Modified UNIFAC Group Contribution Method Research Articles

Investigation of surface tension and surface properties of alkanolamine–alcohol mixtures at T = 313.15 K and P = 90.6 kPa

Alkanolamine compounds are especially useful in the adsorption of acid–gases from gas streams. In this work, surface tension for nine binary systems containing an alkanolamine (monoethanolamine (MEA), diethanolamine (DEA) and triethanolamine (TEA)) and a short chain alcohol (methanol, ethanol and isopropanol) were measured over the entire concentration range at 313.15 K and 90.6 kPa by means of the ring detachment method. From these data, the surface tension deviations were computed. The maximum deviation in nine systems was <1%. Then these surface tension data were correlated using Myers–Scott (MS) and Fu et al. (FLW) polynomial expansions. Also, the surface tension data have been predicted based on the Sprow–Prausnitz (SP) equation. The results show that good agreement is obtained between experimental and predicted data of surface tension, a fact which confirms the applicability of the SP equation in the binary mixtures with polar components. The modified UNIFAC group contribution method is used for calculation of activity coefficients of components in mentioned systems. Finally, surface mole fraction of alcohol at the (air + liquid) interface were calculated from (SP) equations. The results show that the surface concentration of alcohol in binary mixtures increase with increasing the alkyl chain length of alcohol.

Modelling and experimental validation of dimethyl carbonate solvent recovery from an aroma mixture by batch distillation

Modelling and experimental validation of solvent recovery from an aroma mixture by batch distillation process is presented, with particular emphasis of the effect of the prediction of the physicochemical properties and the phase equilibrium data on the content of the aroma compounds in the distillate cuts. The illustrative case study refers to an industrial batch distillation to recover dimethyl carbonate (DMC) from an extract generated by a solvent extraction process involving variable natural raw materials for tailored perfume and fragrance applications. Due to the high number of aroma compounds in natural extracts, a synthetic mixture containing six target aroma compounds (α-pinene, eucalyptol, linalool, cis-3-hexenol, fenchone and benzyl acetate) was mixed with DMC for the modelling and experimental studies of the batch distillation process. The methodology is tested through the simulation of the process with BatchColumn® software. As physicochemical properties of the aroma compounds and the vapour–liquid equilibrium (VLE) of all involved mixtures are required for simulation study, group contribution methods are used to predict missing properties such as vapour pressure, vaporisation enthalpy and liquid and vapour heat capacities. For VLE calculation, the modified UNIFAC group contribution method is considered and new binary interaction parameters for the main groups COO and CH2O are regressed from experimental data. Simulation results are in good agreement with experiments carried out in a fully automated batch distillation column at 15 kPa and help optimise the industrial process operation. The proposed methodology can be applied for the design of other solvent recovery process in fragrance industry.

Thermodynamic modeling of VLE and VLLE for the ternary system of 2,3,3,3-tetrafluoroprop-1-ene(R1234yf) + propane (R290) + 1,1,1,2-tetrafluoroethane(R134a) at 253.15 K-313.15 K

The excess Gibbs free energy-equation of state (GEEoS) models is presented based on the Peng-Robinson (PR) EoS combined with the Wong-Sandler (WS) mixing rule and the modified UNIFAC group contribution method (PR-WS-MUNIFAC). The average absolute deviation (AAD) of vapor phase mass fraction and the absolute average relative deviation (AARD) of pressure are 0.0047 and 0.53%, respectively, for R152a + R1234yf; 0.0064、0.0050 and 1.59%, respectively, for R32 + R125 + R134a. The VLE properties of the ternary mixture R1234yf + R290 + R134a as a drop-in replacement for R134a were predicted over the temperature range of (253.15–313.15 K) at 10 K intervals. The vapor–liquid-liquid equilibrium (VLLE) was qualitatively analyzed in theory, and the relevant phase equilibrium diagrams were constructed. The R290 + R134a system has clear characteristics of VLLE near the azeotropic point; the pressure of the upper critical end point (UCEP) is approximately 1.627 MPa. Liquid phase separation also exists in the ternary system of R1234yf + R290 + R134a.

Vapor–liquid equilibrium of isoamyl alcohol + isoamyl propionate and propionic acid + isoamyl propionate systems at 50.00, 101.33 and 150.00 kPa

In this work, the isobaric vapor–liquid equilibrium (VLE) for the pseudo-binary systems isoamyl alcohol+isoamyl propionate and propionic acid+isoamyl propionate at three different pressures is reported. Measurements were done in a dynamic equilibrium cell (Fischer Labodest VLE 602) at 50.00, 101.33 and 150.00kPa. The experimental data were tested for thermodynamic consistency with point, total area and infinite dilution tests, using the Hayden–O’Connell equation-of-state for the calculation of vapor fugacity coefficients and the Dortmund modified UNIFAC group contribution method for the prediction of excess enthalpies. VLE data were correlated using the NRTL activity model and good agreement with experimental data was observed.

Isobaric Vapor−Liquid Equilibria at 101.32 kPa and Densities, Speeds of Sound, and Refractive Indices at 298.15 K for MTBE or DIPE or TAME + 1-Propanol Binary Systems

The isobaric vapor−liquid equilibria (VLE) at 101.32 kPa and densities, speeds of sound, and refractive indices at 298.15 K have been measured for binary liquid mixtures of 2-methoxy-2-methylpropane (MTBE) or 2-isopropoxypropane (DIPE) or 2-methoxy-2-methylbutane (TAME) and 1-propanol. The molar volumes, molar refractions, and isentropic compressibilities have been calculated from these experimental data. The excess molar volumes and the deviations in molar refraction and isentropic compressibility upon mixing have been satisfactorily correlated by the Redlich−Kister polynomial. The vapor−liquid equilibrium data have been found thermodynamically consistent and have been adequately correlated by means of Wilson, NRTL, and UNIQUAC equations. The ASOG and the original and modified UNIFAC group contribution methods have not afforded very adequate predictions of data involved in this study.

Isobaric vapour–liquid equilibria of binary 1-propoxy-2-propanol mixtures with water and alcohols at reduced pressure

A dynamic recirculation apparatus has been used to determine the isobaric phase equilibria of binary 1-propoxy-2-propanol mixtures with water and different alcohols (methanol, ethanol, 2-butanol and 1-hexanol). The systems exhibit both positive and negative deviations from Raoult’s law. No azeotropic mixture is found in any of the systems under investigation. The binary diagram of water/1-propoxy-2-propanol (PnP) shows the well-known liquid–liquid-separation. The experimental results are correlated with the Wilson, NRTL and UNIQUAC model and also compared to the COSMO-RS predictive model and the modified UNIFAC group-contribution method. Additionally, the vapour pressure of PnP has been determined experimentally up to 140 ° C as prerequisite for modelling of the data.

Isobaric Vapor−Liquid Equilibria of Hexane + 1-Decene and Octane + 1-Decene Mixtures

In this work the isobaric vapor−liquid equilibrium (VLE) data for hexane + 1-decene and octane + 1-decene systems have been measured at 101.33 kPa. The results were correlated using the Margules, Van Laar, Wilson, and UNIQUAC equations for the liquid phase activity coefficients. The average deviations fall within the same range for all models and agree well with experimental VLE data obtained in this work. Also, the experimental results were compared with the predictions of the modified UNIFAC group contribution method, which suggests that UNIFAC works well for unbranched alkane + 1-alkene systems.

Isobaric vapor–liquid equilibria for systems composed by 2-ethoxy-2-methylbutane, methanol or ethanol and water at 101.32 kPa

Isobaric vapor–liquid equilibrium (VLE) data for 2-ethoxy-2-methylbutane (TAEE) + methanol + water and TAEE + ethanol + water ternary systems, and for their binary subsystems alcohol + ether, have been determined experimentally at 101.32 kPa. Both binary systems form an azeotrope with a minimum boiling point. The ternary system TAEE + methanol + water does not form a ternary azeotrope, however, the ternary system TAEE + ethanol + water shows a ternary azeotrope near the top of the binodal. Thermodynamically consistent VLE measurements have been satisfactorily correlated with NRTL, and UNIQUAC equations for the liquid phase activity coefficient. The ASOG and the original and modified UNIFAC group-contribution methods do not predict adequately the VLE data of this work.

Isobaric Vapor−Liquid Equilibria for the Ternary System of 2-Methyl-1-butanol, 3-Methyl-1-butanol, and Ethylene Glycol at 101.3 kPa

Isobaric vapor−liquid equilibrium data for the ternary system 2- methyl-1-butanol (1) + 3- methyl-1-butanol (2) + ethylene glycol (3) were measured in a modified Rose recirculation still at 101.3 kPa. The experimental data were satisfactorily correlated with the Wilson equation. They were also compared with the predictions by Weidlich's modified UNIFAC group contribution method, and the deviations were also small. The both models are satisfied with the accuracy demanded of process development, design, and simulation.

Experimental data, correlation and prediction of isobaric VLE for the ternary mixture (2-butanol + n-hexane + 1-chlorobutane) at 101.3 kPa

Isobaric vapour–liquid equilibrium (VLE) has been experimentally studied for the ternary mixture 2-butanol (1) + n-hexane (2) + 1-chlorobutane (3), at the pressure of 101.3 kPa. The activity coefficients were found to be thermodynamically consistent and they were satisfactorily correlated with the Wilson, NRTL and UNIQUAC equations. They have been also compared with the results obtained from the application of the ASOG and the modified UNIFAC group contribution methods. The boiling points of the solutions were correlated with compositions by using the Wisniak–Tamir equations. The results obtained indicate that the ternary system deviates positively over the whole compositions range. Azeotropic behaviour was not found for the ternary mixture.

Prediction of Infinite Dilution Activity Coefficients Using COSMO-RS

Infinite dilution activity coefficients (IDACs) are important characteristics of mixtures because of their ability to predict operating behavior in distillation processes. Thermodynamic models are used to predict IDACs since experimental data can be difficult and costly to obtain. The models most often employed for predictive purposes are the “original and modified UNIFAC Group Contribution Methods” (GCMs). COSMO-RS (COnductor-like Screening MOdel for Real Solvents) is an alternative predictive method for a wide variety of systems that requires a limited minimum number of input parameters. A significant difference between GCMs and COSMO-RS is that a given GCMs' predictive ability is dependent on the availability of group interaction parameters, whereas COSMO-RS is only limited by the availability of individual component parameters. In this study COSMO-RS was used to predict infinite dilution activity coefficients. The database assembled by, and calculations with various UNIFAC models carried out by, Vouts...

(Vapour + liquid) equilibrium of (DIPE + IPA + water) at 101.32 kPa

Thermodynamically consistent (vapour + liquid) equilibrium data at 101.32 kPa have been determined for (diisopropyl ether + isopropyl alcohol + water) and its constituents (diisopropyl ether + isopropyl alcohol) and (isopropyl alcohol + water). The NRTL and UNIQUAC equations for the liquid phase activity coefficients were found to correlate better the experimental data. The ASOG and the original and modified UNIFAC group-contribution methods did not represent adequately the (vapour + liquid) equilibrium data of this study.

Isobaric Vapor−Liquid Equilibrium for the Binary Mixtures (2-Butanol + n-Hexane) and (2-Butanol + 1-Butylamine) and for the Ternary System (2-Butanol + n-Hexane + 1-Butylamine) at 101.3 kPa

Isobaric vapor−liquid equilibrium has been experimentally studied for the binary mixtures 2-butanol + n-hexane and 2-butanol + 1-butylamine and for the ternary mixture 2-butanol + n-hexane + 1-butylamine at 101.3 kPa. The activity coefficients were found to be thermodynamically consistent, and they were satisfactorily correlated with the Margules, van Laar, Wilson, NRTL, and UNIQUAC equations. The activity coefficients were also compared with the results obtained from the application of the ASOG and modified UNIFAC group contribution methods. The boiling points of the solutions were correlated with compositions by the Wisniak−Tamir equations. The results obtained indicate that the binary system 2-butanol + n-hexane deviates positively from ideality, whereas 2-butanol + 1-butylamine deviates negatively from ideality. The ternary system deviates positively or negatively depending on the composition. Only the binary systems present azeotropy. Azeotropic behavior was not found in the ternary mixture.

Separation of chlorobenzoic acids by dissociation extractive crystallization

Separation of o- and p-chlorobenzoic acids (CBAs) has been investigated by a two-phase process of dissociation extractive crystallization. On the basis of a screening procedure developed from thermodynamic considerations, methanol and piperazine were selected as a solvent and reagent, respectively. The ternary phase equilibrium diagram depicting several isotherms has been constructed for the o-CBA– p-CBA–methanol system. Also included are the corresponding calculated values based on a modified UNIFAC group contribution method and these show good agreement for such a complex system. A series of batch equilibrium precipitation experiments was performed and the proposed thermodynamic model predicted comparable concentrations of all species in the solution phase at equilibrium. Good recovery of o-CBA (in excess of 90%) was achieved in a single stage and very high separation factors (usually approaching infinity) were possible indicating the potential efficacy of the separation technique for this system.

Phase equilibria involved in extractive distillation of 2-methoxy-2-methylpropane+methanol using 1-butanol as entrainer

Consistent vapour–liquid equilibrium (VLE) data at 101.32 kPa have been determined for the ternary system 1-butanol+methanol+2-methoxy-2-methylpropane, correlated by means of the Wilson, NRTL, and UNIQUAC equations, and compared with the results predicted by using the same equations with interaction parameters obtained from data for the relevant binary systems. The predictions deviated only slightly from the experimental data. The Wilson equation provided the most satisfactory prediction. Moreover, deviations were smaller than those obtained when the equilibrium data were predicted using the ASOG-KT and the original and modified UNIFAC group-contribution methods. The results obtained with a commercial simulator (ChemCAD IV) indicate that extractive distillation with 1-butanol as entrainer is a feasible method for the separation of 2-methoxy-2-methylpropane (MTBE) and methanol.

Isobaric VLE data of the binary mixture ( n-hexane+1-chlorobutane) and the ternary system (1-butanol+ n-hexane+1-chlorobutane) at 101.3 kPa

Isobaric vapour–liquid equilibrium (VLE) for the ternary mixture, 1-butanol (1)+ n-hexane (2)+1-chlorobutane (3) and for the binary mixture, n-hexane (1)+1-chlorobutane (2) at 101.3 kPa has been experimentally studied. The activity coefficients were found to be thermodynamically consistent and were satisfactorily correlated with the Margules, van Laar, Wilson, NRTL and UNIQUAC equations. They have been also compared with the results obtained from the application of ASOG and the modified UNIFAC group contribution methods.

Isobaric VLE Data of the Ternary System (1-Butanol+n-Hexane+1-Butylamine) and the Three Constituent Binary Mixtures at 101.3kPa.

The isobaric vapour-liquid equilibrium has been experimentally studied for the ternary mixture (1-butanol + n-hexane + 1-butylamine) and for the binary mixtures (1-butanol + n-hexane), (1-butanol + 1-butylamine), and (n-hexane + 1-butylamine) at 101.3 kPa. The activity coefficients were found to be thermodynamically consistent and they were satisfactorily correlated with the Margules, Van Laar, Wilson, NRTL and UNIQUAC equations. They have been also compared with the results obtained from the application of ASOG and the modified UNIFAC group contribution methods.

Vapour-Liquid Equilibrium of the Ternary System (Benzene + Cyclohexane + Hexane) at 40.0 kPa AND 101.3 kPa

Abstract The isobaric vapour-liquid equilibrium has been experimentally studied for the ternary mixture (Benzene + Cyclohexane + Hexane) at pressures of 40.0 kPa and 101.3 kPa. The equilibrium data have been correlated using the equations of Wilson, NRTL and UNIQUAC. They have been also compared with the results obtained from the application of the modified UNIFAC group contribution method. The mixture does not show azeotrope.

Prediction of Excess Enthalpy and Excess Entropy Using Modified UNIFAC Group Contribution Methods.

We have examined the accuracy of recent versions of the UNIFAC group contribution method (Larsen et al., 1987; Weidlich and Gmehling, 1987 and Gmehling et al., 1993) for predicting excess enthalpy and excess entropy. For comparison, we also include the results predicted according to the ASOG method

Isobaric Vapor-Liquid Equilibria of Methanol + 1-Octanol and Ethanol + 1-Octanol Mixtures

Isobaric vapor-liquid equilibrium data for methanol + 1-octanol and ethanol + 1-octanol have been measured at 101.325 kPa. The results were checked for thermodynamic consistency using Fredenslund et al.'s test, correlated using Wilson, NRTL, and UNIQUAC equations for the liquid phase activity coefficients, and compared with the predictions of the ASOG, UNIFAC, and modified UNIFAC group contribution methods. © 1995, American Chemical Society. All rights reserved.