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Deactivation of a CoMo Catalyst during Catalytic Hydropyrolysis of Biomass. Part 2. Characterization of the Spent Catalysts and Char

Cite this: Energy Fuels 2019, 33, 12, 12387–12402
Publication Date (Web):November 14, 2019
Copyright © 2019 American Chemical Society

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    In this work sulfided CoMo/MgAl2O4 catalysts used in fluid bed catalytic hydropyrolysis for the conversion of beech wood and wheat straw to liquid fuels were thoroughly characterized by Raman spectroscopy and scanning (transmission) electron microscopy (S(T)EM) together with energy dispersive X-ray spectroscopy (EDS). Potassium and calcium were transferred from the beech wood to the catalyst, and the accumulated amounts increased proportionally with the time on stream (TOS) and reached 0.67 and 0.28 wt % after 16.2 h, respectively, when beech wood was used as biomass feedstock with a feeding rate of approximately 270 g/h (4.4 kg in total) beech wood to 50 g of catalyst. The concentration of coke on the spent catalyst also increased with TOS and was 3.7 wt % (carbon) after 3.5 h and 7.2 wt % after 16.2 h, indicating that the coking rate decreased with time on stream. However, SEM-EDS indicated that the carbon concentration increased more on the surface than in the bulk, thereby increasing the risk of pore blocking. In addition, Raman spectroscopy showed that the initially formed coke was mostly graphitic, but the coke became less ordered as successive layers grew on top. Doping the catalyst with K2CO3, corresponding to a potassium loading of 1.9 wt %, prior to the sulfidation, led to a higher degree of stacking and increased the slab length of the MoS2 particles. Furthermore, SEM images of the spent catalyst indicated that the catalyst particles were encapsulated by a layer of coke during pyrolysis, but this layer was continuously removed by knock-off. This indicates that potassium acts as a catalyst for polymerization of tar and coking reactions on the catalyst. The effect of using wheat straw, which contains 10 times more potassium than beech wood, as feedstock was also investigated. This led to defluidization due to agglomeration within the first 0.3 h on stream. SEM images showed that agglomerates of char and catalyst particles, with a diameter up to 5 mm, were formed due to polymerization of the metaplast and tar. Additionally, SEM-EDS images showed that potassium was well-distributed in the agglomerates, indicating that potassium catalyzed the formation of these agglomerates.

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    Cited By

    This article is cited by 11 publications.

    1. Guanyu Wang, Yujie Dai, Haiping Yang, Qingang Xiong, Kaige Wang, Jinsong Zhou, Yunchao Li, Shurong Wang. A Review of Recent Advances in Biomass Pyrolysis. Energy & Fuels 2020, 34 (12) , 15557-15578.
    2. M. Z. Stummann, M. Høj, A. B. Hansen, P. Beato, P. Wiwel, J. Gabrielsen, P. A. Jensen, A. D. Jensen. Deactivation of a CoMo Catalyst during Catalytic Hydropyrolysis of Biomass. Part 1. Product Distribution and Composition. Energy & Fuels 2019, 33 (12) , 12374-12386.
    3. Liujie Xu, Ludi Wang, Yi Li, Qingbin Song, Zhipeng Tian, Chao Wang, Ming Zhao, Ningbo Gao. A novel high-entropy spinel ferrites (CoNiCuZnMg)Fe2O4 catalyst for H2 production via steam reforming of derived volatiles from polypropylene and waste cooking oil. Chemical Engineering Journal 2024, 488 , 150767.
    4. Bingxu Chen, Hao Du, Jianzhang Wang, Biao Liu, Jan J. Weigand, Huiquan Li, Shaona Wang, Jianping Peng, Yi Zhang. A novel method to leach vanadium, molybdenum and nickel from spent hydrodesulfurization catalysts using hydroxyl radicals (HO•) in Fe2O3-assisted oxygen microbubble process. Hydrometallurgy 2024, 223 , 106225.
    5. Rashid Minhas, Asif Hussain Khoja, Nida Naeem, Mustafa Anwar, Sehar Shakir, Rabia Liaquat, Israf Ud Din. Thermal steam methane reforming over bimetal-loaded hemp-derived activated carbon-based catalyst for hydrogen production. Research on Chemical Intermediates 2023, 49 (7) , 3181-3203.
    6. Xinyong Diao, Na Ji. Rational design of MoS2-based catalysts toward lignin hydrodeoxygenation: Interplay of structure, catalysis, and stability. Journal of Energy Chemistry 2023, 77 , 601-631.
    7. Shuang Xue, Zhongyang Luo, Haoran Sun, Wanchen Zhu. Product regulation and catalyst deactivation during ex-situ catalytic fast pyrolysis of biomass over Nickel-Molybdenum bimetallic modified micro-mesoporous zeolites and clays. Bioresource Technology 2022, 364 , 128081.
    8. Heather O. LeClerc, Geoffrey A. Tompsett, Alex D. Paulsen, Amy M. McKenna, Sydney F. Niles, Christopher M. Reddy, Robert K. Nelson, Feng Cheng, Andrew R. Teixeira, Michael T. Timko. Hydroxyapatite catalyzed hydrothermal liquefaction transforms food waste from an environmental liability to renewable fuel. iScience 2022, 25 (9) , 104916.
    9. Shinyoung Oh, Jechan Lee, Su Shiung Lam, Eilhann E. Kwon, Jeong-Myeong Ha, Daniel C.W. Tsang, Yong Sik Ok, Wei-Hsin Chen, Young-Kwon Park. Fast hydropyrolysis of biomass Conversion: A comparative review. Bioresource Technology 2021, 342 , 126067.
    10. Joby Sebastian, You Wayne Cheah, Diana Bernin, Derek Creaser, Louise Olsson. The Promotor and Poison Effects of the Inorganic Elements of Kraft Lignin during Hydrotreatment over NiMoS Catalyst. Catalysts 2021, 11 (8) , 874.
    11. Magnus Zingler Stummann, Martin Høj, Jostein Gabrielsen, Lasse Røngaard Clausen, Peter Arendt Jensen, Anker Degn Jensen. A perspective on catalytic hydropyrolysis of biomass. Renewable and Sustainable Energy Reviews 2021, 143 , 110960.

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