ESTABILIDADE OXIDATIVA DE BIODEISEL DE SOJA COM ADITIVOS DE Ipomoea batatas (L.) Lam.

Abstract

Biodiesel is a biofuel used in mixture with petroleum diesel throughout the Brazilian territory. However, considering its chemical composition, it is susceptible to oxidative and autoxidative processes. Exposure of biodiesel to air, moisture and light during storage and transport compromises the quality of the fuel. The oxidative stability of biodiesel is established, in Brazil, by ANP norms, with a minimum required of 12 hours. Therefore, it is necessary to use antioxidants so that biodiesel can be commercialized. To reach the minimum limit of oxidative stability, predicted by the ANP, the industry predominantly uses synthetic antioxidants. However, these additives are toxic, expensive and derived from petroleum. Based on the above, this work presents a feasibility study of the use of natural antioxidant additives based on extracts of bark, pulp and branches of a genotype of Ipomoea batatas (L.) Lam. Ethanol extracts of bark, pulp and branches obtained through continuous extraction in a Soxhlet system were used. Oxidation stability measurements were carried out in accordance with the Standards contained in the ANP with Rancimat equipment at 110oC. The concentrations of antioxidants used were between 0.05; 0.10; 0.15; 0.30 and 0.50% (w/w). The variances in relation to the induction time were determined using the Tukey test. The results showed an increase in the induction period, when compared to pure biodiesel, in all concentrations of pulp, bark and branch extracts. The most expressive increase was obtained with the pulp extract at a concentration of 0.50% (m/m). By the analysis of aligned contrasts it was possible to verify that all the extracts had antioxidant activity when applied in biodiesel and by the analysis of variance it was possible to verify the behavior of the vegetal extracts against the biodiesel and the influence of the concentration and composition of the extract. These results indicate that natural additives can be used as a sustainable alternative to increase the oxidation stability of biodiesel.