HYDROGENATION OF ALPHA, BETA-UNSATURATED CARBONYLS - ACROLEIN HYDROGENATION ON GROUP-VIII METAL-CATALYSTS

Hydrogenation of acrolein was studied in the vapor phase on various supported Group VIII metals. The distribution of products changes rapidly with time on stream. When supported on alumina, silica, titania, zirconia or graphite, Co, Ni and Ru based catalysts show good initial selectivity to allyl alcohol, while Pt - with a higher activity - is less selective, as is Ir. The other products formed in major quantities were propanal and acetone, while the activities for n-propanol and light compounds are short lived. It is proposed that acetone is formed through a 1,4-diadsorbed intermediate on some specific electron-deficient sites which could be situated at the interface between the metal particles and the support. Acetone is not formed when graphite or zirconia is used as the support. From the study of the influence of the size of Ru particles supported on alumina on the hydrogenation of acrolein, it turns out that the highly dispersed Ru/Al2O3 catalyst is the least selective to allyl alcohol. In other respects, the zirconia-supported ruthenium catalyst exhibits the highest selectivity to allyl alcohol, possibly owing to some alloying occurring between ruthenium and zirconium.