Controlling the selectivity and deactivation of H-ZSM-5 by tuning b-axis channel length for glycerol dehydration to acrolein

Abstract

Glycerol dehydration to value-added acrolein over zeolite catalysts is a useful approach to offer a sustainable economic route for the biodiesel industry. Glycerol dehydration over H-ZSM-5 with conventional morphology often exhibits a significant mass transfer limitation and inhibits the access to active sites in the micropores, which causes low activity, selectivity, and severe catalyst deactivation. In this study, a significant impact of b-axis channel length on acrolein selectivity and catalyst activity was revealed by using H-ZSM-5 synthesized with varied channel length in b-axis of 60, 130, 180, and 250nm. Complete glycerol conversion and high acrolein selectivity (88%) were observed over H-ZSM-5 with 60nm channels length in b-axis, due to high availability of active sites and enhanced diffusion through the shortest channels, which dramatically suppressed the coke formation. The catalysts with long b-axis channels exhibited a slow internal diffusion, leading to increased polymerization side reactions and coke formation.