**8. Conclusions**

Biodiesel production in the laboratory of alkaline transesterification reaction and the treatment of methyl esters were successful. All parameters except the oxidative stability were within the established in ANP Nº 45/2014, indicating a good quality biodiesel. The oxidative stability below specification may have been due to lack of the addition of antioxidant.

Industrial biodiesels showed some parameters out of specification. BI-01 showed three parameters out of specification (ester content, carbon residue content of glycerol), which is probably associated with the raw material. The BI-02 showed only one parameter out of spec (Acid Value) which can be associated to microbial growth in storage tanks or the fact that after neutralization of excess acid base with the same has not been washed properly.

By TG curves, soybean oil showed higher thermal stability than Biodiesel and Fossil Diesel. In oil, the onset of decomposition was 358 °C, while biodiesels began to vaporization around 160 °C. For fossil diesel mass loss started around 30 °C, whereas the increase in the binary mixtures Biodiesel slightly increased thermal stability.

The biodiesels were tested at a heating rate of 5, 10, 15 and 20 °C and all were obtained in the same profile.

The DSC curves of biodiesels calorimetric showed a similar profile. The analysis of biodiesels had only one endothermic peak on the vaporization of the esters. Comparing ΔH of biodiesels BL> BI-02> BI-01 with the respective ΔH 329.1> 272.7> 252.5 J g-1.

The TG curves of the binary mixtures have very similar profile to that of fossil diesel, biodiesel from the addition made to increase the thermal stability of the mixture. When compared with fossil diesel, it begins to loss mass around 30 °C and the Biodiesel that begins to vaporization at 160 °C there has been a small increase in the temperature at which it begins to lose mass, and that the More mixture containing biodiesel B25, takes a longer time to fully decompose when compared with the mixture of 5 %, indicating greater thermal stability.

In the curves of crystallization of biodiesels (BL, BI-01, BI-02) shows that all the curves have two transitions of liquid-solid state, one that represents the solidification of a fraction rich in saturated compounds and the other corresponding to rich fraction unsaturated compounds. Crystallization of saturated compounds is represented by an endothermic peak at around 0 °C, and the unsaturated compounds endothermic peak around – 60 °C.
