Modification of the acidic and textural properties of ZSM-5 zeolite by using double mineralizers in synthesis and its catalytic performance in the conversion of methanol to propene

A static hydrothermal approach was adopted to synthesize nanosized SiO₂-ZSM-5 zeolite in the media of F^--OH^- with double mineralizers, using tetraethoxysilane, sodium aluminate, and tetrapropylammonium hydroxide as the silicon source, aluminum source, and template agent, respectively. The physical and chemical properties of the synthesized ZSM-5 zeolites were characterized and their catalytic performance was evaluated in the conversion methanol to propene (MTP); the effect of F^-/Al₂O₃ molar ratio on the catalytic performance of synthesized H-ZSM-5 was investigated. The results indicate that an increase in the F^-/Al₂O₃ molar ratio of the synthesis mixture leads to an increase in the surface content of microcrystalline SiO₂, accompanying with a decrease in the relative crystallinity, surface area, pore volume, and acid strength and density. With a F^-/Al₂O₃ molar ratio of 12, the SiO₂-ZSM-5 zeolite exhibits the best catalytic performance in MTP, with a selectivity of 45% to propene and a propene/ethene (P/E) ratio of greater than 10. It is further hypothesized that the transition state shape selectivity plays an important role in determining the product selectivity in MTP.