Liquid Equilibria Of Binary Systems Research Articles

Thermodynamic aspects of phase equilibrium in binary water–organic solvent mixtures

It is shown that the boundary curves of liquid equilibria in binary systems characterize the temperature–concentration boundary of the existence of homogeneous mixtures whose formation is not accompanied by changes in the Gibbs energy of the system and are a combination of two branches that do not convert into each other but intersect at the temperature of homogenization of a mixture of critical composition. The phase diagrams of a number of water–organic solvent systems are analyzed to determine the thermodynamic particularities of the latter.

Modeling systems relevant to the biodiesel production using the CPA equation of state

In this study, CPA parameters for heavy esters, glycerides, organic acids, and glycerol are presented, together with trends of these parameters against the van der Waals volume. Such trends allow the prediction of parameters for compounds for which data are not available. Pure fluid parameters were estimated by adjusting model predictions to recent DIPPR correlations and carefully selected literature data. Then, the performance of CPA was evaluated in correlating the vapor – liquid and liquid – liquid equilibrium of binary systems containing fatty acids and their esters, glycerides, water, alcohols and/or glycerol. Satisfactory correlation results were obtained using one (water-acids, alcohols/water - glycerol) or two (systems containing fatty acid esters with water, alcohols or glycerol and mixtures containing glycerides and alcohols) interaction parameters. Moreover, the interaction parameters show smooth trends with carbon chain length, permitting extrapolation for systems for which data are not available. Finally, the estimated parameters and correlations were used for the prediction of liquid-liquid equilibrium of one ternary and one multicomponent mixture. The results showed that accurate predictions are feasible, however indicated the need of more accurate data, at least for important binary mixtures, such as the systems with glycerol.

Prediction of Isothermal Vapor–Liquid Equilibria of Binary Systems by Using Wilson Equation with Parameters Estimated from Pure-Component Properties

Prediction of Isothermal Vapor–Liquid Equilibria of Binary Systems by Using Wilson Equation with Parameters Estimated from Pure-Component Properties

Prediction of Vapor–Liquid Equilibria of Binary Systems at Reduced Pressures by Using Wilson Equation with Parameters Estimated from Pure-Component Properties

Prediction of Vapor–Liquid Equilibria of Binary Systems at Reduced Pressures by Using Wilson Equation with Parameters Estimated from Pure-Component Properties

Comparing Four Compound-specific Cohesion Factor Relationships for Soave–Redlich–Kwong Equation of State

The approach described in one of our previous papers (Jr. Taiwan Inst. Chem. Eng., 41, pp. 570–578, 2010) was applied to the Soave–Redlich–Kwong equation of state to develop compound-specific parameters for four different types of cohesion factor models. Compound-specific parameters for nearly 300 compounds are listed in the paper and can be utilized for the modelling of phase equilibrium of the mixtures of these compounds. Performance of the models was compared based on the accuracy in predicting various pure compound properties as well as vapour liquid equilibrium of binary systems. The modified Trebble Bishnoi (mGAS) type of cohesion factor model emerged as the best amongst the compared models. Generalization of compound-specific models was also done. These expressions would be useful in the absence of compound-specific parameters.

Liquid–Liquid Equilibria for Dipropylene Glycol–Hydrocarbon Binary Systems: Experimental Data and Regression

Propylene glycols (mono- and di-) have an important potential as solvents in liquid–liquid extraction of aromatics and in azeotropic distillation. Literature and databases provide few accurate experimental data on liquid–liquid and vapor–liquid equilibria in systems consisting of propylene glycols and hydrocarbons (paraffinic, naphthenic, and aromatic hydrocarbons). However, an increasing interest in this field can be observed in recent years. This paper reports the results of an experimental study on the liquid–liquid equilibria in binary systems consisting of dipropylene glycol and paraffinic, naphthenic, and aromatic hydrocarbons with six, seven, and eight atoms of carbon. The experimental data were obtained in a high-precision thermostatic equilibrium cell. The first and most important result was that all normal paraffinic and naphthenic hydrocarbons are partially miscible with dipropylene glycol (4-oxa-2,6-heptanediol), whereas aromatics are completely dissolved. To obtain the binary interaction para...

Effect of alkanolammonium formates ionic liquids on vapour liquid equilibria of binary systems containing water, methanol, and ethanol

Vapour pressures were measured using a quasi-static ebulliometer for the pseudo-binary mixtures of (water+ethanol), (water+methanol), and (methanol+ethanol) containing an alkanolammonium-based ionic liquid (IL), namely, mono-ethanolammonium formate ([HMEA][HCOO]) and di-ethanolammonium formate ([HDEA][HCOO]), respectively, with fixed IL mass fraction of 0.30 and over the temperature ranges of (292.12 to 371.13)K. The vapour pressures of the IL-containing ternary systems were favourably correlated using the NRTL model with an overall average absolute relative deviation (AARD) of 0.0082. Further, the salt effects of [HMEA][HCOO] and [HDEA][HCOO] on isobaric vapour liquid equilibria (VLE) of azeotrope and close boiling mixture, especially for the mixtures of (water+ethanol) and (methanol+ethanol), were investigated and compared with other ILs in terms of the x′–y phase diagrams predicted with the binary NRTL parameters. It is demonstrated that the relative volatilities of ethanol to water and ethanol to methanol are enhanced, and [HMEA][HCOO] might be used as a promising entrainer for the efficient separation of ethanol aqueous solution by special rectification.

Are safe results obtained when SAFT equations are applied to ordinary chemicals? Part 2: Study of solid–liquid equilibria in binary systems

In a previous work, some irregular behaviours of the PC-SAFT EoS – and more generally of SAFT-type EoS – were pointed out for pure components at low temperatures. In particular, it was shown that for pure fluids at a fixed temperature and pressure, these equations of state were likely to exhibit up to five molar volumes, thus leading to the simultaneous existence of pseudo liquid–liquid and liquid–vapour phase equilibria at a same temperature. In this work, low-temperature calculations are performed using the PC-SAFT EoS which is combined with a fugacity model for the solid phase in order to predict solid–liquid phase equilibria. It is shown that when varying the binary-interaction parameter of the PC-SAFT equation, non-feasible phase diagrams may be calculated including for instance, the presence of a liquid–liquid azeotrope, of a liquid–liquid–solid–solid four-phase equilibrium or the simultaneous existence of several eutectic points.

Liquidus in the CO2 + and N2O + Hydrofluorocarbon Systems

The present paper summarizes and reinterprets the results for a series of measurements of solid−liquid equilibria for binary systems formed by carbon dioxide or nitrous oxide with a series of hydrofluorocarbons (fluoromethane, difluoromethane, trifluoromethane, pentafluoromethane, 1,1,1,2-tetrafluoroethane, 1,1,1-trifluoroethane, and 1,1-difluoroethane). All of the systems form eutectics. The contribution from heat capacity and activity coefficients to the liquidus courses represented by the Schröder equation were analyzed for each system included in the present study. The performed analysis showed that both mentioned contributions are small and, to a great extent, are mutually compensating each other and thus could be disregarded. The results showed that, for the systems under study, the liquidus curve down to the eutectic point may be represented by the Schröder equation involving two quantities only: the temperature at triple point and the enthalpy of fusion of the system components.

Vapor−Liquid Equilibria of Binary Systems of Ethene Oxide + Dodecane, Ethene Oxide + 1-Decanol, and Ethene Oxide + 1-Dodecanol and Prediction with the Predictive Soave−Redlich−Kwong (PSRK) Equation of State

Vapor−liquid equilibrium (VLE) measurements have been made for the binary systems ethene oxide + dodecane at four temperatures from (303.15 to 393.15) K, ethene oxide + 1-decanol at three temperatures from (303.15 to 363.15) K, and ethene oxide + 1-dodecanol at four temperatures from (313.15 to 433.15) K for varying mole fractions. An adiabatic calorimeter was used as a static apparatus for the VLE measurement. The obtained temperature, pressure, and liquid mole fraction data (T−p−x data) were used for fitting binary interaction parameters for the predictive Soave−Redlich−Kwong equation of state (PSRK EoS). The applicability of fitted parameters to other systems containing identical structural groups is shown by means of the binary system ethene oxide + 2-methylpropane and ethene oxide + 1-dodecanol.

Vapor−Liquid Equilibrium for Binary Systems of Cyclohexane + Cyclohexanone and + Cyclohexanol at Temperatures from (414.0 to 433.7) K

In this work, the vapor−liquid equilibrium (VLE) data for binary systems of cyclohexane + cyclohexanone and cyclohexane + cyclohexanol were measured using a static-analytical apparatus at temperatures from (414.0 to 433.7) K. To avoid the disturbance of pressure drop during the sampling process, a stopcock was designed inside the autoclave to block out a part of vapor-phase space quickly before sampling. The measured VLE data were correlated by the Soave−Redlich−Kwong state equation (SRK) and Wilson activity coefficient models. The Redlich−Kwong (RK) and Hayden−O’Connell (HOC) equations were used to modify the vapor ideality in the Wilson models. The fitted Wilson model with the HOC equation (Wilson-HOC) was also compared against predictive universal functional activity coefficient (UNIFAC) models (standard UNIFAC and Dortmund modified UNIFAC). By error analysis, the Wilson-HOC model gave the best fit.

Vapor−Liquid Equilibria in Binary Systems Formed by n-Hexane with Alcohols

Vapor−Liquid Equilibria in Binary Systems Formed by <i>n</i>-Hexane with Alcohols

Vapor−Liquid Equilibria in Binary Systems Formed by n-Hexane with Alcohols

The modified Świȩtoslawski ebulliometer was used for the accurate determination of vapor−liquid equilibria in binary isothermal systems formed by cyclohexane with: 2-butanol at 313.15 K, 323.15 K, 333.15 K, and 343.15 K, 2-pentanol at 333.15 K, 343.15 K, and 353.15 K, 2-methyl-2-butanol at 313.15 K, 323.15 K, 333.15 K, and 343.15 K, and 1-hexanol at 323.15 K, 333.15 K, 343.15 K, and 353.15 K. The vapor pressures of the pure substances are also given. The experimental data have been compared with literature data (if available) of those systems and correlated by means of the Redlich−Kister, NRTL, and Wilson equations.

Vapor−Liquid Equilibria in Binary Systems Formed by Cyclohexane with Alcohols

Vapor−Liquid Equilibria in Binary Systems Formed by Cyclohexane with Alcohols

Vapor−Liquid Equilibrium for Tetrahydrothiophene + n-Butane, + trans-2-Butene, + 2-Methylpropane, and + 2-Methylpropene

Isothermal vapor−liquid equilibrium of binary systems of tetrahydrothiophene + n-butane, + trans-2-butene, + 2-methylpropane, and + 2-methylpropene was measured at (318 and 346) K or 347 K with a static total pressure apparatus. The measured data were reduced to phase equilibrium data with the Barker’s method. Legendre, Wilson, NRTL, and UNIQUAC parameters were calculated. All binaries exhibited a positive deviation from the Raoult’s Law. No azeotropes were observed.

Phase Equilibria of Binary Systems Comprising Formic Acid, N,N-Dimethylformamide, 1-Chloro-2-ethylhexane, and 2-Ethyl-1-hexanol

Isobaric vapor−liquid equilibria of binary systems formed by formic acid + N,N-dimethylformamide or + 2-ethyl-1-hexanol as well as N,N-dimethylformamide + 1-chloro-2-ethylhexane were estimated at a pressure of 10.00 kPa. Mutual solubilities of formic acid + 1-chloro-2-ethylhexane were determined within the temperature range of (20 to 80) °C. The binary equilibrium data were fitted to the Redlich−Kister, Wilson, and NRTL equations employing the maximum likelihood procedure. Binary parameters of the chosen excess molar Gibbs energy models were calculated assuming ideal behavior of the vapor phase. A comparison of the goodness of fit of the selected GE models is presented.

Vapor−Liquid Equilibria in Binary Systems of Phenol or Cresols + Water, + Toluene, and + Octane and Liquid−Liquid Equilibria in Binary Systems of Cresols + Water

Isothermal vapor−liquid equilibrium data were measured at 333.15 and 363.15 K for the systems toluene + phenol, toluene + 2-cresol, toluene + 3-cresol, toluene + 4-cresol, octane + 2-cresol, octane + 3-cresol, water + phenol, and water + 3 cresol. Additionally, heteroazeotropic data of water + 2-cresol and water + 4-cresol were determined. The solubility of water in 2-cresol, 3-cresol, and 4-cresol was measured by photometric turbidity titration. Excess molar volumes for the systems toluene + phenol or cresols and octane + 2 cresol or + 3 cresol are presented together with Redlich−Kister polynomial fits. The VLE data and, if present, LLE data have been regressed according to the models NRTL, UNIQUAC, and Elliott Suresh Donohue equation of state together with data from the literature.

Equation of State for the Vapor−Liquid Equilibria of Binary Systems Containing Imidazolium-Based Ionic Liquids

The vapor−liquid equilibria of binary systems containing imidazolium-based ionic liquids (ILs) have been investigated using an equation of state (EOS) for the heteronuclear square-well chain fluids (hetero-SWCFs). ILs are represented by “diblock compounds”, with the alkyl group as one block and the imidazolium ring−anion pair as the other block. Model parameters of the imidazolium ring−anion block are obtained by fitting the experimental pressure−volume−temperature (pVT) data of ILs, and they are combined with those of the alkyl block from our previous work to correlate and predict the molar volumes of homologous imidazolium ILs, with the average deviations of 0.62% and 3.24%, respectively. Vapor−liquid equilibria (VLE) of 22 binary systems that contain imidazolium ILs and solvents are correlated, with an average deviation of 5.38%. The results reveal that the imidazolium ILs can be regarded as diblock compounds fairly well and the hetero-SWCF−EOS is well-suited for calculation of their thermophysical pro...

Vapor−Liquid Equilibrium for Binary Systems of Diacetyl with Methanol and Acetone

Diacetyl is a byproduct of sugar manufacture and has many food-related uses. Vapor−liquid equilibrium (VLE) data are required in order to design a purification process. A vapor and liquid recirculating still was used to measure data for acetone + diacetyl at 303.15 K, 313.15 K, 323.15 K, and 40 kPa. Data were also measured for methanol + diacetyl at 313.15 K, 323.15 K, 333.15 K, and 40 kPa. The γ−Φ approach to VLE was used to reduce the data to excess Gibbs energy model parameters. The vapor-phase nonideality was accounted for using the truncated (two-term) Virial equation of state. The Wilson, NRTL, and UNIQUAC excess Gibbs energy models were used to account for liquid-phase departure from ideal behavior. The data are shown to be reliable by both point and direct tests for thermodynamic consistency.

Vapor−Liquid Equilibrium for Binary System of 1-Propanethiol, Thiophene, and Diethyl Sulfide with Toluene at 90.03 kPa

Isobaric vapor−liquid equilibrium (VLE) for three systems with different organic sulfur compounds (1-propanethiol + toluene, thiophene + toluene, and diethyl sulfide + toluene) were measured at 90.03 kPa with a circulation still. The experimental results were compared with original UNIFAC, UNIFAC-Dortmund, and COSMO-RS predictive models. All systems showed nearly ideal behavior. VLE data sets measured passed the point consistency test.