A mechanism of the realumination process was proposed when MCM-22 was post-treated in Al(NO3)(3) solution. Al atoms would deposit into zeolite with the amorphous alumina form, or insert into the framework by substituting Si atoms on certain T sites near the surface. The realumination process increased the amount of acid sites on the surface of MCM-22, significantly improved the catalytic activity and stability for olefins conversions in the alkylation of benzene with diluted olefins.