多级孔ZSM-5分子筛的制备及催化噻吩烷基化性能研究

用不同浓度的Na₂CO₃溶液处理ZSM-5分子筛,采用XRD、XRF、SEM、N₂吸附脱附及NH₃-TPD方法对处理前后的ZSM-5分子筛进行表征,并考察了Na₂CO₃溶液处理对ZSM-5分子筛孔结构、酸性以及噻吩烷基化性能的影响。结果表明,Na₂CO₃溶液处理在保持ZSM-5分子筛微孔骨架结构的同时,增加了ZSM-5分子筛的比表面积、外表面积和介孔体积,并调变了酸性。Na₂CO₃溶液处理提高了ZSM-5分子筛催化剂的噻吩烷基化活性和噻吩选择性。一定反应条件下,随着Na₂CO₃溶液浓度增加,多级孔ZSM-5分子筛的噻吩烷基化性能逐渐提高,而噻吩选择性先增加后下降。当Na₂CO₃溶液浓度为2 mol/L时,分子筛的噻吩转化率和噻吩选择性分别为81.26 %和73.15%。当Na₂CO₃溶液浓度为3 mol/L时,噻吩转化率和选择性分别为90.57 %和72.59%。

Preparation of hierarchical ZSM-5 zeolites and their catalytic performance in thiophene alkylation

ZSM-5 zeolites were treated by Na₂CO₃ solutions with different concentrations and characterized by XRD, XRF, SEM, N₂ sorption and NH₃-TPD techniques; the influence of Na₂CO₃ treatment on their pore structure, acidity and performance in thiophene alkylation was investigated. The results showed that the BET surface area, external surface area and mesoporous volume of the ZSM-5 zeolites were enhanced through Na₂CO₃ treatment and the acidity was also modulated without altering the microporous structure of ZSM-5 zeolites. The activity and the selectivity to alkylates of the ZSM-5 zeolites in thiophene alkylation are also improved after Na₂CO₃ treatment. With the increase of Na₂CO₃ solution concentration, the thiophene conversion over the hierarchical ZSM-5 zeolites increases gradually, while the selectivity to alkylates increases first, reaches a maximum and then decreases along with the Na₂CO₃ solution concentration. When the Na₂CO₃ concentrations are 2 and 3 mol/L the thiophene conversions and alhylation selectivities are 81.26%, 73.15% and 90.57%, 72.59%, respectively.