Characterization of Sn–Pt/SiO2 Catalysts Used in Selective Hydrogenation of Crotonaldehyde by Mössbauer Spectroscopy

Upon treatment of Sn–Pt/SiO2 catalysts with crotonaldehyde (CA) at 80°C formation of Sn4+ species was evidenced by Mössbauer spectroscopy. These results have confirmed the earlier suggestion that the “reaction induced selectivity improvement” observed in the hydrogenation of CA to crotylalcohol 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 suggested that in our Sn–Pt/SiO2 catalysts the formed Sn4+ species are responsible 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 hindered.