Hybrid CaO/ZnFe₂O₄ Modified with Al₂O₃ as a Green Catalyst for Biodiesel Production from Waste Cooking Oil

In this work, biodiesel was produced from waste cooking oil (WCO) via a green catalyst of CaO-ZnFe₂O₄ modified Al₂O₃. The catalyst was characterized using Fourier-transform infrared spectroscopy (FTIR), X-ray powder diffraction (XRD), scanning electron microscopy (SEM), energy dispersive x-ray (EDX), SEM-mapping, Brunauer-Emmett-Teller (BET), transmission electron microscopy (TEM) analyses. The catalyst performance was studied in the transesterification reaction of WCO conversion to biodiesel. The catalytic activity increased with the combination of nanoparticles effect and support catalysts obtained biodiesel yield of nano-Al₂O₃, nano-CaO, ZnFe₂O₄, CaO-ZnFe₂O₄, and CaO-ZnFe₂O₄/Al₂O₃ is 36.86%, 67.16%, 74.83%, 86.54%, and 93.41%, respectively. The best biodiesel yield was 93.41% with a mass ratio of Al₂O₃ to CaO-ZnFe₂O₄ (2:1). The physicochemical properties (acid number, density, kinematic viscosity, flash point, and cetane number) of biodiesel under the optimal conditions agreed with the ASTM standard. These results show that the developed nanocomposite has great potential to reduce biodiesel production costs because derived from WCO. In conclusion, CaO-ZnFe₂O₄ modified Al₂O₃ as a catalyst has a high potential for biodiesel production on a large scale.