A first-principles study of oxygenates on Co surfaces in Fischer-Tropsch synthesis

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

*Corresponding author for this work

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Abstract

Extensive density function theory calculations are performed to study the mechanism of the formation of aldehyde and alcohol on Co surfaces in Fischer-Tropsch synthesis, a challenging issue in heterogeneous catalysis. Three possible pathways for the production of formaldehyde and methanol on flat and stepped Co(0001) surfaces are investigated: (i) CO + 4H -> CHO + 3H -> CH2O + 2H -> CH3O + H -> CH3OH; (ii) CO + 4H -> COH + 3H -> CHOH + 2H -> CH2OH + H -> CH3OH; and (iii) the coupling reactions of CH2 + O -> CH2O and CH3 + OH -> CH3OH. It is found that these pathways are generally favored at step sites, and the preferred mechanism is pathway (i) via CHO. Furthermore, the three traditional chain growth mechanisms in Fischer-Tropsch synthesis are semi quantitatively compared and discussed. Our results suggest that the two mechanisms involving oxygenate intermediates (the CO-insertion and hydroxycarbene mechanisms) are less important than the carbene mechanism in the production of long chain hydrocarbons. However, the CO-insertion mechanism may be responsible for the production of long-chain oxygenates.

Original languageEnglish
Pages (from-to)9464-9473
Number of pages10
JournalThe Journal of Physical Chemistry C
Volume112
Issue number25
Early online date4 Jun 2008
DOIs
Publication statusPublished - 26 Jun 2008

Keywords

  • density-functional theory
  • gas shift kinetics
  • methanol decomposition
  • hydrocarbon synthesis
  • cobalt catalysts
  • metal-surfaces
  • chain growth
  • PT(111)
  • mechanism
  • adsorption

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