Behaviour of palladium and ruthenium catalysts on alumina and silica prepared by gas and liquid phase deposition in cinnamaldehyde hydrogenation

Study was made of the catalytic activity and selectivity of alumina and silica supported palladium and ruthenium catalysts in cinnamaldehyde hydrogenation. Palladium and ruthenium beta-diketonate complexes were introduced onto alumina and silica supports by atomic layer epitaxy (ALE) and by conventional impregnation technique. Palladium catalysts were more active than ruthenium catalysts. ALE-prepared palladium catalysts showed the highest initial activity because of the small metal particle size. However, the reactivity of surface palladium atoms was highest in the large metal particles. ALE-prepared Ru on silica showed good selectivity in cinnamaldehyde hydrogenation; only hydrocinnamaldehyde and 3-phenyl-1-propanol were formed. All other catalysts gave a variety of products. ALE-prepared Ru on alumina had the highest selectivity to cinnamyl alcohol. (C) 2002 Elsevier Science B.V. All rights reserved.