Nonrandom Two-liquid Research Articles

Computational study of the acetic acid extraction process from an aqueous solution with the aid of biological buffer

The liquid-liquid extraction of acetic acid from an aqueous solution with 1-heptanol as an extraction solvent in the extraction column and mixer-decanter at 30°C and atmospheric pressure was simulated using Aspen Plus. A Non-Random Two-Liquid (NRTL) based model was developed by minimizing maximum-likelihood objective function. In the simulation of the extraction column and mixer-decanter, the effect of the number of stages and the flow rate of the solvent on the percent recovery can be seen. In addition, a comparison of the percent recovery value between acetic acid extraction systems using EPPS (4-(2-hydroxyehtyl)-1-piperazine propanesulfonic acid) and HEPES (4-(2-hydroxyethyl)-1 piperazineethanesulfonic acid) buffers was also carried out with systems without buffers. In this study, an economic analysis was also carried out for the acetic acid extraction system using an extraction column and a mixer-decanter. Based on the simulation results, the acetic acid extraction system with the addition of HEPES buffer using extraction column with the number of stages = 8 and solvent to feed mass ratio = 1.6 was the most optimal and efficient extraction process obtained in this study. This system has the capital cost of 180,729,262.67 USD with the percent recovery up to 99.83% and the mass fraction of acetic acid in the raffinate phase is 0.0002 which is also extremely low.

Phase equilibrium for the binary mixture of 1,1,2,3,3,3-hexafluoro-1-propene (R1216) + propane (R290) at temperatures from 283.15 to 313.15 K

Based on the study of the mixture containing 1,1,2,3,3,3-hexafluoro-1-propene (R1216) and propane (R290) by a set of static-analytical type experimental apparatus, this paper presents a series of vapour-liquid equilibrium data at the temperature from 283.15 K to 313.15 K. It is the first time to report the VLE data at a temperature below 313.15 K. Moreover, the uncertainties of pressure, temperature, and mole fraction in this experiment were determinate. The PR equation of state (EoS) combined with the following two models respectively, the van der Waals (vdWs) mixing rule and the Huron-Vidal (HV) mixing rule relating to the non-random two-liquid (NRTL) activity coefficient model were used to correlate the experimental VLE data of the binary system. Two models all presented an extremely content correlation of the experimental data for the R290 + R1216 mixtures, and the second model is more suitable as the pressure's maximum average relative and absolute deviation are 0.003 and 0.0026, respectively, and the maximum average absolute deviation of the vapor phase mole fraction AAD(y) is 0.0045. Near azeotropic phenomenon occurred within the temperature range of the experiment when the proportion of R290 is about 0.6 to 0.7.

Experimental investigation on the phase behavior of DME/ [P6,6,6,14][Cl] and thermodynamic analysis for absorption refrigeration system

Dimethyl ether (DME), as an environmental-friendly alternative refrigerant, has received broadly attention. Phosphonium-based ionic liquids with good thermophysical properties are regarded as promising absorbents in absorption refrigeration systems. In this work, the measurement of solubility behavior to DME in trihexyltetradecylphosphonium chloride ([P6,6,6,14][Cl]) was carried out from 278.15 K to 348.15 K by means of isochoric saturation method. Non-random two liquid (NRTL) model and Krichevsky-Kasarnovsky (K-K) model were used to correlate the experimental data. The absolute average relative deviation between experimental liquid mole fraction and calculated values was 0.739% and 1.517% for NRTL model and K-K model respectively. Based on the solubility results, the performance of single-effect absorption refrigeration cycle used DME/[P6,6,6,14][Cl] pairs was analyzed, and further compared with other working pairs composed of [P6,6,6,14][Cl].

Solubility Measurement and Thermodynamic Correlation of Diacetone Acrylamide in 15 Pure Solvents from 272.05 to 323.65 K

For the design, optimization, and control of the solution crystallization process of diacetone acrylamide (DAAM), solid–liquid equilibrium data in various solvents are critical. In this work, the solubility of DAAM in 15 pure solvents, such as methanol, ethanol, n-propanol, isopropanol, n-butanol, 1-hexanol, isobutanol, n-pentanol, isopentanol, 2-butanone, acetone, ethyl acetate, 2-pentanone, acetonitrile, methyl acetate, and ethyl formate, is analyzed by a gravimetric method under ambient pressure and temperatures ranging from 272.05 to 323.65 K. The solubility values in all of the solvents are positively correlated with temperature. The solubility of DAAM can be satisfactorily correlated by the Apelblat equation, λh equation, nonrandom two-liquid (NRTL) model, and Wilson model, and the calculated solubility agrees well with the measured results. The obtained maximum relative average deviation (RAD) and root-mean-square deviation (RMSD) are 2.44 × 10–2 (n-propanol, NRTL model) and 2.40 × 10–2 (methanol, λh equation), respectively. The most suitable model is the Apelblat equation.

Solubility behavior of 3, 3, 3-trifluoropropene in 1-hexyl-3-methyl-Imidazolium hexafluorophosphate and 1-octyl-3-methyl-imidazolium hexafluorophosphate

Due to low global warming potential and ozone depletion potential, 3, 3, 3-trifluoropropene (HFO1243zf or R1243zf) has attracted much attention. 1-Hexyl-3-methyl-imidazolium hexafluorophosphate ([HMIM][PF6]) and 1-octyl-3-methyl-imidazolium hexafluorophosphate ([OMIM][PF6]) with strong absorbability and hydrophobicity are assumed as potential absorbents in absorption refrigeration cycle. In this work, the solubility of R1243zf in [HMIM][PF6] and [OMIM][PF6] was measured based on isochoric saturation method under seven temperatures (283.15 K, 293.15 K, 303.15 K, 313.15 K, 323.15 K, 333.15 K and 343.15 K). The experimental solubility data was correlated using the non-random two liquid (NRTL) and Krichevsky-Kasarnovsky (K-K) model, and both models showed reasonable results. In addition, the Henry’s law constants and mixing thermodynamic properties (mixing enthalpy, entropy and Gibbs energy) for R1243zf + [HMIM][PF6] and R1243zf + [OMIM][PF6] solutions were computed, and their variation with solubility was analyzed. Besides, the dissolving performances of different HFOs (R1234ze(E), R1243zf and R1234yf) in [HMIM][PF6] and [OMIM][PF6] were compared and analyzed on basis of the published data in the literature.

Vapor–Liquid Equilibrium Experiment for Butanone and Ethyl Acetate at 101.3 kPa

The formation of azeotrope brings severe challenges to the separation of butanone and ethyl acetate, two important chemical raw materials. In this article, two ionic liquids, 1-hexyl-3-methylimidazolium bis[(trifluoromethyl) sulfonyl] {[HMIM][NTf2]} and 1-ethyl-3-methylimidazolium bis[(trifluoromethyl) sulfonyl] {[EMIM][NTf2]}, and ethylene glycol (EG) were selected as entrainers to separate butanone and ethyl acetate. Vapor–liquid equilibrium data of butanone–ethyl acetate–[EMIM][NTf2], butanone–ethyl acetate–[HMIM][NTf2], and butanone–ethyl acetate–EG were measured at atmospheric pressure. The results show that the three extractants can effectively break the azeotrope of butanone–ethyl acetate, and the significant salt effect makes [EMIM][NTf2] and [HMIM][NTf2] show better separation ability than EG. Then, a non-random two liquid (NRTL) thermodynamic model was further used to fit the experimental data, and the average relative deviation was only 0.033, indicating that the NRTL model can well describe the influence of these three entrainers on the phase equilibrium behavior of butanone–ethyl acetate.

Measurement and Thermodynamic Modeling for CO2 Solubility in the N-(2-Hydroxyethyl) Piperazine + Water System

Amine scrubbing is the most important technique for capturing CO2. The cyclic diamine N-(2-Hydroxyethyl)-piperazine (HEPZ), a derivative of piperazine, with good mutual solubility in aqueous solution, a low melting point, and a high boiling point, has the potential to replace PZ as an activator added in the mixed amine system to capture CO2. In this study, the solubility of CO2 in aqueous HEPZ solutions was determined for three HEPZ concentrations and four temperatures. The VLE data for HEPZ-H2O were obtained using a gas–liquid double circulation kettle at pressure 30–100 kPa, and the thermodynamic model for the HEPZ-H2O-CO2 system was built in Aspen Plus based on the electrolytic non-random two-liquid (ENRTL) activity model. The physical parameters for HEPZ and the interaction parameters for ENRTL, along with reaction constants of carbamate reactions, were regressed. Using the thermodynamic model, the CO2 cyclic capacity, speciation with loading, and heat of reaction for the CO2 capture system by the aqueous HEPZ solution are predicted and analyzed.

Comparative evaluation of liquid–liquid equilibria for extraction of 2,2,3,3‐tetrafluoro‐1‐propanol from water by a ZIF‐8‐porous ionic liquid

AbstractBACKGROUND2,2,3,3‐Tetrafluoro‐1‐propanol (TFP) is a benign solvent and widely used in the electronics industry as a cleaning agent. Because water and TFP can form an azeotropic mixture, it consumes energy to separate TFP from its aqueous mixtures using conventional distillation.RESULTSIn this work, the zeolitic imidazolate framework‐8 porous ionic liquid (ZIF‐8‐PIL) and the ionic liquid (IL) N‐butyl pyridinium bis(trifluoromethyl sulfonyl) imide ([Bpy][NTf2]) are used as extractants to extract TFP from its aqueous solution. ZIF‐8‐PIL was synthesized by ZIF‐8 and IL [Bpy][NTf2]. The liquid–liquid equilibrium (LLE) data for the two systems (water + TFP + ZIF‐8‐PIL/IL) were determined at 298.15, 308.15 and 318.15 K under 101.3 kPa. The selectivity (S) and distribution coefficient (D) were examined to assess the extractive performance of ZIF‐8‐PIL and IL. The non‐random two‐liquid (NRTL) model was applied to fit the tie‐line data of the investigated mixtures.CONCLUSIONThe results demonstrate that ZIF‐8‐PIL is a suitable extractant to separate TFP with values of S and D greater than unity. The NRTL model has better correlation performance for the ternary systems with root mean square deviation lower than 0.01. The obtained parameters satisfy the minimum state of the mixed Gibbs free energy, which indicated that the model parameters are reliable. © 2021 Society of Chemical Industry (SCI).

Performance of functionalized ionic liquid with double chemical sites for separating phenolic compounds: mechanism and liquid-liquid behavior studies

Ionic liquids (ILs) are recognized as green solvents in separation field. Many studies have found that the hydrogen bond between anions and solutes plays an important role during the separation process, while the cations in ILs do not. In this work, a functionalized [OHEmim][NO3], 1-hydroxyethyl-3-methylimidazole nitrate, with double chemical sites, is designed for the separation of phenolic compounds (phenol, o-, m-, p-cresol). The hydroxyl group is introduced into the cation as a chemical site. Meanwhile, the anion is also a chemical site. Thus, both the anion and the cation can interact with phenolic compounds. To verify this view, the separation performance of the IL was evaluated by mechanism analysis and liquid-liquid equilibrium behavior. Then, the σ-profiles, bond length, and interaction energy between [OHEmim][NO3] and phenolic compounds are calculated and compared with [Emim][NO3]. The liquid-liquid equilibrium (LLE) data of n-hexane + (phenol, o-, m-, p-cresol) + [OHEmim][NO3] ternary systems were determined. The separation coefficient (S) and distribution coefficient (D) were calculated to evaluate the extraction performance. Non-random two liquid (NRTL) model was adopted to correlate the experimental data, which can provide basic data and parameters for the extraction process design.

Prediction of ternary azeotropic refrigerants containing ammonia

Developing azeotropic refrigerants based on ammonia is a promising way to achieve better refrigeration performance and less refrigerant charge than using ammonia alone. In this paper, ammonia-based, homogenous ternary azeotropic refrigerants were predicted. The Peng-Robinson equation of state was combined with the non-random two-liquids (NRTL) to represent the vapor-liquid equilibrium (VLE) behavior of binary and ternary mixtures. The non-randomness binary interaction parameter α in NRTL model has a significant influence on the VLE description of the ammonia mixtures, while such influence is commonly weak in hydrocarbon or hydrofluorocarbon mixtures at α from 0.2 to 0.47. Empirically, α = 0.2 is more suitable for ammonia mixtures rather than the conventional default value 0.3. The azeotropic loci of the mixtures were determined by the extreme pressure method. Ten ternary systems were predicted, of which three maximum-point azeotropes were found, namely ammonia + n -butane + pentafluoroethane /1,1-difluoroethane /2, 3, 3, 3 - tetrafluoroprop-1-ene. The ternary azeotropes predicted are thought to be promising substitute refrigerants.

Absorption behavior for R1234ze(E) and R1233zd(E) in [P66614][Cl] as working fluids in absorption refrigeration systems

The absorption-cycle technology driven by low-grade thermal energy has attracted significant attention. Hydrofluoroolefins refrigerant and ionic-liquid absorbent have been currently proposed as the promising candidates to traditional NH 3 /H 2 O and H 2 O/LiBr working pairs. The properties of refrigerant/absorbent pairs have a vital impact on the efficiency of an absorption-refrigeration cycle, especially the solubility of the gaseous refrigerant in an absorbent. In this work, solubilities were measured for two new working pairs (R1234ze(E)/[P 66614 ][Cl] and R1233zd(E)/[P 66614 ][Cl]) by an isochoric saturation method at the temperature range from 283.15 to 343.15 K. Solubilities increase with the increase of pressure and decrease with increase of temperature. To assess solubility model of refrigerant/IL pairs, the Krichevsky-Ilinskays (KI) equation and Nonrandom Two-Liquid (NRTL) model were used to correlate the new data. From the results, we found that the NRTL model could provide smaller deviations than KI equation. In contrast with the existing IL, the [P 66614 ][Cl] has the highest solubility. Furthermore, the enthalpy, entropy, and Gibbs energy of dissolution were estimated.

Isobaric vapor-liquid equilibrium for 2-butanone + ethanol + acetate-based ionic liquids at 101.3 kPa

Three acetate-based ionic liquids (ILs) (tetraethylammonium acetate, [N2,2,2,2][AC]; 1‑butyl‑2,3-dimethylimidazolium acetate, [BMMIM][AC]; or tributyl-methylammonium acetate, [N4,4,4,1][AC]) were used to separate the 2-butanone-ethanol azeotropic mixture as entrainer. The separation abilities of the three ILs were compared by measuring isobaric vapor-liquid equilibrium (VLE) data of the 2-butanone + ethanol + IL ternary systems at 101.3 kPa. The VLE data were well correlated through the use of the nonrandom two-liquid (NRTL) model. The azeotrope of 2-butanone + ethanol binary system is entirely eliminated when the concentration of IL achieves a certain value. The minimum mole fractions of the three ILs to completely eliminate azeotropic phenomena are 0.0146, 0.0166 and 0.0240, respectively. The breaking azeotropic capacities of the three ILs are better than that previously reported in the literatures. According to the average relative volatility, after the azeotropic point is thoroughly eliminated, the order of the separation capability of the three ILs is as below: [N2,2,2,2][AC] > [BMMIM][AC] > [N4,4,4,1][AC]. The σ-profiles were used to further explore the separation mechanism.

Parameterization of a RTPT Association Activity Coefficient Model using Spectroscopic Data

Self-associating species exhibit highly nonideal vapor-liquid phase behavior in many mixtures, which is challenging to model. The most successful models, such as the statistical associating fluid theory (SAFT) equations, are based on Wertheim's first thermodynamic perturbation theory (TPT-1). However, despite its success, the traditional TPT-1 implementations of SAFT lack the requisite flexibility to account for the cooperative effects of hydrogen bonding observed in alcohol + hydrocarbon systems. The resummed thermodynamic perturbation theory (RTPT) provides an improved representation of these systems by considering hydrogen bond cooperativity. While more robust than its TPT-1 predecessor, RTPT has only been validated against computer simulations. In this work, we develop a form of the RTPT association contribution to the activity coefficient and fit RTPT parameters to experimental infrared spectroscopic data. The agreement between the RTPT model and the experimental data is striking despite requiring only one additional parameter compared to TPT-1. Calculated enthalpies indicate the occurrence of positive hydrogen bond cooperativity in all of the systems examined. Association constants fitted to the spectroscopic data are used to calculate activity coefficient contributions using a Flory combinatorial term. For completeness, regressions of vapor-liquid equilibrium data are included and utilize a non-random two-liquid (NRTL) model residual contribution.

Solid-liquid equilibrium of 3,3-dilauryl thiodipropionate/lauryl alcohol in melt crystallization and model based process design

Melt crystallization is a promising and widely used method for obtaining pure compounds. Nonetheless, separation of 3,3-dilauryl thiodipropionate (DLTP) has not yet been realized by melt crystallization. Solid-liquid equilibrium is the fundamental for the separation process design. In this work, we evaluated the feasibility of the purification of DLTP from the DLTP/lauryl alcohol (LA) binary mixture by melt crystallization technique. For this purpose, the solid-liquid equilibrium data were measured using differential scanning calorimetry (DSC) technique. The experimental data were correlated by Wilson, Margules-3-suffix and Non-Random Two-Liquid (NRTL) activity coefficient models to obtain the binary parameters of the three models. Eutectic composition and temperature were calculated using NRTL model, which were xLA = 0.961 (molar fraction) and 295.79 K, respectively. On the basis of the solid–liquid equilibrium, the multistage countercurrent separation configurations were proposed for the separation of the binary system. The formulated Mixed Integer Nonlinear Programming (MINLP) problem was solved using the branch-and-bound algorithm. The conceptual designs for multistage countercurrent configuration were derived based on MINLP optimization by comparing results at various conditions. Results showed that at least 3 crystallization stages with keff ≤ 0.4 are required to obtain the 99% (mass fraction) DLTP product within the initial concentration range from10% to 30% (mass fraction).

Liquid–Liquid Equilibrium Data for Cyclohexane–Ethanol–Solvent Ternary Systems and Their Correlation with the Nonrandom Two-Liquid Model

Liquid–Liquid Equilibrium Data for Cyclohexane–Ethanol–Solvent Ternary Systems and Their Correlation with the Nonrandom Two-Liquid Model

Thermodynamic modeling of calcium carbonate scale precipitation: aqueous Na+-Ca2+-Cl–-HCO3–-CO32–-CO2 system

To allow for accurate calculations of calcium carbonate scaling in highly saline produced waters, we present a comprehensive thermodynamic model based on the electrolyte nonrandom two-liquid (eNRTL) activity coefficient equation for the aqueous Na+-Ca2+-Cl–-HCO3–-CO32–-CO2 system. The eNRTL binary interaction parameters for the H2O:(Na+-CO32–) pair, the H2O:(Na+-HCO3–) pair, the (Na+-Cl–):(Na+-CO32–) pair, and the (Na+-Cl–):(Na+-HCO3–) pair are identified in this work via the regression of thermodynamic, calorimetric, and phase equilibria experimental data. The binary interaction parameters associated with the H2O:(Na+-Cl–) pair, the CO2:(Na+-Cl–) pair, the H2O:(Ca2+-Cl–) pair, and the (Na+-Cl–):(Ca2+-Cl–) pair are retrieved from the literature. The remaining binary interaction parameters are retrieved from Aspen Plus or set to zero. In addition, the solubility product constants are identified for Na2CO3•10H2O(s), Na2CO3•7H2O(s), Na2CO3•H2O(s), Na2CO3•NaHCO3•2H2O(s), Na2CO3•3NaHCO3(s), and CaCO3(s) via regression of solubility data. The model is capable of accurately calculating all phase equilibria and calorimetric properties at temperatures up to 473.15 K and salt concentrations up to saturation.

Design Optimization of Deep Eutectic Solvent Composition and Separation Performance of Cyclohexane and Benzene Mixtures with Extractive Distillation

Deep eutectic solvents (DESs) have properties that make them suitable candidates to be used as entrainers for extractive distillation. In the previous work, it was proven that DES(1:2) (tetrabutylammonium bromide: levulinic acid, 1:2, molar ratio) can break the cyclohexane-benzene azeotrope. In the present work, the HBA and HBD ratio and molar concentration of DES were optimized to obtain a better constitute and condition of DES to be utilized in cyclohexane and benzene extractive distillation. The physical properties and structure of the prepared DESs were characterized. Vapor–liquid equilibrium data of the ternary system (benzene + cyclohexane + DESs) were also measured at atmospheric pressure. All experimental equilibrium data were correlated with Wilson, nonrandom two-liquid (NRTL), and universal quasichemical (UNIQUAC) activity coefficient models, from which the coefficient of determination (R2) of the three pseudo-ternary systems fitting was calculated. From the obtained results, the best HBA and HBD ratio in the DESs is elucidated as 1:2, the best molar concentration of DES is 0.1, and the NRTL model predicts the experimental data more accurately than the Wilson and UNIQUAC models. From the derived mechanism, the formation of stronger hydrogen bond and π–π bond interactions between DES and benzene is obtained when HBA and HBD ratio in DES is 1:2. In other conditions, the azeotrope cannot be broken, or the efficiency is low. The present work provides an environmentally friendly method to separate aromatic/aliphatic mixtures and act as a guide for further study of DESs in extractive distillation.

Solubility measurement, modeling and mixing thermodynamic properties of R1243zf and R600a in [BMIM][Ac

3,3,3-Trifluoropropene (R1243zf) and isobutane (R600a) are considered as prominent environmentally-friendly refrigerants, and acetate-based ionic liquids are potential absorbents used in absorption refrigeration cycles. In this work, the dissolving capacities of R1243zf and R600a in one of the acetate-based ionic liquids (1-butyl-3-methylimidazolium acetate, [BMIM][Ac]) were investigated. The measurements were based on isochoric saturation method and the experimental temperature range was from 283.15 K to 343.15 K. The non-random two liquid (NRTL) model and Krichevsky-Kasarnovsky (K-K) model were utilized to model the experimental results, and both models exhibited reasonable deviations. On the basis of solubility data and correlation results, the Henry’s law constants and the mixing thermodynamic properties (mixing enthalpy, mixing entropy and Gibbs energy) for the two mixtures were determined. In addition, the dissolving abilities of R1243zf and R600a in [BMIM][Ac] were compared with the reported results of R1234yf in the literature.

Calculation of vapor-liquid equilibrium of binary precious metal alloys using modified molecular interaction volume model

In this work, the activities and activity coefficients of binary precious metal alloys (Ag-Pb, Ag-Sb, Ag-Bi, Au-Pb, Pd-Pb, Pt-Pb and Cu-Pb) were predicted using molecular interaction volume model (MIVM), modified MIVM (M-MIVM), Wilson equation and nonrandom two-liquid (NRTL) model. The average standard deviation and average relative deviations of these models were also calculated. The results show that the prediction deviations of the M-MIVM were smallest among the four thermodynamic models, indicating that the M-MIVM is reliable. On this premise, the separation coefficient and vapor-liquid equilibrium (VLE) data of Ag-Pb, Au-Pb, Pd-Pb and Pt-Pb were calculated based on the M-MIVM. The results show that the separation coefficients were much larger than one, indicating that these alloys can be easily separated by vacuum distillation. There is good agreement between the predicted and experiment VLE data, indicating that M-MIVM is reliable for the VLE calculation in vacuum distillation. The VLE phase diagrams procured in this work can afford theoretical guidance for experimental design and industrial production in vacuum distillation.

Experimental measurements for the liquid-liquid equilibrium of ternary systems [(water + methyl oleate + model mixtures of tar (naphthalene, phenanthrene and anthracene)] issued from the biomass gasification process

Energy, fuel and chemical production like syngas from biomass is increasingly attracting interest in the world, with increasing potential to replace conventional fossil fuels in the energy market.Biomass gasification has been studied widely as an efficient and sustainable technology for the syngas production.Thus, raw syngas contains a significant quantities of undesirable impurities known as syngas contaminants, especially tar which can cause major problems to the gasification process; therefore it is crucial to eliminate the generated tar in this process by one of the most promising method “the tar scrubbing oil” using a suitable extracting solvent. With this aim, an experimental study of the liquid–liquid equilibrium of the ternary systems of water + solvent (methyl oleate-biodiesel solvent) + model mixtures of tar (naphthalene, phenanthrene and anthracene) that are presented in the raw syngas was conducted at 303.2 K, 323.2 K and 343.2 K. Due to the low solubility of the studied model molecule of tars in the aqueous phase, an extraction of these analytes (naphthalene, phenanthrene and anthracene) from the aqueous phase was performed by an auxiliary solvent (dichloromethane), in which was dissolved an internal standard (hexadecane) before analysis in the GC–MS using the internal standard technique. A control analysis was systematically performed in order to ensure that all of the solute was extracted from the aqueous phase. As for the analysis of the organic phase, it was carried out in the GC–MS using the internal standard technique without any prior extraction. Coulometric Karl Fischer (KF) titration was used to quantify water in the organic phase. Partition coefficient and selectivity of the biodiesel solvent were also discussed. This work is followed by a modeling study of the same systems using the nonrandom two-liquid (NRTL) and UNIQUAC (universal quasichemical) models.