Synthesis of bimetallic SnPt-nanoparticle catalysts for chemoselective hydrogenation of crotonaldehyde: Relationship between SnxPty alloy phase and catalytic performance

Abstract

Bimetallic SnPt-nanoparticle (SnPt-NP) catalysts with several types of SnxPty alloy structures were prepared using a polyalcohol reduction process; the catalytic behavior of each SnxPty alloy phase toward the selective hydrogenation of unsaturated aldehydes to the corresponding unsaturated alcohols was elucidated. Atomic absorption spectroscopy (AAS) and transmission electron microscopy (TEM) indicate that SnPt-NP catalysts with various Sn/Pt atomic ratios can be successfully prepared by a polyalcohol reduction process using Pt(acac)2 and Sn(AcO)2 as the metal precursors. X-ray diffraction (XRD) results reveal that the Sn1Pt3, Sn1Pt1, and Sn2Pt1 alloy phases are formed through control of the Sn/Pt atomic ratio of the starting mixture during preparation. The Sn1Pt3 alloy phase enhanced the hydrogenation of both the CC and CO bonds during the selective hydrogenation of crotonaldehyde. When only Sn1Pt1 alloy phases (Sn/Pt = 1.40), accompanying with separated Sn phase, were formed in the SnPt-NP catalysts, the highest unsaturated alcohol (UOL) selectivity (71.5% at 37.6% conversion) was observed. The formation of the Sn2Pt1 alloy phase led to decreased UOL selectivity. We suggest that the Sn1Pt1 alloy phase is an effective bimetallic SnPt hydrogenation catalyst for the selective formation of unsaturated alcohols.