Estudo de validação termodinâmica do equilíbrio líquido vapor (ELV) para sistema etanol-água usando Software LIVRE COCO

Abstract

Obtaining the resulting ethanol from fermentable processes generates a final product with the formation of a binary mixture between ethanol-water, considered a non-ideal mixture for presenting a minimum temperature azeotrope in the molar fraction of 89%. The equilibrium curve is presented in the literature as an equilibrium point and its adjustment by mathematical models is a very important step for the evaluation of its thermodynamic properties present in the mixture. In this case, the identification of the activity coefficients of ethanol and water is very important in the adjustment of the equilibrium data. Wilson, NRTL, Van Laar and Margules equations are among the most used empirical models to identify these activity coefficients. In this work, the FREE COCO Software was used to compare the Wilson, NRTL, Van Laar and Margules thermodynamic models in order to identify the best model that fits the experimental data of T-x-y equilibrium of the ethanol-water mixture at a pressure of 1 atm. In this study, Microsoft Excel and the XSEOS plugin in Excel were also used to calculate the properties of the liquid phase. In the COCO software simulations, the models that best fit the experimental data were Wilson and NRTL. The Van Laar model showed a failure in the adjustment when working with low compositions and the Margules model cannot explain the behavior of the experimental data. The binary interaction coefficients obtained from the Margules and Van Laar models showed a similarity with the data obtained in the literature. The binary interaction parameters of the Wilson and NRTL model were not obtained, although an equation for three parameters was found. Still, all tested thermodynamic models have similar behaviors regarding excess Gibbs energy and activity coefficient calculations.