Measurement and prediction of solid–liquid phase equilibria for diamine + n-heptane, or cyclohexane

Solid–liquid equilibria (SLE) of N,N,N′,N′-tetramethylethylenediamine, 1,4-dimethylpiperazine and N,N-dimethylaniline+n-heptane or cyclohexane mixtures were measured by a static method. It was found that all systems are simple eutectic systems. Group contribution models have proved fairly successful in predicting SLE, however, the presence of intramolecular effects (ring effect, proximity effect) renders the widely used empirical methods quite inaccurate. However, in this work, the experimental phase diagrams compared satisfactorily with group contribution models (DISQUAC) and also modified UNIFAC (Dortmund version) predictions.     

Activity coefficient at infinite dilution, azeotropic data, excess enthalpies and solid–liquid-equilibria for binary systems of alkanes and aromatics with esters

Binary azeotropic data have been measured at different pressures for ethyl acetate + heptane, methyl acetate + heptane, isopropyl acetate + hexane and isopropyl acetate + heptane by means of a wire band column. Additionally activity coefficients at infinite dilution have been determined for ethyl acetate and isopropyl acetate in decane and dodecane in the temperature range between 303.15 and 333.15 K with the help of the dilutor technique. Furthermore excess enthalpies for the binary systems methyl acetate + hexane, methyl acetate + decane, ethyl acetate + hexane and ethyl acetate + decane at 363.15 and 413.15 K have been studied with the help of isothermal flow calorimetry. Finally solid–liquid equilibria for the systems ethyl myristate + benzene and ethyl myristate + p-xylene have been investigated by a visual technique. All these data have been used for the revision and extension of the group interaction parameters of the group contribution method modified UNIFAC (Dortmund) and the group contribution equation of state VTPR. The experimental data was compared with the results predicted using the group contribution method modified UNIFAC (Dortmund) and the group contribution equation of state VTPR.     

Solubility of polycyclic aromatics in binary solvent mixtures using activity coefficient models

Polycyclic aromatic hydrocarbons (PAHs) precipitation is one of the major problems in the hydrocracking units. In this investigation, pyrene and phenanthrene were selected because they were found to be in higher concentrations in the feed to hydrocracking units. Their solubilities were investigated in toluene solvent mixture of iso-octane and heptane over a temperature range from 293 to 323 K. The experimental solubility data were used to predict the interaction parameters for seven different solid–liquid equilibrium models. The following activity coefficient models were used; Wilson, NIBS/Redlich–Kister, UNIQUAC, modified UNIFAC, modified UNIFAC (Dortmund), Flory–Huggins and Sheng. The interaction parameters were expressed as a second-order polynomial function in temperature. In order to test the models, the average absolute deviation percentage (AADP) was used. The overall AADP was found to range from approximately 7 to 14%. The models can be arranged according to their accuracy in a descending order based on AADP as follows: NIBS/Redlich–Kister, Wilson, UNIQUAC, Sheng, Flory–Huggins, modified UNIFAC (Dortmund) and finally modified UNIFAC. All models used in this work gave reasonable results; however, the group contribution models can also be used as a predictive tool for the solubility measurement of pyrene and phenanthrene in other solvents containing the same groups of the solvents used in this study.     

Estimation of the Nitta-Chao Parameters for the ether-group. Ether + n-alkane mixtures

In this work we have estimated the structural and interactional parameters of the ether- group for the group-contribution model of Nitta-Chao using a extensive experimental database of thermodynamic properties of ethers (monoethers, polyethers and acetals) and ether + n-alkane and ether + ether mixtures. The results obtained by Nitta-Chao model with this parameters get closer to the experimental values than those obtained with parameters of Eckart et al. (1986). The thermodynamic properties obtained by the Nitta-Chao model with old and new parameters were compared to predictions by other models such as Flory (1965) theory, DISQUAC (Kehiaian, 1977) model and UNIFAC model (versions of Dang and Tassios, 1986, and Larsen et al., 1987).     

Vapour–liquid equilibria, azeotropic data, excess enthalpies, activity coefficients at infinite dilution and solid–liquid equilibria for binary alcohol–ketone systems

Isothermal vapour–liquid equilibria (VLE), solid–liquid equilibria and excess enthalpies have been measured for the systems cyclohexanone + cyclohexanol and 2-octanone + 1-hexanol. Additionally in this paper binary azeotropic data at different pressures for 1-pentanol + 2-heptanone and 1-hexanol + 2-octanone have been determined with the help of a wire band column. Furthermore activity coefficients at infinite dilution for methanol, ethanol, 1-butanol and 1-propanol in 2-octanone at different temperatures have been measured with the help of the dilutor technique. These data together with literature data for alcohol–ketone systems were used to fit temperature-dependent group interaction parameters for the group contribution method modified UNIFAC (Dortmund) and the group contribution equation of state VTPR.     

Excess enthalpy of ternary mixture for diamine+heptane+cyclohexan

The excess molar enthalpy of ternary mixture for 3-diethylaminopropylamine+heptane+cyclohexane were measured using a Calvet microcalorimeter at 303.15 K. Empirical equations, Redlich-Kister, Tsao-Smith, and Kohler and group contribution models, UNIFAC (modified version) and DISQUAC have been applied. A reasonable representation of ternary data is obtained. This revised version was published online in August 2006 with corrections to the Cover Date.     

Isothermal vapor–liquid equilibria of bromochloromethane or 1-bromo-2-chloroethane+tetrachloromethane or benzene. Experimental measurements and analysis in terms of group contributions

Isothermal vapor–liquid equilibria (VLE) have been measured for bromochloromethane+tetrachloromethane or benzene at 298.15 K and 313.15 K, and for 1-bromo-2-chloroethane+tetrachloromethane or benzene at 313.15 K. Bromochloromethane+tetrachloromethane shows azeotropic behaviour in the temperature range covered. These experimental results, along with our previous ones on excess enthalpies, are interpreted with two group contribution models: DISQUAC (DISpersive-QUAsiChemical) and modified (Dortmund) UNIFAC (UNIquac Functional group Activity Coefficients).     

Liquid–liquid equilibria of water + ethanol + reformate

Liquid–liquid equilibria (LLE) of the multicomponent system water + ethanol + a synthetic reformate (composed of benzene, n-hexane, 2,2,4-trimethylpentane, and cyclohexane) was studied at atmospheric pressure and at 283.15 and 313.15 K. The mutual reformate–water solubility with addition of anhydrous ethanol was investigated. Different quantities of water were added to the blends in order to have a wide water composition spectrum, at each temperature. We conclude from our experimental results, that this multicomponent system presents a very small water tolerance and that phase separation could result a considerable loss of ethanol that is drawn into the aqueous phase. The results were also used to analyse the applicability of the UNIFAC group contribution method and the UNIQUAC model. Both models fit the experimental data with similar low average root mean square deviations (rsmd ≤ 2.05%) yielding a satisfactory equilibrium prediction for the multicomponent system, although the predicted ethanol (rsmd ≤ 4.6%) compositions are not very good. The binary interaction parameters needed for the UNIQUAC model were obtained from the UNIFAC method.     

Experimental and predicted viscosities of the binary system (n-hexane + 1,3-dioxolane) and for the ternary system (n-hexane + 1,3-dioxolane + 1-butanol) at 298.15 and 313.15 K

Viscosities of the ternary system n-hexane+1,3-dioxolane+1-butanol and the binary system n-hexane+1,3-dioxolane have been measured at atmospheric pressure at 298.15 and 313.15 K. Viscosity deviations for the binary and ternary systems were calculated from experimental data and fitted to Redlich–Kister and Cibulka equations, respectively. The group contribution method proposed by Wu has been used to predict the viscosity of all mixtures.     

Liquid–liquid equilibria of the ternary system water + acetic acid + dimethyl adipate

Liquid–liquid equilibrium (LLE) data of water + acetic acid + dimethyl adipate have been determined experimentally at 298.15, 308.15 and 318.15 K. Complete phase diagrams were obtained by determining binodal curve and tie-lines. The reliability of the experimental tie-line data was confirmed by using the Othmer-Tobias correlation. UNIFAC and modified UNIFAC models were used to predict the phase equilibrium in the system using the interaction parameters determined from experimental data of CH₂, CH₃COO, CH₃, COOH, and H₂O functional groups. Distribution coefficients and separation factors were evaluated for the immiscibility region.     

Viscometric and sorption equilibrium studies on n-alkane-butanone-poly-(dimethylsiloxane) systems

Intrinsic viscosities, [η], second virial coefficients, A₂, and preferential solvation coefficients, λ, for the ternary systems n-alkane (l)-butanone (2)-poly(dimethylsiloxane) (PDMS) (3), with n-alkane = n-hexane, n-heptane, n-nonane and n-undecane, have been determined at 20°. The K and a constants of the Mark-Houwink equation have been evaluated over the whole composition range of the binary solvent mixtures. Polymer (mixed solvent) interaction parameters and unperturbed dimensions have been evaluated both from A₂ and [η] data, the feasibility of A₂ evaluation from [η] experimental data or vice versa being discussed. Experimental and calculated (through Dondos and Patterson theory) excess free energies, G^E, follow similar trends with composition; large numerical discrepancies, however, arise between both sets of G^E. Maxima in [η], in a and in A₂ are accompanied by inversion points in λ. The solvent mixture composition range in which PDMS is preferentially solvated by n-alkane, as well as the extent of solvation, decrease with increasing number of carbon atoms in the n-alkane.     

Liquid–liquid equilibria of ternary mixture (propargyl alcohol + diisopropyl ether + water)

The liquid–liquid equilibria (LLE) of ternary mixture (propargyl alcohol + diisopropyl ether + water) were measured under atmospheric pressure and at different temperatures of 297.25, 304.35, 313.15, and 323.25 K. It was found that the end points of tie-lines at the four temperatures were located almost on a common solubility curve but the tie-lines possessed different slopes that described different equilibrium relations. A comparison of the predicted values through use of UNIFAC method with the measured LLE data was carried out but the predicted values showed remarkable deviations from the experimental data.     

Isothermal vapor-liquid equilibria of bromochloroalkanes with heptane or cyclohexane: Measurement and analysis in terms of group contributions

Isothermal vapor-liquid equilibria (VLE) have been measured for liquid bromochloromethane + heptane or cyclohexane at 25‡C and 40‡C, and for 1-bromo-chloroethane + heptane or cyclohexane at 40‡C. These experimental results, along with our previous ones on excess enthalpies, as well as literature data on activity coefficients at infinite dilution, are interpreted in terms of the DISQUAC group contribution model, and are compared with UNIFAC predictions.     

Isothermal vapor–liquid equilibria and excess molar volumes for 2-methyl pyrazine (2MP) containing binary mixtures

2-Methyl pyrazine (2MP) has led to significant interest for its industrial and pharmaceutical uses. The new vapor–liquid equilibria (VLE) at 353.15 K and excess molar volumes (V^E) at 298.15 K over the whole mole fraction range for seven binaries (water, n-hexane, cyclohexane, n-heptane, methylcyclopentane (MCP), methylcyclohexane (MCH) and ethyl acetate (EA) with 2MP) have been measured. VLE were measured by using headspace gas chromatography and V^E were determined using precision density meter. The water+2MP system has only the minimum boiling azeotrope. The experimental VLE and V^E data were well correlated in terms of common g^E models and Redlich–Kister equation, respectively.     

Solid-liquid equilibria of binary systems containing <Emphasis Type="Italic">n</Emphasis>-tetracosane with naphthalene or dibenzofuran

A differential scanning calorimeter (DSC) was used to determine binary solid-liquid equilibria (SLE) for dibenzofuran+n-C24 and naphthalene+n-C24 mixtures. Results obtained with this technique were compared with those predicted by two modified UNIFAC (Universal Functional group Acitivity Coefficients) versions. This model is employed with the idea to extensively investigate the validity of UNIFAC (Larsen and Gmehling versions). The corresponding activity coefficients were calculated and applied to the prediction of non-electrolyte mixtures real behavior. Reasons of prediction without success in the case of using original interaction parameters, were analysed and discussed. Interesting representation of solubility diagrams was obtained using partly readjusted UNIFAC interaction parameters. The two systems selected can be used for contributing to develop the data base using group contribution methods. For practical purposes, SLE are of interest in chemical process design, especially when process conditions must be specified to prevent precipitation of a solid.     

Effect of combining rules for cubic equations of state on the prediction of double retrograde vaporization

In this work, the phenomenon of double retrograde vaporization (DRV) is simulated using the Peng–Robinson equation of state with the classical mixing rules and several combining rules for the cross-energy and cross-co-volume parameters. The binary interaction parameters are set equal to zero in all cases, i.e., the calculations are entirely predictive. An interesting conclusion is that the predictions using the classical combining rules (geometric mean rule for a_ij and arithmetic mean rule for b_ij) provide the best agreement with the experimental data for all the systems tested: methane + n-butane, methane + n-pentane, ethane + limonene, and ethane + linalool. Another interesting observation is that several combining rules for b_ij, other than the arithmetic mean rule, predict the existence of three phases in equilibrium in a very narrow temperature range close to the critical temperature of methane in the methane + n-pentane system, even though, literature data indicates that n-hexane is the first n-alkane to present partial liquid phase immiscibility with methane.     

Vapor–liquid equilibria and excess molar volumes of diethylamine(1) + acetone(2) and diethylamine(1) + acetonitrile(2) binary systems

Isothermal vapor–liquid equilibrium (VLE) data for diethylamine(1)+acetone(2) and diethylamine(1)+acetonitrile(2) binary systems were obtained at 323.15 K by dynamic method. Excess molar volumes at 298.15 K for these systems were measured by a dilution dilatometer. VLE data have been checked for thermodynamic consistency and correlated by Wilson, NRTL and UNIQUAC equations. UNIFAC group interaction parameters for CH₂NH---CH₃CO and CH₂NH---CH₃CN pairs are also obtained from the experimental VLE data.     

Vapor liquid equilibrium for the binary systems 2-methylpentane + 2-butanol at 329.2 K and n-hexane + 2-butanol at 329.2 and 363.2 K with a static apparatus

A static total pressure apparatus was build. Isothermal vapour–liquid equilibrium of two binary systems, 2-methylpentane+2-butanol at 329.2 K and n-hexane+2-butanol at 329.2 K and 363.2 K were measured. The results of the 2-methylpentane+2-butanol measurements were compared with earlier measurements made with a recirculation still and good agreement was found. The ability of estimation methods (UNIFAC and modified UNIFAC Dortmund) to predict the measured data was tested. The capability of the original UNIFAC to predict the behaviour of the systems measured was worse than the performance of the modified UNIFAC Dortmund.