Influence of the support on the catalytic properties of bimetallic Ru-Cu samples

Propane hydrogenolysis has been studied on a series of Ru-Cu catalysts supported on SiO2, Al2O3 and MgO. On SiO2 the hydrogenolysis activity of Ru decreased continuously on addition of copper over the entire range of composition. On A12O3 and MgO however, it was found that on increasing the amount of Cu the catalytic activity initially decreases, reaching a minimum at intermediate Ru/Cu ratios, and then increases at higher Cu contents. For each support, the less active samples were also found to be the most selective towards ethane formation. The lower catalytic activity and the higher selectivity observed on the bimetallic samples has been attributed to a Ru-Cu interaction, the degree of which depends on the nature of the support. It is suggested that the relative amount of bimetallic aggregates present on the reduced samples is strongly dependent either on the total surface area of the support, which influences the rate of formation and growth of the metallic particles, and/or on the acid-base characteristic of the oxide, which would determine the degree of hydrolysis of the catalyst precursor.