LIQUAC Model Research Articles

Effect of salt-based deep eutectic solvent on vapor-liquid equilibrium for the mixture of 2-propanol and water

Salt-based deep eutectic solvents (DESs) (i.e, ethylene glycol-choline chloride-MgBr2 (1: 0.6: 0.05) and ethylene glycol-choline chloride-MgCl2 (1: 0.6: 0.05)) have been proposed in this work for the separation of the azeotrope of 2-propanol and water (H2O). Based on the newly determined experimental data for the systems (2-propanol + H2O + DESs), revised LIQUAC model was developed for describing the vapor-liquid phase equilibrium of the system (2-propanol + H2O + DESs). Comparisons of model calculated and experimental measured values proved that the model presented here provides a reliable method for correlating the vapor-liquid equilibria data. Furthermore, both the VLE experiments and the model were used to study the effect of salt-based deep eutectic solvent on vapor–liquid equilibria. It was revealed that ethylene glycol-choline chloride-MgCl2 (1: 0.6: 0.05) is more promising than ethylene glycol-choline chloride-MgBr2 (1: 0.6: 0.05) as entrainer for the separation of mixture (2-propanol + water).

A modified LIQUAC model for prediction of the vapor pressure of single liquid desiccant at high concentration and regeneration temperature

A comparative study is conducted to find that there are significant prediction deviations of single liquid desiccants vapor pressure at high concentration and regeneration temperature (high temperature) based on existing typical models. Some factors affecting water activity are not taken into account in these models, and they become more significant at high temperature and high concentration. This paper proposes a modified LIQUAC model to improve the prediction accuracy of single liquid desiccants vapor pressure at high temperature and high concentration. In the modified thermodynamic model, the middle-range interaction is derived by enhancing temperature and concentration dependence. By analyzing the prediction results of three typical liquid desiccants, it is found that the theoretical framework of the novel model is better than that of two typical models (using same data base for parameterization) at high temperature and high concentration. The interaction parameters in the modified model have precise physical meanings and make the model can be extended to other electrolyte solutions.

Salts Effect on Isobaric Vapor–Liquid Equilibrium for the Azeotropic Mixture 2-Propanol + Water

Vapor–liquid equilibrium (VLE) data for the systems 2-propanol + water + calcium chloride, 2-propanol + water + magnesium chloride, 2-propanol + water + calcium nitrate, and 2-propanol + water + magnesium nitrate were measured at the pressure of 101.3 kPa. Experimental data of all ternary systems passed the thermodynamic consistency test by modified McDermott–Ellis method. Then, the effects of salts on the vapor phase mole fraction of 2-propanol and the relative volatility of 2-propanol to water were analyzed. Results show that the azeotropic point of the system 2-propanol and water can be removed with addition of the salts, and the salting-out effects follow the order calcium nitrate > calcium chloride > magnesium nitrate > magnesium chloride. Furthermore, the LIQUAC model was adopted to correlate the VLE experimental data of the systems. The comparative results of the average relative deviation (Δz̅) and the corresponding standard deviations (σ) between the experimental and calculated values indicate that LIQUAC model is suitable for the VLE calculation for the systems of 2-propanol + water + salts.

A revised LIQUAC and LIFAC model (LIQUAC*/LIFAC*) for the prediction of properties of electrolyte containing solutions

The reliable knowledge of the thermodynamic behavior plays a major role for the design of different industrial processes. A lot of thermodynamic models do not incorporate electrolyte solutions. For these systems special models have been published. However a lot of these models suffer from the fact that highly concentrated electrolyte solutions cannot be calculated with the desired accuracy which leads to problems when calculating, e.g. salt solubilities. In this article, a revised LIQUAC and LIFAC model is presented, which enables the user to describe mean activity coefficients, osmotic coefficients and also vapor–liquid equilibria reliably. Furthermore the prediction of salt solubilities in aqueous solutions and mixed solvents can be performed successfully. In this paper the predicted data are compared with published data stored in the Dortmund Data Bank. The improvements achieved are additionally shown by a comparison with the results of the original LIQUAC and LIFAC model.

Thermodynamics of Phase Equilibria in Aqueous Strong Electrolyte Systems

The middle range (MR) parameters of the LIQUAC model were improved as a function of temperature to allow the calculation of the activities of all the species in the solution over a wide temperature...

The solid–liquid equilibrium of the binary system H 2O–DMSO and the influence of a salt (NaCl, KCl) on the thermodynamic behavior : Correlations using a revised LIQUAC model

The solid–liquid equilibrium of the binary system water (H 2O)–dimethyl sulfoxide (DMSO) is investigated and the results are compared to experimental values to ensure that the applied measurement procedure provides reliable results. After that, the freezing point depression of water is measured in the presence of different amounts of salt. Furthermore solubility measurements are carried out and compared to published experimental data to show that the apparatus used is also capable to provide reliable results for salt solubilities. Afterwards the ternary system is investigated using this measurement procedure to determine the solubilities of the salt in the mixed solvent system as well as the freezing point depression of the mixed solvents after the addition of salt. Two salts are investigated, sodium chloride (NaCl) and potassium chloride (KCl). Most of the measured ternary data seems to be reported for the first time. A correlation of the experimental results is also carried out using a revised version of the electrolyte model LIQUAC.

Generalized LIQUAC model for the single‐ and mixed‐solvent strong electrolyte systems

AbstractA generalized strong electrolyte LIQUAC model is presented to describe the vapor–liquid equilibria, osmotic coefficients, mean ion activity coefficients, and solid–liquid equilibria for the single‐ and mixed‐solvent electrolyte systems over the entire concentration range from infinite dilution to saturated solutions. An appropriate reference state for the ions was first applied to test the capability of the model in simultaneously describing the mean ion activity coefficients and the solubility of a salt in a binary solvent mixture. The influence of salt on the vapor–liquid equilibrium behavior is predicted with the new correlated parameters. The generalized activity coefficient formulations are presented through the investigation of thermodynamic properties and phase phenomena in the single‐ and mixed‐solvent electrolyte systems. This work is a continuous study for the LIQUAC activity coefficient model. A reliable representation of the single‐ and mixed‐solvent salt solutions is obtained. © 2010 American Institute of Chemical Engineers AIChE J, 2011

Solubilities of NaCl, KCl, LiCl, and LiBr in Methanol, Ethanol, Acetone, and Mixed Solvents and Correlation Using the LIQUAC Model

The solubilities of NaCl, KCl, LiCl, and LiBr in pure methanol, ethanol, and acetone were measured over a temperature range from 293.15 to 333.15 K. Furthermore salt solubilities in the mixed solvents (water + methanol, water + ethanol, water + acetone, methanol + ethanol, methanol + acetone, ethanol + acetone) were determined at 313.15 K. For a few systems solubility data are reported for the first time. In a few cases a comparison with published data stored in the Dortmund Data Bank (DDB)(1) showed disagreement. The LIQUAC model was used to correlate the experimental data. The calculated salt solubilities are in good agreement with the experimental results for the systems NaCl + water + methanol and KCl + water + methanol.

Prediction of solubilities of salts, osmotic coefficients and vapor–liquid equilibria for single and mixed solvent electrolyte systems using the LIQUAC model

The electrolyte model LIQUAC has been used up till now to predict osmotic coefficients, mean ion activity coefficients, the vapor–liquid equilibrium (VLE) behavior, the solubility of gases in single and mixed solvent electrolyte systems, and solubilities of salts in aqueous solutions. In this paper, the required expressions for the calculation of salt solubilities not only in aqueous systems, but also in organic solvents and water–solvent electrolyte systems were deduced in detail based on the LIQUAC model with a fixed reference state and thermodynamic relations. Four salts (NaCl, KCl, NH 4Cl and NaF) and two solvent (water and methanol) were selected to test the derived expressions. The results show that the LIQUAC model with a fixed reference state can be used to predict osmotic coefficients, solubilities of salts in aqueous solutions, vapor–liquid equilibria, and the solubilities of salts in water–organic solvent systems with strong electrolytes.

Modified LIQUAC and Modified LIFACA Further Development of Electrolyte Models for the Reliable Prediction of Phase Equilibria with Strong Electrolytes

The gE model LIQUAC and the corresponding group contribution model LIFAC are widely used for the reliable prediction of vapor−liquid equilibria (VLE), osmotic coefficients, and mean ionic activity coefficients for aqueous systems that contain strong electrolytes up to high concentrations. These models consist of a Debye−Hückel term, a Pitzer type virial equation for the middle-range contribution, and the UNIQUAC, respectively, the UNIFAC term. However, with the variable reference state proposed herein, a reliable prediction of liquid−liquid equilibria (LLE) using the LIQUAC or the LIFAC model is not possible. Because the mean ionic activity coefficient in all existing liquid phases must be predicted reliably, an explicit fixed reference state for the ions had to be introduced for the normalization of the middle-range term. The aim of this work is to modify the LIQUAC and LIFAC model for the prediction of ternary LLE using interaction parameters based on binary datasets. In addition, the results for binary properties could be improved by further changes of the original models. Using a comprehensive database, the interaction parameters for the modified LIQUAC and the modified LIFAC model had to be refitted and the obtained results for the calculated properties of binary and ternary mixtures were finally compared to the results of the original models.

Prediction of Solid-Liquid Equilibrium for KCl in Mixed Water-Ethanol Solutions Using the LIQUAC Model

The LIQUAC model is often used to predict vapor-liquid equilibria, osmotic coefficients, and mean ion activity coefficients for electrolyte systems. This paper describes a thermodynamic method to analyze solid-liquid equilibrium for electrolytes in mixed solvents solutions using the LIQUAC model. The KCl solubilities in mixed water-ethanol solutions are predicted with the LIQUAC model and its original interaction parameters. This method is also used to obtain new K +-ethanol interaction parameters in the LIQUAC model from the solubility data. The new interaction parameters accurately predict the vapor-liquid equilibrium data of K + salts (including KCl, KBr, and KCOOCH 3) in mixed water-ethanol solutions. The results illustrate the flexibility of the LIQUAC model which can predict not only vapor-liquid equilibrium but also solid-liquid equilibrium in mixed solvent systems.

GE Model for Single- and Mixed-Solvent Electrolyte Systems. 3. Prediction of Salt Solubilities in Aqueous Electrolyte Systems

The LIQUAC and LIFAC models have been widely used to predict osmotic coefficients, mean ion activity coefficients, the vapor−liquid equilibrium behavior, and the solubility of gases in single- and mixed-solvent electrolyte systems. In this paper, starting from the solubility product calculated using standard thermodynamic properties, the LIQUAC model is used to predict the solubilities of salts consisting of various cations (Na+, K+, and NH4+) and anions (F-, Cl-, Br-, I-, and SO42-) and their mixtures in aqueous solutions as a function of temperature.

Measurement and Correlation of Isothermal Vapor−Liquid Equilibrium Data for the System Ethanol + 2-Propanol + Barium Iodide

Isothermal vapor-liquid equilibrium data for the system ethanol + 2-propanol + barium iodide at three constant salt molalities (0.5, 1.0 and 1.5 mol.kg -1 ) have been measured with the help of headspace gas chromatography at 40.3, 55.3, and 70.6 °C. The experimental data were correlated using four electrolyte models: an electrolyte NRTL model, an extended UNIQUAC model, an electrolyte UNIFAC model, and the LIQUAC model.

Vapor–liquid equilibria of perfluorinated SPE/fuel system using group-contribution method

The LIQUAC model is extended to describe water activities of polymer electrolyte at the operating condition of polymer electrolyte fuel cell (PEFC). The proposed model includes the long-range interaction contribution caused by the Coulomb electrostatic forces, the middle-range interaction contribution from the indirect effects of the charge interactions and the short-range interaction contribution represented by the chain length dependence of a polymer. Theoretical predictions and experimental results are in good agreement.

Prediction of vapor–liquid equilibria in mixed-solvent electrolyte systems using the group contribution concept

The LIQUAC model is widely used to predict reliably vapor–liquid equilibria (VLE), osmotic coefficients and mean ion activity coefficients for electrolyte systems. It consists of a Debye–Hückel term, the UNIQUAC term and the osmotic virial equation for the middle-range contribution. The aim of this work is to provide a model based on the group contribution concept that can be used to predict phase equilibria in mixed-solvent electrolyte systems. Therefore, in the LIQUAC model the UNIQUAC equation has been substituted by the original UNIFAC equation and group interaction parameters have been introduced into the middle-range term. With the help of a large data base, 234 group interaction parameters for seven solvent groups, 13 cations and seven anions have been fitted. The model parameters have been used to calculate the VLE behavior, osmotic coefficients and mean ion activity coefficients for a large number of systems with high accuracy.

Measurement and Correlation of Isobaric Vapor−Liquid Equilibrium Data for the System Acetone + Methanol + Zinc Chloride

Isobaric vapor−liquid equilibrium data for the system acetone (1) + methanol (2) + zinc chloride (3) at constant salt molalities have been measured with the help of a modified Scott ebulliometer at 66.66 and 101.33 kPa. The measured data were correlated using the electrolyte UNIQUAC (Sander et al., 1986) and the LIQUAC (Li et al., 1994) model. A comparison of the correlations with the experimental data shows superior results for the LIQUAC model.

Measurement and Correlation of Isothermal Vapor−Liquid Equilibrium Data for the System Acetone + Methanol + Lithium Bromide

Isothermal vapor−liquid equilibrium data at three temperatures (39.5, 55.0, and 70.6) °C have been measured for the system acetone (1) + methanol (2) + lithium bromide (3) at constant salt molalities (0.500, 1.00, 2.00, 3.00 and 4.00 mol·kg-1) with the help of headspace gas chromatography. The experimental data were fitted using the electrolyte NRTL model (Mock et al., 1986), the extended UNIQUAC model (Sander et al., 1986), the electrolyte UNIFAC group-contribution model (Kikic et al., 1991) and the LIQUAC model (Li et al., 1994). The results of correlation were compared with the experimental data. Superior results were obtained for the LIQUAC model.

Isothermal Vapor−Liquid Equilibrium Data for the Acetone + Methanol + Lithium Nitrate System

Isothermal vapor−liquid equilibrium data at (39.5, 55.0, and 70.6) °C have been measured for the system acetone (1) + methanol (2) + lithium nitrate (3) at constant salt molalities (0.000, 0.500, 1.00, 2.000, and 3.000) with the help of headspace gas chromatography. The data were compared with the predicted results using the LIQUAC model.

Isothermal Vapor−Liquid Equilibrium Data for the Ethanol + Ethyl Acetate + Sodium Iodide System at Five Temperatures

Isothermal vapor−liquid equilibrium data at five temperatures (30.0, 40.3, 50.4, 61.2, and 70.2 °C) have been measured for the system ethanol + ethyl acetate + sodium iodide at constant salt molalities (0.000, 0.150, 0.300, 0.500, 0.700, 1.00, 1.50, 2.00 mol·kg-1) with the help of headspace gas chromatography. The data were compared with the predicted results using the LIQUAC model published by Li et al.