UNIFAC Group Contribution Method Research Articles

Phase stability of the system limonene + linalool + 2-aminoethanol

Liquid–liquid equilibrium data for the ternary system limonene + linalool + 2-aminoethanol at 298.15, 308.15 and 318.15 K are reported. The experimental data have been correlated using UNIQUAC and NRTL equations obtaining the binary interaction parameters. This last equation was used to determine binodal and spinodal curves. The second derivatives of the Gibbs free energy of mixing for binary systems were calculated with the aim to predict the slopes of the ternary tie-lines. Experimental data were also compared with the predictions of the UNIFAC group contribution method.

VLE of the binary systems (dimethyl carbonate with 2-propanol or 2-butanol) and (diethyl carbonate with methylcyclohexane) at 101.3 kPa

Isobaric vapour + liquid equilibria (VLE) have been experimentally determined for the binary systems (2-propanol + dimethyl carbonate (DMC), dimethyl carbonate + 2-butanol, and methylcyclohexane + diethyl carbonate (DEC)) at 101.3 kPa. The activity coefficients were calculated to be thermodynamically consistent and were correlated with the Wilson, NRTL, and UNIQUAC equations. ASOG and UNIFAC group contribution methods will be employed to predict these binary systems. Densities at T = (293.5, 298.15, 303.15, 308.15, and 313.15) K and atmospheric pressure have been measured over the whole composition range for (DEC + methylcyclohexane). Excess molar volumes have been calculated for each temperatures. A polynomial equation has been used to estimate the binary fitting parameters as a function of mole fraction and temperature. Standard deviations from the regression lines are shown for the binary mixture.

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.

Heterogeneous catalysed esterification of acetic acid with isoamyl alcohol: kinetic studies

Kinetics of heterogeneous catalysed esterification of acetic acid with isoamyl alcohol was studied with a cation-exchange resin catalyst, Purolite CT-175, in a stirred batch reactor to synthesise a value added ester, isoamyl acetate. Physical and chemical characterisation of the catalyst in the form of scanning electron micrographs, Brunauer–Emmett–Teller (BET) surface area measurement, sodium capacity determination, particle size distribution, and pore size distribution was conducted to assess its performance as a catalyst for esterification reaction. The density functional theory (DFT) model was used to analyse the pore size distribution data of the catalyst. Effects of various parameters such as speed of agitation, catalyst particle size, mole ratio of reactants, reaction temperature, catalyst loading, and reusability of the catalyst were studied to optimise the reaction condition. The equilibrium conversion of acetic acid was found to increase slightly with an increase in temperature from 333 to 363 K and also it increased appreciably with an excess of isoamyl alcohol in the reacting system. CT-175 catalyst can be reused without any loss of catalytic performance. The nonideality of each species in the reacting mixture was accounted for by using the activity coefficient via the use of the UNIFAC group contribution method. The kinetic data were correlated with the Langmuir–Hinshelwood–Hougen–Watson model. The surface reaction is the rate-limiting step.

Isothermal Vapor−Liquid Equilibrium and Excess Enthalpy Data for the Binary Systems Water + Sulfolane and Methanol + N-Methyl-2-pyrrolidone

Isothermal vapor−liquid equilibrium (VLE) and excess enthalpy (HE) data for the two binary systems water + sulfolane and methanol + N-methyl-2-pyrrolidone (NMP) were measured by means of a static technique and an isothermal flow calorimeter, respectively. The experimental data are presented using temperature-dependent interaction parameters for the nonrandom two-liquid model, which were fitted simultaneously to all experimental data from this work and from the literature, and allow us to compare the measured data with the data of the other authors. Furthermore, the experimental results from this work are compared to predictions using the Mod. UNIFAC (Do) group contribution method.

Liquid–Liquid Equilibria of Linalool + Ethanol + Water, Water + Ethanol + Limonene, and Limonene + Linalool + Water Systems

The present work was undertaken to determine liquid–liquid equilibria for ternary systems involved in the citrus essential oil terpeneless using dilute alcohol. Tie-line data have been determined for the linalool + ethanol + water, water + ethanol + limonene, and limonene + linalool + water ternary systems at 298.15 K. The experimental data were satisfactorily correlated using the UNIQUAC and NRTL equations, and the obtained binary interaction parameters are reported. The UNIFAC group-contribution method did not allow adequate predictions of liquid–liquid equilibria involved in this study.

Liquid−Liquid Equilibria of Methyl Acetate + Methanol + Octane or Nonane

Liquid−liquid equilibria for the ternary systems methyl acetate + methanol + octane and methyl acetate + methanol + nonane were studied at (278.15, 288.15, and 298.15) K and at atmospheric pressure. Composition analysis of each phase was carried out by gas chromatography. The nonrandom two-liquid and universal quasichemical models were used to correlate the experimental results. A good fit has been obtained as a function of temperature for all cases studied. The UNIFAC group contribution method and its modifications have been applied to test their prediction capability. A poor prediction was observed from the contribution methods.

Kinetic Study for the Reactive System of Lactic Acid Esterification with Methanol: Methyl Lactate Hydrolysis Reaction

The hydrolysis of methyl lactate catalyzed by an acidic cation-exchange resin, Amberlyst 15, is presented in this work. The kinetic experiments were carried out in a stirred tank batch reactor. The effects of catalyst loading, temperature, and feed composition were investigated. The reaction modeling was carried out by correlating the experimental kinetic data obtained for the esterification (previously reported) and the hydrolysis reactions simultaneously. Three models were essayed, the quasi-homogeneous, the Langmuir−Hinshelwood, and the Eley−Rideal models. Because of the high nonideality of the reaction mixture, the kinetics were expressed in terms of activities. The activity coefficients were calculated by using the group contribution method UNIFAC. The quasi-homogeneous model was found to represent the esterification and hydrolysis reactions over Amberlyst 15 fairly well.

Preferential Solvation in Ternary Solutions Containing Methylbenzoate. A Kirkwood−Buff Fluctuation Theory Study

Density, dynamic viscosity, and refractive index of the hexane/cyclohexane/methylbenzoate ternary solvent and its binary constituents were measured at 298.15 K over the whole composition range. From the experimental measurements, excess and mixing properties were evaluated and correlated with composition using different models. The structure and interactions in the ternary solvent were analyzed starting from the experimental properties by application of the Kirkwood−Buff fluctuation theory of solutions along with the UNIFAC group contribution method for predicting activity coefficients. The local composition and excess (or deficit) number of molecules aggregated around a central one were determined using the Kirkwood−Buff integrals. The properties of the ternary system were used to test the predictive ability of several models. The volumetric properties of the binary and ternary systems were correlated and predicted with the cubic equations of state by Soave and Peng−Robinson combined with two simple mixi...

(Liquid + liquid) equilibria of ternary and quaternary systems with two hydrocarbons, an alcohol, and water at 303.15 K. Systems containing cyclohexane, benzene, ethanol, and water

Tie-line data for the water, ethanol, and cyclohexane [{ w 1H 2O + w 2C 2H 5OH + (1− w 1− w 2)C 6H 12}] ternary system, where w is the mass fraction, was investigated at T=303.15 K. A quaternary system containing these three compounds and benzene { w 1C 2H 5OH + w 2C 6H 6 + w 3C 6H 12 + (1− w 1− w 2− w 3)H 2O} was also studied at the same temperature, while data on its other two partially miscible ternary systems were taken from the literature [the fourth { w 1C 2H 5OH + w 2C 6H 6 + (1− w 1− w 2)C 6H 12} is not partially miscible]. From our experimental results we conclude that this quaternary system presents a very small water tolerance and that phase separation could produce a considerable loss of C 2H 5OH drawn into the aqueous phase. On the other hand, the results also show that the aqueous phase generally contains a higher concentration of C 6H 6 than of C 6H 12. A comparison with other similar quaternary systems investigated in our laboratory was also made. The ternary experimental results were correlated with the UNIQUAC equation, and predicted with the UNIFAC group contribution method. As previously, the equilibrium data of the three ternary systems (including those taken from the literature) were used to determine interaction parameters for the UNIQUAC equation. These parameters were then averaged in order to predict equilibrium data of this quaternary system. The UNIFAC method was also used with the same purpose. The UNIQUAC equation appears to be more accurate than the UNIFAC method for this ternary system. However, this last model is slightly better for the quaternary system, as can be seen from the values of both residuals.

Liquid–solid phase equilibrium study of tetradecane and hexadecane binary mixtures as phase change materials (PCMs) for comfort cooling storage

Phase diagrams (equilibrium diagrams) are a convenient way of depicting the concentration–temperature–pressure relationships of a chemical system at equilibrium. They are invaluable to PCMs thermal storage researches and developers. In the present paper, the liquid–solid phase equilibrium of binary mixture system of tetradedcane and hexadecane has been studied. For theoretical evaluation of the thermodynamic equilibrium between the liquid phase and solid phase of tetradecane and hexadecane, several methods were compared: the UNIFAC group-contribution method, the model of Won, and Pedersen’s model. The temperature–composition phase diagram of the binary system has been obtained by the calculation. The diagram illustrates a binary, isomorphous system with a temperature minimum. Differential scanning calorimetry (DSC) was used to study the phase transformation of the binary system. DSC was run at different ramp rates and results indicate that these mixtures melt and freeze over a temperature range and the temperature range depends on the DSC ramp rate, and in a short mixture concentration interval appears low temperature solid–solid peaks. From the DSC results presented, it is concluded that the behaviour of binary mixtures of n-alkanes is far more complicated than considered in earlier studies. The phase diagram and all information from DSC are very important for designing PCM storage system.

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...

Propanediols for separation of citrus oil: liquid–liquid equilibria of limonene + linalool + (1,2-propanediol or 1,3-propanediol)

To evaluate the use of propanediols for separation of the major components of citrus oil, liquid–liquid equilibrium (LLE) data for the ternary systems limonene+linalool+1,2-propanediol and limonene+linalool+1,3-propanediol were determined at 298.15, 308.15 and 318.15 K. The immiscibility region was found to be larger when the OH groups of solvent were at opposite ends of its carbon chain. The experimental data were satisfactorily correlated using the UNIQUAC and NRTL equations, and the binary interaction parameters so obtained are reported. The data were not satisfactorily predicted by the UNIFAC group contribution method.

(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.

(Liquid+liquid) equilibria of ternary and quaternary systems with two hydrocarbons, an alcohol, and water at T=303.15 K. Systems containing cyclohexane, benzene, methanol, and water

Tie-line data for ternary systems including methanol (CH 3OH), water (H 2O), benzene (C 6H 6), and cyclohexane (C 6H 12) were investigated. Phase diagrams of {w 1 H 2 O+w 2 CH 3 OH+(1−w 1−w 2) C 6 H 12} , {w 1 H 2 O+w 2 C 6 H 12+(1−w 1−w 2) C 6 H 6} , and {w 1 CH 3 OH+w 2 C 6 H 6+(1−w 1−w 2) C 6 H 12} , where w is the mass fraction, were obtained at T=303.15 K. A quaternary system containing these four compounds {w 1 CH 3 OH+w 2 C 6 H 6+w 3 C 6 H 12+(1−w 1−w 2−w 3) H 2 O} was also studied at the same temperature, while the system {w 1 H 2 O+w 2 CH 3 OH+(1−w 1−w 2) C 6 H 6} was taken from the literature. From our experimental results we conclude that this quaternary system presents a very small water tolerance and that phase separation could produce a considerable loss of CH 3OH drawn into the aqueous phase. On the other hand, the results also show that the aqueous phase generally contains a higher concentration of C 6H 6 compared with C 6H 12. The ternary experimental results were correlated with the UNIQUAC equation, and predicted with the UNIFAC group contribution method. The equilibrium data of the four ternary systems (including that taken from the literature) were used to determine interaction parameters for the UNIQUAC equation. These parameters were then used to predict equilibrium data of this quaternary system. The UNIFAC method was also used with the same purpose. The UNIQUAC equation appear to be more accurate than the UNIFAC method, particularly for the {w 1 CH 3 OH+w 2 C 6 H 6+(1−w 1−w 2) C 6 H 12} ternary system, because it predicts an immiscibility region much larger than the experimentally observed. However, both models have small and similar deviations between experimental and predicted values for the quaternary system.

Isobaric Vapor-Liquid Equilibria and Densities for the Binary Systems Oxolane + Ethyl 1,1-Dimethylethyl Ether, Oxolane + 2-Propanol and Propan-2-One + Trichloromethane

Vapor-liquid equilibrium data have been determined at 50 kPa for the binary systems oxolane (THF) + ethyl 1,1-dimethylethyl ether (ETBE) and oxolane + 2-propanol, and at 94 kPa for the system propan-2-one + trichloromethane. Excess volumes have also been determined from density measurements at 298.15 K. The systems oxolane + ethyl 1,1-dimethylethyl ether and oxolane + 2-propanol exhibit slight to moderate positive deviations from ideal behavior and no azeotrope is present. The system propan-2-one + trichloromethane exhibits negative deviations from ideal behavior and presents an azeotrope. The excess volumes of the system oxolane + ethyl 1,1-dimethylethyl ether are negative over the whole mole fraction range while those of the system oxolane + 2-propanol are positive. Excess volumes of the system propan-2-one + trichloromethane, change from negative to positive as the concentration of propan-2-one increases. The activity coefficients and boiling points of the solutions were correlated with the mole fraction by the Wohl, Wilson, UNIQUAC, and NRTL equations, and predicted by the UNIFAC group contribution method. Excess volume data were correlated using the Redlich-Kister expansion. The chemical association theory was applied for explaining the equilibrium behavior of the systems oxolane + 2-propanol and propan-2-one + trichloromethane.

Isobaric Vapour-Liquid Equilibrium of Ternary Mixtures Cyclohexane (or n -Hexane) Plus 1,3-Dioxolane Plus 2-Butanol at 40.0 and 101.3 kPa

Isobaric vapour-liquid equilibrium (VLE) data for the mixtures cyclohexane + 2-butanol and cyclohexane + 1,3-dioxolane + 2-butanol have been obtained with a recirculating still at 40.0 and 101.3 kPa. We also have determined isobaric VLE data at 101.3 kPa for the system n -hexane + 1,3-dioxolane + 2-butanol. The experimental data for all the binary and ternary mixtures were checked for thermodynamic consistency using the method of Van Ness. Activity coefficients have been correlated with different equations (Wilson, Van Laar, Margules, NRTL and UNIQUAC) giving satisfactory results. Predictions with the group contribution methods ASOG and UNIFAC were obtained and compared with experimental data.

Exploring Azeotropes in a Ternary Mixture

The existence of an azeotrope in a ternary mixture containing isopropanol, methylcyclohexane and toluene is explored from a bi-directional approach of computer simulation and experimentation. Distilling the mixture at total reflux, experimental results analyzed by a gasliquid chromatograph were then compared with computer output using a computer programme written by Fletcher based on the Perkins and Doherty model. The computer programmes written by Fredenslund, Gmehling and Rasmussen that are based on the UNIFAC group contribution method for calculating vapour-liquid equilibrium ratios are employed in the prediction calculations. Both approaches confirm existence of an azeotrope between isopropanol and methylcyclohexane. Key words: Azeotrope, Group contribution method, computer simulation (Af. J. of Science and Technology: 2003 4(1): 96-103)

KVAERNER WINS POLYMER EPC ORDER

Headspace gas chromatography mass spectrometry (HS-GC–MS) was used to determine the volatility of six selected hydrophobic deep eutectic solvents (DESs). The partial pressure of each DES constituent (decanoic acid, thymol, 1-tetradecanol, menthol or lidocaine) was measured from 313.15 to 373.15 K. The activity coefficients of the hydrogen bond acceptor (HBA) and the hydrogen bond donor (HBD) were determined to quantify the interactions between the DES constituents, thereby deepening the understanding of the thermodynamic nature of the DESs. In addition, the activity coefficients for both components in each DES were predicted with the UNIFAC group contribution method. Similar trends and reasonably close values were obtained for the measured and predicted activity coefficients. It has been found that the interactions between the DES constituents tend to become weaker with increasing temperature. Strong interactions occur between thymol and lidocaine, and thymol interacts moderately with menthol. A weak force exists between decanoic acid and menthol. The mixtures of menthol with 1-tetradecanol or lidocaine are not strictly DESs since for each DES constituent both the measured and predicted activity value is close to unity. A viscosity study was also carried out to quantify the interactions and similar results were found. The ideal mixing rule was proven to correctly describe the viscosity for the mixture of menthol with 1-tetradecanol or lidocaine. While compared to the ideal mixture viscosity, an increase in viscosity was observed for other studied DESs indicating stronger interactions. Finally, the Perturbed-Chain Statistical Associating Fluid Theory (PC-SAFT) was shown to accurately describe the thermodynamic properties, where the PC-SAFT pure-component parameters for the DESs were obtained by fitting to pure DES density and total vapor pressure data.