Understanding reaction-induced restructuring of well-defined FexOyCz compositions and its effect on CO2 hydrogenation

• Published in: Applied catalysis. B, Environmental Vol. 291; p. 120121
• Main Authors: Skrypnik, Andrey S., Yang, Qingxin, Matvienko, Alexander A., Bychkov, Victor Yu, Tulenin, Yuriy P., Lund, Henrik, Petrov, Sergey A., Kraehnert, Ralph, Arinchtein, Aleks, Weiss, Jana, Brueckner, Angelika, Kondratenko, Evgenii V.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 15-08-2021; Elsevier BV
• Subjects: Carbon dioxide; Catalysts; Catalytic converters; CO2 hydrogenation; Composition effects; Conversion; Decomposition reactions; Fischer-Tropsch; Hydrocarbons; Iron; Iron oxalate decomposition; Iron oxide; Magnetite; Methane; Oxalic acid; Paraffin; Paraffins; Phase composition; Selectivity; Steady state; Iron oxide; Magnetite; Iron oxalate decomposition; Fischer-Tropsch; CO2 hydrogenation
• ISSN: 0926-3373; 1873-3883
• DOI: 10.1016/j.apcatb.2021.120121

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•Different FexOyCz compositions were prepared by controlled iron oxalate decomposition.•Steady-state compositions in CO2 hydrogenation depend on the initial compositions.•The steady-state composition changes along the catalyst bed.•Iron carbides are formed directly in upstream catalyst layer.•Fe and Fe3O4 form CH4 from CO, while iron carbides convert CO2 to CH4.
Herein, we provide fundamentals relevant for the development of Fe-based catalysts for CO2hydrogenation to higher hydrocarbons. It was possible owing to preparation of well-defined FexOyCz compositions through controlled decomposition of iron oxalate, determination of their composition under CO2-FT reaction and catalytic tests in a broad range of CO2 conversion. Such steady-state composition changes along the catalyst bed. The changes and their strength depend on the initial phase composition. In addition to the reaction-induced catalyst restructuring, reaction pathways leading from CO2 to CO, CH4 and higher hydrocarbons were elucidated. A correlation between them and the steady-state composition was established and offers the possibility for tailored catalyst design and preparation. Our best performing promoter-free Fe-based catalyst shows the selectivity to CH4 below 10 %, while the selectivity to C2+-hydrocarbons is about 50 % at CO2 conversion of about 25 % and 300 °C. The olefin to paraffin ratio among C2-C4 hydrocarbons is 5.5.