Facile synthesis of mesoporous MFI crystals with multilamellar morphology and its application in catalytic cracking of 1-hexene

Abstract

Turning crystal morphology and size of zeolite materials is crucial for promoting their diffusion and catalytic properties. Herein, MFI hierarchical lamellar zeolites with tunable SiO₂/Al₂O₃ ratios were synthesized under hydrothermal conditions through the self-assembly of commercially available simple surfactant and inorganic zeolite precursor. Through detailed investigation of the crystallization process using various characterization techniques, a reliable formation mechanism of hierarchical lamellar ZSM-5 zeolite was proposed. Cetyltrimethylammonium bromide (CTAB) acted both as a structure-directing agent and a mesoporogen, responsible for creating such structure. Hierarchical lamellar ZSM-5 can be successfully obtained by regulating the SiO₂/Al₂O₃ ratios and crystallization temperature. In the 1-hexene cracking process, the hierarchical lamellar ZSM-5 zeolite exhibited significantly enhanced propylene selectivity and stability compared to conventional microporous ZSM-5. The enhanced textural and diffusion properties can effectively suppress the hydrogen transfer reaction, which plays a crucial role in determining the selectivity of C₃-C₅ olefins. These findings provide a facile and rational synthesis route to reduce diffusion resistance and enhance the catalytic performance of zeolite.