Efficient Antioxidant Formulations for Use in Biodiesel

Abstract

Biodiesel has a lipid origin; thus, antioxidants commonly used in oils and fats have been adopted for the improvement of the oxidative stability of biodiesel. However, these antioxidants have not shown the same efficiency when they are applied to biodiesel. This fact points out the need to investigate additives that warrant the oxidative stability of biodiesel, especially during long storage periods. In this paper, antioxidant formulations were developed for application in biodiesel, from blends including the synthetic antioxidants butylated hydroxytoluene (BHT), tert-butylhydroquinone (TBHQ), the chelating agent citric acid, and organic rosemary extracts. The antioxidants were applied at different concentrations and combinations and were evaluated by the Rancimat method, EN 14112, and by the pressurized PetroOXY method. The results showed that for ethanol soybean biodiesel, the antioxidant compositions formed by TBHQ (2000 mg kg–1) and citric acid (500 mg kg–1) and by the chloroform rosemary extract (2000 mg kg–1) and citric acid (500 mg kg–1) were the most effective in delaying the oxidative process, in a manner independent of the evaluation method. For the methanol cottonseed oil biodiesel, the best result was obtained using the combination of 1500 mg of TBHQ with 1500 mg of ethanol rosemary extract. However, the formulations using low concentrations of rosemary ethanol extract and citric acid induction periods of >6 h were obtained, reaching the limit specified by European Standard EN 14214.