Preparation of micro-mesoporous ZSM-5 zeolite through mixed alkali treatment and its catalytic performance in the alkylation of thiophene

ZSM-5 zeolite with a SiO₂/Al₂O₃ mol ratio of 50 as the raw material was treated either by adding tetrapropylammonium hydroxide solution for secondary crystallization after pre-treating with Na₂CO₃ solution or directly by Na₂CO₃/TPAOH mixed solution, to prepare the micro-mesoporous hierarchical HZSM-5 catalyst;the catalytic performance of resultant micro-mesoporous HZSM-5 in thiophene alkylation was then investigated.The results showed that if the raw ZSM-5 material is first pre-treated with 4 mol/L Na₂CO₃ and then crystallized for the second time in the presence of 0.3 mol/L TPAOH and at 170℃ for about 24 h, the resultant micro-mesoporous HZSM-5(CO₃^2--TPA⁺, 0.3-24-170) has a moderate pore diameter and acidity and exhibits the highest conversion of thiophene (99.1%) in alkylation.However, if the raw ZSM-5 is treated by the mixed solution of Na₂CO₃ and TPAOH, the dissolved SiO₂ may block the pores and channels, leading to lower acidity and smaller pores, which is not suitable for the thiophene alkylation.