EFFECT OF CATALYST PRETREATMENT ON THE OXIDATION OF CARBON-MONOXIDE OVER COPRECIPITATED GOLD CATALYSTS

Au/Co3O4, Au/Fe2O3 and Au/CuO and the corresponding silver containing catalysts were prepared by coprecipitation and subjected to various heat and oxygen pretreatments prior to being used to promote carbon monoxide oxidations. The most active catalysts were those which were heated in oxygen before use. The relative activities of these catalysts depended on the degree of heating and oxygen exposure before use. Reduction of the gold containing precipitates with formaldehyde gave species with markedly diminished activities. The unreduced gold containing catalysts were more active than the silver species. These catalysts were also subjected to alternate pulses of O2, CO and O2 at varying temperatures to determine the type of interaction taking place on the catalyst surface. These data indicate that carbon monoxide oxidation takes place primarily by the interaction of carbon monoxide with adsorbed oxygen and to a lesser extent by the reverse.