Aluminum incorporated SBA-15 mesoporous molecular sieves with different n(Si)/n(Al) ratios have been hydrothermally synthesized by adjusting the synthesis gel pH below the isoelectric point of silica (pH similar to 2) using nonionic surfactant as the structure directing agent. All the samples were characterized by X-ray diffraction, N-2 adsorption to determine specific pore volume, pore size and specific surface area, FT-IR, TGA-TPD to determine the acid sites and Al-27 magic angle spinning nuclear magnetic resonance spectroscopy (MAS NMR). Vapor phase alkylation of in-cresol with isopropanol was carried out over large pore AlSBA-15 catalysts with different n(Si)/n(Al), ratios. The influence of various reaction parameters such as reaction temperature, reactant feed ratio and space velocity affecting the activity and selectivity of AlSBA-15, were studied. 2-Isopropyl-5-methylphenol (2I-5MP) was obtained as a major product with high selectivity. AlSBA-15 (45) was found to be the most active catalyst in this study. It showed 73.5% m-cresol conversion and a selectivity of 45.68% for 21-5MP under the optimized reaction conditions. Further, large pore AlSBA-15 (45) catalyst was not deactivated when the reaction was carried out for several hours of reaction time. (c) 2005 Elsevier B.V. All rights reserved.