Fischer-Tropsch synthesis is rapidly becoming an important technology to convert a range of carbonaceous feedstocks into liquid transportation fuels and chemicals. The Fischer-Tropsch reaction is a very complex reaction involving many elementary reaction steps. The rate of these steps depends in a sensitive manner on the type of transition metal, the surface metal atom topology and the composition of the adsorbed layer. While density functional theory methods provide accurate data for the rate constants for these elementary reaction steps, microkinetics simulations allow to predict the compositon of the surface adsorbed layer as well as the rates of all elementary reaction steps. In this manner, important issues can be resolved that pertain to the mechanism of the Fischer-Tropsch reaction such as the dominant reaction pathway from reactants (CO and H2) to products (alkanes, alkenes, oxygenates and water). Pertinent questions relevant to the Fischer-Tropsch reaction relate to the mode of CO dissociation, which of the two main proposed mechanisms for chain growh - the carbide mechanism and the CO insertion mechanism – dominates, what the rate-controlling steps are and which elementary reaction steps influence the product selectivity. These issues are critical to understand the mechanism for syngas conversion into long-chain hydrocarbons on Co and Ru surfaces and on the competition between methane and ethanol for Rh. In this lecture, I will introduce the methodology of first-principles microkinetics simulations, discuss mechanistic aspects of CO activation and subsequent carbon coupling and hydrogenation reactions as relevant to Ru, Co and Rh surfaces. Emphasis will be on the understanding how metal choice and surface topology influence the activity and selectivity. The results emphasize the complexity of the reaction networks underlying synthesis gas conversion. Limitations of microkinetics modeling are discussed as well. R.A. van Santen, A.J. Markvoort, I.A.W. Filot, M.M Ghouri and E.J.M. Hensen Physical Chemistry Chemical Physics 15 (2013) 17038-17063. I.A.W. Filot, R.A. van Santen and E.J.M. Hensen, Catalysis Science and Technology 4 (2014) 3129-3140. I.A.W. Filot, R.A. van Santen and E.J.M. Hensen, Angewandte Chemie International Edition 53 (2014) 12746-12750. I.A.W. Filot, R.J.P. Broos, J.P.M. van Rijn, G.J.H.A. van Heugten, R.A. van Santen and E.J.M. Hensen,ACS Catalysis 5 (2015) 5453-5467.

Mechanistic insights into syngas conversion through first-principles-based microkinetics simulations

251st National Meeting (2016)

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