Comparison of antioxidative performance of synthetic and natural-derived antioxidants for oxidative stabilization of biodiesel

Abstract. In this work, liquid extracts of banana, mango, and fruit palm peels recovered via supercritical fluid extraction (SFE) were used as natural antioxidants whose antioxidative effectiveness was compared with those of their synthetic antioxidant counterparts namely quercetin, gallic acid, and beta-carotene on improving biodiesel’s resistance to oxidation reaction. Blends of the two antioxidant types were tested in mono (single antioxidant) and binary (mixture of two antioxidants) dosages. The results show that a superior antioxidative effect was manifested by the natural antioxidants extracts as evidenced by having higher induction period (IP) values of 6.3 and 8.5 h for the mono and binary-blended biodiesel respectively, compared to 4.5 and 6.7 h for the corresponding synthetic antioxidants-blended peers. However, the presence of water- soluble polyphenols in the natural extracts was identified as the driving factor for the enhanced solubility of the natural antioxidant extracts giving rise to faster reaction by the hydrocarbon chains of the antioxidants and that in the biodiesel, and subsequent deceleration of the radical chain growth.