Modelagem termodinâmica do equilíbrio líquido-vapor de sistemas etanol + água + etilenoglicol para obtenção de etanol anidro

Abstract

This work is based on the study and thermodynamic modeling of the liquid-vapor equilibrium, formed by the ternary mixture of ethanol + water + ethyleneglycol, aiming to obtain ethanol in its anhydrous form. This mixture's study becomes important because the difficulties encountered in dehydrating ethanol due to the formation of an azeotrope between ethanol and water in compositions close to 95% by mass. In addition to its hydrated form, ethanol has a wide application of its anhydrous form, which must have a high degree of purity, being it 99% by mass. Some alternative processes to simple continuous distillation are applied to make it possible to acquire such purity, and among the most used processes are extractive and azeotropic distillation. Both have the addition of a third component to act as a solvent modifying the characteristics of the mixture and breaking the azeotropy, making it possible to obtain the anhydrous ethanol. In this work, the modeling of this system was performed from experimental data of binary and ternary pairs, in EXCEL® software with the aid of the thermodynamic supplement XSEOS© and computational tool Solver, present in the software, through the gamma-phi approach considering the vapor phase as ideal and, for the liquid phase, applying excess Gibbs energy models in the calculation of the activity coefficient, such as NRTL, Wilson, and UNIQUAC, allowing to obtain the binary interaction parameters for the species under study, to subsequently predicting the conditions of liquid – vapor equilibrium and study the influences of ethyleneglycol as a solvent. The realization of the modeling showed the solvents’ ability to separate the ethanol + water mixture, breaking the azeotrope to compositions greater than 0,1 molar.