Product distribution change in the early stages of carbon monoxide hydrogenation over cobalt magnesium Fischer-Tropsch catalyst.

The catalytic hydrogenation of carbon monoxide, known as the Fischer-Tropsch process, is a technologically important, complex multipath reaction which produces long chain hydrocarbons. In order to access the initial kinetics and the mechanism, we developed a reactor that provides information under non-steady state conditions. We tested a CoMgO catalyst and monitored the initial product formation within 2 s of exposure to CO as well as the time dependence of high molecular weight products (in a 60 s window) and found drastic changes in the product selectivity. The probability for forming branched isomers (C 4 and C 5 ) peaks in the first 25 s, and within that time frame no unsaturated products were detected. The subsequent decline (at ∼35 to 40 s) of branched isomers coincides with the detection of olefins (from C 2 to C 5 ) and the change in carbon coverage at the surface of the catalyst. This indicates a change in the reaction pathway. [ABSTRACT FROM AUTHOR]