Zeolite Synthesis: A Comparative Analysis of Conventional Hydrothermal and Microwave-Assisted Methods

Abstract

ZSM-5 zeolite was synthesized using both conventional hydrothermal and microwave-assisted hydrothermal techniques to investigate the effect of the synthesis approach on its structural and physicochemical characteristics. The precursor gel was subjected either to control aging or to microwave irradiation prior to hydrothermal crystallization at 160 °C under autogeneous pressure. X-ray diffraction (XRD) patterns confirmed the successful formation of highly crystalline MFI-type ZSM-5 in both cases, with comparatively higher peak intensity observed for the microwave-treated sample, indicating improved crystallinity. FTIR spectroscopy revealed characteristic framework vibrations, including bands associated with double five-membered ring (D5R) units, confirming the development of the ZSM-5 structure. Thermo gravimetric and differential thermal (TG–DTA) analyses showed sequential removal of adsorbed water and organic template species, demonstrating good thermal stability of the synthesized materials. Scanning electron microscopy (SEM) images displayed well-defined crystalline morphology, with the microwave-assisted method yielding relatively uniform and elongated nanocrystals as a result of rapid and homogeneous nucleation.