Phase diagrams of liquid-liquid equilibria for the systems water-phosphoric acid-solvent entrainer at 313.15 and 333.15 K

Liquid-liquid equilibria data have been determined for the ternary system of water + phosphoric acid + solvent entrainer (1,4-dimethylbenzene, 1,2-dichloroethane, and n-hexane) at 313.15 and 333.15 K. Experiments were carried out at atmospheric pressure using stirred and thermo-regulated cells. The ternary phase diagrams were obtained by the experimental solubility and tie-line data. The Othmer-Tobias equation was used to correlate the tie-line compositions. The measured liquid-liquid equilibrium data were compared with the non-random two liquid activity coefficient model. Root mean square deviations between experimental and calculated compositions were considered satisfactory. It was showed that the non-random two liquid model of all ternary systems presented very good satisfactory results with root mean square deviations so that this model was highly appropriate to calculate thermodynamic properties of the ternary solutions. The liquid-liquid equilibrium thermodynamic properties of water + phosphoric acid + solvent entrainer can be used in research on the nature of mixing behavior of the ternary system for molecular models and industrial applications in concentration the phosphoric acid aqueous solution.     

Binodal curve of two liquid phases and solid-liquid equilibrium for water + fatty acid + ethanol systems and water + fatty acid + acetone systems

To determine the liquid-liquid-solid three-phase equilibrium (LLSE), binodal data of the liquid-liquid equilibrium (LLE) and the solid-liquid equilibrium (SLE) have been measured for the ternary water + acetone or ethanol + lauric acid, myristic acid or palmitic acid systems. The binodal region for two liquid phases increases successively in the following order of the third component: lauric acid < myristic acid < palmitic acid. The binodal regions of the ternary systems with acetone as the second component are larger than those for ethanol. These binodal curves are not highly sensitive to temperature. The isothermal solubility of these fatty acids is considerably reduced when the water content in the aqueous phase increases. The solubility of fatty acids is successively reduced in the following order: lauric acid > myristic acid > palmitic acid. The solubility of fatty acids in aqueous solutions containing acetone is smaller than in those containing ethanol. Predictions of both the binodal curve for LLE and the SLE curve by the UNIFAC method and the NRTL equation do not represent the experimental data. However, data of the binodal curve and solubility are well correlated by the NRTL equation, and also the LLSE relationship could be represented.     

Densities and Volumetric Properties of Binary and Ternary Mixtures of Diisopropyl Ether, Fluorobenzene, α,α,α-Trifluorotoluene, and Ethanol at Temperature 298.15 K and Pressure 101 kPa

Excess molar volumes of binary mixtures of (fluorobenzene + ethanol), (fluorobenzene + diisopropyl ether), (α,α,α-trifluorotoluene + ethanol), (diisopropyl ether + ethanol), (α,α,α-trifluorotoluene + diisopropyl ether), and the ternary mixtures of (fluorobenzene + diisopropyl ether + ethanol), and (α,α,α-trifluorotoluene + diisopropyl ether + ethanol) were evaluated from density data. The densities were measured with a vibrating-tube densimeter at the temperature 298.15 K and the pressure 101 kPa.The values of the mixing volumes of the ternary systems were predicted in terms of empirical equations using binary solution data alone. The extent of chemical associations among the molecules forming the mixtures is discussed.     

Phenomenological Interpretation of the Systems Exhibiting a Closed-Loop Liquid-Liquid Phase Diagram by Using a Simple <Emphasis Type="Italic">g</Emphasis><Superscript>E</Superscript>-Model

A simple phenomenological g ^E-model based on the Flory-Huggins lattice theory was used to interpret critical behavior, excess properties and liquid-liquid equilibria of three aqueous systems that exhibit a closed-loop phase diagram: (2-butoxyethanol + water), (2,6-dimethylpyridine + water) and (tetrahydrofuran (THF) + water). The model showed flexibility in application and good performance in all the aforementioned properties. Since it describes with a very good accuracy both binodal (coexistence) curves and excess enthalpies, it was used to calculate the molar excess enthalpies of the phases in equilibrium which may be a useful task in practice.     

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.     

Identification of Additives to Render Mixtures of Gasoline and the Ethanol-Water Azeotrope Hiscible

The economical production of gasohol, in terms of both energy and dollars, is dependent upon th e use of pure, water-free ethanol. Since a small amount of water will cause phase separation in the gasohol, the ethanol must be completely water free. Rather than using pure ethanol, it was proposed to use the ethanol-water azeotrope and some kind of modifier to remove the phase splitting that would occur from using the azeotrope, thus removing the burden of producing water-free ethanol.

A thermodynamic analysis of a set of mixtures containing the gasoline, ethanol azeotrope, and an additive was performed. Each system was evaluated using a computer algorithm which interfaced liquid-liquid equilibrium calculations with the UNIFAC ac tivity coefficient prediction model. The amount of each additive necessary to produce a single phase in the mixture was then determined.

Thirty six compounds were evaluated as possible additives and, of these, six were found to require less than 10% by volume added in order to produce complete miscibility in the gasoline-ethanol azeotrope mixture. All six of these additives were alcohols. Another six components were also found for which 10 to 20% by volume added was required to produce single phase behavior.     

UNIFAC方程用于H2O—n—C12H26—D2EHPA—LaCl3—HCl萃取体系

本文实验测定了n-C_(12)H_(26)-D_2EHPA在盐酸介质中萃取La~(3+)的平衡数据和H_2O-n-C_(12)H_(26)D_2EHPA体系的活度系数.用Pitzer方程计算水相中H_2O和H~+、La~(3+)的活度系数,用UNIFAC方程计算有机相各组分的活度系数,提出了萃取剂和金属萃合物的基因划分方法,经数据拟合,获得了能在全浓度范围内适用的萃取反应平衡常数和UNIFAC参数,用这些参数成功计算了n-C_(12)H_(26)-D_2EHPA萃取La~(3+)的平衡浓度.     

Modeling gradient elution in countercurrent chromatography: efficient separation of tanshinones from Salvia miltiorrhiza Bunge

Countercurrent chromatography (CCC) is a support-free liquid-liquid chromatography using centrifugal fields to hold the liquid stationary phase. CCC has been widely applied in the separation of various natural and synthetic components using a variety of biphasic liquid systems. The related hexane or heptane/ethyl acetate/methanol or ethanol/water biphasic liquid systems demonstrated their significance in CCC. Gradient is difficult in CCC since any composition change in one phase induces a composition change of the other phase to maintain phase equilibrium. This work provides a new insight into linear gradient elution in CCC that is feasible with some biphasic liquid systems such as selected compositions of the hexane/ethyl acetate/ethanol/water systems. The equations modeling solute motion inside the CCC column are proposed. Particular compositions of the liquid system, namely the hexane/ethyl acetate/ethanol/water 8:2:E:W compositions with E + W = 10, were studied from W = 1 to 9. They showed moderate changes in the upper organic phase compositions. The model is tested with the separation of tanshinones from the rhizome of Salvia miltiorrhiza Bunge. Different linear solvent gradient profiles were experimentally performed between 8:2:5:5 and 8:2:3:7 compositions and the results were evaluated using the proposed model. Five tanshinones including dihydrotanshinone I, cryptotanshinone, tanshinone I, 1,2-dihydrotanshinquinone, and tanshinone IIA have been successfully separated (>95% purities) using a gradient profile optimized by the developed model. The gradient model can be used only with biphasic liquid systems in which one phase shows minimum composition changes when the other phase composition changes notably. This case is not the general case for biphasic liquid systems but can be applied with specific compositions of the quaternary hexane or heptane/ethyl acetate/methanol or ethanol/water most useful CCC liquid systems.     

(Vapor + liquid) equilibrium for the binary systems {water + glycerol} and {ethanol + glycerol, ethyl stearate, and ethyl palmitate} at low pressures

This work reports the experimental measurements {(vapor + liquid) equilibrium} for the systems {water(1) + glycerol(2)}, {ethanol(1) + glycerol(2)}, {ethanol(1) + ethyl stearate(2)}, and {ethanol(1) + ethyl palmitate(2)}. Boiling temperatures were measured using an Othmer-type ebulliometer over a pressure range of 14 kPa to 96 kPa. The experimental data were well correlated using the NRTL and UNIQUAC models. The performance of the UNIFAC-Dortmund model in relation to predicting the phase equilibrium of the systems was also studied.     

Dendritic PtCo alloy nanoparticles as high performance oxygen reduction catalysts

We studied the physical properties and the concentration profile of benzene+water+caprolactam mixtures near the fluid-fluid interface using self-consistent field (SCF) theory. This yields the interfacial tension which plays an important role in describing the stability of transient liquid droplets of one phase in the other. The studies were performed at a fixed temperature of 313K. Flory-Huggins binary interaction parameters and the compound lattice segment numbers are input parameters for the applied SCF theory. These parameters were derived from activity coefficient relations, which are used to describe experimental liquid-liquid and vapor-liquid phase equilibrium measurements. Using first principles, the benzene-water interface was studied and the resulting interfacial tension was found to be in agreement with experimental values. This study illustrates that caprolactam accumulates at the benzene-water interface, acting as a weak surfactant. The interfacial tension is also demonstrated to be affected by the caprolactam concentration and the SCF results are in fair agreement with the experimental observations.     

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.     

Phase equilibria and modeling of ammonium ionic liquid, C2NTf2, solutions

Novel quaternary ammonium ionic liquid, ethyl(2-hydroxyethyl)dimethylammonium bis(trifluomethylsulfonyl)imide (C2NTf2), has been prepared from N,N-dimethylethanolamine as a substrate. The paper includes a specific basic characterization of the synthesized compound by NMR and the basic thermophysical properties: the melting point, enthalpy of fusion, enthalpy of solid-solid phase transition, glass transition determined by the differential scanning calorimetry (DSC), temperature of decomposition, and water content. The density of the new compound was measured. The solid-liquid or liquid-liquid phase equilibria of binary mixtures containing {C2NTf2+water or an alcohol (propan-1-ol, butan-1-ol, hexan-1-ol, octan-1-ol, decan-1-ol), aromatic hydrocarbons (benzene, toluene), aliphatic hydrocarbons (n-hexane, n-octane), dimethylsulfoxide (DMSO), or tetrahydrofuran (THF)} have been measured by a dynamic method in a wide range of temperatures from 230 to 430 K. These data were correlated by means of the nonrandom two-liquid (NRTL) equation utilizing temperature-dependent parameters derived from the solid-liquid or liquid-liquid equilibrium. From the solubility results, the negative value of the partition coefficient of ionic liquid in binary system octan-1-ol/water (log P) at 298.15 K has been calculated.     

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).     

Solvent-generated liquid-liquid chromatography with aqueous ternary systems

Summary It is shown that solvent-generated liquid-liquid chromatography can also be realized with aqueous ternary systems. One phase of such a liquid-liquid system is used as eluent and the column is packed with a porous solid support whose surface is better wetted by the other phase which is then generated dynamically on it by the mobile phase. The partition mode of retention was verified by linear regression of the chromatographic retention data and the partition coefficients measured at equilibrium. A further confirmation was obtained by the sharp change observed in the retention characteristics when approaching a composition of the mobile phase corresponding to the liquid-liquid equilibrium. The stationary phase is generated rather quickly needing between 10 and 100 times the column volume of mobile phase for equilibration depending on the magnitude of the change of composition of the mobile phase and the specific surface area of the solid support. The stability of solvent-generated LLC columns is very high allowing long term reproducibility of the selectivity coefficient of about 1 %. It is demonstrated that solvent-generated LLC offers a powerful means to optimize the separation of a mixture by chromatography. Presented at the 15th International Symposium on Chromatography, Nürnberg, October 1–5, 1984; including results already presented at the 5th International Symposium on Column Liquid Chromatography, Avignon, May 11–15, 1981.     

De-acidification of sunflower oil by solvent extraction: (Liquid + liquid) equilibrium data at T = (303.15 and 313.15) K

Short chain alcohols such as ethanol and methanol were used for extraction of oleic acid from sunflower oil. (Liquid + liquid) equilibrium data for the systems (sunflower oil + oleic acid + methanol) and (sunflower oil + oleic acid + ethanol) at T = (303.15 and 313.15) K are reported. The experimental (liquid + liquid) equilibrium data were satisfactorily correlated using the UNIQUAC activity coefficient model to obtain the binary interaction parameters. The experimental and calculated compositions of the equilibrium phases were compared and the relative mean square deviations (RMSD) are reported. The partition coefficients and the selectivity factor of the methanol and ethanol were calculated and presented. The experimental results indicate that increasing the temperature increases the distribution coefficient but decreases the selectivity factor. Our experimental results indicate that a possible alternative to reduce energy consumption is de-acidification of sunflower oil through liquid–liquid extraction by short chain alcohols, as this process is carried out at room temperature.     

Prediction of partition coefficients in ternary liquid-liquid systems as a function of the phase system composition by factor analysis for

The measured partition data of 26 steroids for six different compositions of ternary liquid-liquid systems consisting of 2,2,4-trimethylpentane, ethanol and water are used in calculations of partition data for new phase system compositions. It was possible to reproduce the original data and to verify new experimental data by this calculation with high accuracy. Calculations were done in three ways. In the first, non-linear regression of the partition coefficients as a function of the phase system composition was examined. With this classical approach it is possible to calculate the values of the partition coefficients, solute by solute, with good accuracy. In the second approach, principal component factor analysis was used. The phase system-specific factors for further phase system compositions were calculated with a non-linear regression of these factors on the phase system composition. In combination with the solute-specific factors, the values of the partition coefficients for all solutes in any phase system composition could be predicted with excellent accuracy. In the third approach, target transformation factor analysis was applied. A relationship between the partition coefficient and the phase system composition was established on the basis of either the phase system composition itself or a simple function of it. This method also gave very accurate predictions of known and unknown partition coefficients.     

Distribution ratio, distribution constant and partition coefficient. Countercurrent chromatography retention of benzoic acid

There is some confusion in chromatography between terms such as solute distribution ratio, distribution constant and partition coefficient. These terms are very precisely defined in the field of liquid-liquid systems and liquid-liquid extraction as well as in the field of chromatography with sometimes conflicting definitions. Countercurrent chromatography (CCC) is a chromatographic technique in which the stationary phase is a support-free liquid. Since the mobile phase is also liquid, biphasic liquid systems are used. This work focuses on the exact meaning of the terms since there are consequences on experimental results. The retention volumes of solutes in CCC are linearly related to their distribution ratios. The partition coefficient that should be termed (IUPAC recommendation) distribution constant is linked to a single definite species. Using benzoic acid that can dimerize in heptane and ionize in aqueous phase and an 18 mL hydrodynamic CCC column, the role and relationships between parameters and the consequences on experimental peak position and shape are discussed. If the heptane/water distribution constant (marginally accepted to be called partition coefficient) of benzoic acid is 0.2 at 20 °C and can be tabulated in books, its CCC measured distribution ratio or distribution coefficient can change between zero (basic aqueous mobile phase) and more than 25 (acidic aqueous mobile phase and elevated concentration). Benzoic acid distribution ratio and partition coefficient coincide only when both dimerization and ionization are quenched, i.e. at very low concentration and pH 2. It is possible to quench dimerization adding butanol in the heptane/water system. However, butanol additions also affect the partition coefficient of benzoic acid greatly by increasing it.     

The influence of cation, anion and temperature on the liquid-liquid equilibrium of some pentanols-water system

Liquid-liquid equilibrium (LLE) measurements for aqueous systems containing some pentanols and sodium, or potassium nitrate have been performed experimentally at 25 °C and atmospheric pressure. The pentanols are: 1-pentanol (1P), 2-pentanol (2P), 3-pentanol (3P), 2-methyl-1-butanol (3M1B) and 2-methyl-2-butanol (2M2B). The obtained data have been modeled using an extended UNIQUAC activity coefficient model. The influence of the cation, the anion and the temperature on the liquid-liquid equilibrium, are illustrated by applying the Setschenow equation on the studied systems and on other systems from literature. The results show that the influence of sodium salts is higher than that of potassium salts with the same anion and the same alcohol. On the other hand, the influence of the nitrate and bromide salts is lower than that of chloride salts with the same cation and the same alcohol. Linearity of Setschenow relation indicates that the influence of the given salts on the liquid-liquid equilibrium in the systems under study, are additive. The effect of temperature on the phase behavior is that the mutual solubilities of both liquids, in the presence of salt, decrease with temperature.     

Liquid–liquid phase equilibrium of methanol + ethylbenzene + isooctane + ethanol system at 303 K

The phase equilibrium data for methanol + ethanol + isooctane systems were obtained at 303.15 K. Data for methanol + ethylbenzene + isooctane system were taken from literature. The effect of ethanol addition on the system equilibrium was investigated at the same temperature. The distribution curves for ternary and quaternary system was analyzed. The experimental results for ternary systems were correlated with UNIQUAC and NRTL equations. For the ternary systems studied here, the NRTL equation is more accurate than the UNIQUAC. The equilibrium data for the three ternary systems were used to determine interactions parameters for the UNIQUAC equation. For the quaternary system, the experimental data can be fitted more accurately to UNIQUAC equation than by the UNIFAC method.