Aluminosilicate MCM-48 mesostructures assembled from dried zeolite precursors and Gemini surfactant

Abstract

Aluminosilicates with well-ordered MCM-48 mesostructures were prepared via the assembly of “dried” zeolite precursors with Gemini surfactant. The aluminosilicate MCM-48 materials thus obtained were characterized by a variety of techniques including powder X-ray diffraction (XRD), 27Al and 29Si magic angle spinning (MAS) NMR, IR, transmission electron microscopy (TEM), scanning electron microscopy (SEM) and nitrogen adsorption measurements. The use of the Gemini surfactant and the dried zeolite precursor facilitated the incorporation of more Al (at an Si/Al ratio of up to 20) into the MCM-48 framework without compromising the integrity of the cubic mesostructure. The materials assembled from zeolite precursors exhibited higher hydrothermal stability and better cumene cracking activities than the Al-MCM-48 sample prepared by direct synthesis. Although the physical measurements could not distinguish between the dried precursors of MFI and those of BEA zeolites, the catalytic cracking activity of their derived MCM-48 samples did differ. Materials ranging from zeolitic MCM-48, zeolite/MCM-48 composite and pure zeolite nanocrystals were obtained by varying the temperature used to prepare the zeolite precursors and that of the hydrothermal treatment following the addition of surfactant.