A density functional theory study of the a-olefin selectivity in Fischer-Tropsch synthesis

J. Cheng, T. Song, Peijun Hu, C.M. Lok, P. Ellis, S. French

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60 Citations (Scopus)

Abstract

We studied the alpha-olefin selectivity in Fischer-Tropsch (FT) synthesis using density functional theory (131717) calculations. We calculated the relevant elementary steps from C-2 to C-6 species. Our results showed that the barriers of hydrogenation and dehydrogenation reactions were constant with different chain lengths, and the chemisorption energies of alpha-olefins from DFT calculations also were very similar, except for C-2 species. A simple expression of the paraffin/olefin ratio was obtained based on a kinetic model. Combining the expression of the paraffin/olefin ratio and our calculation results, experimental findings are satisfactorily explained. We found that the physical origin of the chain length dependence of paraffin/olefin ratio is the chain length dependence of both the van der Waals interaction between adsorbed alpha-olefins and metal surfaces and the entropy difference between adsorbed and gaseous alpha-olefins, and that the greater chemisorption energy of ethylene is the main reason for the abnormal ethane/ethylene ratio. (c) 2008 Elsevier Inc. All rights reserved.
Original languageEnglish
Pages (from-to)20-28
Number of pages9
JournalJournal of Catalysis
Volume255
Issue number1
DOIs
Publication statusPublished - 01 Apr 2008

ASJC Scopus subject areas

  • Catalysis
  • Process Chemistry and Technology

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