The typical physico-chemical properties and their hydrodesulfurization activities of NiMo/TiO2-Al2O3 series catalysts with different TiO2 loadings were studied. The catalysts were evaluated with a blend of two kinds of commercially available diesels in a micro-reactor unit. Many techniques including N-2-adsorption, UV-vis DRS, XRD, FT-Raman, TPR, pyridine FT-IR and DRIFT were used to characterize the surface and structural properties of TiO2-Al2O3 binary oxide supports and the NiMo/TiO2-Al2O3 catalysts. The samples prepared by sol-gel method possessed large specific surface areas, pore volumes and large average pore sizes that were suitable for the high dispersion of nickel and molybdenum active components. UV-vis DRS, XRD and Fr-Raman results indicated that the presence of anatase TiO2 species facilitated the formation of coordinatively unsaturated sites (CUS) or sulfur vacancies, and also promoted high dispersion of Mo active phase on the catalyst surfaces. DRIFT spectra of NO adsorbed on the pure MOS2 and the catalysts with TiO2 loadings of 15 and 30% showed that NiMo/TiO2-Al2O3 catalysts possessed more CUS than that of pure MOS2. HDS efficiencies and the above characterization results confirmed that the incorporation of TiO2 into Al2O3 could adjust the interaction between support and active metals, enhanced the reducibility of molybdenum and thus resulted in the high activity of HDS reaction. (c) 2007 Elsevier B.V All rights reserved.