Advances in the Correlation of Thermodynamic Properties of Binary Systems Applied to Methanol Mixtures with Butyl Esters

Abstract

This work analyzes the utility of a new model to correlate thermodynamic properties of solutions, the foundations of which have been published in a previous study. The model is applied to a set of experimental data for several properties of binary systems of methanol with four butyl alkanoates (vapor-liquid equilibria at p ) 141.32 kPa and excess enthalpies and volumes at 298.15 and 318.15 K). Vapor-liquid equilibrium data (VLE) indicate that the four binary systems deviate positively from Raoult's law and do not present azeotrope. Excess enthalpies (h E ) are positive for the entire range of compositions and decrease regularly with increasing length of the ester chain, with (∂h E /∂T) p,x > 0. The excess volumes (V E ) decrease regularly with the length of the acid chain; they are positive for the binary systems of methanol with butyl (methanoate, ethanoate, and propanoate) and become negative for the system with butyl butanoate, with (∂V E /∂T) p,x > 0. The new model can be used to obtain a satisfactory correlation for Gibbs function g E ) g E (p, T, x i ), and for its derivatives. Correlation procedures for the data are described for the stages (x, h E ) f [x, g E (T)] for the isobaric data reported here and (x, V E ) f [x, g E (p)] for isothermal data reported in the literature. The new method allows a better correlation than the one obtained with the classical models of Wilson, NRTL, and UNIQUAC. We also present a unique correlation of all the properties of the methanol + butyl ethanoate system in the form of an analytical expression (p, T, x, y) ) 0 and conclude that, on the whole, its implementation can be considered an advance in the data treatment of the properties of liquid solutions.

Liquid–Liquid Equilibria in Binary Solutions Formed by [Pyridinium-Derived][F4B] Ionic Liquids and Alkanols: New Experimental Data and Validation of a Multiparametric Model for Correlating LLE Data

“…. The database generated was used together with data published previously 4À7 to achieve one of the objectives of this work, to treat and correlate them using two models: the NRTL model 8 and a parametric model proposed by the authors in previous works 9,10 (detailed in the following section). The graphs in Figures 1aÀe show the results for the set of compounds studied, with the distribution of experimental points obtained for each of the ILs.…”

“…Two correlation models were used for the Gibbs function: one previously employed by the authors to correlate vaporÀliquid equilibrium (VLE) data 9,10 and derived thermodynamic quantities, and an extended version of the local composition model (Non-Random Two Liquids, NRTL), for comparative purposes. A correlation method was applied (the same for both models) using a genetic algorithm (GA) 36 as a correlation tool and the appropriate objective functions for this procedure.…”

“…The characteristics of these global algorithms are similar to those of others constructed for the joint correlation of different thermodynamic properties, and some of their applications to other cases, which have been presented in previous works. 9,10 The detailed stages of this procedure are as follows: (1) Initial values are calculated for the model parameters obtained by optimizing an objective function (OF) γ , based on the isoactivity criterion and expressed as…”

“…In recent studies, 9,10 we have discussed the utility of a parametric model, of the type G E = G E (p, T, x), for the Gibbs excess function in multicomponent systems, of the form…”

“…8 However, because of the irregular distribution of the LLE data, there is some difficulty fitting the systems studied, and extended versions of the original model must be used to obtain acceptable correlations. Previous works 9,10 have presented the development and application of a polynomial model for Gibbs excess function G E = ψ{p, T, z(x)}, which gave good results for the correlation of vaporÀliquid equilibrium (VLE) data and other properties of solutions. This model will be Industrial & Engineering Chemistry Research ARTICLE used in this work for the first time to study its efficacy in the treatment of liquidÀliquid equilibrium (LLE) data, comparing the goodness of fit of the correlation obtained with that obtained via the NRTL model.…”