Isothermal Vapor-liquid Equilibrium Data Research Articles

Isothermal vapor–liquid equilibria for mixtures composed of 1,2-dimethoxybenzene, 2-methoxyphenol, and diphenylmethane

Diphenylmethane was found to be a potential entrainer for separating the closely boiling mixtures of 2-methoxyphenol+1,2-dimethoxybenzene via extractive distillation. To gain insight into the capability of this auxiliary agent, isothermal vapor–liquid equilibrium data were measured for the binary and the ternary mixtures containing 2-methoxyphenol, 1,2-dimethoxybenzene, and diphenylmethane at temperatures from 433.15 to 463.15 K. All the binary data passed thermodynamic consistency tests. However, there exhibits a large discrepancy between the experimental values and the predicted results from the UNIFAC model. The new data were correlated with the Wilson, the NRTL, and the UNIQUAC models, respectively. The model parameters determined from the binary data were applied to predict the phase equilibrium behavior of the ternary system.

Vapor−Liquid Equilibria and Excess Properties of Cyclohexane−1,1-Dimethylpropyl Methyl Ether (TAME) Mixtures

Vapor−liquid equilibrium (VLE) data are reported for the binary mixtures formed by cyclohexane and the branched ether 1,1-dimethylpropyl methyl ether (tert-amyl methyl ether or TAME). A Gibbs−Van Ness type apparatus was used to obtain total vapor pressure measurements for cyclohexane−TAME mixtures as a function of composition at 298.15, 308.15, 318.15, and 328.15 K. These data are analyzed together with isothermal VLE data previously obtained at 313.15 K and excess enthalpies and volumes previously determined at 298.15 K for these mixtures. The Peng−Robinson equation of state and the Wong−Sandler mixing rule, the lattice-fluid (LF) model, the Flory theory, the UNIQUAC model, and the modified UNIFAC (Dortmund) model are used to correlate or predict the VLE data and excess properties of cyclohexane−TAME mixtures.

Isothermal vapor–liquid equilibria for mixtures of 4-methoxyphenol, catechol, and p-cresol

Isothermal vapor–liquid equilibrium data are measured with a static apparatus for the binary and ternary mixtures composed of 4-methoxyphenol, catechol (1,2-dihydroxybenzene ), and p-cresol (4-methylphenol) at temperatures ranging from 423.15 to 453.15 K. While minimum pressure azeotropes are exhibited in 4-methoxyphenol+catechol, no azeotropes are found in the rest of the systems. The new binary data are correlated with the Wilson, the NRTL, and the UNIQUAC models under the assumption of an ideal vapor-phase. The model parameters, determined from these binary data, are applied to predict the phase behavior for the ternary system. The NRTL model appears to yield the best prediction.

Isothermal vapor–liquid equilibria of mixtures of (methanol+ethanol+1-propanol or 2-propanol) at 333.15 K

The UNIQUAC associated-solution theory is extended to reproduce systems containing three alcohols and is applied to binary and ternary mixtures of alcohols. The isothermal vapor–liquid equilibrium data of the liquid mixtures of (methanol+ethanol+1-propanol) and (methanol+ethanol+2-propanol) have been measured at 333.15 K using a modified Boublik vapor-recirculating still. The experimental results are analyzed by use of the UNIQUAC associated-solution theory and the UNIQUAC model with binary parameters alone. Both models give comparable results.

Vapor–liquid equilibrium data and critical points for the system H 2S+COS. Extension of the PSRK group contribution equation of state

Isothermal vapor–liquid equilibrium data for the binary system hydrogen sulfide+carbonyl sulfide were measured in the temperature range from 232 to 293 K using the static-synthetic technique. From the isothermal P− x data, the azeotropic conditions were derived. The critical line of this system was visually detected in a flow apparatus. Interaction parameters for this binary system were fitted simultaneously to all the experimental VLE and critical data for the Predictive Soave–Redlich–Kwong group contribution equation of state.

Use of the SSF equations in the Kojima-Moon-Ochi thermodynamic consistency test of isothermal vapour-liquid equilibrium data

The Kojima-Moon-Ochi (KMO) thermodynamic consistency test of vapour-liquid equilibrium (VLE) measurements for 32 isothermal data sets of binary systems of various complexity was applied using two fitting equations: the Redlich-Kister equation and the Sum of Symmetrical Functions. It was shown that the enhanced reliability of the fitting of the experimental data can change the conclusions drawn on their thermodynamic consistency in those cases of VLE data sets that are estimated to be near the border of consistency.

Vapor Liquid Equilibrium for the Binary Systems of 2-Methylpropane + Ethanenitrile and 2-Methylpropene + Ethanenitrile at 358 K

Isothermal vapor liquid equilibrium data were measured for two binary systems, 2-methylpropane + ethanenitrile and 2-methylpropene + ethanenitrile, at 358 K. The experimental method incorporates automated vapor- and liquid-phase sampling. The results were correlated by the Soave-Redlich-Kwong equation of state and the Wilson activity coefficient model.

Vapor−Liquid Equilibria for the Difluoromethane (HFC-32) + 1,1,1-Trifluoroethane (HFC-143a) System

Isothermal vapor-liquid equilibrium data of the binary system of difluoromethane (HFC-32) + 1,1,1-trifluoroethane (HFC-143a) were obtained in the temperature range from 263.15 K to 313.15 K. Temperature, pressure, and compositions of the liquid and vapor phases were measured with a circulation type apparatus. The experimental data were correlated with the Canahan-Starling-De Santis, Peng-Robinson, and Redlich-Kwong-Soave equations of state.

Vapor–liquid equilibrium data for methanol–water–NaCl at 45°C

Isothermal vapor–liquid equilibrium data at 45°C for methanol–water–NaCl system have been measured by using the two-phase-recirculating still. The compositions were determined by densities. The data were tested by the thermodynamic consistency, which was based on reduced excess free enthalpy function.

Isothermal vapour–liquid equilibria of 1-propanol–water–salt mixtures

Isothermal vapour–liquid equilibrium data at 60°C for the system 1-propanol–water–salt were obtained using the headspace gas chromatography (HSGC) technique. Three different salts were investigated in this study; NH 4Cl, NaCl and CaCl 2. The results obtained showed that while 0.50 M NH 4Cl or 0.50 M CaCl 2 had no effect on the vapour–liquid–equilibrium (VLE) of this system, NaCl with the same molarity could alter the VLE of the system and shift its azeotropic point. The azeotropic point of the system was shifted from 40 mol% 1-propanol to about 60 mol% 1-propanol when NaCl was added under saturation conditions. Good agreement with the Furter equation was observed for the experimental data with NaCl under unsaturated conditions. The salt effect parameter calculated from the Furter equation was found to be a function of the liquid concentration.

Isothermal vapour–liquid equilibrium data for the binary propan-2-one+chloroalkanes mixtures at temperatures from 298.15 K to 313.15 K

Isothermal vapour–liquid equilibrium data are reported for binary mixtures of propan-2-one with 1,1,2,2-tetrachloroethane (I) and 1,4-dichlorobutane (II) within the 298.15–313.15 K temperature range. Total vapour pressures were measured by a static method, the mixtures beeing prepared by weight and degased directly into the working cell. The experimental data were correlated by Barker's method and different expressions for excess Gibbs energy were tested. The results indicate negative deviation from ideality for mixture (I), while mixture (II) behaves almost ideally, with slightly positive deviations.

Experimental Study of Vapor–Liquid Equilibrium of Acetone–Water System Using Headspace Gas Chromatography

Isothermal vapor-liquid equilibrium (VLE) data at 60°C for the acetone–water–salt system were obtained using headspace gas chromatography. Three different salts were investigated in this study; NH4Cl, NaCl, and CaCl2. The results obtained showed that although the alteration in the VLE of the acetone–water system in the presence of any 0.5 M salt was very small, the three salts had a salting-out effect on acetone. On the other hand, significant alteration in the VLE was obtained when NaCl was added under saturation conditions. Good agreement with the Furter equation was observed for the experimental data with unsaturated NaCl salt. The salt effect parameter, obtained from the Furter equation, was found to be a function of the liquid concentration.

Measurement and Correlation of Vapor−Liquid Equilibria for Asymmetric Mixtures of Helium and Polar Compounds

Phase compositions of vapor−liquid equilibrium (VLE) were measured for three binary asymmetric systems of helium with 1-hexanol, 1-octanol, or 1-decanol at temperatures from 353 to 453 K and pressures up to 10 MPa. The solubility of helium in 1-alkanols, as evidenced by the experimental results, is enhanced by increasing both pressure and temperature. Over the investigated conditions, the saturated gas-phase composition of the 1-alkanol component decreases with an increase of pressure at a constant temperature. Henry's constants of helium in 1-alkanols were determined from the isothermal VLE data. The new data were used to test various cubic equations of state and mixing rules.

Isothermal vapour–liquid equilibria for pentan-3-one+1,4- dichlorobutane, +trichloromethane, +1,1,1-trichloroethane, +1,1,2,2-tetrachloroethane binary mixtures

Isothermal vapour–liquid equilibrium data are reported for binary mixtures containing pentan-3-one with 1,4-dichlorobutane from 343.15 to 373.15 K, trichloromethane from 313.15 to 343.15 K, 1,1,1-trichloroethane from 323.15 to 353.15 K, and 1,1,2,2-tetrachloroethane from 343.15 to 373.15 K. A modified equilibrium still is described. The experimental data were correlated using the Redlich–Kister, Wilson and NRTL models by means of the maximum likelihood method.

Isothermal vapor-liquid equilibria for mixtures of methyl tert-butyl ether, methyl acetate, and ethyl acetate

A static apparatus was applied to measure isothermal vapor-liquid equilibrium (VLE) data for binary and ternary mixtures composed of methyl tert-butyl ether (MTBE), methyl acetate, and ethyl acetate at temperatures from 353 K to 373 K. Maximum pressure azeotropes were exhibited in the MTBE + methyl acetate system. All the binary data passed thermodynamic consistency tests. Data reduction was made by both φ-γ and φ-φ methods. The model parameters determined from the binary VLE data were used for predicting the phase equilibrium behavior of the ternary system.

Vapor−Liquid Equilibria for the Difluoromethane (HFC-32) + 1,1,1,2-Tetrafluoroethane (HFC-134a) System

Isothermal vapor-liquid equilibrium data of the binary mixture of difluoromethane (HFC-32) + 1,1,1,2-tetrafluoroethane (HFC-134a) have been measured in the temperature range between 263 K and 323 K. The experiment was carried out with a circulation type apparatus with the measurement of temperature, pressure, and compositions of the liquid and vapor phases. The experimental data were correlated with the Peng-Robinson and Redlich-Kwong-Soave equations of state, and comparison with literature results has been made.

Crossover Leung–Griffiths model and the phase behavior of dilute aqueous ionic solutions

A new parametric crossover model for the phase behavior of a binary mixture is presented that corresponds to the Leung–Griffiths model in the critical region and is transformed into the regular classical expansion far away from the critical point. The model is optimized to, and leads to excellent agreement with, isothermal vapor–liquid equilibrium data for dilute aqueous solutions of sodium chloride by Bischoff and co-workers. It then accurately predicts constant-composition phase equilibrium loci as measured by independent workers. This crossover model is therefore capable of representing the thermodynamic surface of ionic solutions in a large range of temperatures and densities around the critical points of vapor–liquid equilibrium.

Vapour pressures and excess Gibbs energy of ethylbenzene-cyclooctane binary mixtures

Isothermal vapour-liquid equilibrium data at 343.15, 353.15 and 373.15 K for ethylbenzene + cyclooctane mixtures are reported. Use has been made of an ebullioneter which allowed sampling from both phases in equilibrium. Different G E expressions suitable for correlation of these data were tested. The results evidenced a positive deviation from ideality of the system.

Vapor-liquid equilibria for nitrogen with 2-methyl-1-pentanol, 1-octanol, or 1-decanol binary systems

Isothermal vapor-liquid equilibrium (VLE) data were measured for the binary systems of nitrogen with 2-methyl-1-pentanol, 1-octanol, or 1-decanol at temperatures from 333.15 K to 453.15 K and pressures up to 100 bar. Henry's constants of nitrogen in these three alcohols were determined by using the Krichevsky-Ilinskaya (KI) equation. The experimental VLE data were also correlated by the Peng-Robinson and the Patel-Teja equations of state with various mixing rules.

Vapor-liquid equilibria for the system water + tert.-pentanol at 4 temperatures

Precise isothermal vapor-liquid equilibrium data at 10, 30, 55 and 70°C for the system water + tert.-pentanol were measured using a computer-operated differential static apparatus. Activity coefficients at infinite dilution were derived from the experimental P − x data in the dilute region using a flexible Legendre polynomial, and the vapor-liquid-liquid locus was derived directly from the P − x data near the liquid-liquid phase boundary. Heteroazeotropic points were measured directly by distillation using a rotating band column. Furthermore the UNIQUAC and the NRTL models were used to correlate the experimental P − x data and to derive the azeotropic data. Experimental H E data were taken from literature and used together with the experimental P − x data to simultaneously fit temperature dependent interaction parameters for UNIQUAC and NRTL. The parameters were used to predict the azeotropic composition over a large temperature range. The results were compared with those of a simple analytical thermodynamic equation using only the pure component vapor pressure data, heats of mixing in the heterogeneous region and the azeotropic composition at one temperature. Heats of mixing were measured at 140°C with the help of a flow calorimeter in order to determine the slope of H E vs. x 1 in the heterogeneous region. The H E data were used to check the reliability of the G E model parameters and the equation to calculate the temperature dependence of the heteroazeotropic composition.