CARBON-MONOXIDE HYDROGENATION ON COBALT FOIL AND ON THIN COBALT FILM MODEL CATALYSTS

Carbon monoxide hydrogenation has been studied on polycrystalline cobalt foils and on thin cobalt films evaporated on gold substrate, using a combination of UHV studies and atmospheric pressure reactions, in the temperature range from 475 to 575 K and at 101 kPa total pressure. On the cobalt foils we have detected C1-C4 hydrocarbons and on the Co/Au surfaces C1-C3 hydrocarbons. The activation energy of methane formation is the same for both types of surfaces (∼86 kJ/mol, but the CO and H2 partial pressure dependencies of the rate are different. For Co/Au surfaces the reaction rate increases with increasing partial pressures of both H2 and CO, but on cobalt foils the CO pressure dependence is negative, as for the supported cobalt catalysts reported in the literature. On cobalt foil the Co hydrogenation reaction proceeds via CO dissociation, followed by subsequent hydrogenation of surface carbon. Whereas in the Co/Au system the rate-limiting step is either formation or dissociation of a CHOH-complex. Auger electron spectroscopy shows no excessive carbon build-up during the reaction on any of the cobalt surfaces below 550 K. © 1993 Academic Press, Inc.