In this study experimental liquid-liquid equilibrium data are reported for the systems water+[var epsilon]-caprolactam+1-heptanol, and water+[var epsilon]-caprolactam+1-heptanol+ammonium sulfate at 20[degree sign]C, 40[degree sign]C, and 60[degree sign]C. It is shown that with increasing temperature, the solubility of [var epsilon]-caprolactam in the organic phase increases to a greater extent than the solubility of [var epsilon]-caprolactam in the aqueous phase. An increasing salt concentration in the aqueous phase results in a salting out of [var epsilon]-caprolactam into the organic phase.

Solubilities of ammonia in room-temperature ionic liquids, 1-ethyl-3-methylimidazolium acetate, 1-ethyl-3-methylimidazolium thiocyanate, 1-ethyl-3-methylimidazolium ethylsulfate, and N,N-dimethylethanolammonium acetate have been measured for the first time. Static phase equilibrium cells used in our previous work have been slightly modified for the present solubility measurements. Six mixture compositions of each binary system were prepared for the present experiments from about 30 to 85 mol% of ammonia. Pressure-temperature-composition (PTx) data were measured at isothermal conditions of about 283, 298, 323, 348, and 373 K. Observed solubilities in the present ionic liquids are again very high, being similar to our previous report on ammonia + ionic liquid mixtures and all cases show negative deviations from ideal solution behavior. Experimental PTx data have been successfully correlated with our equation-of-state (EOS) model. All the excess properties (enthalpy, entropy, and Gibbs energy) show negative values, indicating some intermolecular complex formation between ammonia and ionic liquids. Application of the present systems to the absorption cooling-heating cycle has also been discussed.

The extraction of glycolic acid from an aqueous glycolonitrile hydrolysate with tri-n-octylamine (TOA) in diluents of 1-octanol and kerosene was investigated in this article. The influences of TOA concentration, extraction temperature and phase ratio, O/W (volume ratio of organic phase to aqueous phase) on the acid distribution coefficient and loading factor of TOA were measured. The liquid-liquid equilibrium data of glycolic acid distributed between the extract phase and the raffinate phase were determined, and correlated with a model developed from the mass action law and suitable assumptions. Additionally, the acid loaded extractants were regenerated by using pure water as the back-extractant. The results show that lower temperature is beneficial to the extraction of glycolic acid from the hydrolysate, while higher temperature and phase ratio (O/W) are favorable to the back-extraction.

Phase equilibria governing the reactive extraction of citric acid from aqueous solution into solutions of tri-n-octylamine in the single solvents toluene, chloroform and methyl isobutyl ketone are investigated. In addition to batch extraction experiments, infrared spectroscopic measurements were performed. These spectroscopic investigations yield information about the stoichiometry of complex formation. All measurements were carried out at 298.15 K. A model for the liquid-liquid equilibrium which takes into account chemical reactions as well as physical interactions in both phases is used to correlate the experimental data. In comparison with earlier work, the model was extended to include the partitioning of the amine as well as its influence on the aqueous phase pH. The model reliably describes the partitioning of acid, water and organic compounds into the coexisting phases. New model parameters are also presented in order to complement recent publications on the partitioning of other single carboxylic acids (acetic and oxalic acids) into the same water/organic solvent systems.

A new algorithm for computation of the simultaneous chemical and phase equilibrium in homogeneous as well as in heterogeneous liquid mixtures is presented. The algorithm is based on the concept of transformed coordinates and the rigorous tangent plane stability test. Using transformed coordinates, we restrict the solution space to the compositions that are already at chemical equilibrium. This reduces the dimension of the problem by the number of independent reactions and makes it possible to represent phase equilibrium in reactive systems in a similar way as in non-reactive mixtures. A global algorithm for stability analysis in multi-component, multiphase reactive mixtures has been developed. It is based on the Gibbs tangent plane stability test. In our approach, we locate all stationary points of the tangent plane distance function expressed in terms of transformed coordinates. The algorithm is independent of the specific fluid model, is self-starting and significantly improves the robustness and reliability of multiphase reactive equilibrium calculations. The method has been implemented and tested on a variety of problems, in which solutions for the entire phase diagram were found without fail, and difficult cases were successfully calculated. Illustrative examples of Gibbs free energy surface and reactive phase diagrams: isothermal liquid-liquid and isobaric vapor-liquid-liquid equilibrium diagrams for multiple liquid phases are presented.

Several approaches have been proposed for the computation of solutions to the phase and chemical equilibrium problem when the problem is postulated as the minimization of the Gibbs Free Energy function. None of them can guarantee convergence to the true optimal solution, and are dependent to a large extent on the initial starting point. Convergence to local optima often occurs, yielding incorrect phase and component distributions. In this work, the problem when the liquid phase is adequately modeled by the Non-Random Two Liquid (NRTL) activity coefficient expression is examined. The contribution of this work is twofold: firstly, a novel and important property of the Gibbs free energy expression involving the NRTL equation is provided. It is subsequently shown that by introducing new variables, the problem can then be transformed to one where a biconvex objective function is minimized over a set of bilinear constraints. Secondly, the Global OPtimization (GOP) algorithm (Floudas and Visweswaran, [3, 4]; Visweswaran and Floudas, [13, 14]) is used to exploit these induced properties of the formulation to guarantee convergence to an ?-global solution, regardless of the supplied initial point. The performance of the algorithm for a selected liquid-liquid equilibrium problem is examined.

Abstract: The phase diagrams of the following imidazolium ionic liquids, 1-ethyl-3-methylimidazolium tosylate [EMIM][TOS] + hexane or cycloheptane and 1-ethyl-3-methylimidazolium ethylsulfate [EMIM][EtSO4] + hexane or benzene, have been measured. The (solid + liquid) (SLE) and (liquid + liquid) (LLE) phase equilibria of binary mixtures containing hexyl(2-hydroxyethyl)dimethylammonium bromide (C6Br) + hexane or benzene or an alcohol (ethanol or dodecan-1-ol) and the salt with a different anion hexyl(2-hydroxyethyl)dimethylammonium tetrafluoroborate (C6BF4) + hexane or benzene or dodecan-1-ol have been measured. The effect of anion type (Br- vs BF4-) on the thermophysical properties of the IL and on the phase behavior is dependent on the strength of the cation-anion interaction in the investigated ILs and is noticeable. The phase diagrams for some novel ammonium ionic liquids, (2-decanoyloxyethyl)dimethylpentyloxymethylammonium trifluoro-acetate [C10OOEtC5OMMMN][CF3COO] or (2-methyloyoxyethyl)dimethylpentyloxyammonium acesulfamate [MOOEtC5OMMMN][Ace] or (2-hydroxyethyl)dimethylundecyloxymethylammonium dicyanamide [C11OMEtOHMMN][(CN)2N], with octan-1-ol are reported. The solvents were chosen as representatives of alkanes, cycloalkanes, aromatic hydrocarbons, and alcohols. The interaction between the most commonly studied ionic liquids and those chosen in this work with typical organic solvents was described. The solubilities were measured by a dynamic method from 250 K to the melting point of the ionic liquid or to the boiling point of water in the bath. The immiscibility of the liquid phase in [EMIM][TOS] + cycloheptane was observed. The observed upper critical solution temperature (UCST) in binary mixtures of [EMIM][TOS] + cycloheptane and [EMIM][EtSO4] + hexane or benzene was limited by the boiling temperature of the solvent. The difference between the solubilities of the three ammonium ionic liquids, [C10OOEtC5OMMMN][CF3COO] or [MOOEtC5OMMMN][Ace] or [C11OMEtOHMMN][(CN)2N], in octan-1-ol is significant: a simple eutectic system was observed for [C10OOEtC5OMMMN][CF3COO]; LLE was observed for [MOOEtC5OMMMN][Ace]; and an eutectic system with immiscibility in the liquid phase was observed for [C11OMEtOHMMN][(CN)2N]. For the system [C11OMEtOHMMN][(CN)2N] + octan-1-ol, the upper critical solution temperature was determined to be 312.9 K. Characterization and purity of the compounds were obtained by water content (Fisher method) and differential scanning microcalorimetry (DSC) analysis. From DSC, melting points, enthalpies of fusion, temperatures, and enthalpies of the solid-solid phase transitions and the temperatures of glass transition of all the investigated ionic liquids were measured.

The huge number of possible combinations of binary mixtures of alcohols and ionic liquids (ILs) make the exhaustive measurement of all these systems impracticable requiring the use of a predictive model for their study. In this work, the predictive capability of COSMO-RS, a model based on unimolecular quantum chemistry calculations, was evaluated for the description of the liquid-liquid equilibria and the vapour-liquid equilibria of binary mixtures of alcohols and several imidazolium and pyridinium-based ILs. The effect of the ions and alcohols conformers on the quality of the predictions was assessed and the quantum chemical COSMO calculation at the BP/TZVP level derived from the lower energy conformations was adopted. Although a degradation in the liquid-liquid equilibria predictions with increasing size length of the alkyl chain of the alcohol or of the ionic liquid and with the short chain alcohol methanol in the vapour-liquid equilibria predictions were observed, in general a reasonable qualitative agreement between the model predictions and experimental data for a large combination of structural variations of both alcohols and ILs was obtained. COSMO-RS can thus be very useful in the scanning of the growing number of known ILs to find suitable candidates, or help designing new ILs, for specific applications before extensive experimental measurements.