The role of H2 in Fe carburization by CO in Fischer-Tropsch catalysts

Journal article (2021)

Authors

Jiachun Chai Eindhoven University of Technology
Robert Pestman Eindhoven University of Technology
Wei Chen Eindhoven University of Technology
A.I. Dugulan RID/TS/Instrumenten groep
Bo Feng National Institute of Clean-and-Low-Carbon Energy, Shenhua NICE, Future Science and Technology City, Changping District, Beijing 102211, People's Republic of China
Zhuowu Men National Institute of Clean-and-Low-Carbon Energy, Shenhua NICE, Future Science and Technology City, Changping District, Beijing 102211, People's Republic of China
Peng Wang Wang Eindhoven University of Technology, National Institute of Clean-and-Low-Carbon Energy, Shenhua NICE, Future Science and Technology City, Changping District, Beijing 102211, People's Republic of China
Emiel J.M. Hensen Eindhoven University of Technology
Research Group
RID/TS/Instrumenten groep
Copyright: © 2021 Jiachun Chai, Robert Pestman, Wei Chen, A.I. Dugulan, Bo Feng, Zhuowu Men, Peng Wang, Emiel J.M. Hensen
DOI: https://doi.org/10.1016/j.jcat.2021.05.027
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Published Date

2021

Language

English

Research Group

RID/TS/Instrumenten groep

Abstract

The formation of Fe-carbide phases is relevant to the synthesis of Fischer-Tropsch synthesis catalysts. We investigated the carburization of Raney Fe as a model catalyst using spectroscopic and temperature-programmed techniques. IR spectroscopy shows that CO dissociation already occurs at −150 °C, while C diffusion into metallic Fe requires much higher temperature (~180 °C). The carburization rate increases with increasing H2/CO ratio, which can be attributed to the lower overall barrier for O removal as H2O as compared to CO2. O removal frees vacancies that are needed for CO dissociation. The resulting higher C coverage increases the driving force for Fe-carbide formation. A higher driving force leads to predominant formation of the more carbon-rich ε(́)-carbide, while χ-Fe5C2 is formed at lower H2/CO ratio. The removal of surface O appears to be the rate-limiting step under all conditions. Initially, most of deposited C is used for Fe-carbide formation with a small contribution to hydrocarbons formation.