Zeolite ZSM-12 was synthesized by a direct hydrothermal method and subsequently desilicated by alkaline treatment under different conditions. Changes in the properties of the zeolite samples were investigated by XRD, nitrogen adsorption/desorption isotherms, SEM, ICP-OES, and temperature programmed desorption of ammonia. Nitrogen adsorption measurements showed that the mesopore volume of the treated samples increased while the micropore volume decreased as a consequence of the desilication with NaOH. The Si/Al ratio of the desilicated samples decreased while the strong acidic sites determined by NH3-TPD were virtually unchanged. An L-9 orthogonal array of Taguchi method was used to investigate the optimum desilication conditions on mesopore volume. Catalytic activity of the samples were tested in the benzylation of benzene to diphenyl methane and the zeolite treated with 0.2 M NaOH at 85 degrees C for 60 min enhanced the catalytic activity 10-fold compared to the parent sample of HZSM-12.