Structural and physicochemical effects of MFI zeolite nanosheets for the selective synthesis of propylene from methanol

• This work could synthesize NS-MFI catalysts optimized for MTP reaction.
• The MTP activity and catalyst lifetime improved by the mesoporosity of NS-MFIs.
• The thinner thickness of NS-MFI catalyst was preferable in view of the catalyst life.
• Correlation between the coking and Si/Al2 ratio of NS-MFIs could be explained by acid site dispersion.
• This paper suggested the optimized NS-MFI catalysts can greatly improve MTP process efficiency.

MFI zeolite nanosheets (NS-MFI) with two different thicknesses (2.5 nm and 7.5 nm) and various Si/Al2 ratios (100–700) were prepared and their catalytic activities for propylene production from methanol were investigated. According to analyses of X-ray diffraction patterns as well as scanning electron microscopy, transmission electron microscopy, and N2 adsorption results, all NS-MFI catalysts had a well-developed nanosheet structure with a high specific surface area and a large mesopore volume. In the methanol-to-propylene (MTP) reaction, they showed greater activity and selectivity to propylene and longer lifetimes than commercial ZSM-5. Among these NS-MFI zeolites, thinner NS-MFI had better catalytic activity in MTP reactions than thicker NS-MFI at the same Si/Al2 ratio, and superior catalytic performance for MTP reactions was observed at a Si/Al2 ratio of 500. These results can be attributed to the appropriate acid density and the facile diffusion of molecules in the NS-MFI catalysts.

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