Oxidation resistance of biodiesel

Abstract

Oxidation resistance of biodiesel synthesized by ester interchange of vegetable oil and animal fat triglycerides with methanol was studied. When stored under common conditions (in the dark at 20–25°С), the biodiesel is stable for no less than a year. However, the thermal oxidation resistance of biodiesel is low. The results obtained by different methods suggest that the processes occurring in the course of thermal oxidative degradation include not only radical-chain oxidation but also various condensation reactions showing no correlation with the former process. With this fact taken into account, additives enhancing the thermal oxidation resistance of biodiesel to the level of petroleum fuels containing no additives and no biodiesel were found among shielded phenols and aromatic amines. These additives prolong the shelf life of biodiesel fuel, which today is as short as 3 months, and allow the admissible concentration of biodiesel in mixtures with petroleum diesel fuel (7 vol %) to be increased.