Tetrahedrally coordinated W(VI) species induced Lewis acid for stable catalytic cracking of 1-hexene to propene

Reasonable regulation of the acidity of ZSM-5 could fundamentally improve the catalytic performance for the cracking of low-carbon olefins to propene. Herein, a series of ZSM-5 catalysts with highly dispersed tetrahedrally coordinated W(VI) species were prepared for the catalytic cracking of 1-hexene to propene by a simple top down method. Multi-characterizations revealed that the introduction of W enhanced the stability of the Si-O-Al structure in W-ZSM-5 by eliminating the non-skeleton aluminum and excessive Bronsted acid sites, leading to a superb resistance to carbon/coke deposition. Moreover, the Lewis acid sites originated from the active tetrahedrally coordinated W (VI) species improved the propene selectivity via inhibiting the polymerization of products. In addition, through the optimization of various parameters (such as Si/Al ratio, temperature and weight hourly space velocity), high 1-hexene conversion (>97%) and propene selectivity (>40%) could be maintained at 575 degrees C over the W-ZSM-5(60) catalyst during 30 h long period reaction. This work may provide some new insights for the effect of W-based catalysts on acid composition in the cracking of light olefins to propene.

Automated summary

Reasonable regulation of acidity in ZSM-5 catalysts, by introducing highly dispersed tetrahedrally coordinated W(VI) species, greatly improves the catalytic cracking performance for the production of propene from 1-hexene. The introduction of W enhances the stability of the catalyst structure, eliminates non-skeleton aluminum and excessive Bronsted acid sites, and inhibits carbon/coke deposition. The active tetrahedrally coordinated W(VI) species also enhance propene selectivity by inhibiting product polymerization. Optimizing parameters such as Si/Al ratio, temperature, and weight hourly space velocity allows for high conversion and selectivity to be maintained over a long reaction period.