W-INCORPORATED COMO GAMMA-AL2O3 HYDRODESULFURIZATION CATALYST .1. CATALYTIC ACTIVITIES/

The promotional effect of tungsten in the CoMo/gamma-Al2O3 catalyst wa s studied for series of W-incorporated CoMo/gamma-Al2O3 catalysts with different content of tungsten. Two series of the catalysts were prepa red by changing the impregnation order of cobalt and tungsten onto a b ase Mo/gamma-Al2O3 catalyst. Impregnation of tungsten was achieved und er the condition that the pH of an aqueous impregnating solution of W anion was controlled to 9.5. The hydrodesulfurization (HDS) and hydrog enation (HYD) activities of the sulfided catalysts were evaluated by t hiophene HDS and ethylene HYD reactions at atmospheric pressure, respe ctively. Low-temperature O-2 chemisorption at 195 K was conducted for the sulfided catalysts in order to determine the W-incorporation effec ts on the surface concentration of coordinatively unsaturated sites re lated to the catalytic activities. The dependence of catalytic activit ies on tungsten content showed initially an increase and subsequent de crease with increasing tungsten content. The maximum promotion of HDS and HYD activities occurred at a low content of tungsten corresponding to 0.025 in W/(W + Mo) atomic ratio regardless of the impregnation or der of tungsten and cobalt. Oxygen uptake correlated well with catalyt ic activities. In general, the catalysts prepared by impregnating tung sten onto the CoMo/gamma-Al2O3 showed higher activities than the catal ysts prepared by impregnating tungsten onto Mo/gamma-Al2O3 prior to im pregnation of cobalt. (C) Academic Press, Inc.