Effects of SnxPty Alloy Structures on the Performance of SnPt Catalysts for the Selective Hydrogenation of Unsaturated Aldehydes to Unsaturated Alcohols

The development of next-generation heterogeneous catalysts for the chemoselective hydrogenation of unsaturated aldehydes to unsaturated alcohols requires extensive structural understanding of active catalyst sites. In the case of SnPt catalysts, the presence of metallic Sn and the formation of Sn-Pt alloys are believed to be key factors strongly affecting the selectivity of unsaturated alcohol formation. This review describes the relationship between the catalytic crotonaldehyde (CH3-CH = CH-CHO) hydrogenation performance of supported and non-supported SnPt catalysts and the structure of the component SnxPty alloys, which reveal that at the same Sn/Pt atomic ratio, the composition of the produced SnxPty alloys depends on the preparation method. The Sn1Pt3, Sn1Pt1, and Sn2Pt1 phases identified in SnPt catalysts exhibited higher crotyl alcohol (CH3-CH = CH-CH2OH) formation selectivity than the monometallic Pt phase. Furthermore, the Sn1Pt1 and Sn2Pt1 phases showed lower crotonaldehyde conversion than the Pt phase. Formation of Sn oxides over the supported SnPt catalysts was confirmed with excess amount of Sn. The crotyl alcohol selectivity increased with the transition from Sn1Pt3 to Sn1Pt1, then decrease with the further transition to the more Sn-rich Sn2Pt1 phase. Thus, the Sn1Pt1 alloy phase was concluded to be the most effective bimetallic SnPt structure for the selective formation of crotyl alcohol.