Abstract
In the hydrodesulfurization (HDS) of dibenzothiophene (DBT) and 4, 6-dimethyldibenzothiophene (4, 6-DMDBT), the effects of H2S on catalytic activity and selectivity were investigated under deep desulfurization conditions (sulfur concentration<0.05wt%) using a commercial Co-Mo/Al2O3 catalyst. The conversions of DBTs decreased with increasing partial pressure of H2S. The formations of both biphenyls (BPs) and cyclohexylbenzenes (CHBs) were inhibited by H2S, but the former was inhibited more significantly. The HDS reactions of DBTs were described using Langmuir-Hinshelwood rate equation. Activation energies of formation of BP and 3, 3'-DMBP were 24±2 and 38±2kcal/mol, respectively. Heats of adsorption of DBT, 4, 6-DMDBT, and H2S for the formations of BPs were 10±2, 17±2, and 19±2kcal/mol, respectively; however, H2S adsorbed more strongly on the catalyst than on DBT and 4, 6-DMDBT, and inhibited the HDS of DBT and 4, 6-DMDBT.
