Hydrodesulfurization of oxidized sulfur compounds in benzothiophene, methylbenzothiophene, and dibenzothiophene series over CoOMoO 3Al 2O 3 catalyst

Abstract

Hydrodesulfurization experiments were carried out with a sulfided CoOMoO 3Al 2O 3 catalyst at various elevated pressures (30 to 70 atm) and temperatures (200 to 300 °C) under stirred batch reactor conditions. The reactants were hydrogen and pure sulfur compounds including dibenzothiophene, benzothiophene and its methyl derivatives, and their oxidized products, sulfoxides and sulfones. In the case of dibenzothiophene the reaction is the CS bond scission without any observed hydrogenation of the aromatic ring. For the S-oxidized compounds a deoxygenation takes place first and the sulfide reacts as before. For benzothiophene (BT) and its methyl derivatives there is first a hydrogenation of the C 2–3 thiophenic double bond and then desulfurization leading to ethylbenzene derivatives. For the sulfoxides a deoxygenation takes place first but for the sulfones (BTO 2) as for the sulfide the hydrogenation is operative. Methyl substitution leads to a decrease in the rate of the hydrogenation step in the BT and BTO 2 series. A correlation, related to the overall aromaticity of the system, between the rate constants and the vertical ionization potential of the molecules, suggests that electronic effects may be preponderant.