Avaliação do efeito sinérgico entre antioxidantes convencionais e aditivos contendo grupo antraquinona na estabilização de biodiesel de soja

Abstract

The stability of biodiesel and/or oils depends on the presence of unsaturated fatty acids in its composition as well as efficiency in the use of stabilizing additives during handling and storage conditions. Additives that provide greater antioxidant efficiency ensure better storage conditions, and improve engine performance with an increase in the lifetime of the parts. Moreover, the control of biodiesel degradation helps to encourage its adhesion to the global energy matrix as a renewable energy source, offering many environmental, economic and social advantages. Therefore, in this work an innovative study by using combinations containing alternative additives and conventional antioxidants as a way to control the degradation of soybean biodiesel is presented. To meet these goals, we studied different concentrations and different combinations containing the dye quinizarin (QNZ) and Solvent Blue 59 (SA-59) together with the conventional antioxidants tert-butylhydroquinone (TBHQ), propyl gallate (PG) and butylated hydroxytoluene (BHT) and their effects on the stability of soybean biodiesel. The degradation of the samples under controled thermal conditions were determined by physicochemical analyses and Rancimat® test. The analyses showed that the additive-free biodiesel undergoes further degradation during the storage period, especially at higher temperature. However, with the use of the proposed combinations there was a more effective control of the degradation process even in low concentrations, which varied between 65 and 150 mg kg-1 than the single addition of conventional antioxidant at a concentration level of 500 mg kg-1. These results meet the objectives of the work and prove that alternative additives can effectively control the degradation of biodiesel, whose cost/benefit ratio is highly satisfactory, reducing from 70 and 88% concentration of additives to be inserted into biodiesel to meet the specifications required by the Brazilian legislation.