Enhancement of metal-oxides bifunctional catalyst applied in biodiesel production from waste cooking oil via microwave-aided and conventional heating methods

Abstract

The present study developed metal-oxides bifunctional catalyst from eggshell waste, ferric sulfate, and zinc sulfate. The developed catalyst was applied to optimize biodiesel production from waste cooking oil (WCO) using Box-Behnken design by comparing the activity of the catalyst in microwave-aided technology (MAT) and conventional heating technology (CHT). Characterization analysis revealed that the catalyst was dominated by the crystalline phase of ZnO while the surface area and pore diameter of the catalyst were 14.24 m2/g and 9.81 nm, respectively. The synthesized catalyst contained mesoporous particles with strong acidic and basic active sites. Optimal conditions established for maximum biodiesel yield were methanol/oil molar ratio (15:1), catalyst loading (1 wt%), and reaction time (62 min) at a constant temperature of 70 °C for the CHT process with a corresponding biodiesel yield of 90.45 %. For the MAT process, the optimal conditions established were methanol/oil molar ratio (15:1), catalyst loading (2.5 wt%), and reaction time (20 min), at a constant irradiation power of 450 W, with a corresponding biodiesel yield of 98.7 %. Using the synthesized catalyst, the MAT process produced a higher WCO biodiesel yield at a shorter reaction time compared to the CHT process. The properties of the fuel produced indicate that it met biodiesel standards.