1. Laboratório de EXtração, TeRmodinâmica Aplicada e Equilíbrio Matricarde Falleiro, R. M. 1, Meirelles, A. J. A. 2, Krähenbühl, M. A. 1, * 1 Laboratory of Thermodynamic Properties, LPT, School of Chemical Engineering, University of Campinas, Brazil 2 Laboratory of Extraction, Applied Thermodynamics and Equilibrium, ExTrAE, School of Food Engineering, University of Campinas, Brazil * Corresponding author e-mail: mak@feq.unicamp.br OBJECTIVES Vapor-liquid equilibrium (VLE) data of mixtures involving fatty acids and ethyl esters are practically nonexistent in literature. The great importance of such data for the biodiesel industry is related to the quality of the biofuel. Generally, it quality can be influenced by several factors, such as presence of Free Fatty Acids (FFA). These, depending of concentration, inhibit phase separation of ethyl esters and glycerol, which compromises the quality standards of biodiesel. Therefore, the present work aims to determine VLE data for fatty mixtures of acids and esters by Differential Scanning Calorimetry (DSC). METHODOLOGY Lauric acid, myristic acid, ethyl myristate and ethyl palmitate with purity greater than 99% were acquired from Sigma, and oleic acid, with 99% purity, was acquired from Fluka. The experimental apparatus (Figure 1-a) consists of a DSC (Model 2920) with a vacuum system fitted to it. For the DSC analysis, binary mixtures of ethyl myristate + myristic acid; lauric acid + ethyl palmitate and ethyl palmitate + oleic acid was evaluated at 2.67 kPa, covering throughout the phase diagram (x 1 = 0, 0.1, 0.2... to 1.0). Samples of 4 to 8 mg were used in the study, with a heating rate of 25 °C.min −1 and a small ball placed over the pinhole (Figure 1-c), in order to avoid the pre-vaporization of the sample, since it behaves as an exhaust valve, releasing the vapor phase in a controlled manner. RESULTS AND DISCUSSION For each one of samples analyzed (Figure 2, 3 and 4), it was determined the boiling temperature through of the temperature onset measure as showed in figure 1-d. The data were modelated using the NRTL and UNIQUAC Equations (Table 1). Both models were able to describe the experimental data with low deviations. CONCLUSION The results obtained have shown that the applied method is an accuracy experimental technique that uses a shorter operation time and small amount of sample. This study also improved the thermodynamic modeling by determining the binary interaction parameters of models used to describe non-ideality of the liquid phase needed for the development of equipment for fuel production (biodiesel) Figure 1 – (a) General view of experimental apparatus room; (b) Expanded perspective of the DSC furnace; (c) Tungsten ball being placed on the pinhole; (d) Perspective in more details of some accessories under of the bench; (e) Differential thermal curve obtained by DSC (b) (c) (a) (d) onset temperature baseline boiling endotherm (e) x 1 ≈ 0.1 x 1 ≈ 0.3 x 1 ≈ 0.5 x 1 ≈ 0.7 x 1 ≈ 0.9 Sistemasg E Model A 12 / cal.mol -1 A 21 / cal.mol -1  12 * Mean Deviation / ºC Ethyl Myristate + Myristic Acid NRTL1529.5500-782.99400.29870.14 UNIQUAC637.3379-447.0392-0.14 Lauric Acid + Ethyl Palmitate NRTL-865.82601339.64470.31810.17 UNIQUAC-341.7366437.2044-0.18 Ethyl Palmitate + Oleic Acid NRTL844.9378-927.54030.30540.38 UNIQUAC283.2647-275.0970-0.38 Table 1 – Binary interaction parameters of NRTL and UNIQUAC models. Figure 2 – (a) Boiling endotherms to system: ethyl myristate (1) + myristic acid (2) obtained by DSC; (b) liquid-vapor equilibria: ethyl myristate (1) + myristic acid (2) at 2.67 kPa. Figure 3 – (a) Boiling endotherms to system: lauric acid (1) + ethyl palmitate (2) obtained by DSC; (b) liquid-vapor equilibria: lauric acid (1) + ethyl palmitate (2) at 2.67 kPa. Figure 4 – (a) Boiling endotherms to system: ethyl palmitate (1) + oleic acid (2) obtained by DSC; (b) liquid-vapor equilibria: ethyl palmitate (1) + oleic acid (2) at 2.67 kPa. (a) (b)