Preparation of Alumina-supported Cobalt–molybdenum Catalysts by Sol-gel Method and Hydrodesulfurization Activities

Abstract

Al2O3-supported Co and Mo catalysts were prepared by the sol-gel method, in which Co and/or Mo species were added at the hydrolysis of Al tri-s-butoxide. XRD patterns, N2 adsorption and desorption, amounts of NO adsorption and NO species by FT-IR were measured to characterize the catalysts. Catalysts with active components Co and Mo separately supported by the sol-gel method had higher activity for hydrodesulfurization of dibenzothiophene. Mo-Co/Al2O3, in which Mo species was supported on Co/Al2O3 by the sol-gel method, showed the highest activities at lower temperature, indicating that the Co species was effectively dispersed on Al2O3 during the preparation of Co/Al2O3. Catalysts in which Co and Mo species were simultaneously supported had lower activity, indicating that both Co and Mo species were dispersed and reduced interaction between Co and Mo. Co-Mo/sol-gelAl2O3, with the Co species supported on Mo/sol-gelAl2O3, showed the highest activity among sol-gelAl2O3 supported CoMo catalysts, indicating that the Mo species was effectively dispersed during the preparation of Mo/sol-gelAl2O3. Biphenyl was selectively obtained. NO adsorption measurement showed that the amount of NO adsorbed was almost same for Mo-Co/Al2O3 sulfided once or twice. In contrast, sol-gelCoMo/Al2O3, with the Co and Mo added simultaneously by the sol-gel method, showed significant decrease in NO adsorption after second sulfiding, which would be related to the lower stability of sol-gelCoMo/Al2O3 prepared by the sol-gel method. Al2O3-supported Co-Mo catalysts prepared using the sol-gel method had relatively high surface areas (282-544 m2/g) and relatively smaller pore sizes (3.7-6.3 nm).