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Isobaric vapor–liquid equilibria (VLE) were measured for four binary systems containing tetrahydrofuran (THF): THF + water, and three different mixtures of THF + n-alkane (n-pentane, n-hexane, and n-heptane). Measurements were conducted at pressures in the range 40.0–101.3 kPa using a simple, automatic apparatus developed in our laboratory. From the experimental VLE data it was confirmed that the THF + water and THF + n-hexane systems formed minimum-boiling-point azeotropes, whereas the THF + n-pentane and THF + n-heptane systems were non-azeotropic mixtures. Non-random two-liquid (NRTL) parameters were also determined on the basis of the experimental VLE data.

A method for estimating Wilson parameters on the basis of solubility parameters and molar volumes has been adopted to correlate vapor–liquid equilibria of polar mixtures such as binary systems containing ethers, ketones, ethanol, and water. The correlation performances are examined and discussed.

The concentrations of the vapor-liquid equilibria have been measured in a small capacity recirculating still for the binaries composed of four butyl esters (from methanoate to butanoate) and propan-2-ol at a constant pressure of 101.32 kPa. VLE data were thermodynamically verified with the point-to-point test and the predictions made using several group-contribution models were acceptable but with some exceptions. An azeotrope was found for (x1butyl methanoate + x2propan-2-ol) at x1 = y1 = 0.038 and T = 354.9 K.

Isobraric p-T-x-y values for four binary mixtures composed of several butyl esters (from methanoate to butanoate) with n-propanol at 101.32 kPa have been measured using a dynamic method. All mixtures presented positi ve deviations from ideality and they were found to be thermodynamically consistent with the point-to-point test, being then correlated with suitable equations. An azeotrope at x1 = 0.300 and T = 363.7 K was found for the mixture (x1, butyl methanoate + x2 n-propanol). The group contribution models gave acceptable estimations for the γi values.

The T-x-y data for binary mixtures composed of methyl acetate + (1-chloropentane or 1-chlorohexane) and ethyl acetate + (1-chloropentane or 1-chlorohexane) have been measured ebulliometrically at 101.32 kPa using a dynamic method. In thermodynamic calculations using these data, the vapor phase was considered to be non-ideal, and the four systems studied exhibit positive deviations from Raoult's law. The activity coefficients and vapor phase compositions have been compared with those predicted by using UNIFAC and ASOG models

Isobaric vapor-liquid equilibrium data were measured at 74.66, 101.32 and 127.99 kPa for binary mixtures composed of methyl ethanoate or methyl propanoate and propan-2-ol using a dynamic method. In thermodynamic calcutions using the data, the vapor phase was considered to be non-ideal, and all the systems studied exhibit positive deviations from ideal solution behavior. At 74.66 kPa, the binary system (x1 methyl propanoate + x2 propan-2-ol) presents an azeotrope at x1 = 0.666, T = 340.47 K; as pressure increased, azeotrope concentration decreased quasi-regularly towards regions richer in propan-2-ol. After reduction of the data by fitting with a suitable equation and verification of thermodynamic consistency, various group-contribution models were applied to estimate the isobaric VLE data. The mean error in prediction of the activity coefficients for each system in no case exceeded 7%.

We present the vapor-liquid equilibrium data for the binary mixture of 1,1,1,2-tetrafluoroethane (HFC134a) + 1,1,1-trifluoroethane (HFC143a). Experimental temperatures were fixed at 278.15, 288.15, 303.15, 318.15 and 333.15 K while pressures ranged from 0.35 to 2.9 MPa. Experimental data were fitted to the Soave-Redlich-Kwong (S-R-K) and Peng-Robinson (P-R) equations of state by using a mixing rule. Optimum corresponding binary interaction parameters for these equations of state were obtained

We present vapor-liquid equilibrium data for the system of 1,1,1,2-tetrafluoroethane (HFC134a)/1,1-dichloro-2,2,2trifluoroethane (HCFC123). Temperatures were fixed at 289.17, 303.15, 318.15 and 332.74 K while pressures ranged from 0.1 to 1.5 MPa. Experimental data were correlated by the Soave-Redlich-Kwong (S-R-K) and Peng-Robinson (P-R) equations of state to evaluate the corresponding binary interaction parameters

Isothermal vapor-liquid equilibrium data of acetone-carbon dioxide system at 25°C and 40°C and methanol-carbon dioxide system at 25°C were measured with a vapor-recirculation apparatus over a pressure range from 2 to 80 atm. Experimental results obtained are analyzed by thermodynamic procedures, and the nonidealities of vapor and liquid phases are compared between these two systems.

To discuss prediction of vapor-liquid equilibria with esterification on the basis of the ASOG model, infinite-dilution binary activity coefficients were measured for five systems in the 40°-100°C range by an ebulliometric method. The systems measured are methyl acetate-n-heptane, ethyl acetate-ethanol, ethyl acetate-water, acetic acid-n-heptane, and acetic acid-ethyl acetate. The group Wilson parameters for any system made up of CH2, OH, COO, COOH groups were determined in the 40°-100°C range by infinite-dilution activity coefficients. Vapor-liquid equilibria predicted for three quaternary esterification systems and for 26 binary and ternary systems involving alcohols, water, paraffins, esters, and carboxylic acids agreed fairly well with observed values.

The perturbation theory in conjunction with the conformal solution theory was applied to the correlation of vapor-liquid equilibria of systems containing ammonia; hydrogen-ammonia, nitrogen-ammonia, argon-ammonia, methane-ammonia, and nitrogen-methane-ammonia. The Lennard-Jones potential, with temperature-dependent parameters which were determined from the P-V-T and related properties of pure substance, was used to represent the intermolecular potentials for both nonpolar and polar molecules. By comparing the calculated results with the experimental data, it was found that the perturbation theory is useful in correlating the vapor-liquid equilibria of binary and ternary mixtures containing ammonia.

A new apparatus has been designed and constructed in order to obtain reliable high-pressure vapor-liquid equilibrium data for binary systems. The vapor-liquid equilibrium phase compositions of the ethylene-propylene system were measured at 283.15 K, 298.15 K, 323.15 K and 348.15 K under pressures ranging from the vapor pressure of propylene (0.78-3.38 MPa) to the critical pressure of the mixture (5.00-5.57 MPa). Simple consistency tests were applied to both vapor and liquid compositions. Their results show the reliability of the experimental data obtained in this work. Three equations of state are used to predict the vapor-liquid equilibrium relationships of this system. Calculated values are compared with the data obtained in the present measurements. The calculated results agree well with the experimental results except near the critical region.

Thermodynamics of salt effects on vapor-liquid equilibria is discussed. Empirical activity coefficients of volatile components are defined, and the Gibbs-Duhem equations for ternary systems which contain two volatile components and a non-volatile salt are developed. Furthermore, the salt effects on vapor-liquid equilibria are exactly generalized through chemical potentials and the Gibbs-Duhem equation for the systems.

The constants in the modified BWR state equations for light hydrocarbons, nitrogen and hydrogen were re-determined from volumetric data selected for their even distribution over wide ranges of temperature and pressure, and the effects of the accuracy of these equations on the prediction of vapor-liquid equilibria for binary systems consisting of the above components were investigated. It was found that the accuracy of vapor-liquid equilibrium prediction is improved greatly, even when the conventional mixing rules are used, by increasing the accuracy of the state equation for each pure component. No binary parameters in mixing rules were needed for the above binary systems, even those containing a super-critical component, if the highly improved equations of state were applied. This suggests that re-examination of the accuracy of the state equations is necessary prior to studying the effectiveness of the conventional mixing rules.

Isothermal vapor-liquid equilibrium data of propylene oxide-ethylene and ethyl ether-ethylene systems were measured by a static method at 25°C and 40°C. The consistency of experimental results is examined by an enhancement factor of the vapor phase and by the Henry constant (f2/x2) of the liquid phase. By use of the Lewis fugacity rule for ethylene in the vapor phase, the activity coefficients of liquid phase and the fugacity coefficients of vapor phase are evaluated from themodynamic relationships. The P-x-y data of both systems are correlated with the Redlich-Kwong equation modified by Soave and the perturbation equation proposed by Gubbins and Twu. In the normal probability plot of the residuals, the SRK equation gives better correlation results for both systems.

Vapor-liquid equilibrium relationships in ternary systems can be classified according to the number and types of azeotropes in them. All combinations of azeotropes however cannot exist because of thermodynamic and topological constraints. Two necessary conditions for the existence of the combinations are presented in this paper. One is the thermodynamic condition expressed as the relation among boiling temperatures of the pure materials and azeotropes in the system. The other is the topological one given in terms of indices of singular points in the vector field composed of residue curves which represents topological properties of the vapor-liquid equilibrium relationship. By use of these conditions ternary systems are classified into 113 groups.

Vapor-liquid equilibrium data are obtained for the binary systems benzene-ammonia and cyclohexene-ammonia at 0°C and 20°C, and for the ternary system benzene-cyclohexene-ammonia at 20°C by a static method. Experimental phase compositions are compared with those calculated by the equation previously reported.

The perturbation theory of Barker-Henderson was applied to the calculation of vapor-liquid equilibria of normal fluids. The previously determined Kihara potential parameters, used to evaluate the pair potential, were readjusted by the thermodynamic equilibrium condition in order to represent well the vapor-liquid coexisting regions. The potential parameters obtained were correlated by quadratic functions of acentric factor. By introducing the correction factor k12, the perturbation theory was found to be useful for correlating vapor-liquid equilibria of normal fluid mixtures except in the critical region of the mixture and near the critical temperature of the solvent.

The vapor-liquid equilibria of hydrogen-methane-propylene, hydrogen-ethylene-propane, and hydrogen-propylene-propane ternary systems were measured at temperatures from -100° to -25°C and at pressures from 20 to 80 atm. The experimental results agreed with those calculated by the BWR equation except for temperatures below the normal boiling point of the heaviest hydrocarbon. By using the vapor-liquid equilibrium data obtained, Henry''s constants for hydrogen in binary hydrocarbon solvents were determined. The nonideality of the solvent mixture was small, so that the regular solution theory was successfully applied to Henry''s constants for hydrogen in these mixed solvents.

An augmented van der Waals equation of state developed in a previous study was applied to the calculation of high-pressure vapor-liquid equilibria of non-polar asymmetric mixtures. The equation of state for a non-polar substance comprised three terms, each of which was classified into repulsion, symmetric interaction and non-polar asymmetric interaction. Two types of mixing models based on the one-fluid model, that is, the van der Waals one-fluid model and a semiempirical mixing model of Kreglewski and Kay, were tested for both repulsion and symmetric interaction terms, while two types of semiempirical mixing models based on the one-fluid model and on the threefluid model were developed for the non-polar asymmetric interaction term. This method, which applied a separate mixing model to each interaction term, provided good correlation results for the high-pressure vapor-liquid equilibria of non-polar asymmetric mixtures.

An empirical equation is proposed for correlating vapor-liquid equilibrium data of alcohol-hydrocarbon, alcohol-alcohol and alcohol aqueous solutions. It shows a slightly better fitting accuracy than a modified Wilson, NRTL and UNIQUAC equation. The posibility of correlating pair parameters is also investigated.

Vapor-liquid equilibria (VLE) for single electrolyte systems NH3-H2O, HCOOH-H2O, CH3COOH-H2O and C2H5COOH-H2O were measured at 101.3kPa in dilute electrolyte regions. The experimental data were compared with the results calculated by the Wilson equation or the Margules equation which were extended to the whole concentration range of weak electrolyte, and good agreement was found for the present systems. Further, the effect of pH on VLE was measured for NH3-H2O and CH3COOH-H2O systems at 101.3 kPa and the pH effect was predicted by using the Wilson equation mentioned above. Agreement between calculated and experimental results was very good.

Vapor-liquid equilibrium data for binary systems containing carbon dioxide: CO2-C2H6, CO2-C3H8, CO2-n-C4H10, CO2-iso-C4H10, CO2-C2H4, CO2-C3H6 and CO2-1-C4H8 were determined by the vapor recirculation method in the low-temperature range (-41.6°C-0°C). The CO2-C2H4 and CO2-C2H6 systems formed minimum-boiling azeotropes. The modified Redlich-Kwong equation of state was used to calculate vapor-liquid equilibria of these systems. It provided fairly good agreement with experiment.

Vapor-liquid equilibrium data at 760 mmHg were determined for the quaternary ethanol-isopropanol-ethyl acetate-isopropyl acetate system. Following hypothetical reaction is considered for the quaternary system.EtOH+AcOiPr→←iPrOH+AcOEt The system could be treated as a system accompanied by chemical reaction. That is, vapor-liquid equilibria for the quaternary system could be calculated from the vapor-liquid equilibrium data for the binary and ternary systems at conversion 0 or 1. Similar results were obtained for the methanol-ethanol-methyl acetate-ethyl acetate system.

A prediction method of high pressure vapor-liquid equilibria by the BWR equation of state is presented. This method in terms of ratio of mole fractions in liquid phase can be used more easily than the usual method, and is particularly useful for multicomponent system for which experimental data are not available. This method is shown to be successful in the prediction of the ternary methane-n-pentane system and quinary methane-ethane-propanen-butane-n-pentane system.

The vapor pressures of pure DMSO were measured from 30 to 150°C by ths isoteniscopic method. An empirical equation for P-T correlation is given and molal heats of vaporization are calculated. The vapor-liquid equilibrium compositions and temperatures were determined experimentally under isobaric conditions of 550, 350, and 150 mmHg pressures for DMSO-H2O system. The activity coefficients are correlated to liquid compositions by Chao and Hougen''s equation.

The applicability of the Benedict-Webb-Rubin equation to the vapor-liquid equilibria of hydrogen-hydrocarbon mixtures was studied. Nine binary and six multicomponent systems were tested over wide temperature and pressure ranges and the equation was shown to be successful. However, at low temperatures, errors became significant for heavy components. The predicted K-values were compared with those from the Chao-Seader correlation, and the former was shown to be better in general than the latter.

Vapor-liquid equilibria containing carbon dioxide: CO2-CO, CO2-Ar, CO2-CH4 and CO2-H2-CO were measured by static method at -50°C to 20°C and up to 200 atm. By using these data and the data available in literature, the extent of usefulness of the Benedict-Webb-Rubin equation (hereafter abbreviated as BWR equation) and the treatment of Leland et al. were studied. The BWR equation correctly predicted the vapor-liquid equilibria of inorganic mixtures except in the critical region, while the treatment of Leland et al. was insufficient.

Vapor-liquid equilibrium data are reported for the binary systems ethanol-nitromethane (MeNO2) and ethanol-diethylamine (Et2NH) at 730mmHg. As expected from a strong hydrogen-bond interaction between hydroxyl group and amino base, the ethanol-Et2NM system shows negative deviation from the ideal solution law and no azeotrope can be found. The ethanol-MeNO2 system shows a positive deviation. MeNO2 forms an azeotrope at 76.4°C and 75.0 mole % of ethanol. Based on these results and other activity coefficient data available, the prediction of azeotrope formation in binary ethanol solutions by the previously presented correlation and azeotrope diagram is discussed.

The Scatchard-Hildebrand theory of regular solutions was modified by introducing the excess entropy of mixing term and by using temperature dependent solubility parameters. A comparison was made of the present treatment with the data available in the literature and the experimental results concerning the n-hexane-benzene-toluene and n-hexane-benzene-monochlorobenzene systems. The modified theory was shown, from the knowledge of pure components only, to be capable of predicting vapor -liquid equilibria for systems not containing polar components and useful for screening solvents effective for extractive distillation.

By use of Eq.(1), vapor-liquid equilibria for the following five systems were predicted from binary x-y-t data, and compared with literature values and estimated values by other methods. logKi = Ai/T + Bi (1) System A : isopropanol-water-isopropyl ether System B : methanol-ethanol-water System C : ethanol-isopropanol-water System D : methanol-ethanol-isopropanol-water System E : l-hexadecene-n-tetradecane-naphthalene These systems are hypothetical reaction systems. For example, the following hypothetical reaction is considered for System A. 2 isopropanol →← isopropyl ether + water In Eq.(1) Ai is a constant determined by reaction system and component, and Bi is a constant determined from binary x-y-t data for liquid composition at hypothetical conversion 0 and/or 1. As a conclusion, it was found that the predicted values agree well with the literature values, and that Eq.(1) may be used with nearly equal accuracy to other equations.

The BWR equation was applied to correlate the vapor-liquid equilibria of the polar-nonpolar systems. Polar components studied were Freon-22, hydrogen sulfide and ammonia. The vapor-liquid equilibrium data were cited from the literature, except for the Freon-22 mixtures whose data were obtained by a static method in this paper. The BWR constants also were taken from the literature, but those of Freon-22 were determined from the principle of corresponding states and of ammonia from the P-V-T data. By introducing the interaction parameter into the constant, A0, the BWR equation was shown to be successful for correlating the vapor-liquid equilibria of the polar-nonpolar systems. The characteristics of the parameter were discussed based on the concept of intermolecular potential between unlike molecules.

Quaternary vapor-liquid equilibria with ester if) cation have been formulated mathematically. First, activity coefficients have been related to liquid compositions with polynomial equations derived from the Mar gules model, and second, the parameters Bt defined in an equation of the vapor-liquid equilibrium ratio with esterification reported previously have been represented by polynomials. Both correlations are adequate to describe the behavior of the given systems. Vapor-liquid equilibrium with reaction of the system acetic acid-ethanol-water-ethyl acetate was predicted from Wilson''s parameters obtained from binary system data only. Association equilibrium constants of dimerization and trimerization in acetic acid vapor were used to calculate modified activity coefficients, and Wilson''s parameters were determined from six binary data. The agreement of the calculated and experimental data may be considered satisfactory for the practical use to design multicomponent distillation column reactors.

The van der Waals one-fluid theory was applied to mixtures of simple molecules and to systems containing carbon dioxide. The excess properties of mixtures of simple molecules, GE, HE and VE, were well correlated by introducing correction factors, ζ12 and η12, for the Lorentz-Berthelot rules for the potential parameters between unlike molecules. Further, these parameters were useful in correlating the vapor-liquid equilibria for mixtures of simple molecules. Among systems containing carbon dioxide, the vapor-liquid equilibria for carbon dioxide-light hydrocarbon systems and carbon dioxide-fluorocarbon systems were also well correlated by introducing the correction factor, ζ12. On the other hand, systems consisting of carbon dioxide and simple molecules could be successfully correlated by adjusting the critical temperature of the light component.

Vapor-liquid equilibria were measured by the static method for the systems hydrogen-methane-ammonia and hydrogen-nitrogen-methane-ammonia at 25°C and up to approximately 200 atm. It was found that the solubilities of gases in multicomponent systems containing liquid ammonia deviate from the values estimated from the data of binary systems.

Vapor-liquid equilibrium data for the binary systems methyl acetate-methanol and methyl acetate-water were determined at 5.78 atm, 8.66 atm, and 11.57 atm under nitrogen pressure. These data were correlated by Wilson s and Scatchard s equations. In both correlations the average deviations in the predicted results were fairly small for the system methyl acetate-methanol but not for the system methyl acetate-water. The effect of pressure on the azeotrope formed was represented by two sets of empirical equations.

Purified kerosene was fractionated for 5°C rise in boiling point. Vapor-liquid equilibria of each fraction containing a minute amount of diethyl sulfide of w-propyl mercaptan were measured at 1 atmosphere. The equilibrium ratios of the minor components in each fraction are expressed as functions of the boiling point of the fraction.

Measurements of the vapor-liquid relationship for E.H.P.-mT.C.P. system are performed by use of an agitator vessel at three residual pressures (3.5 × 10-3 mmHg, 1.0 ×10-1 mmHg and 3.5×10-1 mmHg) and two liquid surface temperatures (130°C and 160°C). Independent of residual air pressure, at liquid surface temperature of 130°C this system is regarded as an ideal solution. But at liquid surface temperature of 160°C, the deviation from ideal behavior increases as the residual air pressure is lowered.