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

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 67.55wt%, which improved the performance of the parent ZSM-5 by 13.42wt%.