Abstract: Fe-ZSM-5 molecular sieve with hierarchical pore structure was prepared by alkali treatment of ZSM-5 and impregnation method. The catalyst samples were characterized by X-ray diffraction, N2 adsorption-desorption and NH3 temperature programmed desorption. The results showed that the pore size of the zeolite was enlarged, the amount of weak acid sites increased significantly, the strength of weak acid became stronger, and the amount of strong acid sites decreased when ZSM-5 was treated with 0.05 mol/L of sodium hydroxide solution. After loading Fe, the structure of ZSM-5 was still maintained. The alkylation of benzene with benzyl chloride was carried out to investigate the effects of alkali concentration, metal loading, calcination time and temperature on the catalytic performance of the catalyst for the synthesis of diphenylmethane. The experimental results indicated the prepared catalyst had the high catalytic performance for the alkylation reaction when the Fe to molecular sieve mass ratio was 5%, the sodium hydroxide concentration was 0.05 mol/L, the alkali treatment time was 30 minutes, the calcination temperature was 450 ℃, and the calcination time was 4 h. The conversion rate of benzyl chloride was 96.2%, and the selectivity of diphenylmethane was 84.9%.

Key words: alkali treatment, metal modification, ZSM-5, diphenylmethane