Role of ethanol in sodalite crystallization in an ethanol-Na ₂O-Al₂O₃-SiO₂-H₂O system

Crystallization of sodalite was studied in an ethanol-Na ₂O-Al₂O₃-SiO₂-H₂O system. The addition of ethanol was observed to significantly affect the crystallization process and final crystal sizes and morphologies. Micron-sized sodalite particles with disc and thread-ball-like shapes were produced at low ethanol contents whereas sodalite particles with core-shell nanostructures were dominant at high ethanol contents. Prolongation of the reaction time led to hollow architectures with polycrystalline shells. This study showed that the formation of core-shell and hollow sodalite structures followed a surface crystallization process, including the following steps: the formation of amorphous spherical aggregates, multiple nucleation on the surface, growth of shell nanocrystals, and amorphous core digestion. The present work provides new insights into a better understanding of the role of ethanol in zeolite crystallization, and controllable synthesis of sodalite crystals with different morphologies.