等级孔微孔-介孔Fe2O3/ZSM-5中空分子筛催化材料的制备及催化苄基化性能

ZSM-5分子筛具有极其均匀的孔道结构、 良好的形状选择性和催化活性及耐水热稳定性, 是一种高效、 绿色的固体催化剂, 被广泛应用于石油催化裂化、 精细化工和环境保护等领域. 但其单一的微孔结构大大降低了客体分子的流通扩散性, 导致由大分子参与的芳烃烷基化反应受到极大限制. 本文采用NaOH/四丙基氢氧化铵(TPAOH)混合碱处理微孔ZSM-5, 制备了具备高结晶度、 高比表面积的等级孔微孔-介孔ZSM-5中空分子筛材料, 该材料在保持微孔孔道良好水热稳定性和大量活性中心的同时, 还通过介孔的引入进一步促进反应物及产物的扩散, 使间三甲苯苄基化反应的转化率提高了3.8倍. 通过在等级孔微孔-介孔ZSM-5中空材料上负载Fe, 开发出了具有双功能的等级孔微孔-介孔Fe₂O₃/ZSM-5中空催化剂, 该催化剂在苯的苄基化反应中表现出优异的催化性能, 当Fe负载量(质量分数)为6.67%, 反应温度为75 ℃, 反应时间为15 min时, 转化率高达98.3%, 选择性为81.6%, 最终收率达到80.2%.

Preparation of Hierarchical Microporous-mesoporous Fe2O3/ZSM-5 Hollow Molecular Sieve Catalytic Materials and Their Catalytic Properties for Benzylation

As a kind of efficient and environment friendly solid catalyst， ZSM-5 zeolite shows extremely uniform pore structure， excellent shape selectivity， great catalytic activity and superb hydrothermal stability， which has already been used in plenty of fields like petroleum catalytic cracking， fine-chemicals processing and environmental protection. However， its simplex microporous structure severely reduces the diffusion of guest molecules， which results in a great limitation of aromatic alkylation reaction in which macromolecules participate. In this paper， through a method of etching ZSM-5 zeolite with NaOH/TPAOH（tetrapropylammonium hydroxide） mixed alkali， a hierarchical micro-/mesoporous ZSM-5 catalyst with high crystallinity and abundant specific surface area was prepared. This special hierarchical structure can not only maintain the great hydrothermal stability and plentiful active centers of microporous ZSM-5， but also promote the diffusion of reactants and products with the introduction of mesopores. As a result， the conversion of m-trimethylbenzene benzylation increased 3.8 times. In addition， a bifunctional hierarchical micro-/mesoporous Fe₂O₃/ZSM-5 hollow catalyst was developed by loading Fe on the hierarchical microporous- mesoporous ZSM-5 hollow catalyst mentioned above， which exhibited excellent catalytic performance in the benzylation reaction of benzene， and the conversion， selectivity and percent yield reached 98.3%， 81.6% and 80.2% while Fe loading was 6.67%（mass fraction）， and the reaction temperature and the reaction time were 75 ℃ and 15 min， respectively.