Hydrogenations of two model compounds (acetone, propanal) have been st
udied with Pt/SiO2 catalysts, promoter-free or promoted by Ga, Ge or F
e compounds. It appeared that hydrogenation of acetone is faster than
that of propanal, but the promotion effect is more pronounced with the
aldehyde than with the ketone. This is in compliance with earlier wor
k, A tentative explanation of the observed phenomena is suggested, bas
ed on the theoretical analysis by Delbecq and Sautet.