Catalytic desulfurization of a model sulfur-containing compound benzothiophene (BT) through partial oxidation in supercritical water (SCW) was investigated in a bomb reactorat 623-723 K and 30-40MPa over sulfided CoMo/gamma-Al2O3. Vacuum residuum was used to confirm the desulfurization rate and efficiency, and the desulfurization mechanism of vacuum residuum was determined by the pyrolysis temperature (T-R) of the vacuum residuum (VR). For T > T-R, obvious reduction of sulfides up to 67% was obtained. The thermodynamic equilibrium of in situ H-2 generation was a controlling factor of the desulfurization pathway. (c) 2004 Elsevier B.V. All rights reserved.