In-situ synthesis of hierarchical lamellar ZSM-5 zeolite with enhanced MTP catalytic performance by a facile seed-assisted method

Abstract

A seed-assisted route has been applied to prepare the hierarchical lamellar ZSM-5 zeolite with good porosity and catalytic performance in methanol to propylene (MTP) reaction. In this method, ZSM-5 crystal seeds instead of organic quaternary ammonium were used to direct the formation of ZSM-5 nuclei and conventional surfactant cetyltrimethylammonium bromide (CTAB) employed as the mesoporogen. The process for the formation of hierarchical lamellar ZSM-5, including the effect of the ratio of CTAB/SiO2, initial gel aging temperature, synthesis temperature and synthesis time were discussed in detail. The results suggested that mesoporous structure was first obtained and then transformed into MFI structure in-situ during the hydrothermal synthesis process. The obtained hierarchical lamellar ZSM-5 zeolite displays an organized flack-like nanosheet stacks morphology with regular intercrystal mesopores of 3–7 nm, possessing large surface area and mesopore volume. Moreover, the synthesized hierarchical ZSM-5 zeolite has perfect catalyst lifetime in methanol to propylene (MTP) reaction than conventional microporous ZSM-5 zeolite, which could be ascribed to the hierarchical mesoporous structure accommodating more bulky molecules and accessible acid sites in the catalytic reaction.