Improvement of the Oxidation Stability of Waste Cooking Oil Biodiesel Using Natural Antioxidants

Abstract

Abstract 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 the present study, the Rancimat method is employed to determine the efficacy of three natural antioxidants, vitamins A, C, and E, in enhancing the oxidation stability of biodiesel produced from waste cooking oil (WCO). At a concentration of 1000 ppm, the selected antioxidants improved the oxidation stability of biodiesel. Vitamin C improved the WCO biodiesel induction period (IP) from 0.79 to 7 hours most effectively. This is due to the low bond dissociation energy (BDE, 318.5 kJ/mol), the low molecular weight (Mw, 176.16 g/mol), and the formation of acetyl palmitate, which is known to possess antioxidant properties in oils. When antioxidants A and C (IP = 12.9 hours) and antioxidants C and E (IP = 7 hours) were combined in a ratio of 1:1, they were more effective. The combination of A and E negatively affected the oxidation stability of WCO biodiesel, resulting in an induction period of 0.33 hours. Herein, the present research has demonstrated that the utilisation of antioxidant C, either alone or in conjunction with other natural antioxidants, exerts a favourable impact on the oxidative stability of WCO biodiesel.