Thermal Properties of the Blends of Methyl and Ethyl Esters Prepared from Babassu and Soybean Oils

Fatty acid esters (methyl and ethyl) prepared from babassu nut oil were blended with the respective esters from soybean oil. These binary blends (babassu:soybean) were made in proportions of 10:90, 20:80, 30:70, 40:60, and 50:50 (vol%). The ester content of all the blends was higher than 96.5%, which is the minimum value required by the Brazilian National Agency of Petroleum, Natural Gas and Biofuels (Agencia Nacional do Petroleo, Gas Natural e Biocombustiveis, ANP). The thermal properties of the babassu, soybean and binary mixtures of esters were investigated by thermogravimetry-differential thermogravimetry (TG/DTG) and differential scanning calorimetry (DSC). The thermal stability of the blended biodiesels decreased as the total contents of the babassu esters increased. From the experiments it was found that babassu methanol biodiesel is stable up to 49.6 oC and the ethanol biodiesel is stable up to 53.7 oC in air. The methyl esters blends were thermally stable up to 83.2 and 56.8 oC, for 90:10 and 50:50 blends (soybean:babassu), respectively. The ethyl ester blends presented values of temperature ranges somewhat higher than the methyl esters, such as 85.2 and 64.5 oC for 90:10 and 50:50 blends, respectively. The esters from babassu oil have satisfactory performance at low temperatures with respect to the point of crystallization, which were below –9.8 oC for ethylic esters and –8.5 oC for methylic esters. A good correlation between the crystallization onset temperature and the increase in the concentration of the babassu oil esters was obtained in the mixtures analyses. In the 50:50 combination (babassu:soybean), the crystallization onset temperature were –6.73 and –9.12 oC for methyl and ethyl esters, respectively.