Density Functional Theory Study of Iron and Cobalt Carbides for Fischer-Tropsch Synthesis

Jun Cheng, P. Hu*, Peter Ellis, Sam French, Gordon Kelly, C. Martin Lok

*Corresponding author for this work

Research output: Contribution to journalArticle

116 Citations (Scopus)

Abstract

Carbides are important phases in heterogeneous catalysis. However, the understanding of carbide phases is inadequate: Fe and Co are the two commercial catalysts for Fischer-Tropsch (FT) synthesis, and experimental work showed that Fe carbide is the active phase in FT synthesis, whereas the appearance of Co carbide is considered as a possible deactivation cause, TO understand very different catalytic roles of carbides, all the key elementary steps in FT synthesis, that is, CO dissociation, C(1) hydrogenation, and C(1)+C(1) coupling, are extensively investigated on both carbide surfaces using first principles calculations. In particular, the most important issues in FT synthesis, the activity and methane selectivity, on the carbide surfaces are quantitatively determined and analyzed. They are also discussed together with metallic Fe and Co surfaces. It is found that (i) Fe carbide is more active than metallic Fe and has similar methane selectivity to Fe, being consistent with the experiments; and (ii) Co carbide is less active than Co and has higher methane selectivity, providing evidence on the molecular level to support the suggestion that the formation of Co carbide is a cause of relatively high methane selectivity and deactivation on Co catalysts.

Original languageEnglish
Pages (from-to)1085-1093
Number of pages9
JournalJournal of Physical Chemistry C
Volume114
Issue number2
DOIs
Publication statusPublished - 21 Jan 2010

Keywords

  • EVANS-POLANYI RELATION
  • HETEROGENEOUS CATALYSIS
  • CO DISSOCIATION
  • CHAIN GROWTH
  • HYDROCARBON SYNTHESIS
  • VOLCANO CURVE
  • SURFACES
  • ADSORPTION
  • MECHANISM
  • RU(0001)

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