LIQUID-PHASE HYDROGENATION OF CROTONALDEHYDE OVER PT SIO2 CATALYSTS/

The dependence of the catalytic properties of Pt/SiO2 catalysts for th e hydrogenation of crotonaldehyde on the hydrogen pressure, the reacti on temperature, the nature of the solvent and the presence of several additives were investigated. Strong deactivation of the catalysts main ly caused by decarbonylation of crotonaldehyde and irreversible adsorp tion of CO was observed. The initial activity of the deactivated catal ysts is regained by oxidation of the adsorbed CO to CO2 by purging wit h air. The selectivity to crotylalcohol increased with increasing numb er of turnovers per metal site. This is explained with preferential bl ocking of the nonselective sites on the metal crystallites by CO and b y a slow surface modification of the aging catalyst with organic depos its. The overall rate and the selectivity to the saturated aldehyde ar e markedly enhanced by an increase in hydrogen pressure and by a decre ase in reaction temperature. The addition of modifiers such as potassi um acetate, triphenylphosphine and thiophene had only little influence on the activity and the selectivity of the catalysts. (C) 1997 Elsevi er Science B.V.