VLE Data Research Articles

Study of the LLE, VLE, and VLLE of the Ternary System Water + 1-Butanol + Isoamyl Alcohol at 101.3 kPa

The liquid–liquid equilibrium of the water + 1-butanol + isoamyl alcohol system at 303.15 and 313.15 K has been determined experimentally. The UNIQUAC, NRTL, and UNIFAC models have been employed to correlate and predict liquid–liquid equilibria (LLE) and compare them with the experimental data. Additionally, the vapor–liquid and vapor–liquid–liquid equilibria (VLE and VLLE, respectively) of this system have been determined using a modified Fischer LABODEST still. The data obtained have been used to correlate and obtain the binary interaction parameters for UNIQUAC and NRTL. The validity of the models to reproduce the VLE and VLLE data has been analyzed.

Wagner Equation Predicting Entire Curve for Pure Fluids from Limited VLE Data: Critical and Normal Boiling Points & Acentric Factor

Wagner constants are estimated from VLE predictions based solely on the critical and normal boiling points, and acentric factor. The predictions come from the standard forms of 1) Riedel and 2) Ambrose-Walton, 3) a modified Riedel equation resulting from forcing the value of K to provide zero error at the reduced temperature of 0.7, and 4) a modified Ambrose-Walton equation resulting from using a pseudo acentric factor that provides zero error at the normal boiling point. Reduced vapor pressure values obtained using these Wagner constants are compared to those generated by using literature-reported Wagner constants that are applicable for the entire two-phase VLE curve for 72 species. It is shown that the Wagner equation parameterized using VLE predictions from such correlations can provide better accuracy than the underlying source correlations themselves, and it can exhibit less error than a parameterization using a limited interval of experimental data.

Refractive Index and Vapor–Liquid Equilibrium Data for the Binary Systems of Anisole with Xylene Isomers at 93.13 kPa

Phase equilibrium behavior of binary systems of anisole with xylene isomers was analyzed experimentally. An apparatus which establishes equilibrium conditions through continuous circulation of equilibrium vapor condensate and equilibrium liquid was used. Experimental data comprising refractive indices of binary mixtures, equilibrium compositions of vapor and liquid, and equilibrium temperature are reported for all binary systems. Thermodynamic consistency of vapor–liquid equilibrium data was established for using the Herington, Van Ness and absolute mean deviation tests. Interaction parameters of activity coefficient models, Wilson, nonrandom two liquid, and universal quasichemical, which are important for accounting nonideal behavior in process modeling, are also estimated through regression of the respective binary VLE data. Although VLE data shows that binary systems are nonazeotropic in nature, a pinch in the T–x,y plot indicates that separation of all binary system using distillation may need a signi...

Vapor-liquid equilibrium in the binary and ternary systems containing ethyl propionate, ethanol and alkane at 101.3 kPa

The vapor-liquid equilibria at 101.3 kPa of seven binary systems: ethanol (1) + cyclohexane (2), ethanol (1) + n-hexane (2), ethanol (1) + n-octane (2), cyclohexane (1) + ethyl propionate (2), n-hexane (1) + ethyl propionate (2), n-octane (1) + ethyl propionate (2) and ethanol (1) + ethyl propionate (2), three ternary systems: ethanol (1) + cyclohexane (2) + ethyl propionate (3), ethanol (1) + n-hexane (2) + ethyl propionate (3) and ethanol (1) + n-octane (2) + ethyl propionate (3) at temperatures from 332.15 to 396.85 K were studied, all the binary VLE data passed the Herington test. Wilson, NRTL and UNIQUAC models were used to correlate experimental VLE data of the all systems to obtain interaction parameters through the MATLAB software and the experimental values were compared with the regression results. The Wilson and NRTL models reproduced the experimental values very well. Ternary VLE behavior were successfully predicted by the correlated binary parameters. The VLE data for the binary and ternary systems predicted by the correlated interaction parameters were in good agreement with all the experimental data.

Vapor-liquid and liquid-liquid equilibrium modeling of systems involving ethanol, water, and ethyl valerate (valeric acid) using the PC-SAFT equation of state

Valeric biofuels are renewable and environmental friendly fuels whose production avoids the competition with the food industry for edible oils since its route of production uses lignocellulose of residue from crops as raw material. After the reaction steps several purification operations are necessary for the valeric biofuels to meet purity standards. Therefore, it is of utter importance the knowledge of both liquid-liquid (LLE) and vapor-liquid (VLE) equilibrium behavior of species present in the process, such as ethyl valerate, valeric acid, ethanol and water. In this sense, the objective of this work is to provide a general overview for the phase equilibria of the system aforementioned using experimental data collected as background for the thermodynamic modeling. Experimental data concerning to LLE were evaluated at local atmospheric pressure (around 90.9 kPa) and 293.15 K and 318.15 K, while VLE data were collected at several different controlled pressures, ranging from approximately 7 kPa to local atmospheric pressure (around 91 kPa). UNIFAC and PC-SAFT (Perturbed Chain form of the Statistical Associating Fluid Theory) were used to perform the thermodynamic modeling. The results obtained in this work are helpful to prove the importance of carefully evaluate the interactions between the molecules present in the system. Otherwise, the design of unit operations could underestimate the number of stages required for the purification, causing the products to not reach purity specifications.

Acetonitrile Dehydration via Extractive Distillation Using Low Transition Temperature Mixtures as Entrainers

Low transition temperature mixtures (LTTMs) are versatile alternatives to ILs. They share many properties with ILs, so they become a suitable choice for entrainers in extractive distillation processes. In this study, glycolic acid and choline chloride in a 3:1 molar ratio (GC3:1) were synthesized and explored as entrainers for separation of acetonitrile + water azeotropic mixtures. Isobaric vapor–liquid equilibrium data for the pseudobinary mixtures of ACN + GC3:1 and water + GC3:1 were measured at atmospheric pressure (101.32 kPa). For the pseudoternary system ACN + water + GC3:1, also VLE data were measured at different GC3:1 mole fractions of 0.05, 0.1, and 0.15. The thermodynamic modeling of these systems was performed using the nonrandom two-liquid (NRTL) model. Furthermore, a study was conducted for synthesized GC3:1 recoverability. A good agreement were found between experimental data and predicted values for these systems. Results showed that LTTM (GC3:1) eliminated the acetonitrile + water azeotr...

Separation of ethylbenzene and p-xylene using extractive distillation with p-dinitrobenzene

Though p-xylene derived from naphtha reformate is in high demand as a raw material in the production of polyesters and polyethylene terephthalates, its separation from the FCC reformate is not easy due to close boiling points among the components in the reformate. When a proper solvent for the p-xylene separation is available, an extractive distillation can be applied in the separation. Currently the separation utilizes an adsorption process requiring a large amount of costly adsorbent and a desorption process followed by distillation. In the proposed extractive distillation here, p-dinitrobenzene has been utilized to improve the separation of p-xylene from its ethylbenzene mixture. The VLE data of the ternary mixture estimated with the UNIFAC were compared to those computed from molecular simulation to show their reliability. An extractive distillation and solvent recovery were applied to obtain 99.6% purity p-xylene with 99.1% recovery. The economics of the proposed process demonstrates its comparability to the existing Parex process.

Thermodynamic modeling of methane hydrate formation in the presence of imidazolium-based ionic liquids using two-step hydrate formation theory and CPA EoS

In this study, thermodynamic modeling is performed to predict the P-T equilibrium conditions of methane gas hydrate formation in presence of ionic liquids. The imidazolium-based ionic liquids including [EMIM][HSO4], [EMIM][EtSO4], [BMIM][BF4], [OH-EMIM][BF4], [BMIM][Cl] and [BMIM][Br] are modeled through two-step hydrate formation theory of Chen and Guo coupled with CPA EoS for calculating the fugacities of species in liquid and gas phase. The CPA pure component parameters for ionic liquids and also the majority of binary interaction parameters are adjusted using the liquid density and binary VLE data, respectively. The thermodynamic modeling is carried out in the presence of 0.1 weight fractions of all the studied imidazolium based ionic liquids. Moreover, the effect of three various concentrations of [BMIM][BF4] on the P-T equilibrium diagram of methane hydrate are predicted at 0.1, 0.15 and 0.20 weight fractions of this ionic liquid. The results indicate that the CPA EoS can satisfactorily model the phase behavior of aqueous solutions of imidazolium based ionic liquids considering 2B scheme for the association term. In addition, the results indicate good predictions of the proposed model for methane hydrate equilibrium conditions in the presence of imidazolium-based studied ionic liquids including concentration changes such that the absolute average deviations of methane hydrate formation pressures is obtained below 4.2%.

Isobaric Vapor–Liquid Equilibrium for Binary and Ternary Systems of tert-Butanol + tert-Butyl Acetate + Chlorobenzene at 101.33 kPa

Isobaric vapor–liquid equilibria of tert-butanol + chlorobenzene and tert-butyl acetate + chlorobenzene binary systems and the tert-butanol + tert-butyl acetate + chlorobenzene ternary system at 101.33 kPa were measured using a circulation VLE still. The data of binary systems passed the thermodynamic consistency test of the Herington method and the Van Ness point test, and the experimental data of the ternary system also passed the Wisniak consistency test. These binary systems’ VLE data were fitted by the Wilson, nonrandom two-liquid (NRTL), and universal quasichemical (UNIQUAC) activity coefficient models with minor deviations. Furthermore, the obtained binary interaction parameters from the binary systems were used to predict the VLE behavior of the tert-butanol + tert-butyl acetate + chlorobenzene ternary system. The rmsd of vapor and the temperature between the experimental and predicted values for the ternary system were smaller than 0.0304 and 0.81K, respectively. The results indicated that the re...

Isobaric vapor-liquid equilibrium for methanol + methyl acetate with ionic liquids [OMMIM][Tf2N] and [OMIM][Tf2N] as entrainers at 101.3 kPa

The ionic liquids 1-methyl-3-octylimidazoliumbis (trifluoromethylsulfonyl)imide ([OMIM][Tf2N]) and 1,2-dimethyl-3-octylimidazolium bis(trifluoromethylsulfonyl)imide ([OMMIM][Tf2N]) were utilized as extractive distillation entrainers to make methanol as the volatile component for the separation of the azeotropic mixture of methanol and methyl acetate. Isobaric VLE data for the methanol (1) + methyl acetate (2) + [OMIM][Tf2N] and methanol (1) + methyl acetate (2) + [OMMIM][Tf2N] were measured at 101.3 kPa. The experimental data were correlated by NRTL model and UNIFAC model, and the NRTL model is more accurate. Both [OMIM][Tf2N] and [OMMIM][Tf2N] produce notable salting-out effects and make methanol as the volatile component, and the azeotropic point of methanol + methyl acetate can be eliminated if the mole fraction of [OMMIM][Tf2N] or [OMIM][Tf2N] is greater than 0.4. The mechanism of [OMMIM][Tf2N] and [OMIM][Tf2N] to improve the relative volatility of methanol to methyl acetate were investigated, and the salting-out effects of [OMMIM][Tf2N] is a little larger.

Isobaric Vapor–Liquid Equilibrium Data for Binary Systems of Anisole with Methyl Acetate, Ethyl Acetate, n-Propyl Acetate, and Isopropyl Acetate at 93.9 kPa

The present work reports experimental isobaric vapor–liquid equilibrium data at 93.9 kPa pressure using a dynamic recirculation still for four binary pairs of acetates with anisole. The suitability of the experimental data for modeling was established by performing the Herington area test, Van Ness test, and mean absolute deviation test. Binary interaction parameters necessary for process modeling were derived through the regression of the VLE data for Wilson, NRTL, and UNIQUAC activity coefficient models with a suitable objective function. VLE data in the form of T–x, y plots indicates no formation of azeotropes for all pairs.

Solubility of carbon dioxide in methanol from 213.15 K to 273.15 K: Measurement and modeling

The isothermal solubility data of carbon dioxide in methanol were measured at temperatures from 213.15 K to 273.15 K and pressures from vacuum up to 3.3450 MPa. The experimental method was a static analytical method with liquid sampling using a heated sample cylinder coupled to a gas chromatograph for analysis. The SRK EOS with the vdW one-fluid mixing rule was used to describe the equilibrium behavior of the vapor phase in the system for carbon dioxide + methanol binary mixture. The equilibrium behavior of the liquid phase was separately described by the NRTL and Wilson activity coefficient models. The measured data were separately correlated with SRK-vdW-NRTL and SRK-vdW-Wilson models. The calculated results indicate that the SRK-vdW-NRTL model predicts false liquid-liquid splitting, and the SRK-vdW-Wilson model not only matches well with the measured data but also predicts optimally VLE data of the system from 213.15 K to 273.15 K.

Experimental Vapor–Liquid Equilibrium Data for Binary Mixtures of Methyldiethanolamine in Water and Ethylene Glycol under Vacuum

Methyldiethanolamine (MDEA) is a widely used chemical in the natural gas processing industry as a solvent for CO2 and H2S capture and as a basic compound for pH stabilization corrosion control. During pH stabilization corrosion control, the removal of MDEA during the (mono)ethylene glycol (MEG) regeneration process may occur under vacuum conditions during reclamation in which the removal of salt cations is performed. Isobaric vapor–liquid equilibrium data for the binary MEG–MDEA system is presented at (20, 10 and 5) kPa and water–MDEA system at (40, 20, 10) kPa to simulate its behavior during MEG reclamation under vacuum. Vapor and liquid equilibrium concentrations of MDEA were measured using a combination of ion chromatography and refractive index. The generated experimental VLE data were correlated to the UNIQUAC, NRTL, and Wilson activity coefficient models, and the respective binary parameters were regressed.

Wagner Equation Predicting Entire Curve for Pure Fluids from Limited VLE Data: Error Dependency Upon Data Interval & Fully-Determined Case

The predictive error in vapor pressure of limited-data Wagner constants relative to that of entire-curve constants is studied for eleven data intervals. Good precision is assumed for data inputs, four digits in the mantissa of Ln Pv,r and five digits for Tr. An algebraic solution for the fully-determined case based on only four data points is used to estimate Wagner constants. Seventy-two species are used to assess the impact of the location of the two interior points and the location and width of the limited-data interval upon the error in predicted Pv,r due to data imprecision. Hydrogen, helium, R152a, and water are used to assess error due to Wagner imperfection and compare predictive capability of the algebraic fully-determined and regressed over-determined approaches. The results indicate that limited VLE data of good precision from reduced temperature intervals with a width ≥ 0.1 and a lower bound ≤ 0.6 can generally provide reasonable VLE predictions over the entire two-phase curve for pure substances, with average error of approximately 1%. It is shown that the algebraic, fully-determined solution presented is a viable tool for investigating the extensibility of limited-data Wagner constants.

Study on the use of an imidazolium-based acetate ionic liquid for CO2 capture from flue gas in absorber/stripper packed columns: Experimental and modeling

In the present work, 1-Ethyl-3-methylimidazolium acetate ([Emim][Ac]) ionic liquid (IL) has been considered for experimental and theoretical investigation of post-combustion carbon dioxide (CO2) capture from flue gas. The absorption and stripping of CO2 into [Emim][Ac] IL has been studied in a typical absorber/stripper system that randomly packed with Raschig ring at absorption pressures of 5–8 bar, absorption temperatures of 298.15–338.15 K and stripping conditions of 1.5 bar in temperature range 363.15–398.15 K. A mathematical model was developed for absorption and stripping processes based on mass transfer concepts and Peng–Robinson equation of state (PR EOS). The validity of the model was verified via comparison of the results achieved by the model with data taken from the experiments performed in this work and VLE data given in the literature. The impacts of parameters such as absorption/stripping pressure and temperature on the performance of CO2 capture, the sorbent flow rate and energy demand at selected operating conditions and specified CO2 capture rates were examined. The experimental tests showed that the recovered CO2 from the stripper column was pure. The results demonstrated that the energy requirement for the CO2 capture IL-based process is about 4890 kW or 2.75 GJ/t CO2. It was also found that the degradation rate of ion liquid is 3.78 wt.% of circulated IL. Using the enhancement factor obtained based on experimental results, the pseudo-first order reaction constant of the CO2 + [Emim][Ac] IL system was estimated. By fitting the kinetics data into Arrhenius equation, the activation energy and frequency factor of the reaction rate constant were found to be 10.317 kJ/mol and 1545 s−1, respectively.

Wagner equation predicting entire curve for pure fluids from limited VLE data: Critical point & four Antoine analytic points

Entire-curve Wagner analytics are treated as “true” or “best” values, and Antoine analytic values are used as surrogate experimental data. Limited-data Wagner constants are estimated from Antoine analytics for the fully-determined case for fifty-five species, from which reduced vapor pressures below and above the interval are predicted and compared with the entire-curve Wagner analytics to estimate the ability of limited VLE data to be used to accurately represent the entire two-phase curve. The Antoine intervals have a pressure range of 0.02–2 bars for most species, an average reduced temperature interval width of 0.20, and an average lower bound reduced temperature of 0.53. The Wagner constants estimated from Antoine analytics have an average entire-curve error of 4.8%, with the majority of the error occurring when extending down towards the triple point (9.55%), compared to 1.36% average error when extending up to the critical point. Such limited-data Wagner constants produce less predictive error for alcohols, while the semi-theoretical Riedel equation has the advantage for organic acids, and the empirical Ambrose-Walton equation produces less error for the remaining species. A comparison of Wagner and Antoine analytic values strictly over the Antoine interval indicates that disagreement of VLE data in the literature averages around 2% but varies considerably between species. Data disagreement is not found to be a strong indicator of predictive power of the limited-data Wagner constants; however, it is found to be a discriminator of performance relative to that of Riedel and Ambrose-Walton for some polar species.

CO2 + 3,7-dimethyl-1-octanol + 1-decanol: High pressure experimental phase equilibria data and thermodynamic modelling

New VLE data are presented for CO2 + 3,7-dimethyl-1-octanol (37DM1O) + 1-decanol (C10OH) at 35, 55 and 75 °C and pressures between 68 and 237 bar. Phase compositions were analysed using a static analytic apparatus with dual sampling and online chromatography. The mixture displays virtually no enhanced solubility, liquid curves remain convex throughout, and coexisting detached two-phase regions were not detected. CO2 can fractionate all measured 37DM1O:C10OH ratios though with limited efficacy, as highlighted by relative solubilities ranging from 1.1 to 1.5. RK-ASPEN, SR-POLAR, PR-BM and PC-SAFT correlations failed at 35 °C, the optimum fractionation temperature. At 55 and 75 °C, RK-ASPEN and SR-POLAR produced the smallest percentage average absolute deviations in equilibrium pressure of 4.0%, and RK-ASPEN was marginally superior at correlating vapour and liquid phase curves. At 35 °C and 187.5 bar, the 25:75 37DM1O:C10OH mixture passed through a density inversion and interesting images thereof are presented.

Separation of azeotrope (allyl alcohol + water): Isobaric vapour-liquid phase equilibrium measurements and extractive distillation

Abstract To separate the azeotrope of (allyl alcohol + water) by extractive distillation, N-methyl-2-pyrrolidone, N-methyl formamide and ethylene glycol were selected as extractive agents, and the isobaric VLE data for the binary systems of (allyl alcohol + N-methyl-2-pyrrolidone), (allyl alcohol + N-methyl formamide) and (allyl alcohol + ethylene glycol) were determined at 101.3 kPa by a modified Rose type recirculating still. The thermodynamic consistency of the experimental data was checked by the Herington, van Ness, infinite dilution, and pure component consistency method. Meanwhile, the experimental data were correlated by the NRTL, UNIQUAC and Wilson activity coefficient models, and the binary interaction parameters of the three models were regressed. All the correlated results by the NRTL, UNIQUAC, and Wilson models agreed well with the experimental data. Furthermore, the extractive distillation processes with the extractive agents were presented to separate the azeotrope of (allyl alcohol + water).

Measurement and Correlation of Vapor–Liquid Equilibrium for R124 (1-Chloro-1,2,2,2-Tetrafluoroethane)-NMP (N-Methyl-2-Pyrrolidone) and R124-DMF (N,N-Dimethylformamide) Mixtures

Vapor–liquid equilibrium data of binary working pairs play a crucial part in the research of absorption process and absorption refrigeration technology. In this paper, the VLE data of binary mixtures, R124-NMP and R124-DMF, were measured in a temperature range from 303.15 to 363.15 K, using a VLE measurement apparatus. The activity coefficient model of five-parameter nonrandom two liquid (NRTL) was selected to correlate all the VLE data acquired by measurement. The maximum relative deviation of the pressure between the measurement data and calculated data for R124-NMP and R124-DMF were 3.80% and 3.27% respectively, and the average relative deviation of the pressure were 1.25% and 1.17% respectively. The correlated results coincide well with the measurement data and show that the VLE characteristics of R124-NMP and R124-DMF mixtures have a negative deviation from Raoul’s law. Comparing three absorbents, DMF, DMAC and NMP, the activity coefficient of R124 in DMF is largest, that in DMAC is second, and that ...

CO2 + n-dodecane + 3,7-dimethyl-1-octanol: High pressure experimental phase equilibria data and thermodynamic modelling

New high pressure VLE data for the ternary mixture CO2+n-dodecane (nC12)+3,7-dimethyl-1-octanol (37DM1O) are presented. A static apparatus with online analysis was used to measure phase compositions at 35, 55 and 75°C, and pressures between 68 and 157bar. In the high-nC12 region the mixture displayed enhanced solubility, presenting as a pinched two phase band and s-shaped liquid phase curves. Relative solubility, an indicator of fractionation sharpness, increased with 37DM1O content and the 75:25 nC12:37DM1O mixture cannot be separated using CO2. RK-ASPEN, SR-POLAR, PR-BM and PC-SAFT models were evaluated for their ability to correlate these data. RK-ASPEN and PC-SAFT models provided the best and worst correlation of equilibrium pressures with respective percentage average absolute deviations of 3.1% and 8.5%. RK-ASPEN model was impressive in its ability to capture the co-solubility pinch seen for the 75:25 nC12:37DM1O mixture and the resultant s-shaped liquid phase complexity.