Novel preparation of amorphous aluminosilicates via amorphous borosilicates by B-to-Al exchange

Abstract

The preparation of precursor amorphous materials for zeolite synthesis is one of important units, which has a significant impact on zeolite crystallization behavior. In this study, we propose a novel preparation method to obtain amorphous aluminosilicates used for zeolite synthesis. It consists of in the precipitation of amorphous borosilicates followed by B-to-Al exchange, which is inspired by post-synthesis treatment performed in zeolites. Amorphous borosilicates prepared under different conditions, aluminosilicates obtained by B-to-Al exchange, and CHA zeolites synthesized using the amorphous aluminosilicates were studied by various microstructural analyses, including UV-Raman spectroscopy, solid MAS NMR, and High-energy X-ray total scattering (HEXTS)/pair distribution function (PDF) analysis. The interesting finding is that Si/B ratios in the first mixture composition affect the subsequent progress of B-to-Al exchange and zeolite synthesis steps. In addition, the amorphous aluminosilicates prepared from amorphous borosilicates by B-to-Al exchange led to a wide synthesis window of CHA zeolite such as the reduction of the alkali concentration and the synthesis time. These results suggest that the novel amorphous aluminosilicates prepared from amorphous borosilicates by B-to-Al exchange could become a promising raw material for optimizing zeolite synthesis.