Gas phase transfer hydrogenation of α, β- unsaturated carbonyl compounds into saturated carbonyl compounds over supported Cu catalysts

Abstract

This work aims to produce hydrocinnamaldehyde via selective CC bond hydrogenation of cinnamaldehyde via transfer hydrogenation catalyzed by supported Cu catalysts. The catalytic activity and characterization results demonstrated that conversion of cinnamaldehyde and selectivity to hydrocinnamaldehyde is an integrated result of active Cu metal surface area and nature of support material. In the case of Cu/SiO2 catalysts, the rate of formation of hydrocinnamaldehyde was linearly dependent on the active Cu metal surface area. A maximum rate of formation of hydrocinnamaldehyde 167.82 μmol.g−1.s-1 was obtained at an active Cu metal surface area of 6.1 m2.gcat-1 over 20 wt. % Cu/SiO2 catalyst. While in the case of other supported Cu catalysts (Cu/MgO, Cu/ZrO2 and Cu/γ-Al2O3) along with the active Cu metal surface area, the surface acidity and basicity governed the selectivity of hydrocinnamaldehyde. The rate of formation of hydrocinnamaldehyde followed the trend Cu/SiO2 >Cu/Al2O3 >Cu/MgO > Cu/ZrO2. Unlike Cu/SiO2 catalyst, the competitive adsorption of CC and CO bonds over these (Al2O3, MgO and ZrO2) supported Cu catalysts altered the selectivity of hydrocinnamaldehyde. Cu/SiO2 catalyst was superior in selective CC hydrogenation of α, β-unsaturated carbonyl compounds via transfer hydrogenation. Cyclohexenone, isophorone and crotonaldehyde were selectively converted into their saturated carbonyl compounds.