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Title: Density functional theory study of the co insertion mechanism for Fischer-Tropsch synthesis over co catalysts
Authors: Zhuo, M.
Tan, K.F.
Borgna, A.
Saeys, M. 
Issue Date: 14-May-2009
Citation: Zhuo, M., Tan, K.F., Borgna, A., Saeys, M. (2009-05-14). Density functional theory study of the co insertion mechanism for Fischer-Tropsch synthesis over co catalysts. Journal of Physical Chemistry C 113 (19) : 8357-8365. ScholarBank@NUS Repository.
Abstract: Different mechanisms have been proposed for Fischer-Tropsch synthesis, the conversion of CO and H2 to long-chain alkanes. Density functional theory calculations indicate that CO activation has a barrier of 220 kJ/mol on Co(0001), and hence the concentration of surface C or CH2 species is likely too low to explain the high chain growth probability. Hydrogenation lowers the C-O dissociation barrier to 90 kJ/mol for HCO and to 68 kJ/mol for H2CO; however, CO hydrogenation has a high energy barrier of 146 kJ/mol and is +117 kJ/mol endothermic. We propose an alternative propagation cycle starting with CO insertion into surface RCH groups. The barrier for this step is 80 kJ/mol. RCHCO is subsequently hydrogenated to RCH2CHO, which undergoes C-O dissociation with a barrier of 50 kJ/mol. The hydrogenation barriers are 120 and 48 kJ/mol along the dominant reaction path. The calculated CO turnover frequency for the proposed CO insertion mechanism is 1 to 2 orders of magnitude faster the hydrogen-assisted CO activation mechanism and 4 orders of magnitude faster than direct CO activation on a model Co(0001) surface. © 2009 American Chemical Society.
Source Title: Journal of Physical Chemistry C
ISSN: 19327447
DOI: 10.1021/jp900281h
Appears in Collections:Staff Publications

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