Elementary steps in Fischer–Tropsch synthesis: CO bond scission, CO oxidation and surface carbiding on Co(0001)

Abstract

Dissociation of CO on a Co(0001) surface is explored in the context of Fischer–Tropsch synthesis on cobalt catalysts. Experiments show that CO dissociation can occur on defect sites around 330K, with an estimated barrier between 90 and 104kJmol−1. Despite the ease of CO dissociation on defect sites, extensive carbon deposition onto the cobalt surface up to 0.33ML requires a combination of high surface temperature and a relatively high CO pressure. Experimental data on the CO oxidation reaction indicate a high reaction barrier for the CO+O reaction, and it is argued that, due to the rather strong Co–O bond, (i) oxygen removal is the rate-limiting step during surface carbidization and (ii) in the context of Fischer–Tropsch synthesis, removal of surface oxygen rather than CO bond scission might be limiting the overall reaction rate.