Structure-activity relation and ethane formation in the hydrogenolysis of methyl acetate on silicasupported copper catalysts

Abstract

The activity and selectivity of silica-supported copper catalysts in the hydrogenolysis of methyl acetate were studied in relation to the structure of the active phase. The activity was found independent of the copper loading, when the weight of copper in the reactor was kept constant. Copper catalysts were prepared by homogeneous precipitation. In the range of reduction temperatures between 543 K and 743 K, the activity was constant, in spite of considerably different copper metal surface areas. The absence of a correlation between activity and copper surface area is assigned to the formation of highly dispersed copper not active in methyl acetate hydrogenolysis. In contrast to the equal activity, catalysts of low copper loading produced more ethane than the higher loaded catalysts, based on the weight of copper. A remarkable parallel between the amount of ammonia chemisorbed on the reduced catalyst and the ethane selectivity suggests that a dehydration reaction to ethene on acid sites located at the silica support, followed by hydrogenation on the copper metal phase, is responsible for the formation of ethane.