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