Preparation, characterization, and catalytic performances of cobalt catalysts supported on KIT-6 silicas in oxidative desulfurization of dibenzothiophene

Abstract

Sulfur-containing compounds in oils are harmful to the ecosystem whose cost-effective removal is still a challenge. In this study, novel heterogeneous catalysts of cobalt supported on KIT-6 mesoporous silicas were prepared and evaluated for oxidative desulfurization (ODS) under ambient conditions using cyclohexanone peroxide (CYHPO) as the oxidant. The model oil was obtained via dissolving DBT in the n-octane. The conventional wet impregnation method was applied for the preparation of the catalysts, and cobalt nitrate was used as the precursor. The catalysts were characterized by XRD, N2-physisorption, FT-IR, TGA, SEM/TEM and XPS. Then their catalytic activities in total oxidation of dibenzothiophene (DBT) were evaluated at various conditions. DBT conversion by this heterogeneous ODS system reached 98.68%. Co/KIT-6 catalysts showed high ODS activity due to Ia3d mesoporous structure resulting in better cobalt dispersion, higher activity of Co, and faster diffusion of reactant and products. The Box-Behnken design showed that the optimum values for the conversion of DBT were 93°C (oxidation temperature), 1.6×10−1g (catalyst amount) and 5.7 (O/S molar ratio), respectively. The inhibitory effect of quinoline on ODS was higher than carbazole and indole, adding quinoline into model oil under same conditions led to a decrease of the conversion of DBT from 98.68% to 65.67% when the concentration of quinoline increased from 160ppm to 4845ppm. Kinetics data correlated well with the pseudo-first-order equation. These data showed that this novel Co/KIT-6 catalysis system has the potential to be applied in ODS from oils.