Abstract <p>This work presents a detailed comparative study of two methods for the synthesis of ZSM-5 zeolite (SiO₂/Al₂O₃ = 50) aimed at obtaining a material with a reduced sodium content: conventional hydrothermal synthesis and an innovative method involving microwave activation of the reaction mixture. The relevance of the study is associated with the search for energy-efficient and rapid approaches to the preparation of zeolite catalysts with improved structural and functional properties for petroleum refining and organic synthesis processes. It was experimentally demonstrated that microwave activation not only significantly reduces the crystallization time compared with conventional hydrothermal synthesis but also affects the morphology and quality of the resulting crystals. X-ray phase analysis unambiguously confirmed the formation of the target MFI-type zeolite structure in all samples; however, significant differences in phase purity and degree of crystallinity were revealed. Based on comprehensive differential thermal analysis, a detailed mechanism of phase and structural transformations occurring during synthesis and subsequent heating was proposed, explaining the behavior of the materials during dehydration and their enhanced thermal stability. IR spectroscopy data demonstrated a direct correlation between the synthesis method employed and the state of hydroxyl groups in the resulting zeolites, which is critically important for their acidic and, consequently, catalytic properties. The results obtained make a substantial contribution to the fundamental understanding of zeolite synthesis and are of considerable practical importance for the development of advanced energy-saving technologies for the preparation of zeolite catalysts with specified and controllable structural, adsorption, and catalytic characteristics.</p>