Liquid-liquid Equilibria Of Systems Research Articles

Liquid–liquid equilibria of the ternary system (cyclopentanol + water + cyclopentyl formate) at (298.2–338.2) K: Measurements and correlation

Cyclopentanol is an important intermediate in a production of many chemical specialties. This paper relates to a development of a new technology of indirect cyclopentene hydration in the presence of formic acid and presents the data of liquid-liquid equilibrium (LLE) for the ternary system of (cyclopentanol + water + cyclopentyl formate) under atmospheric pressure and within a temperature range from 298.2 K to 338.2 K. The experiments were conducted in a temperature-controlled glass cell and the received data were correlated with nonrandom two-liquid (NRTL) and universal quasichemical (UNIQUAC) equations in order to obtain binary coefficients describing LLE of the given system. A consistency of the experimental tie-lines data was validated by the Bachman and Othmer-Tobias equations and the data fitting accuracy was evaluated by the use of the calculated average absolute deviation and the root-mean-square-error values. According to our best knowledge, the LLE of this system have not yet been published elsewhere and the values of binary interaction parameters should be used for the design of the reactor and separation units in the process of indirect cyclopentene hydration.

Liquid-liquid equilibrium in systems used for the production of 5-hydroxymethylfurfural from biomass using alcohols as solvents

The present work reports liquid–liquid equilibrium data for systems containing water+5-hydroxymethylfurfural+{1-butanol, 2-butanol or 2-pentanol} at T=298.2K and atmospheric pressure (∼0.1MPa), determined by refractometry and density measurements. The results were evaluated by calculation of the overall mass balance, resulting in overall relative deviations lower than 1.05%. Experimental data were correlated with the NRTL model to calculate the activity coefficient. The average root mean square deviation was equal to 0.65% for all systems. Cloud points, tie lines, partition coefficients and selectivities indicated that 2-pentanol is better than the other studied solvents for 5-hydroxymethylfurfural recovery from water.

Application of GC-PPC-SAFT EoS to ammonia and its mixtures

The GC-PPC-SAFT equation of state (EoS) is a combination of the PC-SAFT EoS proposed by Gross and Sadowski [J. Gross, G. Sadowski, Ind. Eng. Chem. Res. 40 (2001) 1244–1260] and a group contribution method proposed by Tamouza [S. Tamouza et al., Fluid Phase Equilib. 222–223 (2004) 67–76; S. Tamouza et al., Fluid Phase Equilib. 228–229 (2005) 409–419] which was extended to polar molecules by Nguyen-Huynh [D. Nguyen-Huynh et al., Fluid Phase Equilib. 264 (2008) 62–75]. It is here applied to ammonia for which parameters have been regressed on pure component data (vapour pressures and liquid molar volumes), and some mixture vapour–liquid equilibrium data. Ammonia is described with an association scheme containing four associating sites (one donor site on the nitrogen atom and an acceptor site on each hydrogen atom). It also contains a dipole moment. These resulting parameters have then been tested on vapour–liquid equilibrium (VLE) and liquid–liquid equilibrium (LLE) of mixtures with n-alkanes, cycloalkanes, aromatics and small molecules such as methane, hydrogen or nitrogen whose parameters were previously published. The vapour–liquid equilibrium and the mixing enthalpy have also been evaluated for the ammonia+water binary system. For these systems a binary interaction parameter kij and corrective parameters for the cross-association energy wαβ and volume uαβ have been used in some cases.The agreement with experimental data is encouraging as correlations and predictions are both qualitatively and quantitatively satisfactory. In terms of pure component properties, the mean absolute average deviation (AAD) for the vapour pressures is about 2.5% whereas it is about 2.7% for the saturated liquid volumes. Furthermore, predictions on mixtures with n-alkanes, cycloalkanes or aromatics show that LLE lines predicted by GC-PPC-SAFT are perfectly well-located. Finally, results for VLE with n-alkanes, aromatics, small molecules or water are as accurate as it was for previously investigated systems. These results also show that the model is able to correctly represent the sign and the order of magnitude of the mixing enthalpy for the ammonia+water system.For systems containing ammonia with alkylbenzenes, this study have highlighted that a re-adjustment of alkybenzenes groups parameters was necessary. This paper explains the fitting procedure used for the new alkylbenzenes groups parameters and show satisfactory results for VLE and LLE of systems containing ammonia and alkylbenzenes.

Modeling Liquid−Liquid Equilibrium of Ionic Liquid Systems with NRTL, Electrolyte-NRTL, and UNIQUAC

Characterization of liquid−liquid equilibrium (LLE) in systems that contain ionic liquids (ILs) is important in evaluating ILs as candidates for replacing traditional extraction and separation solvents. Although an increasing amount of experimental LLE data is becoming available, comprehensive coverage of ternary liquid-phase behavior via experimental observation is impossible. Therefore, it is important to model the LLE of mixtures that contain ILs. Experimental binary and ternary LLE data that involve ILs can be correlated using standard excess Gibbs energy models. However, the predictive capability of these models in this context has not been widely studied. In this paper, we study the effectiveness with which excess Gibbs energy models can be used to predict ternary LLE solely from binary measurements. This is a stringent test of the suitability of various models for describing LLE in systems that contain ILs. Three different excess Gibbs free energy models are evaluated: the non-random two-liquid (NRTL) model, the universal quasi-chemical (UNIQUAC) model, and the electrolyte−NRTL (eNRTL) model. In the case of eNRTL, a new formulation of the model is used, based on a symmetric reference state. To our knowledge, this is the first time that an electrolyte excess Gibbs energy model has been formulated for and applied to the modeling of multicomponent LLE for mixtures that involve ILs. Ternary systems (IL, solvent, co-solvent) that exhibit experimental phase diagrams of various types have been chosen from the literature for comparison with the predictions. Comparisons of experimental and predicted octanol−water partition coefficients are also used to evaluate the models studied.

Ternary phase equilibria of tetrahydrofuran‐polystyrene‐polytetrahydrofuran

AbstractPhase diagrams including tie lines for three ternary solvent‐polymer‐polymer systems consisting of tetrahydrofuran‐polystyrene‐polytetrahydrofuran at 30°C have been obtained using size exclusion chromatography. The effect of molecular weight on polymer‐polymer compatibility has been investigated. A liquid‐liquid equilibria (LLE) database has been used to compare UNIQUAC and a modified Flory‐Huggins model with respect to their ability to correlate LLE data. Both models contain six adjustable parameters. As previously observed in the literature, the estimation of the UNIQUAC parameters is troublesome due to the model's complexity and the intercorrelation of the parameters. On the basis of better performance and ease of use, the Flory‐Huggins model is recommended. The Flory‐Huggins model is capable of accurately describing LLE of systems which exhibit quite complex tie line behavior. © 1993 John Wiley & Sons, Inc.