LLE of ternary mixtures of water/acetone/2-ethyl-1-hexanol at different temperatures

Experimental liquid–liquid equilibrium (LLE) data were determined for a ternary system water+acetone+2-ethyl-1-hexanol at various temperatures of 298.2, 303.2, 308.2, and 313.2 K and atmospheric pressure. The UNIQUAC model was used to correlate the experimental tie-line data. The LLE data were correlated fairly well with this solution model, indicating the reliability of the UNIQUAC equation for this ternary system. The average root mean square deviation between the observed and calculated mole fractions was 1.87%. The mutual solubility of 2-ethyl-1-hexanol and water was also investigated by the addition of acetone at different temperatures.     

Liquid phase equilibria of (water + propionic acid + oleyl alcohol) ternary system at several temperatures

(Liquid–liquid) equilibrium (LLE) data are investigated for mixtures of (water + propionic acid + oleyl alcohol) at 298.15, 308.15 and 318.15 K and atmospheric pressure. The solubility curves and the tie-line end compositions of liquid phases at equilibrium were determined, and the tie-line results were compared with the data predicted by the UNIFAC method. The phase diagrams for the ternary mixtures including both the experimental and correlated tie-lines are presented. The distribution coefficients and the selectivity factors for the immiscibility region are calculated to evaluate the effect of temperature change. The reliability of the experimental tie-lines was confirmed by using Othmer–Tobias correlation. It is concluded that oleyl alcohol may serve as an adequate solvent to extract propionic acid from its dilute aqueous solutions. The UNIFAC model correlates the LLE data for 298.15, 308.15 and 318.15 K with a root mean square deviation of 5.89, 6.46, and 6.69%, respectively, between the observed and calculated mole concentrations.     

Liquid-liquid equilibrium in ternary ionic liquid systems by UNIFAC: New volume, surface area and interaction parameters. Part II

Ionic liquids are potential solvents for liquid extraction processes; thermodynamic modeling of liquid-liquid equilibrium (LLE) data is essential for the optimization and operation of these processes. Therefore, ternary LLE data in systems involving ionic liquids have been investigated by several years. In most of the cases, the thermodynamic modeling of these systems has been made using the NRTL model; in some cases, the UNIQUAC model has also been used. The structural parameters of UNIQUAC for ionic liquids have been determined either by empirical correlations or, more recently, through quantum mechanics calculation. This work is a continuation of a recent paper, in which the structural group volume and area parameters for the group-contribution UNIFAC method have been calculated for five ionic liquids following the quantum mechanics approach. In order to optimize the molecular geometry and to calculate the area and volume, the Density Functional Theory (DFT) and the Polarizable Continuum Method (PCM) were used, respectively. The obtained parameters were used to correlate LLE data for fifteen ternary systems, totalizing 155 tie-lines. New interaction parameters were also estimated between the solvent and the ionic liquid functional groups. The results are very satisfactory, with root mean square deviations 0.0037 between experimental and calculated equilibrium mole fractions.     

Calculation for liquid-liquid equilibria of quaternary alkane-ethyl acetate-methanol-water systems used in counter-current chromatography

The calculation of liquid-liquid equilibrium compositions of solvent systems is very important for the work on counter-current chromatography (CCC), especially the phase composition and volume ratio obtained from liquid-liquid equilibrium calculation. In this work, liquid-liquid equilibria of quaternary Arizona solvent systems, alkane-ethyl acetate-methanol-water, and related ternary systems are correlated and predicted using the non-random two-liquid model (NRTL). Hexane, heptane and isooctane are the used alkanes. The parameters in the model are regressed only with the special systems considered. Detailed comparison with experimental data shows that liquid-liquid equilibria of these systems can be predicted with greatly improved accuracy as compared to the group contribution method (UNIFAC).     

Quaternary Liquid–Liquid Equilibria for Aqueous Systems Containing Dimethyl Carbonate at 298.15 K

Experimental tie-line data for two ternary systems, water + dimethyl carbonate + methanol or ethanol, and two quaternary systems, water + dimethyl carbonate + toluene + methanol or ethanol were investigated at 298.15 K and atmospheric pressure. The experimental liquid–liquid equilibrium data were correlated using a modified UNIQUAC activity coefficient model with binary and ternary as well as quaternary parameters. The calculated results were further compared with those obtained from an extended UNIQUAC model.     

Measurement and correlation of liquid–liquid equilibria for water + ethanol + mixed solvents (dichloromethane or chloroform + diethyl ether) at T = 293.15 K

Liquid–liquid equilibrium (LLE) data for the quaternary systems (water + ethanol + dichloromethane (DCM) or chloroform (CHCl₃) + diethyl ether (DEE)) were experimentally investigated at 293.15 K. The thermodynamic consistency of the data was performed using the Othmer–Tobias and Hand plots. The experimental tie-line data were correlated using the non-random, two-liquid (NRTL) model. As a result, the comparison of the extracting capabilities of the mixed solvents with respect to the distribution coefficients and separation factors showed that the (50% DCM +50% DEE) system had a higher separation factor for the (water + ethanol + DCM + DEE) system. On the other hand, the (50% CHCl₃ +50% DEE) system had a higher separation factor for the (water + ethanol + CHCl₃ + DEE) system. The last solvent (50% CHCl₃ +50% DEE) was found to be the best solvent, with a positive synergistic effect on DEE, high separation factor, and very low solubility in water.     

Ternary liquid–liquid equilibria for mixtures of (ethanol + toluene + n -decane)

The data on the liquid–liquid equilibrium in (ethanol?+?toluene?+?n-decane) have been measured at three temperatures 298.15, 303.15 and 313.15?K and ambient pressure. Gas liquid chromatography has been employed, to determine the composition of the substances in liquid phases. The measured tie-line data are presented. The experimental ternary liquid–liquid equilibrium data have been correlated, using the universal quasi chemical (UNIQUAC) and non-random tow-liquid (NRTL) activity coefficient models to obtain the binary interaction parameters of these components. Both the UNIQUAC and NRTL models, satisfactorily predict the equilibrium compositions. The partition coefficients and the selectivity factor of the toluene extraction from n-decane mixtures were calculated and presented.     

Phase equilibria for liquid mixtures of (butanenitrile + a carboxylic acid + water) at 298.15 K

Liquid–liquid equilibrium data are presented for mixtures of (butanenitrile (1)+acetic acid or propanoic acid or butanoic acid or 2-methylpropanoic acid or pentanoic acid or 3-methylbutanoic acid (2)+water (3)) at 298.15 K. The relative mutual solubility of all the carboxylic acids is higher in the butanenitrile layer than in the aqueous layer. The influence of acetic acid and propanoic acid on the solubility of water in butanenitrile is greater than that of the other acids. Three parameter equations have been fitted to the binodal curve data. These equations are compared and discussed in terms of statistical consistency. Selectivity values for solvent separation efficiency were derived from the tie-line data. The NRTL and UNIQUAC models were used to correlate the experimental results and to calculate the phase compositions of the ternary systems. The NRTL equation fitted the experimental data far better than the UNIQUAC equation.     

LLE for the extraction of alcohol from aqueous solutions with diethyl ether and dichloromethane at 293.15 K, parameter estimation using a hybrid genetic based approach

Experimental liquid-liquid equilibrium (LLE) data for the extraction of methanol, ethanol and 1-propanol from water by diethyl ether and dichloromethane at 293.15 K and at ambient pressure were investigated. Data for the binodal curves have been determined by cloud-point titration method and conjugate points on tie-line were obtained by correlating the refractive index of the binodal curves as a function of composition. The experimental ternary (liquid + liquid) equilibrium data have been estimated using the NRTL and UNIQUAC activity coefficient models to obtain the binary interaction parameters of these components by a combination of Levenberg-Marquardt method and the genetic algorithm based method. The distribution coefficients and the selectivity factor of the solvent used were calculated and presented. From our experimental and calculated results, we conclude that for the extraction of alcohol from aqueous solutions with dichloromethane solvent has a higher selectivity factor than the diethyl ether solvent.     

Liquid–liquid equilibrium of ternary systems 1-octyl-3-methylimidazolium hexafluorophosphate + aromatic + aliphatic hydrocarbons

The phase behavior of six ternary systems involving an aromatic hydrocarbon (benzene, toluene or m-xylene), an aliphatic hydrocarbon (nonane or undecane), and an ionic liquid (1-octyl-3-methylimidazolium hexafluorophosphate, [omim][PF₆]) was experimentally studied at 298.15 K and atmospheric pressure, totalizing 26 tie-lines. The main goal is to determine if [omim][PF₆] is a good solvent for the separation of the aromatic and aliphatic compounds, a common operation in the processing of reformed naphtha. All the ternary diagrams are of type 1, with high and wide two-phase regions, which show that [omim][PF₆] is a good solvent for the extraction of aromatic from aliphatic hydrocarbons. The Othmer–Tobias correlation was used for evaluation of the quality of the tie-line data, with good results. The data were correlated with the NRTL model for the activity coefficient, with estimation of new interaction energy parameters by using a modified Simplex method and a composition-based objective function. The results, expressed by root mean square deviations between experimental and calculated compositions, are very satisfactory.     

Fluid phase topology of ethanol+benzene+cyclohexane at 101.3 kPa

In this article, isobaric vapor–liquid equilibria for the ternary mixture of ethanol?+?benzene?+?cyclohexane was experimentally investigated at atmospheric pressure. Vapor–liquid equilibria data for ethanol?+?benzene?+?cyclohexane at 101.3?kPa were obtained with a Othmer-type ebulliometer. Data were tested and considered thermodynamically consistent. The experimental results showed that this ternary mixture is completely miscible and exhibits three binary homogeneous azeotropes and a ternary minimum azeotrope at the studied conditions. Satisfactory results were obtained for correlation of equilibrium compositions with UNIQUAC activity coefficients model and also for prediction with UNIFAC method. In both cases, low root mean square deviations of vapor mole fraction and temperature were calculated. The capability of ethanol as modified distillation agent at atmospheric condition is discussed in terms of the thermodynamic topological analysis. However, owing to the complex topology of the ternary mixture it leads to a distillation scheme with three columns and difficult operation and thus, ethanol is not recommended as a separating agent for benzene?+?cyclohexane azeotrope.     

Isothermal vapor–liquid equilibria for mixtures composed of 1,2-dimethoxybenzene, 2-methoxyphenol,and diphenylmethane

Diphenylmethane was found to be a potential entrainer for separating the closely boiling mixtures of 2-methoxyphenol+1,2-dimethoxybenzene via extractive distillation. To gain insight into the capability of this auxiliary agent, isothermal vapor–liquid equilibrium data were measured for the binary and the ternary mixtures containing 2-methoxyphenol, 1,2-dimethoxybenzene, and diphenylmethane at temperatures from 433.15 to 463.15 K. All the binary data passed thermodynamic consistency tests. However, there exhibits a large discrepancy between the experimental values and the predicted results from the UNIFAC model. The new data were correlated with the Wilson, the NRTL, and the UNIQUAC models, respectively. The model parameters determined from the binary data were applied to predict the phase equilibrium behavior of the ternary system.     

Liquid–Liquid Equilibria of Oxygenate Fuel Additives with Water at 298.15 K: Ternary and Quaternary Aqueous Systems of Diisopropyl Ether and Hydrocarbons with 2-Propanol

Experimental tie-line data were determined for one ternary system, water + diisopropyl ether + n-heptane and two quaternary systems, water + diisopropyl ether + 2-propanol + n-heptane or toluene at 298.15 K and ambient pressure. The experimental liquid–liquid equilibrium data were successfully correlated using a modified UNIQUAC model with ternary and quaternary mixture parameters, in addition to the binary ones. The calculated results were also compared with those obtained from an extended UNIQUAC model of Nagata [Fluid Phase Equilib. 54, 191 (1990)].     

Improved binary parameters using GA for multi-component aromatic extraction: NRTL model without and with closure equations

Application of genetic algorithm (GA), which leads to globally optimal binary interaction parameters from multi-component liquid–liquid equilibrium data, has been recently demonstrated for some ternary, quaternary and quinary systems. The binary interaction parameters are related to each other through the closure equations. In this work, the binary interaction parameters based on non-random two liquid (NRTL) activity coefficient model have been estimated using GA, without and with closure equations for 65 multi-component aromatic extraction systems: 53 ternary, 9 quaternary and 3 quinary systems. Parameters that satisfy the closure equations exhibit better root mean square deviations than those that do not satisfy the closure equations. Root mean square deviation value without implementation of closure equations is 0–80% better than literature as compared to 0–90% better with implementation of closure equations.     

Azeotropic behaviour of (benzene + cyclohexane + chlorobenzene) ternary mixture using chlorobenzene as entrainer at 101.3 kPa

In this paper, the azeotropic behaviour of the (benzene + cyclohexane + chlorobenzene) ternary mixture was experimentally investigated with the aim of enhancing the knowledge for the feasible use of chlorobenzene as an entrainer for the azeotropic distillation of the binary azeotrope. Such a study has not been reported in the literature to the best of the authors’ knowledge. (Vapour + liquid) equilibria data for (benzene + cyclohexane + chlorobenzene) at 101.3 kPa were obtained with a Othmer-type ebulliometer. Data were tested and considered thermodynamically consistent. The experimental results showed that this ternary mixture is completely miscible and exhibits an unique binary homogeneous azeotrope, an unstable node at the conditions studied, and the propitious topological characteristics (residual curve map and relative volatility) to be separated. Satisfactory results were obtained for the correlation of equilibrium compositions with the UNIQUAC activity coefficients model and also for prediction with the UNIFAC method. In both cases, low root mean square deviations of the vapour mole fraction and temperature were calculated. The capability of chlorobenzene as a modified distillation agent at atmospheric condition is discussed in terms of the thermodynamic topological analysis. A conceptual distillation scheme with reversed volatility is proposed to separate the azeotropic mixture. In order to reduce the operational cost requirements of the sequence of columns proposed, the range for optimal reflux and the ratio for feed flow conditions were studied.     

Isobaric vapor–liquid equilibria for 1-propanol + water + lithium chloride at 100 kPa

Isobaric vapor–liquid equilibria for the ternary system 1-propanol+water+lithium chloride has been measured at 100 kPa using a recirculating still. The addition of lithium chloride to the solvent mixture produced an important salting-out effect over the alcohol and the azeotrope tended to be eliminated when the salt content increased, and two immiscible liquid phases were observed in a broad range of salt concentration. The experimental data sets were fitted with the electrolyte NRTL model and the parameters of Mock et al.’s model were estimated. This model has proved to be suitable to represent experimental data in the entire range of compositions. The effect of lithium chloride on the vapor–liquid equilibrium of the propanol+water system has been compared with that produced by other salts.     

Liquid–liquid equilibrium for the system water + acetic acid + 1-heptanol at 278.1, 293.1, 303.1 and 313.1 K

Liquid–liquid equilibrium (LLE) for the system water+acetic acid+1-heptanol have been studied at atmospheric pressure in the temperature range of 278.1–313.1 K. The raw experimental data of this work, together with the available experimental data in the literature on the same ternary system, are analyzed and compared. The analysis is achieved by using three versions of the well-known UNIFAC model. The comparison is made in terms of root-mean-square (RMS) in temperature and composition, maximum deviation (MAXDEV) in temperature, and the average-absolute deviations (AAD) in compositions. In all of these models, the interaction parameters employed are those provided by Aspen Plus library. All models predict much lower deviations and RMS values for the data of this study than those for the data of the literature.     

Measurement and prediction of tie-line data for mixtures of (water + 1-propanol + diisopropyl ether): LLE diagrams as a function of temperature

Tie-line data for ternary system of (water + 1-propanol + diisopropyl ether (DIPE)) were determined at T = (298.2, 308.2 and 313.2) K under atmospheric conditions. The ternary system exhibited type-I LLE behavior, as (DIPE + water) is the only liquid pair that is partially miscible. The experimental data for this system were predicted with the UNIFAC model with a root mean square deviation of 2.64%. The reliability of the experimental tie-line data was determined through the Othmer–Tobias and Hand plots. Distribution coefficients and separation factors were measured to evaluate the extracting capability of the solvents. The influence of temperature effect on the equilibrium characteristics and separation factor was found to be significant at the temperatures studied.     

Phase equilibria of (water + levulinic acid + dibasic esters) ternary systems

Liquid–liquid equilibrium (LLE) data of the solubility (binodal) curves and tie-line end compositions were examined for mixtures of {(water (1) + levulinic acid (2) + dimethyl succinate or dimethyl glutarate or dimethyl adipate (3)} at 298.15 K and 101.3 ± 0.7 kPa. The reliability of the experimental tie-line data was confirmed by using the Othmer–Tobias correlation. The LLE data of the ternary systems were predicted by UNIFAC method. The LLE data were correlated fairly well with UNIQUAC and NRTL models, indicating the reliability of the UNIQUAC and NRTL equations for these ternary systems. The best results were achieved with the NRTL equation, using non-randomness parameter (α = 0.3) for the correlation. Distribution coefficients and separation factors were measured to evaluate the extracting capability of the solvents.