This study aimed to synthesized zeolites via a hydrothermal process in an alkaline medium using coal fly ashes as an alternative source of silicon. The zeolites were evaluated for their crystallinity, morphology, and surface area. The characterization of the sample revealed that the zeolite type sodalite was synthesized, and quartz and mullite were identified as by-products. The microstructure of the powders showed clusters with specific surface areas of approximately 10 m(2)/g. The synthesized sodalite was used as a catalyst for transesterification of soy oil to obtain a maximum conversion of 95.5 wt% at 65 degrees C with a 4 wt% catalyst concentration, a 12:1 methanol-to-oil molar ratio, and a reaction time of 2 h. The mechanistic pathway for sodalite catalyzed transesterification and the possible formation of active sites was proposed. (C) 2016 Elsevier Ltd. All rights reserved.