不同粒径ZSM-5分子筛在苯与甲醇烷基化反应中催化性能及反应条件优化

采用水热合成法合成了不同粒径的ZSM-5分子筛催化剂，系统考察了分子筛粒径变化对苯与甲醇烷基化反应的影响。研究结果表明，随着ZSM-5分子筛粒径增大，不但苯的转化率和二甲苯选择性降低，而且催化剂稳定性明显下降。其中，粒径为0.25 μm的ZSM-5分子筛在苯烷基化反应中的催化性能最佳，且催化剂稳定性最好。另外，采用拉曼光谱和热重等方法对催化剂积碳物种和失活机理进行了深入研究，发现催化剂失活主要是由于反应过程中生成的大分子稠环芳烃堵塞了分子筛孔道并覆盖活性位点造成的。最后，考察了反应温度、原料组成及空速对苯烷基化反应的影响并优化出最佳的苯烷基化反应条件。

Catalytic Properties of Different Crystal Sizes for ZSM-5 Zeolites on the Alkylation of Benzene with Methanol and Optimization of the Reaction Conditions

The hydrothermal synthesis method is used to prepare various crystal sizes of ZSM-5, and the effect of the crystal size on the alkylation of benzene with methanol is systematically investigated. The research results show that the conversion of benzene, selectivity of xylene, and the stability of the catalyst all decrease significantly with increasing crystal size. The ZSM-5 zeolite with a crystal size of 0.25 μm possesses the best catalytic performance and stability compared with other larger-sized zeolites. In addition, the deposition species and deactivation mechanism were also studied by Raman spectroscopy and thermogravimetric analysis. The results indicate that the catalyst deactivation may be attributed to the formation of polycyclic aromatic molecules, which can block the channel of the zeolite and cover the active sites. Finally, the effects of the reaction temperature, ratio of benzene to methanol, and space velocity on the alkylation of benzene with methanol are also investigated, and the optimum reaction conditions are determined.