(80e) Oxidative Stability of Biodiesel From Castor Oil Fatty Acid Methyl Esters

Biodiesel is an alternative diesel fuel consisting of alkyl monoesters of fatty acids prepared from vegetable oils. It has been the focus of a considerable amount of recent research because it is renewable, biodegradable and reduces the emission of some pollutants. However, biodiesel has lower oxidation stability as compared with petroleum diesel because biodiesel has high content of unsaturated methyl esters, especially poly-unsaturated methyl esters which can be easily oxidized such as methyl linoleate (C18:2) and methyl linoleate (C18:3), which lead to the formation of decomposed compounds such as acids, aldehydes, esters, ketones, peroxides and alcohols. These products not only affect the properties of biodiesel, but also bring problems for engine operation. Consequently, storage of biodiesel over extended periods may lead to degradation of fuel properties that can compromise fuel quality.

The objective of this study was to determine the oxidative stability of biodiesel produced by transesterification of castor oil. The evaluation was conducted by means of a rapid oxidation method (PetroOxy), at temperatures of 100,120 and 140°C at time intervals between 0 and 60min, and at pressure 700kPa. The Acidity Index (AI) of each oxidized sample from the accelerated tests was measured in order to evaluate the kinetics behavior of the oxidation process.