The properties of three types of pore systems in MCM-49 zeolite have been investigated by precoking to block the supercages and poisoning the surface pockets. Most Lewis acid sites (ca. 73%) are located within the supercages, while 38% of Bronsted acid sites are located in the surface pockets, 28% in the sinusoidal pores and only 34% in the supercages, respectively. Alkylation of benzene with ethylene mainly occurs in the surface pockets, and the contribution from the sinusoidal pores is limited. The generation of heavy aromatics in supercages results in the deactivation of MCM-49 at the early reaction stage. A moderate alkali-treatment process has been demonstrated to enlarge the opening of supercages without affecting the sinusoidal pores, resulting in improved diffusion of big molecules and hence better catalytic performance for liquid alkylation of benzene with ethylene. (C) 2011 Elsevier Inc. All rights reserved.