SBA-15 and Al-SBA-15 of varying Si/Al ratios (10-40) were synthesized by well-known procedures. Characterization using XRD, pore size distribution, Al-27 NMR confirmed that hexagonal mesoporous structure is obtained and majority of Al is in tetrahedral positions. Mo, CoMo and NiMo catalysts prepared using these supports were examined by XRD, oxygen uptakes in sulfided state and temperature programmed reduction (TPR). The catalysts were tested for hydrodesulfurization (HDS) of thiophene and hydrogenation of cyclohexene. Systematic variation of oxygen chemisorption and catalytic activities were observed as a function of Si/Al ratio. The systematic variation of activities, oxygen chemisorption and TPR hydrogen consumption of Mo indicated that the molybdenum dispersion and anion vacancies, and catalytic activities are significantly influenced by support Al content. Compared to SBA-15, Al-SBA-15 supported Mo, CoMo and NiMo catalysts show outstanding activities for hydrogenation. (c) 2006 Elsevier B.V. All rights reserved.