Vapor phase hydrodeoxygenation and hydrogenation of m-cresol on silica supported Ni, Pd and Pt catalysts

Hydrodeoxygenation of in cresol (a model compound of lignin derived phenolics in bio-oil) has been studied on silica supported Ni, Pd and PL catalysis at 250 degrees C and atmospheric pressure. Hydrogenation (to 3-methylcyclohexanone and 3-methylcyclohexanol) and hydrodeoxygenation (to toluene) are the primary reactions over all catalysis. The intrinsic hydrogenation activity follows the order of Ni < Pd < PL, and the deoxygenation activity follows the order of Ni Pd PL. The oxygen removal is mainly through a direct. deoxygenation (DDO) route. The hydrogenation-deoxygenation (HYD) route is not important due to the lack of acidic sites to catalyze dehydration and a rather low hydrogenolysis activity of the C-OH bond of 3-methylcyclohexanol. Al high conversions, the initial hydrogenation products are reversely dehydrogenated to m-cresol, making the deoxygenation to toluene and its subsequent hydrogenation to methylcyclohexane the major pathway. In general, increasing reaction temperature suppresses the hydrogenation reaction but promotes the hydrodeoxygenation as well as C-C bond hydrogenolysis. On Pd and Pt, increasing temperature improves deoxygenation to toluene over the C-C bond hydrogenolysis. In contrast, higher temperature favors the successive C-C hydrogenolysis to produce the low value methane on Ni. (C) 2015 Elsevier Ltd. All rights reserved.