Efficient photocatalytic esterification of waste cooking oil over empty fruit bunches ash-supported TiO2

Biodiesel production from waste cooking oil (WCO) holds promise as a renewable and sustainableenergy source. However, high levels of free fatty acids (FFAs) in WCO require efficient pre-treatment before transesterification. Utilizing solar energy for heterogeneous catalytic reactionsoffers an alternative to thermal-driven processes. TiO2EFBA, synthesized via the wet impregnationmethod, exhibits distinctive physicochemical properties confirming the successful incorporationof titanium dioxide (TiO2) onto the metal oxides of empty fruit bunches ash (EFBA), thereby en-hancing the catalyst’s performance and stability. Results showed that TiO2EFBA exhibits superiorFFA conversion compared to TiO2alone. Under optimized reaction conditions, employing 4 wt%TiO2EFBA catalyst, 20:1 methanol to oil molar ratio, and 2 h reaction time at room temperatureunder Ultra Violet (UV) light, achieves a remarkable 78% conversion rate of FFAs in WCO.Mechanistic investigation reveals the crucial role of electron/hole (e−/h+) species in reducingFFAs by suppressing the e−/h+mechanism. Notably, TiO2EFBA facilitates easy separation andcan be reused for 10 cycles, demonstrating its stability as a heterogeneous photocatalyst.