Improvement of the Oxidation Stability of Biodiesel from Waste Cooking Oil Using Various Antioxidants

Efforts to meet the constantly increasing global energy demand without adverse environmental impacts have led to the development of alternative energy sources. Biodiesel, a biomass alternative, has been identified as a source with a potential substitute for fossil fuel-derived diesel for transportation purposes. Oxidation degradation is one of the primary obstacles hindering the commercialization of biodiesel, which has been established as a viable alternative to diesel derived from fossil fuels. In this research, the Rancimat method is used to find out how well three antioxidants—vitamins A, C, and E—improve the stability of biodiesel made from waste cooking oil. At a concentration of 1000 ppm, the selected antioxidants improved the oxidation stability of biodiesel. Vitamin C improved the waste cooking oil biodiesel induction period from 0.79 to 7 h most effectively. These results are because of the low bond dissociation energy (318.5 kJ/mol), the molecular weight (176.16 g/mol), and the formation of acetyl palmitate, known to possess antioxidant properties in oils. When antioxidants A and C (induction period = 12.9 h) and C and E (induction period = 7 h) were combined in a ratio of 1:1, they were more effective. The combination of A and E negatively affected the oxidation stability of waste cooking oil biodiesel, resulting in an induction period of 0.33 h. Herein, the present research has demonstrated that using antioxidant C, either alone or in conjunction with other natural antioxidants, positively impacts the oxidation stability of waste cooking oil biodiesel.