Kinetics of hydrodesulfurization of dibenzothiophene catalyzed by sulfided Co-Mo/MCM-41

The kinetics of dibenzothiophene (DBT) hydrodesulfurization catalyzed by MCM-41-supported Co-Mo sulfides was investigated at temperatures of 280-340 degreesC and 5.0 MPa. Both the Langmuir-Hinshelwood (L-H) model and pseudo-first-order model were used to fit the experimental data in an integral operation. It was found that the L-H rate expression was not applicable in the study whereas the pseudo-first-order model fitted very well with the experimental data. Moreover, it is indicated that the L-H expression becomes first-order in DBT concentration if the adsorption of DBT is negligible and DBT concentration is low, as in a typical commercial hydrotreating process. It is shown that the rate constant of the hydrogenolysis route was influenced more greatly by the atomic ratio of Co to Mo than that of the hydrogenation route, implying that hydrogenolysis and hydrogenation might take place on separate active sites and the introduction of Co to the Mo matrix might enhance mainly the hydrogenolysis route.