Antioxidative performance and oil-soluble properties of conventional antioxidants in rubber seed oil biodiesel

The resistance of biodiesel fuels to autoxidation can be improved by mixing them with antioxidants. In this study, the effectiveness of 10 conventional antioxidants added to rubber seed oil biodiesel was investigated. According to the Chinese Pharmacopoeia (2015 version), the soluble interval was evaluated and Rancimat method using EN 14112 was adopted to determine the antioxidative effect of conventional antioxidants in rubber seed oil biodiesel. Moreover, this study also revealed the oil-soluble properties of conventional antioxidants in biodiesel at different temperatures and investigated the change rule of their oil-soluble properties. The results indicated that 10 common antioxidants could improve the antioxidative performance of rubber seed oil biodiesel to a certain extent; however, their effects were quite different. At room temperature (20 °C), conventional antioxidants exhibited relatively poor oil-soluble properties, with great discrepancy. The decreasing order of oil-soluble properties of 10 conventional antioxidants in rubber seed oil biodiesel is as follows: BHA > TBHQ > D-TBHQ > PA > PG > OG > VC > MT > AP > GA. With increasing temperature, the oil-soluble properties of 10 antioxidants somewhat improved; however, their soluble interval changed only slightly. A weak relationship was observed between the antioxidative performance and oil-soluble properties of 10 conventional antioxidants. Noteworthy, in practical production applications, the antioxidative performance and oil-soluble properties of antioxidants are important factors in the selection of appropriate antioxidants.