The molecular details of the Fischer-Tropsch synthesis reaction have intrigued researchers in the field of heterogeneous catalysis for decades. Catalysts for this process have to be active for three types of reactions: (i) Dissociation of the strong CO bond, (ii) C-C coupling reactions to form longer chains, and (iii) hydrogenation to form products. The first reaction most likely controls the activity of the catalyst, whereas the other two reactions are important for the selectivity of the catalyst.<br/>Following the philosophy that well-defined systems can yield important information on catalytically relevant surface reactions we use a well-defined Co(0001) single crystal surface in a well-controlled atmosphere we systematically explore the elementary steps that play a role in Fischer-Tropsch synthesis. Regarding the activity of the catalyst we discuss our experimental findings regarding direct dissociation of CO, as well as regarding the removal of oxygen in the form of water. Using olefins of different chain length we then look at the chemistry of hydrocarbon species on the close-packed surface of cobalt. At Fischer-Tropsch conditions the surface is covered to a large extent with adsorbates, in particular CO. Infrared measurements indicate that the presence of adsorbed CO significantly affects the stabilities of hydrocarbon adsorbates. After discussing the experimental findings we will discuss them in the context of two questions: (i) which elementary step determines the rate of Fischer-Tropsch synthesis, and (ii) which chain growth mechanism is most feasible on cobalt?

Surface science investigations of the Fischer-Tropsch reaction on cobalt

251st National Meeting (2016)

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