Catalytic C-O bond hydrogenolysis of tetrahydrofuran-dimethanol over metal supported WOx/TiO2 catalysts

摘要

M-Wo(x)/Tio(2) (M = Pt-, Rh-, Pd-, and Ru) catalysts were prepared and studied for tetrahydrofuran-dimethanol (THFDM) hydrogenolysis. All catalysts have a small metal particle size (< 2 nm) but show catalytic activities that differ by two orders of magnitude. From a combination of CO chemisorption and STEM, we conclude that this wide gap in activity is primarily due to overgrowth of WOx/TiO2 covering the metal particle of the less active catalysts. This overgrowth decreases the number of exposed hydrogenation sites in these catalysts, lowering the overall reaction rate. The catalyst with the highest activity (Pt-WOx/TiO2) was studied at various pressures of H-2, with catalytic activity passing through a maximum with increasing pressure. This is likely due to changes in the oxidation state of W delta+ on the catalyst surface, which changes from W6+ to W5+ and W4+ with increasing hydrogen pressure. Moreover, H-2 can strongly adsorb on the catalyst surface and inhibit the activity at high hydrogen pressure. The apparent activation energy of THFDM conversion over Pt-WOx/TiO2 is 47 kJ.mol(-1). Pt-WOx/TiO2 showed a decrease in conversion from 45% to 23% over 46 h on stream in a continuous flow reactor. Catalyst deactivation is likely due to leaching of W. THFDM can be efficiently converted to 1,2,6-hexanetriol (HTO) in the presence of Pt/TiO2 and homogeneous W salts.