USO DE RESÍDUO DE Annona muricata L. COMO ANTIOXIDANTE EM BIODIESEL

Abstract

Biodiesel, is an alternative fuel to diesel oil and from a renewable source, gradually gaining more prominence. However, its susceptibility to oxidation, due to its main composition of unsaturated fatty acids, makes this aspect one of the biggest challenges to be improved in biodiesel. Antioxidants are an alternative to prevent or retard biofuel degradation. Soursop (Annona muricata L.) is a native fruit of tropical America, with important antioxidant activity, besides high concentration of phenolic compounds. Peels form about 20% of the soursop fruit and are usually discarded as a waste product. The aim of this work was to use the residue from the peel of soursop as antioxidant source and evaluate its performance in increasing the oxidative stability of biodiesel. Extractions were carried out using different pH solvents (hydrochloric acid, pH=1; methoxide potassium, pH=14; and methanol, pH=7) and different concentrations (1 g/L, 3 g/L and 5 g/L) of mass/volume. The extract solutions obtained were added in the biofuel production process. Accelerated oxidation tests were performed on Rancimat 873 Metrohm® at a temperature of 110 °C according to the EN 14112. Additional techniques were executed to evaluate the quality biodiesel such as, specific mass, infra-red analyses, electrical conductivity, acidity index, flash point, water content, and color and appearance. An 3² factorial experiment design was carried out. All experiments, except one extraction (hydrochloric acid, pH=1; 1 g/L), surpassed the minimum induction time of 8 h established by the ANP. The best result was obtained with a concentration of 3 g/L, reaching an induction time of 10,30 h with neutral extract (methanol). Results showed that the soursop peel has antioxidant potential, that could be used as a natural antioxidant in biodiesel, ensuring low toxicity and preventing the oxidative biodiesel process.