Synergistic effects of fly ash-derived magnetic acid-base trifunctional catalyst with electrolytic transesterification for biodiesel production

The production of biodiesel as a renewable liquid fuel faces two major constraints, the high energy consumption of conventional thermal transesterification and the challenge of reusing catalysts. This study presents a synergistic system coupling the acid-base and magnetic trifunctional NaOH/FAU@Fe3O4 catalyst with electrolytic transesterification for biodiesel production, using acidified palm oil as the feedstock. FAU-type zeolites were first synthesized from fly ash via an alkali fusion-hydrothermal method, followed by Fe3O4 incorporation and NaOH loading to obtain the trifunctional catalyst. The catalyst was characterized to reveal its physicochemical properties and synergistic interactions with the substrate molecules in the electrolytic transesterification reaction. Further, response surface methodology with central composite design (RSM-CCD) was employed to optimize the electrolytic transesterification parameters. A biodiesel yield of 98.15% was achieved under the optimal conditions (methanol to oil molar ratio of 7:1, catalyst dosage of 2.9 wt%, reaction duration of 2 h and input voltage of 48 V). Notably, the synergistic system exhibits strong acid resistance and acceptable reusability, enabling efficient conversion of low-quality feedstocks. Meanwhile, the physicochemical properties of the produced biodiesel met ASTM standards, confirming the suitability of the synergistic system for biodiesel production.