Mesoporous MFI zeolites as high performance catalysts for Diels-Alder cycloaddition of bio-derived dimethylfuran and ethylene to renewable p-xylene

- Nanosheet MFI zeolites (NS-MFI) were synthesized with different crystal thickness and Si/Al ratios.
- NS-MFI were investigated as model catalysts for Diels-Alder cycloaddition reaction of 2,5-dimethylfuran and ethylene.
- p-Xylene production yield improved by the NS-MFI with small crystal thickness.
- The better PX production yield of NS-MFI is attributed to a large number of external Brønsted acid sites and mesopores.
- These catalytic factors can be extended to a commercial ZSM-5 zeolite catalyst.

Zeolite solid-acid catalyst can produce p-xylene (PX) via a renewable synthetic route through Diels-Alder cycloaddition and dehydration reactions of bio-derived 2,5-dimethylfuran (DMF) and ethylene (DMF-to-PX). Here, to find a key factor in the physicochemical properties of a zeolite catalyst, we synthesized a series of mesoporous MFI zeolite nanosheets with systematically controlled thickness (2.5 and 7.5 nm) and silica-alumina ratio (Si/Al = 48-340) as well-defined model catalysts for PX production. From the catalytic results using these MFI zeolite nanosheets and conventional MFI zeolites, PX production yield was found to be strongly related to zeolite crystal thickness and concentration of Brønsted acid sites of the MFI zeolite catalysts. The MFI zeolite nanosheet with small thickness provided high PX production due to the presence of Brønsted acid sites on the exterior surface and facile mass transfer of aromatic compounds through mesopores. To verify these catalytic factors and to apply it to commercially available zeolite, a mesoporous MFI zeolite was prepared from a commercial ZSM-5 zeolite via a simple post-treatment process; mesoporous MFI-type zeolites were tested in the DMF-to-PX reaction. This mesoporous MFI zeolite exhibited a superior PX yield (75.8%) with high DMF conversion and PX selectivity compared with those characteristics of pristine MFI zeolite (PX yield = 8.4%).

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