MFI-Type Zeolite Nanosheets with Controllable Length along the b‑Axis for Methanol-to-Propylene Reactions

The lifetime of a catalyst and the selectivity of a product are inevitable and key issues in catalytic reactions. These two issues can be settled by synthesizing the MFI-type zeolite nanosheet and regulating the length along the b-axis of the MFI-type zeolite nanosheet when MFI-type zeolites are employed in catalytic reactions. Herein, we proposed a facile strategy for regulating the length along the b-axis of various MFI-type zeolite nanosheets (ranging from ca. 50 nm to a few micrometers). This strategy could be accomplished by simple hydrothermal synthesis with the aid of biomass-based guaiacol and “liquid seed” (LS). Not only the roles and effects of guaiacol and LS but also the mechanism of the formation of nanosheets was investigated and discussed in detail. The as-synthesized ZSM-5 nanosheets were employed in the methanol-to-propylene reaction and characterized by various techniques (X-ray diffraction, X-ray fluorescence, N₂ physisorption, scanning electron microscopy, NH₃-TPD, and thermalgravimetric analysis). The lifetimes of as-synthesized ZSM-5 nanosheets were 2.3-fold and 10-fold longer than those of commercial ZSM-5 nanosheets and conventional ZSM-5, respectively. Besides, the as-synthesized ZSM-5 nanosheets could be used for 3 cycles without deactivation. This superior catalytic performance could be attributed to shorter diffusion paths along the b-axis.