Characterization of Sn-Pt/SiO2 catalysts used in selective hydrogenation of crotonaldehyde by Mossbauer spectroscopy

Upon treatment of Sn-Pt/SiO2 catalysts with crotonaldehyde (CA) at 80 degre es C formation of Sn4+ species was evidenced by Mossbauer spectroscopy. The se results have confirmed the earlier suggestion that the "reaction induced selectivity improvement" observed in the hydrogenation of CA to crotylalco hol over Sn-Pt/SiO2 catalysts is related to the formation and stabilization of ionic forms of tin in the atomic closeness to the platinum. It is sugge sted that in our Sn-Pt/SiO2 catalysts the formed Sn4+ species are responsib le for the activation of the carbonyl group, while further hydrogenation of crotylalcohol to n-butanol is prevented by the presence of a tin enriched Sn-Pt alloy phase on which the readsorption of crotylalcohol is strongly hi ndered. (C) 2000 Academic Press.