混合碱处理制备微介孔催化剂及其噻吩烷基化催化性能

摘要

ZSM-5 zeolite with a SiO2/Al2 O3 mol ratio of 50 as the raw material was treated either by adding tetrapropylammonium hydroxide solution for secondary crystallization after pre-treating with Na2 CO3 solution or directly by Na2 CO3/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 Na2 CO3 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 ( CO2-3 -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 Na2 CO3 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.%以SiO2/Al2 O3物质的量比为50的H-ZSM-5分子筛为母体,分别采用Na2 CO3溶液处理后加入TPAOH溶液进行二次晶化法以及Na2 CO3/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Na2 CO3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(CO2-3-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Na2 CO3/TPAOH同时处理HZSM-5分子筛所得的催化剂,由于生成大量SiO2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。