THE IMPORTANCE OF Medicago saliva EXTRACT ON THE OXIDATIVE STABILITY OF BIODIESEL

摘要

Biodiesel is an alternative diesel fuel produced through the transesterification of vegetable oils or animal fats and it is composed of esters with long chain fatty acids, unsaturated or saturated. Oxidation reactions determine the degradation of biodiesel, affecting its oxidative stability. The oxidation stability is determined by the property of fuel to resist to the chemical changes during storage. Chemical changes appear at the main qualitative indices: acid value, iodine number, refraction number, viscosity, induction period, cetane number and flash point. The use of natural and synthetic antioxidants may be a way to improve the oxidative stability of biodiesel. Although oils contain large amounts of natural antioxidants, they are lost during processing. The aim of this study was to determine the influence of the oil extracted from Medicago saliva on the oxidation of biodiesel produced from sunflower oil. Samples of biodiesel added to the oil extracted from Medicago saliva (1%) were stored for 12 months at room temperature. The acid value, the refraction number and the induction period were monthly determined. Gaseous emissions (CO, CO_2, hydrocarbons, O_2) released by burning biodiesel in a diesel monocyclic R Y50 engine, were determined using a COSTECH ECS 4010-CHNS-O device. Values obtained for samples of biodiesel in a mixture with oil from Medicago saliva showed increased stability to oxidation compared with that of pure biodiesel.