Self-assembly of hierarchical ZSM-5 particles on rice husk template as hybrid catalysts for boosting methanol aromatization

Herein, natural rice husks with hierarchically porous structures were used as a platform to assemble ZSM-5 particles (denoted as hierarchical ZSM-5) to improve diffusion properties in the methanol-to-aromatics (MTA) reactions. Rice husk could work as the platform to immobilize zeolite grains and provide additional silicon sources for the growth of zeolite particles. Sodium hydroxide amount and SiO2/Al2O3 ratio strongly determined the acid properties, and the rotational crystallization condition favored the zeolite formation. Improved diffusion properties of hierarchical ZSM-5 particles were confirmed by comprehensive pore analysis and benzene diffusion experiments, showing an excellent diffusion property towards aromatic molecules. Compared with commercial microporous zeolite in the catalytic MTA reaction, hierarchical ZSM-5 exhibited superior aromatics selectivity (40.8 vs. 35.8 %), higher liquid hydrocarbon yield (22.3 vs. 14.7 wt%), and longer lifetime (60 vs. 40 h). These results offer new insights into the controllable synthesis of Hier-ZSM-5 with a hierarchically porous structure using biomass as templates.