Relationship between Iron Carbide Phases (ε-Fe2C, Fe7C3, and χ-Fe5C2) and Catalytic Performances of Fe/SiO2 Fischer-Tropsch Catalysts

Qiang Chang, Chenghua Zhang, Chengwei Liu, Yuxue Wei, Ajin V. Cheruvathur, A. Iulian Dugulan, J. W. Niemantsverdriet, Xingwu Liu, Yurong He, More Authors

    Research output: Contribution to journalArticleScientificpeer-review

    71 Citations (Scopus)

    Abstract

    The influence of different iron carbides on the activity and selectivity of iron-based Fischer-Tropsch catalysts has been studied. Different iron carbide phases are obtained by the pretreatment of a binary Fe/SiO2 model catalyst (prepared by coprecipitation method) to different gas atmospheres (syngas, CO, or H2). The phase structures, compositions, and particle sizes of the catalysts are characterized systematically by XRD, XAFS, MES, and TEM. It is found that in the syngas-treated catalyst only χ-Fe5C2 carbide is formed. In the CO-treated catalyst, Fe7C3 and χ-Fe5C2 with a bimodal particle size distribution are formed, while the H2-treated catalyst exhibits the bimodal size distributed ε-Fe2C and χ-Fe5C2 after a Fischer-Tropsch synthesis (FTS) reaction. The intrinsic FTS activity is calculated and assigned to each corresponding iron carbide based on the phase composition and the particle size. It is identified that Fe7C3 has the highest intrinsic activity (TOF = 4.59 × 10-2 s-1) among the three candidate carbides (ε-Fe2C, Fe7C3, and χ-Fe5C2) in typical mediumerature Fischer-Tropsch (MTFT) conditions (260-300 °C, 2-3 MPa, and H2/CO = 2). Moreover, FTS over ε-Fe2C leads to the lowest methane selectivity.

    Original languageEnglish
    Pages (from-to)3304-3316
    JournalACS Catalysis
    Volume8
    Issue number4
    DOIs
    Publication statusPublished - 2018

    Keywords

    • FeC
    • Fischer-Tropsch synthesis
    • in situ MES
    • iron carbide
    • iron catalyst
    • XAFS

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