The effect of the presence of varying titanium concentrations introduced into hexagonal mesoporous silica (HMS) support on the catalytic activity of the catalysts was evaluated in the hydrodesulfurization of 4-ethyl-6-methyl dibenzothiophene (4E6MDBT) in a fixed-bed reactor at T = 598 K, P = 5.0 MPa, and WHSV = 46.4 h(-1). The catalysts were characterized by S-BET, XRD, DRS, FTIR spectroscopy of the framework vibration, DRIFTS in the OH region, H-1-NMR, FT-IR spectroscopy of adsorbed NO and pyridine, XPS, and TGA. All Ti-containing catalysts showed higher activity than the Ti-free CoMo/HMS sample. The catalyst with a Si/Ti molar ratio of 40 is the most active. The HDS of 4E6MDBT over the Ti-free catalyst proceeds mainly via the dealkylation (DA) route, and then HDS of the more reactive DBT occurs. After Ti-incorporation into the HMS material, additional acid-catalyzed isomerization occurs, followed by direct HDS and HYD. Based on the catalyst activity-structure correlation, the increase in HDS activity over the Ti-containing catalysts with respect to the Ti-free sample was attributed to increased CoS2 and MoS2 surface exposure, as well as increased Lewis and Br circle divide nsted acidity. (c) 2006 Elsevier Inc. All rights reserved.