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Chabazite synthesis from commercial zeolite Y

CHA-type zeolite is one of the most important zeolites that found application in important industrial processes and exhaust gas treatment. The aluminophosphate counterpart of CHA structure is relatively easy to synthesize, whereas the production of aluminosilicate analogue is difficult. The simplest way to obtain aluminosilicate CHA is to transform zeolite Y under hydrothermal conditions. However, this approach has certain limitations in term of framework composition and particle size of ultimate product. In fact, the mechanism of hydrothermal transformation of one zeolite framework type into another is not yet well understood. The preceding studies of some transformations have shown that the first step in reaction is the dissolution of the starting zeolite, followed by the appearance of the new phase. It was shown that these transformations are solution mediated processes and various intermediates, which does not provide clues to the mechanism of zeolite transformation, were found. Herein, we report on the conversion of commercial zeolite Y (FAU) into chabazite, in KOH solution at 100 °C. The reaction course was followed using powder X-ray diffraction, Raman and NMR spectroscopy, scanning and transmission electron microscopy as well as dynamic light scattering technique. The formation of secondary building units, prior to the formation of long range order in the solid was observed. The results obtained in this study shed a new light in the mechanism of the CHA formation and represent additional contribution in the understanding of the processes taking place during zeolite-zeolite conversions.

intrazeolite conversion; chabazite; faujasite; mechanism

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