Evaluation of oxidative stability of soybean biodiesel using ethanolic and chloroform extracts of Platymiscium floribundum as antioxidant

Abstract

The objective of this work was to evaluate the effect of Platymiscium floribundum ethanolic and chloroform extracts on the oxidative stability of soybean biodiesel using the Rancimat and DSC methods. The soybean biodiesel was obtained by transesterification. The antioxidant activity of the extracts was also evaluated by the free radical scavenging (DPPH) method and the total phenolic content by the FolinCiocalteu method. Both extracts showed antioxidant activity, reducing the DPPH by about 90%, and the total phenolic content of the ethanolic and chloroform extracts were 2.87 and 3.10 mg GAE/100 mg of extract, respectively. The extracts showed to be very efficient in retarding the oxidation of soybean biodiesel since the induction period increased from 4.53 h to 18.09 h (PFeEtOH, 10000 mg/kg) and 17.58 h (PFeCHCl3, 10000 mg/kg). Both extracts showed high thermal stability with Ton-e of 405.76 °C (PF-CHCl3) and 396.79 °C (PF-EtOH). The presence of the extracts increased the activation energy of the samples between 12.3% and 37.0%. The increase of the activation energy represents an improvement of the oxidative stability of biodiesel. All results confirmed the action of the antioxidants present in the extracts on controlling the oxidation reactions in biodiesel.