A series of MCM-49 catalysts with different Si/Al ratios were prepared and characterized by XRD, XRE, Al-27 MAS NMR, BET, and SEM. The overall and external surface acidity of the catalysts were measured by temperature-programmed desorption of both small- and large-base probe Molecules (NH3 and 2.6-di-tert-butyl-pyridine), as well as by model acid-catalyzed reactions, such as cumene cracking and 1,3,5-tri-tert-butyl-benzene dealkylation. and compared with those of ZSM-5 and USY zeolites. The strong external acid sites on the surface pockets of MCM-49 play an important role in the alkylation of hydroquinone with tert-butanol. MCM-49 catalyst with a Si/Al ratio of 20 exhibits good activity and selectivity for the alkylation reaction, and it is more reusable than mesoporous molecular sieves Such as AISBA-15 and MSU-S-(BEA) due to the higher thermal and hydrothermal stability of the crystalline zeolite framework. (c) 2006 Elsevier Inc. All rights reserved.