Vapor-liquid Equilibrium Measurements Research Articles

Isobaric Vapor-Liquid Equilibrium Data for Binary Mixture of 2-Methyltetrahydrofuran and Cumene

Isobaric vapor-liquid equilibrium measurements are reported for binary mixture of 2-Methyltetrahydrofuran and Cumene at 97.3 kPa. The data were obtained using a vapor recirculating type (modified Othmer's) equilibrium still. The mixture shows slight negative deviation from ideality. The system does not form an azeotrope. The experimental data obtained in this study are thermodynamically consistent according to the Herington test. The activity coefficients have been satisfactorily correlated by means of the Margules, and NRTL equations. Excess Gibbs free energy has been calculated from the experimental data. The values of activity coefficients have also been obtained by the UNIFAC group contribution method. Keywords—Binary mixture, 2-Methyltetrahydrofuran, Cumene, Vapor-liquid equilibrium, UNIFAC, Excess Gibbs free energy.

Vapor−Liquid Equilibria for the Binary System Pentafluoroethane (HFC-125) + Isobutane (HC-600a) at Temperatures from (243.15 to 333.15) K

An experimental method was presented for vapor liquid equilibrium measurement by improving the PVT measurement apparatus. Isothermal vapor liquid equilibrium data for pentafluoroethane (HFC-125) + isobutane (HC-600a) were measured at (243.15, 253.15, 263.15, 272.15, 283.15, 293.15, 303.15, 313.15, 323.15, and 333.15) K at pressures up to 3.2 MPa. The experimental data were correlated with the Peng−Robinson equation of state with van der Waals mixing rules. The overall average absolute deviation between measured pressures and calculated results from the Peng−Robinson (PR) equation of state is 0.87 %. The interaction parameters k12 were obtained for different temperatures, and the values of k12 increase from 0.12 to 0.22 as the temperature increases.

Vapor–liquid equilibrium measurements and correlations for the binary mixture of difluoromethane + isobutane and the ternary mixture of propane + isobutane + difluoromethane

Hydrocarbons such as propane (R-290), n-butane (R-600), and isobutane (R-600a) are expected candidates for CFC, HCFC, and HFC alternative working fluids for refrigerators and heat pump systems. Hydrocarbons (HCs) are environmentally acceptable refrigerants; however, most HCs have the problem of flammability. In order to maintain the safety of home refrigerators and air-conditioners, mixing a small amount of HFCs with HCs may be effective. In our previous study, the vapor–liquid equilibrium (VLE) measurements for the binary mixtures of R-290 + R-600a and the difluoromethane (R-32) + R-290 have already been performed. This study measured the VLEs of the binary mixture of R-32 + R-600a and the ternary mixture of R-290 + R-600a + R-32. Based on the experimental data, the VLEs for three binary mixtures were correlated by using the cubic equations of state with the conventional mixing rule, and the appropriate binary interaction parameters were determined for each binary mixture. For the R-290 + R-600a and R-32 + R-290 mixtures, the correlations were successful. For the R-32 + R-600a mixture, however, because of a relatively high nonideality, the accuracy of correlation was less than that for the other two mixtures. By applying the mixing rule based on the excess Gibbs free energy model, the accuracy was well improved. Moreover, by using the binary interaction parameters for each binary mixture the prediction of the VLE for the R-290 + R-600a + R-32 mixture was tested, and predicted bubble-point pressures were compared with the experimental values. The accuracy of this prediction was at similar level to the VLE correlation for the R-32 + R-600a mixture.

Vapor–liquid equilibrium for binary system of thiophene + 2,2,4-trimethylpentane at 343.15 and 353.15 K and thiophene + 2-ethoxy-2-methylpropane at 333.15 and 343.15 K

Isothermal vapor–liquid equilibrium (VLE) for thiophene + 2,2,4-trimethylpentane were measured at 343.15 and 353.15 K and thiophene + 2-ethoxy-2-methylpropane were measured at 333.15 and 343.15 K with a circulation still. Maximum pressure azeotropes were found in thiophene + 2,2,4-trimethylpentane systems, whereas thiophene + 2-ethoxy-2-methylpropane systems exhibit slight positive deviation from ideality. No azeotropic behavior was found in thiophene + 2-ethoxy-2-methylpropane systems. The experimental results were correlated with the Wilson model and also compared with the original UNIFAC, UNIFAC-Dortmund, and the COSMO-RS predictive models. Analyses of liquid and vapor phase composition were determined with gas chromatography. All VLE measurements passed the used thermodynamic consistency tests (integral, infinite dilution and point test).

Solid−Liquid Equilibrium and Activity Coefficients for Caprolactam + 1-Hexyl-3-methylimidazolium Bis(trifluoromethylsulfonyl)imide and Cyclohexanone Oxime + 1-Hexyl-3-methylimidazolium Bis(trifluoromethylsulfonyl)imide

Thermophysical properties for binary mixtures e-caprolactam + 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide and cyclohexanone oxime + 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide have been measured. New measurements of heat capacity for caprolactam (CL) in the temperature range of (260 to 370) K and parameters of fusion have been carried out. Mutual solubility of caprolactam (CL) and 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([HMIM][NTf2]) in the wide concentration range and solubility of cyclohexanone oxime (CHO) in [HMIM][NTf2] within x(CHO) from (0.2 to 1) were studied by a visual method. Activity coefficients of the components were estimated. Vapor−liquid equilibrium (VLE) of the binary mixture CL + [HMIM][NTf2] was studied using the Knudsen method. VLE measurements were carried out over the broad concentration range at temperatures between (315.3 and 331.9) K. Activity coefficients of CL in [HMIM][NTf2] have been determined from the VLE data and ar...

Vapour–liquid equilibrium for the systems butane + methanol, +2-propanol, +1-butanol, +2-butanol, +2-methyl-2-propanol at 364.5 K

Isothermal vapour–liquid equilibrium measurements for the systems of butane with methanol, 2-propanol, 1-butanol, 2-butanol and 2-methyl-2-propanol were made at 364.5 K using a static total pressure apparatus. The obtained pressure–temperature–total composition (PTz) data were converted into pressure–temperature–liquid–vapour composition (PTxy) form by means of the Barker method. Error analysis was performed on measured and calculated variables. The systems of butane with methanol and 2-propanol showed azeotropic behaviour at 364.5 K. Wilson and NRTL parameters were regressed. The VLE measurements were compared with predictions obtained using the UNIFAC, UNIFAC-Dortmund and COSMO-RS models.

Vapor−Liquid Equilibrium for Binary System of Diethyl Sulfide + n-Hexane at (338.15 and 323.15) K and Diethyl Sulfide + 1-Hexene at (333.15 and 323.15) K

Isothermal vapor−liquid equilibrium (VLE) for diethyl sulfide + n-hexane at (338.15 and 323.15) K and diethyl sulfide + 1-hexene at (333.15 and 323.15) K were measured with a circulation still. All systems exhibit a slight positive deviation from ideality. No azeotropic behavior was found in any of the systems studied. The experimental results were correlated with the Wilson model and also compared with the original UNIFAC and the COSMO-RS predictive models. The measured diethyl sulfide + n-hexane VLE have been used simultaneously with the excess enthalpy from literature for a correlation of temperature-dependent Wilson parameters. Excess molar enthalpies at 318.15 K for the diethyl sulfide + 1-hexene system were calculated from the VLE data. Analyses of liquid- and vapor-phase compositions were determined with gas chromatography. All VLE measurements passed the thermodynamic consistency tests that were used (integral, infinite dilution, and point test).

Vapor–liquid equilibrium for binary system of diethyl sulfide + cyclohexane at 353.15 and 343.15 K and diethyl sulfide + 2-ethoxy-2-methylpropane at 343.15 and 333.15 K

Isothermal vapor–liquid equilibrium (VLE) for diethyl sulfide + cyclohexane were measured at 353.15 and 343.15 K and diethyl sulfide + 2-ethoxy-2-methylpropane were measured at 343.15 and 333.15 K with a circulation still. All systems exhibit slight positive deviation from ideality. No azeotropic behavior was found in any of the systems studied. The experimental results were correlated with the Wilson model with temperature dependent parameters and also compared with the original UNIFAC, and the COSMO-RS predictive models. The measured diethyl sulfide + cyclohexane VLE have been used simultaneously with the excess enthalpy from literature for a correlation of temperature-dependent Wilson parameters. Excess molar enthalpies at 298.15 K for diethyl sulfide + 2-ethoxy-2-methylpropane system were calculated from the VLE data. Analyses of liquid and vapor-phase composition were determined with gas chromatography. All VLE measurements passed the used thermodynamic consistency tests (integral, infinite dilution and point test).

Vapor−Liquid Equilibrium for Binary System of Diethyl Sulfide + n-Heptane and Diethyl Sulfide + 2,2,4-Trimethylpentane at (363.15 and 353.15) K

Isothermal vapor−liquid equilibrium (VLE) for diethyl sulfide + n-heptane and diethyl sulfide + 2,2,4-trimethylpentane at (363.15 and 353.15) K were measured with a circulation still. Maximum pressure azeotropes were found in both systems. The experimental results were correlated with the temperature-dependent Wilson model and also compared with the original UNIFAC and COSMO-RS predictive models. The measured diethyl sulfide + n-heptane VLE have been used simultaneously with the excess enthalpy from literature for a correlation of temperature-dependent Wilson parameters. Analyses of liquid- and vapor-phase composition were determined with a gas chromatograph and a refractometer. All VLE measurements passed the three thermodynamic consistency tests used.

Isothermal vapour–liquid equilibrium for cyclic ethers with 1-chloropentane

Isothermal vapour–liquid equilibrium measurements for mixtures containing cyclic ethers: tetrahydrofuran, tetrahydropyran, 1,3-dioxolane or 1,4-dioxane and 1-chloropentane at the temperatures of 298.15, 313.15 and 328.15 K are reported. The thermodynamic consistency of the VLE measurements was satisfactorily checked with the van Ness method. Activity coefficients were correlated with Wilson, NRTL, and UNIQUAC equations. The calculated excess Gibbs functions for tetrahydrofuran and tetrahydropyran are negative over the whole composition range while for 1,3-dioxolane and 1,4-dioxane the excess Gibbs functions are positive.

Experimental Study of Thermodynamic Properties of Mixtures Containing Ionic Liquid 1-Ethyl-3-methylimidazolium Ethyl Sulfate Using Gas−Liquid Chromatography and Transpiration Method

Activity coefficients at infinite dilution of 46 solutes such as alkanes, alkenes, alkylbenzenes, linear and branched C1−C6 alcohols, esters, aldehydes, cyclohexanone oxime, and e-caprolactam in the ionic liquid (IL) 1-ethyl-3-methylimidazolium ethyl sulfate or [EMIM][EtSO4] have been determined by gas chromatography using the IL as the stationary phase. The measurements were carried out at different temperatures between (302 and 396) K. From the temperature dependence of the limiting activity coefficients, partial molar excess enthalpies at infinite dilution of the solutes in the ILs have been derived. Vapor−liquid equilibria (VLE) of binary mixtures containing water with [EMIM][EtSO4] were studied using the transpiration method. VLE measurements were carried out over the broad concentration range at temperatures between (302.9 and 322.9) K. Activity coefficients γi of water in the [EMIM][EtSO4] have been determined from the VLE data and are described formally by using the NRTL equation. Furthermore, act...

Vapor−Liquid Equilibrium for Binary System of Thiophene + n-Hexane at (338.15 and 323.15) K and Thiophene + 1-Hexene at (333.15 and 323.15) K

Isothermal vapor−liquid equilibrium (VLE) for thiophene + n-hexane at (338.15 and 323.15) K and thiophene + 1-hexene at (333.15 and 323.15) K were measured with a circulation still. Maximum pressure azeotropes were found in the thiophene + n-hexane system. Azeotropic behavior was not found for the thiophene + 1-hexene system. The experimental results were correlated with Wilson model and also compared with original UNIFAC, UNIFAC−Dortmund, and COSMO-RS predictive models. Analyses of liquid and vapor-phase composition were determined with gas chromatograph and refractometer. All VLE measurements passed the three thermodynamic consistency tests used.

Isobaric vapor–liquid equilibria for the binary systems 1-propyl alcohol + dipropyl ether and 1-butyl alcohol + dibutyl ether at 20 and 101.3 kPa

Isobaric vapor–liquid equilibrium measurements for the binary systems 1-propyl alcohol + dipropyl ether and 1-butyl alcohol + dibutyl ether are reported at 20 and 101.3 kPa. Both systems, which deviate positively from ideal behavior present a minimum boiling point azeotrope at both pressures, showing the azeotropic compositions a strong dependency on pressure. The activity coefficients and boiling points of the solutions were correlated with its composition by the Wilson, UNIQUAC, NRTL, and Wisniak–Tamir equations.

High pressure vapor–liquid equilibrium measurements of carbon dioxide with naphthalene and benzoic acid

High pressure vapor–liquid equilibrium data for binary systems of carbon dioxide with naphthalene and benzoic acid were measured at three different temperatures for each system. Experimental temperatures and pressures ranged from 373 to 458 K and 0 to 22 MPa, respectively. Dew points were also measured for naphthalene in the CO 2 rich region. The data measured provides valuable solubility information and is used to derive gas–solvent group interaction parameters for the predictive Soave–Redlich–Kwong equation of state.

Vapor Pressures and Activity Coefficients of n-Alcohols and Benzene in Binary Mixtures with 1-Methyl-3-butylimidazolium Octyl Sulfate and 1-Methyl-3-octylimidazolium Tetrafluoroborate

Vapor−liquid equilibria (VLE) of binary mixtures containing methanol, ethanol, propanol-1, and benzene in the ionic liquid [BMIM][OctS] or [OMIM][BF4] were studied by using a static method. VLE measurements were carried out over the whole concentration range at four different temperatures in the range from 298.15 K to 313.15 K. Activity coefficients γi of these solvents in the ionic liquids and osmotic coefficients φi of the ionic liquids have been determined from the VLE data and are described formally by using the NRTL equation.

Thermodynamic Properties of Mixtures Containing Ionic Liquids. 9. Activity Coefficients at Infinite Dilution of Hydrocarbons, Alcohols, Esters, and Aldehydes in Trimethyl-butylammonium Bis(trifluoromethylsulfonyl) Imide Using Gas−Liquid Chromatography and Static Method

Activity coefficients at infinite dilution of solutes such as alkanes, alkenes, and alkylbenzenes as well as of the linear and branched C1−C6 alcohols, esters, and aldehydes in the ionic liquids trimethyl-butylammonium bis(trifluoromethylsulfonyl) imide [Me3BuN][NTf2] have been determined by gas chromatography using the ionic liquids as stationary phase. The measurements were carried out at different temperatures between 302 K and 393 K. From the temperature dependence of the limiting activity coefficients, partial molar excess enthalpies at infinite dilution of the solutes in the ionic liquids have been derived. Vapor−liquid equilibria (VLE) of binary mixtures containing methanol, ethanol, and propan-1-ol in [Me3BuN][NTf2] were studied by using a static method. VLE measurements were carried out covering the whole concentration range at four different temperatures between 298.15 K and 313.15 K. Activity coefficients γi of solutes in the ionic liquid and their osmotic coefficients φi in the [Me3BuN][NTf2] have been determined from the VLE data and are described formally by using the NRTL equation. and for methanol, ethanol, and propan-1-ol in [Me3BuN][NTf2] are derived from the both the GC and the static method.

Vapor–liquid equilibrium measurements and correlations for an azeotropic system of ethane + hexafluoroethane

The research on the isothermal vapor–liquid phase behavior for the ethane (R170) + hexafluoroethane (R116) system is presented in this paper. The vapor–liquid equilibrium (VLE) data were measured at four temperatures 189.31, 192.63, 247.63 and 252.80 K with an apparatus based on recirculation method. The experimental results were correlated with the Peng–Robinson equation of state using two types of mixing rules, the Panagiotopoulos–Reid mixing rule and the Huron–Vidal mixing rule involving the NRTL model. The calculated data using the regressed parameters were compared with the previous measured results, and good agreements can be observed.

Vapor–liquid equilibria for the carbon dioxide + propane system over a temperature range from 253.15 to 323.15 K

The isothermal vapor–liquid equilibrium (VLE) data were measured for the binary system of the carbon dioxide + propane at eight temperatures ranging from 253.15 to 323.15 K. Since the blends are natural refrigerants and have good thermophysical properties, they are considered as promising alternative refrigerants. The VLE measurement was performed at pressures up to 7.2 MPa in the circulation type equipment with a view cell. The binary system was found to be a zeotropic mixture in the tested temperature range and could be correlated with a sufficient accuracy by using the Peng–Robinson equation of state (PR EoS) with the van der Waals one fluid mixing rule. A comparison with published experimental VLE data has been carried out by means of the PR equation of state.

Experimental and predicted vapour–liquid equilibrium of 1,4-dioxane with cycloalkanes and benzene

Isobaric vapour–liquid equilibrium measurements for mixtures containing 1,4-dioxane and cyclopentane, cyclohexane or benzene at the pressures of 40.0, 66.6 and 101.3 kPa are reported. The experimental data were tested for thermodynamic consistency, the calculated activity coefficients have been correlated using Wilson, NRTL and UNIQUAC equations. The system 1,4-dioxane with cyclohexane shows minimum temperature azeotropes. Using our VLE results UNIFAC and predictive Soave–Redlich–Kwong methods were tested.

Thermodynamic properties of mixtures containing ionic liquids: Vapor pressures and activity coefficients of n-alcohols and benzene in binary mixtures with 1-methyl-3-butyl-imidazolium bis(trifluoromethyl-sulfonyl) imide

Vapor–liquid equilibria (VLE) of binary mixtures containing methanol, ethanol, propanol-1 and benzene in the ionic liquid [BMIM] [NTf 2] were studied by using a static method. VLE measurements were carried out over the whole concentration range at four different temperatures in the range from 298.15 to 313.15 K. Activity coefficients γ i of these solvents in the ionic liquid have been determined from the VLE data and are described formally by using the NRTL equation.