Hydrogenation of Cinnamaldehyde over an Ionic Cobalt Promoted Alumina-Supported Palladium Catalyst

Nano -alumina-supported transition metal-based mono- (Pd0/-Al2O3 or Co III/-Al2O3) and bimetallic catalysts (Pd0CoIII/-Al2O3), were prepared by wet impregnation, oxidation and in situ reduction of the palladium. The palladium(II) acetate [PdII3(OOCCH3)6], cobalt(II) acetate [Co II(OOCCH3)2]·4H2O and palladium, cobalt bridging tetraacetate [PdIICoII(OOCCH3)4]·H2O·2CH3COOH, were used as catalyst precursors to prepare a 7.4 % mol catalyst/support loading. The oxidation states of these activated catalysts were studied by XPS. These catalysts were evaluated for hydrogenation of cinnamaldehyde in a biphasic reaction under 3 MPa of hydrogen at 80 °C. The Pd0/-Al2O3 selectively catalyzed the hydrogenation of C=C bond in cinnamaldehyde to form phenylpropanol (100 %). In contrast, catalysis with Pd0CoIII/-Al2O3 hydrogenated both C=C and C=O bonds consecutively, forming 65 % phenylpropanal and 35 % phenylpropanol with TOF = 47.2 h–1. No reaction occurred when CoIII/-Al2O3 was used