Characterization of chabazite and chabazite-like zeolites of unusual composition

Abstract

Characterization of an unusual high-sodium natural chabazite and a variety of aluminium-rich chabazite-like species by ²⁷Al and ²⁹Si magic-angle-spinning nuclear magnetic resonance spectroscopy (MAS NMR), scanning electron microscopy (SEM), powder X-ray diffraction (XRD) and compositional analysis is presented. A simple method to convert mineral chabazite to a new high-aluminium-content species, ‘Al-chab’, is presented which increases the ion-exchange capacity of the material to the theoretical zeolite limit. Crystalline contaminants indigenous to mineral chabazite are removed and can serve as nutrients for the formation of this new species. The results show that Al-chab forms directly from solution using chabazite as a seeding template. Partially converted samples were found to be mixtures of the chabazite and Al-chab, and not an intermediate species. Another high-aluminium-content chabazite-like species, synthetic zeolite K-G1, and Al-chab are contrasted using powder XRD, crystallite morphology and structure fragment precursors observed by ²⁹Si NMR.