Oxidative Stability of Soybean Biodiesel in Mixture with Antioxidants by Thermogravimetry and Rancimat Method

F. H. N. Souza, F. J. N. Maia, S. E. Mazzetto, T. L. Nascimento, N. C. de Andrade, A. L. N. F. de Oliveira and M. A. de Sousa Rios

Abstract
The effects of three antioxidants on the oxidative stability of soybean biodiesel were studied using two techniques: Thermogravimetry (TG-DTG curves) and the Rancimat method. The onset (Tonset) and endset (Tendset) temperatures were determined from TG curves, the peak temperatures (Tpeak) were determined from DTG curves, and induction times were determined by the Rancimat method. The compounds butylated hydroxyl anisole (AO1), 2,6–di-tert-butyl-4–methylphenol (AO2) and the mixture 2,6–di-tert-butylphenol + 2,4,6–tri-tert-butylphenol (AO3) were studied and among the hindered phenols evaluated the AO1, AO2 and AO3 proved to protect the soybean biodiesel against thermo-oxidation process, and in the Rancimat method AO2 proved to be more effective than AO1 and AO3 for protection of the biodiesel against oxidation process in the conditions of the method.

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Keywords
IPDT, TG, Rancimat, 2,6–di-tert-butyl-4–methylphenol, butylated hydroxyl anisole