ACTIVITY AND SELECTIVITY OF PTNI/TIO2 CATALYSTS FOR HYDROGENATION OF CROTONALDEHYDE

The hydrogenation of crotonaldehyde over a series of titania supported PtNi catalysts was investipted. Pt/TiO2 had the highest activity to hydrogenate the C=O bond of crotonaldehyde. With the addition of Ni to Pt the activity for carbonyl group hydrogenation decreased, while that for the C=C bond hydrogenation increased. Two different types of sites were established to be active for C=O bond hydrogenation, located at (i) the Pt-TiO2 interface and (ii) the PtNi bimetallic phase. For the Pt-TiO2 interface the presence of accessible Ti(x+) cations in close distance to Pt and for the PtNi phase a slightly positively charged Ni on the surface of these alloy particles were concluded to be responsible for the enhanced selectivity to crotylalcohol. The hydrogenation of the C=C bond occurs mainly on the ''clean'' metal surfaces of Ni and Pt.