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|Title:||First principle reaction path analysis of the Fischer-Tropsch synthesis mechanism. Effect of CO coverage on the kinetics of the CO insertion mechanism|
|Citation:||Zhuo, M.,Saeys, M. (2011). First principle reaction path analysis of the Fischer-Tropsch synthesis mechanism. Effect of CO coverage on the kinetics of the CO insertion mechanism. 11AIChE - 2011 AIChE Annual Meeting, Conference Proceedings : -. ScholarBank@NUS Repository.|
|Abstract:||Fischer-Tropsch Synthesis (FTS), the conversion of CO and H 2 to long chain hydrocarbons, (CH 2) n, and H 2O, involves a sequence of C-O scission, C-C forming, and C and O hydrogenation steps. Different reaction sequences have been proposed. Recent Density Functional Theory (DFT) calculations provide theoretical support for the CO insertion mechanism, where C-C bond formation via a RCH + CO step occurs before C-O scission. Subsequent surface science experiments confirmed that C-O bond breaking is indeed kinetically possible on Co(0001) terraces if a C xH y-O moiety can be formed, as proposed in the CO insertion mechanism. However, on a clean Co(0001) surface the calculated CO turnover frequency (TOF) for the CO insertion mechanism is several orders of magnitude lower than experimental values. FTS is performed under a CO partial pressure of about 7 bar. First principle phase diagram calculations indicate that the CO coverage exceeds 1/3 ML under such conditions, in agreement with experimental data. DFT calculations on a CO pre-covered Co(0001) surface further show that the binding energies of the various reaction intermediates decrease by about 10 kJ/mol in the presence of 1/3 ML CO, and the overall reaction energy for the CO insertion mechanism changes from +42 kJ/mol endothermic on a clean surface to -40 kJ/mol exothermic on the CO pre-covered surface. A kinetic analysis using the first principle data furthermore shows that the CO TOF increases from 10 -8 s -1 to 0.1 s -1 when the high CO coverage is accounted for.|
|Source Title:||11AIChE - 2011 AIChE Annual Meeting, Conference Proceedings|
|Appears in Collections:||Staff Publications|
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