多级孔ZSM-5分子筛的制备及其催化甲醇芳构化反应性能

采用晶种法，在合成体系中引入十六烷基三甲基溴化铵（CTAB）制备了具有多级孔道的ZSM-5分子筛。采用XRD、SEM、NH₃-TPD、XRF和氮气吸附等多种技术对其进行了表征，并考察了不同CTAB添加量对该分子筛结构、酸性及其在甲醇芳构化反应中催化性能的影响。结果表明，CTAB的添加显著影响分子筛的形貌、孔结构及分子筛的酸性，进而决定其在甲醇制芳烃反应中的稳定性和芳构化选择性。分子筛增加的介孔性提高了大分子化合物的扩散，进而提高了催化剂寿命。CTAB的添加抑制了铝源进入骨架进行配位，增加CTAB的用量导致Si/Al比提高，进而导致分子筛酸性下降以及芳烃选择性下降。

Synthesis of hierarchical ZSM-5 molecular sieves and evaluation of their catalytic performance in methanol aromatization

A series of ZSM-5 nanozeolites with hierarchical porosity were prepared by a seeding method of adding cetyltrimethyl ammonium bromide (CTAB). The hierarchical ZSM-5 molecular sieves were characterized by XRD, SEM, NH₃-TPD, XRF and N₂ sorption. The impacts of CTAB amount on the zeolite structure, acid property and the catalytic performance in methanol aromatization were investigated. The results indicated that the CTAB amount significantly affected the crystal morphology, pore structure, acidity and thus influenced the catalytic stability and aromatic selectivity considerably. The hierarchical ZSM-5 catalysts exhibited an increased mesopores by introducing CTAB and high stability for the MTA reaction due to the enhanced mass transfer and reduced diffusion limitation. Also, the formation of framework Al was suppressed by the addition of CTAB. The Si/Al ratio was increased by increasing the amounts of CTAB, which decreased the acidity of hierarchical ZSM-5 molecular sieves and the aromatics selectivity.