The worldwide rise in biodiesel production leads to an immense increase in glycerol as a byproduct, and this increase causes a rapid decline in the glycerol price. 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, we prepared H-ZSM-5 with precisely controlled channel lengths in b-axis. By modifying the composition of precursor in aluminosilicate gel, four highly nanocrystalline H-ZSM-5 catalysts were prepared with similar Si/Al ratio, acidity strength and a-axis length, but with different b-axis channel length (60 nm, 130 nm, 180 nm, and 250 nm). By using these four catalysts, the influence of the b-axis channel length on the glycerol dehydration to acrolein was studied in terms of the catalyst activity, selectivity, and stability. A significant impact of b-axis channel length on acrolein selectivity and catalyst activity was revealed. Complete glycerol conversion and high acrolein selectivity (88%) were observed over H-ZSM-5 with 60 nm 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.

Catalytic dehydration of glycerol to acrolein over short b-axis H-ZSM-5

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.