Unique hydrogenation activity of supported tin catalyst: Selective hydrogenation catalyst for unsaturated aldehydes

Abstract

Selective hydrogenation of unsaturated aldehydes, crotonaldehyde (CH 3CHCHCHO) and cinnamaldehyde (C 6H 5CHCHCHO), has been studied over SiO 2-supported monometallic Sn and bimetallic RhSn catalysts in the liquid phase. Over a silica-supported monometallic Rh catalyst, Rh SiO 2 , no unsaturated alcohol (crotyl alcohol or cinnamyl alcohol) was formed, whereas considerable amounts of the corresponding saturated aldehyde and saturated alcohol were obtained. The selectivity to the unsaturated alcohol was improved over the RhSn bimetallic catalyst. The selectivity to the corresponding unsaturated alcohol attained ca. 65% over the RhSn bimetallic catalysts. On the other hand, The supported Sn catalyst showed markedly high selectivity to the unsaturated alcohols. The selectivity of the Sn SiO 2 , attained 95% to crotyl alcohol and 100% to cinnamyl alcohol, respectively. Although the conversion of each unsaturated aldehyde over RhSn SiO 2 catalysts was greater than that over Sn SiO 2 catalysts, the selectivity of Sn SiO 2 catalysts to the corresponding unsaturated alcohols was superior to that over RhSn SiO 2 . The selectivity of Sn SiO 2 was also compared with that of RhSn SiO 2 at a similar conversion of the unsaturated aldehydes. The selectivity of Sn SiO 2 was significantly greater than that of the RhSn bimetallic catalyst. These results indicate that the high selectivity over Sn SiO 2 was ascribed not to low conversion but to intrinsic selectivity of the Sn catalyst.