Modelling of relative protection factor of antioxidants TBHQ, BHT and BHA in mixture with biodiesel

Antioxidants are an alternative to prevent or retard the degradation of biofuels. In this study was utilized biodiesel obtained from the soybean oil transesterification, by methylic route, using sodium methoxide as catalyst. The synthetic antioxidants, butylhydroxyanisole (BHA), terc-butylhidroquinone (TBHQ) and butylhydroxytoluene (BHT) were added separately and in misture to the biodiesel. The induction period and the relative protection factor (RPF) were evaluated by the Rancimat method at temperatures 110, 115, 120 and 125ºC. The results showed that the highest RPF was for the tests containing the antioxidant TBHQ. The multi-response optimization indicated that the mixture containing only TBHQ was the condition with better performance on the RPF, with the predicted value of 31.27 at a temperature of 110°C. A similar value was obtained experimentally, showing the efficiency of design used and the validity of the obtained models confirmed by statistical analysis of the obtained data.