Additive-free synthesis of layer-like Faujasite-type zeolite X

Abstract

Faujasite-type zeolite X (FAU-X) with a layered morphology was successfully synthesized by an additive-free route at a crystallization temperature of 90 °C for 24 h. The sample was dried at 70 °C for 40 h (designated FAU) and then calcined at 450 °C for 5 h (designated FAU-450). Both samples were analyzed by X-ray diffraction (XRD), which confirmed the formation of the FAU structure. In addition, from the XRD data and Energy Dispersive Spectroscopy, the Si/Al ratio was determined to be ~ 1.20, which is typical for FAU-X zeolite. Scanning Electron Microscopy revealed that both samples have morphologies corresponding to sheet agglomerate, with FAU-450 having an agglomerate size of 1.41 µm and a sheet thickness of about 0.13 µm. These values are close to the data obtained by transmission electron microscopy, where an agglomerate size of ~ 1.39 µm and a sheet thickness of ~ 0.12 µm were observed. From the Tauc’s plots for FAU and FAU-450, the values of direct and indirect band gaps were determined and found to be close for both samples. In the case of FAU-450, values of 4.35 eV and 3.12 eV were obtained for the direct and indirect transition, respectively. From the TGA/DTA data, it was found that FAU loses mass due to dehydration of the zeolite at temperatures below 350 °C, while the sample is structurally stable up to 700 °C.Graphical