Evaluation of the oxidation stability of biodiesel stabilized with antioxidants using the PetroOXY method

In this paper, the PetroOXY method has been mainly used to determine the oxidation stability of biodiesel stabilized with five synthetic antioxidants. The differences in the antioxidant activity of these phenolic compounds could be clearly distinguished with this method. Pyrogallol (PY) and propyl gallate (PG) prove more efficient in inhibiting biodiesel oxidative degradation than butylated hydroxyanisol (BHA) and butylated hydroxytoluene (BHT). BHT and BHA act more efficiently in the PetroOXY test than in the Rancimat method with regard to stabilization factor. Tert-butylhydroquinone (TBHQ) displays the weakest antioxidant activity in PetroOXY, inconsistent with the best stabilizing effects shown in the Rancimat method. The influence of reaction temperature on the induction period is very pronounced. From the plots of logarithm of induction period against temperature, the storage life of biodiesel at ambient temperature can be predicted with the extrapolation method, and the temperature sensitivity of these antioxidants can also be obtained. Changes in the mechanism of the oxidation process with the introduction of antioxidants may give variations in the temperature dependence.