Hydrodesulfurization of 4-Methyldibenzothiophene and 4,6-Dimethyldibenzothiophene on a CoMo/Al2O3 Catalyst: Reaction Network and Kinetics

Abstract

The hydrodesulfurization of 4-methyldibenzothiophene and 4,6-dimethyldibenzothiophene on a commercial CoMo/Al2O3 catalyst was studied in a multiphase flow reactor in the presence of dibenzothiophene. Hougen−Watson rate equations for the hydrogenolysis of 4-methyldibenzothiophene into 3-methylbiphenyl and H2S and for the hydrogenation of 4-methyldibenzothiophene into partially hydrogenated intermediates were developed. In an identical manner Hougen−Watson kinetics were determined for the hydrogenolysis of 4,6-dimethyldibenzothiophene into 3,3‘-dimethylbiphenyl and H2S and for the hydrogenation of 4,6-dimethyldibenzothiophene into dimethyltetra- and dimethylhexahydrodibenzothiophene. Two different types of active sites exist on the catalyst surface: σ sites for hydrogenolysis and τ sites for hydrogenation reactions. The surface reaction between adsorbed reactants and two competitively adsorbed hydrogen atoms was the rate-determining step for both types of reaction.