The promotion effect of Cu on the Pd/C catalyst in the chemoselective hydrogenation of unsaturated carbonyl compounds

Abstract

Highly efficient and selective hydrogenation of α,β-unsaturated carbonyl compounds to unsaturated alcohol using bimetallic palladium-copper supported on carbon (denoted as Pd-Cu(3.0)/C; 3.0 is Pd/Cu molar ratio) catalyst is demonstrated. Pd-Cu(3.0)/C catalyst was prepared via a simple hydrothermal route under air atmosphere at 150 °C for 24 h followed by reduction with hydrogen at 400 °C for 1.5 h. The chemoselective hydrogenation of typical α,β-unsaturated carbonyl ketone (2-cyclohexene-1-one) and aldehyde (trans-2-hexenaldehyde), and chemoselective hydrogenation of FFald and (E)-non-3-en-2-one mixture demonstrated high productivity, leading to high selectivity of unsaturated alcohols. The presence of bimetallic Pd-Cu alloy phase with relatively high H2 uptakes was observed, enabling to preferentially hydrogenate C=O rather than to C=C bonds under mild reaction conditions. Pd-Cu(3.0)/C catalyst was found to stable and reusable for at least four reaction runs and the activity and selectivity of the catalyst can be restored to the original after rejuvenation with H2 at 400 °C for 1.5 h.