Benzaldehyde hydrogenation over supported nickel catalysts

The hydrogenation of benzaldehyde over nickel catalysts supported on Al2O3, SiO2, TiO2 and CeO2 was studied at atmospheric pressure in the range temperature of 70-140 degrees C under H-2 flow. They were characterized by their BET surface area, XRD spectra, reducibility properties under H,. The obtained products were benzylalcohol, toluene, benzene with yields depending on the nature of the support and reaction temperature. Methylcyclohexane was also produced, mainly at low temperature and on Ni/alpha-Al2O3 as catalyst. The products of benzaldehyde hydrogenation (benzylalcohol. toluene and methylcyclohexane) and hydrogenolysis (benzene) were preferentially formed at low/middle and high reaction temperature respectively. The observed selectivities also suggested the existence of bifunctional sites for both the hydrogenation and hydrogenolysis reactions. These sites were believed to be involved as acidic/cationic centers for the adsorption of the oxygenate molecules and metal center for the hydrogenation or hydrogenolysis step. (c) 2006 Elsevier B.V. All rights reserved.