Insight into catalytic cracking pathways of n‐pentane over bifunctional catalysts to produce light olefins

Abstract

Revealing the reaction mechanism to guide the industrial production of targeted products still remains a grand challenge for catalytic cracking of light alkanes to olefins over metal‐acid bifunctional catalyst. Herein, we systematically investigated the reaction mechanism of n‐pentane cracking on the Ag/ZSM‐5 bifunctional catalyst featuring both dehydrogenation and cracking capabilities. Specifically, overall cracking network of n‐pentane was comprehensively constructed to show the roles of metal dehydrogenation sites and acid sites respectively, in which metal Ag could substitute the H of the Brønsted acid site to form the Al–O–Ag linkage with enhanced adsorption and activation of n‐pentane, while Brønsted acid site with weak acid strength relay to promote cracking reaction. Thanks to this synergy of the two active sites, the apparent activation energy of n‐pentane cracking to light olefins was decreased from 82.77 KJ/mol to 68.26 KJ/mol and the proportion of specific path (C5H12 → H2 + C5H10) in n‐pentane monomolecular cracking reaction increased from 14.62% to 69.24%. In addition, 0.57Ag/ZSM‐5 catalyst exhibited the conversion of n‐pentane up to 67.55 wt%, which improved the performance of the parent ZSM‐5 by 13.42 wt%. These analysis results of reaction mechanism may provide some insights for the rational design of catalysts and the full utilization of petrochemical resources.