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

Abstract

MFI zeolite nanosheets (NS-MFI) with two different thicknesses (2.5 nm and 7.5 nm) and various Si/Al-2 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 N-2 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/Al-2 ratio, and superior catalytic performance for MTP reactions was observed at a Si/Al-2 ratio of 500. These results can be attributed to the appropriate acid density and the facile diffusion of molecules in the NS-MFI catalysts.