Vapor-liquid Equilibrium Behavior Research Articles

Isobaric vapor–liquid equilibria of binary system ethyl acetate + ethyl benzene + lithium bromide

The isobaric vapor–liquid equilibrium (VLE) behaviors for binary system, ethyl acetate + ethyl benzene, and ethyl acetate + ethyl benzene + LiBr (at saturation) were studied at the local ambient pressure (707 ± 1 mmHg). Equilibrium still was used where both liquid and vapor were continuously circulated. The experimental results showed that salt-free ethyl acetate + ethyl benzene system does not form an azeotrope point. The experimental results for ethyl acetate + ethyl benzene system were in a very good agreement with the predicted results using UNIFAC, UNIQUAC, NRTL, and Wilson models. Adding LiBr, as a salt, did show slight effects on the VLE behavior of ethyl acetate + ethyl benzene system.

Vapour–liquid equilibrium measurements and modelling for the ternary system (water + 2-propanol + 1-butyl-3-methylimidazolium acetate)

Vapour–liquid equilibrium (VLE) data were measured for the ternary mixtures of water (1) + 2-propanol (2) + 1-butyl-3-methylimidazolium acetate ([bmim][OAc]) (3). Complete T, x and y data were obtained in a relatively wide range of ionic liquid (IL) mass fractions up to 0.8. The data were correlated by means of NRTL and eNRTL equations with satisfactory results. Using the eNRTL equation, the ternary VLE behaviour was also modelled through correlation of two data sets, in which the mole fraction of 2-propanol on IL-free basis is respectively at 0.1 and 0.98. In this way, the six data sets were reproduced satisfactorily, with root mean square deviations of 1.06 K for temperature and 0.0098 for vapour-phase mole fractions. Owing to the regular distribution of the experimental data, good agreement between experiment and calculation was graphically presented. Effect of the IL on the VLE behaviour of the volatile components was also illustrated.

Ebulliometric Determination and Prediction of Vapor–Liquid Equilibria for Binary Mixtures of Ethanol and Ethyl Hexanoate

The objective of this study is to measure vapor–liquid equilibria (VLE) data for an ethanol + fatty acid ethyl ester (FAEE) system. VLE data for the binary system ethanol + ethyl hexanoate were determined at pressures of (40.00 to 101.3) kPa using an ebulliometer, which could compensate for vapor hold-up. The hold-up compensable ebulliometer was designed for this study, and the experimental apparatus and procedure were verified by measuring the VLE data for ethanol + p-xylene at pressures of (40.00 to 101.3) kPa. The densities at 298.15 K for pure components investigated in this study were also measured by a densimeter. The experimental VLE data of the two binary mixtures, ethanol + p-xylene and ethanol + ethyl hexanoate, were represented by the Wilson and nonrandom two-liquid (NRTL) models. The analytical solutions of groups (ASOG) and modified universal functional activity coefficient (UNIFAC, Dortmund) group contribution models were also used to predict the VLE behavior of these binary mixtures. The VL...

Ebulliometric determination and prediction of (vapor + liquid) equilibria for binary and ternary mixtures containing alcohols (C 1–C 4) and dimethyl carbonate

(Vapor + liquid) equilibrium (VLE) data for a ternary mixture, namely {methanol + propan-1-ol + dimethyl carbonate (DMC)}, and four binary mixtures, namely an {alcohol (C 3 or C 4) + DMC}, containing the binary constituent mixtures of the ternary mixture, were measured at p = (40.00 to 93.32) kPa using a modified Swietoslawski-type ebulliometer. The experimental data for the binary systems were correlated using the Wilson model. The Wilson model was also applied to the ternary system to predict the VLE behavior using parameters from the binary mixtures. The modified UNIFAC (Dortmund) model was also tested for the predictions of the VLE behavior of the binary and ternary mixtures. In addition, the experimental VLE data for the ternary and constituent binary mixtures were correlated using the extended Redlich–Kister (ERK) model, which can completely represent the azeotropic points. For the ternary system, a comparison of the experimental and the predicted or correlated boiling points obtained using the Wilson and ERK models showed that the ERK model is more accurate. The valley line, i.e., the curve which divides the patterns of vapor–liquid tie lines, was found in the (methanol + propan-1-ol + DMC) system. This valley line could be represented by the ERK model. Finally, the composition profile for simple distillation of this ternary mixture was obtained by analysis of the residue curves from the estimated Wilson parameters of the constituent binary mixtures.

Vapor-Liquid Equilibrium Measurements and Modeling for Ternary System Water + Ethanol + 1-Butyl-3-methylimidazolium Acetate

Vapor-liquid equilibrium (VLE) data were measured for ternary system water + ethanol + 1-butyl-3-methylimidazolium acetate ([bmim][OAc]), in a relatively wide range of ionic liquid (IL) mass fractions up to 0.8. Six sets of complete T- x- y data were obtained, in which the mole fraction of ethanol on IL-free basis was fixed separately at 0.1, 0.2, 0.4, 0.6, 0.8, and approximate 0.98. The non-random-two-liquid (NRTL) and electrolyte non-random-two-liquid (eNRTL) equations were used for correlation, showing similar deviations. The ternary VLE was also modeled with the correlation from two data sets, with the mole fractions of ethanol on IL-free basis being 0.1 and approximate 0.98. The VLE data were also reproduced satisfactorily. With the eNRTL model, the root-mean-square deviation for temperature is 0.79 K and that for vapor-phase mole fraction is 0.0094. The calculations are in good agreement with experimental data. The effect of the IL on the VLE behavior of the volatile components is also illustrated.

Correction toP, ρ,TMeasurements and Isobaric Vapor–Liquid Equilibria of the 1,3,3-Trimethyl-2-oxabicycle[2,2,2]octane + Propan-1-ol Mixture: Cubic and Statistical Associating Fluid Theory-Based Equation of State Analysis

Densities measured at pressures from (20 to 40) MPa and the temperatures (283.15, 298.15, 313.15, and 328.15) K and isobaric (vapor + liquid) equilibrium (VLE) at pressures of (33.33, 66.66, and 101.33) kPa are reported for the mixture {1,8-cineole(1,3,3-trimethyl-2-oxabicycle[2,2,2]octane) + propan-1-ol} in the whole composition range. Excess molar volumes, isobaric thermal expansions, and isothermal compressibilities were calculated from the density data. VLE data were correlated by means of three activity coefficient models [Wilson, nonrandom two-liquid (NRTL), and universal quasichemical activity coefficient (UNIQUAC)], and their thermodynamic consistency was determined. Four equations of state (EOS), namely, the Peng−Robinson, the Patel−Teja, statistical associating fluid theory (SAFT), and perturbed-chain statistical associating fluid theory (PC-SAFT), were used first to predict (interaction parameters, kij, equal to zero) both the density and the VLE behavior of the system and second to correlate t...

P, ρ, T Measurements and Isobaric Vapor−Liquid−Equilibria of the 1,3,3-Trimethyl-2-oxabicycle[2,2,2]octane + Propan-1-ol Mixture: Cubic and Statistical Associating Fluid Theory-Based Equation of State Analysis

Densities measured at pressures from (20 to 40) MPa and the temperatures (283.15, 298.15, 313.15, and 328.15) K and isobaric (vapor + liquid) equilibrium (VLE) at pressures of (33.33, 66.66, and 101.33) kPa are reported for the mixture {1,8-cineole(1,3,3-trimethyl-2-oxabicycle[2,2,2]octane) + propan-1-ol} in the whole composition range. Excess molar volumes, isobaric thermal expansions, and isothermal compressibilities were calculated from the density data. VLE data were correlated by means of three activity coefficient models [Wilson, nonrandom two-liquid (NRTL), and universal quasichemical activity coefficient (UNIQUAC)], and their thermodynamic consistency was determined. Four equations of state (EOS), namely, the Peng−Robinson, the Patel−Teja, statistical associating fluid theory (SAFT), and perturbed-chain statistical associating fluid theory (PC-SAFT), were used first to predict (interaction parameters, kij, equal to zero) both the density and the VLE behavior of the system and second to correlate the VLE by adjustment of the interaction parameters for each EOS.

Generalized LIQUAC model for the single‐ and mixed‐solvent strong electrolyte systems

AbstractA generalized strong electrolyte LIQUAC model is presented to describe the vapor–liquid equilibria, osmotic coefficients, mean ion activity coefficients, and solid–liquid equilibria for the single‐ and mixed‐solvent electrolyte systems over the entire concentration range from infinite dilution to saturated solutions. An appropriate reference state for the ions was first applied to test the capability of the model in simultaneously describing the mean ion activity coefficients and the solubility of a salt in a binary solvent mixture. The influence of salt on the vapor–liquid equilibrium behavior is predicted with the new correlated parameters. The generalized activity coefficient formulations are presented through the investigation of thermodynamic properties and phase phenomena in the single‐ and mixed‐solvent electrolyte systems. This work is a continuous study for the LIQUAC activity coefficient model. A reliable representation of the single‐ and mixed‐solvent salt solutions is obtained. © 2010 American Institute of Chemical Engineers AIChE J, 2011

Experimental Measurement and Modeling of Vapor−Liquid Equilibrium for the Ternary System Water + Ethanol + 1-Butyl-3-methylimidazolium Chloride

Vapor−liquid equilibrium (VLE) data were measured for the ternary system water (1) + ethanol (2) + 1-butyl-3-methylimidazolium chloride ([bmim]Cl) (3). Complete T, x, and y data were obtained in a relatively wide range of ionic liquid (IL) mass fractions up to 0.8 and in a relatively complete composition range for the volatile binary pair. The nonrandom two-liquid (NRTL) equation was used for correlation and was revealed to be adequate for the ternary system in the experimental composition range. The ternary VLE behavior was also modeled by the correlation of two data sets, in which the ethanol mole fraction on IL-free basis is respectively at 0.1 and 0.98. In this way, the six data sets were reproduced satisfactorily, with root-mean-square deviations of 0.40 K for temperature and 0.0070 for vapor-phase mole fractions. Owing to the regular distribution of the experimental data, a good agreement between the experiment and the calculation was graphically presented. The effect of the IL on the VLE behavior o...

Measurement and Correlation of Vapor−Liquid Equilibrium for the Carbon Dioxide + 1-Butoxy Butane System

In this paper, 1-butoxy butane was proposed as a novel absorbent for carbon dioxide capturing from the process gas stream with rich carbon dioxide, and the feasibility for further research and development was investigated through the study on the vapor−liquid equilibrium (VLE) for the carbon dioxide + 1-butoxy butane system. The VLE measurements were carried out with a set of high pressure devices connected online to a gas chromatograph under a range from (263.15 to 309.15) K and (0.5 to 3.0) MPa. The experimental results were given with expanded uncertainties, which were δ 0.03 K and δ 0.006 MPa. Then, on the basis of the Peng−Robinson (PR) equation of state (EoS), an isothermal correlation for experimental data and the interaction parameter kij was obtained. The average liquid absolute deviation is 0.0159, and the average vapor absolute deviation is 0.0025. It proves the validity to use the PR EoS for describing the VLE behavior for 1-butoxy butane + carbon dioxide system.

Experimental Measurement and Modeling of Vapor−Liquid Equilibrium for Ternary Systems Containing Ionic Liquids: A Case Study for the System Water + Ethanol + 1-Hexyl-3-methylimidazolium Chloride

Vapor−liquid equilibrium (VLE) data were measured for the ternary system water (1) + ethanol (2) + 1-hexyl-3-methylimidazolium chloride ([hmim]Cl) (3) at p = 100 kPa. Six sets of complete T, x, y data were reported. While the mole fraction of ethanol on an ionic liquid (IL)-free basis was fixed, respectively, at 0.1, 0.2, 0.4, 0.6, 0.8, and 0.98, measurements were performed in a way in which the IL mass fraction varied from 0.8 to 0.1, in an interval of 0.1. The NRTL equation was used for correlation and was revealed as adequate for the ternary system in the experimental composition range. The quality of correlation appeared to be sensitive to the parameters used for water + ethanol. The ternary VLE behavior was also modeled by correlation of two data sets, in which the ethanol mole fraction on an IL-free basis is, respectively, at 0.1 and 0.98. In this way, the six data sets were reproduced satisfactorily, with root-mean-square deviations of 0.49 K for temperature and 0.0042 for vapor phase mole fraction. Owing to the regular distribution of the experimental compositions, the feasibility of the correlation−prediction procedure was graphically presented, and in some sense visualized, in terms of relative volatility, activity coefficient, and bubble temperature, showing good agreement between experiment and calculation.

Steady-state and dynamic modeling of commercial bulk polypropylene process of Hypol technology

Both steady-state and dynamic models for the commercial bulk polypropylene process of HYPOL technology were developed by using fundamental chemical engineering principles and advanced software tools, Polymers Plus and Aspen Dynamics. The models consider the important issues of physical property and thermodynamic model selections, catalyst characterization, and reactor model, in addition to the traditional Ziegler–Natta polymerization kinetics. The performance of equilibrium-stage modeling was examined using the perturbed-chain statistical associating fluid theory (PC-SAFT) equation of state and a pre-built reactor model in Polymers Plus. The detection of non-equilibrium behavior for the liquid-phase reactor leads to a novel reactor model suggested in this work, wherein the vapor–liquid equilibrium behavior was separated from polymerization behavior. Besides, the traditional Ziegler–Natta polymerization system was incorporated from single-site to multi-site model by fitting the actual data sourced from open reports and certain plant data. Furthermore, we validated the models using the plant data and demonstrated the application of our dynamic model by simulating a grade change.

Vapor–Liquid Equilibrium Behaviors of 5-Methyl-2-(1-methylethyl)phenol in Alcohol

Vapor–liquid equilibrium behaviors of scent solid, 5-methyl-2-(1-methylethyl)phenol, in methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, or 2-methyl-1-propanol were measured at atmospheric pressure in the dilute composition range of 5-methyl-2-(1-methylethyl)phenol with a recirculation still. Equilibrium compositions were determined with an ultraviolet spectrometer. The activity coefficients of 5-methyl-2-(1-methylethyl)phenol at infinite dilution in alcohol were less than unity.

THERMODYNAMICS OF ALKANOLAMINE + WATER SYSTEM

Design of gas treating processes requires knowledge of the vapor-liquid equilibrium behavior of the (acid gas + aqueous alkanolamine) system. The present study is focused on thermodynamics and associated nonideal behavior of binary MEA + H2O, DEA + H2O, and MDEA + H2O systems, which is required to predict the vapor-liquid equilibrium of acid gases such as CO2 and H2S over aqueous alkanolamine solutions. Determination of binary interaction parameters and analytical prediction of infinite dilution activity coefficient, heats of solution at infinite dilution, the excess Gibbs free energy, and excess enthalpy for nonideal alkanolamine-water systems are the objectives of this study.

Vapor−Liquid Equilibria of the Perfluoromethyl Vinyl Ether and Chlorotrifluoroethylene System

Isothermal vapor−liquid equilibrium (VLE) data for the perfluoromethyl vinyl ether + chlorotrifluoroethylene system were measured in a vapor−liquid equilibrium still with a vapor recycling system at four temperatures from (267.67 to 282.62) K. The uncertainty of the temperature was ± 0.01 K, and the accuracy of the pressure was ± 0.05 %. The experimental data were correlated with the NRTL equation and the Wilson equation. The calculated results agree well with the experimental data. Azeotropic VLE behaviors can be observed at certain compositions from the experimental data.

QSPR generalization of activity coefficient models for predicting vapor–liquid equilibrium behavior

Multiphase equilibrium calculations are an integral part of the design and optimization of numerous chemical processes. Several accurate experimental techniques have been developed for measuring phase equilibrium data. However, experimental techniques are time consuming and costly. Hence, a need exists for reliable thermodynamic models capable of giving a priori predictions of the phase behavior of diverse systems in the absence of experimental data. Quantitative structure–property relationship (QSPR) modeling has the potential to provide reliable property estimates based on detailed chemical structure information. Although current QSPR models have been successful in providing reliable structure-based property predictions, they have been limited to estimating properties at a single temperature. Further, little work has been done on QSPR models for mixtures. In this work, we generalize excess Gibbs energy ( G E) models, such as the non-random two-liquid (NRTL) and universal quasi-chemical (UNIQUAC) models by developing structure-based model parameters using QSPR modeling. Specifically, integrated G E-QSPR models capable of a priori prediction of the vapor–liquid equilibrium (VLE) phase behavior are developed. These NRTL-QSPR and UNIQAC-QSPR model generalizations produced VLE predictions for a wide variety of systems (332 binaries) with an average absolute percent deviation (%AAD) of approximately 5%, which is about twice that from direct parameter regressions. In addition, our generalization strategy was successful in reducing the effects of the inherent parameter inter-correlation in the NRTL and the UNIQUAC model regressions.

High-pressure Vapor-Liquid Equilibrium Studies for DME-CO 2-CH 3OH and DME-CO 2-C 2H 5OH Systems

In this study, the Gibbs-Duhem equation was applied to make the thermodynamic consistency test and thermodynamic model estimation for systems of CO 2-DME (dimethyl ether), DME-CH 3OH, CO 2-CH 3OH and C 2H 5OH systems on the basis of the vapor-liquid equilibrium (VLE) experimental data in published reports. And the NRTL binary interaction parameters of the systems mentioned above were regressed by the VLE data and were subjected to a thermodynamic consistency test because the study showed that PR-NRTL model combination was appropriate for the four systems mentioned above. The regressed binary interaction parameters were used to estimate the VLE for DME-CO 2-CH 3OH at temperatures of 313.15K and 333.15K, and the estimated result was coincident with the experimental data. On the basis of the predicted VLE data for systems of DME-CO 2-CH 3OH and DME-DME-CO 2-C 2H 5OH, the VLE behaviors of the two systems were studied by the phase diagrams of these two ternary systems, with the forms of both the two dimensional and three dimensional phase diagrams, respectively.

Vapor−Liquid Equilibrium Data for the Ethane + Trifluoromethane System at Temperatures from (188.31 to 243.76) K

Isothermal vapor−liquid equilibrium (VLE) data for ethane (R170) + trifluoromethane (R23) system were measured at six temperatures from (188.31 to 243.76) K and pressures up to 1.62 MPa. The measurements were performed with a recirculation method. The experimental data were correlated with the Soave−Redlich−Kwong equation of state using the Huron−Vidal mixing rule and the NRTL model. The calculated results agree well with the experimental data. Azeotropic VLE behaviors can be observed at certain compositions from the experimental and calculated data.

Vapor-liquid equilibrium and critical behavior of the square-well fluid of variable range: A theoretical study

The vapor-liquid phase behavior and the critical behavior of the square-well (SW) fluid are investigated as a function of the interaction range, lambdain [1.25, 3], by means of the self-consistent Ornstein-Zernike approximation (SCOZA) and analytical equations of state based on a perturbation theory [A. L. Benavides and F. del Rio, Mol. Phys. 68, 983 (1989); A. Gil-Villegas, F. del Rio, and A. L. Benavides, Fluid Phase Equilib. 119, 97 (1996)]. For this purpose the SCOZA, which has been restricted up to now to a few model systems, has been generalized to hard-core systems with arbitrary interaction potentials requiring a fully numerical solution of an integro-partial differential equation. Both approaches, in general, describe well the liquid-vapor phase diagram of the square-well fluid when compared with simulation data. SCOZA yields very precise predictions for the coexistence curves in the case of long ranged SW interaction (lambda>1.5), and the perturbation theory is able to predict the binodal curves and the saturated pressures, for all interaction ranges considered if one stays away from the critical region. In all cases, the SCOZA gives very good predictions for the critical temperatures and the critical pressures, while the perturbation theory approach tends to slightly overestimate these quantities. Furthermore, we propose analytical expressions for the critical temperatures and pressures as a function of the square-well range.

Vapour–liquid equilibrium of carboxylic acid systems: Propionic acid + valeric acid and isobutyric acid + valeric acid

The vapour–liquid equilibrium behaviour of two carboxylic acid systems was studied; viz. propionic acid (1)–valeric acid (2) and isobutyric acid (1)–valeric acid (2). For each system, a single isobar at 20 kPa and three isotherms at 393.15, 403.15 and 413.15 K, respectively, were measured. Liquid-phase activity coefficients were determined using a procedure based on the chemical theory for the vapour phase similar to those of Tamir and Wisniak [A. Tamir, J. Wisniak, Chem. Eng. Sci. 30 (1975) 335–342], Marek [J. Marek, Coll. Czech. Chem. Commun. 20 (1955) 1490–1502], and Marek and Standart [J. Marek, G. Standart, Coll. Czech. Chem. Commun. 19 (1954) 1074–1084]. The experimental activity coefficients, γ A and γ B, proved difficult to correlate using the commonly utilized Gibbs excess energy models, with best results obtained from the T– K Wilson equation. Area tests for thermodynamic consistency (strongly dependent on the chemical equilibrium constants, K) showed greater apparent consistency for the isobutyric acid–valeric acid system than for the propionic acid–valeric acid system. This is attributed to the possible formation of small amounts of propionic acid trimer. The vapour-phase correction factors, Φ i , showed considerable departure from unity, confirming the highly non-ideal nature of the vapour-phase for the mixtures studied. An efficient bubble-point calculation routine is proposed that yields system pressure and vapour-phase compositions (at any arbitrary liquid composition and temperature) of sufficient accuracy for distillation equipment design.