Investigation on isobaric vapor–liquid equilibrium for acetic acid + water + methyl ethyl ketone + isopropyl acetate

Isobaric vapor–liquid equilibrium (VLE) data for acetic acid + water, acetic acid + methyl ethyl ketone (MEK), MEK + isopropyl acetate, acetic acid + MEK + water and acetic acid + MEK + isopropyl acetate + water are measured at 101.33 kPa using a modified Rose cell. The nonideal behavior in vapor phase of binary systems measured in this work is analyzed through calculating fugacity coefficients since mixture containing acetic acid deviates from ideal behavior seriously in vapor phase due to the associating effect of acetic acid. Combined with Hayden–O’Connell (HOC) equation, the VLE data of the measured binary systems for acetic acid + water, acetic acid + MEK and MEK + isopropyl acetate are correlated by the NRTL and UNIQUAC models. The NRTL model parameters obtained from correlating data of binary system are used to predict the VLE data of the ternary and quaternary systems, and the predicted values obtained in this way agree well with the experimental values.     

Vapor–liquid equilibria and critical points of the CO2 + 1-hexanol and CO2 + 1-heptanol systems

Vapor–liquid equilibria (VLE), vapor–liquid–liquid equilibria (VLLE) and critical point (CP) data for the carbon dioxide+1-hexanol (at 324.56, 353.93, 397.78, 403.39, 431.82 and 432.45 K up to 20 MPa) and carbon dioxide+1-heptanol (at 313.14, 333.16, 373.32, 411.99 and 431.54 K up to 21 MPa) systems are reported. Phase behavior measurements were made in a new equilibrium cell based on the static-analytic method and capable of measurements up to 60 MPa and 673 K. The Peng–Robinson equation of state (EoS) with the Wong–Sandler mixing rules and temperature independent parameters was able to correlate and extrapolate the VLE for the carbon dioxide+1-hexanol system. However, in order to obtain good agreement with experimental data for the carbon dioxide+1-heptanol system, the mixture EoS parameters were adjusted to the experimental VLE data at each temperature.     

Isobaric vapour–liquid equilibria data for the binary system 1-propanol+1-pentanol and isobaric vapour–liquid–liquid equilibria data for the ternary system water+1-propanol+1-pentanol at 101.3 kPa

Consistent vapour–liquid equilibrium (VLE) data for the binary system 1-propanol+1-pentanol and for the ternary system water+1-propanol+1-pentanol are reported at 101.3 kPa. An instrument using ultrasound to promote the emulsification of the partly miscible liquid phases have been used in the determination of the vapour–liquid–liquid equilibrium (VLLE). The VLE and VLLE data were correlated using UNIQUAC.     

Isobaric vapor–liquid and vapor–liquid–liquid equilibrium data for the system water + ethanol + cyclohexane

Isobaric vapor–liquid (VLE) and vapor–liquid–liquid equilibria (VLLE) were measured for the ternary system water + ethanol + cyclohexane at 101.3 kPa. The experimental determination was carried out in a dynamic equilibrium still with circulation of both the vapor and liquid phases, equipped with an ultrasonic homogenizer. The experimental data demonstrated the existence of a ternary heterogeneous azeotrope at 335.6 K with a composition of 0.188, 0.292, 0.520 mole fraction of water, ethanol and cyclohexane, respectively. The experimental data were compared with those obtained using UNIFAC and NRTL models with parameters taken from literature.     

High pressure phase equilibrium properties for ethane+1-butanol system at 313.15 K

Phase equilibria and saturated densities for ethane+1-butanol system at high pressures were measured using a static-circulation apparatus at 313.15 K. The experimental apparatus equipped with three Anton Paar DMA 512S vibrating tube density meters was previously developed for measuring vapor–liquid–liquid equilibrium (VLLE) at high pressures. Co-existing phase composition and saturated density of each phase can be measured by means of the apparatus with a maximum temperature and pressure of 400 K and 20 MPa, respectively. The present experimental results include vapor–liquid equilibria (VLE), liquid–liquid equilibria (LLE), and VLLE. The equilibrium composition and density of each phase were determined by gas chromatography and density measurements, respectively. The experimental data were correlated with various equations of state.     

Isothermal vapor–liquid equilibria for binary mixtures of benzene, toluene, m-xylene, and N-methylformamide at 333.15 K and 353.15 K

Isothermal vapor–liquid equilibrium (VLE) at 333.15 K and 353.15 K for four binary mixtures of benzene + toluene, benzene + N-methylformamide, toluene + m-xylene and toluene + N-methylformamide have been obtained at pressures ranged from 0 kPa to 101.3 kPa. The NRTL, UNIQUAC and Wilson activity coefficient models have been employed to correlate experimental pressures and liquid mole fractions. The non-ideal behavior of the vapor phase has been considered by using the Soave–Redlich–Kwong equation of state in calculating the vapor mole fraction. Liquid and vapor densities were also measured by using two vibrating tube densitometers. The P–x–y diagram and the activity coefficient indicate that two mixtures of benzene + toluene and toluene + m-xylene were close to the ideal solution. However, two mixtures containing N-methylformamide present a large positive deviation from the ideal solution. The excess Gibbs energy in the benzene + toluene mixture is negative indicates that it is an exothermic system.     

High-pressure phase equilibria in the (carbon dioxide + 1-hexanol) system

(Vapour + liquid) equilibria (VLE) and (vapour + liquid + liquid) equilibria (VLLE) data for the (carbon dioxide + 1-hexanol) system were measured at (293.15, 303.15, 313.15, 333.15, and 353.15) K. Phase behaviour measurements were made in a high-pressure visual cell with variable volume, based on the static-analytic method. The pressure range under investigation was between (0.6 and 14.49) MPa. The Soave–Redlich–Kwong (SRK) equation of state (EOS) with classical van der Waals mixing rules (two-parameters conventional mixing rule, 2PCMR), was used in a semi-predictive approach, in order to represent the complex phase behaviour (critical curve, LLV line, isothermal VLE, LLE, and VLLE) of the system. The topology of phase behaviour is reasonably well predicted.     

High pressure phase equilibrium for ethylene + 1-propanol system at 283.65 K

Phase equilibria and saturated densities for ethylene+1-propanol system at high pressures were measured using a static-circulation apparatus at 283.65 K. The equilibrium composition and saturated density of each phase were determined by using gas chromatograph and vibrating tube density meters, respectively. The saturated points near the critical region are further measured by the conventional indirect method. The present experimental results include vapor–liquid equilibria (VLE), liquid–liquid equilibria (LLE), and vapor–liquid–liquid equilibria (VLLE). The experimental data were correlated with various equations of state.     

An activity coefficient model for predicting salt effects on vapor–liquid equilibria of mixed solvent systems

In the present study, an activity coefficient model, based on the concept of local volume fractions and the Gibbs–Helmholtz relation, has been developed. Some modifications were made from Tan–Wilson model (1987) and TK–Wilson model (1975) to represent activity coefficients in mixed solvent–electrolyte systems. The proposed model contains two groups of binary interaction parameters. One group for solvent–solvent interaction parameters corresponds to that given by the TK–Wilson model (1975) in salt-free systems. The other group of salt–solvent interaction parameters can be calculated either from vapor pressure or bubble temperature data in binary salt–solvent systems. It is shown that the present model can also be used to describe liquid–liquid equilibria. No ternary parameter is required to predict the salt effects on the vapor–liquid equilibria (VLE) of mixed solvent systems. By examining 643 sets of VLE data, the calculated results show that the prediction by the present model is as good as that by the Tan–Wilson model (1987), with an overall mean deviation of vapor phase composition of 1.76% and that of the bubble temperature of 0.74 K.     

Isothermal vapor–liquid equilibria and excess molar volumes for 2-methyl pyrazine (2MP) containing binary mixtures

2-Methyl pyrazine (2MP) has led to significant interest for its industrial and pharmaceutical uses. The new vapor–liquid equilibria (VLE) at 353.15 K and excess molar volumes (V^E) at 298.15 K over the whole mole fraction range for seven binaries (water, n-hexane, cyclohexane, n-heptane, methylcyclopentane (MCP), methylcyclohexane (MCH) and ethyl acetate (EA) with 2MP) have been measured. VLE were measured by using headspace gas chromatography and V^E were determined using precision density meter. The water+2MP system has only the minimum boiling azeotrope. The experimental VLE and V^E data were well correlated in terms of common g^E models and Redlich–Kister equation, respectively.     

Modeling the vapor–liquid equilibria of polymer–solvent mixtures: Systems with complex hydrogen bonding behavior

The vapor–liquid equilibria of binary polymer–solvent systems was modeled using the Non-Random Hydrogen Bonding (NRHB) model. Mixtures of poly(ethylene glycol), poly(propylene glycol), poly(vinyl alcohol) and poly(vinyl acetate) with various solvents were investigated, while emphasis was put on hydrogen bonding systems, in which functional groups of the polymer chain can self-associate or cross-associate with the solvent molecules. Effort has been made to explicitly account for all hydrogen bonding interactions. The results reveal that the NRHB model offers a flexible approach to account for various self- or cross-associating interactions. In most cases model's predictions (using no binary interaction parameter k_ij = 0) and model's correlations (using one temperature independent binary interaction parameter, k_ij ≠ 0) are in satisfactory agreement with the experimental data, despite the complexity of the examined systems.     

Phase equilibria study of Lennard–Jones mixtures by an analytical equation of state

The recently developed equation of state (EOS) for Lennard–Jones mixtures [Y. Tang, B.C.-Y. Lu, Fluid Phase Equilibria 146 (1998) 73.] is further investigated in this work for describing phase equilibria of these mixtures. The investigation covers vapor–liquid equilibria (VLE), liquid–liquid equilibria (LLE), vapor–liquid–liquid equilibria (VLLE) and vapor–vapor equilibria (VVE) over a wide range of temperatures, pressures and molecular characteristic parameters. Results from the van der Waals one-fluid (VDW1) theory are included for comparison. The newly proposed theory performs very well for VLE and LLE and the performance is better than the VDW1 theory; but both theories yield only qualitative results for VVE. It is also found that one system should exhibit VLLE, which was not noticed in previous investigations. Results from two other perturbation theories are also compared in some cases.     

Phase behavior of {carbon dioxide + [bmim][Ac]} mixtures

Carbon dioxide solubility {(vapor + liquid) equilibria: VLE} in ionic liquid, 1-butyl-3-methylimidazolium acetate ([bmim][Ac]), has been measured with a gravimetric microbalance at four isotherms about (283, 298, 323, and 348) K up to about 2 MPa. (Vapor + liquid + liquid) equilibria (VLLE: or liquid–liquid separations) have also been investigated with a volumetric method used in our previous works, since the present analysis of the VLE data using our equation-of-state model has predicted the VLLE at CO₂-rich side solutions. The prediction for the VLLE has been confirmed experimentally. CO₂ solubilities at the ionic liquid-rich side show extremely unusual behaviors; CO₂ dissolves in the ionic liquid to a great degree, but there is hardly any vapor pressure above these mixtures up to about 20 mol% of CO₂. It indicates that CO₂ may have formed a non-volatile or very low vapor pressure molecular complex with the ionic liquid. The thermodynamic excess properties (enthalpy, entropy, and Gibbs free energy) of the present system do support such a complex formation. We have conducted several other experiments to investigate the complex formation (or chemical reactions), and conclude that a minor chemical reaction occurs but the complex formation is reversible without much degradation of the ionic liquid.     

Isothermal vapor–liquid equilibria for different binary mixtures involved in the alcoholic distillation

Isothermal vapor–liquid equilibrium (VLE) data for five binary systems ethyl acetate + 3-methyl-1-butanol, ethanol + 3-methyl-1-butanol, ethyl acetate + 2-methyl-1-butanol, ethanol + 2-methyl-1-butanol, ethyl acetate + 2-methyl-1-propanol, involved in the alcoholic distillation have been determined experimentally by headspace gas chromatography. The composition in the liquid phase was corrected with the help of an iterative method by means of a G^E model. However, due to the large density difference between the liquid and the vapor, the correction of the liquid phase composition is nearly negligible. All the binary mixtures show positive deviations from Raoult's law. The experimental VLE data are well predicted by using the modified UNIFAC model (Dortmund).     

Liquid–liquid phase equilibria of the ternary system of water/1,4-dioxane/dihydromyrcene

Liquid–liquid phase equilibria (LLE) for the system of water/1,4-dioxane/dihydromyrene (DHM) were investigated experimentally at 343.15, 348.15, 353.15, 358.15 K and atmospheric pressure. The reliability of the experimental tie-lines has been confirmed by using Othmer–Tobias correlation. The NRTL and improved UNIQUAC models were used to correlate the phase equilibria in the system using the interaction parameters determined from experimental data. The root mean square deviation (RMSD) between the observed and calculated mole percents was 0.58%. It is found that NRTL and improved UNIQUAC used for LLE could provide a good correlation.     

Liquid–liquid equilibria of aromatics removal from middle distillate using NMP

We investigated the removal of aromatics from a typical Kuwait middle distillate using liquid–liquid extraction. A multicomponent system; dodecane + hexadecane + 1,3,5-trimethyl benzene (mesitylene) + butylbenzene; was used to represent the middle distillate mixture. N-methyl-2-pyrrolidone (NMP) was used as a solvent. The liquid–liquid equilibria (LLE) of the mixture was studied over a temperature range of 293–323 K and at different solvent to feed ratios (1.35–1.97). The selectivity and distribution coefficient of the solvent were correlated successfully using the universal quasi-chemical (UNIQUAC) model for the pseudo-ternary system (paraffins (1) + aromatics (2) + NMP (3)) at the studied temperature range. The UNIQUAC model fit the experimental data with an average percentage root mean square deviation (rmds) of 0.2980%.     

High-pressure multiphase equilibria in the system glycerol + olive oil + propane + AOT

This work investigated the high-pressure phase behavior of systems containing glycerol, olive oil and propane in the presence of surfactant AOT. The static synthetic method, using a variable-volume view cell, was employed for obtaining the experimental data in the temperature range from 298 to 373 K, and pressures up to 30 MPa. First, the effect of addition of AOT on the vapor pressure of pure propane was investigated and then the effect of addition of AOT to mixtures of propane + glycerol. Measurements were afterwards accomplished for the system propane + AOT + glycerol + olive oil. For the ternary system liquid–liquid (LLE) and vapor–liquid–liquid (VLLE) equilibrium were observed. Besides VLE, LLE and VLLE, the quaternary system propane + AOT + glycerol + olive oil exhibited at higher concentrations of the glycerol/olive oil ratio a fascinating phase behavior, with the occurrence of three (LLL) and four (VLLL)—phases in equilibrium.     

Isobaric vapor–liquid equilibria for the system 1-pentanol–1-propanol–water at 101.3 kPa

Consistent vapor–liquid equilibrium data for the ternary system 1-pentanol–1-propanol–water is reported at 101.3 kPa at temperatures in the range of 362–393 K. The VLE data were satisfactorily correlated with UNIQUAC model.     

Modelling (vapour + liquid) and (vapour + liquid + liquid) equilibria of {water (H2O) + methanol (MeOH) + dimethyl ether (DME) + carbon dioxide (CO2)} quaternary system using the Peng–Robinson EoS with Wong–Sandler mixing rule

The (vapour + liquid) equilibria (VLE) and (vapour + liquid + liquid) equilibria (VLLE) binary data from literature were correlated using the Peng–Robinson (PR) equation of state (EoS) with the Wong–Sandler mixing rule (WS). Two group contribution activity models were used in the PRWS: UNIFAC–PSRK and UNIFAC–Lby. The systems were successfully extrapolated from the binary systems to ternary and quaternary systems. Results indicate that the PRWS–UNIFAC–PSRK generally displays a better performance than the PRWS–UNIFAC–Lby.     

Prediction of vapor–liquid and liquid–liquid equilibria for polymer systems: Comparison of activity coefficient models

A large number of equations of state and activity coefficient models capable of describing phase equilibria in polymer solutions are available today, but only a few of these models have been applied to different systems. It is therefore useful to investigate the performance of existing thermodynamic models for complex polymer solutions which have not yet been widely studied. The present work studies the application of several activity coefficient models [P.J. Flory, Principles of Polymer Chemistry, Cornell University Press, New York, NY, 1953; T. Oishi, J.M. Prausnitz, Estimation of solvent activities in polymer solutions using a group-contribution method, Ind. Eng. Chem. Process Design Dev. 17 (1978) 333; H.S. Elbro, A. Fredenslund, P. Rasmussen, A new simple equation for the prediction of solvent activities in polymer solutions, Macromolecules 23 (1990) 4707; G.M. Kontogeorgis, A. Fredenslund, D. Tassios, Simple activity coefficient model for the prediction of solvent activities in polymer solutions, Ind. Eng. Chem. Res. 32 (1993) 362; C. Chen, A segment-based local composition model for the Gibbs energy of polymer solutions, Fluid Phase Equilib. 83 (1993) 301; A. Vetere, Rules for predicting vapor–liquid equilibria of amorphous polymer solutions using a modified Flory–Huggins equation, Fluid Phase Equilib. 97 (1994) 43; C. Qian, S.J. Mumby, B.E. Eichinger, Phase diagrams of binary polymer solutions and blends, Macromolecules 24 (1991) 1655; Y.C. Bae, J.J. Shim, D.S. Soane, J.M. Prausnitz, Representation of vapor–liquid and liquid–liquid equilibria for binary systems containing polymers: applicability of an extended Flory–Huggins equation, J. Appl. Polym. Sci. 47 (1993) 1193; G. Bogdanic, J. Vidal, A segmental interaction model for liquid–liquid equilibrium calculations for polymer solutions, Fluid Phase Equilibria 173 (2000) 241] and activity coefficient from equations of state [F. Chen, A. Fredenslund, P. Rasmussen, Group-contribution Flory equation of state for vapor–liquid equilibria en mixtures with polymers, Ind. Eng. Chem. Res. 29 (1990) 875; M.S. High, R.P. Danner, Application of the group contribution lattice—fluids EOS to polymer solutions, AIChE J. 36 (1990) 1625]. The evaluation of these models was carried out both at infinite dilution and at finite concentrations and the results compared to experimental data. Furthermore, liquid–liquid equilibrium predictions for binary polymer solutions using six activity coefficient models are compared in this work. The parameters were estimated for all the models to achieve the best possible representation of the reported experimental equilibrium behavior.