Highly dispersed molybdenum sulfide catalysts prepared from Mo(CO) 6 encaged in a zeolite

Abstract

Molybdenum sulfide catalysts were prepared from Mo(CO) 6 encaged in zeolites and characterized by XPS, IR and NO adsorption. It was demonstrated that highly dispersed sulfides were produced by a reaction between molybdenum subcarbonyl species and H 2S at 373 K. The molybdenum sulfide in a KY or NaY zeolite was found to show a higher catalytic activity per Mo for the hydrodesulfurization (HDS) of thiophene than a molybdenum sulfide catalyst prepared by impregnation procedures. The dependence of the turnover frequency of the HDS on the zeolite and support oxide is explained in terms of the structure of sulfided molybdenum and of the diffusion limitations of the reactant and products. The basic strength of the zeolite is suggested to control the reactivity of the subcarbonyl species toward H 2S and the dispersion degree of the molybdenum sulfide. On the basis of IR, temperature-programmed decomposition and XPS results, the subcarbonyl species, Mo(CO) 3, was shown to form a complex, Mo(CO) 3(SH) ads, by reaction with H 2S at room temperature.