Vapor-Liquid Equilibrium Modeling of Ethanol/Water/Glyceline Systems

This work aims to correlate vapor-liquid equilibrium (VLE) data involving ethanol, water and glyceline, in order to design and simulate an alternative extractive distillation (ED) process to produce anhydrous ethanol. In the Aspen Plus v12 software, the deep eutectic solvent (DES), composed of a binary mixture of choline chloride:glycerol (glyceline) with a molar ratio of 1:2, was represented as a pseudo-component. Temperature-dependent thermophysical properties data, including vapor pressure, viscosity, molar volume, and heat capacity, were collected from literature and regressed using appropriate models programmed in python, yielding high coefficients of determination (R² > 0.99) and relative deviations below 10%. From experimental VLE data available in the literature at different pressures (101.3 and 11.3 kPa) for binary, pseudobinary and pseudoternary systems involving ethanol, water and glyceline, a thermodynamic modeling was proposed based on the Non-Random Two-Liquid (NRTL). In this case, the TMV-VLE software was adopted to obtain the binary interaction parameters of the NRTL model, following the Barker’s modified method. Experimental and calculated data for the VLE systems were compared through the average absolute deviation (AAD). Two different parameter sets were obtained, in order to better describe VLE data at 101.3 kPa and 11.3 kPa, since these pressures are suitable for the purification and recovery columns, respectively, of an alternative ED process. Excellent agreement was obtained between experimental data and calculated results by NRTL, taking into account the suitable representation of the VLE diagrams and low values of AAD. The use of distinct parameter sets for different pressures proved essential to improve the accuracy of the phase equilibrium modeling, assuring more safety in the design and simulation steps involved to develop an alternative ED process from DES.