Synthesis of nanosheet epitaxial growth ZSM-5 zeolite with increased diffusivity and its catalytic cracking performance

Abstract

Nanosheet epitaxial growth hierarchical zeolite, that is, nanosheet MFI epitaxially grows on the surface of bulk seed, well maintaining the diffusion advantages of the 2D structure while increasing the microporous acidity characteristics. By adjusting the water content in the synthesis gel, hybrid zeolites with a Si/Al ratio of 100–300 were successfully synthesized. In the catalytic cracking reaction, the turnover frequency of nanosheet epitaxial growth zeolite was 143–156% higher than that of pure nanosheet zeolite. Although the pure nanosheet zeolite has high acid content and high mesoporosity, the “acid wall” barrier formed by the externally accessible acid reduces the catalytic efficiency greatly. The introduction of a microporous substrate modulates the acid distribution and decreases the surface barrier. The diffusion time constant of the hybrid zeolite is increased by 32%. The crystal combination of 2D nanosheets and 3D bulk zeolite results in high catalytic activity and helps to further understand the synergistic relationship between pore structure and acidic properties.