Atividade antioxidante de compostos fenólicos e aminado no biodiesel de babaçu: avaliação por Rancimat e calorimetria exploratória diferencial

Abstract

The antioxidant activity of phenolic (unsaturated cardanol or CDN-I, and IONOL) and amine (N,N’-di-sec-butyl-p-phenylenediamine or PDA) antioxidants on the thermo-oxidative stability of fatty acid methyl ester (FAME) of babassu oil were evaluated under accelerated conditions. Babassu FAME was obtained using a two-step transesterification reaction, via alkaline catalysis. The FAME samples were doped with the antioxidants at concentrations between 1 and 1000 mg/kg. The oxidation tests used the Rancimat method (EN 14112) and the Differential Scanning Calorimetry (DSC) method (ASTM E537). The physicochemical properties of babassu FAME and its blends with the three antioxidants were within the limits of RANP 45/2014, excepting kinematic viscosity. Regarding RANP 798/2019, almost all formulations exceeded the minimum induction period (IP) limit of 12 h, excepting pure babassu biodiesel and its CDN-I formulations with up to 100 mg/kg. The other results by Rancimat showed a significant improvement in IPs using 100 mg/kg of synthetic antioxidants IONOL and PDA (55 h and 180 h, respectively). By DSC, the thermal analyzes showed a considerable increase of the extrapolated onset temperature of the PDA sample (211.7 ° C), indicating a higher antioxidant activity of PDA when compared to the two phenolic antioxidants.