Catalytic Performance of Methanol to Aromatics over Hierarchical ZSM-5 Zeolite Synthesized by a Soft Template Method

A method for the direct synthesis of hierarchical zeolites was developed by converting precursors of zeolites and mesoporous copolymers into homogeneous gels using conventional block copolymers as scaffolds. In this method, hydrothermal synthesis is accomplished on a steam-assisted basis, and the dry gel leaves the system free of the liquid water phase, which successfully avoids phase separation between the soft stencil and the solid silica phase. The catalytic performance of hierarchical zeolites was evaluated on a fixed-bed reactor for the methanol-to-aromatics reaction. The hierarchical structure greatly enhances the catalytic activity of the probe reaction due to the increased outer surface, decreased coke formation, and diffusion resistance in the microporous network. The selectivity of BTX reached 65.8%, and there was no significant deactivation after a reaction of 107 h. The transition state and energy barrier for methanol to aromatics were obtained by the minimum energy search of the LST/QST transition state.

Automated summary

A method for the direct synthesis of hierarchical zeolites using block copolymers as scaffolds was developed, which successfully avoids phase separation between the soft stencil and the solid silica phase. The catalytic activity of the hierarchical zeolites was greatly enhanced, leading to improved selectivity and reduced deactivation rate.