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

Jiachun Chai, Robert Pestman, Wei Chen, A. Iulian Dugulan, Bo Feng, Zhuowu Men, Peng Wang*, Emiel J.M. Hensen

*Corresponding author for this work

    Research output: Contribution to journalArticleScientificpeer-review

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    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.

    Original languageEnglish
    Pages (from-to)93-102
    Number of pages10
    JournalJournal of Catalysis
    Volume400
    DOIs
    Publication statusPublished - 2021

    Keywords

    • Carburization
    • Fischer-Tropsch synthesis
    • Iron
    • Mechanism
    • Synthesis gas

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