**6. DSC biodiesel samples**

The DSC curves were obtained in the device DSC-Q20 with cooling system RCS-90 from TA Instruments, using as a sample holder, aluminum crucibles with cover and stuck to both the crystallization and to volatilization. As a reference, a similar empty crucible was used. Nitrogen atmospheres with flow rate of 50 mL min-1 and heating rate of 20 °C min-1 (vaporization) and 5 °C min-1 (crystallization and melting) at temperatures from -80 to 550 °C.

### **6.1. DSC profile**

**Figure 7.** Profile of TG Fossil Diesel and biodiesel (BI 02) blends

262 Biofuels - Status and Perspective

**Figure 8.** Profile of DTG Fossil Diesel and Biodiesel (BI 02) blend

For the three biodiesels, there was only one endothermic event with a temperature around 250 °C. Thus it can confirm that the event was indeed observed in the TG vaporization of biodiesel. The differential scanning calorimetry was used to check the physical and chemical transitions occurring in the vaporization of soybean biodiesel process. According to the DSC curve, there is an endothermic transition for each biodiesel: BL showed a ΔH=329.1 J g-1, BI 01 showed a ΔH=252.5 J g-1 and BI 02 showed a ΔH=272.7 J g-1. These transitions can be attributed to the processes of vaporization of methyl esters [31]. Such events can be seen in Figure 9:

### **6.2. Biodiesel crystallization**

Comparing the curves of biodiesels (BL, BI-01 and BI-02) can be seen that all curves have two state transitions, the first liquid-liquid crystal formation, which is the solidification of a fraction rich in unsaturated compounds and the second, which is a freeze, which corresponds to the fraction rich in unsaturated compounds [32]. Crystallization of saturat‐ ed compounds is represented by an exothermic peak at around-5 °C. In this range crystallization BL has the lowest crystallization temperature, -4 °C, followed by BI-02 and BI-01 which crystallize to -2.8 °C and 1.9 °C respectively. The crystallization points of unsaturated compounds are below -50 °C, as observed for the BL, BI-02 and BI-01 have the second crystallization temperature of -61.2 °C, -59.8 °C and -57.6 °C, respectively, as observed in the curves of cooling to -80 °C in Figure 10.

Because the greatest amount of unsaturated compounds in soybean biodiesel be unsaturated compounds that peak is observable below – 50 °C is larger in area, requiring more energy to crystallize than the saturated compounds. The peak around-50 °C needed for the phase transition of 68 and 58 J g-1 to BL and BI-02 respectively compounds. The peak at around-5 °C needed 16 and 15 J g-1 to BL and BI 02 respectively compounds. BI-01 for the peak around -50

**Figure 9.** biodiesel sample DSC profile

**Figure 10.** Crystallization of samples of biodiesel – Cooling curve

°C took 32 J g-1 for the largest peak and 7 J g-1 for the smaller peak. For the peak at around 0 °C took 30 J g-1 for the phase transition.

In the heating curves from – 80 °C to 30 °C may be seen two peaks of the curves BL and BI-02, referring to melting of the unsaturated (-46 °C) saturated (0 °C) compounds. To BI-01 may be seen three peaks related to the two unsaturated compounds (-53 to -40 °C) and references to unsaturated compounds (5 °C). BI-01 showed different behavior in crystallization of unsatu‐ rated compounds, there were two peaks of the onset of crystallization while BL and BI-02, showed only a peak of crystallization.

**Figure 11.** Crystallization of samples of biodiesel – heating curve

This fact may be related to the type of oil used in biodiesel production. As is reused oil underwent oxidation and hydrolysis of their triglycerides, causing increase in conjugated *dienes* and *trienes* unsaturated bonds [5], causing another peak appears in the unsaturated region.

### **7. Future development areas**

**Figure 9.** biodiesel sample DSC profile

264 Biofuels - Status and Perspective

**Figure 10.** Crystallization of samples of biodiesel – Cooling curve

Various types of vegetable oils have been tested in the preparation of biodiesel (canola, soybean, corn, sunflower, castor beans, cotton, etc.). The type of oil to be used in the production of biodiesel depends on geographical factors, as each region produces a certain kind of oil, according to their fitness. In some European countries, for example rapeseed oil, Brazil is already in use, depending on the region, can be produced from soy, castor oil or babassu [6] oil. Another highlight is the use of oils used in frying whose nobler purpose was hitherto the production of soap or disposed of in a sanitary [33] landfill. The high price of vegetable oils has become non-competitive biodiesel economically forward to petroleum diesel, programs and government incentives are needed. The search for new raw materials for the production of biodiesel and are more environmentally friendly and economically viable.

Biodiesel is a cleaner-burning alternative fuel, produced from renewable resources, does not contain oil, but it can be added to form a mixture. Can be used in compression-ignition engines (diesel) without modification. Non-toxic, essentially free of sulfur and aromatics [34] com‐ pounds. Its main disadvantages include low pour point (on cold) and maintain fuel quality during long-term storage [35]. A good source for development would address this disadvant‐ age that has biodiesel.
