 6% Ni/char was 3.5 times that of the spent 6% Ni–4% Co/char after one use, which was mainly ascribed to some pores of 6% Ni/char being blocked by more carbon deposition. The analysis results of carbon deposition by BET and SEM demonstrated that 6% Ni–4% Co/char exhibited an excellent ability to suppress carbon deposition.
从图 4c、f 中的 EDS 图扫描中可以看出，根据新鲜和废催化剂中碳元素的含量粗略计算，6% Ni-4% Co/char 和 6% Ni/char 的废碳沉积量分别约为 9.4 和 14.5 wt %。如表 2 和图 S8 所示，使用一次后，用过的 6% Ni/char 的 BET 表面积减少是用过的 6% Ni–4% Co/char 的 3.5 倍，这主要是由于 6% Ni/char 的一些孔被更多的碳沉积堵塞。BET 和 SEM 的碳沉积分析结果表明，6% Ni–4% Co/char 表现出优异的抑制碳沉积能力。
Table 2. Textural Properties of the Fresh and Spent Catalysts
表 2.新鲜和废催化剂的质构特性
samples 样品recycling times 回收时间BET surface area (m2/g)
BET 表面积 （m2/g）		total pore volume (cm3/g)
总孔体积 （cm3/g）		average pore diameter (nm)
6% Ni/char 6% 镍/碳0853.290.4672.218
1577.360.3872.645
3189.300.1396.406
6% Ni–4% Co/char 6% 镍 - 4% 钴/碳0920.610.2692.180
1840.090.2563.166
5227.170.1575.723
The quantity and composition of carbon deposited on the spent nanocatalysts were further measured by TPO. The carbon deposition of the spent catalysts was equal to the difference in weight loss between the spent catalysts and fresh catalysts. (66,67) The previous studies have shown that thermal decomposition mass loss of spent catalysts at temperatures between 400 and 600 °C and between 600 and 800 °C in TG and DTG curves represent amorphous carbon and graphitic carbon deposition, respectively. (25,68) Notably, graphitic carbon is more prone to cause the catalyst deactivation than amorphous carbon because the former was difficult to be consumed by char gasifacation reactions (eqs 9–10). (44,69) As observed in Figure 5c,d, the weight loss rate for the spent 6% Ni–4% Co/char at 400–800 °C was identified as 2.07 wt % of amorphous carbon after one use, as well as 1.18 wt % of graphitic carbon and 6.91 wt % of amorphous carbon occurred after five times reuse. By contrary, 1.50 wt % of graphitic carbon and 2.48 wt % of amorphous carbon were formed over the spent 6% Ni/char after one use according to Figure 5a,b. Moreover, the amount of graphite whisker carbon deposition reached 15.66% after three times reuse, which proved that the amorphous carbon deposited on the surface of the catalyst gradually transformed into graphitic carbon as recycling times increased.
通过 TPO 进一步测量沉积在废纳米催化剂上的碳的数量和成分。废催化剂的碳沉积等于废催化剂和新鲜催化剂之间的重量损失差。（66,67） 以前的研究表明，在 TG 和 DTG 曲线中，在 400 至 600 °C 和 600 至 800 °C 之间，废催化剂的热分解质量损失分别代表无定形碳和石墨碳沉积。（25,68） 值得注意的是，石墨碳比无定形碳更容易导致催化剂失活，因为前者很难被焦化气化反应消耗（方程 9-10）。（44,69） 如图 5c，d 所示，在 400-800 °C 下，用过的 6% Ni-4% Co/char 的重量损失率被确定为一次使用后 2.07 wt % 的无定形碳，以及 1.18 wt % 的石墨碳和 6.91 wt% 的无定形碳在五次再利用后发生。相反，根据图 5a，b，使用一次后，在用过的 6% Ni/char 上形成了 1.50 wt % 的石墨碳和 2.48 wt % 的无定形碳。此外，石墨晶须碳沉积量经过 3 次再利用后达到 15.66%，证明沉积在催化剂表面的无定形碳随着回收次数的增加逐渐转变为石墨碳。

Figure 5 图 5

Figure 5. TG-DTG curves and Raman spectra of the corresponding fresh and spent catalysts. TG-DTG curves of (a,b) 6% Ni/char and (c,d) 6% Ni–4% Co/char; Raman spectra of (e) 6% Ni/char and (f) 6% Ni–4% Co/char.
图 5.相应的新鲜和废催化剂的 TG-DTG 曲线和拉曼光谱。（a，b） 6% Ni/char 和 （c，d） 6% Ni–4% Co/char 的 TG-DTG 曲线;（e） 6% Ni/char 和 （f） 6% Ni–4% Co/char 的拉曼光谱。

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To visually display the type of carbon deposition, the fresh and spent catalysts were characterized by Raman spectroscopy. The D and G bands in Raman spectroscopy of the spent catalyst represented the presence of amorphous carbon deposition and graphitic carbon deposition, respectively. (70) According to the Tuinstra and Koening (TK) law, the integrated ratio of the D and G bands (ID/IG) varies inversely with the graphite crystallinity of carbon deposition. (64) The low graphite crystallinity was observed for the spent 6% Ni–4% Co/char (ID/IG = 1.20) after five-time reuse compared to that of the spent 6% Ni/char (ID/IG = 1.01) after three-time reuse in Figure 5e,f. Clearly, 6% Ni/char was prone to deactivation because of the serious graphitic whisker carbon deposition, while 6% Ni–4% Co/char proposed higher resistance to carbon deposition by promoting char gasification reaction (eqs 9 and 10) and suppressing the growth of graphitic whisker carbon. (71)
为了直观地显示碳沉积的类型，通过拉曼光谱对新鲜和废催化剂进行了表征。废催化剂拉曼光谱中的 D 和 G 波段分别表示无定形碳沉积和石墨碳沉积的存在。（70） 根据 Tuinstra 和 Koening （TK） 定律，D 和 G 带的积分比 （ID/IG） 与碳沉积的石墨结晶度成反比。（64） 在图 5e，f 中，与三次再利用后的 6% Ni/char （I D/I G = 1.20） 相比，在 5 次重复使用后观察到 6% Ni-4% Co/char （ID/IG = 1.20） 的低石墨结晶度。显然，由于严重的石墨晶须碳沉积，6% Ni/char 容易失活，而 6% Ni–4% Co/char 通过促进炭气化反应（方程 9 和 10）和抑制石墨晶须碳的生长，提出了更高的碳沉积抵抗力。（71）
As can be seen from the above characterization results, 6% Ni–4% Co/char exhibited an excellent ability to suppress carbon deposition in comparison with 6% Ni/char. On the one hand, Co has a high affinity for oxygen-containing species (CO2 and H2O), suppressing the carbon deposition of 6% Ni–4% Co/char through promoting char self-gasification reaction (eq 9) and Boudouard reaction (eq 10). On the other hand, the addition of Co was conductive to suppress carbon deposition by reducing Ni nanoparticle size (13.3 nm) since the nucleation of carbon whiskers was retarded by the smaller nickel nanoparticles. (51) The importance of the size of Ni particles on the nucleation of carbon has been confirmed by thermogravimetric experiments and in situ investigations by high-resolution transmission electron microscopy (TEM). (72,73) In addition, some research demonstrated that the formation of Ni–Co alloy can also reduce carbon deposition. (47,50) In a word, 6% Ni–4% Co/char exhibited excellent resistance to carbon deposition by removing the nucleation sites for graphite formation, forming a stable Ni–Co alloy and promoting the char gasification reaction (eqs 9 and 10).
从上述表征结果可以看出，与 6% Ni/char 相比，6% Ni–4% Co/char 表现出优异的抑制积碳能力。一方面，Co 对含氧物质（CO2 和 H2O）具有高亲和力，通过促进焦自气化反应（方程 9）和布杜阿尔反应（方程 10）抑制 6% Ni–4% Co/char 的碳沉积。另一方面，Co 的添加有助于通过减小 Ni 纳米颗粒的尺寸 （13.3 nm） 来抑制碳沉积，因为较小的镍纳米颗粒会延缓碳晶须的成核。（51） Ni 颗粒的大小对碳成核的重要性已通过热重实验和高分辨率透射电子显微镜 （TEM） 的原位研究得到证实。（72,73） 此外，一些研究表明，Ni-Co 合金的形成也可以减少碳沉积。（47,50） 总之，6% Ni–4% Co/char 通过去除石墨形成的成核位点、形成稳定的 Ni-Co 合金并促进焦化气化反应（方程 9 和 10），表现出优异的抗碳沉积能力。

Anti-oxidation and Anti-sintering Deactivation of Co-Modified Nickel Catalysts
共改性镍催化剂的抗氧化和抗烧结失活

The final deactivation processes that must be considered were oxidation and sintering of the metal particles in the nickel-based catalyst. (74) As shown in Figure 6a,b, the new peaks of carbon at 2θ = 15°∼20°, 26.23° observed on the spent catalysts were significantly different from the specific diffraction peaks of carbon (2θ = 29.49 and 44.29°) on the char (Figure 1c), which further proved the formation of carbon deposition. Besides, the diffraction peaks at 2θ = 37.25°, 43.28°, 62.86° of the spent 6% Ni/char were ascribed to crystalline phases of NiO corresponding to planes (111), (200), and (220), respectively. Regarding the spent 6% Ni–4% Co/char, the diffraction peaks were indistinctly attributed to NiO and CoO, since the similar diffraction angles of NiO and CoO hindered their separate identification. In addition, the thermal decomposition mass loss of the catalysts in Figure 5a,c at 200–400 °C was attributed to the oxidation of Ni or Co. (25) However, 6% Ni–4% Co/char still maintained higher catalytic activity after three times reuse, which revealed that most of the oxidized metal particles were determined as promoter Co instead of Ni. Moreover, the XPS analysis has confirmed that the oxidation deactivation of 6% Ni–4% Co/char was preferably oxidation of Co species compared to Ni species due to the high oxygen affinity of Co (Figure 6e,f). The active metals Ni and Co were mainly oxidated by the oxygen derived from the dissociative adsorption of the water in the steam required during tar catalytic reforming. (43,75) Moreover, the oxidation degree strengthened with the increase in the recycling times of the catalysts, as present in Figure 6a,b.
必须考虑的最终失活过程是镍基催化剂中金属颗粒的氧化和烧结。（74） 如图 6a、b 所示，在废催化剂上观察到的碳在 2θ = 15°∼20°、26.23° 处的新峰与碳在炭上的比重衍射峰（2θ = 29.49 和 44.29°）显著不同（图 1c），这进一步证明了碳沉积的形成。此外，用过的 6% Ni/char 在 2θ = 37.25°、43.28°、62.86° 处的衍射峰分别归因于对应于晶面 （111）、（200） 和 （220） 的 NiO 晶相。对于消耗的 6% Ni–4% Co/char，衍射峰模糊不清地归因于 NiO 和 CoO，因为 NiO 和 CoO 的相似衍射角阻碍了它们的单独鉴定。此外，图 5a，c 中催化剂在 200–400 °C 下的热分解质量损失归因于 Ni 或 Co 的氧化。（25） 然而，6% Ni–4% Co/char 在三次重复使用后仍保持较高的催化活性，这表明大多数氧化金属颗粒被确定为促进剂 Co 而不是 Ni。此外，XPS 分析证实，由于 Co 的高氧亲和力，与 Ni 物种相比，6% Ni–4% Co/char 的氧化失活优于 Co 物种的氧化（图 6e，f）。活性金属 Ni 和 Co 主要被焦油催化重整过程中所需的蒸汽中水解离吸附产生的氧氧化。（43,75） 此外，氧化程度随着催化剂回收时间的增加而增强，如图 6a、b 所示。

Figure 6 图 6

Figure 6. XRD patterns and XPS survey spectra of the fresh and spent catalysts. XRD patterns of (a) 6% Ni/char and (b) 6% Ni–4% Co/char; XPS survey spectra of (c) high-resolution scans, (d) C 1s regions, (e) Ni 2p regions, and (f) Co 2p regions of 6% Ni–4% Co/char.
图 6.新鲜和废催化剂的 XRD 图谱和 XPS 测量光谱。（a） 6% Ni/char 和 （b） 6% Ni–4% Co/char 的 XRD 图谱;（c） 高分辨率扫描、（d） C 1s 区域、（e） Ni 2p 区域和 （f） 6% Ni–4% Co/char 的 Co 2p 区域的 XPS 测量光谱。

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The pattern of fresh 6% Ni/char presents the main diffraction at 2θ = 44.50, which is marked as the (111) of Ni. With regard to the fresh 6% Ni–4% Co/char, the typical diffraction peak of Ni–Co was evident at 2θ = 44.40°. The typical diffraction peak of Ni–Co slightly shifted toward (111) of Co (2θ = 44.10°) due to the formation of Ni–Co alloy and the Ni lattice with a small amount of doped Co, which was consistent with previous reports. (76,77) In addition, the main diffraction peaks of 2θ = 44.40°, 51.85°, and 76.38° belonging to the Ni–Co alloy nanoparticles were still obtained on the spent catalysts. Based on the XRD results, the crystallite size and dispersion of Ni were calculated and summarized in Table S5 so as to evaluate the irreversible deactivation by metal sintering. The Ni particle dispersion of the spent 6% Ni–4% Co/char after five cycles (3.9%) was similar to that of the spent 6% Ni/char after one use (3.4%). The results illustrated that the intimate interaction between Ni and Co based on the formation of the Ni–Co alloy improved the Ni nanoparticle dispersion and suppressed aggregation sintering. It has also been reported that the similarity in the atom radius of Ni and Co was beneficial to the formation of Ni–Co alloy and their intimate interaction played an important role in suppressing catalyst sintering deactivation. (50)
新鲜的 6% Ni/char 图案在 2θ = 44.50 处呈现主衍射，标记为 Ni 的 （111）。对于新鲜的 6% Ni–4% Co/char，Ni–Co 的典型衍射峰在 2θ = 44.40° 处很明显。由于形成 Ni-Co 合金和含有少量掺杂 Co 的 Ni 晶格，Ni-Co 的典型衍射峰略微向 Co 的 （111） 移动 （2θ = 44.10°），这与以前的报道一致。（76,77） 此外，属于 Ni-Co 合金纳米颗粒的主要衍射峰 2θ = 44.40°、51.85° 和 76.38° 仍然在废催化剂上获得。根据 XRD 结果，计算了 Ni 的晶粒尺寸和分散性，并将其汇总在表 S5 中，以评估金属烧结的不可逆失活。5 次循环后 6% Ni–4% Co/char 的 Ni 颗粒分散性 （3.9%） 与使用 1 次后 6% Ni/char 的 Ni 颗粒分散性 （3.4%） 相似。结果表明，基于 Ni-Co 合金形成的 Ni 和 Co 之间的密切相互作用改善了 Ni 纳米颗粒的分散性并抑制了聚集烧结。据报道，Ni 和 Co 原子半径的相似性有利于 Ni-Co 合金的形成，它们的密切相互作用在抑制催化剂烧结失活方面起了重要作用。（50）
As presented in Figure 6c, Ni, Co, O, C, and K were the major components of the 6% Ni–4% Co/char, which can also be proven by the results of SEM-EDS. In addition, in order to clearly present the XPS results of Figure 6c, the local enlarged images of the XPS peaks of Ni 2p and Co 2p of 6% Ni–4% Co/char are provided in Figure S9. As recycling times increased, the carbon peak on the spent catalyst strengthened, while the peaks of other species weakened. The results indicated that the carbon deposition on the catalyst covered other species and led them not being detected due to the XPS analysis depth being less than 2 nm. The increase of carbon deposition on the surface of the catalyst can also be observed in Figure 6d. Charging effects were corrected by regulating the binding energy (BE) of C 1s to 284.6 eV. (78) In the C 1s spectrum, the carbon atoms of 6% Ni–4% Co/char mainly existed in the shape of sp2 hybridized graphitized carbon, which was favorable for improving the catalytic activity of catalyst. (79) Gai et al. and Ren et al. both found that the modified char-supported catalysts exhibited higher catalytic activity due to the outstanding graphitized and layered delocalized structures. (46,80)
如图 6c 所示，Ni、Co、O、C 和 K 是 6% Ni–4% Co/char 的主要成分，这也可以被 SEM-EDS 的结果证明。此外，为了清晰地呈现图 6c 的 XPS 结果，图 S9 提供了 6% Ni–4% Co/char 的 Ni 2p 和 Co 2p XPS 峰的局部放大图像。随着回收时间的增加，废催化剂的碳峰值增强，而其他物种的碳峰值减弱。结果表明，催化剂上的碳沉积覆盖了其他物种，由于 XPS 分析深度小于 2 nm，导致它们未被检测到。在图 6d 中也可以观察到催化剂表面碳沉积的增加。通过将 C 1s 的结合能 （BE） 调节到 284.6 eV 来校正充电效应。（78） 在 C 1s 光谱中，6% Ni–4% Co/char 的碳原子主要以 sp2 杂化石墨化碳的形式存在，有利于提高催化剂的催化活性。（79） Gai 等人和 任 等人都发现，由于出色的石墨化和层状离域结构，改性的焦负载催化剂表现出更高的催化活性。（46,80）
In the Ni 2p spectrum (Figure 6e), the peak in fresh 6% Ni–4% Co/char at 852.6 and 869.9 eV were ascribed to Ni0, (81) which showed that the metallic Ni mainly existed in the shape of Ni0. The new peaks for Ni2+ at 862.3 eV were observed on the spent 6% Ni–4% Co/char (N = 1) because of a small amount of Ni being oxidized to NiO, which corresponded to the result of XRD. (81) For the Co 2p spectrum (Figure 6f), the peaks at 778.0 and 794.2 eV were attributed to Co. (81) The −0.1 eV of Ni0(870 eV) and +0.2 eV of Co0(794.0 eV) shift corresponds to the strengthened interaction between Ni and Co due to the formation of Ni–Co alloy, which is ascribed to the difference of the electron work function between Ni and Co. (82,83) The electrons may transfer from Co to Ni, leading to the shifts of the binding energies in the Ni–Co alloy because of a lower electron work function. The electronic conditions of Ni and Co atoms were changed and their electronic properties were improved. (84) In addition, the peaks of Co at 786.4 and 802.5 eV can be ascribed to Co2+, indicating that metallic Co was easy to be oxidized instead of Ni. (85,86) The oxidation deactivation of 6% Ni–4% Co/char nanocatalyst was preferable to the oxidation of metallic Co species rather than Ni species because of the high oxygen affinity of Co, as reported by other studies. (50,51) The strengthened interaction between Ni and Co in the Ni–Co alloy, high dispersion of Ni nanoparticles, and high oxygen affinity of Co were beneficial to suppress agglomeration sintering and oxidation deactivation of active particles Ni loading on 6% Ni–4% Co/char.
在 Ni 2p 光谱中（图 6e），新鲜的 6% Ni–4% Co/char 在 852.6 和 869.9 eV 处的峰值归因于 Ni0，（81），这表明金属 Ni 主要以 Ni0 的形状存在。由于少量 Ni 被氧化成 NiO，因此在用过的 6%Ni–4% Co/char （N = 1） 上观察到 Ni2+ 在 862.3 eV 处的新峰，这与 XRD 的结果相对应。（81） 对于 Co 2p 光谱（图 6f），778.0 和 794.2 eV 处的峰归因于 Co。（81） Ni0（870 eV） 的 −0.1 eV 和 Co0（794.0 eV） 的 +0.2 eV 偏移对应于由于 Ni-Co 合金的形成而加强的 Ni 和 Co 之间的相互作用，这归因于 Ni 和 Co 之间的电子功函数的差异。电子可以从 Co 转移到 Ni，由于电子功函数较低，导致 Ni-Co 合金中的结合能发生变化。Ni 和 Co 原子的电子条件发生了变化，它们的电子性质得到了改善。（84） 此外，Co 在 786.4 和 802.5 eV 的峰可归因于 Co2+，表明金属 Co 而不是 Ni 容易被氧化。（85,86） 正如其他研究报道的那样，6% Ni-4% Co/char 纳米催化剂的氧化失活优于金属 Co 物种而不是 Ni 物种的氧化，因为 Co 具有高氧亲和力。（50,51） Ni-Co 合金中 Ni 和 Co 之间的相互作用增强、Ni 纳米颗粒的高分散性和 Co 的高氧亲和力有利于抑制活性颗粒在 6% Ni–4% Co/char 负载下的团聚烧结和氧化失活。

Antideactivation Mechanisms of Co-Modified Nickel Catalysts
共改性镍催化剂的抗失活机制

Based on the above discussion, the nickel-based catalyst deactivation was mainly caused by carbon deposition, Ni crystallite sintering, and oxidation. The 6% Ni/char was quickly deactivated by the graphitic whisker carbon deposition covering the active sites, blocking the pore openings, and preventing the access of tar-model molecules to the active sites, because graphitic carbon was difficult to be consumed by char gasification reaction (eqs 9 and 10). However, 6% Ni–4% Co/char can suppress carbon deposition by removing the nucleation sites for graphite formation since the nucleation of graphitic whisker carbon was retarded by the smaller nickel nanoparticles and promoting the water–gas shift reaction (eq 8), char self-gasification reaction (eq 9), and Boudouard reaction (eq 10), since promoter Co has a high affinity for oxygen-containing species (CO2 and H2O). As for the oxidation deactivation of 6% Ni/char, the active metal Ni was mainly oxidized by oxygen derived from the dissociative adsorption of water in the steam required during tar catalytic reforming. Surprisingly, the promoter Co in 6% Ni-4% Co/char was easily oxidized instead of Ni due to the higher oxygen affinity of Co. Additionally, the oxidized nickel (Ni2+) can be reactivated in situ by reducing gas products (i.e., H2 and CO), which was attributed to H2 production. Obviously, Ni crystallite sintering was another key factor leading to the 6% Ni/char catalyst deactivation through a loss of total active sites owing to Ni nanoparticle growth and aggregation at high temperature during tar catalytic reforming. Interestingly, 6% Ni–4% Co/char inhibited the Ni sintering by the strengthened interaction between Ni and Co particles of Ni–Co alloy, high specific surface area (920.61 m2/g), and high dispersion (7.3%) of Ni nanoparticles at the same temperature.
基于以上讨论，镍基催化剂失活主要由积碳、镍微晶烧结和氧化引起。6% Ni/char 被覆盖在活性位点的石墨晶须碳沉积迅速失活，堵塞了孔隙，并阻止了焦油模型分子进入活性位点，因为石墨碳很难被焦炭气化反应消耗（方程 9 和 10）。然而，6% Ni–4% Co/char 可以通过去除石墨形成的成核位点来抑制碳沉积，因为石墨晶须碳的成核被较小的镍纳米颗粒延迟，并促进水-气变换反应（方程 8）、焦自气化反应（方程 9）和 Boudouard 反应（方程 10），因为启动子 Co 对含氧物质（CO2 和 H2 ）具有高亲和力对于6% Ni/char的氧化失活，活性金属Ni主要被焦油催化重整过程中所需的蒸汽中水的解离吸附得到的氧氧化。令人惊讶的是，由于 Co 具有较高的氧亲和力，6% Ni-4% Co/char 中的促进剂 Co 很容易被氧化而不是 Ni。此外，氧化的镍 （Ni2+） 可以通过还原气体产物（即 H2 和 CO）在原位重新活化，这归因于 H2 的产生。显然，Ni 微晶烧结是导致 6% Ni/char 催化剂失活的另一个关键因素，因为在焦油催化重整过程中，由于 Ni 纳米颗粒在高温下生长和聚集而失去了总活性位点。 有趣的是，在相同温度下，6% Ni–4% Co/char 通过 Ni-Co 合金的 Ni 和 Co 颗粒之间的相互作用增强、高比表面积 （920.61 m2/g） 和高分散性 （7.3%） 抑制了 Ni 烧结。

Environmental Implications
环境影响

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Tar, generated as the hazardous byproduct, poses a serious threat to environmental equipment, human health, and the ecological environment. In this work, a novel alloy nanocatalyst was first synthesized for converting tar into H2 with a more than 30% increase in hydrogen yield (263.84 g H2/kg M-TMC) compared to traditional catalysts during catalytic reforming. The antideactivation mechanisms of the nanocatalyst were studied in depth and found that the alloy nanocatalyst exhibited excellent resistance to carbon deposition deactivation by removing the nucleation sites for graphite formation, resistance to oxidation deactivation due to high oxygen affinity of Co, as well as resistance to aggregation sintering deactivation by strengthened interaction between Ni and Co in the Ni–Co alloy. Through the utilization of the catalytic reforming process with the innovative nanocatalyst in this work, irrespective of process energy losses, an estimated 7.0 million tons of H2 can be generated from coal tar based on China’s coal tar production of 26.5 million tons in 2021, which enables the electricity generation of 1.4 × 1011 kW·h, equivalent to reducing the consumption of 17.2 million tons of standard coal (based on the calculation of 20 kW·h/1 kg H2 and 0.123 kg standard coal/1 kW·h). This work offered reliable strategies for the in situ conversion of tar into H2 during coal or biomass gasification in application and further fostering sustainable recycling for the production of clean energy.
焦油是有害的副产品，对环境设备、人类健康和生态环境构成严重威胁。在本工作中，首次合成了一种新型合金纳米催化剂，用于将焦油转化为 H2，在催化重整过程中，氢气产率比传统催化剂提高了 30% 以上 （263.84 g H2/kg M-TMC）。深入研究了纳米催化剂的抗脱活机理，发现合金纳米催化剂通过去除石墨形成的成核位点表现出优异的抗碳沉积失活能力，由于 Co 的高氧亲和力而表现出优异的抗氧化性，以及通过加强 Ni-Co 合金中 Ni 和 Co 之间的相互作用而表现出对聚集烧结失活的抵抗力。通过在这项工作中使用带有创新纳米催化剂的催化重整工艺，无论工艺能量损失如何，根据中国 2021 年煤焦油产量 2650 万吨，估计煤焦油可产生 700 万吨 H2，发电量为 1.4 × 1011 kW·h， 相当于减少 1720 万吨标准煤的消耗量（基于 20 kW·h/1 kg H2 和 0.123 kg 标准煤/1 kW·h 的计算）。这项工作为在煤或生物质气化过程中将焦油原位转化为 H2 提供了可靠的策略，并进一步促进了清洁能源生产的可持续回收。

Supporting Information 支持信息

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The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acs.est.3c08857.
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  • Additional experimental details, characterization, catalytic activity, stability results, computational methods, and additional data (PDF)
    其他实验细节、表征、催化活性、稳定性结果、计算方法和其他数据 （PDF）

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Author Information 作者信息

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  • Corresponding Authors 通讯作者
    • Junrong Yue - State Key Laboratory of Multi-Phase Complex System, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190, China;  Email: jryue@ipe.ac.cn
      岳俊荣 - 中国科学院过程工程研究所， 多相复杂系统国家重点实验室， 北京 100190; 电子邮件：jryue@ipe.ac.cn
    • Jun Zhang - State Key Laboratory of Urban Water Resource and Environment, National Engineering Research Center for Safe Disposal and Resources Recovery of Sludge, School of Environment, Harbin Institute of Technology, Harbin 150090, China;  Orcidhttps://orcid.org/0000-0002-5683-777X;  Email: hitsunyboy@126.com
      张军 - 哈尔滨工业大学环境学院，城市水资源与环境国家重点实验室，污泥安全处置与资源化国家工程研究中心，黑龙江 哈尔滨 150090; Orcid https://orcid.org/0000-0002-5683-777X;  电子邮件： hitsunyboy@126.com
  • Authors 作者
    • Junjie Chen - State Key Laboratory of Urban Water Resource and Environment, National Engineering Research Center for Safe Disposal and Resources Recovery of Sludge, School of Environment, Harbin Institute of Technology, Harbin 150090, China
      陈俊杰 - 哈尔滨工业大学环境学院，城市水资源与环境国家重点实验室，污泥安全处置与资源化国家工程研究中心，哈尔滨 150090
    • Yongxiao Liu - State Key Laboratory of Urban Water Resource and Environment, National Engineering Research Center for Safe Disposal and Resources Recovery of Sludge, School of Environment, Harbin Institute of Technology, Harbin 150090, China
    • Zhengrui Chen - State Key Laboratory of Urban Water Resource and Environment, National Engineering Research Center for Safe Disposal and Resources Recovery of Sludge, School of Environment, Harbin Institute of Technology, Harbin 150090, China
    • Yu Tian - State Key Laboratory of Urban Water Resource and Environment, National Engineering Research Center for Safe Disposal and Resources Recovery of Sludge, School of Environment, Harbin Institute of Technology, Harbin 150090, China
    • Chengzhi Zheng - Guangdong Yuehai Water Investment Co., Ltd, Shenzhen 518021, China
  • Notes
    The authors declare no competing financial interest.

Acknowledgments

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This study was supported by the National Key R&D Program of China (2022YFC3801101), the National Natural Science Foundation of China (52170028), and the NERC-UWR R&D Program (GJS-YF-LX202207280015). The authors also appreciate the State Key Laboratory of Urban Water Resource and Environment, Harbin Institute of Technology (2023DX11), and the Joint Engineering Research Center of Biomass Energy Development and Utilization (2021B005).

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    Energy recovery via waste utilization in gasification process is an attractive alternative energy source which is expected to supersede part of the energy from fossil fuels. To enhance the H2-rich syngas prodn. from residual biomass mixed with polymeric waste, a dual stage process involving catalytic steam gasification and tar cracking was integrated as a promising alternative technol. for clean fuel prodn. Generally, the presence of tar causes syngas degrdn. and has been identified as one of the major impurities from the gasification process. This study shows the results obtained from an integrated process with optimization process conditions to enhance H2-rich syngas yield. Nickel and dolomite were used as cheap and effective catalysts in fluidized and fixed bed gasifiers resp., which resulted in high-quality syngas prodn. with a max. hydrogen yield of 284.1 gH2 kg-1feedstock and carbon conversion efficiency (CCE) of 92.4 wt%. Furthermore, the study eventuates the upgrading of the bio-char to carbon nano-tubes (CNT). In fact CNT could be further employed either in gasification process or as electrocatalyst supporting materials for low-temp. fuel cells.
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  6. 6
    Wang, Y.; Huang, L.; Zhang, T.; Wang, Q. Hydrogen-rich syngas production from biomass pyrolysis and catalytic reforming using biochar-based catalysts. Fuel 2022, 313, 123006,  DOI: 10.1016/j.fuel.2021.123006
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    Hydrogen-rich syngas production from biomass pyrolysis and catalytic reforming using biochar-based catalysts
    Wang, Yanjie; Huang, Liang; Zhang, Tianyu; Wang, Qiang
    Fuel (2022), 313 (), 123006CODEN: FUELAC; ISSN:0016-2361. (Elsevier Ltd.)
    A residual biochar-based catalyst has been studied for in-line catalytic reforming process after biomass pyrolysis. Poplar pyrolytic char and Ni/char with different Ni loading were prepd. and used as catalysts for producing hydrogen-rich syngas from poplar wood. XRD, BET, SEM, and TEM anal. were used to characterize the synthesized catalysts. The results show that biochar has abundant pore structure and catalytic activity, which is in favor of bio-oil reforming. When loaded with Ni, biochar can also be used as a support, which directly reduces NiO to active Ni and protects Ni from oxidn. Ni/Char catalyst showed better catalytic activity than biochar. A series of expts. have been performed to det. the optimal operating conditions, such as catalytic temp. and water injection flow rate. The expt. results indicated that the best syngas prodn. of 34.321 mmol per 1 g biomass can be achieved with 10 wt% Ni/Char catalyst at 650°C. When 0.3 mL/min of water was added to the pyrolysis reactor, syngas prodn. was significantly increased to 109.848 mmol per 1 g biomass, owing to the thorough utilization of biol. carbon through reaction with water vapor. Therefore, this study points to innovative and effective approaches to make full use of biomass and biomass residues.
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  7. 7
    Dai, H.; Dai, H. Green hydrogen production based on the co-combustion of wood biomass and porous media. Appl. Energy 2022, 324, 119779,  DOI: 10.1016/j.apenergy.2022.119779
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    Show, K. Y.; Lee, D. J.; Chang, J. S. Bioreactor and process design for biohydrogen production. Bioresources Technol. 2011, 102 (18), 8524– 8533,  DOI: 10.1016/j.biortech.2011.04.055
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    Bioreactor and process design for biohydrogen production
    Show, Kuan-Yeow; Lee, Duu-Jong; Chang, Jo-Shu
    Bioresource Technology (2011), 102 (18), 8524-8533CODEN: BIRTEB; ISSN:0960-8524. (Elsevier Ltd.)
    A review of advances in bioreactor and bioprocess design for biohydrogen prodn. The state-of-the art of biohydrogen prodn. is discussed emphasizing on prodn. pathways, factors affecting biohydrogen prodn., as well as bioreactor configuration and operation. While biohydrogen prodn. is still in the early stage of development, there have been a variety of lab.- and pilot-scale systems developed with promising potential. Challenges and prospects of biohydrogen prodn. are also outlined.
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  9. 9
    Srivastava, N.; Srivastava, M.; Malhotra, B. D.; Gupta, V. K.; Ramteke, P. W.; Silva, R. N.; Shukla, P.; Dubey, K. K.; Mishra, P. K. Nanoengineered cellulosic biohydrogen production via dark fermentation: A novel approach. Biotechnol. Adv. 2019, 37 (6), 107384,  DOI: 10.1016/j.biotechadv.2019.04.006
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    Nanoengineered cellulosic biohydrogen production via dark fermentation: A novel approach
    Srivastava, Neha; Srivastava, Manish; Malhotra, Bansi D.; Gupta, Vijai K.; Ramteke, P. W.; Silva, Roberto N.; Shukla, Pratyoosh; Dubey, Kashyap Kumar; Mishra, P. K.
    Biotechnology Advances (2019), 37 (6), 107384CODEN: BIADDD; ISSN:0734-9750. (Elsevier)
    A review. The insights of nanotechnol. for cellulosic biohydrogen prodn. through dark fermn. are reviewed. In this context, impacts of nanomaterial on lignocellulosic biomass to biohydrogen prodn. process have been reviewed. Numerous aspects such as possible replacement of chem. pretreatment method using nanostructured materials, use of immobilized enzyme for a fast rate of reaction and its reusability along with long viability of microbial cells and hydrogenase enzyme for improving productivity are highlights of this review. It is found that various types of nanostructured materials e.g. metallic nanoparticles (Fe°, Ni, Cu, Au, Pd, Au), metal oxide nanoparticles (Fe2O3, F3O4, NiCo2O4, CuO, NiO, CoO, ZnO), nanocomposites (Si@CoFe2O4, Fe3O4/alginate) and graphene-based nanomaterials can influence different parameters of process and therefore may perhaps be utilized for cellulosic biohydrogen prodn.. emphasis has been given on cost issue and synthesis sustainability of nanomaterials for making biohydrogen technol. cost effective. Finally, recent advancements and feasibility of nanomaterials as potential soln. for improved cellulose conversion to biohydrogen prodn. process have been discussed, and this is likely to assist in developing an efficient, economical and sustainable biohydrogen prodn. technol.
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    Dauptain, K.; Schneider, A.; Noguer, M.; Fontanille, P.; Escudié, R.; Carrere, H.; Trably, E. Impact of microbial inoculum storage on dark fermentative H2 production. Bioresources Technol. 2021, 319 (124234), 0960– 8524,  DOI: 10.1016/j.biortech.2020.124234
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    Fagbohungbe, M. O.; Komolafe, A. O.; Okere, U. V. Renewable hydrogen anaerobic fermentation technology: Problems and potentials. Renewable Sustainable Energy Rev. 2019, 114 (109340), 1364– 0321,  DOI: 10.1016/j.rser.2019.109340
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    Xia, D.; Yan, X.; Su, X.; Zhao, W. Analysis of the three-phase state in biological hydrogen production from coal. Int. J. Hydrogen. Energy 2020, 45 (41), 21112– 21122,  DOI: 10.1016/j.ijhydene.2020.05.139
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    Analysis of the three-phase state in biological hydrogen production from coal
    Xia, Daping; Yan, Xiatong; Su, Xianbo; Zhao, Weizhong
    International Journal of Hydrogen Energy (2020), 45 (41), 21112-21122CODEN: IJHEDX; ISSN:0360-3199. (Elsevier Ltd.)
    The prodn. of biohydrogen from coal is a new research direction in the bioengineering of coalbed methane. To study the transformation process and mechanism of the gas-liq.-solid tripe phase in biohydrogen prodn. from coal, a biohydrogen prodn. expt. from low-rank coal is carried out under lab. conditions. The results show that: The daily gas prodn. of H reaches a peak value of 1.23 mL/g on the 5th day. The cumulative H prodn. is 6.24 mL/g. The pH of the liq. products gradually decreases to 5, and the Eh gradually increased from -180 to -50 mV during the expt. The peak value of lignin degrdn. rate is 0.42% on the 7th day. The COD 1st increases and then decreases. The highest COD is 4068 mg/L, and the final COD degrdn. rate is 46.3%. The peak values of cellulase are 0.021 mg/(mL h) and 0.223 mmol H2/(min mg) at 3 d later than that of hydrogenase. The absorbance of bacterial turbidity 1st increases and then decreases, with the community structure proving that the hydrolytic bacteria are dominated by Acinetobacter, Comamonas, Intestinimonas, and some fermn. bacteria, including Macellibacteroides. The changes of C, O, N, S and functional groups of C and O in coal are obvious, with aliph. C (methoxy, carbonyl, and so on) representing the main part of the biochem. reaction in the macromol. structure of coal. The anal. of the 3-phase state in the process of coal H prodn. is helpful to study the mechanism of H prodn. by coal fermn. from different perspectives, and also provides a ref. for the promotion of coal H prodn. by fermn. in the next step.
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    Sivaramakrishnan, R.; Ramprakash, B.; Ramadoss, G.; Suresh, S.; Pugazhendhi, A.; Incharoensakdi, A. High potential of Rhizopus treated rice bran waste for the nutrient-free anaerobic fermentative biohydrogen production. Bioresources Technol. 2021, 319 (124193), 0960– 8524,  DOI: 10.1016/j.biortech.2020.124193
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    Yin, Z.; Xu, H.; Chen, Y.; Zhao, T.; Wu, J. Experimental simulate on hydrogen production of different coals in underground coal gasification. Int. J. Hydrogen. Energy 2023, 48 (19), 6975– 6985,  DOI: 10.1016/j.ijhydene.2022.03.205
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    Experimental simulate on hydrogen production of different coals in underground coal gasification
    Yin, Zhenyong; Xu, Hao; Chen, Yanpeng; Zhao, Tiantian; Wu, Jingjie
    International Journal of Hydrogen Energy (2023), 48 (19), 6975-6985CODEN: IJHEDX; ISSN:0360-3199. (Elsevier Ltd.)
    Research on hydrogen prodn. from coal gasification is mainly focused on the formation of CO and H2 from coal and water vapor in high-temp. environments. However, in the process of underground coal gasification, the water gas shift reaction of low-temp. steam will absorb a lot of heat, which makes it difficult to maintain the combustion of coal seams in the process of underground coal gasification. In order to obtain high-quality hydrogen, a pure oxygen-steam gasification process is used to improve the gasification efficiency. And as the gasification surface continues to recede, the drying, pyrolysis, gasification and combustion reactions of underground coal seams gradually occur. Direct coal gasification can't truly reflect the process of underground coal gasification. In order to simulate the hydrogen prodn. laws of different coal types in the underground gasification process realistically, a two-step gasification process (pyrolysis of coal followed by gasification of the char) was proposed to process coal to produce hydrogen-rich gas. First, the effects of temp. and coal rank on product distribution were studied in the pyrolysis process. Then, the coal char at the final pyrolysis temp. of 900°C was gasified with pure oxygen-steam. The results showed that, the hydrogen prodn. of the three coal chars increased with the increase of temp. during the pyrolysis process, the hydrogen release from Inner Mongolia lignite and Xinjiang long flame coal have the same trend, and the bimodality is obvious. The hydrogen release in the first stage mainly comes from the dehydrogenation of the fat side chain, and the hydrogen release in the second stage mainly comes from the polycondensation reaction in the later stage of pyrolysis, and the pyrolysis process of coal contributes 15.81%-43.33% of hydrogen, as the coal rank increases, the hydrogen prodn. rate gradually decreases. In the gasification process, the release of hydrogen mainly comes from the water gas shift reaction, the hydrogen output is mainly affected by the quality and carbon content of coal char. With the increase of coal rank, the hydrogen output gradually increases, mainly due to the increasing of coal coke yield and carbon content, The gasification process of coal char contributes 56.67-84.19% of hydrogen, in contrast, coal char gasification provides more hydrogen. The total effective gas output of the three coal chars is 0.53-0.81 m3/kg, the hydrogen output is 0.3-0.43 m3/kg, and the percentage of hydrogen is 53.08-56.60%. This study shows that two-step gasification under the condition of pure oxygen-steam gasification agent is an efficient energy process for hydrogen prodn. from underground coal gasification.
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  15. 15
    Li, J.; Zeng, K.; Zhong, D.; Flamant, G.; Nzihou, A.; White, C. E.; Yang, H.; Chen, H. Algae Pyrolysis in Molten NaOH–Na2CO3 for Hydrogen Production. Environ. Sci. Technol. 2023, 57 (16), 6485– 6493,  DOI: 10.1021/acs.est.3c01325
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    Algae Pyrolysis in Molten NaOH-Na2CO3 for Hydrogen Production
    Li, Jun; Zeng, Kuo; Zhong, Dian; Flamant, Gilles; Nzihou, Ange; White, Claire E.; Yang, Haiping; Chen, Hanping
    Environmental Science & Technology (2023), 57 (16), 6485-6493CODEN: ESTHAG; ISSN:1520-5851. (American Chemical Society)
    Biomass pyrolysis within the alk. molten salt is attractive due to its ability to achieve high hydrogen yield under relatively mild conditions. However, poor contact between biomass, esp. the biomass pellet, and hydroxide during the slow heating process, as well as low reaction temps., become key factors limiting the hydrogen prodn. To address these challenges, fast pyrolysis of the algae pellet in molten NaOH-Na2CO3 was conducted at 550, 650, and 750°C. Algae were chosen as feedstock for their high photosynthetic efficiency and growth rate, and the concept of coupling molten salt with concd. solar energy was proposed to address the issue of high energy consumption at high temps. At 750°C, the pollutant gases contg. Cl and S were completely removed, and the HCN removal rate reached 44.92%. During the continuous pyrolysis process, after a slight increase, the hydrogen yield remained stable at 71.48 mmol/g-algae and constituted 86.10% of the gas products, and a min. theor. hydrogen prodn. efficiency of algae can reach 84.86%. Most importantly, the evolution of physicochem. properties of molten NaOH-Na2CO3 was revealed for the first time. Combined with the conversion characteristics of feedstock and gas products, this study provides practical guidance for large-scale application of molten salt including feedstock, operation parameters, and post-treatment process.
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    Liu, Y.; Paskevicius, M.; Wang, H.; Parkinson, G.; Wei, J.; Asif Akhtar, M.; Li, C.-Z. Insights into the mechanism of tar reforming using biochar as a catalyst. Fuel 2021, 296, 120672,  DOI: 10.1016/j.fuel.2021.120672
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    Insights into the mechanism of tar reforming using biochar as a catalyst
    Liu, Yurong; Paskevicius, Mark; Wang, Hongqi; Parkinson, Gordon; Wei, Juntao; Asif Akhtar, Muhammad; Li, Chun-Zhu
    Fuel (2021), 296 (), 120672CODEN: FUELAC; ISSN:0016-2361. (Elsevier Ltd.)
    Biochar is an efficient catalyst for tar removal from syngas during biomass gasification. The aim of this research is to investigate the mechanism of tar reforming using biochar as a catalyst. A series of in situ steam tar reforming expts. were carried out using a two-stage fluidized-bed/fixed-bed reactor at 800°C. Mallee wood biochar (106-250μm) was activated in 15 vol% H2O balanced with Ar for different times (0-50 min) and then used as a catalyst for tar reforming. The online gas compn., light tar compn. and the pore structure of biochar were analyzed using mass spectrometer (MS), GC-MS and synchrotron small angle X-ray scattering (SAXS) resp. An increased ratio of H2/CO was obsd. after reforming with biochar compared to reforming without biochar. The destruction of light tar compds., esp. the non-oxygen-contg. compds., was significantly enhanced when activated biochars were used. Steam activation increased the sp. surface area (SSA), micro- and mesopore vols. in biochar while the values stayed almost unchanged during tar reforming. Results indicate that the micro- and mesopores in biochar promote the diffusion of both small and large tar mols. into the internal surface of biochar. However, the catalytic activity of biochar for tar reforming mainly depends on the content of O-contg. functional groups in biochar. The O-contg. functional groups facilitate the dissocn. of tar mols. to form tar radicals, giving rise to the enhanced tar removal efficiency. Moreover, the formation of tar radicals over O-contg. functional groups appears as the rate-limiting step in the process of catalytic reforming of tar over biochar catalysts.
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    Buentello-Montoya, D.; Zhang, X.; Li, J.; Ranade, V.; Marques, S.; Geron, M. Performance of biochar as a catalyst for tar steam reforming: Effect of the porous structure. Appl. Energy 2020, 259, 114176,  DOI: 10.1016/j.apenergy.2019.114176
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    17
    Performance of biochar as a catalyst for tar steam reforming: Effect of the porous structure
    Buentello-Montoya, David; Zhang, Xiaolei; Li, Jun; Ranade, Vivek; Marques, Simao; Geron, Marco
    Applied Energy (2020), 259 (), 114176CODEN: APENDX; ISSN:0306-2619. (Elsevier Ltd.)
    The application of gasification to thermally treat biomass as carbon neutral resources has been constrained by the tech. challenges assocd. with tar formations, which cause operational problems in downstream equipment for syngas processing. Catalysts, such as transition metals, calcined rocks and char, can be used to catalyze tar reforming. Biochars, which are naturally produced during biomass gasification, are particularly attractive as an alternative catalyst due to their catalytic functions, low cost and long endurance. Despite these promising characteristics, adequate knowledge on the relationship between the porous structure of biochar and its deactivation by coking during the steam reforming of tars is not available. In this work, the influence of the porous structure of biochar on its performance across time for reforming tar was investigated in a fixed-bed reactor, over a temp. range from 650 to 850°C. Regular biochar and phys. activated biochar from the same precursor biomass were employed as bed material. The tar samples were the composed mixt. of benzene, toluene and naphthalene. Both fresh and spent catalysts were analyzed with Brunauer-Emmet-Teller, t-plot, Fourier Transform IR and SEM/Energy Dispersive Spectroscopy. Results showed that, while at moderate temps. of 650 and 750°C, the activated biochar offered a higher tar conversion but more severe deactivation than that of the regular biochar. At the high temp. of 850°C, the difference in the catalytic performance between the two chars was negligible, and over 90% of the initial tar species were removed throughout the 3-h long expts. At 850°C, the coke deposited in the meso- and macro-pores of both chars was gasified, leading to a stable catalytic performance of both chars. The results indicated that meso- and macro-porous biochars are resilient and active enough to become a viable option for tar steam reforming.
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    Guo, F.; Li, X.; Liu, Y.; Peng, K.; Guo, C.; Rao, Z. Catalytic cracking of biomass pyrolysis tar over char-supported catalysts. Energy Convers. Manage. 2018, 167, 81– 90,  DOI: 10.1016/j.enconman.2018.04.094
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    Catalytic cracking of biomass pyrolysis tar over char-supported catalysts
    Guo, Feiqiang; Li, Xiaolei; Liu, Yuan; Peng, Kuangye; Guo, Chenglong; Rao, Zhonghao
    Energy Conversion and Management (2018), 167 (), 81-90CODEN: ECMADL; ISSN:0196-8904. (Elsevier Ltd.)
    The work aims to investigate an effective method of catalytic reforming of tar during biomass high-temp. pyrolysis using rice husk char (RHC) and metal impregnated (Fe, Cu and K) char in a dual-stage reactor. The char and char-supported catalysts exhibited high catalytic performance, in terms of the high tar conversion efficiencies of 77.1% for RHC, 82.7% for K-RHC, 92.6% for Fe-RHC and 90.6% for Cu-RHC at 800°C. Moreover, K-RHC and Cu-RHC catalysts after three cycles still exhibited high activity for tar removal. The catalytic tar conversion by char or char-supported catalysts contributes to improving the yield of syngas, particularly the combustible gases of H2, CO and CH4, corresponding to the syngas yield increasing from 196.6mL/g for thermal reforming to 269.6mL/g for K-RHC, 274.9mL/g for Cu-RHC and 342.7mL/g for Fe-RHC at 800°C, resp. The results from GC-MS anal. illustrated that the addn. of char and char-supported catalysts promoted the transformation of larger polycyclic arom. hydrocarbons into lighter tar compds., leading to an increase in the proportion of single-ring tars. XRD results indicated that the most active phases of the fresh K-RHC, Cu-RHC and Fe-RHC for tar cracking and reforming were KCl, Cu and Fe, resp. Textural characterization showed the addn. of Fe and Cu was in favor of producing highly porous carbon materials and led to the increase in sp. surface area and total pore vol.
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    Duman, G.; Uddin, M. A.; Yanik, J. Hydrogen production from algal biomass via steam gasification. Bioresources Technol. 2014, 166, 24– 30,  DOI: 10.1016/j.biortech.2014.04.096
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    Hydrogen production from algal biomass via steam gasification
    Duman, Gozde; Uddin, Md. Azhar; Yanik, Jale
    Bioresource Technology (2014), 166 (), 24-30CODEN: BIRTEB; ISSN:0960-8524. (Elsevier Ltd.)
    Algal biomasses were tested as feedstock for steam gasification in a dual-bed microreactor in a two-stage process. Gasification expts. were carried out in absence and presence of catalyst. The catalysts used were 10% Fe2O3-90% CeO2 and red mud (activated and natural forms). Effects of catalysts on tar formation and gasification efficiencies were comparatively investigated. It was obsd. that the characteristic of algae gasification was dependent on its components and the catalysts used. The main role of the catalyst was reforming of the tar derived from algae pyrolysis, besides enhancing water gas shift reaction. The tar redn. levels were in the range of 80-100% for seaweeds and of 53-70% for microalgae. Fe2O3-CeO2 was found to be the most effective catalyst. The max. hydrogen yields obtained were 1036 cc/g algae for Fucus serratus, 937 cc/g algae for Laminaria digitata and 413 cc/g algae for Nannochloropsis oculata.
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    Yang, J.; Kaewpanha, M.; Karnjanakom, S.; Guan, G.; Hao, X.; Abudula, A. Steam reforming of biomass tar over calcined egg shell supported catalysts for hydrogen production. Int. J. Hydrogen. Energy 2016, 41 (16), 6699– 6705,  DOI: 10.1016/j.ijhydene.2016.03.056
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    20
    Steam reforming of biomass tar over calcined egg shell supported catalysts for hydrogen production
    Yang, Jingxuan; Kaewpanha, Malinee; Karnjanakom, Surachai; Guan, Guoqing; Hao, Xiaogang; Abudula, Abuliti
    International Journal of Hydrogen Energy (2016), 41 (16), 6699-6705CODEN: IJHEDX; ISSN:0360-3199. (Elsevier Ltd.)
    Calcined egg shell (CES) shows porous structure and exhibits alk. property, which is expected to be applied for the adsorption and decompn. of biomass-derived tar. In this research, steam reforming of tar derived from cedar wood over CES was firstly investigated in a fixed bed reactor and found that CES had high catalytic activity for steam reforming of tar to produce hydrogen-rich gas. Then, iron, nickel, cobalt and copper were loaded on CES, more syngas esp. hydrogen gas was produced. Among them, copper loaded CES exhibited more enhanced catalytic activity. The optimum Cu loading amt. on CES was found to be 1-2 wt%, which resulted in the most amt. of syngas and exhibited excellent reusability.
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    Michel, R.; L̷amacz, A.; Krzton, A.; Djéga-Mariadassou, G.; Burg, P.; Courson, C.; Gruber, R. Steam reforming of α-methylnaphthalene as a model tar compound over olivine and olivine supported nickel. Fuel 2013, 109, 653– 660,  DOI: 10.1016/j.fuel.2013.03.017
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    Steam reforming of α-methylnaphthalene as a model tar compound over olivine and olivine supported nickel
    Michel, Rudy; Lamacz, Agata; Krzton, Andrzej; Djega-Mariadassou, Gerald; Burg, Philippe; Courson, Claire; Gruber, Rene
    Fuel (2013), 109 (), 653-660CODEN: FUELAC; ISSN:0016-2361. (Elsevier Ltd.)
    At high temp., biomass steam gasification generates tars and more particularly Polycyclic Arom. Hydrocarbons (PAHs). To assess the ability of olivine-based catalyst to eliminate the tars by steam reforming, α-methylnaphthalene (MNP) was chosen as model compd. The Ni/olivine has shown a good ability to reform the MNP, much better than olivine alone. Moreover, catalyst water pre-treatment has proven its efficiency. Thereby, this investigation has emphasized secondary reactions such as water gas shift reaction, and an overall mechanism has been proposed, taking into consideration the important role of adsorbed oxygen species coming from water catalytic dissocn. over nickel metal. In addn., catalyst activity and stability have been discussed on the basis of X-ray diffraction (XRD) and SEM coupled with EDX anal., carried out on the samples before and after expts. On the prepd. fresh catalysts, we have shown the presence of NiO-MgO solid soln., formed on the surface of olivine support. Then, after the expt., both Ni metal (Ni0) and Ni-Fe alloys have been obsd.
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    Zhang, L.; Wu, W.; Siqu, N.; Dekyi, T.; Zhang, Y. Thermochemical catalytic-reforming conversion of municipal solid waste to hydrogen-rich synthesis gas via carbon supported catalysts. Chem. Eng. J. 2019, 361, 1617– 1629,  DOI: 10.1016/j.cej.2018.12.115
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    Thermochemical catalytic-reforming conversion of municipal solid waste to hydrogen-rich synthesis gas via carbon supported catalysts
    Zhang, Lu; Wu, Wei; Siqu, Nyima; Dekyi, Tenzin; Zhang, Yongjie
    Chemical Engineering Journal (Amsterdam, Netherlands) (2019), 361 (), 1617-1629CODEN: CMEJAJ; ISSN:1385-8947. (Elsevier B.V.)
    Catalytic-reforming is considered to be an effective way to remove tar and adjust the H2/CO ratio of synthesis gas generated via gasification and reforming of municipal solid waste. The abundance of carbon materials and the variability of their properties provide new opportunities for the development of reforming catalysts. In this study, carbon supported catalysts were prepd. by impregnation with carbon materials as the support, Ni as the main component of the catalysts, the rare earth element Ce as the promoter. The results indicated that Nickel based catalysts can promote tar cracking and increase hydrogen prodn. in the process of catalytic reforming of MSW gasification. Adding a proper amt. of promoter Ce can improve the catalytic performance, promote the tar cracking and hydrogen conversion. When the content of the active component Ni in Ni/C supported catalysts was 15%, the highest concn. of H2 and CO was 29.30 and 21.03%, resp., and the ratio of H2/CO was up to 1.39. When the molar ratio of Ce and Ni was 0.25 in Ce-15%Ni/C supported catalysts, the concn. of H2 reached 37.76%, the concn. of CO was 14.69%, the ratio of H2/CO was 2.57 and tar content was low to 15.32 g/Nm3. A proper addn. of CeO2 can promote the tar cracking conversion from PAHs in tar to alkane. When the molar ratio of Ce and Ni was 0.50, the PAHs in tar almost disappeared, and more chain like aliph. compds. (C19 ∼ C27) appeared, which was beneficial to the subsequent treatment of tar and utilization of synthesis gas.
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  23. 23
    Si, X.; Lu, R.; Zhao, Z.; Yang, X.; Wang, F.; Jiang, H.; Luo, X.; Wang, A.; Feng, Z.; Xu, J.; Lu, F. Catalytic production of low-carbon footprint sustainable natural gas. Nat. Commun. 2022, 13 (1), 258,  DOI: 10.1038/s41467-021-27919-9
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    Catalytic production of low-carbon footprint sustainable natural gas
    Si, Xiaoqin; Lu, Rui; Zhao, Zhitong; Yang, Xiaofeng; Wang, Feng; Jiang, Huifang; Luo, Xiaolin; Wang, Aiqin; Feng, Zhaochi; Xu, Jie; Lu, Fang
    Nature Communications (2022), 13 (1), 258CODEN: NCAOBW; ISSN:2041-1723. (Nature Portfolio)
    Natural gas is one of the foremost basic energy sources on earth. Although biol. process appears as promising valorization routes to transfer biomass to sustainable methane, the recalcitrance of lignocellulosic biomass is the major limitation for the prodn. of mixing gas to meet the natural gas compn. of pipeline transportation. Here we develop a catalytic-drive approach to directly transfer solid biomass to bio-natural gas which can be suitable for the current infrastructure. A catalyst with Ni2Al3 alloy phase enables nearly complete conversion of various agricultural and forestry residues, the total carbon yield of gas products reaches up to 93% after several hours at relative low-temp. (300°C). And the catalyst shows powerful processing capability for the prodn. of natural gas during thirty cycles. A low-carbon footprint is estd. by a preliminary life cycle assessment, esp. for the low hydrogen pressure and non-fossil hydrogen, and tech. economic anal. predicts that this process is an economically competitive prodn. process.
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    Liang, S.; Guo, F.; Du, S.; Tian, B.; Dong, Y.; Jia, X.; Qian, L. Synthesis of Sargassum char-supported Ni-Fe nanoparticles and its application in tar cracking during biomass pyrolysis. Fuel 2020, 275, 117923,  DOI: 10.1016/j.fuel.2020.117923
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    Synthesis of Sargassum char-supported Ni-Fe nanoparticles and its application in tar cracking during biomass pyrolysis
    Liang, Shuang; Guo, Feiqiang; Du, Shilin; Tian, Beile; Dong, Yichen; Jia, Xiaopeng; Qian, Lin
    Fuel (2020), 275 (), 117923CODEN: FUELAC; ISSN:0016-2361. (Elsevier Ltd.)
    Ni-Fe nanoparticles (NPs) supported on biomass char were synthesized by a pyrolysis method using an abundant and fast-growing seaweed biomass (Sargassum) as the precursor for biomass tar cracking applications. With the presence of Ni and Fe ions, the surface area of the prepd. SC@0.0.05Ni-Fe and SC@0.1Ni-Fe was larger than 200 m2 g-1 with unique honeycomb-like structures, which was conducive to improving the absorption capacity of the catalyst to tar mols., enhancing the interaction between tar mols. and active sites, and prolonging the reaction time. Well-dispersed Ni NPs and FeNi3 NPs were in situ formed on the surface of the char support during Sargassum pyrolysis. At a low temp. of 600°C, the fresh SC@0.1Ni-Fe reached a high tar conversion efficiency of 90.07% with a significant increase in the syngas yield. The yields of the combustible gas components (H2, CO, and CH4) were significantly improved as a result of the tar cracking. After five times successive reuse under the same conditions, the SC@0.1Ni-Fe was able to maintain the tar conversion efficiency at a level of higher than 80%. The structure of the char-supported Ni-Fe catalysts was well retained with the change of the honeycomb-like structure to a certain extent, ensuring the high stability of the catalyst.
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    Gao, N.; Salisu, J.; Quan, C.; Williams, P. Modified nickel-based catalysts for improved steam reforming of biomass tar: A critical review. Renewable Sustainable Energy Rev. 2021, 145, 111023,  DOI: 10.1016/j.rser.2021.111023
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    Modified nickel-based catalysts for improved steam reforming of biomass tar: A critical review
    Gao, Ningbo; Salisu, Jamilu; Quan, Cui; Williams, Paul
    Renewable & Sustainable Energy Reviews (2021), 145 (), 111023CODEN: RSERFH; ISSN:1364-0321. (Elsevier Ltd.)
    A review. The gasification of biomass produces a syngas that can be used for electricity generation and fuels/chems. prodn. However, tar is generated along with the syngas as a byproduct which causes problematic issues in the end-use of the syngas, such as blockages, plugging and corrosion. Catalytic steam reforming is a suitable option to convert tar into more syngas in the presence of nickel-based catalysts, as the preferred catalyst, mainly due to their activity and low cost. There has been considerable research reported in the literature on modified nickel-based catalysts for steam tar reforming. These modifications have been carried out in order to improve the performance of the Ni-based catalysts for tar reforming, mainly in terms of catalyst stability and activity. Such improvements are achieved by manipulating the properties of the catalyst. This paper therefore presents a crit. assessment of these modifications on Ni-based catalysts available in the literature for improved tar reforming. The modifications considered in this review were categorized as: the addn. of secondary metal (Fe, Co, Cu, Cr), the addn. of noble metals (Pt, Pd, Rh, Au, Rh, Ir), addn. of rare earth metals as promoters (Ce, La), alkali and alk. earth metals (Sr, Ba, Ca, Mg,Ba) and modification of the support material. The paper aims at understanding the properties responsible for the improved performance of the modified Ni-based catalysts in comparison with unmodified Ni-based catalysts. The review paper will serve as a guide for further improvement of Ni-based catalysts for biomass tar reforming.
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    Liang, D.; Wang, Y.; Chen, M.; Xie, X.; Li, C.; Wang, J.; Yuan, L. Dry reforming of methane for syngas production over attapulgite-derived MFI zeolite encapsulated bimetallic Ni-Co catalysts. Appl. Catal. B 2023, 322, 122088,  DOI: 10.1016/j.apcatb.2022.122088
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    Dry reforming of methane for syngas production over attapulgite-derived MFI zeolite encapsulated bimetallic Ni-Co catalysts
    Liang, Defang; Wang, Yishuang; Chen, Mingqiang; Xie, Xuanlan; Li, Chang; Wang, Jun; Yuan, Liang
    Applied Catalysis, B: Environmental (2023), 322 (), 122088CODEN: ACBEE3; ISSN:0926-3373. (Elsevier B.V.)
    Dry reforming of methane (DRM) shows bright prospects for the treatment and value-added utilization of greenhouse gas, and catalyst inactivation has been a long-standing grand challenge for this process. Here, a catalyst of attapulgite-derived MFI (ADM) zeolite encapsulated Ni-Co alloys was synthesized using a one-pot method. Characterization results demonstrated that the Ni-Co alloys, which could be stably presentduring DRM process, favored the formation of electron-rich Ni metal sites and thus significantly enhanced C-H bond breaking ability. Meanwhile, the ADM zeolite not only firmly anchored metallic sites by pore or layer confinement, but also provided abundant CO2 adsorption/activation centers. These contributed to the improved anti-sinter and anti-coke ability as well as superior DRM activity of 10Ni1Co@ADM-0.1 catalyst. This work is expected to supply guidance for the development of clay-based metallic Ni catalysts and its application in DRM for syngas prodn.
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    Hu, M.; Laghari, M.; Cui, B.; Xiao, B.; Zhang, B.; Guo, D. Catalytic cracking of biomass tar over char supported nickel catalyst. Energy 2018, 145, 228– 237,  DOI: 10.1016/j.energy.2017.12.096
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    Catalytic cracking of biomass tar over char supported nickel catalyst
    Hu, Mian; Laghari, Mahmood; Cui, Baihui; Xiao, Bo; Zhang, Beiping; Guo, Dabin
    Energy (Oxford, United Kingdom) (2018), 145 (), 228-237CODEN: ENEYDS; ISSN:0360-5442. (Elsevier Ltd.)
    Catalytic cracking of biomass tar was investigated using steam gasification obtained char supported nickel catalyst in a lab-scale fixed bed reactor to det. the effects of catalytic cracking temp., Ni loading and gas residence time on product distribution and gas compn. Results showed that the optimum catalytic cracking parameters were at 800 °C catalytic cracking temp., 6 wt% Ni loading and 0.5 s gas residence time. The characterizations of tars were detd. by ultimate anal., FTIR and GC-MS. Compared with no catalyst cracking, the relative content of single-ring aroms. in tars obviously increases with the appreciably decreases in polycyclic aroms., O-contg. compds. and heterocyclic compds. after catalytic cracking, esp. in Ni-6/char catalyst condition. The surface characteristics of Pre- and Post- char supported 6 wt% loading Ni catalysts were analyzed with BET, SEM, XRD and XPS. The BET and SEM results indicated that there was a slight deposition of coke on the surface of char after catalytic cracking. Meanwhile, XRD and XPS results indicated that NiO was transformed into Ni via carbothermal and hydrogenation redns. which contributed to the enhancement of tar conversion. These findings manifested that char supported nickel catalyst can be used as a low-cost catalyst to decomp. tar.
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    Feng, D.; Zhao, Y.; Zhang, Y.; Sun, S.; Meng, S.; Guo, Y.; Huang, Y. Effects of K and Ca on reforming of model tar compounds with pyrolysis biochars under H2O or CO2. Chem. Eng. J. 2016, 306, 422– 432,  DOI: 10.1016/j.cej.2016.07.065
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    Effects of K and Ca on reforming of model tar compounds with pyrolysis biochars under H2O or CO2
    Feng, Dongdong; Zhao, Yijun; Zhang, Yu; Sun, Shaozeng; Meng, Shun; Guo, Yangzhou; Huang, Yudong
    Chemical Engineering Journal (Amsterdam, Netherlands) (2016), 306 (), 422-432CODEN: CMEJAJ; ISSN:1385-8947. (Elsevier B.V.)
    Pyrolysis biochar is widely used as the catalyst for tar cracking during biomass gasification. K and Ca in pyrolysis biochar affect the reforming of biomass tar under H2O or CO2 atmosphere significantly. In this paper, the transformation mechanism of H-form/K-loaded/Ca-loaded biochar structures and the reaction route of model tar compds. catalytic reforming were identified. The results show that during the reforming of model tar compds. in 15% H2O or pure CO2 at 800°, the release of K from biochar samples is nearly twice as that of Ca. More O-contg. functional groups are formed on K-loaded biochar than Ca-loaded and H-form biochars. H2O or CO2 activation increases the lattice defects and surface functional groups in biochars to promote the combination between biochar and model tar compds. The pathways for tar reformed in H2O or CO2 by K and Ca in biochar include direct homogeneous reforming and consumed by H2O or CO2 gasification on biochar surface. Tars contg. heteroatoms are converted faster than those contg. aliph. chains and pure arom. rings. On catalytic reforming of naphthalene and toluene with biochars, in 15% H2O atm. the effect of K is about 10% greater than that of Ca, while in pure CO2 atmosphere the effect of K is approx. 5% greater than that of Ca.
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    Wang, S.; Shan, R.; Gu, J.; Zhang, J.; Yuan, H.; Chen, Y. Pyrolysis municipal sludge char supported Fe/Ni catalysts for catalytic reforming of tar model compound. Fuel 2020, 279, 118494,  DOI: 10.1016/j.fuel.2020.118494
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    Pyrolysis municipal sludge char supported Fe/Ni catalysts for catalytic reforming of tar model compound
    Wang, Shuxiao; Shan, Rui; Gu, Jing; Zhang, Jun; Yuan, Haoran; Chen, Yong
    Fuel (2020), 279 (), 118494CODEN: FUELAC; ISSN:0016-2361. (Elsevier Ltd.)
    Pyrolytic char is widely used for tar removal due to its cost-effective and eco-friendly. The waste municipal sludge is selected to produce the composite catalyst with transition metal Fe/Ni, and the as-synthesized catalyst was used in the catalytic cracking of the tar model compd. toluene by a lab.-scale plant. The toluene conversion and the molar ratios of CO, H2, CO2, CH4 and C2H4 in the generated gas were studied. Municipal sludge char-based catalysts are more likely to produce H2-rich syngas (the molar ratio of syngas > 75%), and the molar ratio of H2 can reach 73.3% under optimal conditions. The Fe-Ni bimetallic catalyst combines the advantages of different metal elements to make the catalyst performance more stable. Meanwhile, the effects of residence time (τ) and steam-to-C ratio (S/C) on the conversion rate were studied. As a result, the excessive residence time or steam-to-C ratio will have no more pos. effect on the performance of the catalyst. Ultimately, the catalyst life test of 8 h was carried out, cost-effective and green waste municipal sludge char-supported Fe/Ni catalysts in this work could be used for removal of the tar heavy component toluene.
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    Wang, Y.; Zhang, Y.; Su, L.; Li, X.; Duan, L.; Wang, C.; Huang, T. Hazardous air pollutant formation from pyrolysis of typical Chinese casting materials. Environ. Sci. Technol. 2011, 45 (15), 6539– 6544,  DOI: 10.1021/es200310p
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    Hazardous Air Pollutant Formation from Pyrolysis of Typical Chinese Casting Materials
    Wang, Yujue; Zhang, Ying; Su, Lu; Li, Xiangyu; Duan, Lei; Wang, Chengwen; Huang, Tianyou
    Environmental Science & Technology (2011), 45 (15), 6539-6544CODEN: ESTHAG; ISSN:0013-936X. (American Chemical Society)
    Anal. pyrolysis was conducted to evaluate major hazardous air pollutant (HAP) emissions from pyrolysis of bituminous coal and a furan binder, the 2 most commonly used casting materials for making greensand and furan no-bake molds in Chinese foundries. These 2 materials were flash-pyrolyzed in a Curie-point pyrolyzer at 920° and slowly pyrolyzed in a thermogravimetric analyzer (TGA) from ambient temp. to 1000° at a 30°/min heating rate. Emissions from Curie-point and TGA pyrolysis were analyzed by gas chromatog./mass spectrometer with flame ionization detector. In total, 13 HAP species were identified and quantified in pyrolysis emissions of these materials. Prominent HAP emissions were cresols, benzene, toluene, phenol, and naphthalene for bituminous coal, and m-, p-, and o-xylene for the furan binder. Xylenesulfonic acid, an acidic catalyst in the furan binder, was the major xylene emission source. Thermogravimetry/mass spectrometry monitored HAP emission evolution during TGA pyrolysis. For both casting materials, most emissions were released at 350-700°.
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    Guo, F.; Peng, K.; Liang, S.; Jia, X.; Jiang, X.; Qian, L. Evaluation of the catalytic performance of different activated biochar catalysts for removal of tar from biomass pyrolysis. Fuel 2019, 258, 116204,  DOI: 10.1016/j.fuel.2019.116204
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    Evaluation of the catalytic performance of different activated biochar catalysts for removal of tar from biomass pyrolysis
    Guo, Feiqiang; Peng, Kuangye; Liang, Shuang; Jia, Xiaopeng; Jiang, Xiaochen; Qian, Lin
    Fuel (2019), 258 (), 116204CODEN: FUELAC; ISSN:0016-2361. (Elsevier Ltd.)
    Biomass derived chars via simple synthesis methods play an important role in different applications due to their porous structure, low cost and potential for the catalysis research field. This work prepd. three typical activated char catalysts using KOH, H3PO4 and ZnCl2 as activators and rice husk as precursor for the catalytic decompn. of tar from biomass pyrolysis. Results showed that high surface areas were achieved and inorg. elements were introduced by applying the activators. The char obtained by KOH activation exhibited excellent catalytic performance on tar decompn. due to the high surface area and the presence of potassium compds. Activation using H3PO4 led to a more heterogeneous pore size distribution of biochar, also exhibiting high catalytic performance, while the activation of ZnCl2 might promote the agglomeration of zinc and rice husk contg. inorg. matters, resulting in relatively lower tar conversion efficiency. The tar catalytic decompn. led to the significant increase in the yield of product gas, particularly the combustible gas components such as H2, CO and CH4. GC-MS test results showed that macromol. tar components were generally cracked and phenol was the main components of the residue tar, representing the good selectivity of the catalysts. The catalysts also showed excellent stability for tar cracking process and high catalytic performance was still achieved after five cycling tests. The biochar catalysts remained good porous structure with high surface area and the metals phases were well retained after five recycles, indicating that the biochar catalysts have the potential for long-term practical applications.
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    Wang, S.; Shan, R.; Lu, T.; Zhang, Y.; Yuan, H.; Chen, Y. Pyrolysis char derived from waste peat for catalytic reforming of tar model compound. Appl. Energy 2020, 263, 114565,  DOI: 10.1016/j.apenergy.2020.114565
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    Pyrolysis char derived from waste peat for catalytic reforming of tar model compound
    Wang, Shuxiao; Shan, Rui; Lu, Tao; Zhang, Yuyuan; Yuan, Haoran; Chen, Yong
    Applied Energy (2020), 263 (), 114565CODEN: APENDX; ISSN:0306-2619. (Elsevier Ltd.)
    The pyrolysis char derived from solid waste peat was used in the removal of biomass tar. A lab. dual-stage reactor was designed to obtain a cost-effective and eco-friendly tar removal approach using peat pyrolysis char-based catalyst. Rich pore structure of pyrolysis char can enhance the adsorption and removal performance of tar, the KOH and CO2 activation method were used to increase the pore structure of pyrolysis char. Toluene was chosen as the model compd. of biomass tar for basic research. The effects of pyrolysis char and transition metal Fe on toluene removal were studied. The investigated reforming parameters were reaction temp. (700-900°C), residence time (0.3-0.8 s) and steam-to-carbon ratio (1.5:1-4:1). The results indicated that the peat pyrolysis char-based Fe catalysts showed excellent catalytic performance (toluene conversion >89%) and gas selectivity, esp. the catalyst that activated by CO2 had the best selectivity for syngas (88.1 mol%), and the waste peat catalyst was compared with other waste pyrolysis char-based catalysts. Textural characterization showed that the excellent catalytic activity and stability of the catalysts are due to the presence of FeC and FeSiO3 structures. Such the peat pyrolysis char can as a carrier be used to remove tar and produce high content syngas in pyrolysis process.
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    Shi, C.; Zhang, P. Role of MgO over γ-Al2O3-supported Pd catalysts for carbon dioxide reforming of methane. Appl. Catal. B 2015, 170–171, 43– 52,  DOI: 10.1016/j.apcatb.2015.01.034
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    Role of MgO over γ-Al2O3-supported Pd catalysts for carbon dioxide reforming of methane
    Shi, Chunkai; Zhang, Peng
    Applied Catalysis, B: Environmental (2015), 170-171 (), 43-52CODEN: ACBEE3; ISSN:0926-3373. (Elsevier B.V.)
    A series of Pd/Al2O3 catalysts with varying Mg loading (1, 3, 7 and 10%) were investigated for carbon dioxide reforming of methane. The initial catalytic activities and long-term stabilities in terms of both CO2 and CH4 conversions increased with increasing Mg content when its loading was below 7%. When Mg content was up to 10%, the initial activity and stability decreased. Moreover, Pd7Mg/Al2O3 displayed the highest H2 and CO yields. Characterization results conducted on catalysts before and after reaction test demonstrated that MgO mainly presented in amorphous form for catalysts with additive content below 7%; while a fraction of MgO transformed into cryst. form when more additive was introduced to the catalyst. The amorphous MgO significantly enhanced surface metal dispersion, decreased av. Pd crystallite size and thus improved resistances against both metal sintering and carbon deposition, which contributed to the enhanced initial activities and long-term stabilities. On the contrary, the cryst. MgO decreased exposed Pd active sites, caused metal sintering and thus led to increased amt. of carbon deposition owing to both its neg. decoration effect on surface metal and deterioration effect on textural characteristics of support. These factors were responsible for the worse catalytic performance of Pd10Mg/Al2O3 as compared to that of Pd7Mg/Al2O3.
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    Zhang, J.; Chen, J.; Chen, Z.; Xiong, Q.; Di, Y.; Yin, L.; Tian, Y. A highly efficient bimetallic/biochar composite with enhanced catalytic reforming of pyrolysis tar: Performance and mechanism. Bioresour. Technol. Rep. 2022, 19, 101204,  DOI: 10.1016/j.biteb.2022.101204
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    A highly efficient bimetallic/biochar composite with enhanced catalytic reforming of pyrolysis tar: Performance and mechanism
    Zhang, Jun; Chen, Junjie; Chen, Zhengrui; Xiong, Qinyi; Di, Yingchen; Yin, Linlin; Tian, Yu
    Bioresource Technology Reports (2022), 19 (), 101204CODEN: BTRICJ; ISSN:2589-014X. (Elsevier Ltd.)
    In this study, a highly efficient bimetallic Ni-Fe/char composite catalyst has been synthesized successfully for catalytic cracking of pyrolysis tar and displays excellent catalytic cracking performance with tar conversion efficiency of 95.6 % (35.2 % of H2 yield). The results showed that at the steam/carbon ratio, the reaction temp. and gas residence time of 1.0, 800 °C and 0.5 s resp., the bimetallic char-supported catalysts showed outstanding catalytic performance compared with traditional catalyst, in which the N6F6/C exhibited the best activity under the same conditions. The catalytic mechanism of Ni-Fe based catalysts can be attributed to the formation of a Ni-Fe alloy. Furthermore, the synergy of Ni and Fe contributed to greater activity for toluene cracking and enhancement of fuel-gas yield. Bimetallic Ni-Fe alloy catalysts have a promising potential for application as highly efficient catalysts for tar removal and reutilization via catalytic cracking.
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    Liu, L.; Zhang, Z.; Das, S.; Kawi, S. Reforming of tar from biomass gasification in a hybrid catalysis-plasma system: A review. Appl. Catal. B 2019, 250, 250– 272,  DOI: 10.1016/j.apcatb.2019.03.039
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    Reforming of tar from biomass gasification in a hybrid catalysis-plasma system: A review
    Liu, Lina; Zhang, Zhikun; Das, Sonali; Kawi, Sibudjing
    Applied Catalysis, B: Environmental (2019), 250 (), 250-272CODEN: ACBEE3; ISSN:0926-3373. (Elsevier B.V.)
    A review. The generation of tar in biomass gasification is highly undesirable since the condensation and agglomeration of tar causes clogging and contamination of downstream equipment, leading to low energy efficiency and high maintenance cost. Currently, the most widely used methods for tar reforming are catalytic reforming and plasma reforming. However, the main drawbacks for these two processes are: (i) the rapid catalyst deactivation caused by poisoning, sintering and coke deposition for catalytic reforming, and (ii) low energy efficiency, low selectivity of syngas and the formation of undesirable byproducts for plasma reforming. Recently, therefore, the hybrid plasma-catalysis system has attracted much attention for tar reforming, since it can overcome the above-mentioned drawbacks and generate a synergy effect. The addn. of catalyst in plasma could change the discharge properties of plasma, and the plasma could also modify the catalyst property and change the status of reactants. At present, few review articles have reported and compared the performances of tar reforming in the plasma-only, catalysis-only and hybrid plasma-catalysis system. Therefore, this review paper focus on: (i) the deactivation characteristics and modification methods of steam-reforming catalysts, as well as the mechanism of tar catalytic reforming; (ii) the performance of tar reforming in various plasma reactors and the reaction mechanism based on the anal. of byproducts and energetic plasma species; and (iii) the possible synergistic effect of plasma and heterogeneous catalyst in a hybrid plasma-catalysis system caused by the multiple interactions of plasma and catalysts.
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    Kang, Y.; Tang, Y.; Zhu, L.; Jiang, B.; Xu, X.; Guselnikova, O.; Li, H.; Asahi, T.; Yamauchi, Y. Porous nanoarchitectures of nonprecious metal borides: from controlled synthesis to heterogeneous catalyst applications. ACS Catal. 2022, 12 (23), 14773– 14793,  DOI: 10.1021/acscatal.2c03480
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    Porous Nanoarchitectures of Nonprecious Metal Borides: From Controlled Synthesis to Heterogeneous Catalyst Applications
    Kang, Yunqing; Tang, Yi; Zhu, Liyang; Jiang, Bo; Xu, Xingtao; Guselnikova, Olga; Li, Hexing; Asahi, Toru; Yamauchi, Yusuke
    ACS Catalysis (2022), 12 (23), 14773-14793CODEN: ACCACS; ISSN:2155-5435. (American Chemical Society)
    A review. Porous nonprecious metal-based nanomaterials have gained considerable attention in heterogeneous catalysis owing to their low price, high sp. surface area, efficient mass/electron transfer, tunable pore structure, and unique physicochem. properties. Controlling the phase and compns. of these porous nonprecious metal-based materials is crit. to their applications. Porous nonprecious transition-metal borides (TMBs), typical metal-metalloid alloys, have recently received much interest because of their optimized electronic structure, adjustable crystal phase, and abundant active site. The controlled tuning of the porous structure of TMBs, exploring the relationship between the structure and performance, and understanding the function of B are essential for developing catalysts with excellent performance; however, these factors have rarely been reviewed. Herein, a detailed summary of the synthesis methods of porous TMBs is provided by precisely defining their shape, compn., and pore size/structure. Incorporating B into metals can significantly alter their performance due to the unique metalloid properties of B. Further, we focus on the key roles of B in porous TMBs for related heterogeneous catalytic applications, including phase control, regulated electronic structure, optimized adsorption of reaction intermediates, and enhanced charge transfer and stability. Finally, we outline the shortcomings, challenges, and possible development of porous TMBs, which need to be further explored to increase TMBs' contribution to heterogeneous catalyst applications and beyond.
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    Kang, Y.; Guo, Y.; Zhao, J.; Jiang, B.; Guo, J.; Tang, Y.; Li, H.; Malgras, V.; Amin, M. A.; Nara, H.; Sugahara, Y.; Yamauchi, Y.; Asahi, T. Soft template-based synthesis of mesoporous phosphorus-and boron-codoped NiFe-based alloys for efficient oxygen evolution reaction. Small 2022, 18 (33), 2203411,  DOI: 10.1002/smll.202203411
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    Soft Template-Based Synthesis of Mesoporous Phosphorus- and Boron-Codoped NiFe-Based Alloys for Efficient Oxygen Evolution Reaction
    Kang, Yunqing; Guo, Yanna; Zhao, Jingjing; Jiang, Bo; Guo, Jingru; Tang, Yi; Li, Hexing; Malgras, Victor; Amin, Mohammed A.; Nara, Hiroki; Sugahara, Yoshiyuki; Yamauchi, Yusuke; Asahi, Toru
    Small (2022), 18 (33), 2203411CODEN: SMALBC; ISSN:1613-6810. (Wiley-VCH Verlag GmbH & Co. KGaA)
    Controlling the morphol., compn., and cryst. phase of mesoporous nonnoble metal catalysts is essential for improving their performance. Herein, well-defined P and B-codoped NiFe alloy mesoporous nanospheres (NiFeB-P MNs) with an adjustable Ni/Fe ratio and large mesopores (11 nm) are synthesized via soft-template-based chem. redn. and a subsequent phosphine-vapor-based phosphidation process. Earth-abundant NiFe-based materials are considered promising electrocatalysts for the oxygen evolution reaction (OER) because of their low cost and high intrinsic catalytic activity. The resulting NiFeB-P MNs exhibit a low OER overpotential of 252 mV at 10 mA cm-2, which is significantly smaller than that of B-doped NiFe MNs (274 mV) and com. RuO2 (269 mV) in alk. electrolytes. Thus, this work highlights the practicality of designing mesoporous nonnoble metal structures and the importance of incorporating P in metallic-B-based alloys to modify their electronic structure for enhancing their intrinsic activity.
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  38. 38
    Santamaria, L.; Lopez, G.; Arregi, A.; Amutio, M.; Artetxe, M.; Bilbao, J.; Olazar, M. Influence of the support on Ni catalysts performance in the in-line steam reforming of biomass fast pyrolysis derived volatiles. Appl. Catal. B 2018, 229, 105– 113,  DOI: 10.1016/j.apcatb.2018.02.003
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    Influence of the support on Ni catalysts performance in the in-line steam reforming of biomass fast pyrolysis derived volatiles
    Santamaria, Laura; Lopez, Gartzen; Arregi, Aitor; Amutio, Maider; Artetxe, Maite; Bilbao, Javier; Olazar, Martin
    Applied Catalysis, B: Environmental (2018), 229 (), 105-113CODEN: ACBEE3; ISSN:0926-3373. (Elsevier B.V.)
    The influence the support has on the performance of Ni catalysts used in the reforming of biomass fast pyrolysis volatiles has been assessed. Accordingly, five catalysts have been prepd. by wet impregnation method, namely Ni/Al2O3, Ni/SiO2, Ni/MgO, Ni/TiO2 and Ni/ZrO2. These catalysts have been characterized by nitrogen adsorption/desorption, X-ray fluorescence spectroscopy, temp. programmed redn. and X-ray diffraction techniques. The pyrolysis-reforming runs have been performed in a bench scale unit operating in continuous regime. The biomass (pine wood sawdust) pyrolysis step has been carried out in a conical spouted bed reactor at 500°C, with the volatiles produced (a mixt. of gases and bio-oil) being reformed in-line on the prepd. catalysts in a fluidized bed reactor at 600°C. Remarkable differences have been obsd. amongst the catalyst prepd., with Ni/Al2O3, Ni/MgO and Ni/ZrO2 being those leading to the most encouraging results, whereas Ni/TiO2 and, esp. Ni/SiO2, having a limited reforming activity. The performance of each catalyst has been related to its properties detd. in the characterization.
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    Fang, S.; Cui, Z.; Zhu, Y.; Wang, C.; Bai, J.; Zhang, X.; Xu, Y.; Liu, Q.; Chen, L.; Zhang, Q.; Ma, L. In situ synthesis of biomass-derived Ni/C catalyst by self-reduction for the hydrogenation of levulinic acid to γ-valerolactone. J. Energy Chem. 2019, 37, 204– 214,  DOI: 10.1016/j.jechem.2019.03.021
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    Li, Y.; Men, Y.; Liu, S.; Wang, J.; Wang, K.; Tang, Y.; An, W.; Pan, X.; Li, L. Remarkably efficient and stable Ni/Y2O3 catalysts for CO2 methanation: Effect of citric acid addition. Appl. Catal. B 2021, 293, 120206,  DOI: 10.1016/j.apcatb.2021.120206
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    Remarkably efficient and stable Ni/Y2O3 catalysts for CO2 methanation: Effect of citric acid addition
    Li, Yingying; Men, Yong; Liu, Shuang; Wang, Jinguo; Wang, Kang; Tang, Yuhan; An, Wei; Pan, Xiaoli; Li, Lin
    Applied Catalysis, B: Environmental (2021), 293 (), 120206CODEN: ACBEE3; ISSN:0926-3373. (Elsevier B.V.)
    Citric acid has been investigated for prepg. the highly dispersed nickel catalysts on Y2O3 support. A highly enhanced methanation activity with the high CO2 conversion of 92% and CH4 selectivity of 100% was obtained over Ni/Y2O3 with optimum addn. of citric acid at 350°C. The citric acid additives during the prepn. are found to influence the size of nickel nanoparticles and the interaction of metal and support, as estd. by various techniques, which, in turn, to correlated with the catalytic performance. In situ DRIFTS spectra further indicate the importance of small Ni particles on formation of carbonates and formate species as key intermediates and the subsequent hydrogenation of those species into methane. This study proposes that the Y-O-Ni interfacial structure formed by the strong Ni and Y2O3 interaction at high citric acid addn. is of prime importance for the formation of methane, benefiting from the more abundant basic sites and metallic Ni to enable CO2 activation and hydrogenation of key intermediates by effective H2 dissocn. resp. This work provides a new design strategy for developing highly efficient composite CO2 methanation catalysts by control of the metal particle size and charge transfer via metal/support interface.
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    Jin, H.; Yu, R.; Hu, C.; Ji, P.; Ma, Q.; Liu, B.; He, D.; Mu, S. Size-controlled engineering of cobalt metal catalysts through a coordination effect for oxygen electro catalysis. Appl. Catal. B 2022, 317, 121766,  DOI: 10.1016/j.apcatb.2022.121766
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    Size-controlled engineering of cobalt metal catalysts through a coordination effect for oxygen electrocatalysis
    Jin, Huihui; Yu, Ruohan; Hu, Chenxi; Ji, Pengxia; Ma, Qianli; Liu, Bingshuai; He, Daping; Mu, Shichun
    Applied Catalysis, B: Environmental (2022), 317 (), 121766CODEN: ACBEE3; ISSN:0926-3373. (Elsevier B.V.)
    In the prepn. process of carbon-based transition metal catalysts, the transition metal atoms usually seriously agglomerate, thus reducing the catalytic activity. To slow down the agglomeration of transition metal atoms during high-temp. treatments, herein, orgs. with coordination functions are proposed to regulate the typical metal-org. framework compd. ZIF-67 with rich Co atoms. Electron microscopy structural characterization proves that ZIF-67 modified by coordinated org. compds., including ascorbic acid (AA), citric acid (CA) and EDTA disodium salt (EA), greatly improves the dispersibility of cobalt in the final product. All the adjusted ZIF-67 can derive cobalt-based bifunctional oxygen catalysts with higher activity. Among them, EA-MOF-Co shows the best ORR performance, with a half-wave potential comparable to com. Pt/C in alk. solns. and an obviously reduced oxygen evolution overpotential. This suggests that it is an effective method for use of coordination orgs. to tether metal ions and prevent their further agglomeration during carbonation.
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    Meng, J.; Zhao, Z.; Wang, X.; Zheng, A.; Zhang, D.; Huang, Z.; Zhao, K.; Wei, G.; Li, H. Comparative study on phenol and naphthalene steam reforming over Ni-Fe alloy catalysts supported on olivine synthesized by different methods. Energy Convers. Manage. 2018, 168, 60– 73,  DOI: 10.1016/j.enconman.2018.04.112
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    42
    Comparative study on phenol and naphthalene steam reforming over Ni-Fe alloy catalysts supported on olivine synthesized by different methods
    Meng, Junguang; Zhao, Zengli; Wang, Xiaobo; Zheng, Anqing; Zhang, Dongyan; Huang, Zhen; Zhao, Kun; Wei, Guoqiang; Li, Haibin
    Energy Conversion and Management (2018), 168 (), 60-73CODEN: ECMADL; ISSN:0196-8904. (Elsevier Ltd.)
    Ni/Fe bimetallic catalysts were synthesized on an olivine support using the wetness impregnation (WI) and thermal fusion (TF) methods, and catalytic cracking and steam reforming on different tar model compds. (phenol and naphthalene) were investigated in a fixed bed reactor. The effects of the reaction temp. and space-time on the catalytic cracking activity of phenol and naphthalene were tested, and the influences of steam on the carbon molar ratio (S/C) and different synthesized methods on the steam reforming of phenol and naphthalene were also studied. In addn., the carbon deposited on the catalyst was analyzed using temp. program oxidn. (TPO), Raman spectroscopy and transmission electron microscopy (TEM) methods. The elemental compn. of the catalyst was analyzed by X-ray fluorescence (XRF), and the physiochem. properties of the catalysts were characterized via X-ray diffraction (XRD), the BET surface area, SEM (SEM), TEM, Raman spectroscopy, temp. program redn. (TPR), and XPS. The results showed that the structure of TF-Ni/Fe/olivine changed considerably compared with that of calcined olivine (mainly the Mg2SiO4 phase) and that a portion of Fe was fused into the olivine structure and reorganized into a new (Mg, Fe) Fe2O4 phase. After redn., the Ni-Fe alloy was detected on both catalysts, and the particle size of the Ni-Fe alloy on TF-Ni/Fe/olivine was smaller than that of WI-Ni/Fe/olivine. The TF-Ni/Fe/olivine cracked phenol into small-mol. gas (CO and H2) and a small quantity of olefin. By contrast, phenol was polymd. to naphthalene in the absence of a catalyst. The phenol and naphthalene steam reforming conversion on WI-Ni/Fe/olivine were both higher than that of TF-Ni/Fe/olivine. A 100-h stability test of phenol steam reforming on TF-Ni/Fe/olivine and WI-Ni/Fe/olivine was conducted, and TF-Ni/Fe/olivine showed higher stability in the early stages of the expt. due to stronger interactions between the active sites and olivine support. The deposited carbon from naphthalene steam reforming was more difficult to eliminate because it contained more Cβ and Cγ, which had higher degrees of graphitization.
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    Santamaria, L.; Lopez, G.; Arregi, A.; Artetxe, M.; Amutio, M.; Bilbao, J.; Olazar, M. Catalytic steam reforming of biomass fast pyrolysis volatiles over Ni–Co bimetallic catalysts. J. Ind. Eng. Chem. 2020, 91, 167– 181,  DOI: 10.1016/j.jiec.2020.07.050
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    Catalytic steam reforming of biomass fast pyrolysis volatiles over Ni-Co bimetallic catalysts
    Santamaria, Laura; Lopez, Gartzen; Arregi, Aitor; Artetxe, Maite; Amutio, Maider; Bilbao, Javier; Olazar, Martin
    Journal of Industrial and Engineering Chemistry (Amsterdam, Netherlands) (2020), 91 (), 167-181CODEN: JIECFI; ISSN:1226-086X. (Elsevier B.V.)
    The influence of the metal selected as catalytic active phase in the two-step biomass pyrolysis-catalytic reforming strategy has been analyzed. The pyrolysis step was carried out in a conical spouted bed reactor at 500 °C, whereas steam reforming was performed in a fluidized bed reactor at 600 °C. Ni/Al2O3, Co/Al2O3 and two bimetallic Ni-Co/Al2O3 catalysts with different metal loadings were synthesized by wet impregnation method, and fresh and deactivated catalysts were characterized by N2 adsorption/desorption, X-ray Fluorescence (XRF), Temp. Programmed Redn. (TPR), X-Ray powder Diffraction (XRD), Temp. Programmed Oxidn. (TPO), SEM (SEM) and Transmission Electron Microscopy (TEM). Although Ni/Al2O3 and both bimetallic catalysts had similar initial activity in terms of oxygenate conversion, (higher than 98%), the poorer metal dispersion obsd. in both bimetallic catalysts led to a fast decrease in conversion due to the promotion of coke formation on large particles. This occurred even though Ni-Co alloy formation has a pos. influence by hindering the oxidn. of Co0 species. The poor initial performance of Co/Al2O3 catalyst is related to changes in the Co0 oxidn. state induced by the presence of steam, which led to a fast deactivation of this catalyst.
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    Moyer, M. M.; Karakaya, C.; Kee, R. J.; Trewyn, B. G. In-Situ Formation of Metal Carbide Catalysts. ChemCatchem 2017, 9 (16), 3090– 3101,  DOI: 10.1002/cctc.201700304
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    In Situ Formation of Metal Carbide Catalysts
    Moyer, Megan M.; Karakaya, Canan; Kee, Robert J.; Trewyn, Brian G.
    ChemCatChem (2017), 9 (16), 3090-3101CODEN: CHEMK3; ISSN:1867-3880. (Wiley-VCH Verlag GmbH & Co. KGaA)
    A review; metal carbide catalysts are essential to many widely used chem. processes. Fischer-Tropsch synthesis, methane dehydroaromatization and biomass conversion catalysts are typically prepd. in situ from a metal oxide precursor with a carbon-contg. gas. The redn. process of the metal oxide affects the final catalyst, as does the carburization gas mixt. and metal promoters. By looking at materials that are carburized in situ, new insights can be gained about catalyst activation, fuel processing, and deactivation stages. The main focuses of this Review are iron carbide, molybdenum carbide and nickel carbide; analyzing catalyst synthesis methods, redn. steps, in situ carburization and improvements to the native processes. By combining years of research on these catalysts, trends and similarities are obsd. that can be used to improve current catalytic studies.
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    Shen, Y.; Zhao, P.; Shao, Q.; Ma, D.; Takahashi, F.; Yoshikawa, K. In-situ catalytic conversion of tar using rice husk char-supported nickel-iron catalysts for biomass pyrolysis/gasification. Appl. Catal. B 2014, 152–153, 140– 151,  DOI: 10.1016/j.apcatb.2014.01.032
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    45
    In-situ catalytic conversion of tar using rice husk char-supported nickel-iron catalysts for biomass pyrolysis/gasification
    Shen, Yafei; Zhao, Peitao; Shao, Qinfu; Ma, Dachao; Takahashi, Fumitake; Yoshikawa, Kunio
    Applied Catalysis, B: Environmental (2014), 152-153 (), 140-151CODEN: ACBEE3; ISSN:0926-3373. (Elsevier B.V.)
    This paper aims to propose an effective tar conversion approach during biomass pyrolysis via in-situ dry reforming over rice husk (RH) char and char-supported Ni-Fe catalysts. Using high pyrolysis temp., tar from biomass pyrolysis could be removed effectively in the gasifier by mixing with the char-supported catalysts, simplifying the follow-up tar removal process. Under the optimized conditions, the conversion efficiencies of condensable tar can reach ∼92.3% and 93% using Ni-Fe char (without calcination) and Ni char (with calcination), resp. It is noteworthy that the condensable tar could be catalytically transformed into the noncondensable tar or small mol. gases resulting in the heating value increase of gaseous products to benefit of the power generation systems. Compared with the other catalysts prepn. methods, Ni-Fe char exhibited more advantages of convenient and energy-saving. In the presence of catalysts, the concn. of CO2 (vol.%) was reduced slightly, while the CO concn. (vol.%) increased greatly because of dry reforming. Due to C loss, parts of RH char-supported catalysts (C-SiO2 catalysts) could be converted into SiO2-based catalysts because of high-content amorphous nano-sized SiO2 in RH char. Partial metal oxides or ions via C (i.e., biochar) and gas (i.e., H2, CO) in-situ redn. were transformed into metallic states contributing to the enhancement of tar conversion. Therefore, RH char plays two significant roles during the process of biomass pyrolysis. On one hand, it works as an intermediate reductant to reduce the metal oxides and CO2; however, it can be considered as an adsorptive-support to adsorb metal ions and tar. After that, the char-supported catalysts could be used for tar conversion. In particular, since the metal catalysts still remain in the solid residues, the pyrolysis char could be regenerated via thermal regeneration using waste heat or gasified into syngas directly.
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    Gai, C.; Zhang, F.; Yang, T.; Liu, Z.; Jiao, W.; Peng, N.; Liu, T.; Lang, Q.; Xia, Y. Hydrochar supported bimetallic Ni–Fe nanocatalysts with tailored composition, size and shape for improved biomass steam reforming performance. Green Chem. 2018, 20 (12), 2788– 2800,  DOI: 10.1039/C8GC00433A
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    Hydrochar supported bimetallic Ni-Fe nanocatalysts with tailored composition, size and shape for improved biomass steam reforming performance
    Gai, Chao; Zhang, Fang; Yang, Tianxue; Liu, Zhengang; Jiao, Wentao; Peng, Nana; Liu, Tingting; Lang, Qianqian; Xia, Yu
    Green Chemistry (2018), 20 (12), 2788-2800CODEN: GRCHFJ; ISSN:1463-9262. (Royal Society of Chemistry)
    Multicomponent nickel-iron alloy nanoparticles supported on hydrochar were synthesized by a facile one-step hydrothermal strategy. Spinel nickel ferrite (NiFe2O4) with a small cryst. size around 10 nm was uniformly dispersed on a bimetallic catalyst. The roles of the Ni/Fe doping concn. and calcination temp. in tailoring the phase, morphol. and size of the Ni-Fe alloy nanoparticles were investigated. To probe the catalytic abilities of the prepd. bimetallic catalysts, a two-stage reaction system was applied for steam gasification of sewage sludge. Compared to monometallic nickel nanoparticles, the synthesized bimetallic catalyst, esp. Ni0.25Fe0.25/HC calcined at 700 °C, showed excellent dispersibility of the Ni-Fe alloy NPs and exhibited a strong metal-support interaction, which allowed for better suppression of carbon deposition and nanoparticle agglomeration in the reforming process. The best catalytic performance resulted in a promoted hydrogen selectivity of 113.7 g H2 per kg sludge with a low tar yield of 2.3 mg g-1 under mild gasification conditions. These shape- and size-modulated nanocatalysts harbor promising potential for their application as a highly efficient catalyst for hydrogen prodn. via steam gasification of sewage sludge.
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    Nabgan, W.; Tuan Abdullah, T. A.; Mat, R.; Nabgan, B.; Gambo, Y.; Triwahyono, S. Influence of Ni to Co ratio supported on ZrO2 catalysts in phenol steam reforming for hydrogen production. Int. J. Hydrogen. Energy 2016, 41 (48), 22922– 22931,  DOI: 10.1016/j.ijhydene.2016.10.055
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    Influence of Ni to Co ratio supported on ZrO2 catalysts in phenol steam reforming for hydrogen production
    Nabgan, Walid; Tuan Abdullah, Tuan Amran; Mat, Ramli; Nabgan, Bahador; Gambo, Yahya; Triwahyono, Sugeng
    International Journal of Hydrogen Energy (2016), 41 (48), 22922-22931CODEN: IJHEDX; ISSN:0360-3199. (Elsevier Ltd.)
    In this work, catalytic steam reforming of phenol for hydrogen prodn. was investigated. This study focuses on the effects of Ni to Co ratio supported on ZrO2 catalysts. The NixCoy/ZrO2 (x = 0, 1, 2, 3, 4 where x + y = 4) catalysts were prepd. by impregnation method. Steam reforming activity was tested in a fixed bed reactor at 600 °C using a feed of phenol/water mixt. at a molar ratio of 1:9 and a const. liq. feed rate of 0.36 mL/min. The catalysts were characterized by BET surface area, X-ray diffraction (XRD), transmission electron microscopy (TEM), NH3 Temp.-Programmed Desorption (NH3-TPD), CO2 Temp.-Programmed Desorption (CO2-TPD), H2 Temp.-Programmed Redn. (H2-TPR) and thermo-gravimetric anal. (TGA). The increase in the Co content from 0 to 4, caused a decrease in the crystal size, the t-ZrO2 phase and the reducibility of the catalysts. However, it only slightly affected the total surface area. It was found that metallic Ni4 and Co4 catalysts have lower activity towards phenol steam reforming and deposit higher coke due to having higher acidity sites compare to bimetallic catalysts. In contrast, Ni3Co1 displayed a superior catalytic activity among all the catalysts, suggesting the presence of the highest basic site and high coking resistance. Phenol conversion of 53.5% and hydrogen yield of 50.4% were achieved with the Ni3Co1 catalyst, even though its activity decreased by increasing the cobalt content.
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    Yang, F.-L.; Cao, J.-P.; Zhao, X.-Y.; Ren, J.; Tang, W.; Huang, X.; Feng, X.-B.; Zhao, M.; Cui, X.; Wei, X.-Y. Acid washed lignite char supported bimetallic Ni-Co catalyst for low temperature catalytic reforming of corncob derived volatiles. Energy Convers. Manage. 2019, 196, 1257– 1266,  DOI: 10.1016/j.enconman.2019.06.075
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    Acid washed lignite char supported bimetallic Ni-Co catalyst for low temperature catalytic reforming of corncob derived volatiles
    Yang, Fei-Long; Cao, Jing-Pei; Zhao, Xiao-Yan; Ren, Jie; Tang, Wen; Huang, Xin; Feng, Xiao-Bo; Zhao, Ming; Cui, Xin; Wei, Xian-Yong
    Energy Conversion and Management (2019), 196 (), 1257-1266CODEN: ECMADL; ISSN:0196-8904. (Elsevier Ltd.)
    Acid washed Shengli lignite (AWSL) supported Ni, Co and Ni-Co catalysts were prepd., characterized and evaluated in catalytic reforming (CR) of corncob pyrolysis volatiles at a relatively low catalytic temp. of 450°C. Moreover, the prodn. and selectivity of H2 were also investigated. Amongst the catalysts studied, bimetallic Ni-10%Co/AWSL exhibited the most remarkable activity, yielding 36.3 mmol H2/g corncob and 710μmol min-1 g-1 formation rate of syngas (H2 + CO + 4CH4) with trace of tar. It also tuned the gas compn. and showed the greatest selectivity of H2 due to the promotion of the water gas shift reaction (with H2 accounting for the max. 50.3% and 63% under Ar and steam atm., resp.). Regardless of the loss of sp. surface area, the superior performance of Ni-Co based catalysts under mild circumstance was attributed to the better reducibility and electronic properties along with a high dispersion of active metal. Addnl., the synergy of Ni and Co contributed to the combined and enlarged activity for CR of corncob volatiles and great selectivity for H2-rich syngas under moderate condition.
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    Wu, Y.-L.; Yang, R.-R.; Yang, G.-P.; Yan, Y.-T.; Su, X.-L.; He, X.-H.; Song, Y.-Y.; Ma, Z.-S.; Wang, Y.-Y. A new porous Co(ii)-metal–organic framework for high sorption selectivity and affinity to CO2 and efficient catalytic oxidation of benzyl alcohols to benzaldehydes. CrystEngcomm 2021, 23 (20), 3717– 3723,  DOI: 10.1039/D1CE00250C
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    A new porous Co(II)-metal-organic framework for high sorption selectivity and affinity to CO2 and efficient catalytic oxidation of benzyl alcohols to benzaldehydes
    Wu, Yun-Long; Yang, Rong-Rong; Yang, Guo-Ping; Yan, Yang-Tian; Su, Xiao-Lei; He, Xin-Hai; Song, Yan-Yan; Ma, Zheng-Sheng; Wang, Yao-Yu
    CrystEngComm (2021), 23 (20), 3717-3723CODEN: CRECF4; ISSN:1466-8033. (Royal Society of Chemistry)
    Herein, we report a new 3D porous Co(II)-based metal-org. framework catalyst (Me2NH2)2[Co3(L)2(H2O)2]·2DMF (MOF I), which has been successfully prepd. by using Co(II) ions and rigid V-shaped 3,5-di(2,4-dicarboxylphenyl)pyridine (H4L) via the solvothermal reaction. Structural anal. reveals that I displays a porous structure with the pore size of 16.2 x 7.2 Å2 based on the trinuclear [Co3(COO)4(H2O)2N2] secondary building units (SBUs). Gas sorption expts. on the guest free sample I' reveals a high capacity and selectivity to CO2 over CH4. And further, the catalytic explorations of the I'-catalyzed system (I': 3 mol%; proline: 40 mol%; CH3CN: 2 mL) reveal that benzyl alcs. with different structures can be efficiently transformed into benzyl alcs. without byproducts under mild conditions.
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  50. 50
    Ashok, J.; Dewangan, N.; Das, S.; Hongmanorom, P.; Wai, M. H.; Tomishige, K.; Kawi, S. Recent progress in the development of catalysts for steam reforming of biomass tar model reaction. Fuel Process. Technol. 2020, 199, 106252,  DOI: 10.1016/j.fuproc.2019.106252
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    50
    Recent progress in the development of catalysts for steam reforming of biomass tar model reaction
    Ashok, Jangam; Dewangan, Nikita; Das, Sonali; Hongmanorom, Plaifa; Wai, Ming Hui; Tomishige, Keiichi; Kawi, Sibudjing
    Fuel Processing Technology (2020), 199 (), 106252CODEN: FPTEDY; ISSN:0378-3820. (Elsevier Ltd.)
    This review describes recent advances in development of catalysts for steam reforming of biomass tar model reactions, using toluene, benzene and naphthalene as tar model compds. Catalytic systems have been categorized based on their catalytic properties. The material properties such as oxygen mobility and basicity of catalysts showed great influence in their effectiveness in tar reforming. Changes in the properties such as oxygen mobility and basicity with various metal and/or support modifications and their influence on catalytic behavior with respect to reactant conversion and coke inhibition is comprehensively discussed. The activity of the catalysts derived from various synthesis methods is also introduced. The changes induced in the pathways of steam reforming reactions by catalyst modification is also highlighted together with changes in catalytic properties. Reaction pathways for steam reforming of toluene by exptl. studies together with insights gained from computational DFT studies is also presented.
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    Aramouni, N. A. K.; Touma, J. G.; Tarboush, B. A.; Zeaiter, J.; Ahmad, M. N. Catalyst design for dry reforming of methane: Analysis review. Renewable Sustainable Energy Rev. 2018, 82, 2570– 2585,  DOI: 10.1016/j.rser.2017.09.076
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    Catalyst design for dry reforming of methane: Analysis review
    Aramouni, Nicolas Abdel Karim; Touma, Jad G.; Abu Tarboush, Belal; Zeaiter, Joseph; Ahmad, Mohammad N.
    Renewable & Sustainable Energy Reviews (2018), 82 (Part_3), 2570-2585CODEN: RSERFH; ISSN:1364-0321. (Elsevier Ltd.)
    A review. The performance of catalysts used for the dry reforming of methane can strongly depend on the selection of active metals, supports and promoters. This work studies their effects on the activity and stability of selected catalysts. Designing an economically viable catalyst that maintains high catalytic activity and stability can be achieved by exploiting the synergic effects of combining noble and/or non-noble metals to form highly active and stable bi- and tri-metallic catalysts. Perovskite type catalysts can also constitute a potent and cost effective substituent. Metal oxide supports with surface Lewis base sites are able to reduce carbon formation and yield a greater stability to the catalyst, while noble metal promoters have proven to increase both catalyst activity and stability. Moreover, a successful metal-support-promoter combination should lead to higher metal-support interacrtion, lower redn. temp. and enhancement of the anti-coking and anti-amalgamation properties of the catalyst. However, the effect of each parameter on the overall performance of the catalyst is usually complex, and the catalyst designer is often faced with a tradeoff between activity, stability and ease of activation. Based on the review carried out on various studies, it is concluded that a catalyst design must take into consideration not only the sep. effects of the active metal, support and promoter, but should also include the combined and mutual interactions of these components.
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    Xu, J.; Holthaus, P.; Yang, N.; Jiang, S.; Heupel, A.; Schönherr, H.; Yang, B.; Krumm, W.; Jiang, X. Catalytic tar removal using TiO2/NiWO4-Ni5TiO7 films. Appl. Catal. B 2019, 249, 155– 162,  DOI: 10.1016/j.apcatb.2019.03.006
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    Catalytic tar removal using TiO2/NiWO4-Ni5TiO7 films
    Xu, Jing; Holthaus, Philip; Yang, Nianjun; Jiang, Siyu; Heupel, Alwin; Schoenherr, Holger; Yang, Bing; Krumm, Wolfgang; Jiang, Xin
    Applied Catalysis, B: Environmental (2019), 249 (), 155-162CODEN: ACBEE3; ISSN:0926-3373. (Elsevier B.V.)
    One-dimensional Ni catalysts are more promising than Ni powders for catalytic tar removal from biomass gasification, originating from their unique morphologies and higher sp. surfaces. Herein, the authors demonstrate the application of a Ti supported multilayer system, a TiO2/NiWO4-Ni5TiO7 film, for catalytic tar removal. This film is synthesized via plasma electrolytic oxidn. (PEO) combined with subsequent impregnation and annealing. The surface morphol. and the size of as-synthesized Ni5TiO7 nanowires are detd. mainly by used electrolytes during PEO processes. For catalytic tar removal, a fixed bed reactor is used and naphthalene is chosen as a model tar. This TiO2/NiWO4-Ni5TiO7 film exhibits higher efficiency than thermal cracking as well as long-term stability towards catalytic steam reformation of naphthalene. A naphthalene conversion rate of 63% is achieved at 800° with a short residence time of 0.34 s and a high tar load of 75 g m-3N. Such a TiO2-NiWO4/Ni5TiO7 film is thus promising for future tar removal from biomass gasification in the industry.
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    Lee, Y.-L.; Kim, K.-J.; Hong, G.-R.; Roh, H.-S. Target-oriented water–gas shift reactions with customized reaction conditions and catalysts. Chem. Eng. J. 2023, 458, 141422,  DOI: 10.1016/j.cej.2023.141422
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    Target-oriented water-gas shift reactions with customized reaction conditions and catalysts
    Lee, Yeol-Lim; Kim, Kyoung-Jin; Hong, Ga-Ram; Roh, Hyun-Seog
    Chemical Engineering Journal (Amsterdam, Netherlands) (2023), 458 (), 141422CODEN: CMEJAJ; ISSN:1385-8947. (Elsevier B.V.)
    A review. The conventional hydrogen prodn. process from natural gas includes a water-gas shift reaction (WGSR) as a core step to remove carbon monoxide and produce addnl. hydrogen. The WGSR can be further applied to the upcycling of other types of synthesis gases, such as biomass, municipal solid waste, and coal-derived synthesis gas. We have focused on the reaction conditions and catalysts for the WGSR dealing with diverse types of feed gases for the last 10 years to understand the development progress. Based on the categorization (by the type of feed gas), the tested catalysts, capacity, temp., feed gas compn., steam-to-carbon ratio, and the performance of the catalyst are carefully compared. This review provides insight into the current research trends and perspectives for target-oriented WGSR in each type of feed gas, which can give clues for customization.
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    Bimbela, F.; Ábrego, J.; Puerta, R.; García, L.; Arauzo, J. Catalytic steam reforming of the aqueous fraction of bio-oil using Ni-Ce/Mg-Al catalysts. Appl. Catal. B 2017, 209, 346– 357,  DOI: 10.1016/j.apcatb.2017.03.009
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    Catalytic steam reforming of the aqueous fraction of bio-oil using Ni-Ce/Mg-Al catalysts
    Bimbela, F.; Abrego, J.; Puerta, R.; Garcia, L.; Arauzo, J.
    Applied Catalysis, B: Environmental (2017), 209 (), 346-357CODEN: ACBEE3; ISSN:0926-3373. (Elsevier B.V.)
    The performance of different Ni/Mg-Al catalysts modified with Ce was evaluated in the catalytic steam reforming of aq. fractions of bio-oil from biomass pyrolysis. The effects of several prepn. methods for incorporating Ce as a modifier (co-pptn., impregnation and direct thermal decompn. of the salt precursors), the Ce content (0-5%) and the feed streams (3 different aq. fractions from bio-oil) on the catalyst performance were examd., and the stability and activity of the catalysts were significantly influenced by all these factors. In general, the addn. of Ce to a ref. Ni/Mg-Al catalyst improved the overall C conversion to gas and the yield to H2 as well as enhancing the catalyst stability in the steam reforming of aq. fractions of bio-oils. The best prepn. method was impregnation and the optimal Ce content is 0.5%. Much higher initial C conversion to gas and initial H2 yields was obtained using bio-oils derived from pine than those derived from poplar. A very low coke formation, 103 mg C/(g of catalyst·g of orgs. in the aq. fraction reacted), was achieved using the optimized catalyst, 0.5% Ce prepd. by impregnation.
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    Huang, Z.; Deng, Z.; Feng, Y.; Chen, T.; Chen, D.; Zheng, A.; Wei, G.; He, F.; Zhao, Z.; Wu, J.; Li, H. Exploring the Conversion Mechanisms of Toluene as a Biomass Tar Model Compound on NiFe2O4 Oxygen Carrier. ACS Sustainable Chem. Eng. 2019, 7 (19), 16539– 16548,  DOI: 10.1021/acssuschemeng.9b03831
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    Exploring the Conversion Mechanisms of Toluene as a Biomass Tar Model Compound on NiFe2O4 Oxygen Carrier
    Huang, Zhen; Deng, Zhengbing; Feng, Yuheng; Chen, Tianju; Chen, Dezhen; Zheng, Anqing; Wei, Guoqiang; He, Fang; Zhao, Zengli; Wu, Jinhu; Li, Haibin
    ACS Sustainable Chemistry & Engineering (2019), 7 (19), 16539-16548CODEN: ASCECG; ISSN:2168-0485. (American Chemical Society)
    As a novel biomass gasification technol., chem. looping gasification (CLG) could in situ catalytically crack biomass tar by oxygen carrier (OC). This study compares the reactivity of different OCs (Al2O3, Fe2O3, NiO, NiO+Fe2O3, and NiFe2O4) to crack a biomass tar model compd. (toluene) and preliminarily explores the reaction mechanisms of toluene cracked by NiFe2O4 OC. Among five OCs, NiFe2O4 with a homogeneous Fe/Ni dispersibility shows the best reactivity for toluene cracking with a toluene conversion and H2 yield of 96.83% and 0.91 L/g, resp. Addnl., on the basis of the dispersibility of active sites on the OC sample surface, the reactivity of the other four OCs to crack toluene shows the sequence NiO+Fe2O3 > Fe2O3 > NiO » Al2O3. A large amt. of carbon deposition, including amorphous carbon and graphitized carbon, is generated during toluene catalytic cracking, while the addn. of steam significantly eliminates the carbon deposition. The NiFe2O4 OC shows a dual-function of in situ oxidn.-catalysis during toluene cracking. A mechanism of four steps is proposed for the toluene cracking on OCs: (I) toluene cracking at high temp., (II) redn. of OC, (III) generation of amorphous carbon deposition and (III') formation of graphitized carbon, and (IV) elimination of carbon deposition. The oxygen carrier NiFe2O4 exhibits in situ oxidn.-catalysis for tar cracking, which efficiently decomps. biomass tar into small-mol. gases.
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    Xie, Y.; Su, Y.; Wang, P.; Zhang, S.; Xiong, Y. In-situ catalytic conversion of tar from biomass gasification over carbon nanofibers- supported Fe-Ni bimetallic catalysts. Fuel Process. Technol. 2018, 182, 77– 87,  DOI: 10.1016/j.fuproc.2018.10.019
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    In-situ catalytic conversion of tar from biomass gasification over carbon nanofibers- supported Fe-Ni bimetallic catalysts
    Xie, Yinhang; Su, Yinhai; Wang, Peng; Zhang, Shuping; Xiong, Yuanquan
    Fuel Processing Technology (2018), 182 (), 77-87CODEN: FPTEDY; ISSN:0378-3820. (Elsevier Ltd.)
    Using catalytic conversion to reduce the formation of tar in biomass gasification has received great attention, and catalyst improvement is one of the key issues. In this work, Fe-Ni/carbon nanofibers composite materials were prepd. and used for tar conversion during biomass gasification. Compared with non-catalyst tar conversion, the tar removal efficiency reached 85.76% and the total syngas yield doubled (0.947 L/g) with Fe-Ni/carbon nanofibers catalyst. After 13-time reuse, the tar removal efficiency and syngas yield only decreased by 7.25% and 9.07%, resp. Due to the formation of carbon nanofibers through calcination, a high mesopore vol. of catalyst was achieved which is beneficial to the adsorption and cracking of macromol. tar components. And the Fe0.64Ni0.36 alloy detected in Fe-Ni/carbon nanofibers catalyst has a quite high catalytic ability to arom. compds. Furthermore, the carbon deposition of catalyst can be relieved by the interaction between Fe and Ni, which can effectively maintain the catalytic performance of catalysts. The combination of bimetallic catalyst with carbon nanofibers allows the high catalytic activity and stable cyclability of Fe-Ni/CNF for effective tar conversion.
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    Huang, S.; Xu, H.; Li, H.; Guo, Y.; Sun, Z.; Du, Y.; Li, H.; Zhang, J.; Pang, R.; Dong, Q.; Zhang, S. Preparation and characterization of char supported Ni-Cu nanoalloy catalyst for biomass tar cracking together with syngas-rich gas production. Fuel Process. Technol. 2021, 218, 106858,  DOI: 10.1016/j.fuproc.2021.106858
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    Preparation and characterization of char supported Ni-Cu nanoalloy catalyst for biomass tar cracking together with syngas-rich gas production
    Huang, Sisi; Xu, Hailiang; Li, Hongyan; Guo, Yifeng; Sun, Zhenjie; Du, Yang; Li, Huaju; Zhang, Jinfeng; Pang, Renze; Dong, Qing; Zhang, Shuping
    Fuel Processing Technology (2021), 218 (), 106858CODEN: FPTEDY; ISSN:0378-3820. (Elsevier Ltd.)
    In order to realize the efficient biomass tar cracking into syngas-rich gases, several Aspen wood char (ASC) supported metal catalysts, including the Ni/ASC, Cu/ASC and bimetallic Ni-Cu/ASC catalysts, were synthesized with the method of one-step pyrolysis. The structure of the Ni-Cu/ASC catalyst with Ni-Cu nanoalloy encapsulated in carbon nanofibers (CNFs) was obsd. on the basis of the XRD, SEM and TEM anal. The catalytic performances of the prepd. catalysts on tar cracking were assessed in a two-stage fixed-bed pyrolysis-cracking/reforming device at the catalytic cracking temps. of 600-800°C. In a comparison to the single metal catalysts, the bimetallic Ni-Cu/ASC catalyst exerted a better performance on tar removal and possessed a higher selectivity to H2 and CO. The tar conversion efficiency and syngas (H2 + CO) yield, over the Ni-Cu/ASC catalyst at 800°C, reached up to 93.2% and 581.07 mL/g with the total volumetric content of 72.2% together with H2/CO of 1.1, resp. The Ni-Cu/ASC catalyst resulted in the lowest contents of two-ring and three-ring aroms. accompanied with highest contents of one-ring aroms. in tar. The Ni-Cu/ASC catalyst was reasonably stable because of its good resistance to sintering and carbon deposition.
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    Liu, H.; Chen, T.; Chang, D.; Chen, D.; He, H.; Frost, R. L. Catalytic cracking of tar derived from rice hull gasification over palygorskite-supported Fe and Ni. J. Mol. Catal A Chem. 2012, 363–364, 304– 310,  DOI: 10.1016/j.molcata.2012.07.005
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    Catalytic cracking of tar derived from rice hull gasification over palygorskite-supported Fe and Ni
    Liu, Haibo; Chen, Tianhu; Chang, Dongyin; Chen, Dong; He, Hongping; Frost, Ray L.
    Journal of Molecular Catalysis A: Chemical (2012), 363-364 (), 304-310CODEN: JMCCF2; ISSN:1381-1169. (Elsevier B.V.)
    The catalytic performance of Fe-Ni/PG (PG: palygorskite) catalysts pre-calcined and reduced at 500 °C for catalytic decompn. of tar derived through rice hull gasification was investigated. The materials were characterized by using X-ray diffraction, hydrogen temp. redn., and transmission electron microscopy. The results showed that ferrites with spinel structure ((Fe, Ni)3O4) were formed during prepn. of bimetallic systems during calcination and redn. of the precursors (Fe-Ni/PG catalysts) and NiO metal oxide particles were formed over Fe6-Ni9/PG catalyst. The obtained exptl. data showed that Fe-Ni/PG catalysts had greater catalytic activity than natural PG. Tar removal using Fe6-Ni9/PG catalyst was as high as Fe10-Ni6/PG catalyst (99.5%). Fe6-Ni9/PG showed greater catalytic activity with greater H2 yield and showed stronger resistance to carbon deposition, attributed to the presence of NiO nanoparticles. Thus, the addn. of nickel and iron oxides played an important role in catalytic cracking of rice hull biomass tar.
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    Liu, L.; Liu, Y.; Song, J.; Ahmad, S.; Liang, J.; Sun, Y. Plasma-enhanced steam reforming of different model tar compounds over Ni-based fusion catalysts. J. Hazard. Mater. 2019, 377, 24– 33,  DOI: 10.1016/j.jhazmat.2019.05.019
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    Plasma-enhanced steam reforming of different model tar compounds over Ni-based fusion catalysts
    Liu, Lina; Liu, Yawen; Song, Jianwei; Ahmad, Shakeel; Liang, Jie; Sun, Yifei
    Journal of Hazardous Materials (2019), 377 (), 24-33CODEN: JHMAD9; ISSN:0304-3894. (Elsevier B.V.)
    Tar formation during biomass gasification is undesirable due to the decreased energy efficiency and increased costs for maintaining downstream equipment. The hybrid non-thermal plasma-catalysis method is considered to be a promising alternative, since it overcomes the disadvantages arising from both catalyst deactivation during catalytic reforming and the formation of undesirable liq. byproducts in plasma reforming. SiO2- and ZSM-5-supported Ni-based catalysts with different Ni loadings (0.5, 1, 3, and 5 wt%) were prepd. by thermal fusion and applied to the steam reforming of toluene. Different characterizations of fresh and spent catalysts including XRD, H2-TPR, N2 adsorption-desorption, SEM, TEM, XPS and TGA were conducted to show the properties of catalysts. The results indicated that Ni/ZSM-5 exhibited better performance than Ni/SiO2, due to the increased dispersion of Ni particles and the stronger metal-support interaction of Ni/ZSM-5, which was confirmed by the TEM and H2-TPR results. In addn., the performances of the catalysis-only (CatO), plasma-only (PlO), and in-plasma-catalysis (IPC) systems in steam reforming of different model tar compds. including benzene, toluene, furfural, naphthalene, fluorene and pyrene were compared using Ni(5 wt%)/ZSM-5. Obvious synergistic effects between DBD plasma and Ni(5 wt%)/ZSM-5 was obsd. for syngas prodn. in the IPC system.
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    Kang, S.; He, M.; Yin, C.; Xu, H.; Cai, Q.; Wang, Y.; Cui, L. Graphitic carbon embedded with Fe/Ni nano-catalysts derived from bacterial precursor for efficient toluene cracking. Green Chem. 2020, 22 (6), 1934– 1943,  DOI: 10.1039/C9GC03357B
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    Graphitic carbon embedded with Fe/Ni nano-catalysts derived from bacterial precursor for efficient toluene cracking
    Kang, Shifei; He, Maofen; Yin, Chaochuang; Xu, Haiyang; Cai, Qing; Wang, Yangang; Cui, Lifeng
    Green Chemistry (2020), 22 (6), 1934-1943CODEN: GRCHFJ; ISSN:1463-9262. (Royal Society of Chemistry)
    The environmentally-harmful byproduct - biomass tar - is the major obstacle during biomass gasification, which produces synthetic gas as a clean energy source from agricultural waste or other bio-wastes. The highly-dispersed Fe/Ni-based nano-catalysts are of great research interest because of their great catalytic performance for catalytic biomass tar cracking. Supported Fe/Ni alloy catalysts were recognized as promising tar-cracking catalysts with the ability of redox enhancement and C deposition prevention. However, the controllable synthesis of highly-dispersed Fe/Ni nano-catalysts with high activity and stability remains a huge challenge. Highly-dispersed FeNi alloy catalysts embedded in graphitic C (BC-FeNi) were successfully synthesized by simple calcination of a bacterial precursor, which can be easily harvested by collecting nonpathogenic bacteria in a Fe/Ni ion enriched liq. medium. The bacteria served as a C source and helped to uniformly distribute the Fe-Ni ions in the precursor for subsequent prepn. of highly-dispersed FeNi catalysts. TEM showed the BC-FeNi contained well-dispersed Fe-Ni nanoparticles with sizes of 3-10 nm in a mesoporous graphitic C matrix, which were beneficial for the protection of metal nanoparticles against coking and thus were highly desirable for catalytic biomass tar cracking. The conversion rate of the biomass tar model compd. - toluene by BC-FeNi nano-catalysts was 82.6% at 700° and 95.8% at 800°, which were significantly superior over the control sample supported by active C. Noticeably, the metal loading (1.01%) in the bacteria-derived BC-FeNi catalysts was very lower compared to previous studies using other synthetic methods (usually >10%). This unique nature grants that the bacterial method may enable the facile design and synthesis of other types of practical nano-materials.
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    Kaewpanha, M.; Karnjanakom, S.; Guan, G.; Hao, X.; Yang, J.; Abudula, A. Removal of biomass tar by steam reforming over calcined scallop shell supported Cu catalysts. J. Energy Chem. 2017, 26 (4), 660– 666,  DOI: 10.1016/j.jechem.2017.03.012
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    Huang, Z.; Gao, N.; Lin, Y.; Wei, G.; Zhao, K.; Zheng, A.; Zhao, Z.; Yuan, H.; Li, H. Exploring the migration and transformation of lattice oxygen during chemical looping with NiFe2O4 oxygen carrier. Chem. Eng. J. 2022, 429, 132064,  DOI: 10.1016/j.cej.2021.132064
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    Exploring the migration and transformation of lattice oxygen during chemical looping with NiFe2O4 oxygen carrier
    Huang, Zhen; Gao, Na; Lin, Yan; Wei, Guoqiang; Zhao, Kun; Zheng, Anqing; Zhao, Zengli; Yuan, Haoran; Li, Haibin
    Chemical Engineering Journal (Amsterdam, Netherlands) (2022), 429 (), 132064CODEN: CMEJAJ; ISSN:1385-8947. (Elsevier B.V.)
    Chem. looping (CL) technol. using an oxygen carrier (OC) offers a versatile platform to convert various fuels (e.g., CH4, coal, and biomass) to value-added products (e.g., heat, syngas, and H2) in a clean and efficient approach. Currently, the migration and transformation mechanisms of lattice oxygen in spinel OCs were not extensively investigated, which are considered the cornerstone of OC. In this work, the release-uptake paths of lattice oxygen and the chem. reaction laws at interface were studied in detail using a composite metal oxide (NiFe2O4) as an OC through (in-situ) XPS technol. coupled with fixed bed expts. Mechanistic studies indicate that the chem. reaction interface is fixed on the surface of OC particles, and the concn. gradient between the surface and the bulk drives the transmission of lattice oxygen to achieve the redn. or oxidn. of OC. Addnl., an important hydroxyl ions formation process of OC is confirmed by an in-situ XPS.
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    Ren, J.; Liu, Y.-L. Promoting syngas production from steam reforming of toluene using a highly stable Ni/(Mg, Al)Ox catalyst. Appl. Catal. B 2022, 300, 120743,  DOI: 10.1016/j.apcatb.2021.120743
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    Promoting syngas production from steam reforming of toluene using a highly stable Ni/(Mg, Al)Ox catalyst
    Ren, Jie; Liu, Yi-Ling
    Applied Catalysis, B: Environmental (2022), 300 (), 120743CODEN: ACBEE3; ISSN:0926-3373. (Elsevier B.V.)
    Toluene, as one of the representative biomass tar model compd., has been widely chosen for investigation of biomass tar reforming. Herein, novel Ni/(Mg, Al)Ox (Ni/MAO) catalysts derived from Ni-Mg-Al hydrotalcites were prepd. successfully and used for steam reforming of toluene (SRT). Among all the catalysts, Ni/MAO catalyst prepd. at pH of 10 and aging temp. of 20°C (Ni/MAO-10) exhibited superior activity in toluene conversion (95.3%) and syngas prodn. (833 mmol/g-Ni), as well as the excellent resistance to carbon deposition. Through characterizations, the highest basicity, highest reducibility, tailored "rosette-like" morphol., and larger sp. surface area in Ni/MAO-10 were confirmed. Furthermore, the structure-activity relationship, reforming mechanism, deactivation, and regeneration of the catalyst were comprehensively elaborated from rigorous expts., and meanwhile, the activation energies and turnover frequency (TOF) values of four Ni/MAO catalysts in SRT were calcd. to theor. explain their activities.
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    Theofanidis, S. A.; Galvita, V. V.; Poelman, H.; Batchu, R.; Buelens, L. C.; Detavernier, C.; Marin, G. B. Mechanism of carbon deposits removal from supported Ni catalysts. Appl. Catal. B 2018, 239, 502– 512,  DOI: 10.1016/j.apcatb.2018.08.042
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    Mechanism of carbon deposits removal from supported Ni catalysts
    Theofanidis, Stavros Alexandros; Galvita, Vladimir V.; Poelman, Hilde; Batchu, Rakesh; Buelens, Lukas C.; Detavernier, Christophe; Marin, Guy B.
    Applied Catalysis, B: Environmental (2018), 239 (), 502-512CODEN: ACBEE3; ISSN:0926-3373. (Elsevier B.V.)
    Catalyst deactivation due to carbon deposition is a major issue in all reforming technologies. Because of the significant economic cost of catalyst replacement, catalyst regeneration is increasingly attracting attention. The regeneration mechanism of Ni catalysts, with respect to carbon removal, was investigated on support materials prepd. by one-pot synthesis. The supports were classified based on their redox functionality: Al2O3, MgAl2O4 show no redox properties in contrast to MgFe0.09Al1.91O4 and CeZrO2 that have redox functionality. A Temporal Anal. of Products (TAP) setup was used to investigate the isothermal regeneration mechanism of Ni catalysts at 993 K by O2. Different mechanisms were distinguished depending on the redox functionality of the support material. Two consecutive steps occur on the support that have no redox properties (Al2O3 and MgAl2O4): metallic Ni is oxidized to form NiO (oxidn. step), resulting in an initial local temp. increase of 50-60 K in total, enabling metal particle migration to carbon that was initially sepd. from the metal and subsequent oxidn. through NiO lattice oxygen (redn. step). On the other hand, the mechanism of carbon removal by O2 from Ni catalysts on supports with redox properties does not require particle migration. Two parallel contributions are proposed: (1) Ni metal is oxidized to form NiO, where after lattice oxygen of NiO is used for the oxidn. of carbon that is deposited upon the metals, (2) carbon oxidn. through lattice oxygen that is provided by the support. No dependency of the carbon gasification mechanism on the exposed fraction of the metal (particle size in the nanoscale) or on the structure of the deposited carbon was concluded.
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    Shen, Y. Chars as carbonaceous adsorbents/catalysts for tar elimination during biomass pyrolysis or gasification. Renewable Sustainable Energy Rev. 2015, 43, 281– 295,  DOI: 10.1016/j.rser.2014.11.061
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    Chars as carbonaceous adsorbents/catalysts for tar elimination during biomass pyrolysis or gasification
    Shen, Yafei
    Renewable & Sustainable Energy Reviews (2015), 43 (), 281-295CODEN: RSERFH; ISSN:1364-0321. (Elsevier Ltd.)
    Biomass tar could be produced along with syngas during biomass pyrolysis/gasification. Tar elimination by efficient adsorption and catalytic conversion by carbon-based adsorbents/catalysts with chem. inertness should be attractive methods to commercialize this technol. Biochars are the byproducts of biomass pyrolysis/gasification that can be used as low-cost carbon-based adsorbents to adsorb heavy metals or org. pollutants. Meanwhile, the char-supported catalysts could be simply gasified/burnt to recover the energy from the char without the need of frequently regeneration after deactivation. This review elaborated the recent progress on tar removal by biochars adsorption and catalytic cracking/reforming in detail. Two novel integrated concepts have been proposed that chars can be initially utilized and modified like activated chars for heavy metals or tars adsorption, after that, the satd. char-supported metallic catalysts can be employed for tar conversion. In addn., biomass can directly adsorb the heavy metal ions and realize nascent tar in situ conversion along with the metal nanoparticles in situ generated and embedded in the biochar matrix after pyrolysis. Significantly, the nanocomposite char residue could be catalytically gasified into the useful syngas, accompanied by recycling and reuse of the catalyst metal species in the ash.
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    Liu, Q.; Gu, F.; Gao, J.; Li, H.; Xu, G.; Su, F. Coking-resistant Ni-ZrO2/Al2O3 catalyst for CO methanation. J. Energy Chem. 2014, 23 (6), 761– 770,  DOI: 10.1016/S2095-4956(14)60210-2
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    Fakeeha, A. H.; Khan, W. U.; Al-Fatesh, A. S.; Abasaeed, A. E. Stabilities of zeolite-supported Ni catalysts for dry reforming of methane. Chin. J. Catal. 2013, 34 (4), 764– 768,  DOI: 10.1016/S1872-2067(12)60554-3
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    Sun, H.; Feng, D.; Sun, S.; Wei, Q.; Zhao, Y.; Zhang, Y.; Xie, M.; Qin, Y. Effect of steam on coke deposition during the tar reforming from corn straw pyrolysis over biochar. Fuel Process. Technol. 2021, 224, 107007,  DOI: 10.1016/j.fuproc.2021.107007
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    Effect of steam on coke deposition during the tar reforming from corn straw pyrolysis over biochar
    Sun, Hongliang; Feng, Dongdong; Sun, Shaozeng; Wei, Qingyu; Zhao, Yijun; Zhang, Yu; Xie, Min; Qin, Yukun
    Fuel Processing Technology (2021), 224 (), 107007CODEN: FPTEDY; ISSN:0378-3820. (Elsevier Ltd.)
    Coke deposition is a crit. issue for catalysts in tar reforming. Steam is conducive to tar removal and hydrogen prodn. in biomass pyrolysis, while its effect on coke formation is not well known. Thus, a two-stage fluidized bed/fixed bed reactor was used to study the effect of steam addn. on coke deposition. The primary conclusions are as follows: combining steam and biochar, the tar removal efficiency is more than 90% within 20 min of time on stream (TOS). After the TOS reaches 30 min, the biochar surface is satd. with coke deposition and the sp. surface area of the biochar stops decreasing. The addn. of steam leads to a redn. in the combustion reactivity of the biochar. Besides, the aromatization of the biochar increase and the no. of O-contg. structures decreases. For the tar, the addn. of steam reduces the aliphatics content and increases the O-contg. aroms. content. For the gas compn., the addn. of steam results in the decrease of CH4 yield while the H2 yield increases to 0.12 L/g. The H/C at. ratio of the gas compn. decreases while the O/C at. ratio increases. The active coke is consumed and decompd. after the introduction of steam. The remaining coke is dominated by inert coke. This contributes to the relatively developed pore structure but a weakened combustion reactivity of biochar.
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    Pereira Lopes, R.; Astruc, D. Biochar as a support for nanocatalysts and other reagents: Recent advances and applications. Coord. Chem. Rev. 2021, 426, 213585,  DOI: 10.1016/j.ccr.2020.213585
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    Biochar as a support for nanocatalysts and other reagents: Recent advances and applications
    Pereira Lopes, Renata; Astruc, Didier
    Coordination Chemistry Reviews (2021), 426 (), 213585CODEN: CCHRAM; ISSN:0010-8545. (Elsevier B.V.)
    A review. The transformation and use of the biomass are of fundamental energetic and ecol. interest. The general objective of this review is to provide an overview of biochar (a major biomass product) as a support for nanocatalysts and other reagents, its mode of coordination and activation with nanoparticles and applications. This includes the physico-chem. characteristics of biochar, the advances in its prodn. processes, and its activation and functionalization in order to improve its phys. and chem. characteristics and applications as support in catalysis and environmental decontamination. Biochar is a byproduct produced by carbonization of biomass. In this process, the products of interest are syngas and bio-oil, due to their high calorific value and their diverse applications. However, biochar has interesting characteristics. It can be used as support, allowing to disperse nanoparticles of the catalysts, such as those of the transition metals: Fe, Ag, Ni, Pd, etc. bimetallic compns. such as Ru/Re, Fe/Ni, etc. and metal oxides such as Fe3O4, CO3O4, CuO, TiO2, etc. increasing the reactivity of the system, minimizing the leaching of the catalysts and allowing their re-use. These materials can be employed in the degrdn. of contaminants in aq. systems, soil and sediments, tar reforming reactions and synthesis of fine chems. This review will serve as the basis for new research aiming to add value to this important resource.
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    Yu, J.; Tang, L.; Pang, Y.; Zeng, G.; Wang, J.; Deng, Y.; Liu, Y.; Feng, H.; Chen, S.; Ren, X. Magnetic nitrogen-doped sludge-derived biochar catalysts for persulfate activation: Internal electron transfer mechanism. Chem. Eng. J. 2019, 364, 146– 159,  DOI: 10.1016/j.cej.2019.01.163
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    Magnetic nitrogen-doped sludge-derived biochar catalysts for persulfate activation: Internal electron transfer mechanism
    Yu, Jiangfang; Tang, Lin; Pang, Ya; Zeng, Guangming; Wang, Jiajia; Deng, Yaocheng; Liu, Yani; Feng, Haopeng; Chen, Song; Ren, Xiaoya
    Chemical Engineering Journal (Amsterdam, Netherlands) (2019), 364 (), 146-159CODEN: CMEJAJ; ISSN:1385-8947. (Elsevier B.V.)
    Persulfate-based advanced oxidn. process is a powerful countermeasure for water remediation, where effective and low-cost catalysts are still needed. Herein, a one-pot synthetic method for magnetic nitrogen-doped sludge biochar (MS-biochar) was presented, which exhibited better catalytic property with PDS for tetracycline degrdn. than typical graphitic carbon (graphite powder, graphene oxide and multiwalled carbon nanotubes) and two other types biochars. EDAX manifested the uniform dispersion of elements in MS-biochar. Similar to "top-down", a research thought from whole to part of MS-biochar for contribution measurement was presented, where acid-sol. substance (ASS) was the most important contributor for MS-400/600 while carbon matrix (CM) was dominant for MS-800. Quenching and EPR demonstrated a free-radicals pathway in MS-biochar/PDS, where ASS mainly assumed to be effective for SO·-4 and CM was primarily committed to ·OH generation. EDAX, XPS and Raman studies proved three kinds of catalytic sites, namely the iron compds., doped nitrogen and graphitic carbon. And their activating mechanism were discussed where one internal electron migration path (from sp3 to nanocryst. sp2 carbon) has been first proposed. Reusability, metal leaching detection and pharmaceutical wastewater application indicated the potential of MS-biochar. This work not only presents a potential resource-based disposal of sewage sludge, a novel research thought from whole to part for materials performance measurement, but also provides guidance for carbon materials' design for persulfate activation, esp. for sp2 and sp3 co-hybridized carbons.
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    Mao, Z.; Lustemberg, P. G.; Rumptz, J. R.; Ganduglia-Pirovano, M. V.; Campbell, C. T. Ni nanoparticles on CeO2 (111): energetics, electron transfer, and structure by Ni adsorption calorimetry, spectroscopies, and density functional theory. ACS Catal. 2020, 10 (9), 5101– 5114,  DOI: 10.1021/acscatal.0c00333
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    Ni Nanoparticles on CeO2(111): Energetics, Electron Transfer, and Structure by Ni Adsorption Calorimetry, Spectroscopies, and Density Functional Theory
    Mao, Zhongtian; Lustemberg, Pablo G.; Rumptz, John R.; Ganduglia-Pirovano, M. Veronica; Campbell, Charles T.
    ACS Catalysis (2020), 10 (9), 5101-5114CODEN: ACCACS; ISSN:2155-5435. (American Chemical Society)
    The morphol., interfacial bonding energetics, and charge transfer of Ni clusters and nanoparticles on slightly reduced CeO2-x(111) surfaces at 100-300 K have been studied using single-crystal adsorption calorimetry (SCAC), low-energy ion scattering spectroscopy (LEIS), XPS, LEED (LEED), and d. functional theory (DFT). The initial heat of adsorption of Ni vapor decreased with the extent of pre-redn. (x) of CeO2-x(111), showing that stoichiometric ceria adsorbs Ni more strongly than oxygen vacancies. On CeO1.95(111) at 300 K, the heat dropped quickly with coverage in the first 0.1 ML, attributed to nucleation of Ni clusters on stoichiometric steps, followed by the Ni particles spreading onto less favorable terrace sites. At 100 K, the clusters nucleate on terraces due to slower diffusion. Adsorbed Ni monomers are in the +2 oxidn. state, and they bind more strongly by ~ 45 kJ/mol to step sites than terraces. The measured heat of adsorption vs. av. particle size on terraces is favorably compared to DFT calcns. The Ce 3d XPS line shape showed an increase in Ce3+/Ce4+ ratio with Ni coverage, providing the no. of electrons donated to ceria per Ni atom. The charge transferred per Ni is initially large but strongly decreases with increasing cluster size for both expts. and DFT, and it shows large differences between clusters at steps vs. terraces. This charge is localized on the interfacial Ni and Ce atoms in their at. layers closest to the interface. This knowledge is crucial to understanding the nature of the active sites on the surface of Ni/CeO2 catalysts, for which metal-oxide interactions play a very important role in the activation of O-H and C-H bonds. The changes in these interactions with Ni particle size (metal loading) and the extent of redn. of ceria help to explain how previously reported catalytic activity and selectivity change with these same structural details.
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    Navarro, R. M.; Pena, M. A.; Fierro, J. L. G. Hydrogen production reactions from carbon feedstocks: fossil fuels and biomass. Chem. Rev. 2007, 107 (10), 3952– 3991,  DOI: 10.1021/cr0501994
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    Hydrogen Production Reactions from Carbon Feedstocks: Fossil Fuels and Biomass
    Navarro, R. M.; Pena, M. A.; Fierro, J. L. G.
    Chemical Reviews (Washington, DC, United States) (2007), 107 (10), 3952-3991CODEN: CHREAY; ISSN:0009-2665. (American Chemical Society)
    A review. The fuel cell technol., as well as the prodn. of ammonia and other traditional used, required large amts. of H2. Feedstocks for H2 are methane, liq. hydrocarbons, methanol, coal, biomass and biomass derived products. The common processes to produce H2 from these feeds are steam reforming, partial and autothermal oxidn., catalytic decompn. of CH4, CH4 aromatization, and gasification of biomass in supercrit. water.
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    Rostrup-Nielsen, J. R.; Sehested, J.; No̷rskov, J. K. Hydrogen and synthesis gas by steam-and CO2 reforming. Adv. Catal. 2002, 47, 65– 139,  DOI: 10.1016/S0360-0564(02)47006-X
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    Hydrogen and synthesis gas by steam- and CO2 reforming
    Rostrup-Nielsen, Jens R.; Sehested, Jens; Norskov, Jens K.
    Advances in Catalysis (2002), 47 (), 65-139CODEN: ADCAAX; ISSN:0360-0564. (Elsevier Science)
    A review. Steam reforming reactions will play a key role in new applications of synthesis gas and in a future hydrogen economy. The aim of this review is to provide a coherent description of the catalysis of the reforming reactions. The review is not comprehensive. The first section deals with the applications of synthesis gas and hydrogen and the various synthesis.
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    Boldrin, P.; Gallagher, J. R.; Combes, G. B.; Enache, D. I.; James, D.; Ellis, P. R.; Kelly, G.; Claridge, J. B.; Rosseinsky, M. J. Proxy-based accelerated discovery of Fischer–Tropsch catalysts. Chem. Sci. 2015, 6 (2), 935– 944,  DOI: 10.1039/C4SC02116A
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    Proxy-based accelerated discovery of Fischer-Tropsch catalysts
    Boldrin, Paul; Gallagher, James R.; Combes, Gary B.; Enache, Dan I.; James, David; Ellis, Peter R.; Kelly, Gordon; Claridge, John B.; Rosseinsky, Matthew J.
    Chemical Science (2015), 6 (2), 935-944CODEN: CSHCCN; ISSN:2041-6520. (Royal Society of Chemistry)
    Development of heterogeneous catalysts for complex reactions such as Fischer-Tropsch synthesis of fuels is hampered by difficult reaction conditions, slow characterization techniques such as chemisorption and temp.-programmed redn. and the need for long term stability. High-throughput (HT) methods may help, but their use has until now focused on bespoke micro-reactors for direct measurements of activity and selectivity. These are specific to individual reactions and do not provide more fundamental information on the materials. Here we report using simpler HT characterization techniques (XRD and TGA) along with ageing under Fischer-Tropsch reaction conditions to provide information analogous to metal surface area, degree of redn. and thousands of hours of stability testing time for hundreds of samples per mo. The use of this method allowed the identification of a series of highly stable, high surface area catalysts promoted by Mg and Ru. In an advance over traditional multichannel HT reactors, the chem. and structural information we obtain on the materials allows us to identify the structural effects of the promoters and their effects on the modes of deactivation obsd.
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    Bayram, B.; Soykal, I. I.; Deak, D. V.; Miller, J. T.; Ozkan, U. S. Ethanol steam reforming over Co-based catalysts: Investigation of cobalt coordination environment under reaction conditions. J. Catal. 2011, 284 (1), 77– 89,  DOI: 10.1016/j.jcat.2011.09.001
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    Ethanol steam reforming over Co-based catalysts: Investigation of cobalt coordination environment under reaction conditions
    Bayram, Burcu; Soykal, I. Ilgaz; von Deak, Dieter; Miller, Jeffrey T.; Ozkan, Umit S.
    Journal of Catalysis (2011), 284 (1), 77-89CODEN: JCTLA5; ISSN:0021-9517. (Elsevier Inc.)
    The transformations and the state of cobalt species during steam reforming of ethanol over Co/CeO2 were investigated using in situ x-ray diffraction, controlled-atm. x-ray absorption fine structure, and XPS as well as steady state activity measurements. The catalyst was pretreated under an oxidizing or reducing atm. prior to characterization and activity testing to yield a Co3O4-rich or a Co0-rich surface, resp. While Co3O4 was inactive for ethanol steam reforming, gradual activation of the oxidn.-pretreated catalyst with temp. through redn. in Co3O4 took place under reaction conditions, and, over the activated catalyst, a mixt. of both CoO and metallic Co were obsd. Over the redn.-pretreated catalyst, metallic Co was partially oxidized to CoO during steam reforming of ethanol. The extent of cobalt redn. was obsd. to be independent of the initial state of the metal on the catalyst surface, and cobalt phase had the same compn. under reaction above 450°.
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    Li, Z.; Li, M.; Ashok, J.; Kawi, S. NiCo@NiCo phyllosilicate@CeO2 hollow core shell catalysts for steam reforming of toluene as biomass tar model compound. Energy Convers. Manage. 2019, 180, 822– 830,  DOI: 10.1016/j.enconman.2018.11.034
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    NiCo@NiCo phyllosilicate@CeO2 hollow core shell catalysts for steam reforming of toluene as biomass tar model compound
    Li, Ziwei; Li, Min; Ashok, Jangam; Kawi, Sibudjing
    Energy Conversion and Management (2019), 180 (), 822-830CODEN: ECMADL; ISSN:0196-8904. (Elsevier Ltd.)
    Developing sintering and carbon resistant tar removal catalysts is crucial for biomass gasification technol. Herein, for the first time, NiCo@NiCo phyllosilicate@CeO2 hollow core shell catalysts have been designed for steam reforming of toluene (SRT) as the biomass tar model compd. They show both good catalytic activity and stability within 45 h of time on stream due to their high sintering resistance of NiCo because of the strong interactions between NiCo and CeO2, high metal exposure as a result of the high sp. surface area, high surface metal concn. as well as the high oxygen vacancies as evidenced from the H2-Temp.-programmed redn. (H2-TPR), H2 chemisorption and XPS characterizations resp. Addnl., the synergistic effect between Ni and Co further improves their carbon resistant property. By comparison, Co@Co phyllosilicate@CeO2 catalysts perform the lowest toluene conversion and stability mainly due to their structural instability during reaction resulting from their high Si/Co ratio, leading to their low sp. surface area and Co exposure. The outstanding SRT performance of NiCo@NiCo phyllosilicate@CeO2 catalysts indicates their promising application for steam reforming of biomass tar reaction.
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    Zhai, Y.; Li, C.; Xu, G.; Ma, Y.; Liu, X.; Zhang, Y. Depolymerization of lignin via a non-precious Ni–Fe alloy catalyst supported on activated carbon. Green Chem. 2017, 19 (8), 1895– 1903,  DOI: 10.1039/C7GC00149E
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    Depolymerization of lignin via a non-precious Ni-Fe alloy catalyst supported on activated carbon
    Zhai, Yongxiang; Li, Chuang; Xu, Guangyue; Ma, Yanfu; Liu, Xiaohao; Zhang, Ying
    Green Chemistry (2017), 19 (8), 1895-1903CODEN: GRCHFJ; ISSN:1463-9262. (Royal Society of Chemistry)
    Lignin primarily composed of methoxylated phenylpropanoid subunits is an abundant biomass that can be used to produce aroms. Herein, a series of non-precious bimetallic Ni-Fe/AC catalysts were prepd. for efficiently depolymg. lignin. When organosolv birch lignin was used to det. the efficiency of the catalysts in methanol solvent, the Ni1-Fe1/AC (the ratio of Ni and Fe was 1) : (1) achieved the highest total yield of monomers (23.2 wt%, mainly propylguaiacol and propylsyringol) at 225 °C under 2 MPa H2 for 6 h. From GPC anal., it is also proved that lignin was efficiently depolymd. The Ni-Fe alloy structure was formed according to XRD, HRTEM, H2-TPR and XPS characterization. Based on the model compds.' tests, the Ni1-Fe1/AC catalyst showed high efficiency in ether bond cleavage without hydrogenation of arom. rings which could be attributed to the synergistic effect of Ni and Fe on the alloy structure. The total yield of monomers by using the Ni1-Fe1/AC catalyst reached 39.5 wt% (88% selectivity to PG and PS) when birch wood sawdust was used as the substrate.
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    Zhang, S.; Wang, P.; Chen, Y.; Yao, W.; Li, Z.; Tang, Y. One-Pot Synthesis of Pt Nanobowls Assembled from Ultrafine Nanoparticles for Methanol Oxidation Reaction. Nanomater (Basel) 2022, 12, 19,  DOI: 10.3390/nano12193471
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    Huang, Y.; Cheng, M.; Xiang, Z.; Cui, Y. Facile synthesis of NiCo2S4/CNTs nanocomposites for high-performance supercapacitors. R. Soc. Open Sci. 2018, 5 (9), 180953,  DOI: 10.1098/rsos.180953
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    Facile synthesis of NiCo2S4/ CNTs nanocomposites for high-performance supercapacitors
    Huang, Yunxia; Cheng, Ming; Xiang, Zhongcheng; cui, Yimin
    Royal Society Open Science (2018), 5 (9), 180953/1-180953/11CODEN: RSOSAV; ISSN:2054-5703. (Royal Society)
    Herein, porous NiCo2S4/CNTs nanocomposites were synthesized via a simple hydrothermal method followed by the sulphurization process using different sulfide sources. By comparing two different sulfur sources, the samples using thioacetamide as sulfide source delivered more remarkable electrochem. performance with a high specific capacitance of 1765 F g-1 at 1 A g-1 and an admirable cycling stability with capacitance retention of 71.7% at a high c.d. of 10 A g-1 after 5000 cycles in 2 M KOH aq. electrolyte. Furthermore, an asym. supercapacitor (ASC) device was successfully fabricated with the NiCo2S4/CNTs electrode as the pos. electrode and graphene as the neg. electrode. The device provided a max. energy d. of 29.44Wh kg-1 at a power d. of 812Wkg-1. Even at a high power d. of 8006 W kg-1, the energy d. still reaches 16.68 W h kg-1. Moreover, the ASC presents 89.8% specific capacitance retention after 5000 cycles at 5 A g-1. These results reveal its great potential for supercapacitors in electrochem. energy storage field.
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    Ren, J.; Cao, J.-P.; Yang, F.-L.; Zhao, X.-Y.; Tang, W.; Cui, X.; Chen, Q.; Wei, X.-Y. Layered uniformly delocalized electronic structure of carbon supported Ni catalyst for catalytic reforming of toluene and biomass tar. Energy Convers. Manage. 2019, 183, 182– 192,  DOI: 10.1016/j.enconman.2018.12.093
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    Layered uniformly delocalized electronic structure of carbon supported Ni catalyst for catalytic reforming of toluene and biomass tar
    Ren, Jie; Cao, Jing-Pei; Yang, Fei-Long; Zhao, Xiao-Yan; Tang, Wen; Cui, Xin; Chen, Qiang; Wei, Xian-Yong
    Energy Conversion and Management (2019), 183 (), 182-192CODEN: ECMADL; ISSN:0196-8904. (Elsevier Ltd.)
    Lignite rich in oxygen-contg. species (OCSs) was employed as perfect ion-exchange material for high activity catalyst prepn. HCl treatment Shengli lignite (HSL) selectively removed the org. salt and improved capability of ion exchange. In this paper, highly desirable and layered carbon supported Ni catalyst was prepd. by modified lignite. Thanks to the excellent role of Ni (1 1 1) plane and porous layered graphene-like delocalized electronic structure, specific structure of lignite provides an exchange platform in facilitating the Ni electron transfer during the catalytic reaction process. Ni loaded on HSL (Ni/HSL) showed the great catalytic activity and stability for reforming of toluene and biomass tar. Ni/HSL prepd. at 650°C shows the great activity and stability for toluene steam reforming (TSR) and biomass tar reforming (BTR). A series of instruments (XRD, SEM, TEM, H2-TPR, XPS, CO pulse adsorption, etc.) were employed for characterization. Based on these significant characterizations of catalyst, calcn. of turnover frequency (TOF), and results of conversion of toluene and corncob tar. The results revealed the layered delocalized electronic structure of Ni/HSL, which has lower activation energy than other reported catalysts. Uniform dispersed catalyst was synthesized successfully for reforming of toluene and biomass tar.
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  • Abstract

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    Figure 1

    Figure 1. Effect of different catalysts on (a) T-TMC conversion and H2 yield, (b) gas yield and composition at the reforming temperature of 700 °C, and (c) XRD patterns of different catalysts and SEM-EDS analysis of (d,e) char and (f) 6% Ni/char.

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    Figure 2

    Figure 2. Effect of (a) catalytic reforming temperature of 6% Ni–6% Co/char and (b) promoter Co loading of the Ni–Co alloy nanocatalyst (700 °C) on T-TMC conversion and hydrogen production.

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    Figure 3

    Figure 3. Effect of recycling times of (a) 6% Ni/char and (b) 6% Ni–4% Co/char on M-TMC (weight ratios of toluene:naphthalene:phenol = 5:2:1) conversion and hydrogen yield at the reforming temperature of 700 °C.

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    Figure 4

    Figure 4. SEM image and EDS pattern of (a) the fresh 6% Ni/char (N = 0); (b) the spent 6% Ni/char (N = 1); (c) the spent 6% Ni/char (N = 3); (d) the fresh 6% Ni–4% Co/char (N = 0); (e) the spent 6% Ni-4% Co/char (N = 1); (f) the spent 6% Ni–4% Co/char (N = 5). N represents the recycling times of catalysts.

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    Figure 5

    Figure 5. TG-DTG curves and Raman spectra of the corresponding fresh and spent catalysts. TG-DTG curves of (a,b) 6% Ni/char and (c,d) 6% Ni–4% Co/char; Raman spectra of (e) 6% Ni/char and (f) 6% Ni–4% Co/char.

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    Figure 6

    Figure 6. XRD patterns and XPS survey spectra of the fresh and spent catalysts. XRD patterns of (a) 6% Ni/char and (b) 6% Ni–4% Co/char; XPS survey spectra of (c) high-resolution scans, (d) C 1s regions, (e) Ni 2p regions, and (f) Co 2p regions of 6% Ni–4% Co/char.

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      Wan, Chao; Li, Gui; Wang, Jiapei; Xu, Lixin; Cheng, Dang-guo; Chen, Fengqiu; Asakura, Yusuke; Kang, Yunqing; Yamauchi, Yusuke
      Angewandte Chemie, International Edition (2023), 62 (40), e202305371CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)
      Ammonia borane (AB) is a promising material for chem. H2 storage owing to its high H2 d. (up to 19.6 wt %). However, the development of an efficient catalyst for driving H2 evolution through AB hydrolysis remains challenging. Therefore, a visible-light-driven strategy for generating H2 through AB hydrolysis was implemented in this study using Ni-Pt nanoparticles supported on phosphorus-doped TiO2 (Ni-Pt/P-TiO2) as photocatalysts. Through surface engineering, P-TiO2 was prepd. by phytic-acid-assisted phosphorization and then employed as an ideal support for immobilizing Ni-Pt nanoparticles via a facile co-redn. strategy. Under visible-light irradn. at 283 K, Ni40Pt60/P-TiO2 exhibited improved recyclability and a high turnover frequency of 967.8 molH2 ${{_{{\rm H}{_{2}}}}}$ molPt-1 min-1. Characterization expts. and d. functional theory calcns. indicated that the enhanced performance of Ni40Pt60/P-TiO2 originated from a combination of the Ni-Pt alloying effect, the Mott-Schottky junction at the metal-semiconductor interface, and strong metal-support interactions. These findings not only underscore the benefits of utilizing multipronged effects to construct highly active AB-hydrolyzing catalysts, but also pave a path toward designing high-performance catalysts by surface engineering to modulate the electronic metal-support interactions for other visible-light-induced reactions.
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      H2-rich syngas production through mixed residual biomass and HDPE waste via integrated catalytic gasification and tar cracking plus bio-char upgrading
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      Energy recovery via waste utilization in gasification process is an attractive alternative energy source which is expected to supersede part of the energy from fossil fuels. To enhance the H2-rich syngas prodn. from residual biomass mixed with polymeric waste, a dual stage process involving catalytic steam gasification and tar cracking was integrated as a promising alternative technol. for clean fuel prodn. Generally, the presence of tar causes syngas degrdn. and has been identified as one of the major impurities from the gasification process. This study shows the results obtained from an integrated process with optimization process conditions to enhance H2-rich syngas yield. Nickel and dolomite were used as cheap and effective catalysts in fluidized and fixed bed gasifiers resp., which resulted in high-quality syngas prodn. with a max. hydrogen yield of 284.1 gH2 kg-1feedstock and carbon conversion efficiency (CCE) of 92.4 wt%. Furthermore, the study eventuates the upgrading of the bio-char to carbon nano-tubes (CNT). In fact CNT could be further employed either in gasification process or as electrocatalyst supporting materials for low-temp. fuel cells.
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      A residual biochar-based catalyst has been studied for in-line catalytic reforming process after biomass pyrolysis. Poplar pyrolytic char and Ni/char with different Ni loading were prepd. and used as catalysts for producing hydrogen-rich syngas from poplar wood. XRD, BET, SEM, and TEM anal. were used to characterize the synthesized catalysts. The results show that biochar has abundant pore structure and catalytic activity, which is in favor of bio-oil reforming. When loaded with Ni, biochar can also be used as a support, which directly reduces NiO to active Ni and protects Ni from oxidn. Ni/Char catalyst showed better catalytic activity than biochar. A series of expts. have been performed to det. the optimal operating conditions, such as catalytic temp. and water injection flow rate. The expt. results indicated that the best syngas prodn. of 34.321 mmol per 1 g biomass can be achieved with 10 wt% Ni/Char catalyst at 650°C. When 0.3 mL/min of water was added to the pyrolysis reactor, syngas prodn. was significantly increased to 109.848 mmol per 1 g biomass, owing to the thorough utilization of biol. carbon through reaction with water vapor. Therefore, this study points to innovative and effective approaches to make full use of biomass and biomass residues.
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      A review of advances in bioreactor and bioprocess design for biohydrogen prodn. The state-of-the art of biohydrogen prodn. is discussed emphasizing on prodn. pathways, factors affecting biohydrogen prodn., as well as bioreactor configuration and operation. While biohydrogen prodn. is still in the early stage of development, there have been a variety of lab.- and pilot-scale systems developed with promising potential. Challenges and prospects of biohydrogen prodn. are also outlined.
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      A review. The insights of nanotechnol. for cellulosic biohydrogen prodn. through dark fermn. are reviewed. In this context, impacts of nanomaterial on lignocellulosic biomass to biohydrogen prodn. process have been reviewed. Numerous aspects such as possible replacement of chem. pretreatment method using nanostructured materials, use of immobilized enzyme for a fast rate of reaction and its reusability along with long viability of microbial cells and hydrogenase enzyme for improving productivity are highlights of this review. It is found that various types of nanostructured materials e.g. metallic nanoparticles (Fe°, Ni, Cu, Au, Pd, Au), metal oxide nanoparticles (Fe2O3, F3O4, NiCo2O4, CuO, NiO, CoO, ZnO), nanocomposites (Si@CoFe2O4, Fe3O4/alginate) and graphene-based nanomaterials can influence different parameters of process and therefore may perhaps be utilized for cellulosic biohydrogen prodn.. emphasis has been given on cost issue and synthesis sustainability of nanomaterials for making biohydrogen technol. cost effective. Finally, recent advancements and feasibility of nanomaterials as potential soln. for improved cellulose conversion to biohydrogen prodn. process have been discussed, and this is likely to assist in developing an efficient, economical and sustainable biohydrogen prodn. technol.
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      There is no corresponding record for this reference.
    11. 11
      Fagbohungbe, M. O.; Komolafe, A. O.; Okere, U. V. Renewable hydrogen anaerobic fermentation technology: Problems and potentials. Renewable Sustainable Energy Rev. 2019, 114 (109340), 1364– 0321,  DOI: 10.1016/j.rser.2019.109340
      There is no corresponding record for this reference.
    12. 12
      Xia, D.; Yan, X.; Su, X.; Zhao, W. Analysis of the three-phase state in biological hydrogen production from coal. Int. J. Hydrogen. Energy 2020, 45 (41), 21112– 21122,  DOI: 10.1016/j.ijhydene.2020.05.139
      12
      Analysis of the three-phase state in biological hydrogen production from coal
      Xia, Daping; Yan, Xiatong; Su, Xianbo; Zhao, Weizhong
      International Journal of Hydrogen Energy (2020), 45 (41), 21112-21122CODEN: IJHEDX; ISSN:0360-3199. (Elsevier Ltd.)
      The prodn. of biohydrogen from coal is a new research direction in the bioengineering of coalbed methane. To study the transformation process and mechanism of the gas-liq.-solid tripe phase in biohydrogen prodn. from coal, a biohydrogen prodn. expt. from low-rank coal is carried out under lab. conditions. The results show that: The daily gas prodn. of H reaches a peak value of 1.23 mL/g on the 5th day. The cumulative H prodn. is 6.24 mL/g. The pH of the liq. products gradually decreases to 5, and the Eh gradually increased from -180 to -50 mV during the expt. The peak value of lignin degrdn. rate is 0.42% on the 7th day. The COD 1st increases and then decreases. The highest COD is 4068 mg/L, and the final COD degrdn. rate is 46.3%. The peak values of cellulase are 0.021 mg/(mL h) and 0.223 mmol H2/(min mg) at 3 d later than that of hydrogenase. The absorbance of bacterial turbidity 1st increases and then decreases, with the community structure proving that the hydrolytic bacteria are dominated by Acinetobacter, Comamonas, Intestinimonas, and some fermn. bacteria, including Macellibacteroides. The changes of C, O, N, S and functional groups of C and O in coal are obvious, with aliph. C (methoxy, carbonyl, and so on) representing the main part of the biochem. reaction in the macromol. structure of coal. The anal. of the 3-phase state in the process of coal H prodn. is helpful to study the mechanism of H prodn. by coal fermn. from different perspectives, and also provides a ref. for the promotion of coal H prodn. by fermn. in the next step.
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    13. 13
      Sivaramakrishnan, R.; Ramprakash, B.; Ramadoss, G.; Suresh, S.; Pugazhendhi, A.; Incharoensakdi, A. High potential of Rhizopus treated rice bran waste for the nutrient-free anaerobic fermentative biohydrogen production. Bioresources Technol. 2021, 319 (124193), 0960– 8524,  DOI: 10.1016/j.biortech.2020.124193
      There is no corresponding record for this reference.
    14. 14
      Yin, Z.; Xu, H.; Chen, Y.; Zhao, T.; Wu, J. Experimental simulate on hydrogen production of different coals in underground coal gasification. Int. J. Hydrogen. Energy 2023, 48 (19), 6975– 6985,  DOI: 10.1016/j.ijhydene.2022.03.205
      14
      Experimental simulate on hydrogen production of different coals in underground coal gasification
      Yin, Zhenyong; Xu, Hao; Chen, Yanpeng; Zhao, Tiantian; Wu, Jingjie
      International Journal of Hydrogen Energy (2023), 48 (19), 6975-6985CODEN: IJHEDX; ISSN:0360-3199. (Elsevier Ltd.)
      Research on hydrogen prodn. from coal gasification is mainly focused on the formation of CO and H2 from coal and water vapor in high-temp. environments. However, in the process of underground coal gasification, the water gas shift reaction of low-temp. steam will absorb a lot of heat, which makes it difficult to maintain the combustion of coal seams in the process of underground coal gasification. In order to obtain high-quality hydrogen, a pure oxygen-steam gasification process is used to improve the gasification efficiency. And as the gasification surface continues to recede, the drying, pyrolysis, gasification and combustion reactions of underground coal seams gradually occur. Direct coal gasification can't truly reflect the process of underground coal gasification. In order to simulate the hydrogen prodn. laws of different coal types in the underground gasification process realistically, a two-step gasification process (pyrolysis of coal followed by gasification of the char) was proposed to process coal to produce hydrogen-rich gas. First, the effects of temp. and coal rank on product distribution were studied in the pyrolysis process. Then, the coal char at the final pyrolysis temp. of 900°C was gasified with pure oxygen-steam. The results showed that, the hydrogen prodn. of the three coal chars increased with the increase of temp. during the pyrolysis process, the hydrogen release from Inner Mongolia lignite and Xinjiang long flame coal have the same trend, and the bimodality is obvious. The hydrogen release in the first stage mainly comes from the dehydrogenation of the fat side chain, and the hydrogen release in the second stage mainly comes from the polycondensation reaction in the later stage of pyrolysis, and the pyrolysis process of coal contributes 15.81%-43.33% of hydrogen, as the coal rank increases, the hydrogen prodn. rate gradually decreases. In the gasification process, the release of hydrogen mainly comes from the water gas shift reaction, the hydrogen output is mainly affected by the quality and carbon content of coal char. With the increase of coal rank, the hydrogen output gradually increases, mainly due to the increasing of coal coke yield and carbon content, The gasification process of coal char contributes 56.67-84.19% of hydrogen, in contrast, coal char gasification provides more hydrogen. The total effective gas output of the three coal chars is 0.53-0.81 m3/kg, the hydrogen output is 0.3-0.43 m3/kg, and the percentage of hydrogen is 53.08-56.60%. This study shows that two-step gasification under the condition of pure oxygen-steam gasification agent is an efficient energy process for hydrogen prodn. from underground coal gasification.
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    15. 15
      Li, J.; Zeng, K.; Zhong, D.; Flamant, G.; Nzihou, A.; White, C. E.; Yang, H.; Chen, H. Algae Pyrolysis in Molten NaOH–Na2CO3 for Hydrogen Production. Environ. Sci. Technol. 2023, 57 (16), 6485– 6493,  DOI: 10.1021/acs.est.3c01325
      15
      Algae Pyrolysis in Molten NaOH-Na2CO3 for Hydrogen Production
      Li, Jun; Zeng, Kuo; Zhong, Dian; Flamant, Gilles; Nzihou, Ange; White, Claire E.; Yang, Haiping; Chen, Hanping
      Environmental Science & Technology (2023), 57 (16), 6485-6493CODEN: ESTHAG; ISSN:1520-5851. (American Chemical Society)
      Biomass pyrolysis within the alk. molten salt is attractive due to its ability to achieve high hydrogen yield under relatively mild conditions. However, poor contact between biomass, esp. the biomass pellet, and hydroxide during the slow heating process, as well as low reaction temps., become key factors limiting the hydrogen prodn. To address these challenges, fast pyrolysis of the algae pellet in molten NaOH-Na2CO3 was conducted at 550, 650, and 750°C. Algae were chosen as feedstock for their high photosynthetic efficiency and growth rate, and the concept of coupling molten salt with concd. solar energy was proposed to address the issue of high energy consumption at high temps. At 750°C, the pollutant gases contg. Cl and S were completely removed, and the HCN removal rate reached 44.92%. During the continuous pyrolysis process, after a slight increase, the hydrogen yield remained stable at 71.48 mmol/g-algae and constituted 86.10% of the gas products, and a min. theor. hydrogen prodn. efficiency of algae can reach 84.86%. Most importantly, the evolution of physicochem. properties of molten NaOH-Na2CO3 was revealed for the first time. Combined with the conversion characteristics of feedstock and gas products, this study provides practical guidance for large-scale application of molten salt including feedstock, operation parameters, and post-treatment process.
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    16. 16
      Liu, Y.; Paskevicius, M.; Wang, H.; Parkinson, G.; Wei, J.; Asif Akhtar, M.; Li, C.-Z. Insights into the mechanism of tar reforming using biochar as a catalyst. Fuel 2021, 296, 120672,  DOI: 10.1016/j.fuel.2021.120672
      16
      Insights into the mechanism of tar reforming using biochar as a catalyst
      Liu, Yurong; Paskevicius, Mark; Wang, Hongqi; Parkinson, Gordon; Wei, Juntao; Asif Akhtar, Muhammad; Li, Chun-Zhu
      Fuel (2021), 296 (), 120672CODEN: FUELAC; ISSN:0016-2361. (Elsevier Ltd.)
      Biochar is an efficient catalyst for tar removal from syngas during biomass gasification. The aim of this research is to investigate the mechanism of tar reforming using biochar as a catalyst. A series of in situ steam tar reforming expts. were carried out using a two-stage fluidized-bed/fixed-bed reactor at 800°C. Mallee wood biochar (106-250μm) was activated in 15 vol% H2O balanced with Ar for different times (0-50 min) and then used as a catalyst for tar reforming. The online gas compn., light tar compn. and the pore structure of biochar were analyzed using mass spectrometer (MS), GC-MS and synchrotron small angle X-ray scattering (SAXS) resp. An increased ratio of H2/CO was obsd. after reforming with biochar compared to reforming without biochar. The destruction of light tar compds., esp. the non-oxygen-contg. compds., was significantly enhanced when activated biochars were used. Steam activation increased the sp. surface area (SSA), micro- and mesopore vols. in biochar while the values stayed almost unchanged during tar reforming. Results indicate that the micro- and mesopores in biochar promote the diffusion of both small and large tar mols. into the internal surface of biochar. However, the catalytic activity of biochar for tar reforming mainly depends on the content of O-contg. functional groups in biochar. The O-contg. functional groups facilitate the dissocn. of tar mols. to form tar radicals, giving rise to the enhanced tar removal efficiency. Moreover, the formation of tar radicals over O-contg. functional groups appears as the rate-limiting step in the process of catalytic reforming of tar over biochar catalysts.
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    17. 17
      Buentello-Montoya, D.; Zhang, X.; Li, J.; Ranade, V.; Marques, S.; Geron, M. Performance of biochar as a catalyst for tar steam reforming: Effect of the porous structure. Appl. Energy 2020, 259, 114176,  DOI: 10.1016/j.apenergy.2019.114176
      17
      Performance of biochar as a catalyst for tar steam reforming: Effect of the porous structure
      Buentello-Montoya, David; Zhang, Xiaolei; Li, Jun; Ranade, Vivek; Marques, Simao; Geron, Marco
      Applied Energy (2020), 259 (), 114176CODEN: APENDX; ISSN:0306-2619. (Elsevier Ltd.)
      The application of gasification to thermally treat biomass as carbon neutral resources has been constrained by the tech. challenges assocd. with tar formations, which cause operational problems in downstream equipment for syngas processing. Catalysts, such as transition metals, calcined rocks and char, can be used to catalyze tar reforming. Biochars, which are naturally produced during biomass gasification, are particularly attractive as an alternative catalyst due to their catalytic functions, low cost and long endurance. Despite these promising characteristics, adequate knowledge on the relationship between the porous structure of biochar and its deactivation by coking during the steam reforming of tars is not available. In this work, the influence of the porous structure of biochar on its performance across time for reforming tar was investigated in a fixed-bed reactor, over a temp. range from 650 to 850°C. Regular biochar and phys. activated biochar from the same precursor biomass were employed as bed material. The tar samples were the composed mixt. of benzene, toluene and naphthalene. Both fresh and spent catalysts were analyzed with Brunauer-Emmet-Teller, t-plot, Fourier Transform IR and SEM/Energy Dispersive Spectroscopy. Results showed that, while at moderate temps. of 650 and 750°C, the activated biochar offered a higher tar conversion but more severe deactivation than that of the regular biochar. At the high temp. of 850°C, the difference in the catalytic performance between the two chars was negligible, and over 90% of the initial tar species were removed throughout the 3-h long expts. At 850°C, the coke deposited in the meso- and macro-pores of both chars was gasified, leading to a stable catalytic performance of both chars. The results indicated that meso- and macro-porous biochars are resilient and active enough to become a viable option for tar steam reforming.
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    18. 18
      Guo, F.; Li, X.; Liu, Y.; Peng, K.; Guo, C.; Rao, Z. Catalytic cracking of biomass pyrolysis tar over char-supported catalysts. Energy Convers. Manage. 2018, 167, 81– 90,  DOI: 10.1016/j.enconman.2018.04.094
      18
      Catalytic cracking of biomass pyrolysis tar over char-supported catalysts
      Guo, Feiqiang; Li, Xiaolei; Liu, Yuan; Peng, Kuangye; Guo, Chenglong; Rao, Zhonghao
      Energy Conversion and Management (2018), 167 (), 81-90CODEN: ECMADL; ISSN:0196-8904. (Elsevier Ltd.)
      The work aims to investigate an effective method of catalytic reforming of tar during biomass high-temp. pyrolysis using rice husk char (RHC) and metal impregnated (Fe, Cu and K) char in a dual-stage reactor. The char and char-supported catalysts exhibited high catalytic performance, in terms of the high tar conversion efficiencies of 77.1% for RHC, 82.7% for K-RHC, 92.6% for Fe-RHC and 90.6% for Cu-RHC at 800°C. Moreover, K-RHC and Cu-RHC catalysts after three cycles still exhibited high activity for tar removal. The catalytic tar conversion by char or char-supported catalysts contributes to improving the yield of syngas, particularly the combustible gases of H2, CO and CH4, corresponding to the syngas yield increasing from 196.6mL/g for thermal reforming to 269.6mL/g for K-RHC, 274.9mL/g for Cu-RHC and 342.7mL/g for Fe-RHC at 800°C, resp. The results from GC-MS anal. illustrated that the addn. of char and char-supported catalysts promoted the transformation of larger polycyclic arom. hydrocarbons into lighter tar compds., leading to an increase in the proportion of single-ring tars. XRD results indicated that the most active phases of the fresh K-RHC, Cu-RHC and Fe-RHC for tar cracking and reforming were KCl, Cu and Fe, resp. Textural characterization showed the addn. of Fe and Cu was in favor of producing highly porous carbon materials and led to the increase in sp. surface area and total pore vol.
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    19. 19
      Duman, G.; Uddin, M. A.; Yanik, J. Hydrogen production from algal biomass via steam gasification. Bioresources Technol. 2014, 166, 24– 30,  DOI: 10.1016/j.biortech.2014.04.096
      19
      Hydrogen production from algal biomass via steam gasification
      Duman, Gozde; Uddin, Md. Azhar; Yanik, Jale
      Bioresource Technology (2014), 166 (), 24-30CODEN: BIRTEB; ISSN:0960-8524. (Elsevier Ltd.)
      Algal biomasses were tested as feedstock for steam gasification in a dual-bed microreactor in a two-stage process. Gasification expts. were carried out in absence and presence of catalyst. The catalysts used were 10% Fe2O3-90% CeO2 and red mud (activated and natural forms). Effects of catalysts on tar formation and gasification efficiencies were comparatively investigated. It was obsd. that the characteristic of algae gasification was dependent on its components and the catalysts used. The main role of the catalyst was reforming of the tar derived from algae pyrolysis, besides enhancing water gas shift reaction. The tar redn. levels were in the range of 80-100% for seaweeds and of 53-70% for microalgae. Fe2O3-CeO2 was found to be the most effective catalyst. The max. hydrogen yields obtained were 1036 cc/g algae for Fucus serratus, 937 cc/g algae for Laminaria digitata and 413 cc/g algae for Nannochloropsis oculata.
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    20. 20
      Yang, J.; Kaewpanha, M.; Karnjanakom, S.; Guan, G.; Hao, X.; Abudula, A. Steam reforming of biomass tar over calcined egg shell supported catalysts for hydrogen production. Int. J. Hydrogen. Energy 2016, 41 (16), 6699– 6705,  DOI: 10.1016/j.ijhydene.2016.03.056
      20
      Steam reforming of biomass tar over calcined egg shell supported catalysts for hydrogen production
      Yang, Jingxuan; Kaewpanha, Malinee; Karnjanakom, Surachai; Guan, Guoqing; Hao, Xiaogang; Abudula, Abuliti
      International Journal of Hydrogen Energy (2016), 41 (16), 6699-6705CODEN: IJHEDX; ISSN:0360-3199. (Elsevier Ltd.)
      Calcined egg shell (CES) shows porous structure and exhibits alk. property, which is expected to be applied for the adsorption and decompn. of biomass-derived tar. In this research, steam reforming of tar derived from cedar wood over CES was firstly investigated in a fixed bed reactor and found that CES had high catalytic activity for steam reforming of tar to produce hydrogen-rich gas. Then, iron, nickel, cobalt and copper were loaded on CES, more syngas esp. hydrogen gas was produced. Among them, copper loaded CES exhibited more enhanced catalytic activity. The optimum Cu loading amt. on CES was found to be 1-2 wt%, which resulted in the most amt. of syngas and exhibited excellent reusability.
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    21. 21
      Michel, R.; L̷amacz, A.; Krzton, A.; Djéga-Mariadassou, G.; Burg, P.; Courson, C.; Gruber, R. Steam reforming of α-methylnaphthalene as a model tar compound over olivine and olivine supported nickel. Fuel 2013, 109, 653– 660,  DOI: 10.1016/j.fuel.2013.03.017
      21
      Steam reforming of α-methylnaphthalene as a model tar compound over olivine and olivine supported nickel
      Michel, Rudy; Lamacz, Agata; Krzton, Andrzej; Djega-Mariadassou, Gerald; Burg, Philippe; Courson, Claire; Gruber, Rene
      Fuel (2013), 109 (), 653-660CODEN: FUELAC; ISSN:0016-2361. (Elsevier Ltd.)
      At high temp., biomass steam gasification generates tars and more particularly Polycyclic Arom. Hydrocarbons (PAHs). To assess the ability of olivine-based catalyst to eliminate the tars by steam reforming, α-methylnaphthalene (MNP) was chosen as model compd. The Ni/olivine has shown a good ability to reform the MNP, much better than olivine alone. Moreover, catalyst water pre-treatment has proven its efficiency. Thereby, this investigation has emphasized secondary reactions such as water gas shift reaction, and an overall mechanism has been proposed, taking into consideration the important role of adsorbed oxygen species coming from water catalytic dissocn. over nickel metal. In addn., catalyst activity and stability have been discussed on the basis of X-ray diffraction (XRD) and SEM coupled with EDX anal., carried out on the samples before and after expts. On the prepd. fresh catalysts, we have shown the presence of NiO-MgO solid soln., formed on the surface of olivine support. Then, after the expt., both Ni metal (Ni0) and Ni-Fe alloys have been obsd.
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    22. 22
      Zhang, L.; Wu, W.; Siqu, N.; Dekyi, T.; Zhang, Y. Thermochemical catalytic-reforming conversion of municipal solid waste to hydrogen-rich synthesis gas via carbon supported catalysts. Chem. Eng. J. 2019, 361, 1617– 1629,  DOI: 10.1016/j.cej.2018.12.115
      22
      Thermochemical catalytic-reforming conversion of municipal solid waste to hydrogen-rich synthesis gas via carbon supported catalysts
      Zhang, Lu; Wu, Wei; Siqu, Nyima; Dekyi, Tenzin; Zhang, Yongjie
      Chemical Engineering Journal (Amsterdam, Netherlands) (2019), 361 (), 1617-1629CODEN: CMEJAJ; ISSN:1385-8947. (Elsevier B.V.)
      Catalytic-reforming is considered to be an effective way to remove tar and adjust the H2/CO ratio of synthesis gas generated via gasification and reforming of municipal solid waste. The abundance of carbon materials and the variability of their properties provide new opportunities for the development of reforming catalysts. In this study, carbon supported catalysts were prepd. by impregnation with carbon materials as the support, Ni as the main component of the catalysts, the rare earth element Ce as the promoter. The results indicated that Nickel based catalysts can promote tar cracking and increase hydrogen prodn. in the process of catalytic reforming of MSW gasification. Adding a proper amt. of promoter Ce can improve the catalytic performance, promote the tar cracking and hydrogen conversion. When the content of the active component Ni in Ni/C supported catalysts was 15%, the highest concn. of H2 and CO was 29.30 and 21.03%, resp., and the ratio of H2/CO was up to 1.39. When the molar ratio of Ce and Ni was 0.25 in Ce-15%Ni/C supported catalysts, the concn. of H2 reached 37.76%, the concn. of CO was 14.69%, the ratio of H2/CO was 2.57 and tar content was low to 15.32 g/Nm3. A proper addn. of CeO2 can promote the tar cracking conversion from PAHs in tar to alkane. When the molar ratio of Ce and Ni was 0.50, the PAHs in tar almost disappeared, and more chain like aliph. compds. (C19 ∼ C27) appeared, which was beneficial to the subsequent treatment of tar and utilization of synthesis gas.
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    23. 23
      Si, X.; Lu, R.; Zhao, Z.; Yang, X.; Wang, F.; Jiang, H.; Luo, X.; Wang, A.; Feng, Z.; Xu, J.; Lu, F. Catalytic production of low-carbon footprint sustainable natural gas. Nat. Commun. 2022, 13 (1), 258,  DOI: 10.1038/s41467-021-27919-9
      23
      Catalytic production of low-carbon footprint sustainable natural gas
      Si, Xiaoqin; Lu, Rui; Zhao, Zhitong; Yang, Xiaofeng; Wang, Feng; Jiang, Huifang; Luo, Xiaolin; Wang, Aiqin; Feng, Zhaochi; Xu, Jie; Lu, Fang
      Nature Communications (2022), 13 (1), 258CODEN: NCAOBW; ISSN:2041-1723. (Nature Portfolio)
      Natural gas is one of the foremost basic energy sources on earth. Although biol. process appears as promising valorization routes to transfer biomass to sustainable methane, the recalcitrance of lignocellulosic biomass is the major limitation for the prodn. of mixing gas to meet the natural gas compn. of pipeline transportation. Here we develop a catalytic-drive approach to directly transfer solid biomass to bio-natural gas which can be suitable for the current infrastructure. A catalyst with Ni2Al3 alloy phase enables nearly complete conversion of various agricultural and forestry residues, the total carbon yield of gas products reaches up to 93% after several hours at relative low-temp. (300°C). And the catalyst shows powerful processing capability for the prodn. of natural gas during thirty cycles. A low-carbon footprint is estd. by a preliminary life cycle assessment, esp. for the low hydrogen pressure and non-fossil hydrogen, and tech. economic anal. predicts that this process is an economically competitive prodn. process.
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    24. 24
      Liang, S.; Guo, F.; Du, S.; Tian, B.; Dong, Y.; Jia, X.; Qian, L. Synthesis of Sargassum char-supported Ni-Fe nanoparticles and its application in tar cracking during biomass pyrolysis. Fuel 2020, 275, 117923,  DOI: 10.1016/j.fuel.2020.117923
      24
      Synthesis of Sargassum char-supported Ni-Fe nanoparticles and its application in tar cracking during biomass pyrolysis
      Liang, Shuang; Guo, Feiqiang; Du, Shilin; Tian, Beile; Dong, Yichen; Jia, Xiaopeng; Qian, Lin
      Fuel (2020), 275 (), 117923CODEN: FUELAC; ISSN:0016-2361. (Elsevier Ltd.)
      Ni-Fe nanoparticles (NPs) supported on biomass char were synthesized by a pyrolysis method using an abundant and fast-growing seaweed biomass (Sargassum) as the precursor for biomass tar cracking applications. With the presence of Ni and Fe ions, the surface area of the prepd. SC@0.0.05Ni-Fe and SC@0.1Ni-Fe was larger than 200 m2 g-1 with unique honeycomb-like structures, which was conducive to improving the absorption capacity of the catalyst to tar mols., enhancing the interaction between tar mols. and active sites, and prolonging the reaction time. Well-dispersed Ni NPs and FeNi3 NPs were in situ formed on the surface of the char support during Sargassum pyrolysis. At a low temp. of 600°C, the fresh SC@0.1Ni-Fe reached a high tar conversion efficiency of 90.07% with a significant increase in the syngas yield. The yields of the combustible gas components (H2, CO, and CH4) were significantly improved as a result of the tar cracking. After five times successive reuse under the same conditions, the SC@0.1Ni-Fe was able to maintain the tar conversion efficiency at a level of higher than 80%. The structure of the char-supported Ni-Fe catalysts was well retained with the change of the honeycomb-like structure to a certain extent, ensuring the high stability of the catalyst.
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    25. 25
      Gao, N.; Salisu, J.; Quan, C.; Williams, P. Modified nickel-based catalysts for improved steam reforming of biomass tar: A critical review. Renewable Sustainable Energy Rev. 2021, 145, 111023,  DOI: 10.1016/j.rser.2021.111023
      25
      Modified nickel-based catalysts for improved steam reforming of biomass tar: A critical review
      Gao, Ningbo; Salisu, Jamilu; Quan, Cui; Williams, Paul
      Renewable & Sustainable Energy Reviews (2021), 145 (), 111023CODEN: RSERFH; ISSN:1364-0321. (Elsevier Ltd.)
      A review. The gasification of biomass produces a syngas that can be used for electricity generation and fuels/chems. prodn. However, tar is generated along with the syngas as a byproduct which causes problematic issues in the end-use of the syngas, such as blockages, plugging and corrosion. Catalytic steam reforming is a suitable option to convert tar into more syngas in the presence of nickel-based catalysts, as the preferred catalyst, mainly due to their activity and low cost. There has been considerable research reported in the literature on modified nickel-based catalysts for steam tar reforming. These modifications have been carried out in order to improve the performance of the Ni-based catalysts for tar reforming, mainly in terms of catalyst stability and activity. Such improvements are achieved by manipulating the properties of the catalyst. This paper therefore presents a crit. assessment of these modifications on Ni-based catalysts available in the literature for improved tar reforming. The modifications considered in this review were categorized as: the addn. of secondary metal (Fe, Co, Cu, Cr), the addn. of noble metals (Pt, Pd, Rh, Au, Rh, Ir), addn. of rare earth metals as promoters (Ce, La), alkali and alk. earth metals (Sr, Ba, Ca, Mg,Ba) and modification of the support material. The paper aims at understanding the properties responsible for the improved performance of the modified Ni-based catalysts in comparison with unmodified Ni-based catalysts. The review paper will serve as a guide for further improvement of Ni-based catalysts for biomass tar reforming.
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    26. 26
      Liang, D.; Wang, Y.; Chen, M.; Xie, X.; Li, C.; Wang, J.; Yuan, L. Dry reforming of methane for syngas production over attapulgite-derived MFI zeolite encapsulated bimetallic Ni-Co catalysts. Appl. Catal. B 2023, 322, 122088,  DOI: 10.1016/j.apcatb.2022.122088
      26
      Dry reforming of methane for syngas production over attapulgite-derived MFI zeolite encapsulated bimetallic Ni-Co catalysts
      Liang, Defang; Wang, Yishuang; Chen, Mingqiang; Xie, Xuanlan; Li, Chang; Wang, Jun; Yuan, Liang
      Applied Catalysis, B: Environmental (2023), 322 (), 122088CODEN: ACBEE3; ISSN:0926-3373. (Elsevier B.V.)
      Dry reforming of methane (DRM) shows bright prospects for the treatment and value-added utilization of greenhouse gas, and catalyst inactivation has been a long-standing grand challenge for this process. Here, a catalyst of attapulgite-derived MFI (ADM) zeolite encapsulated Ni-Co alloys was synthesized using a one-pot method. Characterization results demonstrated that the Ni-Co alloys, which could be stably presentduring DRM process, favored the formation of electron-rich Ni metal sites and thus significantly enhanced C-H bond breaking ability. Meanwhile, the ADM zeolite not only firmly anchored metallic sites by pore or layer confinement, but also provided abundant CO2 adsorption/activation centers. These contributed to the improved anti-sinter and anti-coke ability as well as superior DRM activity of 10Ni1Co@ADM-0.1 catalyst. This work is expected to supply guidance for the development of clay-based metallic Ni catalysts and its application in DRM for syngas prodn.
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    27. 27
      Hu, M.; Laghari, M.; Cui, B.; Xiao, B.; Zhang, B.; Guo, D. Catalytic cracking of biomass tar over char supported nickel catalyst. Energy 2018, 145, 228– 237,  DOI: 10.1016/j.energy.2017.12.096
      27
      Catalytic cracking of biomass tar over char supported nickel catalyst
      Hu, Mian; Laghari, Mahmood; Cui, Baihui; Xiao, Bo; Zhang, Beiping; Guo, Dabin
      Energy (Oxford, United Kingdom) (2018), 145 (), 228-237CODEN: ENEYDS; ISSN:0360-5442. (Elsevier Ltd.)
      Catalytic cracking of biomass tar was investigated using steam gasification obtained char supported nickel catalyst in a lab-scale fixed bed reactor to det. the effects of catalytic cracking temp., Ni loading and gas residence time on product distribution and gas compn. Results showed that the optimum catalytic cracking parameters were at 800 °C catalytic cracking temp., 6 wt% Ni loading and 0.5 s gas residence time. The characterizations of tars were detd. by ultimate anal., FTIR and GC-MS. Compared with no catalyst cracking, the relative content of single-ring aroms. in tars obviously increases with the appreciably decreases in polycyclic aroms., O-contg. compds. and heterocyclic compds. after catalytic cracking, esp. in Ni-6/char catalyst condition. The surface characteristics of Pre- and Post- char supported 6 wt% loading Ni catalysts were analyzed with BET, SEM, XRD and XPS. The BET and SEM results indicated that there was a slight deposition of coke on the surface of char after catalytic cracking. Meanwhile, XRD and XPS results indicated that NiO was transformed into Ni via carbothermal and hydrogenation redns. which contributed to the enhancement of tar conversion. These findings manifested that char supported nickel catalyst can be used as a low-cost catalyst to decomp. tar.
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    28. 28
      Feng, D.; Zhao, Y.; Zhang, Y.; Sun, S.; Meng, S.; Guo, Y.; Huang, Y. Effects of K and Ca on reforming of model tar compounds with pyrolysis biochars under H2O or CO2. Chem. Eng. J. 2016, 306, 422– 432,  DOI: 10.1016/j.cej.2016.07.065
      28
      Effects of K and Ca on reforming of model tar compounds with pyrolysis biochars under H2O or CO2
      Feng, Dongdong; Zhao, Yijun; Zhang, Yu; Sun, Shaozeng; Meng, Shun; Guo, Yangzhou; Huang, Yudong
      Chemical Engineering Journal (Amsterdam, Netherlands) (2016), 306 (), 422-432CODEN: CMEJAJ; ISSN:1385-8947. (Elsevier B.V.)
      Pyrolysis biochar is widely used as the catalyst for tar cracking during biomass gasification. K and Ca in pyrolysis biochar affect the reforming of biomass tar under H2O or CO2 atmosphere significantly. In this paper, the transformation mechanism of H-form/K-loaded/Ca-loaded biochar structures and the reaction route of model tar compds. catalytic reforming were identified. The results show that during the reforming of model tar compds. in 15% H2O or pure CO2 at 800°, the release of K from biochar samples is nearly twice as that of Ca. More O-contg. functional groups are formed on K-loaded biochar than Ca-loaded and H-form biochars. H2O or CO2 activation increases the lattice defects and surface functional groups in biochars to promote the combination between biochar and model tar compds. The pathways for tar reformed in H2O or CO2 by K and Ca in biochar include direct homogeneous reforming and consumed by H2O or CO2 gasification on biochar surface. Tars contg. heteroatoms are converted faster than those contg. aliph. chains and pure arom. rings. On catalytic reforming of naphthalene and toluene with biochars, in 15% H2O atm. the effect of K is about 10% greater than that of Ca, while in pure CO2 atmosphere the effect of K is approx. 5% greater than that of Ca.
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    29. 29
      Wang, S.; Shan, R.; Gu, J.; Zhang, J.; Yuan, H.; Chen, Y. Pyrolysis municipal sludge char supported Fe/Ni catalysts for catalytic reforming of tar model compound. Fuel 2020, 279, 118494,  DOI: 10.1016/j.fuel.2020.118494
      29
      Pyrolysis municipal sludge char supported Fe/Ni catalysts for catalytic reforming of tar model compound
      Wang, Shuxiao; Shan, Rui; Gu, Jing; Zhang, Jun; Yuan, Haoran; Chen, Yong
      Fuel (2020), 279 (), 118494CODEN: FUELAC; ISSN:0016-2361. (Elsevier Ltd.)
      Pyrolytic char is widely used for tar removal due to its cost-effective and eco-friendly. The waste municipal sludge is selected to produce the composite catalyst with transition metal Fe/Ni, and the as-synthesized catalyst was used in the catalytic cracking of the tar model compd. toluene by a lab.-scale plant. The toluene conversion and the molar ratios of CO, H2, CO2, CH4 and C2H4 in the generated gas were studied. Municipal sludge char-based catalysts are more likely to produce H2-rich syngas (the molar ratio of syngas > 75%), and the molar ratio of H2 can reach 73.3% under optimal conditions. The Fe-Ni bimetallic catalyst combines the advantages of different metal elements to make the catalyst performance more stable. Meanwhile, the effects of residence time (τ) and steam-to-C ratio (S/C) on the conversion rate were studied. As a result, the excessive residence time or steam-to-C ratio will have no more pos. effect on the performance of the catalyst. Ultimately, the catalyst life test of 8 h was carried out, cost-effective and green waste municipal sludge char-supported Fe/Ni catalysts in this work could be used for removal of the tar heavy component toluene.
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    30. 30
      Wang, Y.; Zhang, Y.; Su, L.; Li, X.; Duan, L.; Wang, C.; Huang, T. Hazardous air pollutant formation from pyrolysis of typical Chinese casting materials. Environ. Sci. Technol. 2011, 45 (15), 6539– 6544,  DOI: 10.1021/es200310p
      30
      Hazardous Air Pollutant Formation from Pyrolysis of Typical Chinese Casting Materials
      Wang, Yujue; Zhang, Ying; Su, Lu; Li, Xiangyu; Duan, Lei; Wang, Chengwen; Huang, Tianyou
      Environmental Science & Technology (2011), 45 (15), 6539-6544CODEN: ESTHAG; ISSN:0013-936X. (American Chemical Society)
      Anal. pyrolysis was conducted to evaluate major hazardous air pollutant (HAP) emissions from pyrolysis of bituminous coal and a furan binder, the 2 most commonly used casting materials for making greensand and furan no-bake molds in Chinese foundries. These 2 materials were flash-pyrolyzed in a Curie-point pyrolyzer at 920° and slowly pyrolyzed in a thermogravimetric analyzer (TGA) from ambient temp. to 1000° at a 30°/min heating rate. Emissions from Curie-point and TGA pyrolysis were analyzed by gas chromatog./mass spectrometer with flame ionization detector. In total, 13 HAP species were identified and quantified in pyrolysis emissions of these materials. Prominent HAP emissions were cresols, benzene, toluene, phenol, and naphthalene for bituminous coal, and m-, p-, and o-xylene for the furan binder. Xylenesulfonic acid, an acidic catalyst in the furan binder, was the major xylene emission source. Thermogravimetry/mass spectrometry monitored HAP emission evolution during TGA pyrolysis. For both casting materials, most emissions were released at 350-700°.
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    31. 31
      Guo, F.; Peng, K.; Liang, S.; Jia, X.; Jiang, X.; Qian, L. Evaluation of the catalytic performance of different activated biochar catalysts for removal of tar from biomass pyrolysis. Fuel 2019, 258, 116204,  DOI: 10.1016/j.fuel.2019.116204
      31
      Evaluation of the catalytic performance of different activated biochar catalysts for removal of tar from biomass pyrolysis
      Guo, Feiqiang; Peng, Kuangye; Liang, Shuang; Jia, Xiaopeng; Jiang, Xiaochen; Qian, Lin
      Fuel (2019), 258 (), 116204CODEN: FUELAC; ISSN:0016-2361. (Elsevier Ltd.)
      Biomass derived chars via simple synthesis methods play an important role in different applications due to their porous structure, low cost and potential for the catalysis research field. This work prepd. three typical activated char catalysts using KOH, H3PO4 and ZnCl2 as activators and rice husk as precursor for the catalytic decompn. of tar from biomass pyrolysis. Results showed that high surface areas were achieved and inorg. elements were introduced by applying the activators. The char obtained by KOH activation exhibited excellent catalytic performance on tar decompn. due to the high surface area and the presence of potassium compds. Activation using H3PO4 led to a more heterogeneous pore size distribution of biochar, also exhibiting high catalytic performance, while the activation of ZnCl2 might promote the agglomeration of zinc and rice husk contg. inorg. matters, resulting in relatively lower tar conversion efficiency. The tar catalytic decompn. led to the significant increase in the yield of product gas, particularly the combustible gas components such as H2, CO and CH4. GC-MS test results showed that macromol. tar components were generally cracked and phenol was the main components of the residue tar, representing the good selectivity of the catalysts. The catalysts also showed excellent stability for tar cracking process and high catalytic performance was still achieved after five cycling tests. The biochar catalysts remained good porous structure with high surface area and the metals phases were well retained after five recycles, indicating that the biochar catalysts have the potential for long-term practical applications.
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    32. 32
      Wang, S.; Shan, R.; Lu, T.; Zhang, Y.; Yuan, H.; Chen, Y. Pyrolysis char derived from waste peat for catalytic reforming of tar model compound. Appl. Energy 2020, 263, 114565,  DOI: 10.1016/j.apenergy.2020.114565
      32
      Pyrolysis char derived from waste peat for catalytic reforming of tar model compound
      Wang, Shuxiao; Shan, Rui; Lu, Tao; Zhang, Yuyuan; Yuan, Haoran; Chen, Yong
      Applied Energy (2020), 263 (), 114565CODEN: APENDX; ISSN:0306-2619. (Elsevier Ltd.)
      The pyrolysis char derived from solid waste peat was used in the removal of biomass tar. A lab. dual-stage reactor was designed to obtain a cost-effective and eco-friendly tar removal approach using peat pyrolysis char-based catalyst. Rich pore structure of pyrolysis char can enhance the adsorption and removal performance of tar, the KOH and CO2 activation method were used to increase the pore structure of pyrolysis char. Toluene was chosen as the model compd. of biomass tar for basic research. The effects of pyrolysis char and transition metal Fe on toluene removal were studied. The investigated reforming parameters were reaction temp. (700-900°C), residence time (0.3-0.8 s) and steam-to-carbon ratio (1.5:1-4:1). The results indicated that the peat pyrolysis char-based Fe catalysts showed excellent catalytic performance (toluene conversion >89%) and gas selectivity, esp. the catalyst that activated by CO2 had the best selectivity for syngas (88.1 mol%), and the waste peat catalyst was compared with other waste pyrolysis char-based catalysts. Textural characterization showed that the excellent catalytic activity and stability of the catalysts are due to the presence of FeC and FeSiO3 structures. Such the peat pyrolysis char can as a carrier be used to remove tar and produce high content syngas in pyrolysis process.
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    33. 33
      Shi, C.; Zhang, P. Role of MgO over γ-Al2O3-supported Pd catalysts for carbon dioxide reforming of methane. Appl. Catal. B 2015, 170–171, 43– 52,  DOI: 10.1016/j.apcatb.2015.01.034
      33
      Role of MgO over γ-Al2O3-supported Pd catalysts for carbon dioxide reforming of methane
      Shi, Chunkai; Zhang, Peng
      Applied Catalysis, B: Environmental (2015), 170-171 (), 43-52CODEN: ACBEE3; ISSN:0926-3373. (Elsevier B.V.)
      A series of Pd/Al2O3 catalysts with varying Mg loading (1, 3, 7 and 10%) were investigated for carbon dioxide reforming of methane. The initial catalytic activities and long-term stabilities in terms of both CO2 and CH4 conversions increased with increasing Mg content when its loading was below 7%. When Mg content was up to 10%, the initial activity and stability decreased. Moreover, Pd7Mg/Al2O3 displayed the highest H2 and CO yields. Characterization results conducted on catalysts before and after reaction test demonstrated that MgO mainly presented in amorphous form for catalysts with additive content below 7%; while a fraction of MgO transformed into cryst. form when more additive was introduced to the catalyst. The amorphous MgO significantly enhanced surface metal dispersion, decreased av. Pd crystallite size and thus improved resistances against both metal sintering and carbon deposition, which contributed to the enhanced initial activities and long-term stabilities. On the contrary, the cryst. MgO decreased exposed Pd active sites, caused metal sintering and thus led to increased amt. of carbon deposition owing to both its neg. decoration effect on surface metal and deterioration effect on textural characteristics of support. These factors were responsible for the worse catalytic performance of Pd10Mg/Al2O3 as compared to that of Pd7Mg/Al2O3.
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    34. 34
      Zhang, J.; Chen, J.; Chen, Z.; Xiong, Q.; Di, Y.; Yin, L.; Tian, Y. A highly efficient bimetallic/biochar composite with enhanced catalytic reforming of pyrolysis tar: Performance and mechanism. Bioresour. Technol. Rep. 2022, 19, 101204,  DOI: 10.1016/j.biteb.2022.101204
      34
      A highly efficient bimetallic/biochar composite with enhanced catalytic reforming of pyrolysis tar: Performance and mechanism
      Zhang, Jun; Chen, Junjie; Chen, Zhengrui; Xiong, Qinyi; Di, Yingchen; Yin, Linlin; Tian, Yu
      Bioresource Technology Reports (2022), 19 (), 101204CODEN: BTRICJ; ISSN:2589-014X. (Elsevier Ltd.)
      In this study, a highly efficient bimetallic Ni-Fe/char composite catalyst has been synthesized successfully for catalytic cracking of pyrolysis tar and displays excellent catalytic cracking performance with tar conversion efficiency of 95.6 % (35.2 % of H2 yield). The results showed that at the steam/carbon ratio, the reaction temp. and gas residence time of 1.0, 800 °C and 0.5 s resp., the bimetallic char-supported catalysts showed outstanding catalytic performance compared with traditional catalyst, in which the N6F6/C exhibited the best activity under the same conditions. The catalytic mechanism of Ni-Fe based catalysts can be attributed to the formation of a Ni-Fe alloy. Furthermore, the synergy of Ni and Fe contributed to greater activity for toluene cracking and enhancement of fuel-gas yield. Bimetallic Ni-Fe alloy catalysts have a promising potential for application as highly efficient catalysts for tar removal and reutilization via catalytic cracking.
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    35. 35
      Liu, L.; Zhang, Z.; Das, S.; Kawi, S. Reforming of tar from biomass gasification in a hybrid catalysis-plasma system: A review. Appl. Catal. B 2019, 250, 250– 272,  DOI: 10.1016/j.apcatb.2019.03.039
      35
      Reforming of tar from biomass gasification in a hybrid catalysis-plasma system: A review
      Liu, Lina; Zhang, Zhikun; Das, Sonali; Kawi, Sibudjing
      Applied Catalysis, B: Environmental (2019), 250 (), 250-272CODEN: ACBEE3; ISSN:0926-3373. (Elsevier B.V.)
      A review. The generation of tar in biomass gasification is highly undesirable since the condensation and agglomeration of tar causes clogging and contamination of downstream equipment, leading to low energy efficiency and high maintenance cost. Currently, the most widely used methods for tar reforming are catalytic reforming and plasma reforming. However, the main drawbacks for these two processes are: (i) the rapid catalyst deactivation caused by poisoning, sintering and coke deposition for catalytic reforming, and (ii) low energy efficiency, low selectivity of syngas and the formation of undesirable byproducts for plasma reforming. Recently, therefore, the hybrid plasma-catalysis system has attracted much attention for tar reforming, since it can overcome the above-mentioned drawbacks and generate a synergy effect. The addn. of catalyst in plasma could change the discharge properties of plasma, and the plasma could also modify the catalyst property and change the status of reactants. At present, few review articles have reported and compared the performances of tar reforming in the plasma-only, catalysis-only and hybrid plasma-catalysis system. Therefore, this review paper focus on: (i) the deactivation characteristics and modification methods of steam-reforming catalysts, as well as the mechanism of tar catalytic reforming; (ii) the performance of tar reforming in various plasma reactors and the reaction mechanism based on the anal. of byproducts and energetic plasma species; and (iii) the possible synergistic effect of plasma and heterogeneous catalyst in a hybrid plasma-catalysis system caused by the multiple interactions of plasma and catalysts.
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    36. 36
      Kang, Y.; Tang, Y.; Zhu, L.; Jiang, B.; Xu, X.; Guselnikova, O.; Li, H.; Asahi, T.; Yamauchi, Y. Porous nanoarchitectures of nonprecious metal borides: from controlled synthesis to heterogeneous catalyst applications. ACS Catal. 2022, 12 (23), 14773– 14793,  DOI: 10.1021/acscatal.2c03480
      36
      Porous Nanoarchitectures of Nonprecious Metal Borides: From Controlled Synthesis to Heterogeneous Catalyst Applications
      Kang, Yunqing; Tang, Yi; Zhu, Liyang; Jiang, Bo; Xu, Xingtao; Guselnikova, Olga; Li, Hexing; Asahi, Toru; Yamauchi, Yusuke
      ACS Catalysis (2022), 12 (23), 14773-14793CODEN: ACCACS; ISSN:2155-5435. (American Chemical Society)
      A review. Porous nonprecious metal-based nanomaterials have gained considerable attention in heterogeneous catalysis owing to their low price, high sp. surface area, efficient mass/electron transfer, tunable pore structure, and unique physicochem. properties. Controlling the phase and compns. of these porous nonprecious metal-based materials is crit. to their applications. Porous nonprecious transition-metal borides (TMBs), typical metal-metalloid alloys, have recently received much interest because of their optimized electronic structure, adjustable crystal phase, and abundant active site. The controlled tuning of the porous structure of TMBs, exploring the relationship between the structure and performance, and understanding the function of B are essential for developing catalysts with excellent performance; however, these factors have rarely been reviewed. Herein, a detailed summary of the synthesis methods of porous TMBs is provided by precisely defining their shape, compn., and pore size/structure. Incorporating B into metals can significantly alter their performance due to the unique metalloid properties of B. Further, we focus on the key roles of B in porous TMBs for related heterogeneous catalytic applications, including phase control, regulated electronic structure, optimized adsorption of reaction intermediates, and enhanced charge transfer and stability. Finally, we outline the shortcomings, challenges, and possible development of porous TMBs, which need to be further explored to increase TMBs' contribution to heterogeneous catalyst applications and beyond.
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    37. 37
      Kang, Y.; Guo, Y.; Zhao, J.; Jiang, B.; Guo, J.; Tang, Y.; Li, H.; Malgras, V.; Amin, M. A.; Nara, H.; Sugahara, Y.; Yamauchi, Y.; Asahi, T. Soft template-based synthesis of mesoporous phosphorus-and boron-codoped NiFe-based alloys for efficient oxygen evolution reaction. Small 2022, 18 (33), 2203411,  DOI: 10.1002/smll.202203411
      37
      Soft Template-Based Synthesis of Mesoporous Phosphorus- and Boron-Codoped NiFe-Based Alloys for Efficient Oxygen Evolution Reaction
      Kang, Yunqing; Guo, Yanna; Zhao, Jingjing; Jiang, Bo; Guo, Jingru; Tang, Yi; Li, Hexing; Malgras, Victor; Amin, Mohammed A.; Nara, Hiroki; Sugahara, Yoshiyuki; Yamauchi, Yusuke; Asahi, Toru
      Small (2022), 18 (33), 2203411CODEN: SMALBC; ISSN:1613-6810. (Wiley-VCH Verlag GmbH & Co. KGaA)
      Controlling the morphol., compn., and cryst. phase of mesoporous nonnoble metal catalysts is essential for improving their performance. Herein, well-defined P and B-codoped NiFe alloy mesoporous nanospheres (NiFeB-P MNs) with an adjustable Ni/Fe ratio and large mesopores (11 nm) are synthesized via soft-template-based chem. redn. and a subsequent phosphine-vapor-based phosphidation process. Earth-abundant NiFe-based materials are considered promising electrocatalysts for the oxygen evolution reaction (OER) because of their low cost and high intrinsic catalytic activity. The resulting NiFeB-P MNs exhibit a low OER overpotential of 252 mV at 10 mA cm-2, which is significantly smaller than that of B-doped NiFe MNs (274 mV) and com. RuO2 (269 mV) in alk. electrolytes. Thus, this work highlights the practicality of designing mesoporous nonnoble metal structures and the importance of incorporating P in metallic-B-based alloys to modify their electronic structure for enhancing their intrinsic activity.
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      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB38XhvFaru7zJ&md5=8e1ad336d97391ed0a92aa1a5da46ada
    38. 38
      Santamaria, L.; Lopez, G.; Arregi, A.; Amutio, M.; Artetxe, M.; Bilbao, J.; Olazar, M. Influence of the support on Ni catalysts performance in the in-line steam reforming of biomass fast pyrolysis derived volatiles. Appl. Catal. B 2018, 229, 105– 113,  DOI: 10.1016/j.apcatb.2018.02.003
      38
      Influence of the support on Ni catalysts performance in the in-line steam reforming of biomass fast pyrolysis derived volatiles
      Santamaria, Laura; Lopez, Gartzen; Arregi, Aitor; Amutio, Maider; Artetxe, Maite; Bilbao, Javier; Olazar, Martin
      Applied Catalysis, B: Environmental (2018), 229 (), 105-113CODEN: ACBEE3; ISSN:0926-3373. (Elsevier B.V.)
      The influence the support has on the performance of Ni catalysts used in the reforming of biomass fast pyrolysis volatiles has been assessed. Accordingly, five catalysts have been prepd. by wet impregnation method, namely Ni/Al2O3, Ni/SiO2, Ni/MgO, Ni/TiO2 and Ni/ZrO2. These catalysts have been characterized by nitrogen adsorption/desorption, X-ray fluorescence spectroscopy, temp. programmed redn. and X-ray diffraction techniques. The pyrolysis-reforming runs have been performed in a bench scale unit operating in continuous regime. The biomass (pine wood sawdust) pyrolysis step has been carried out in a conical spouted bed reactor at 500°C, with the volatiles produced (a mixt. of gases and bio-oil) being reformed in-line on the prepd. catalysts in a fluidized bed reactor at 600°C. Remarkable differences have been obsd. amongst the catalyst prepd., with Ni/Al2O3, Ni/MgO and Ni/ZrO2 being those leading to the most encouraging results, whereas Ni/TiO2 and, esp. Ni/SiO2, having a limited reforming activity. The performance of each catalyst has been related to its properties detd. in the characterization.
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    39. 39
      Fang, S.; Cui, Z.; Zhu, Y.; Wang, C.; Bai, J.; Zhang, X.; Xu, Y.; Liu, Q.; Chen, L.; Zhang, Q.; Ma, L. In situ synthesis of biomass-derived Ni/C catalyst by self-reduction for the hydrogenation of levulinic acid to γ-valerolactone. J. Energy Chem. 2019, 37, 204– 214,  DOI: 10.1016/j.jechem.2019.03.021
      There is no corresponding record for this reference.
    40. 40
      Li, Y.; Men, Y.; Liu, S.; Wang, J.; Wang, K.; Tang, Y.; An, W.; Pan, X.; Li, L. Remarkably efficient and stable Ni/Y2O3 catalysts for CO2 methanation: Effect of citric acid addition. Appl. Catal. B 2021, 293, 120206,  DOI: 10.1016/j.apcatb.2021.120206
      40
      Remarkably efficient and stable Ni/Y2O3 catalysts for CO2 methanation: Effect of citric acid addition
      Li, Yingying; Men, Yong; Liu, Shuang; Wang, Jinguo; Wang, Kang; Tang, Yuhan; An, Wei; Pan, Xiaoli; Li, Lin
      Applied Catalysis, B: Environmental (2021), 293 (), 120206CODEN: ACBEE3; ISSN:0926-3373. (Elsevier B.V.)
      Citric acid has been investigated for prepg. the highly dispersed nickel catalysts on Y2O3 support. A highly enhanced methanation activity with the high CO2 conversion of 92% and CH4 selectivity of 100% was obtained over Ni/Y2O3 with optimum addn. of citric acid at 350°C. The citric acid additives during the prepn. are found to influence the size of nickel nanoparticles and the interaction of metal and support, as estd. by various techniques, which, in turn, to correlated with the catalytic performance. In situ DRIFTS spectra further indicate the importance of small Ni particles on formation of carbonates and formate species as key intermediates and the subsequent hydrogenation of those species into methane. This study proposes that the Y-O-Ni interfacial structure formed by the strong Ni and Y2O3 interaction at high citric acid addn. is of prime importance for the formation of methane, benefiting from the more abundant basic sites and metallic Ni to enable CO2 activation and hydrogenation of key intermediates by effective H2 dissocn. resp. This work provides a new design strategy for developing highly efficient composite CO2 methanation catalysts by control of the metal particle size and charge transfer via metal/support interface.
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    41. 41
      Jin, H.; Yu, R.; Hu, C.; Ji, P.; Ma, Q.; Liu, B.; He, D.; Mu, S. Size-controlled engineering of cobalt metal catalysts through a coordination effect for oxygen electro catalysis. Appl. Catal. B 2022, 317, 121766,  DOI: 10.1016/j.apcatb.2022.121766
      41
      Size-controlled engineering of cobalt metal catalysts through a coordination effect for oxygen electrocatalysis
      Jin, Huihui; Yu, Ruohan; Hu, Chenxi; Ji, Pengxia; Ma, Qianli; Liu, Bingshuai; He, Daping; Mu, Shichun
      Applied Catalysis, B: Environmental (2022), 317 (), 121766CODEN: ACBEE3; ISSN:0926-3373. (Elsevier B.V.)
      In the prepn. process of carbon-based transition metal catalysts, the transition metal atoms usually seriously agglomerate, thus reducing the catalytic activity. To slow down the agglomeration of transition metal atoms during high-temp. treatments, herein, orgs. with coordination functions are proposed to regulate the typical metal-org. framework compd. ZIF-67 with rich Co atoms. Electron microscopy structural characterization proves that ZIF-67 modified by coordinated org. compds., including ascorbic acid (AA), citric acid (CA) and EDTA disodium salt (EA), greatly improves the dispersibility of cobalt in the final product. All the adjusted ZIF-67 can derive cobalt-based bifunctional oxygen catalysts with higher activity. Among them, EA-MOF-Co shows the best ORR performance, with a half-wave potential comparable to com. Pt/C in alk. solns. and an obviously reduced oxygen evolution overpotential. This suggests that it is an effective method for use of coordination orgs. to tether metal ions and prevent their further agglomeration during carbonation.
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    42. 42
      Meng, J.; Zhao, Z.; Wang, X.; Zheng, A.; Zhang, D.; Huang, Z.; Zhao, K.; Wei, G.; Li, H. Comparative study on phenol and naphthalene steam reforming over Ni-Fe alloy catalysts supported on olivine synthesized by different methods. Energy Convers. Manage. 2018, 168, 60– 73,  DOI: 10.1016/j.enconman.2018.04.112
      42
      Comparative study on phenol and naphthalene steam reforming over Ni-Fe alloy catalysts supported on olivine synthesized by different methods
      Meng, Junguang; Zhao, Zengli; Wang, Xiaobo; Zheng, Anqing; Zhang, Dongyan; Huang, Zhen; Zhao, Kun; Wei, Guoqiang; Li, Haibin
      Energy Conversion and Management (2018), 168 (), 60-73CODEN: ECMADL; ISSN:0196-8904. (Elsevier Ltd.)
      Ni/Fe bimetallic catalysts were synthesized on an olivine support using the wetness impregnation (WI) and thermal fusion (TF) methods, and catalytic cracking and steam reforming on different tar model compds. (phenol and naphthalene) were investigated in a fixed bed reactor. The effects of the reaction temp. and space-time on the catalytic cracking activity of phenol and naphthalene were tested, and the influences of steam on the carbon molar ratio (S/C) and different synthesized methods on the steam reforming of phenol and naphthalene were also studied. In addn., the carbon deposited on the catalyst was analyzed using temp. program oxidn. (TPO), Raman spectroscopy and transmission electron microscopy (TEM) methods. The elemental compn. of the catalyst was analyzed by X-ray fluorescence (XRF), and the physiochem. properties of the catalysts were characterized via X-ray diffraction (XRD), the BET surface area, SEM (SEM), TEM, Raman spectroscopy, temp. program redn. (TPR), and XPS. The results showed that the structure of TF-Ni/Fe/olivine changed considerably compared with that of calcined olivine (mainly the Mg2SiO4 phase) and that a portion of Fe was fused into the olivine structure and reorganized into a new (Mg, Fe) Fe2O4 phase. After redn., the Ni-Fe alloy was detected on both catalysts, and the particle size of the Ni-Fe alloy on TF-Ni/Fe/olivine was smaller than that of WI-Ni/Fe/olivine. The TF-Ni/Fe/olivine cracked phenol into small-mol. gas (CO and H2) and a small quantity of olefin. By contrast, phenol was polymd. to naphthalene in the absence of a catalyst. The phenol and naphthalene steam reforming conversion on WI-Ni/Fe/olivine were both higher than that of TF-Ni/Fe/olivine. A 100-h stability test of phenol steam reforming on TF-Ni/Fe/olivine and WI-Ni/Fe/olivine was conducted, and TF-Ni/Fe/olivine showed higher stability in the early stages of the expt. due to stronger interactions between the active sites and olivine support. The deposited carbon from naphthalene steam reforming was more difficult to eliminate because it contained more Cβ and Cγ, which had higher degrees of graphitization.
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    43. 43
      Santamaria, L.; Lopez, G.; Arregi, A.; Artetxe, M.; Amutio, M.; Bilbao, J.; Olazar, M. Catalytic steam reforming of biomass fast pyrolysis volatiles over Ni–Co bimetallic catalysts. J. Ind. Eng. Chem. 2020, 91, 167– 181,  DOI: 10.1016/j.jiec.2020.07.050
      43
      Catalytic steam reforming of biomass fast pyrolysis volatiles over Ni-Co bimetallic catalysts
      Santamaria, Laura; Lopez, Gartzen; Arregi, Aitor; Artetxe, Maite; Amutio, Maider; Bilbao, Javier; Olazar, Martin
      Journal of Industrial and Engineering Chemistry (Amsterdam, Netherlands) (2020), 91 (), 167-181CODEN: JIECFI; ISSN:1226-086X. (Elsevier B.V.)
      The influence of the metal selected as catalytic active phase in the two-step biomass pyrolysis-catalytic reforming strategy has been analyzed. The pyrolysis step was carried out in a conical spouted bed reactor at 500 °C, whereas steam reforming was performed in a fluidized bed reactor at 600 °C. Ni/Al2O3, Co/Al2O3 and two bimetallic Ni-Co/Al2O3 catalysts with different metal loadings were synthesized by wet impregnation method, and fresh and deactivated catalysts were characterized by N2 adsorption/desorption, X-ray Fluorescence (XRF), Temp. Programmed Redn. (TPR), X-Ray powder Diffraction (XRD), Temp. Programmed Oxidn. (TPO), SEM (SEM) and Transmission Electron Microscopy (TEM). Although Ni/Al2O3 and both bimetallic catalysts had similar initial activity in terms of oxygenate conversion, (higher than 98%), the poorer metal dispersion obsd. in both bimetallic catalysts led to a fast decrease in conversion due to the promotion of coke formation on large particles. This occurred even though Ni-Co alloy formation has a pos. influence by hindering the oxidn. of Co0 species. The poor initial performance of Co/Al2O3 catalyst is related to changes in the Co0 oxidn. state induced by the presence of steam, which led to a fast deactivation of this catalyst.
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    44. 44
      Moyer, M. M.; Karakaya, C.; Kee, R. J.; Trewyn, B. G. In-Situ Formation of Metal Carbide Catalysts. ChemCatchem 2017, 9 (16), 3090– 3101,  DOI: 10.1002/cctc.201700304
      44
      In Situ Formation of Metal Carbide Catalysts
      Moyer, Megan M.; Karakaya, Canan; Kee, Robert J.; Trewyn, Brian G.
      ChemCatChem (2017), 9 (16), 3090-3101CODEN: CHEMK3; ISSN:1867-3880. (Wiley-VCH Verlag GmbH & Co. KGaA)
      A review; metal carbide catalysts are essential to many widely used chem. processes. Fischer-Tropsch synthesis, methane dehydroaromatization and biomass conversion catalysts are typically prepd. in situ from a metal oxide precursor with a carbon-contg. gas. The redn. process of the metal oxide affects the final catalyst, as does the carburization gas mixt. and metal promoters. By looking at materials that are carburized in situ, new insights can be gained about catalyst activation, fuel processing, and deactivation stages. The main focuses of this Review are iron carbide, molybdenum carbide and nickel carbide; analyzing catalyst synthesis methods, redn. steps, in situ carburization and improvements to the native processes. By combining years of research on these catalysts, trends and similarities are obsd. that can be used to improve current catalytic studies.
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    45. 45
      Shen, Y.; Zhao, P.; Shao, Q.; Ma, D.; Takahashi, F.; Yoshikawa, K. In-situ catalytic conversion of tar using rice husk char-supported nickel-iron catalysts for biomass pyrolysis/gasification. Appl. Catal. B 2014, 152–153, 140– 151,  DOI: 10.1016/j.apcatb.2014.01.032
      45
      In-situ catalytic conversion of tar using rice husk char-supported nickel-iron catalysts for biomass pyrolysis/gasification
      Shen, Yafei; Zhao, Peitao; Shao, Qinfu; Ma, Dachao; Takahashi, Fumitake; Yoshikawa, Kunio
      Applied Catalysis, B: Environmental (2014), 152-153 (), 140-151CODEN: ACBEE3; ISSN:0926-3373. (Elsevier B.V.)
      This paper aims to propose an effective tar conversion approach during biomass pyrolysis via in-situ dry reforming over rice husk (RH) char and char-supported Ni-Fe catalysts. Using high pyrolysis temp., tar from biomass pyrolysis could be removed effectively in the gasifier by mixing with the char-supported catalysts, simplifying the follow-up tar removal process. Under the optimized conditions, the conversion efficiencies of condensable tar can reach ∼92.3% and 93% using Ni-Fe char (without calcination) and Ni char (with calcination), resp. It is noteworthy that the condensable tar could be catalytically transformed into the noncondensable tar or small mol. gases resulting in the heating value increase of gaseous products to benefit of the power generation systems. Compared with the other catalysts prepn. methods, Ni-Fe char exhibited more advantages of convenient and energy-saving. In the presence of catalysts, the concn. of CO2 (vol.%) was reduced slightly, while the CO concn. (vol.%) increased greatly because of dry reforming. Due to C loss, parts of RH char-supported catalysts (C-SiO2 catalysts) could be converted into SiO2-based catalysts because of high-content amorphous nano-sized SiO2 in RH char. Partial metal oxides or ions via C (i.e., biochar) and gas (i.e., H2, CO) in-situ redn. were transformed into metallic states contributing to the enhancement of tar conversion. Therefore, RH char plays two significant roles during the process of biomass pyrolysis. On one hand, it works as an intermediate reductant to reduce the metal oxides and CO2; however, it can be considered as an adsorptive-support to adsorb metal ions and tar. After that, the char-supported catalysts could be used for tar conversion. In particular, since the metal catalysts still remain in the solid residues, the pyrolysis char could be regenerated via thermal regeneration using waste heat or gasified into syngas directly.
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    46. 46
      Gai, C.; Zhang, F.; Yang, T.; Liu, Z.; Jiao, W.; Peng, N.; Liu, T.; Lang, Q.; Xia, Y. Hydrochar supported bimetallic Ni–Fe nanocatalysts with tailored composition, size and shape for improved biomass steam reforming performance. Green Chem. 2018, 20 (12), 2788– 2800,  DOI: 10.1039/C8GC00433A
      46
      Hydrochar supported bimetallic Ni-Fe nanocatalysts with tailored composition, size and shape for improved biomass steam reforming performance
      Gai, Chao; Zhang, Fang; Yang, Tianxue; Liu, Zhengang; Jiao, Wentao; Peng, Nana; Liu, Tingting; Lang, Qianqian; Xia, Yu
      Green Chemistry (2018), 20 (12), 2788-2800CODEN: GRCHFJ; ISSN:1463-9262. (Royal Society of Chemistry)
      Multicomponent nickel-iron alloy nanoparticles supported on hydrochar were synthesized by a facile one-step hydrothermal strategy. Spinel nickel ferrite (NiFe2O4) with a small cryst. size around 10 nm was uniformly dispersed on a bimetallic catalyst. The roles of the Ni/Fe doping concn. and calcination temp. in tailoring the phase, morphol. and size of the Ni-Fe alloy nanoparticles were investigated. To probe the catalytic abilities of the prepd. bimetallic catalysts, a two-stage reaction system was applied for steam gasification of sewage sludge. Compared to monometallic nickel nanoparticles, the synthesized bimetallic catalyst, esp. Ni0.25Fe0.25/HC calcined at 700 °C, showed excellent dispersibility of the Ni-Fe alloy NPs and exhibited a strong metal-support interaction, which allowed for better suppression of carbon deposition and nanoparticle agglomeration in the reforming process. The best catalytic performance resulted in a promoted hydrogen selectivity of 113.7 g H2 per kg sludge with a low tar yield of 2.3 mg g-1 under mild gasification conditions. These shape- and size-modulated nanocatalysts harbor promising potential for their application as a highly efficient catalyst for hydrogen prodn. via steam gasification of sewage sludge.
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    47. 47
      Nabgan, W.; Tuan Abdullah, T. A.; Mat, R.; Nabgan, B.; Gambo, Y.; Triwahyono, S. Influence of Ni to Co ratio supported on ZrO2 catalysts in phenol steam reforming for hydrogen production. Int. J. Hydrogen. Energy 2016, 41 (48), 22922– 22931,  DOI: 10.1016/j.ijhydene.2016.10.055
      47
      Influence of Ni to Co ratio supported on ZrO2 catalysts in phenol steam reforming for hydrogen production
      Nabgan, Walid; Tuan Abdullah, Tuan Amran; Mat, Ramli; Nabgan, Bahador; Gambo, Yahya; Triwahyono, Sugeng
      International Journal of Hydrogen Energy (2016), 41 (48), 22922-22931CODEN: IJHEDX; ISSN:0360-3199. (Elsevier Ltd.)
      In this work, catalytic steam reforming of phenol for hydrogen prodn. was investigated. This study focuses on the effects of Ni to Co ratio supported on ZrO2 catalysts. The NixCoy/ZrO2 (x = 0, 1, 2, 3, 4 where x + y = 4) catalysts were prepd. by impregnation method. Steam reforming activity was tested in a fixed bed reactor at 600 °C using a feed of phenol/water mixt. at a molar ratio of 1:9 and a const. liq. feed rate of 0.36 mL/min. The catalysts were characterized by BET surface area, X-ray diffraction (XRD), transmission electron microscopy (TEM), NH3 Temp.-Programmed Desorption (NH3-TPD), CO2 Temp.-Programmed Desorption (CO2-TPD), H2 Temp.-Programmed Redn. (H2-TPR) and thermo-gravimetric anal. (TGA). The increase in the Co content from 0 to 4, caused a decrease in the crystal size, the t-ZrO2 phase and the reducibility of the catalysts. However, it only slightly affected the total surface area. It was found that metallic Ni4 and Co4 catalysts have lower activity towards phenol steam reforming and deposit higher coke due to having higher acidity sites compare to bimetallic catalysts. In contrast, Ni3Co1 displayed a superior catalytic activity among all the catalysts, suggesting the presence of the highest basic site and high coking resistance. Phenol conversion of 53.5% and hydrogen yield of 50.4% were achieved with the Ni3Co1 catalyst, even though its activity decreased by increasing the cobalt content.
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    48. 48
      Yang, F.-L.; Cao, J.-P.; Zhao, X.-Y.; Ren, J.; Tang, W.; Huang, X.; Feng, X.-B.; Zhao, M.; Cui, X.; Wei, X.-Y. Acid washed lignite char supported bimetallic Ni-Co catalyst for low temperature catalytic reforming of corncob derived volatiles. Energy Convers. Manage. 2019, 196, 1257– 1266,  DOI: 10.1016/j.enconman.2019.06.075
      48
      Acid washed lignite char supported bimetallic Ni-Co catalyst for low temperature catalytic reforming of corncob derived volatiles
      Yang, Fei-Long; Cao, Jing-Pei; Zhao, Xiao-Yan; Ren, Jie; Tang, Wen; Huang, Xin; Feng, Xiao-Bo; Zhao, Ming; Cui, Xin; Wei, Xian-Yong
      Energy Conversion and Management (2019), 196 (), 1257-1266CODEN: ECMADL; ISSN:0196-8904. (Elsevier Ltd.)
      Acid washed Shengli lignite (AWSL) supported Ni, Co and Ni-Co catalysts were prepd., characterized and evaluated in catalytic reforming (CR) of corncob pyrolysis volatiles at a relatively low catalytic temp. of 450°C. Moreover, the prodn. and selectivity of H2 were also investigated. Amongst the catalysts studied, bimetallic Ni-10%Co/AWSL exhibited the most remarkable activity, yielding 36.3 mmol H2/g corncob and 710μmol min-1 g-1 formation rate of syngas (H2 + CO + 4CH4) with trace of tar. It also tuned the gas compn. and showed the greatest selectivity of H2 due to the promotion of the water gas shift reaction (with H2 accounting for the max. 50.3% and 63% under Ar and steam atm., resp.). Regardless of the loss of sp. surface area, the superior performance of Ni-Co based catalysts under mild circumstance was attributed to the better reducibility and electronic properties along with a high dispersion of active metal. Addnl., the synergy of Ni and Co contributed to the combined and enlarged activity for CR of corncob volatiles and great selectivity for H2-rich syngas under moderate condition.
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    49. 49
      Wu, Y.-L.; Yang, R.-R.; Yang, G.-P.; Yan, Y.-T.; Su, X.-L.; He, X.-H.; Song, Y.-Y.; Ma, Z.-S.; Wang, Y.-Y. A new porous Co(ii)-metal–organic framework for high sorption selectivity and affinity to CO2 and efficient catalytic oxidation of benzyl alcohols to benzaldehydes. CrystEngcomm 2021, 23 (20), 3717– 3723,  DOI: 10.1039/D1CE00250C
      49
      A new porous Co(II)-metal-organic framework for high sorption selectivity and affinity to CO2 and efficient catalytic oxidation of benzyl alcohols to benzaldehydes
      Wu, Yun-Long; Yang, Rong-Rong; Yang, Guo-Ping; Yan, Yang-Tian; Su, Xiao-Lei; He, Xin-Hai; Song, Yan-Yan; Ma, Zheng-Sheng; Wang, Yao-Yu
      CrystEngComm (2021), 23 (20), 3717-3723CODEN: CRECF4; ISSN:1466-8033. (Royal Society of Chemistry)
      Herein, we report a new 3D porous Co(II)-based metal-org. framework catalyst (Me2NH2)2[Co3(L)2(H2O)2]·2DMF (MOF I), which has been successfully prepd. by using Co(II) ions and rigid V-shaped 3,5-di(2,4-dicarboxylphenyl)pyridine (H4L) via the solvothermal reaction. Structural anal. reveals that I displays a porous structure with the pore size of 16.2 x 7.2 Å2 based on the trinuclear [Co3(COO)4(H2O)2N2] secondary building units (SBUs). Gas sorption expts. on the guest free sample I' reveals a high capacity and selectivity to CO2 over CH4. And further, the catalytic explorations of the I'-catalyzed system (I': 3 mol%; proline: 40 mol%; CH3CN: 2 mL) reveal that benzyl alcs. with different structures can be efficiently transformed into benzyl alcs. without byproducts under mild conditions.
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    50. 50
      Ashok, J.; Dewangan, N.; Das, S.; Hongmanorom, P.; Wai, M. H.; Tomishige, K.; Kawi, S. Recent progress in the development of catalysts for steam reforming of biomass tar model reaction. Fuel Process. Technol. 2020, 199, 106252,  DOI: 10.1016/j.fuproc.2019.106252
      50
      Recent progress in the development of catalysts for steam reforming of biomass tar model reaction
      Ashok, Jangam; Dewangan, Nikita; Das, Sonali; Hongmanorom, Plaifa; Wai, Ming Hui; Tomishige, Keiichi; Kawi, Sibudjing
      Fuel Processing Technology (2020), 199 (), 106252CODEN: FPTEDY; ISSN:0378-3820. (Elsevier Ltd.)
      This review describes recent advances in development of catalysts for steam reforming of biomass tar model reactions, using toluene, benzene and naphthalene as tar model compds. Catalytic systems have been categorized based on their catalytic properties. The material properties such as oxygen mobility and basicity of catalysts showed great influence in their effectiveness in tar reforming. Changes in the properties such as oxygen mobility and basicity with various metal and/or support modifications and their influence on catalytic behavior with respect to reactant conversion and coke inhibition is comprehensively discussed. The activity of the catalysts derived from various synthesis methods is also introduced. The changes induced in the pathways of steam reforming reactions by catalyst modification is also highlighted together with changes in catalytic properties. Reaction pathways for steam reforming of toluene by exptl. studies together with insights gained from computational DFT studies is also presented.
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    51. 51
      Aramouni, N. A. K.; Touma, J. G.; Tarboush, B. A.; Zeaiter, J.; Ahmad, M. N. Catalyst design for dry reforming of methane: Analysis review. Renewable Sustainable Energy Rev. 2018, 82, 2570– 2585,  DOI: 10.1016/j.rser.2017.09.076
      51
      Catalyst design for dry reforming of methane: Analysis review
      Aramouni, Nicolas Abdel Karim; Touma, Jad G.; Abu Tarboush, Belal; Zeaiter, Joseph; Ahmad, Mohammad N.
      Renewable & Sustainable Energy Reviews (2018), 82 (Part_3), 2570-2585CODEN: RSERFH; ISSN:1364-0321. (Elsevier Ltd.)
      A review. The performance of catalysts used for the dry reforming of methane can strongly depend on the selection of active metals, supports and promoters. This work studies their effects on the activity and stability of selected catalysts. Designing an economically viable catalyst that maintains high catalytic activity and stability can be achieved by exploiting the synergic effects of combining noble and/or non-noble metals to form highly active and stable bi- and tri-metallic catalysts. Perovskite type catalysts can also constitute a potent and cost effective substituent. Metal oxide supports with surface Lewis base sites are able to reduce carbon formation and yield a greater stability to the catalyst, while noble metal promoters have proven to increase both catalyst activity and stability. Moreover, a successful metal-support-promoter combination should lead to higher metal-support interacrtion, lower redn. temp. and enhancement of the anti-coking and anti-amalgamation properties of the catalyst. However, the effect of each parameter on the overall performance of the catalyst is usually complex, and the catalyst designer is often faced with a tradeoff between activity, stability and ease of activation. Based on the review carried out on various studies, it is concluded that a catalyst design must take into consideration not only the sep. effects of the active metal, support and promoter, but should also include the combined and mutual interactions of these components.
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    52. 52
      Xu, J.; Holthaus, P.; Yang, N.; Jiang, S.; Heupel, A.; Schönherr, H.; Yang, B.; Krumm, W.; Jiang, X. Catalytic tar removal using TiO2/NiWO4-Ni5TiO7 films. Appl. Catal. B 2019, 249, 155– 162,  DOI: 10.1016/j.apcatb.2019.03.006
      52
      Catalytic tar removal using TiO2/NiWO4-Ni5TiO7 films
      Xu, Jing; Holthaus, Philip; Yang, Nianjun; Jiang, Siyu; Heupel, Alwin; Schoenherr, Holger; Yang, Bing; Krumm, Wolfgang; Jiang, Xin
      Applied Catalysis, B: Environmental (2019), 249 (), 155-162CODEN: ACBEE3; ISSN:0926-3373. (Elsevier B.V.)
      One-dimensional Ni catalysts are more promising than Ni powders for catalytic tar removal from biomass gasification, originating from their unique morphologies and higher sp. surfaces. Herein, the authors demonstrate the application of a Ti supported multilayer system, a TiO2/NiWO4-Ni5TiO7 film, for catalytic tar removal. This film is synthesized via plasma electrolytic oxidn. (PEO) combined with subsequent impregnation and annealing. The surface morphol. and the size of as-synthesized Ni5TiO7 nanowires are detd. mainly by used electrolytes during PEO processes. For catalytic tar removal, a fixed bed reactor is used and naphthalene is chosen as a model tar. This TiO2/NiWO4-Ni5TiO7 film exhibits higher efficiency than thermal cracking as well as long-term stability towards catalytic steam reformation of naphthalene. A naphthalene conversion rate of 63% is achieved at 800° with a short residence time of 0.34 s and a high tar load of 75 g m-3N. Such a TiO2-NiWO4/Ni5TiO7 film is thus promising for future tar removal from biomass gasification in the industry.
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    53. 53
      Lee, Y.-L.; Kim, K.-J.; Hong, G.-R.; Roh, H.-S. Target-oriented water–gas shift reactions with customized reaction conditions and catalysts. Chem. Eng. J. 2023, 458, 141422,  DOI: 10.1016/j.cej.2023.141422
      53
      Target-oriented water-gas shift reactions with customized reaction conditions and catalysts
      Lee, Yeol-Lim; Kim, Kyoung-Jin; Hong, Ga-Ram; Roh, Hyun-Seog
      Chemical Engineering Journal (Amsterdam, Netherlands) (2023), 458 (), 141422CODEN: CMEJAJ; ISSN:1385-8947. (Elsevier B.V.)
      A review. The conventional hydrogen prodn. process from natural gas includes a water-gas shift reaction (WGSR) as a core step to remove carbon monoxide and produce addnl. hydrogen. The WGSR can be further applied to the upcycling of other types of synthesis gases, such as biomass, municipal solid waste, and coal-derived synthesis gas. We have focused on the reaction conditions and catalysts for the WGSR dealing with diverse types of feed gases for the last 10 years to understand the development progress. Based on the categorization (by the type of feed gas), the tested catalysts, capacity, temp., feed gas compn., steam-to-carbon ratio, and the performance of the catalyst are carefully compared. This review provides insight into the current research trends and perspectives for target-oriented WGSR in each type of feed gas, which can give clues for customization.
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    54. 54
      Bimbela, F.; Ábrego, J.; Puerta, R.; García, L.; Arauzo, J. Catalytic steam reforming of the aqueous fraction of bio-oil using Ni-Ce/Mg-Al catalysts. Appl. Catal. B 2017, 209, 346– 357,  DOI: 10.1016/j.apcatb.2017.03.009
      54
      Catalytic steam reforming of the aqueous fraction of bio-oil using Ni-Ce/Mg-Al catalysts
      Bimbela, F.; Abrego, J.; Puerta, R.; Garcia, L.; Arauzo, J.
      Applied Catalysis, B: Environmental (2017), 209 (), 346-357CODEN: ACBEE3; ISSN:0926-3373. (Elsevier B.V.)
      The performance of different Ni/Mg-Al catalysts modified with Ce was evaluated in the catalytic steam reforming of aq. fractions of bio-oil from biomass pyrolysis. The effects of several prepn. methods for incorporating Ce as a modifier (co-pptn., impregnation and direct thermal decompn. of the salt precursors), the Ce content (0-5%) and the feed streams (3 different aq. fractions from bio-oil) on the catalyst performance were examd., and the stability and activity of the catalysts were significantly influenced by all these factors. In general, the addn. of Ce to a ref. Ni/Mg-Al catalyst improved the overall C conversion to gas and the yield to H2 as well as enhancing the catalyst stability in the steam reforming of aq. fractions of bio-oils. The best prepn. method was impregnation and the optimal Ce content is 0.5%. Much higher initial C conversion to gas and initial H2 yields was obtained using bio-oils derived from pine than those derived from poplar. A very low coke formation, 103 mg C/(g of catalyst·g of orgs. in the aq. fraction reacted), was achieved using the optimized catalyst, 0.5% Ce prepd. by impregnation.
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    55. 55
      Huang, Z.; Deng, Z.; Feng, Y.; Chen, T.; Chen, D.; Zheng, A.; Wei, G.; He, F.; Zhao, Z.; Wu, J.; Li, H. Exploring the Conversion Mechanisms of Toluene as a Biomass Tar Model Compound on NiFe2O4 Oxygen Carrier. ACS Sustainable Chem. Eng. 2019, 7 (19), 16539– 16548,  DOI: 10.1021/acssuschemeng.9b03831
      55
      Exploring the Conversion Mechanisms of Toluene as a Biomass Tar Model Compound on NiFe2O4 Oxygen Carrier
      Huang, Zhen; Deng, Zhengbing; Feng, Yuheng; Chen, Tianju; Chen, Dezhen; Zheng, Anqing; Wei, Guoqiang; He, Fang; Zhao, Zengli; Wu, Jinhu; Li, Haibin
      ACS Sustainable Chemistry & Engineering (2019), 7 (19), 16539-16548CODEN: ASCECG; ISSN:2168-0485. (American Chemical Society)
      As a novel biomass gasification technol., chem. looping gasification (CLG) could in situ catalytically crack biomass tar by oxygen carrier (OC). This study compares the reactivity of different OCs (Al2O3, Fe2O3, NiO, NiO+Fe2O3, and NiFe2O4) to crack a biomass tar model compd. (toluene) and preliminarily explores the reaction mechanisms of toluene cracked by NiFe2O4 OC. Among five OCs, NiFe2O4 with a homogeneous Fe/Ni dispersibility shows the best reactivity for toluene cracking with a toluene conversion and H2 yield of 96.83% and 0.91 L/g, resp. Addnl., on the basis of the dispersibility of active sites on the OC sample surface, the reactivity of the other four OCs to crack toluene shows the sequence NiO+Fe2O3 > Fe2O3 > NiO » Al2O3. A large amt. of carbon deposition, including amorphous carbon and graphitized carbon, is generated during toluene catalytic cracking, while the addn. of steam significantly eliminates the carbon deposition. The NiFe2O4 OC shows a dual-function of in situ oxidn.-catalysis during toluene cracking. A mechanism of four steps is proposed for the toluene cracking on OCs: (I) toluene cracking at high temp., (II) redn. of OC, (III) generation of amorphous carbon deposition and (III') formation of graphitized carbon, and (IV) elimination of carbon deposition. The oxygen carrier NiFe2O4 exhibits in situ oxidn.-catalysis for tar cracking, which efficiently decomps. biomass tar into small-mol. gases.
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    56. 56
      Xie, Y.; Su, Y.; Wang, P.; Zhang, S.; Xiong, Y. In-situ catalytic conversion of tar from biomass gasification over carbon nanofibers- supported Fe-Ni bimetallic catalysts. Fuel Process. Technol. 2018, 182, 77– 87,  DOI: 10.1016/j.fuproc.2018.10.019
      56
      In-situ catalytic conversion of tar from biomass gasification over carbon nanofibers- supported Fe-Ni bimetallic catalysts
      Xie, Yinhang; Su, Yinhai; Wang, Peng; Zhang, Shuping; Xiong, Yuanquan
      Fuel Processing Technology (2018), 182 (), 77-87CODEN: FPTEDY; ISSN:0378-3820. (Elsevier Ltd.)
      Using catalytic conversion to reduce the formation of tar in biomass gasification has received great attention, and catalyst improvement is one of the key issues. In this work, Fe-Ni/carbon nanofibers composite materials were prepd. and used for tar conversion during biomass gasification. Compared with non-catalyst tar conversion, the tar removal efficiency reached 85.76% and the total syngas yield doubled (0.947 L/g) with Fe-Ni/carbon nanofibers catalyst. After 13-time reuse, the tar removal efficiency and syngas yield only decreased by 7.25% and 9.07%, resp. Due to the formation of carbon nanofibers through calcination, a high mesopore vol. of catalyst was achieved which is beneficial to the adsorption and cracking of macromol. tar components. And the Fe0.64Ni0.36 alloy detected in Fe-Ni/carbon nanofibers catalyst has a quite high catalytic ability to arom. compds. Furthermore, the carbon deposition of catalyst can be relieved by the interaction between Fe and Ni, which can effectively maintain the catalytic performance of catalysts. The combination of bimetallic catalyst with carbon nanofibers allows the high catalytic activity and stable cyclability of Fe-Ni/CNF for effective tar conversion.
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    57. 57
      Huang, S.; Xu, H.; Li, H.; Guo, Y.; Sun, Z.; Du, Y.; Li, H.; Zhang, J.; Pang, R.; Dong, Q.; Zhang, S. Preparation and characterization of char supported Ni-Cu nanoalloy catalyst for biomass tar cracking together with syngas-rich gas production. Fuel Process. Technol. 2021, 218, 106858,  DOI: 10.1016/j.fuproc.2021.106858
      57
      Preparation and characterization of char supported Ni-Cu nanoalloy catalyst for biomass tar cracking together with syngas-rich gas production
      Huang, Sisi; Xu, Hailiang; Li, Hongyan; Guo, Yifeng; Sun, Zhenjie; Du, Yang; Li, Huaju; Zhang, Jinfeng; Pang, Renze; Dong, Qing; Zhang, Shuping
      Fuel Processing Technology (2021), 218 (), 106858CODEN: FPTEDY; ISSN:0378-3820. (Elsevier Ltd.)
      In order to realize the efficient biomass tar cracking into syngas-rich gases, several Aspen wood char (ASC) supported metal catalysts, including the Ni/ASC, Cu/ASC and bimetallic Ni-Cu/ASC catalysts, were synthesized with the method of one-step pyrolysis. The structure of the Ni-Cu/ASC catalyst with Ni-Cu nanoalloy encapsulated in carbon nanofibers (CNFs) was obsd. on the basis of the XRD, SEM and TEM anal. The catalytic performances of the prepd. catalysts on tar cracking were assessed in a two-stage fixed-bed pyrolysis-cracking/reforming device at the catalytic cracking temps. of 600-800°C. In a comparison to the single metal catalysts, the bimetallic Ni-Cu/ASC catalyst exerted a better performance on tar removal and possessed a higher selectivity to H2 and CO. The tar conversion efficiency and syngas (H2 + CO) yield, over the Ni-Cu/ASC catalyst at 800°C, reached up to 93.2% and 581.07 mL/g with the total volumetric content of 72.2% together with H2/CO of 1.1, resp. The Ni-Cu/ASC catalyst resulted in the lowest contents of two-ring and three-ring aroms. accompanied with highest contents of one-ring aroms. in tar. The Ni-Cu/ASC catalyst was reasonably stable because of its good resistance to sintering and carbon deposition.
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    58. 58
      Liu, H.; Chen, T.; Chang, D.; Chen, D.; He, H.; Frost, R. L. Catalytic cracking of tar derived from rice hull gasification over palygorskite-supported Fe and Ni. J. Mol. Catal A Chem. 2012, 363–364, 304– 310,  DOI: 10.1016/j.molcata.2012.07.005
      58
      Catalytic cracking of tar derived from rice hull gasification over palygorskite-supported Fe and Ni
      Liu, Haibo; Chen, Tianhu; Chang, Dongyin; Chen, Dong; He, Hongping; Frost, Ray L.
      Journal of Molecular Catalysis A: Chemical (2012), 363-364 (), 304-310CODEN: JMCCF2; ISSN:1381-1169. (Elsevier B.V.)
      The catalytic performance of Fe-Ni/PG (PG: palygorskite) catalysts pre-calcined and reduced at 500 °C for catalytic decompn. of tar derived through rice hull gasification was investigated. The materials were characterized by using X-ray diffraction, hydrogen temp. redn., and transmission electron microscopy. The results showed that ferrites with spinel structure ((Fe, Ni)3O4) were formed during prepn. of bimetallic systems during calcination and redn. of the precursors (Fe-Ni/PG catalysts) and NiO metal oxide particles were formed over Fe6-Ni9/PG catalyst. The obtained exptl. data showed that Fe-Ni/PG catalysts had greater catalytic activity than natural PG. Tar removal using Fe6-Ni9/PG catalyst was as high as Fe10-Ni6/PG catalyst (99.5%). Fe6-Ni9/PG showed greater catalytic activity with greater H2 yield and showed stronger resistance to carbon deposition, attributed to the presence of NiO nanoparticles. Thus, the addn. of nickel and iron oxides played an important role in catalytic cracking of rice hull biomass tar.
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    59. 59
      Liu, L.; Liu, Y.; Song, J.; Ahmad, S.; Liang, J.; Sun, Y. Plasma-enhanced steam reforming of different model tar compounds over Ni-based fusion catalysts. J. Hazard. Mater. 2019, 377, 24– 33,  DOI: 10.1016/j.jhazmat.2019.05.019
      59
      Plasma-enhanced steam reforming of different model tar compounds over Ni-based fusion catalysts
      Liu, Lina; Liu, Yawen; Song, Jianwei; Ahmad, Shakeel; Liang, Jie; Sun, Yifei
      Journal of Hazardous Materials (2019), 377 (), 24-33CODEN: JHMAD9; ISSN:0304-3894. (Elsevier B.V.)
      Tar formation during biomass gasification is undesirable due to the decreased energy efficiency and increased costs for maintaining downstream equipment. The hybrid non-thermal plasma-catalysis method is considered to be a promising alternative, since it overcomes the disadvantages arising from both catalyst deactivation during catalytic reforming and the formation of undesirable liq. byproducts in plasma reforming. SiO2- and ZSM-5-supported Ni-based catalysts with different Ni loadings (0.5, 1, 3, and 5 wt%) were prepd. by thermal fusion and applied to the steam reforming of toluene. Different characterizations of fresh and spent catalysts including XRD, H2-TPR, N2 adsorption-desorption, SEM, TEM, XPS and TGA were conducted to show the properties of catalysts. The results indicated that Ni/ZSM-5 exhibited better performance than Ni/SiO2, due to the increased dispersion of Ni particles and the stronger metal-support interaction of Ni/ZSM-5, which was confirmed by the TEM and H2-TPR results. In addn., the performances of the catalysis-only (CatO), plasma-only (PlO), and in-plasma-catalysis (IPC) systems in steam reforming of different model tar compds. including benzene, toluene, furfural, naphthalene, fluorene and pyrene were compared using Ni(5 wt%)/ZSM-5. Obvious synergistic effects between DBD plasma and Ni(5 wt%)/ZSM-5 was obsd. for syngas prodn. in the IPC system.
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    60. 60
      Kang, S.; He, M.; Yin, C.; Xu, H.; Cai, Q.; Wang, Y.; Cui, L. Graphitic carbon embedded with Fe/Ni nano-catalysts derived from bacterial precursor for efficient toluene cracking. Green Chem. 2020, 22 (6), 1934– 1943,  DOI: 10.1039/C9GC03357B
      60
      Graphitic carbon embedded with Fe/Ni nano-catalysts derived from bacterial precursor for efficient toluene cracking
      Kang, Shifei; He, Maofen; Yin, Chaochuang; Xu, Haiyang; Cai, Qing; Wang, Yangang; Cui, Lifeng
      Green Chemistry (2020), 22 (6), 1934-1943CODEN: GRCHFJ; ISSN:1463-9262. (Royal Society of Chemistry)
      The environmentally-harmful byproduct - biomass tar - is the major obstacle during biomass gasification, which produces synthetic gas as a clean energy source from agricultural waste or other bio-wastes. The highly-dispersed Fe/Ni-based nano-catalysts are of great research interest because of their great catalytic performance for catalytic biomass tar cracking. Supported Fe/Ni alloy catalysts were recognized as promising tar-cracking catalysts with the ability of redox enhancement and C deposition prevention. However, the controllable synthesis of highly-dispersed Fe/Ni nano-catalysts with high activity and stability remains a huge challenge. Highly-dispersed FeNi alloy catalysts embedded in graphitic C (BC-FeNi) were successfully synthesized by simple calcination of a bacterial precursor, which can be easily harvested by collecting nonpathogenic bacteria in a Fe/Ni ion enriched liq. medium. The bacteria served as a C source and helped to uniformly distribute the Fe-Ni ions in the precursor for subsequent prepn. of highly-dispersed FeNi catalysts. TEM showed the BC-FeNi contained well-dispersed Fe-Ni nanoparticles with sizes of 3-10 nm in a mesoporous graphitic C matrix, which were beneficial for the protection of metal nanoparticles against coking and thus were highly desirable for catalytic biomass tar cracking. The conversion rate of the biomass tar model compd. - toluene by BC-FeNi nano-catalysts was 82.6% at 700° and 95.8% at 800°, which were significantly superior over the control sample supported by active C. Noticeably, the metal loading (1.01%) in the bacteria-derived BC-FeNi catalysts was very lower compared to previous studies using other synthetic methods (usually >10%). This unique nature grants that the bacterial method may enable the facile design and synthesis of other types of practical nano-materials.
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    61. 61
      Kaewpanha, M.; Karnjanakom, S.; Guan, G.; Hao, X.; Yang, J.; Abudula, A. Removal of biomass tar by steam reforming over calcined scallop shell supported Cu catalysts. J. Energy Chem. 2017, 26 (4), 660– 666,  DOI: 10.1016/j.jechem.2017.03.012
      There is no corresponding record for this reference.
    62. 62
      Huang, Z.; Gao, N.; Lin, Y.; Wei, G.; Zhao, K.; Zheng, A.; Zhao, Z.; Yuan, H.; Li, H. Exploring the migration and transformation of lattice oxygen during chemical looping with NiFe2O4 oxygen carrier. Chem. Eng. J. 2022, 429, 132064,  DOI: 10.1016/j.cej.2021.132064
      62
      Exploring the migration and transformation of lattice oxygen during chemical looping with NiFe2O4 oxygen carrier
      Huang, Zhen; Gao, Na; Lin, Yan; Wei, Guoqiang; Zhao, Kun; Zheng, Anqing; Zhao, Zengli; Yuan, Haoran; Li, Haibin
      Chemical Engineering Journal (Amsterdam, Netherlands) (2022), 429 (), 132064CODEN: CMEJAJ; ISSN:1385-8947. (Elsevier B.V.)
      Chem. looping (CL) technol. using an oxygen carrier (OC) offers a versatile platform to convert various fuels (e.g., CH4, coal, and biomass) to value-added products (e.g., heat, syngas, and H2) in a clean and efficient approach. Currently, the migration and transformation mechanisms of lattice oxygen in spinel OCs were not extensively investigated, which are considered the cornerstone of OC. In this work, the release-uptake paths of lattice oxygen and the chem. reaction laws at interface were studied in detail using a composite metal oxide (NiFe2O4) as an OC through (in-situ) XPS technol. coupled with fixed bed expts. Mechanistic studies indicate that the chem. reaction interface is fixed on the surface of OC particles, and the concn. gradient between the surface and the bulk drives the transmission of lattice oxygen to achieve the redn. or oxidn. of OC. Addnl., an important hydroxyl ions formation process of OC is confirmed by an in-situ XPS.
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    63. 63
      Ren, J.; Liu, Y.-L. Promoting syngas production from steam reforming of toluene using a highly stable Ni/(Mg, Al)Ox catalyst. Appl. Catal. B 2022, 300, 120743,  DOI: 10.1016/j.apcatb.2021.120743
      63
      Promoting syngas production from steam reforming of toluene using a highly stable Ni/(Mg, Al)Ox catalyst
      Ren, Jie; Liu, Yi-Ling
      Applied Catalysis, B: Environmental (2022), 300 (), 120743CODEN: ACBEE3; ISSN:0926-3373. (Elsevier B.V.)
      Toluene, as one of the representative biomass tar model compd., has been widely chosen for investigation of biomass tar reforming. Herein, novel Ni/(Mg, Al)Ox (Ni/MAO) catalysts derived from Ni-Mg-Al hydrotalcites were prepd. successfully and used for steam reforming of toluene (SRT). Among all the catalysts, Ni/MAO catalyst prepd. at pH of 10 and aging temp. of 20°C (Ni/MAO-10) exhibited superior activity in toluene conversion (95.3%) and syngas prodn. (833 mmol/g-Ni), as well as the excellent resistance to carbon deposition. Through characterizations, the highest basicity, highest reducibility, tailored "rosette-like" morphol., and larger sp. surface area in Ni/MAO-10 were confirmed. Furthermore, the structure-activity relationship, reforming mechanism, deactivation, and regeneration of the catalyst were comprehensively elaborated from rigorous expts., and meanwhile, the activation energies and turnover frequency (TOF) values of four Ni/MAO catalysts in SRT were calcd. to theor. explain their activities.
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    64. 64
      Theofanidis, S. A.; Galvita, V. V.; Poelman, H.; Batchu, R.; Buelens, L. C.; Detavernier, C.; Marin, G. B. Mechanism of carbon deposits removal from supported Ni catalysts. Appl. Catal. B 2018, 239, 502– 512,  DOI: 10.1016/j.apcatb.2018.08.042
      64
      Mechanism of carbon deposits removal from supported Ni catalysts
      Theofanidis, Stavros Alexandros; Galvita, Vladimir V.; Poelman, Hilde; Batchu, Rakesh; Buelens, Lukas C.; Detavernier, Christophe; Marin, Guy B.
      Applied Catalysis, B: Environmental (2018), 239 (), 502-512CODEN: ACBEE3; ISSN:0926-3373. (Elsevier B.V.)
      Catalyst deactivation due to carbon deposition is a major issue in all reforming technologies. Because of the significant economic cost of catalyst replacement, catalyst regeneration is increasingly attracting attention. The regeneration mechanism of Ni catalysts, with respect to carbon removal, was investigated on support materials prepd. by one-pot synthesis. The supports were classified based on their redox functionality: Al2O3, MgAl2O4 show no redox properties in contrast to MgFe0.09Al1.91O4 and CeZrO2 that have redox functionality. A Temporal Anal. of Products (TAP) setup was used to investigate the isothermal regeneration mechanism of Ni catalysts at 993 K by O2. Different mechanisms were distinguished depending on the redox functionality of the support material. Two consecutive steps occur on the support that have no redox properties (Al2O3 and MgAl2O4): metallic Ni is oxidized to form NiO (oxidn. step), resulting in an initial local temp. increase of 50-60 K in total, enabling metal particle migration to carbon that was initially sepd. from the metal and subsequent oxidn. through NiO lattice oxygen (redn. step). On the other hand, the mechanism of carbon removal by O2 from Ni catalysts on supports with redox properties does not require particle migration. Two parallel contributions are proposed: (1) Ni metal is oxidized to form NiO, where after lattice oxygen of NiO is used for the oxidn. of carbon that is deposited upon the metals, (2) carbon oxidn. through lattice oxygen that is provided by the support. No dependency of the carbon gasification mechanism on the exposed fraction of the metal (particle size in the nanoscale) or on the structure of the deposited carbon was concluded.
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    65. 65
      Shen, Y. Chars as carbonaceous adsorbents/catalysts for tar elimination during biomass pyrolysis or gasification. Renewable Sustainable Energy Rev. 2015, 43, 281– 295,  DOI: 10.1016/j.rser.2014.11.061
      65
      Chars as carbonaceous adsorbents/catalysts for tar elimination during biomass pyrolysis or gasification
      Shen, Yafei
      Renewable & Sustainable Energy Reviews (2015), 43 (), 281-295CODEN: RSERFH; ISSN:1364-0321. (Elsevier Ltd.)
      Biomass tar could be produced along with syngas during biomass pyrolysis/gasification. Tar elimination by efficient adsorption and catalytic conversion by carbon-based adsorbents/catalysts with chem. inertness should be attractive methods to commercialize this technol. Biochars are the byproducts of biomass pyrolysis/gasification that can be used as low-cost carbon-based adsorbents to adsorb heavy metals or org. pollutants. Meanwhile, the char-supported catalysts could be simply gasified/burnt to recover the energy from the char without the need of frequently regeneration after deactivation. This review elaborated the recent progress on tar removal by biochars adsorption and catalytic cracking/reforming in detail. Two novel integrated concepts have been proposed that chars can be initially utilized and modified like activated chars for heavy metals or tars adsorption, after that, the satd. char-supported metallic catalysts can be employed for tar conversion. In addn., biomass can directly adsorb the heavy metal ions and realize nascent tar in situ conversion along with the metal nanoparticles in situ generated and embedded in the biochar matrix after pyrolysis. Significantly, the nanocomposite char residue could be catalytically gasified into the useful syngas, accompanied by recycling and reuse of the catalyst metal species in the ash.
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    66. 66
      Liu, Q.; Gu, F.; Gao, J.; Li, H.; Xu, G.; Su, F. Coking-resistant Ni-ZrO2/Al2O3 catalyst for CO methanation. J. Energy Chem. 2014, 23 (6), 761– 770,  DOI: 10.1016/S2095-4956(14)60210-2
      There is no corresponding record for this reference.
    67. 67
      Fakeeha, A. H.; Khan, W. U.; Al-Fatesh, A. S.; Abasaeed, A. E. Stabilities of zeolite-supported Ni catalysts for dry reforming of methane. Chin. J. Catal. 2013, 34 (4), 764– 768,  DOI: 10.1016/S1872-2067(12)60554-3
      There is no corresponding record for this reference.
    68. 68
      Sun, H.; Feng, D.; Sun, S.; Wei, Q.; Zhao, Y.; Zhang, Y.; Xie, M.; Qin, Y. Effect of steam on coke deposition during the tar reforming from corn straw pyrolysis over biochar. Fuel Process. Technol. 2021, 224, 107007,  DOI: 10.1016/j.fuproc.2021.107007
      68
      Effect of steam on coke deposition during the tar reforming from corn straw pyrolysis over biochar
      Sun, Hongliang; Feng, Dongdong; Sun, Shaozeng; Wei, Qingyu; Zhao, Yijun; Zhang, Yu; Xie, Min; Qin, Yukun
      Fuel Processing Technology (2021), 224 (), 107007CODEN: FPTEDY; ISSN:0378-3820. (Elsevier Ltd.)
      Coke deposition is a crit. issue for catalysts in tar reforming. Steam is conducive to tar removal and hydrogen prodn. in biomass pyrolysis, while its effect on coke formation is not well known. Thus, a two-stage fluidized bed/fixed bed reactor was used to study the effect of steam addn. on coke deposition. The primary conclusions are as follows: combining steam and biochar, the tar removal efficiency is more than 90% within 20 min of time on stream (TOS). After the TOS reaches 30 min, the biochar surface is satd. with coke deposition and the sp. surface area of the biochar stops decreasing. The addn. of steam leads to a redn. in the combustion reactivity of the biochar. Besides, the aromatization of the biochar increase and the no. of O-contg. structures decreases. For the tar, the addn. of steam reduces the aliphatics content and increases the O-contg. aroms. content. For the gas compn., the addn. of steam results in the decrease of CH4 yield while the H2 yield increases to 0.12 L/g. The H/C at. ratio of the gas compn. decreases while the O/C at. ratio increases. The active coke is consumed and decompd. after the introduction of steam. The remaining coke is dominated by inert coke. This contributes to the relatively developed pore structure but a weakened combustion reactivity of biochar.
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    69. 69
      Pereira Lopes, R.; Astruc, D. Biochar as a support for nanocatalysts and other reagents: Recent advances and applications. Coord. Chem. Rev. 2021, 426, 213585,  DOI: 10.1016/j.ccr.2020.213585
      69
      Biochar as a support for nanocatalysts and other reagents: Recent advances and applications
      Pereira Lopes, Renata; Astruc, Didier
      Coordination Chemistry Reviews (2021), 426 (), 213585CODEN: CCHRAM; ISSN:0010-8545. (Elsevier B.V.)
      A review. The transformation and use of the biomass are of fundamental energetic and ecol. interest. The general objective of this review is to provide an overview of biochar (a major biomass product) as a support for nanocatalysts and other reagents, its mode of coordination and activation with nanoparticles and applications. This includes the physico-chem. characteristics of biochar, the advances in its prodn. processes, and its activation and functionalization in order to improve its phys. and chem. characteristics and applications as support in catalysis and environmental decontamination. Biochar is a byproduct produced by carbonization of biomass. In this process, the products of interest are syngas and bio-oil, due to their high calorific value and their diverse applications. However, biochar has interesting characteristics. It can be used as support, allowing to disperse nanoparticles of the catalysts, such as those of the transition metals: Fe, Ag, Ni, Pd, etc. bimetallic compns. such as Ru/Re, Fe/Ni, etc. and metal oxides such as Fe3O4, CO3O4, CuO, TiO2, etc. increasing the reactivity of the system, minimizing the leaching of the catalysts and allowing their re-use. These materials can be employed in the degrdn. of contaminants in aq. systems, soil and sediments, tar reforming reactions and synthesis of fine chems. This review will serve as the basis for new research aiming to add value to this important resource.
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    70. 70
      Yu, J.; Tang, L.; Pang, Y.; Zeng, G.; Wang, J.; Deng, Y.; Liu, Y.; Feng, H.; Chen, S.; Ren, X. Magnetic nitrogen-doped sludge-derived biochar catalysts for persulfate activation: Internal electron transfer mechanism. Chem. Eng. J. 2019, 364, 146– 159,  DOI: 10.1016/j.cej.2019.01.163
      70
      Magnetic nitrogen-doped sludge-derived biochar catalysts for persulfate activation: Internal electron transfer mechanism
      Yu, Jiangfang; Tang, Lin; Pang, Ya; Zeng, Guangming; Wang, Jiajia; Deng, Yaocheng; Liu, Yani; Feng, Haopeng; Chen, Song; Ren, Xiaoya
      Chemical Engineering Journal (Amsterdam, Netherlands) (2019), 364 (), 146-159CODEN: CMEJAJ; ISSN:1385-8947. (Elsevier B.V.)
      Persulfate-based advanced oxidn. process is a powerful countermeasure for water remediation, where effective and low-cost catalysts are still needed. Herein, a one-pot synthetic method for magnetic nitrogen-doped sludge biochar (MS-biochar) was presented, which exhibited better catalytic property with PDS for tetracycline degrdn. than typical graphitic carbon (graphite powder, graphene oxide and multiwalled carbon nanotubes) and two other types biochars. EDAX manifested the uniform dispersion of elements in MS-biochar. Similar to "top-down", a research thought from whole to part of MS-biochar for contribution measurement was presented, where acid-sol. substance (ASS) was the most important contributor for MS-400/600 while carbon matrix (CM) was dominant for MS-800. Quenching and EPR demonstrated a free-radicals pathway in MS-biochar/PDS, where ASS mainly assumed to be effective for SO·-4 and CM was primarily committed to ·OH generation. EDAX, XPS and Raman studies proved three kinds of catalytic sites, namely the iron compds., doped nitrogen and graphitic carbon. And their activating mechanism were discussed where one internal electron migration path (from sp3 to nanocryst. sp2 carbon) has been first proposed. Reusability, metal leaching detection and pharmaceutical wastewater application indicated the potential of MS-biochar. This work not only presents a potential resource-based disposal of sewage sludge, a novel research thought from whole to part for materials performance measurement, but also provides guidance for carbon materials' design for persulfate activation, esp. for sp2 and sp3 co-hybridized carbons.
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    71. 71
      Mao, Z.; Lustemberg, P. G.; Rumptz, J. R.; Ganduglia-Pirovano, M. V.; Campbell, C. T. Ni nanoparticles on CeO2 (111): energetics, electron transfer, and structure by Ni adsorption calorimetry, spectroscopies, and density functional theory. ACS Catal. 2020, 10 (9), 5101– 5114,  DOI: 10.1021/acscatal.0c00333
      71
      Ni Nanoparticles on CeO2(111): Energetics, Electron Transfer, and Structure by Ni Adsorption Calorimetry, Spectroscopies, and Density Functional Theory
      Mao, Zhongtian; Lustemberg, Pablo G.; Rumptz, John R.; Ganduglia-Pirovano, M. Veronica; Campbell, Charles T.
      ACS Catalysis (2020), 10 (9), 5101-5114CODEN: ACCACS; ISSN:2155-5435. (American Chemical Society)
      The morphol., interfacial bonding energetics, and charge transfer of Ni clusters and nanoparticles on slightly reduced CeO2-x(111) surfaces at 100-300 K have been studied using single-crystal adsorption calorimetry (SCAC), low-energy ion scattering spectroscopy (LEIS), XPS, LEED (LEED), and d. functional theory (DFT). The initial heat of adsorption of Ni vapor decreased with the extent of pre-redn. (x) of CeO2-x(111), showing that stoichiometric ceria adsorbs Ni more strongly than oxygen vacancies. On CeO1.95(111) at 300 K, the heat dropped quickly with coverage in the first 0.1 ML, attributed to nucleation of Ni clusters on stoichiometric steps, followed by the Ni particles spreading onto less favorable terrace sites. At 100 K, the clusters nucleate on terraces due to slower diffusion. Adsorbed Ni monomers are in the +2 oxidn. state, and they bind more strongly by ~ 45 kJ/mol to step sites than terraces. The measured heat of adsorption vs. av. particle size on terraces is favorably compared to DFT calcns. The Ce 3d XPS line shape showed an increase in Ce3+/Ce4+ ratio with Ni coverage, providing the no. of electrons donated to ceria per Ni atom. The charge transferred per Ni is initially large but strongly decreases with increasing cluster size for both expts. and DFT, and it shows large differences between clusters at steps vs. terraces. This charge is localized on the interfacial Ni and Ce atoms in their at. layers closest to the interface. This knowledge is crucial to understanding the nature of the active sites on the surface of Ni/CeO2 catalysts, for which metal-oxide interactions play a very important role in the activation of O-H and C-H bonds. The changes in these interactions with Ni particle size (metal loading) and the extent of redn. of ceria help to explain how previously reported catalytic activity and selectivity change with these same structural details.
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    72. 72
      Navarro, R. M.; Pena, M. A.; Fierro, J. L. G. Hydrogen production reactions from carbon feedstocks: fossil fuels and biomass. Chem. Rev. 2007, 107 (10), 3952– 3991,  DOI: 10.1021/cr0501994
      72
      Hydrogen Production Reactions from Carbon Feedstocks: Fossil Fuels and Biomass
      Navarro, R. M.; Pena, M. A.; Fierro, J. L. G.
      Chemical Reviews (Washington, DC, United States) (2007), 107 (10), 3952-3991CODEN: CHREAY; ISSN:0009-2665. (American Chemical Society)
      A review. The fuel cell technol., as well as the prodn. of ammonia and other traditional used, required large amts. of H2. Feedstocks for H2 are methane, liq. hydrocarbons, methanol, coal, biomass and biomass derived products. The common processes to produce H2 from these feeds are steam reforming, partial and autothermal oxidn., catalytic decompn. of CH4, CH4 aromatization, and gasification of biomass in supercrit. water.
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    73. 73
      Rostrup-Nielsen, J. R.; Sehested, J.; No̷rskov, J. K. Hydrogen and synthesis gas by steam-and CO2 reforming. Adv. Catal. 2002, 47, 65– 139,  DOI: 10.1016/S0360-0564(02)47006-X
      73
      Hydrogen and synthesis gas by steam- and CO2 reforming
      Rostrup-Nielsen, Jens R.; Sehested, Jens; Norskov, Jens K.
      Advances in Catalysis (2002), 47 (), 65-139CODEN: ADCAAX; ISSN:0360-0564. (Elsevier Science)
      A review. Steam reforming reactions will play a key role in new applications of synthesis gas and in a future hydrogen economy. The aim of this review is to provide a coherent description of the catalysis of the reforming reactions. The review is not comprehensive. The first section deals with the applications of synthesis gas and hydrogen and the various synthesis.
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    74. 74
      Boldrin, P.; Gallagher, J. R.; Combes, G. B.; Enache, D. I.; James, D.; Ellis, P. R.; Kelly, G.; Claridge, J. B.; Rosseinsky, M. J. Proxy-based accelerated discovery of Fischer–Tropsch catalysts. Chem. Sci. 2015, 6 (2), 935– 944,  DOI: 10.1039/C4SC02116A
      74
      Proxy-based accelerated discovery of Fischer-Tropsch catalysts
      Boldrin, Paul; Gallagher, James R.; Combes, Gary B.; Enache, Dan I.; James, David; Ellis, Peter R.; Kelly, Gordon; Claridge, John B.; Rosseinsky, Matthew J.
      Chemical Science (2015), 6 (2), 935-944CODEN: CSHCCN; ISSN:2041-6520. (Royal Society of Chemistry)
      Development of heterogeneous catalysts for complex reactions such as Fischer-Tropsch synthesis of fuels is hampered by difficult reaction conditions, slow characterization techniques such as chemisorption and temp.-programmed redn. and the need for long term stability. High-throughput (HT) methods may help, but their use has until now focused on bespoke micro-reactors for direct measurements of activity and selectivity. These are specific to individual reactions and do not provide more fundamental information on the materials. Here we report using simpler HT characterization techniques (XRD and TGA) along with ageing under Fischer-Tropsch reaction conditions to provide information analogous to metal surface area, degree of redn. and thousands of hours of stability testing time for hundreds of samples per mo. The use of this method allowed the identification of a series of highly stable, high surface area catalysts promoted by Mg and Ru. In an advance over traditional multichannel HT reactors, the chem. and structural information we obtain on the materials allows us to identify the structural effects of the promoters and their effects on the modes of deactivation obsd.
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    75. 75
      Bayram, B.; Soykal, I. I.; Deak, D. V.; Miller, J. T.; Ozkan, U. S. Ethanol steam reforming over Co-based catalysts: Investigation of cobalt coordination environment under reaction conditions. J. Catal. 2011, 284 (1), 77– 89,  DOI: 10.1016/j.jcat.2011.09.001
      75
      Ethanol steam reforming over Co-based catalysts: Investigation of cobalt coordination environment under reaction conditions
      Bayram, Burcu; Soykal, I. Ilgaz; von Deak, Dieter; Miller, Jeffrey T.; Ozkan, Umit S.
      Journal of Catalysis (2011), 284 (1), 77-89CODEN: JCTLA5; ISSN:0021-9517. (Elsevier Inc.)
      The transformations and the state of cobalt species during steam reforming of ethanol over Co/CeO2 were investigated using in situ x-ray diffraction, controlled-atm. x-ray absorption fine structure, and XPS as well as steady state activity measurements. The catalyst was pretreated under an oxidizing or reducing atm. prior to characterization and activity testing to yield a Co3O4-rich or a Co0-rich surface, resp. While Co3O4 was inactive for ethanol steam reforming, gradual activation of the oxidn.-pretreated catalyst with temp. through redn. in Co3O4 took place under reaction conditions, and, over the activated catalyst, a mixt. of both CoO and metallic Co were obsd. Over the redn.-pretreated catalyst, metallic Co was partially oxidized to CoO during steam reforming of ethanol. The extent of cobalt redn. was obsd. to be independent of the initial state of the metal on the catalyst surface, and cobalt phase had the same compn. under reaction above 450°.
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    76. 76
      Li, Z.; Li, M.; Ashok, J.; Kawi, S. NiCo@NiCo phyllosilicate@CeO2 hollow core shell catalysts for steam reforming of toluene as biomass tar model compound. Energy Convers. Manage. 2019, 180, 822– 830,  DOI: 10.1016/j.enconman.2018.11.034
      76
      NiCo@NiCo phyllosilicate@CeO2 hollow core shell catalysts for steam reforming of toluene as biomass tar model compound
      Li, Ziwei; Li, Min; Ashok, Jangam; Kawi, Sibudjing
      Energy Conversion and Management (2019), 180 (), 822-830CODEN: ECMADL; ISSN:0196-8904. (Elsevier Ltd.)
      Developing sintering and carbon resistant tar removal catalysts is crucial for biomass gasification technol. Herein, for the first time, NiCo@NiCo phyllosilicate@CeO2 hollow core shell catalysts have been designed for steam reforming of toluene (SRT) as the biomass tar model compd. They show both good catalytic activity and stability within 45 h of time on stream due to their high sintering resistance of NiCo because of the strong interactions between NiCo and CeO2, high metal exposure as a result of the high sp. surface area, high surface metal concn. as well as the high oxygen vacancies as evidenced from the H2-Temp.-programmed redn. (H2-TPR), H2 chemisorption and XPS characterizations resp. Addnl., the synergistic effect between Ni and Co further improves their carbon resistant property. By comparison, Co@Co phyllosilicate@CeO2 catalysts perform the lowest toluene conversion and stability mainly due to their structural instability during reaction resulting from their high Si/Co ratio, leading to their low sp. surface area and Co exposure. The outstanding SRT performance of NiCo@NiCo phyllosilicate@CeO2 catalysts indicates their promising application for steam reforming of biomass tar reaction.
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    77. 77
      Zhai, Y.; Li, C.; Xu, G.; Ma, Y.; Liu, X.; Zhang, Y. Depolymerization of lignin via a non-precious Ni–Fe alloy catalyst supported on activated carbon. Green Chem. 2017, 19 (8), 1895– 1903,  DOI: 10.1039/C7GC00149E
      77
      Depolymerization of lignin via a non-precious Ni-Fe alloy catalyst supported on activated carbon
      Zhai, Yongxiang; Li, Chuang; Xu, Guangyue; Ma, Yanfu; Liu, Xiaohao; Zhang, Ying
      Green Chemistry (2017), 19 (8), 1895-1903CODEN: GRCHFJ; ISSN:1463-9262. (Royal Society of Chemistry)
      Lignin primarily composed of methoxylated phenylpropanoid subunits is an abundant biomass that can be used to produce aroms. Herein, a series of non-precious bimetallic Ni-Fe/AC catalysts were prepd. for efficiently depolymg. lignin. When organosolv birch lignin was used to det. the efficiency of the catalysts in methanol solvent, the Ni1-Fe1/AC (the ratio of Ni and Fe was 1) : (1) achieved the highest total yield of monomers (23.2 wt%, mainly propylguaiacol and propylsyringol) at 225 °C under 2 MPa H2 for 6 h. From GPC anal., it is also proved that lignin was efficiently depolymd. The Ni-Fe alloy structure was formed according to XRD, HRTEM, H2-TPR and XPS characterization. Based on the model compds.' tests, the Ni1-Fe1/AC catalyst showed high efficiency in ether bond cleavage without hydrogenation of arom. rings which could be attributed to the synergistic effect of Ni and Fe on the alloy structure. The total yield of monomers by using the Ni1-Fe1/AC catalyst reached 39.5 wt% (88% selectivity to PG and PS) when birch wood sawdust was used as the substrate.
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    78. 78
      Zhang, S.; Wang, P.; Chen, Y.; Yao, W.; Li, Z.; Tang, Y. One-Pot Synthesis of Pt Nanobowls Assembled from Ultrafine Nanoparticles for Methanol Oxidation Reaction. Nanomater (Basel) 2022, 12, 19,  DOI: 10.3390/nano12193471
      There is no corresponding record for this reference.
    79. 79
      Huang, Y.; Cheng, M.; Xiang, Z.; Cui, Y. Facile synthesis of NiCo2S4/CNTs nanocomposites for high-performance supercapacitors. R. Soc. Open Sci. 2018, 5 (9), 180953,  DOI: 10.1098/rsos.180953
      79
      Facile synthesis of NiCo2S4/ CNTs nanocomposites for high-performance supercapacitors
      Huang, Yunxia; Cheng, Ming; Xiang, Zhongcheng; cui, Yimin
      Royal Society Open Science (2018), 5 (9), 180953/1-180953/11CODEN: RSOSAV; ISSN:2054-5703. (Royal Society)
      Herein, porous NiCo2S4/CNTs nanocomposites were synthesized via a simple hydrothermal method followed by the sulphurization process using different sulfide sources. By comparing two different sulfur sources, the samples using thioacetamide as sulfide source delivered more remarkable electrochem. performance with a high specific capacitance of 1765 F g-1 at 1 A g-1 and an admirable cycling stability with capacitance retention of 71.7% at a high c.d. of 10 A g-1 after 5000 cycles in 2 M KOH aq. electrolyte. Furthermore, an asym. supercapacitor (ASC) device was successfully fabricated with the NiCo2S4/CNTs electrode as the pos. electrode and graphene as the neg. electrode. The device provided a max. energy d. of 29.44Wh kg-1 at a power d. of 812Wkg-1. Even at a high power d. of 8006 W kg-1, the energy d. still reaches 16.68 W h kg-1. Moreover, the ASC presents 89.8% specific capacitance retention after 5000 cycles at 5 A g-1. These results reveal its great potential for supercapacitors in electrochem. energy storage field.
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      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1cXisFShtL3J&md5=059203490831e6f07d7cb1d905093340
    80. 80
      Ren, J.; Cao, J.-P.; Yang, F.-L.; Zhao, X.-Y.; Tang, W.; Cui, X.; Chen, Q.; Wei, X.-Y. Layered uniformly delocalized electronic structure of carbon supported Ni catalyst for catalytic reforming of toluene and biomass tar. Energy Convers. Manage. 2019, 183, 182– 192,  DOI: 10.1016/j.enconman.2018.12.093
      80
      Layered uniformly delocalized electronic structure of carbon supported Ni catalyst for catalytic reforming of toluene and biomass tar
      Ren, Jie; Cao, Jing-Pei; Yang, Fei-Long; Zhao, Xiao-Yan; Tang, Wen; Cui, Xin; Chen, Qiang; Wei, Xian-Yong
      Energy Conversion and Management (2019), 183 (), 182-192CODEN: ECMADL; ISSN:0196-8904. (Elsevier Ltd.)
      Lignite rich in oxygen-contg. species (OCSs) was employed as perfect ion-exchange material for high activity catalyst prepn. HCl treatment Shengli lignite (HSL) selectively removed the org. salt and improved capability of ion exchange. In this paper, highly desirable and layered carbon supported Ni catalyst was prepd. by modified lignite. Thanks to the excellent role of Ni (1 1 1) plane and porous layered graphene-like delocalized electronic structure, specific structure of lignite provides an exchange platform in facilitating the Ni electron transfer during the catalytic reaction process. Ni loaded on HSL (Ni/HSL) showed the great catalytic activity and stability for reforming of toluene and biomass tar. Ni/HSL prepd. at 650°C shows the great activity and stability for toluene steam reforming (TSR) and biomass tar reforming (BTR). A series of instruments (XRD, SEM, TEM, H2-TPR, XPS, CO pulse adsorption, etc.) were employed for characterization. Based on these significant characterizations of catalyst, calcn. of turnover frequency (TOF), and results of conversion of toluene and corncob tar. The results revealed the layered delocalized electronic structure of Ni/HSL, which has lower activation energy than other reported catalysts. Uniform dispersed catalyst was synthesized successfully for reforming of toluene and biomass tar.
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    81. 81
      Xuan, J.; Liu, Y.; Xu, L.; Xin, Y.; Xue, L.; Li, L. Properties of SS304 Modified by Nickel–Cobalt Alloy Coating with Cauliflower-Shaped Micro/Nano Structures in Simulated PEMFC Cathode Environment. Nanomater(Basel) 2022, 12 (12), 1976,  DOI: 10.3390/nano12121976
      There is no corresponding record for this reference.
    82. 82
      Zhao, L.; Mu, X.; Liu, T.; Fang, K. Bimetallic Ni–Co catalysts supported on Mn–Al oxide for selective catalytic CO hydrogenation to higher alcohols. Catal. Sci. Technol. 2018, 8 (8), 2066– 2076,  DOI: 10.1039/C7CY02555F
      82
      Bimetallic Ni-Co catalysts supported on Mn-Al oxide for selective catalytic CO hydrogenation to higher alcohols
      Zhao, Lu; Mu, Xiaoliang; Liu, Tianshuo; Fang, Kegong
      Catalysis Science & Technology (2018), 8 (8), 2066-2076CODEN: CSTAGD; ISSN:2044-4753. (Royal Society of Chemistry)
      A series of bimetallic Ni-Co catalysts supported on Mn-Al oxide with different Ni/Co molar ratios were synthesized using a sol-gel method and applied for CO hydrogenation to higher alcs. The phys. and chem. properties of the as-prepd. catalysts were investigated by various characterization methods such as XRD, N2 adsorption/desorption, H2-TPR, TEM, XPS, CO-TPD, H2-TPD, and CO-TPSR. The results indicated that a stronger interaction between Ni and Co ions led to the formation of a Ni-Co alloy in the reduced catalysts, and CO conversion and alc. selectivity changed depending on the Ni/Co molar ratio that significantly influenced the properties of the catalysts. The appropriate Ni/Co molar ratio can improve the reducibility, increase the amt. of non-dissocd. CO on the catalyst surface for CO insertion, and enhance the catalytic performance for higher alc. synthesis. In particular, a Ni/Co molar ratio of 5/3 was the most suitable for the phys.-chem. and catalytic properties of the bimetallic Ni-Co catalysts for CO hydrogenation to higher alcs.
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    83. 83
      Law, Y. T.; Dintzer, T.; Zafeiratos, S. Surface oxidation of NiCo alloy: A comparative X-ray photoelectron spectroscopy study in a wide pressure range. Appl. Surf. Sci. 2011, 258 (4), 1480– 1487,  DOI: 10.1016/j.apsusc.2011.09.111
      83
      Surface oxidation of NiCo alloy. A comparative x-ray photoelectron spectroscopy study in a wide pressure range
      Law, Y. T.; Dintzer, T.; Zafeiratos, S.
      Applied Surface Science (2011), 258 (4), 1480-1487CODEN: ASUSEE; ISSN:0169-4332. (Elsevier B.V.)
      Oxidn. of NiCo alloy was studied under two pressure regimes, 5 × 10-10 and 5 × 10-1 bar, by XPS. The aim of this work is to investigate the synergetic effect between the 2 alloy components during the initial stages of oxidn. At low O pressure, segregation and preferential oxidn. of Co takes place, while oxidn. of Ni is largely suppressed. The species dominating the surface is CoO but small amt. of metallic Co still remains even after prolonged oxidn. at 670 K. At 0.5 bar O2 pressure, alloy oxidn. was found to be temp. depended. From 420 K to 520 K, Co is completely transformed to CoO and the Ni:Co at. ratio at the surface approaches a min., similar to the observations at low pressure regime. However, at higher temps. (from 520 K to 720 K), Ni is re-segregated on the surface, in the expense of Co, while CoO is further oxidized to Co3O4. At this temp. range formation of mixed Ni-Co-O spinel-like oxides is probable as supported by the characteristic modifications of the Ni 2p3/2 photoelectron peak and the increase of the Ni:Co at. ratio.
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    84. 84
      Tang, W.; Cao, J.; Wang, Z.; He, Z.; Liu, T.; Wang, Z.; Yang, F.; Ren, J.; Zhao, X.; Feng, X.; Bai, H. Comparative evaluation of tar steam reforming over graphitic carbon supported Ni and Co catalysts at low temperature. Energy Convers. Manage. 2021, 244, 114454,  DOI: 10.1016/j.enconman.2021.114454
      84
      Comparative evaluation of tar steam reforming over graphitic carbon supported Ni and Co catalysts at low temperature
      Tang, Wen; Cao, Jing-Pei; Wang, Zhi-Hao; He, Zi-Meng; Liu, Tian-Long; Wang, Ze-Ying; Yang, Fei-Long; Ren, Jie; Zhao, Xiao-Yan; Feng, Xiao-Bo; Bai, Hong-Cun
      Energy Conversion and Management (2021), 244 (), 114454CODEN: ECMADL; ISSN:0196-8904. (Elsevier Ltd.)
      The development of cheap and highly dispersed nano-catalyst is one of the key technologies for low temp. steam reforming (SR) of biomass tar. This work used acid-washed and oxidized Shengli lignite char (OXAWSL) as carbon precursor to load Co (Co/OXAWSL) and Ni (Ni/OXAWSL) via ion exchange method to SR of toluene and biomass tar. The Co/OXAWSL was more active and stable than Ni/OXAWSL during the 30 h test with a final toluene conversion of 85% at a relatively low temp. of 450°C and steam to carbon ratio (S/C) of 3.4, which resulted from its small particle size (5.6 nm) and high dispersion (12.3%) of Co. The relatively high H2 prodn. (42.59 mmol/g-biomass) over Co0.1/OXAWSL (450°C, S/C = 3.4) in SR of tar was also obtained. A low Ea (22.0 kJ/mol) value of Co/OXAWSL and good affinity to oxygen for Co explained its excellent performance. The low-temp. tar cracking process can provide theor. and tech. support for the large-scale industrial utilization of biomass pyrolysis and gasification.
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    85. 85
      Wang, Y.; Wang, H.; Li, S.; Sun, S. Waste PET Plastic-Derived CoNi-Based Metal-Organic Framework as an Anode for Lithium-Ion Batteries. ACS Omega 2022, 7 (39), 35180– 35190,  DOI: 10.1021/acsomega.2c04264
      85
      Waste PET Plastic-Derived CoNi-Based Metal-Organic Framework as an Anode for Lithium-Ion Batteries
      Wang, Yaxin; Wang, Huimin; Li, Shuyuan; Sun, Shaorui
      ACS Omega (2022), 7 (39), 35180-35190CODEN: ACSODF; ISSN:2470-1343. (American Chemical Society)
      Recycling waste PET plastics into metal-org. frameworks is conducive to both pollution alleviation and sustainable economic development. Herein, we have utilized waste PET plastic to synthesize CoNi-MOF applied to lithium battery anode materials via a low-temp. solvothermal method for the first time. The prepn. process is effortless, and the sources' conversion rate can reach almost 100%. In addn., the anode performance of MOFs with various Co/Ni mole ratios was investigated. The as-synthesized Co0.8Ni-MOF exhibits excellent crystallinity, purity, and electrochem. performance. The initial discharge and charge capacities are 2496 and 1729 mAh g-1, resp. Even after 200 cycles, the Co0.8Ni-MOF electrode can exhibit a high Coulombic efficiency of over 99%. Consequently, given the environmental and economic benefits, the Co0.8Ni-MOF derived from waste PET plastic is thought to be an appealing anode material for lithium-ion batteries.
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    86. 86
      Li, Z.; Wang, J.; Tian, K.; Zhou, C.; Pei, Y.; Zhang, J.; Zang, L. Nickel-Cobalt Oxide Nanoparticle-Induced Biohydrogen Production. ACS Omega 2022, 7 (45), 41594– 41605,  DOI: 10.1021/acsomega.2c05580
      86
      Nickel-Cobalt Oxide Nanoparticle-Induced Biohydrogen Production
      Li, Zhenmin; Wang, Jiangmei; Tian, Kexin; Zhou, Chen; Pei, Yong; Zhang, Jishi; Zang, Lihua
      ACS Omega (2022), 7 (45), 41594-41605CODEN: ACSODF; ISSN:2470-1343. (American Chemical Society)
      The pos. effects of metal oxide nanoparticles (NPs) on dark fermn. (DF) for biohydrogen synthesis have been increased, and the mechanism still needs to be further revealed. In this study, nickel-cobalt oxide (NiCo2O4) NPs were prepd. to increase H2 yield via DF. The highest (259.67 mL/g glucose) and the lowest (188.14 mL/g glucose) yields were achieved at 400 and 800 mg/L NiCo2O4 NPs added, resp., with their corresponding 33.97% increase and 2.93% decrease compared with the control yield (193.82 mL/g glucose). Meanwhile, the microbial community further confirmed that NiCo2O4 NPs increased the abundance of the dominant H2-producing Clostridium sensu stricto1 by 23.05%. The gene prediction also showed that NiCo2O4 NPs increased the abundance of genes encoding the rate-limiting enzyme pyruvate kinase in glycolysis, thus increasing the substrate conversion. Moreover, the gene abundance of key enzymes directly related to H2 evolution was also increased at different levels.
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  • Supporting Information

    Supporting Information

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