Manipulating the intricate relationship between synthesis parameters in the induction heating method for the preparation of thick and crystalline zeolite coatings

Preparation of durable zeolite coatings of desired phases with high crystallinities, high purities, and high thicknesses on large substrate surfaces in reasonable time presents significant challenges. The induction heating method developed recently has been shown to be a promising tool for providing solutions to these challenges. This study focuses on manipulating the intricate relationship between synthesis parameters in the induction heating method to advance the coating preparation process for water adsorption applications. The coatings were characterized by X-ray diffraction (XRD) and thermogravimetry (TG). The substrate and solution temperatures, determined by the reactor inlet and outlet temperatures, and the solution volume and time, were shown to affect the interplay between significant phenomena, such as the crystallization rate, amorphous material deposition rate, diffusion of precursors in the coating and metastable phase transformations, as a function of time and location along the substrate, during synthesis. With the understanding gained, uniformly and highly crystalline coatings of thicknesses of up to about 400 μm, mainly consisting of zeolite NaX, have been successfully prepared in a single synthesis step by induction heating in this study. This thickness is about twice the value previously reported to be obtained for the same synthesis time and solution composition, by the same method.