Combined Experimental and Theoretical Investigation on the Selectivities of Ag, Au, and Pt Catalysts for Hydrogenation of Crotonaldehyde

Abstract

A parallel study on silver, gold, and platinum catalysts with inert silica support is conducted both experimentally and theoretically for the liquid-phase hydrogenation of crotonaldehyde (Me−CH═CH−CH═O). We find that the silver catalyst exhibits a uniquely high selectivity toward C═O hydrogenation and the selectivity remains constant even at the conversion close to 100%. The gold catalyst, however, shows only a moderate selectivity whereas the platinum catalyst has a rather poor selectivity. Such variation in selectivity is interpreted in terms of the varied adsorption geometries of the crotonaldehyde on different metals. According to our density functional calculations of the chemisorptions of crotonaldehyde on selected M19 (M = Ag, Au, and Pt) model clusters and M(111) surface, the most favored adsorption mode for silver is the C═O oxygen atom being σ-bonded on low-coordinated silver atoms, which results in activation of the C═O bond. In contrast, so-called η4 and di-σC═C modes are preferred on Pt surfa...