Fabrication of a hierarchically structured beta zeolite by a dual-porogenic surfactant

Abstract

Hierarchically structured beta zeolite has been prepared under hydrothermal synthesis conditions by employing only one dual-porogenic hexaquaternary ammonium type surfactant. The resulting mesoporous molecular sieve was characterized by a complementary combination of X-ray powder diffraction, N₂ adsorption–desorption isotherms, scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, ²⁷Al MAS NMR spectroscopy, thermogravimetric analysis and density functional theory calculation. These analyses indicated that the mesopore walls were zeolite-like microporous crystalline aluminosilicate frameworks. The surfactant acts as a dual-functional template for the generation of both micropores and mesopores simultaneously. Due to the short diffusion routes and abundant exposed acid sites on the external surface, the hierarchically structured beta zeolite displayed a clear advantage for catalysis reactions of large molecules compared to conventional zeolites and traditional mesoporous materials. Furthermore, this effective approach can be extended to the synthesis of other hierarchical zeolites.