Castagnaro , T.S. 1 ; Carareto , N.D.D. 1 ; Costa, M.C. 1 ; Meirelles, A.J.A.

1. Solid-liquid phase diagrams of bynary mixtures formed by 1-octanol, 1-decanol, caprilic acid and capric acid Castagnaro, T.S.1; Carareto, N.D.D. 1; Costa, M.C. 1; Meirelles, A.J.A. ExTrAE, Faculdade de Engenharia de Alimentos, Universidade Estadual de Campinas (UNICAMP) * E-mail: tomze@fea.unicamp.br OBJECTIVES The study of phase equilibrium of lipid mixtures is an important research subject connected to the food industry, since many food products are based on fatty systems. Nowadays, little research has concentrated on the thermal behavior of fatty alcohols. The aim of this study was to measure and model the solid-liquid phase diagrams of the binary mixtures formed by the following saturated fatty alcohol pairs: 1-octanol + 1-decanol, 1-decanol + 1-dodecanol, 1-dodecanol + 1-hexadecanol and 1-tetradecanol + 1-octadecanol. The liquidus line of these systems was modelled using the Margules 3-Suffix and the NRTL equations. EXPERIMENTAL SECTION The samples were prepared gravimetrically (analytical balance -Adam AAA/L) with a ± 0.2 mg accuracy. The melting temperatures and the temperatures of solid-solid transition of pure fatty alcohols and their mixtures were determined by DSC, using a MDSC 2920, TA Instruments calorimeter under a heating rate of 1 K.min-1.The calorimeter was equipped with a cooling system, operated in the temperature range of 218 K to 348 K and using nitrogen as a purge gas. RESULTS AND DISCUSSION In thermograms some overlapped peaks are noted and are attributted to other thermal events that can not be identified using only DSC analysis. The phase diagrams of the studied systems exhibit two inflection points in the liquidus line related to the eutectic and peritectic reactions (Fig.1). The Tamman plot of the studied systems shows the existence of a solid solution region in the extreme of the phase diagram rich in the heaviest component (Fig.2). Fig. 1. Observed phase transitions of the system 1-dodecanol + 1-octadecanol. ● fusion temperature; + temperature of solid-liquid transition; ■ transition temperature under liquidus line; ●eutetic reaction temperature; ■ temperature of solid-solid transition; ♦ transition on the solid phase of the pure component. Fig. 2. Tamman plot for 1-dodecanol + 1-octadecanol system. ■ enthalpy of the eutectic reaction ● enthalpy of transition under liquidus line. CONCLUSION The DSC technique has proved to be an efficient and reliable method for studying fatty alcohol mixtures. The thermodynamic models Margules 3-suffix and NRTL allowed for a good fit of the experimental data. Acknowledgment