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 mu m 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.