HYDROGENATION OF CITRAL AND CINNAMALDEHYDE OVER BIMETALLIC RU-ME AL2O3 CATALYSTS/

Hydrogenations of citral and cinnamaldehyde have been investigated ove r Ru-Me/Al2O3 (Me = Ge, Sn, Pb). Two series of catalysts have been pre pared by using the controlled surface reaction (CSR) technique (RuEC s eries) and the more conventional co-impregnation method (RuNI series). Addition of Ge increases the catalytic activity on the RuEC series wh ereas no modifications are found on the samples prepared by co-impregn ation. The selectivity to unsaturated alcohols is not influenced by th e presence of Ge. Addition of tin increases both the activity and the selectivity regardless of the preparation method. The presence of lead does not modify the selectivity and a slight decrease in the catalyti c activity is observed on the sample of the RuNI series. On the basis of the characterization data available on the investigated catalysts, it is suggested that Ru and Ge interacts when the samples are obtained through the CSR technique, Such an interaction increases the catalyti c activity likely through a decrease of the strength of adsorption of one of the reaction components. The positive effect of tin on the cata lytic activity and selectivity is discussed.