Effect of the Support (Silica vs Niobia) and the Pressure (Atmospheric vs High Pressure) on the Catalytic Performance of Pd Based Catalysts for the Hydrodeoxygenation of m-Cresol

This work investigated the effect of reaction pressure (1 bar and 30 bar of total pressure) in the hydrodeoxygenation (HDO) of m-cresol over both catalysts: Pd/SiO2 and Pd/Nb2O5. The results revealed that the catalytic properties of the solids strongly depended on the type of support (silica vs niobia) and reaction conditions (atmospheric vs high pressure). Irrespective the catalyst, an increase of the pressure significantly rose the total reaction rate. The product distribution over Pd/SiO2 catalyst was practically no affected by the reaction pressure, 3-methylcyclohexanone being the main product at atmospheric and high pressure. On the contrary, Pd/Nb2O5 showed significantly higher selectivity toward deoxygenated products, toluene or 3-methylcyclohexane depending the pressure used, the former favored under atmospheric pressure and the latter under 30 bar. This was mainly attributed to the ability of niobia in activating the C-O bond due to its superior oxophilicity. Reaction pressure also affect the stability of catalyst. Pd/Nb2O5 deactivated during 6 h of TOS under atmospheric pressure (loss of 40% in m-cresol conversion) while it remained quite stable at high pressure. [GRAPHICS] .