Isothermal Vapor Liquid Equilibrium Research Articles

Phase diagrams of binary systems containing tricyanomethanide-based ionic liquids and thiophene or pyridine—New experimental data and PC-SAFT modelling

Isothermal vapor–liquid equilibrium (VLE) phase diagram measurements for the binary systems composed of tricyanomethanide-based ionic liquids and thiophene or pyridine were carried out over the whole range of composition at temperature between (293.15 and 313.15) K using a static apparatus. Moreover, liquid–liquid equilibrium (LLE) phase diagrams for the investigated systems have been determined at atmospheric pressure using a dynamic method. The impact of the cation core structure (imidazolium, or pyridinium, or pyrrolidinium) on the both VLE and LLE has been discussed. Modelling of the investigated properties in terms of molecular-based equation of state, namely perturbed-chain statistical associating fluid theory (PC-SAFT), was performed. Pure-fluid parameters for ionic liquids were obtained from ambient pressure densities and the Hildebrand solubility parameters. Calculations of VLE and LLE employed binary corrections to common combining rules fitted to experimental activity coefficients of thiophene and pyridine reported previously in literature.

Isothermal vapor–liquid equilibria and excess molar enthalpy of 2-methylpyrazine (2MP) containing binary mixtures. Comparison with DISQUAC predictions

The vapour pressures of binary mixtures 2-methylpyridine with cyclohexane, n-heptane or toluene were measured by a static method in the range from 263.15 to 353.15K. The pure components vapour pressures data and those of the mixtures were correlated with the Antoine equation. The excess enthalpies were measured at 303.15K, by means of an isothermal calorimeter (C80 SETARAM model). The molar excess Gibbs energies, calculated from the vapour–liquid equilibrium data and the molar excess enthalpies compared satisfactorily with group contribution model (DISQUAC).

Vapour–liquid equilibrium at T = 308.15 K for binary systems: Dibromomethane + n-heptane, bromotrichloromethane + n-heptane, bromotrichloromethane + dibromomethane, bromotrichloromethane + bromochloromethane and dibromomethane + bromochloromethane. Experimental data and modelling

In this paper, the isothermal vapour–liquid equilibrium (VLE) at T=308.15K have been measured for liquid binary systems dibromomethane+n-heptane, bromotrichloromethane+n-heptane, bromotrichloromethane+dibromomethane, bromotrichloromethane+bromochloromethane and dibromomethane+bromochloromethane by a dynamic method. The VLE data have been reduced using the Redlich–Kister equation taking into consideration the vapour phase imperfection in terms of 2nd molar virial coefficients and molar excess Gibbs energies, GmE, have been calculated. The experimental GmE is positive for all systems presenting the greatest value for dibromomethane+n-heptane and a negligible value for dibromomethane+bromochloromethane system. From our experimental data and those reported in the literature, phase and volumetric behaviour of the binary systems containing dibromomethane, bromochloromethane, bromotrichloromethane or n-heptane have been modelled. Two equations of state, EoS, of different formulation have been used obtaining a good agreement for all systems. The mean relative deviations for the studied properties are MRD (P)=1.57%, AAD (y)=0.0116 and MRD (ρ)=0.55% for Peng–Robinson EoS, and MRD (P)=1.20%, AAD (y)=0.0093 and MRD (ρ)=0.38% for PC-SAFT EoS.

Measurement, correlation and prediction of isothermal vapor–liquid equilibria of different systems containing vegetable oils

Thermodynamic properties, in particular vapor–liquid equilibrium (VLE) data, are required for the development of reliable predictive models for systems with fatty compounds. Isothermal VLE data have been measured for mixtures of methanol, ethanol, or n-hexane with refined vegetable oils (soybean, sunflower and rapeseed) at 348.15K and 373.15K using a computer-driven static apparatus. The oils were characterized in terms of their fatty acid and corresponding triacylglycerol (TAG) compositions. For the mixtures containing vegetable oils and n-hexane a negative deviation from Raoult’s law was observed and a homogeneous behavior (no miscibility gap) was found, while the mixtures with alcohols exhibited positive deviation from ideal behavior and, in some cases, limited miscibility. On the basis of the composition of the studied vegetable oils, their relative van der Waals volume and surface area parameters were estimated by the Bondi method and their vapor pressure by a group contribution method developed by Ceriani and Meirelles [1]. The experimental VLE data were correlated together with available excess enthalpies (HE) and activity coefficients at infinite dilution (γi∞) data using the UNIQUAC model. For the fitting process the refined vegetable oil was treated as a single triacylglycerol (pseudo-component) which has the corresponding degree of unsaturation, number of carbon atoms and molar mass of the original oil composition. The overall-average errors (AAE) using UNIQUAC model are 4.46% for VLE, 7.07% for γi∞ and 5.80% for HE The experimental data were also compared with the predicted results using mod. UNIFAC (Dortmund) and an extension of this method proposed for triacylglycerols in a previous work was also tested.

Isothermal vapor–liquid equilibrium data for the ethene + 2,2,3-trifluoro-3-(trifluoromethyl)oxirane binary system between 258 and 308 K at pressures up to 4.5 MPa

Isothermal vapor–liquid equilibrium data (P–x–y) are presented for ethene+2,2,3-trifluoro-3-(trifluoromethyl)oxirane mixtures at six temperatures in the range 258.38–307.38K, and pressures up to 4.54MPa. Experimental P–x–y data were measured using an apparatus based on the “static-analytic” method. The experimental data were correlated with a model composed of the Peng–Robinson equation of state using the Mathias–Copeman alpha function, Wong–Sandler mixing rules and the NRTL local composition model. The thermodynamic model accurately represents the experimental VLE data over the entire temperature range investigated.

Isothermal Vapor–Liquid Equilibrium Data for the 1,1,2,3,3,3-Hexafluoroprop-1-ene +1,1,2,2,3,3,4,4-Octafluorocyclobutane Binary System: Measurement and Modeling from (292 to 352) K and Pressures up to 2.6 MPa

Isothermal vapor–liquid equilibrium data are presented for the 1,1,2,3,3,3-hexafluoroprop-1-ene and 1,1,2,2,3,3,4,4-octafluorocyclobutane binary system at (292.89, 323.02 and 352.71) K, with pressures ranging from (0.3 to 2.6) MPa. The data were measured using an apparatus based on the “static-analytic” method, equipped with a single movable rapid online sampler-injector (ROLSI). The expanded uncertainties are estimated at 0.11 K, 4 kPa, 0.010 and 0.007 for the temperature, pressure, and the equilibrium liquid and vapor mole fractions, respectively. The experimental vapor–liquid equilibrium data were correlated using the Peng–Robinson equation of state with the Mathias–Copeman alpha function. The model provides a satisfactory description of the experimental data.

Vapor–liquid equilibria of fluoroethane (HFC-161) + 2,3,3,3-tetrafluoroprop-1-ene (HFO-1234yf)

In this study, isothermal vapor–liquid equilibrium (VLE) data were measured for the binary system of fluoroethane (HFC-161)+2,3,3,3-tetrafluoroprop-1-ene (HFO-1234yf) over the whole composition range in the temperature range from 283.15 to 323.15K at 10K intervals. The experimental VLE data were correlated with the Peng–Robinson equation of state. The van der Waals (vdW) one-fluid mixing rule and the Wong–Sandler (WS) mixing rule with the non-random two-liquid (NRTL) activity coefficient model were both used. The correlation results show good agreement with the experimental data.

Isothermal Vapor–Liquid Equilibrium of Ethanol + Glycerol and 2-Propanol + Glycerol at Different Temperatures

Isothermal vapor–liquid equilibrium (VLE) data for two binary mixtures of ethanol + glycerol and 2-propanol + glycerol were determined at the temperature range from (323.15 to 343.15) K using a simple quasistatic ebulliometer. The experimental data were correlated with the Wilson, nonrandom two-liquid (NRTL), and universal quasichemical (UNIQUAC) activity coefficient models. Both systems show that the vapor pressures increase with increasing alcohols concentrations, and no azeotropic behaviors are exhibited. In addition, both systems show positive deviations from the Raoult’s Law.

Isothermal Vapor–Liquid Equilibrium Data for the Binary System 1,1,2,3,3,3-Hexafluoro-1-propene (R1216) + 2,2,3-Trifluoro-3-(trifluoromethyl)oxirane from (268.13 to 308.19) K

Isothermal vapor–liquid equilibrium data were measured for the binary system 1,1,2,3,3,3-hexafluoro-1-propene +2,2,3-trifluoro-3-(trifluoromethyl)oxirane from (268 to 308) K using an apparatus based on the “static-analytic” method. The expanded uncertainties in the measurements were evaluated as 0.05 K, 0.6 kPa, 0.002, and 0.003 for the temperature, pressure, and liquid and vapor mole fractions, respectively. The experimental data were correlated with the Peng–Robinson equation of state using the classical mixing rule and the Mathias–Copeman alpha function. No azeotropes were observed within the temperature and pressure range studied; however, the binary mixture had relative volatilities close to unity, indicating that separation of the mixture via standard distillation is not feasible.

Vapor–liquid equilibria of {n-heptane + toluene + [emim][DCA]} system by headspace gas chromatography

The potential use of ionic liquids (ILs) in the extraction of aromatics from aromatic/aliphatic mixtures has been widely evaluated in the last decade. In addition to the good results obtained in the extraction step, the non-volatile character of ILs could simplify the aromatic recovery unit. However, the scarce vapor–liquid equilibria (VLE) data for {aliphatic+aromatic+IL} systems demand additional experimental VLE data for such systems to correctly define the aromatic recovery from the extract stream. Only then, it will be possible to assess as a whole if the application of ILs as replacement to conventional organic solvents could represent a real improvement of the present aromatic extraction industrial methods. Thus, the aim of this work has been to measure the VLE for the {n-heptane+toluene+1-ethyl-3-methylimidazolium dicyanamide ([emim][DCA])} system. This mixture includes one of the most promising IL-based solvents reported previously for aromatic extraction. Static headspace gas chromatography (HS-GC) was employed to measure isothermal VLE at 323.2K, 343.2K, and 363.2K over the whole range of compositions within the rich-IL miscibility region. Also, the correlation of the VLE data to non-random two liquids (NRTL) thermodynamic model was successfully done. A high increase in the n-heptane relative volatility from toluene was achieved under the presence of [emim][DCA].

Isothermal vapor–liquid equilibrium and molar excess Gibbs energies of two ternary systems containing either 1-butanol or 2-butanol + 1-hexene + methylbenzene at 313.15 K

1- or 2-butanol are biomass derived alcohols and their behavior in multicomponent mixtures is important in modeling biofuels. To this respect, accurate isothermal vapor–liquid equilibrium (VLE) data are reported for two new ternary systems containing either 1-butanol or 2-butanol (1)+1-hexene (2)+methylbenzene (3) at 313.15K. An accurate static technique consisting of an isothermal total pressure cell has been used for the measurements. Data reduction was done using Barker’s method providing correlations for GE. Wohl expansion, Wilson, NRTL and UNIQUAC correlations have been successfully applied to the mixtures.

Isothermal vapor–liquid equilibrium for binary mixtures containing furfural and its derivatives

The isothermal vapor–liquid equilibrium (VLE) data were measured for the binary systems of 2-methylfuran+furfuryl alcohol, isopropyl alcohol+furfuryl alcohol, and furan+furfural at 353.2, 373.2, and 408.2K over entire composition range, including the vapor pressures of five constituent compounds. The experimental results of the investigated binary systems show no azeotrope formation and positive deviations from Raoult’s law. The thermodynamic consistency of these new binary VLE data has been confirmed by point, area, and infinite dilution tests. The Wilson–HOC, the NRTL-HOC, and the UNIQUAC-HOC models were used to correlate the VLE data. Comparable results were obtained from these three models.

Phase equilibrium data for the hydrogen sulphide + methane system at temperatures from 186 to 313 K and pressures up to about 14 MPa

Isothermal vapour–liquid equilibrium data have been measured for the methane–hydrogen sulphide (CH4+H2S) binary system at five temperatures from 186.25 to 313.08K, and pressures between 0.043 and 13.182MPa. The experimental method used in this work is of the static–analytic type, taking advantage of two pneumatic capillary samplers (Rolsi™, Armines’ patent) developed in the CTP laboratory. The data were obtained with the following maximum expanded uncertainties (k=2): u(T)=0.06K, u(P)=0.006MPa and the maximum uncertainty for compositions u(x, y)=0.010 for molar compositions. The data have been satisfactorily represented with the classical Peng and Robinson equation of state.

Separation of Benzene and Cyclohexane with Mixed Solvent Using Extractive Distillation

Isothermal Vapour-liquid equilibrium for cyclohexane (1) + benzene (2) binary system, cyclohexane (1) + benzene (2) dimethylformamide (3) ternary system and cyclohexane (1) + benzene (2) dimethylformamide (3) + cosolvent (4) quaternary systems were obtained. The effects of cosolvents (diethyl glycol, dimethylsulfoxide, N-methylformamide) on the performance of dimethylformamide in benzene-cyclohexane separation were studied. The result shows the selected cosolvents suppress the effectiveness of dimethylformamide. The result also shows that the ratio of cosolvents to dimethylformamide affects the separation factor.

Isothermal Vapor–Liquid Equilibrium Data and Thermodynamic Modeling for Binary Systems of Perfluorobutane (R610) + (Methane or Hydrogen Sulfide) at (293, 313, and 333) K

Isothermal vapor–liquid equilibrium data for binary systems comprising perfluorobutane (R610) with methane (CH4) or hydrogen sulfide (H2S) were measured at isothermal conditions of approximately (293, 313, and 333) K, and pressures up to 9.837 MPa. The data were measured using a “static-analytic” apparatus equipped with a mobile pneumatic capillary sampler. The experimental data were correlated via the direct method using two sets of thermodynamic models. The Peng–Robinson equation of state incorporating the Mathias–Copeman α function, with the Wong–Sandler mixing rule utilizing the nonrandom two-liquid activity coefficient model, was used for the correlation of the CH4 + C4F10 system, while the Soave–Redlich–Kwong equation of state incorporating the Mathias–Copeman α function, with the modified Huron–Vidal first-order mixing rule utilizing the nonrandom two-liquid activity coefficient model was used for the H2S + C4F10 system.

Vapour–liquid equilibrium of carboxylic acid–alcohol binary systems: 2-Propanol + butyric acid, 2-butanol + butyric acid and 2-methyl-1-propanol + butyric acid

Isothermal vapour–liquid equilibrium (VLE) data were measured for alcohol–carboxylic acid systems using a dynamic recirculating apparatus operated isothermally. For super-atmospheric pressures, a stainless steel version of the apparatus was used with sight glasses in the Cottrell pump and liquid and condensate sampling chambers to observe flow patterns. Data are presented for 2-propanol+butyric acid, 2-butanol+butyric acid, and 2-methyl-1-propanol+butyric acid at 333.15K, 353.15K, and 373.15K. To account for vapour phase non-ideality the iterative procedure of Prausnitz et al. [J.M. Prausnitz, T.F. Anderson, E.A. Grens, C.A. Eckert, H. Seih, J.P. O’Connell, Multicomponent Vapor–Liquid and Liquid–Liquid Equilibria, Prentice Hall, Englewood Cliffs, NJ, 1980], based on the chemical theory and corresponding states correlations, was used to obtain true species concentrations, association constants (Kii), and from these liquid phase activity coefficients. The Lewis fugacity rule was used for the true species fugacity coefficient. For the low pressures and moderate temperatures of the study, only dimerization of the acid in the vapour phase was considered. Satisfactory modelling of the data was obtained with the NRTL equation and also, for the direct (EOS) method, with the cubic-based Soave–Redlich–Kwong equation of state and the Wong–Sandler mixing rules. The high non-ideality of the vapour phase for the mixtures studied was confirmed by the considerable departure of the vapour phase correction factors, Φi, from unity. The thermodynamic consistency of the data is shown by the area test and the more rigorous Van Ness point and direct tests.

Vapor−liquid equilibria for the binary system of 2,3,3,3-tetrafluoroprop-1-ene (HFO-1234yf) + 1,1,1,2,3,3,3-heptafluoropropane (HFC-227ea)

Isothermal vapor–liquid equilibrium data for the binary system of 2,3,3,3-tetrafluoroprop-1-ene (HFO-1234yf)+1,1,1,2,3,3,3-heptafluoropropane (HFC-227ea) were measured at 10K intervals from 283.15K to 323.15K over the whole composition range. The uncertainties of the experimental data are estimated at ±5mK, ±3.5kPa, and ±0.003 for the temperature, pressure, and the equilibrium liquid and vapor mole fractions, respectively. The experimental data were correlated with the Peng–Robinson equation of state using the van der Waals mixing rule, and the binary interaction parameter was optimized to fit the experimental data. The comparison between the experimental data and the correlated results shows a good agreement.

Isothermal vapor–liquid equilibria for the binary system of dimethyl ether (DME) + methyl iodide (CH3I)

Isothermal vapor–liquid equilibrium data for the binary system of dimethyl ether (DME)+methyl iodide (CH3I) were taken with a circulation-type equilibrium apparatus in which both vapor and liquid phases were recirculated still at five temperatures: 283.15, 293.15, 303.15, 313.15 and 323.15K. This binary mixture system showed negative deviation from the Raoult's law and no azeotrope observance. The equilibrium compositions of vapor and liquid phases and pressures were reported at each temperature. The measured data were correlated with the Peng–Robinson equation of state(PR-EoS) using the Wong–Sandler mixing rules combined with the NRTL excess Gibbs free energy model and Peng–Robinson equation of state (PR-EoS) using the Universal mixing rule (UMR) as well as with the UNIQUAC model. The calculated results with this combination of equations show good agreement with experimental data taken in this study.

Measurement of Vapor–Liquid Equilibria for the Binary Mixture of Octafluoropropane and Hexafluoropropylene Oxide Containing Octafluorocyclobutane

Isothermal vapor–liquid equilibrium (VLE) data were measured for the binary systems of octafluoropropane + octafluorocyclobutane and hexafluoropropylene oxide + octafluorocyclobutane system at the ...

Phase equilibria and excess properties for binary systems in reactive distillation processes. Part II. Ethyl acetate synthesis

In this investigation isothermal vapor–liquid equilibrium data (VLE) and excess enthalpy (HE) data were measured for the binary systems required for the design of reactive distillation processes for the ethyl acetate production. The isothermal P–x data was measured with a static apparatus, the heat of mixing measurements were performed with a commercial isothermal flow calorimeter. To the experimental data from this work and mixture data from other authors temperature dependent UNIQUAC parameters were fitted.