Fundamental comparison studies on hydrodesulfurization of dibenzothiophenes over CoMo-based carbon and alumina catalysts Original Research Article

Hydrodesulfurization (HDS) reactions of dibenzothiophene (DBT) and 4,6-dimethyldibenzothiophene (4,6-DMDBT) over synthesized CoMo-based carbon catalysts and CoMo/Al2O3 commercial catalyst were investigated using a sampling micro-autoclave reactor at 300–380°C and 2.9 MPa hydrogen initial pressure. CoMo-based carbon catalysts showed higher activity than CoMo/Al2O3commercial catalyst. The HDS selectivity of DBT in terms of direct de-sulfurization and hydrogenation routes was found to be almost independent of the temperature, whereas a dramatic change with 4,6-DMDBT was observed on both catalysts. The presence of 10 wt% naphthalene during the HDS of dibenzothiophene was found to inhibit both direct de-sulfurization and hydrogenation routes, while self-produced H2S inhibited only the direct de-sulfurization. Excess slightly reduced the rate of hydrogenation reaction as well. The trend of inhibition by naphthalene was similar for both CoMo-based carbon and CoMo/Al2O3 catalysts. However, much more inhibition by H2S was observed with carbon support. Based on the kinetic analysis of inhibition, active sites on CoMoS for de-sulfurization and hydrogenation are discussed.