**4. Thermoanalytical methods**

from 2 to 7% FFA, Free Fat Acid, when an alkali catalyst (e.g. KOH) is added to these raw materials FFA react with the catalyst to form soap and water. The soaps formed during the reaction are removed with the glycerol in the aqueous washing step. When the concentration of FFA is too large soaps inhibit the phase separation between methyl ester and glycerol and contribute to emulsion formation during the aqueous rinse. With all this explains why the ester content, carbon residue and total glycerol present parameters out of specification. It is likely that the raw material should not have had a proper treatment for the transesterification reaction having a high content of FFA, with that, there was a decrease in the yield of the reaction, which may have been the reason for the ester content display a value specified below and the content of total glycerol be above specified. This above total content of glycerol may explain the residue carbon, as these fuels with high amounts of free glycerol present problems with deposition in

**CHARACTERISTICS UNIty LIMIT MÉTHOD BL BI-01 BI-02**

**Water Teor, max.** mg/kg 500 ASTM D 6304 347 405 276 **Flash Point, min.** °C 100 ASTM D 93 187,5 175,5 177,5 **Esther Teor, min.** % mass 96,5 EN 14103 96,6 91,0\*\* 97,4 **Carbon Residue** % mass 0,05 ASTM 4530 0,0004 0,057\*\* 0,01

**max.** °C <sup>19</sup> ASTM D 6371 -3,5 2,0 -4,0

**Free Glycerol, max.** % mass 0,02 ASTM D 6584 0 0,01 0,01 **Total Glycerol, max** % mass 0,25 ASTM D 6584 0,175 0,27\*\* 0,19

ASTM D 6584

**Methanol, max.** % mass 0,2 EN 14110 <0,01 0,01 0,01

take note

take note

**CKinematic Viscosity at 40°C** mm2

256 Biofuels - Status and Perspective

**Cold Filter Plugging Point,**

**Acid Value, max.** mg

**Mono, Di, Triacylglycerol** % mass

**Iodine Index** g/100g

**Table 1.** Biodiesel Samples Physical-chemistry Characteristics

**Oxidation Stability at 110 ° C, min.**

\*CIA – clear and impurities absent

\*\*Out range parameters

**Aspect** - \*CIA \*CIA \*CIA \*CIA **Density at 20 ºC** kg/m3 850-900 ASTM D 4052 881,6 880,3 881,7

/s 3,0-6,0 ASTM D 445 4,275 4,708 4,19

KOH/g 0,5 ASTM D 664 0,0081 0,2580 0,7391\*\*

Mono - 0,3855; Di - 0,3266; Tri - 0,2814

Hours 6 EN 14112 5,52\*\* 6,9 11,34

Mono – 0,75; Di – 0,46; Tri – 0,08

EN 14111 119,02 88,997 122,97

Mono – 0,68; Di – 0,06; Tri – 0,00

The International Confederation of Thermal Analysis and Calorimetry (ICTAC) defines thermal analysis as a group of techniques in which a physical property of a substance and / or its reaction products is measured as a function of temperature while the substance is subjected to a controlled program Temperature [27].

Thermal analysis provides information regarding: variation of density, thermal stability; and free water; bound water; purity, melting point, boiling point, heats of transition, specific heats, phase diagrams, reaction kinetics studies of catalysts, glass transitions, etc.

The advantages are many thermal analysis (requires little sample for tests, variety of results on a single graph), and its applicability occurs in several areas: food, catalysis, ceramics, civil engineering, pharmaceuticals, inorganic, organic, petrochemical, polymers, glass, among others. But there are some disadvantages in the use of thermal analysis such as the relatively high cost of equipment [28].

### **4.1. Thermogravimetry and Derivate Thermogravimetry (TG/DTG)**

Thermogravimetry or thermo gravimetric analysis is based on studying the variation in weight of a sample, resulting in a physical change (sublimation, evaporation, condensation) or chemical (degradation, decomposition, oxidation) versus time or temperature. It is a technique with wide application area in determining the thermal behavior of materials. The principle is based on obtaining the thermogravimetric curve (TG), by plotting mass (mg) or percentage of weight loss (y-axis) versus temperature or time (X axis). The sample container is wrapped and placed on an analytical balance in a controlled environment, where it performs the continuous and programmed heating. Upon degradation, the sample loses mass, in the form of volatiles and the sensor registers the corresponding mass loss [29-30]. The method allows to obtain the first derivative of the TG curve, called DTG curve, which allows you to view the start and end of each event of mass loss, indicating the temperature range where a particular decomposition reaction occurs.

Typically TGA curve and its derivative DTG curve are presented as in Figure 2:

**Figure 2.** TGA curve (dark-red) and its derivative, DTG (blue)

### **4.2. Differential Scanning Calorimetry (DSC)**

Differential Scanning Calorimetry (DSC) is defined as a technique which measures the temperatures and energy change associated with transitions in materials as a function of temperature or time.

DSC measures the difference in energy required for the substance and a reference material, thermally inert, while both are subjected to a controlled temperature variation so that the sample and reference are maintained under isothermal conditions, in relation the other, regardless the thermal event that is occurring in the sample.

The DSC curve provides qualitative and quantitative information about physical and chemical changes that involve endothermic processes (heat absorption), exothermic (releasing heat) or change in heat capacity [28].

There are two types of equipment that perform the Differential Scanning Calorimetry, the former is called a power compensation DSC and second DSC heat flow.

In power compensation DSC for the sample and the reference are placed in separate compart‐ ments of individual heat sources where the temperature and energy are monitored and generated by filaments of the same platinum, acting as resistive heaters and thermometers. This technique keeps constant the supplied heat. However, instead of measuring the difference in temperature between sample and reference during the reaction, a control system immedi‐ ately increases the power supplied to the sample when the process is endothermic and increases the energy supplied to the process when reference is exothermic, thus preserving the sample and reference at the same temperature.

The second type of instrument is called by DSC "heat flow". In the oven the crucibles are arranged on a base of a highly conductive metal, usually platinum. The sample and the reference are then heated by the same power supply system. Each time the sample reacts energy flow is established between the crucibles through the base of platinum. The data in the form of electric potential (microvolts) corresponding to the temperature increase of both crucibles inside the oven should increase linearly and symmetrically. Thus, a uV versus time curve can be computed.

The flow is then measured by means of temperature sensors placed in each crucible, thereby obtaining a proportional to the thermal capacity difference between the sample and the reference signal.

Typically DSC curve with glass transition, crystallization and fusion events, respectively, are presented as in Figure 3:

**Figure 3.** DSC curve with endothermic and exothermic events
