Mechanism of Carbon Monoxide Dissociation on a Cobalt Fischer–Tropsch Catalyst

The way in which the triple bond in CO dissociates, a key reaction step in the Fischer–Tropsch (FT) reaction, is a subject of intense debate. Direct CO dissociation on a Co catalyst was probed by (12)C(16)O/(13)C(18)O scrambling in the absence and presence of H(2). The initial scrambling rate without H(2) was significantly higher than the rate of CO consumption under CO hydrogenation conditions, which indicated that the surface contained sites sufficiently reactive to dissociate CO without the assistance of H atoms. Only a small fraction of the surface was involved in CO scrambling. The minor influence of CO scrambling and CO residence time on the partial pressure of H(2) showed that CO dissociation was not affected by the presence of H(2). The positive H(2) reaction order was correlated to the fact that the hydrogenation of adsorbed C and O atoms was slower than CO dissociation. Temperature‐programmed in situ IR spectroscopy underpinned the conclusion that CO dissociation does not require H atoms.