MCM-49 zeolite was alkali-treated with NaOH solutions under mild and severe conditions. The samples before and after alkali-treatment were both used as catalysts in liquid alkylation reaction of benzene with ethylene. XRD, XRF, TPD, TPO, IR, SEM, Si-29 NMR, N-2 adsorption and desorption techniques were employed to characterize the samples. The mildly alkali-treated samples exhibited higher catalytic stability than the parent HMCM-49, as the amorphous particles on the MCM-49 crystal surface were cleaned and the diffusion of the reactant and product was enhanced. The severe alkali-treatment condition resulted in the selective extraction of silicon atoms and the introduction of extra mesopores. The catalytic stability of the catalysts that had been severely alkali-treated was not as good as that of mildly treated ones, but was still better than that of the parent HMCM-49 catalyst if the alkali-treatment conditions were not too severe. (C) 2010 Elsevier B.V. All rights reserved.