Tetrahedrally Coordinated W(Vi) Species Induced Lewis Acid for Stable Catalytic Cracking of 1-Hexene to Propene

Abstract

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 the W-ZSM-5 by eliminating the non-skeleton aluminum and excessive Brønsted 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 o 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.

Keywords: 1-Hexene, Propene, tungsten, Lewis Acid, ZSM-5