Abstract: MCM-22 molecular sieve with different Si/Al ratios was synthesized by dynamic hydrothermal synthesis method using hexamethyleneimine (HMI) as template, and MCM-22 molecular sieve as acidic component, a bifunctional transformation type catalyst (Pt/MCM -22) for the isomerization of xylenewas prepared by supported platinum. The morphologies and properties of the molecular sieve samples were characterized by X-ray diffraction (XRD), specific surface area testing (BET), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR) and other methods. The performance of the catalyst was evaluated by using a micro-piston flow reactor and compared with that ofthe catalyst prepared with MORzeolite. The mechanism of the catalytic isomerization of xylene was further studied, and the evaluation results were explained. The results showed that MCM-22 molecular sieve had excellent isomerization activity and selectivity for xylene isomerization, and the acidity of the molecular sieve would affect its reaction performance.

Key words: xylene isomerization, MCM-22 zeolite, tropylium, acidity