Enhanced selective deoxygenation of m-cresol to toluene on Ni/SiO2 catalysts derived from nickel phyllosilicate

Abstract

The nickel phyllosilicate derived Ni/SiO2 catalysts (PS-Ni) were prepared and tested for vapor phase hydrodeoxygenation of m-cresol at 250–300 °C and 1 atm H2. Calcination at 400 °C followed by reduction at 500 °C of the nickel phyllosilicate resulted in uniformly dispersed Ni particles with an average size of 2–3 nm on the support. These particles are much smaller than those in a 20 wt.% Ni/SiO2 catalyst prepared by a conventional impregnation method (IMP-Ni) with the same Ni loadings (25.9 nm). On PS-Ni, the yield of hydrogenation products (methylcyclohexanone and methylcyclohexanol) decreases while that of deoxygenation product (toluene) increases, as compared to those on IMP-Ni at the same m-cresol conversion. At 300 °C, PS-Ni results in increased overall intrinsic reaction rate and turnover frequency for toluene formation by 8 and 10 times, respectively, relative to IMP-Ni. This improved selective deoxygenation of m-cresol to toluene is mainly due to the much smaller Ni particle size in PS-Ni. Furthermore, CC hydrogenolysis to CH4 is greatly inhibited on PS-20Ni. Stability test showed that PS-20Ni deactivated with time on stream, and the strong adsorption of oxygen-containing compounds on the acid sites in PS-20Ni is speculated to be the major reason of deactivation.