Influence of micropore and mesopore spatial distribution of HZSM-5 catalysts on product selectivity during n-hexane catalytic pyrolysis

Hierarchical HZSM-5 with integrated micro–mesopore structure is promising for boosting light olefin yield in light paraffin catalytic cracking, yet conventional alkali etching creates disordered large mesopores and rough crystal surfaces that degrade light olefin selectivity. Herein, this work adopts NaHCO 3 –TPAOH composite alkali treatment and pos-surface silanization treatment were used to regulate the micro-mesopore spatial distribution of hierarchical HZSM-5, for investigating the re-distribute of the hierarchical HZSM-5 and the effects of pore structure and its spatial arrangement on product selectivity. It was found TPA + in composite alkali system possesses large steric hindrance, which inhibits excessive local OH - corrosion, and avoids the formation of irregular large defective mesopores. On the optimized catalyst, the selectivity of light olefins is elevated by 8.7%. After surface silanization of zeolite, precisely passivates external acidic sites without blocking internal micropore channels, concentrating mesopores inside the zeolite framework. This structure greatly promotes the monomolecular cracking pathway of alkanes and achieves an improvement in ethylene production. This study clarifies the regulatory mechanism of spatially differentiated mesopores in HZSM-5 catalysts on the n-hexane catalytic pyrolysis reaction and their modulation effect on light olefin selectivity. It deepens the fundamental understanding of the structure-performance correlation of hierarchical porous zeolites and provides reliable guidance for the rational design and targeted fabrication of high-efficiency pyrolysis catalysts. Download: Download high-res image (254KB) Download: Download full-size image