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

Nano -alumina-supported transition metal-based mono- (Pd0/γ-Al2O3 or CoIII/γ-Al2O3) and bimetallic catalysts (Pd0CoIII/γ-Al2O3), were prepared by wet impregnation, oxidation and in situ reduction of the palladium. The palladium(II) acetate [PdII 3(OOCCH3)6], cobalt(II) acetate [CoII(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 3MPa of hydrogen at 80 °C. The Pd0/γ-Al2O3 selectively catalyzed the hydrogenation of C=C bond in cinnamaldehyde to formphenylpropanol (100 %). In contrast, catalysis with Pd0CoIII/γ-Al2O3hydrogenated 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/γ-Al2O3 was used.KEYWORDS Bimetallic heterogeneous catalyst, palladium, cobalt, hydrogenation, unsaturated aldehydes