Oxidative Stability of Biodiesel Using Tea Leaves

A comparative study of oxidation stability of biodiesel prepared via transesterification and sonication routes was carried out. The polyphenols from tea extract, while acting as an antioxidant could prolong the onset of degradation by about two weeks. Difference in viscosity and peroxide value were used as an indicator of oxidation. Though the polyphenols could not prevent a viscosity increase that corresponds to the beginning of rapid polymerisation but the rate of the increase was quiet slow. Polyphenols from tea extract stabilizes the methyl ester by reducing the rate of peroxide formation and by stabilising the viscosity. A sudden rise of viscosity was attributed to onset of secondary oxidation marked by an increased release of free fatty acid. The onset of secondary oxidation showed a marked delay in ultrasonicated samples as compared to transesterification.