Effects of using substrate heating method for the preparation of zeolite coatings containing faujasite

The substrate heating method was used to crystallize coatings containing faujasite zeolite on stainless steel plates from a clear reaction mixture. Conventional synthesis was also applied under similar conditions for comparison. The coatings obtained were characterized by X-ray diffraction (XRD), field emission gun scanning electron microscopy (FEGSEM), energy dispersive X-ray spectroscopy (EDX) and thermal gravimetry (TG). In general, mixed phases containing faujasite were determined to exist in the coatings prepared. The crystallinities as well as the phases of the zeolite coatings varied with the synthesis conditions used. The Si/Al ratios of the coatings were relatively low when substrate heating was applied, indicating the presence of zeolite X type faujasite, instead of the Y type obtained from conventional synthesis. When the substrate heating method was used, the mass equivalent coating thickness increased from about 30–150 µm, under similar synthesis conditions with the conventional method. Additionally, enhancements of up to about 4% and 23% were obtained in the water capacities of the coatings at 350 °C and 100 °C, respectively.