Formation domain of SDA-free Y faujasite small crystals

Abstract

Throughout this study, the SiO₂, Na₂O and H₂O contents in the starting gel were modified in order to understand their influence on obtaining pure Y faujasite small crystals. Results were assembled in a ternary phase diagram (SiO₂–H₂O–Na₂O). Furthermore, thorough characterization using multiple structural and physicochemical methods is reported for all the pure faujasite samples, in order to emphasize the effect of H₂O, SiO₂ and Na₂O amounts on their structural (the crystallization rate and the Si/Al molar ratio of the framework) and textural properties (the micropore volume and the crystal size). Good yields in Y faujasite small crystals were obtained when optimizing the starting gel composition compared to the one provided in the literature (typically below 10 wt% of the engaged Si). The results show that the gel domains that are able to give pure Y zeolites are very restricted, making predictions very complicated.