gamma-Alumina-supported beta-Mo2N0.78 catalyst was synthesized by the temperature-programmed nitriding reaction and tested to determine its catalytic activity and selectivity during the hydrodesulfudzation (HDS) of dibenzothiophene. The results indicated that the conversion increases with reaction temperature and hydrogen pressure. And increasing the hydrogen pressure results in more hydrogenation, but increasing reaction temperature can improve the two parallel pathways of direct desulfurization and hydrogenation desulfurization at same degree. Sulfur can replace the surface oxygen of passivated nitride in the HDS reaction although the bulk structure is preserved. (C) 2004 Elsevier B.V. All rights reserved.