混合碱处理制备微介孔催化剂及其噻吩烷基化催化性能

以SiO_2/Al2O3物质的量比为50的H-ZSM-5分子筛为母体,分别采用Na_2CO_3溶液处理后加入TPAOH溶液进行二次晶化法以及Na_2CO_3/TPAOH混合溶液同时处理法,制备了微孔-介孔多级孔HZSM-5催化剂,对其噻吩烷基化反应催化性能进行了研究。结果表明,采用4 mol/L的Na_2CO_3溶液处理后的催化剂在TPAOH溶液中发生了二次晶化;当TPAOH溶液浓度为0.3 mol/L、晶化温度为170℃、晶化时间为24 h时,得到的HZ(CO_2-3-TPA+,0.3-24-170)催化剂具有适宜的孔径和酸性,其噻吩烷基化转化率最高(99.1%)。而Na_2CO_3/TPAOH同时处理HZSM-5分子筛所得的催化剂,由于生成大量SiO_2堵塞了孔道,覆盖了催化剂表面,降低了催化剂的平均孔径和酸性,不适合噻吩烷基化反应。

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.