This work focuses on utilizing mesoporous SBA-15 materials of different pore diameters as potential hydrotreating catalyst supports for heavy gas oil (HGO). Hexane was used as swelling agent for the preparation of variable pore diameter SBA-15 materials. Four kinds of SBA-15 supported FeW catalysts with different pore diameters in the range of 5-20 nm were prepared and designated as Cats-A to D. The aqueous co-impregnation technique was employed for preparation of the catalysts. The supports were characterized by several techniques including X-ray powder diffraction (XRD) and N-2 adsorption-desorption isotherms. The SBA-15 supported FeW catalysts were characterized by ICP-MS, BET surface area analysis, powder XRD, transmission electron microscopy (TEM), scanning electron microscopy (SEM) and CO chemisorption. Results from XRD profiles, TEM images, and N2 adsorption-desorption isotherms confirmed the presence of highly ordered two-dimensional hexagonal structure with cylindrical arrays of pores. The structural integrity of the samples was preserved even after loading of 2 wt.% Fe and 15 wt.% W. Hydrotreating experiments were conducted using bitumen derived heavy gas oil under industrial conditions of temperature, pressure, LHSV, and gas to oil ratio of 375_400 degrees C, 8.8 MPa, 1 h(-1), and 600 mL/mL, respectively. The SBA-15 supported catalyst with pore diameter of 10 nm (Cat-B) was the best among the supports studied for FeW catalysts, probably due to sufficient mass transfer of reactant liquids and gases through the catalyst's pores while still maintaining a high surface area necessary for metal dispersion. (C) 2011 Elsevier B.V. All rights reserved.