Isobaric Vapor-liquid Equilibrium Data Research Articles

Improving Estimates of the Crystallization Driving Force: Investigation into the Dependence on Temperature and Composition of Activity Coefficients in Solution

In this work the influence of temperature and composition on the activity coefficient in solution has been investigated, based on isothermal and isobaric vapor–liquid equilibrium data for 30 binary systems classified into four groups: water–organic, polar–polar, polar–nonpolar, and nonpolar–nonpolar systems. It is shown that under most conditions the temperature dependence of the activity coefficient is clearly weaker than the composition dependence. The analysis is extended to include solid–liquid solubility data of 15 binary systems of relatively large and complex organic molecules in organic solvents. Based on this, a novel approach to estimate the thermodynamic driving force of crystallization from solution is proposed. Rather than assuming that the activity coefficient ratio equals unity, it is shown that in most cases a more accurate assumption is to neglect only the temperature dependence of the activity coefficient. This allows the activity coefficient ratio to be estimated from solid–liquid equil...

Isobaric (vapor + liquid) equilibria for 2-methylthiophene with n-heptane, 2,2,4-trimethylpentane, n-nonane and n-decane at 90.00 kPa

Isobaric vapor-liquid equilibrium (VLE) data for the four systems n-heptane+2-methylthiophene, 2,2,4-trimethylpentane+2-methylthiophene, n-nonane+2-methylthiophene, n-decane+2-methylthiophene were measured at 90.00kPa with a modified Rose-Williams still. Gas chromatography equipped with a flame ionization detector was used to analyze composition of the samples from the vapor-liquid equilibrium systems. All the VLE measurements passed the thermodynamic consistent test using the Herington method and the Van Ness test. The azeotropic behavior was found in the 2,2,4-trimethylpentane+2-methylthiophene system. The experimental data were correlated by the Wilson and NRTL activity coefficient models and also compared with the original UNIFAC predictive model. The corresponding parameters for the three models were obtained. The results exhibited that the measured data got agree well with the calculated values using the Wilson, NRTL and original UNIFAC models.

Isobaric Vapor–Liquid Equilibrium for Two Binary Systems, (3-Methyl-1-butanol + 1,4-Butanediol) and (Hexylene Glycol + 1,4-Butanediol), at p = 40.0, 60.0, and 80.0 kPa

The isobaric vapor–liquid equilibrium data for the two binary systems of (3-methyl-1-butanol + 1,4-butanediol, hexylene glycol + 1,4-butanediol) at p = 40.0, 60.0, and 80.0 kPa were obtained by a improved Rose equilibrium still. The thermodynamic consistency of the VLE (vapor–liquid equilibrium) data was checked via the methods of the Herington area test and the Van Ness point test. In addition, the nonrandom two-liquid (NRTL), Wilson, and universal quasichemical (UNIQUAC) activity coefficient models were adopted to correlate the VLE data. The calculated values of the models mentioned above showed good agreements with the measured data.

Isobaric Vapor–Liquid Equilibrium for Two Binary Systems (n-Butanol + 1,4-Butanediol and γ-Butyrolactone + 1,4-Butanediol) at p = (30.0, 50.0, and 70.0) kPa

Isobaric vapor–liquid equilibrium (VLE) data for n-butanol + 1,4-butanediol and γ-butyrolactone + 1,4-butanediol have been experimentally determined by a improved Rose equilibrium still under pressures of 30.0, 50.0, and 70.0 kPa in this work. Additionally, the thermodynamic consistency tests of the experimental binary data were examined with the methods of the Herington area test and Van Ness point test, and then, three of the nonrandom activity coefficient models, which were two-liquid (NRTL), Wilson, as well as universal quasichemical (UNIQUAC), were selected to correlate the isobaric VLE data. All results demonstrated that the calculated values of the above-mentioned models achieved good agreement with the measured data.

Isobaric vapor-liquid equilibrium for methanol + methyl ethyl ketone + bis(trifluoromethylsulfonyl)imide-based ionic liquids at 101.3 kPa

Isobaric vapor-liquid equilibrium data for the ternary systems of methanol + methyl ethyl ketone (MEK) + 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([BMIM][NTf2]) and methanol + MEK + 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([HMIM][NTf2]) have been measured at 101.3 kPa using a modified Othmer still. The data obtained were correlated using NRTL model and fitted in well with it. The results showed that the addition of ionic liquids (ILs) into the azeotropic system caused a significant salting-in effect on MEK, thus increased the relative volatility of methanol to MEK and broke the azeotrope. And [HMIM][NTf2] has a stronger effect than [BMIM][NTf2]. The elimination of azeotropic phenomenon could be achieved when the mole fraction of ILs in the liquid phase was 0.05 (about 0.40 in mass fraction) or more. The effect of the ILs in this study was compared with that of some other ILs.

Investigation on Thermodynamics in Separation for Ethylene Glycol + Neopentyl Glycol System by Azeotropic Distillation

The isobaric vapor–liquid equilibrium (VLE) data for two binary systems of ethylene glycol (EG) + neopentyl glycol (NPG) and NPG + para-xylene (PX) have been measured under pressure of 101.3 kPa, respectively. The thermodynamic consistency of the experimental isobaric VLE data was tested by means of Herington area test. Meanwhile, the experimental isobaric VLE data have been satisfactorily correlated with Wilson, NRTL, and UNIQUAC models. A conventional azeotropic distillation process has been designed to achieve high-purity products based on preceding results. The product purities of EG and NPG can both achieved at 99.9 mol % with minimal total annual cost (TAC) through sequential iterative optimization procedure.

VAPOUR-LIQUID EQUILIBRIUM IN SYSTEMS WITH ISOBUTYL ACETATE, ACETIC ACID AND METHYL ETHYL KETONE

The experimental temperature dependence of the vapour pressures of isobutyl acetate, acetic acid and methyl ethyl ketone were determined, and isobaric vapour-liquid equilibrium data of binary systems of methyl ethyl ketone + isobutyl acetate and methyl ethyl ketone + acetic acid were obtained. The experimental data were processed using the Antoine and Riedel equations and the NRTL and Wilson local composition equations, respectively. Comparison of the experimental and calculated data confirmed the adequacy of the vapour-liquid equilibrium mathematical simulation.

Amino Acid Based Ionic Liquids as Additives for the Separation of an Acetonitrile and Water Azeotropic Mixture: COSMO-RS Prediction and Experimental Verification

The effects of 18 different amino acid based ionic liquids (AAILs) on the phase behavior of an acetonitrile + water mixture were predicted through the COSMO-RS method, indicating that all investigated AAILs could enhance the relative volatility of acetonitrile and break the azeotrope, in which 1-ethyl-3-methylimidazolium proline ([EMIM][Pro]) was the most effective at a given condition. Furthermore, the properties of the interaction energy, charge-density profiles, and excess enthalpy were obtained, showing that the stronger interactions between AAIL and water lead to improvement of the separation efficiency. To verify the feasibility, the isobaric vapor–liquid equilibrium data for two ternary mixtures of acetonitrile + water + [EMIM][Pro] and + 1-ethyl-3-methylimidazolium acetate ([EMIM][OAC]) at fixed IL mole fraction (0.05 and 0.10) were measured at atmospheric pressure. The experimental results show that the two ILs can effectively enhance the relative volatility of acetonitrile and break the azeotrop...

Separation of the ethanol/water azeotropic mixture using ionic liquids and deep eutectic solvents

Two ethanolamine-based ionic liquids (ILs) and two choline chloride-based deep eutectic solvents (DESs) were synthesized and evaluated as entrainers for the separation of the ethanol/water azeotropic mixture. Isobaric vapor-liquid equilibrium data of the ternary system ethanol/water/IL or DES were measured using an ebulliometer at 101.3kPa. The ILs examined were 2-hydroxy ethylammonium acetate and 2-hydroxy ethylammonium hexanoate, while the DESs were choline chloride:urea (1:2) and choline chloride:triethylene glycol (1:3). In all cases, an increase of the relative volatility and, consequently, a displacement of the azeotropic point was observed. Depending on the entrainer, concentrations of about 5.5–9% (w/w) were adequate for the complete elimination of the azeotrope. Recoverability and biodegradation tests were carried out for all ILs and DESs. DESs were found to be biodegradable, while ILs exhibited lower biodegradation capacity than DESs. Furthermore, analysis with 1H NMR proved that all entrainers can be recycled and reused. Finally, thermodynamic modeling of the ethanol/water/IL or DES mixtures was performed with the UNIQUAC and NRTL models. The results for both models were found to be in good agreement with the experimental data.

Experimental isobaric vapor–liquid equilibrium at sub-atmospheric and local atmospheric pressures, volumetric properties and molar refractivity from 293.15 to 313.15 K of water + triethylene glycol

Experimental isobaric vapor–liquid equilibrium data for the binary system of water+triethylene glycol were obtained at sub-atmospheric pressures of 53.33, 66.66, 79.99kPa and local atmospheric pressure of 95.99kPa over the entire composition range using a modified Sweitoslawsky-type ebulliometer. The experimental data was correlated using Wilson and NRTL models. Wilson model was found to better represent the calculation results. The measured densities and refractive indices over the entire composition range of water+triethylene glycol are reported from 293.15 to 313.15K at local atmospheric pressure of 95.99kPa. Excess molar volume, partial molar volume and deviations in molar refractivity were evaluated and fitted to the Redlich–Kister equation. Excess molar volumes were found to be negative at all temperatures and the deviation from ideality decreased with increase in temperature. Different mixing rules were also investigated for predicting the refractive indices of the binary mixture and are reported in terms of their average percentage deviation.

High pressure vapor–liquid equilibria of methyl acetate or ethyl acetate with 2-propanol at 1.5 MPa. Experimental data and predictions

Isobaric vapor–liquid equilibrium data for the binary systems methyl acetate+2-propanol and ethyl acetate+2-propanol at 1.5MPa were obtained. The data quality was verified by using the point-to-point test of Van Ness and the Fortran routine of Fredenslund et al., which was implemented to third virial coefficient using the method of Orbey and Vera. Experimental data satisfied the validation criterion of Fredenslund et al. The azeotropic point of ethyl acetate+2-propanol was not found at 1.5MPa. The ASOG low pressure group contribution models and different versions of UNIFAC were employed for the verification of high pressure vapor–liquid equilibrium data predictions. The ϕ–ϕ approach was applied by using the Peng–Robinson equation of state and employing quadratic mixing rules. The UNIFAC-Lyngby model returned good overall predictions; however the modeling for both systems was best when the Peng–Robinson equation of state was applied.

The Distillation Process Design for the Ternary System 1,2-Butanediol + 1,4-Butanediol + 2,3-Butanediol

The isobaric vapor-liquid equilibrium data for distillation have been measured for three binary systems of (1,2-butanediol(BD)+1,4-BD), (1,2-BD+2,3-BD), and (1,4-BD+2,3-BD) and for the ternary system of (1,2+BD+1,4-BD+2,3-BD) at 101.3 kPa. The thermodynamic properties of the vapor phase have been calculated with the Hayden-O’Connell equation in consideration of nonideality. The liquid activity coefficients have been satisfactorily correlated with the Wilson, NRTL and UNIQUAC models. The corresponding binary interaction parameters of the three models were calculated. Based on all the preceding results, a two-column distillation process was designed to obtain the required products with purity of 98% for industrial use.

Isobaric vapor–liquid equilibria for binary mixtures from methyl methanoate, dimethoxymethane and dimethyl carbonate at 101.33 kPa

New isobaric vapor–liquid equilibrium data were measured for the binary mixtures of dimethoxymethane+dimethyl carbonate, methyl methanoate+dimethyl carbonate and methyl methanoate+dimethoxymethane systems. The experimental data were correlated by some activity coefficient models and were reproduced by the model parameters in good agreements. No azeotropic point was observed for the three binary pairs. The observed phase behaviors of the binary mixtures were compared with those predicted by a group contribution method.

Measurement and Modeling for Isobaric Vapor–Liquid Equilibrium of Binary 1,3,5-Trichlorobenzene + 3,5-Dichloroaniline and 3-Chloroaniline + 3,5-Dichloroaniline Systems

The isobaric vapor–liquid equilibrium data for binary systems of 1,3,5-trichlorobenzene (1) + 3,5-dichloroaniline (2) and 3-chloroaniline (1) + 3,5-dichloroaniline (2) were measured experimentally under pressures of 20.00, 60.00 and 101.20 kPa using an inclined ebulliometer. Thermodynamic consistency of the vapor–liquid equilibrium data was tested by means of the Herington semiempirical method, and the isobaric vapor–liquid equilibrium data were correlated with three activity coefficient models, which were Wilson, NRTL and UNIQUAC. The energy interaction parameters were acquired by a nonlinear least-squares regression method for the three thermodynamic models. Results indicate that all the three activity coefficient models can describe the measured isobaric vapor–liquid data acceptably. The isobaric vapor–liquid equilibrium data determined in the present work are important in the design and operation for purification of 3,5-dichloroaniline by distillation.

Approach to the 1-propanol dehydration using an extractive distillation process with ethylene glycol

The extractive distillation process exploits the capacity of some chemicals to alter the relative volatility between the components of a mixture. In this way, a third component (called entrainer) may be added to an azeotropic binary mixture to break the azeotrope.This paper discusses the potential use of ethylene glycol as entrainer in a 1-propanol dehydration process by extractive distillation. First, the present work focuses on the acquisition of isobaric vapor–liquid equilibrium data of the ternary system 1-propanol+water+ethylene glycol system and the binaries systems 1-propanol+ethylene glycol and water+ethylene glycol. All measurements were done at 101.3kPa.The experimental data were correlated by the Wilson, NRTL and UNIQUAC local composition models in order to obtain a set of thermodynamic parameters. Finally, the extractive distillation process was simulated and later economically optimized with the aid of commercial software (Aspen Hysys®) using the previously obtained parameters of the NRTL model.

Isobaric Vapor–Liquid Equilibrium for Two Binary Systems{Propane-1,2-diol + Ethane-1,2-diol and Propane-1,2-diol + Butane-1,2-diol} at p = (10.0, 20.0, and 40.0) kPa

Isobaric vapor–liquid equilibrium (VLE) data for the two binary systems of {propane-1,2-diol + ethane-1,2-diol and propane-1,2-diol + butane-1,2-diol} at p = (10.0, 20.0, and 40.0) kPa have been determined using a modified Rose–Williams still with continuous circulation of both vapor and liquid phases in this work. The thermodynamic consistency tests of the experimental VLE data were performed according to the methods of the Herington area test and Van Ness point test. The experimental isobaric VLE data were then correlated using the universal quasichemical (UNIQUAC), nonrandom two-liquid (NRTL), Margules, and Wilson activity coefficient models. Consequently, the calculation values showed good agreements with the experimental data measured in this study.

Isobaric Vapor–Liquid Equilibria for the Binary and Ternary Systems of Methanol, Epichlorohydrin, and Glycerol Dimethyl Ether at 101.3 kPa

Glycerol dimethyl ether (2,3-dimethoxy-1-propanol) is one kind of potential fuel additive that can be synthesized from methanol and epichlorohydrin with high selectivity. The isobaric vapor–liquid equilibrium data (VLE) for two binary systems, methanol (1) + epichlorohydrin (2) and methanol (1) + glycerol dimethyl ether (3) were measured in a modified Ellis recirculation still at 101.3 kPa. The VLE data were correlated using the nonrandom two-liquid (NRTL) and universal quasichemical activity coefficient (UNIQUAC) models, The calculated compositions and temperature by NRTL agree better with the experimental values than those calculated by UNIQUAC. The obtained model parameters of the binary systems are used to predict the VLE data for the ternary system.

Prediction of Thermodynamic Consistency of Vapour-liquid Equilibrium of a Two-Phase System in the Presence of the Salting-in and Salting-out Effects

Salt effect on vapour–liquid equilibrium (VLE) has been a subject of intense investigation from experimental and modelling perspectives since the salting-in and salting-out effects might eliminate the possibility of azeotrope formation at saturation. Nevertheless, thermodynamic consistency evaluation of data generated from this type of studies, accounting for non-idealities of one or two of the phases involved, is mandatory. In this communication, a primary evaluation of thermodynamic consistency under a non-ideal VLE situation of data generated for an ethanol–water system with and without the addition of inorganic potassium chloride (KCl) salt is presented. The equilibrium data (T-x-y diagram) for ethanol–water system is generated under isobaric conditions, with and without 2 and 4 g/L concentration levels of KCl. The isobaric VLE data of ethanol–water system saturated with KCl concentrations are correlated by means of a modified Raoult's law to predict the activity coefficient of the volatile components. Activity coefficients are evaluated using a state equation and fugacities as well. Both methodologies give identical activity coefficients, indicating that Raoult's law is a simple approach to calculate these parameters. Thermodynamic consistency of VLE data with and without the addition of KCl is validated from a simple but reliable strategy that makes use of the Gibbs–Duhem plot and Murthy's approach which avoids the use of enthalpy of mixing.

Experimental isobaric vapor–liquid equilibrium at atmospheric and sub-atmospheric pressures, excess molar volumes and deviations in molar refractivity from 293.15 K to 318.15 K of diisopropyl ether with methanol and isopropyl alcohol

Experimental isobaric vapor–liquid equilibrium data for the binary systems, diisopropyl ether+isopropyl alcohol and methanol+diisopropyl ether at the local atmospheric pressure of 94.79kPa and at sub-atmospheric pressures of (53.3, 66.7, 79.9) kPa were obtained over the entire composition range using a Sweitoslawsky-type ebulliometer. The experimental temperatures were compared with predictions made using Wilson, NRTL, UNIQUAC, UNIFAC, Peng–Robinson (PR) and Soave–Redlich–Kwong (SRK) equations of state (EoS) with Wong–Sandler (WS) mixing rules. Model parameters along with the deviations in temperature have been presented. Experimental temperatures were found to be in good agreement with the predicted values. NRTL model was found to represent the VLE behavior of these systems better than the other models used. Density and refractive indices of mixtures are reported from 293.15K to 318.5K.

Measurement and correlation of isobaric vapor-liquid equilibrium for the binary system of cyclopentane and tetrahydrofuran

Isobaric vapor-liquid equilibrium (VLE) data for the cyclopentane and tetrahydrofuran (THF) system were measured at 101.3 kPa by using an equilibrium still. Thermodynamic consistency of the experimental data was confirmed by means of the Herington method. The experimental data were correlated and calculated by the Margules, Van Laar and Wilson activity-coefficient models, respectively. The Wilson and Van Laar activity-coefficient models are better than the Margules activity-coefficient model based on the average absolute deviations of temperature and the vapor-phase composition. For the Wilson and Van Laar activity-coefficient models the average absolute deviations between the experimental and the calculated values were 0.24 K and 0.23 K for the boiling point, and 0.0040 for vapor-phase composition, respectively. These agree well with the experimental data. Therefore, it was shown that the Wilson and Van Laar activity-coefficient models satisfactorily correlate the experimental results of the cyclopentane and tetrahydrofuran system.