IM-5 series zeolites (I-xat-0.05TPABr) were prepared by treating the pristine IM-5 zeolites in a mixed solution of NaOH and TPABr (tetrapropylammonium bromide) with different NaOH concentrations (C (NaOH)). It was found the porosity and acidity of modified IM-5 zeolite changed obviously with C (NaOH). When used for alkylation of benzene with ethanol, the modified I-xat-0.05TPABr exhibited better reaction stability than the unmodified IM-5 zeolite, and I-0.5at-0.05TPABr showed the best stability. Typically, the reaction stabilities of I-xat-0.05TPABr catalysts were directly related to the hierarchical factor, besides the carbon deposition rate. [GRAPHICS] .