Oxidation Stability of Soy and Palm Based Biodiesels Evaluated by Pressure Differential Scanning Calorimetry

The oxidation stabilizing effect of a substituted phenol on soy and palm based biodiesels was investigated according to the ASTM E2009 standard. Pressure differential scanning calorimetry (PDSC) measurements were used to evaluate the influence of oxygen pressure. A relationship was derived to describe the correlation between oxidation onset temperature and oxygen pressure. Additional standard differential scanning calorimetry (DSC) and thermogravimetric analysis tests were performed in order to evaluate other thermal effects of the additive. The different behavior of both fuels was explained on the basis of their different physical and chemical properties. PDSC results were compared with the values obtained by the Rancimat method and the crystallization temperature observed by standard DSC was compared with the cold filter plugging point obtained according to the EN 116 standard.