Catalytic hydrodesulfurization of dibenzothiophene through partial oxidation and a water-gas shift reaction in supercritical water

We conducted a comparative study of catalytic hydrodesulfurization of dibenzothiophene (DBT) with NiMo/Al₂O₃ at 673 K and 30 MPa, in various atmospheres (H₂-SCW, CO-SCW, CO₂-H₂-SCW, and HCOOH-SCW), using a tube bomb reactor. Higher conversion of DBT was obtained in CO-SCW, CO₂-H₂-SCW, and HCOOH-SCW than in H₂-SCW. These results clearly indicate that a water-gas shift reaction in supercritical water (SCW) produces species which can hydrogenate DBT more effectively than H₂ gas. We also conducted another experiment for the partial oxidation of a DBT-hexylbenzene mixture in SCW. Even in the presence of oxygen, effective hydrogenation of DBT took place. This result is probably because CO forms through the partial oxidation of hexylbenzene and converts to the hydrogenating species through a water-gas shift reaction. We think the catalytic desulfurization of heavy oils in SCW will be a promising new technology, since even by introducing oxygen or air instead of hydrogen, an excellent hydrogenating atmosphere can be supplied.