Mesoporous Al-MCM-41 (Si/Al = 55 and 104) and Al,Zn-MCM-41 (Si/(Al + Zn) = 52) molecular sieves were synthesized hydrothermally. The materials were characterized by XRD, TGA, TPD (pyridine), ICP-AES, nitrogen sorption, and FT-IR techniques. The catalytic performance of these materials was examined in the vapor phase alkylation of m-cresol with isopropyl acetate. The products obtained were thymol, isothymol, 2-isopropyl-5-methylphenyl acetate (2-I-5-MPA), and isopropyl-3-methylphenyl ether (I-3-MPE). The time-on-stream study was carried out over Al-MCM-41(55) at 300degreesC and WHSV 1.52 h(-1) wherein optimum conversion of m-cresol and selectivity to thymol were obtained. The dependence of activity and selectivity on the acid sites and hydrophobic and hydrophilic properties of the catalysts is discussed. (C) 2004 Elsevier Inc. All rights reserved.