Kinetic study of the hydrogen sulfide effect in the conversion of thiophene on supported CoMo catalysts

The hydrodesulfurization of thiophene on a commercial CoMo/alumina catalyst was studied in a Berty type CSTR reactor at 350°C, with partial pressures of hydrogen sulfide in the range of 0.2 to 5.5 bar. A kinetic model with interconversion of active sites is superior to models based on a fixed number of active sites. The proposed mechanism for the interconversion of active sites predicts that the hydrogenation and hydrogenolysis activities of a HDS catalyst can be substantially varied by hydrogen sulfide. The model also explains the controversial hydrogen sulfide effects observed in various types of reactions on CoMo catalysts.