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Time-Resolved (2 s) Study of the Initial Steps of the Catalytic Hydrogenation of CO: From Branched Isomers to Unsaturated Molecules

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journal contribution
posted on 20.11.2014, 00:00 by Gérôme Melaet, Walter T. Ralston, Wen-Chi Liu, Gabor A. Somorjai
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 nonsteady 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 isomer (C4 and C5) 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 C2 to C5), indicating a change in the reaction path.