Self-Pillared MFI-Type Zeolite Nanosheets as Selective Catalysts for Glycerol Dehydration to Acrolein

Abstract

The surplus production of glycerol as a by-product of biodiesel has become a serious problem for the sustainability of the biodiesel industry. Glycerol dehydration over MFI zeolites offers a green route to acrolein production. However, conventional MFI zeolites suffer diffusion limitation, which inhibits accessibility to active sites and causes quick deactivation of catalysts because of severe coke deposition. In this study, self-pillared MFI nanosheet catalysts were prepared with different Si/Al ratios to catalyze glycerol dehydration. The nanosheets with interlayered meso-space possessing wide a,c-planes of ∼2 nm thickness in the b-axis provide a shortened diffusion pathway to easily access the active acid sites. In contrast to conventional MFI zeolites, the nanosheet morphology significantly enhanced the catalyst selectivity, activity, and stability; gave a high acrolein selectivity (92%) at a higher WHSV of 4 h–1; and remained stable after up to 100 h of the reaction of 5% glycerol in water.