Isabel Vidal

LLE data for the systems water + (methanol or ethanol) + n-amyl acetate

We report new experimental liquid-liquid equilibrium data for the ternary mixtures water + methanol + n-amyl acetate and water + ethanol + n-amyl acetate at 25, 35 and 45 °C, together with the results of fitting the data with UNIQUAC equations. The activity coefficients of water and the alcohol in water + (methanol or ethanol) mixtures were calculated using UNIQUAC parameters obtained from experimental data for each of a number of ternary mixtures including water and the alcohol in question.

Optimization of UNIQUAC structural parameters for individual mixtures; application to new experimental liquid-liquid equilibrium data for aqueous solutions of methanol and ethanol with isoamyl acetate

Abstract Arce, A., Blanco, A., Martinez-Ageitos, J. and Vidai, I., 1994. Optimization of UNIQUAC structural parameters for individual mixtures; application to new experimental liquid-liquid equilibrium data for aqueous solutions of methanol and ethanol with isoamyl acetate. Fluid Phase Equilibria 93; 285-295. Experimental liquid-liquid equilibrium data for the ternary mixtures water + methanol + isoamyl acetate and water + ethanol + isoamyl acetate at various temperatures are reported, together with the results of correlation by the original UNIQUAC equation using both structural parameters q and r from the literature and qs and rs optimized for each mixture as part of the overall correlation procedure. The improved fit obtained with the optimized parameters (which differed from the “universal” values only for the smaller molecules) may be viewed as being due to the active surface area and volume of a molecule being dependent upon its environment.

Phase equilibria of water + methanol + hexyl acetate mixtures

Abstract Liquid-liquid equilibrium data at 25, 35 and 45 °C, and isobaric vapour-liquid equilibrium data at 101.32 kPa, were determined for the ternary system water + methanol + hexyl acetate. The data were correlated using the Wilson, NRTL and UNIQUAC models and were predicted using the UNIFAC and ASOG methods.

Excess volumes and refractions and liquid-liquid equilibria of the ternary system water + ethanol + hexyl acetate

Abstract Arce, A., Blanco, A., Soto, A., Souza, P. and Vidal, I., 1993. Excess volumes and refractions and liquid-liquid equilibria of the ternary system water + ethanol + hexyl acetate. Fluid Phase Equilibria , 87: 347-364. Densities, refractive indices, excess molar volumes and excess molar refractions at 25°C, and liquid-liquid equilibrium (LLE) data at 25, 35 and 45°C, are reported for the system water + ethanol + hexyl acetate. NRTL and UNIQUAC equations have been fitted to the experimental data, and the sensitivity of the correlation to changes in the composition of the phases in equilibrium has been analysed. The validity of the parameters obtained from the ternary system data for representation of the binary systems was also assessed.

Analysis of the relationship between ternary mixtures and their binary sub-systems as represented by the uniquac and nrtl models

Abstract The second derivative of the Gibbs free energy of mixing, G11, was calculated for the binary mixtures water + alcohol and solvent + alcohol (alcohol is methanol or ethanol, solvent is n-amyl acetate, iso-amyl acetate, hexyl acetate or 1-octanol) using, for G, binary uniquac and nrtl equations with interaction parameters obtained by fitting the corresponding ternary equations to liquid-liquid equilibrium data for the ternary systems water + alcohol + solvent. Apart from the usual result that the binary interaction parameters of the uniquac and nrtl equations, and the corresponding thermodynamic descriptions of binaries in terms of G11, depend heavily on the system from which they have been obtained (which should be borne in mind when using the binary parameters in calculations for multicomponent systems), the chief conclusion of this work is that the uniquac and nrtl models do not imply any consistent relationship between the slopes of the ternary tie-lines and the characteristics of the G11 of the corresponding homogeneous binary mixtures.