Thermodynamic properties of binary mixtures containing aldehydes. II. Liquid-vapor equilibria in normal or branched alkanal + normal alkane mixtures: Analysis in terms of a quasichemical group-contribution model

Recent liquid-vapor equilibrium data for three alkanal + n-alkane mixtures are examined on the basis of the surface-interaction version of the quasichemical group-contribution theory used in Part I to correlate and predict excess enthalpies and excess Gibbs energies for such mixtures. The predictions prove to be accurate to better than 10%. Using the new data, revised interaction parameters are proposed for the estimation of liquid-vapor equilibrium for normal or branched alkanal + normal alkane mixtures.     

Analysis of {[N,N-dialkylamide or 1-methyl-2-pyrrolidone] + 1-chloroalkane or α,ω-dichloroalkane} mixtures in terms of group contribution

The experimental vapour–liquid equilibria, VLE, excess molar Gibbs energies, , and excess molar enthalpies, , determined previously for the systems N,N-dimethylformamide, or N,N-dimethylacetamide, or 1-methyl-2-pyrrolidone + 1-chlorobutane, or +1-chlorohexane, or +1-chlorooctane, or +1,2-dichloroethane, or +1,4-dichlorobutane, or +1,6-dichlorohexane, are examined using the DISQUAC group contribution model. The dispersive and quasi-chemical interchange parameters for the contacts chloro-amide in the mixtures with N,N-dialkylamide or 1-methyl-2-pyrrolidone with chloro- or α,ω-dichloroalkane were calculated. The model reproduces quite well the experimental data.     

DISQUAC predictions of phase equilibria,molar and standard partial molar excess quantities for 1-alkanol+cyclohexane mixtures

Literature data for phase equilibria: vapor-liquid VLE, liquid-liquid LLE, and solid-liquid SLE; molar excess Gibbs energies G ^E , molar excess enthalpies H ^E ; activity coefficients _i and partial molar excess enthalpies H _i ^E,o at infinite dilution for 1-alkanol (1)+cyclohexane (2) mixtures are examined by the DISQUAC group contribution model. For a more sensitive test of DISQUAC, the azeotropes, obtained from the reduction of the original isothermal VLE data, are also examined for systems characterized by hydroxyl, alkane and cyclohexane groups. The alkane/cyclohexane and alkane/hydroxyl interaction parameters have been estimated previously. The cyclohexane/hydroxyl interaction parameters are reported in this work. The first dispersive parameters increase regularly with the size of the alkanol; from 1-octadecanol they are constant; an opposite behavior is encountered for the third dispersive parameters, which are constant from 1-dodecanol. The second dispersive parameters decrease as far as 1-propanol and then increase regularly; from 1-octadecanol they are constant. The quasichemical parameters are equal to those for the alkane/hydroxyl interactions. Phase equilibria, the molar excess functions, and activity coefficients at infinite dilution are reasonably well reproduced. Poor results are found for H _i ^E,o and DISQUAC predictions for H _i ^E,o are strongly dependent on temperature.     

Thermodynamics of 1-alkanol+linear alkanoate mixtures

1-Alkanol?+?linear alkanoate mixtures have been investigated in the framework of the DISQUAC model. The interaction parameters for the OH/COO contacts are reported. The quasichemical parameters are independent of the mixture compounds. The dispersive parameters change with the molecular structure of the components. The same behaviour is observed for the OH/CO (carbonyl) and OH/OCOO (carbonate) contacts. DISQUAC represents well the molar excess Gibbs energies, coordinates of azeotropes and molar excess enthalpies. Using binary parameters only, DISQUAC improves meaningfully predictions on this property from the UNIFAC model for 1-alkanol?+?linear alkanoate?+?hydrocarbon systems. In contrast, the Nitta–Chao and the DISQUAC models yield similar results for the thermodynamic properties of the binary and ternary mixtures considered. 1-Alkanol?+?linear alkanoate mixtures are characterized by strong dipolar interactions between like molecules. In 1-alkanol?+?CH₃COO(CH₂) _{u ?1}CH₃ systems, dipole–dipole interactions between ester molecules are more important for u?≤?7. For u?≥?8, the more important contribution to the excess molar enthalpy comes from the disruption of the alkanol–alkanol interactions. For systems containing a polar compound such as alkanone, alkanoate or linear organic carbonate, dipolar interactions increase in the order: alkanone?<?alkanoate?<?carbonate.     

Proximity effects and cyclization in oxaalkanes+CCl4 mixtures DISQUAC characterization of the Cl–O interactions. Comparison with Dortmund UNIFAC results

Thermodynamic properties, vapor–liquid equilibria (VLE), molar excess Gibbs energies (G^E), molar excess enthalpies (H^E) and natural logarithms of activity coefficients at infinite dilution (ln γ_i^∞) or partial molar excess enthalpies at infinite dilution (H_i^E,∞) of mixtures of oxaalkanes, linear or cyclic monoethers, diethers or acetals, and CCl₄ are studied in the framework of DISQUAC. The oxygen/CCl₄ contacts are characterized by dispersive (DIS) and quasichemical (QUAC) interaction parameters, which are reported. Contacts of the type (polar group)/CCl₄ are usually characterized by DIS parameters only. The effects of proximity and cyclization on the interchange coefficients are examined. In comparison with systems of oxaalkanes and n-alkanes, some differences exist; e.g., linear monoethers and diethers+CCl₄ mixtures are represented by different interaction parameters due to proximity effects of oxygen atoms (i.e., –O–C–C–O–) in diethers. In solutions with cyclic molecules, ring strain seems to be now more important. DISQUAC results are compared with those obtained using the Dortmund version of UNIFAC. From this comparison, it is concluded that it is necessary to distinguish at least between monoethers, diethers and acetals when treating mixtures with oxaalkanes and that each cyclic molecule should be characterized by its own set of interaction parameters.     

Thermodynamics of mixtures containing linear monocarboxylic acids II. Binary systems showing cross-association between components: DISQUAC characterization of linear monocarboxylic acid + 1-alkanol,or + linear monocarboxylic acid mixtures

Binary mixtures containing compounds which show cross-association between them are investigated in terms of DISQUAC: namely, systems with two linear monocarboxylic acids, or with one acid and one 1-alkanol. In the former, the interactions between the COOH groups of the acids are represented by dispersive parameters only. Binary systems involving two 1-alkanols behave similarly. In the linear monocarboxylic acids + 1-alkanol mixtures, the COOH/OH interactions are represented by structure-dependent dispersive and quasichemical parameters. It is shown that those solutions with methanol and ethanol do not fit into the general scheme followed by the higher members of each homologous series considered here. A similar behaviour is found when mixtures containing methanol and benzene or CCl₄ are compared with those involving higher alkanols in the frameworks of DISQUAC or of the Barker's theory.Vapor-liquid equilibria, VLE, and excess enthalpy, H^E, data are consistently described by DISQUAC. Discrepancies are analysed.The UNIQUAC association model or an equation of state (Carnahan-Starling) with the association built in have been applied in the literature as pure correlations of the experimental data for acids + 1-alkanols systems. Their results are compared with those reported in this work by DISQUAC.     

Excess partial molar enthalpies,entropies, Gibbs energies,and volumes in aqueous dimethylsulfoxide

The excess partial molar enthalpies, the vapor pressures, and the densities of dimethylsulfoxide (DMSO)–H₂O mixtures were measured and the excess partial molar Gibbs energies and the partial molar volumes were calculated for DMSO and for H₂O. The values of the excess partial molar Gibbs energies for both DMSO and H₂O are negative over the entire composition range. The results for the water-rich region indicated that the presence of DMSO enhances the hydrogen bond network of H₂O. Unlike monohydric alcohols, however, the solute-solute interaction is repulsive in terms of the Gibbs energy. This was a result of the fact that the repulsion among solutes in terms of enthalpy surpassed the attraction in terms of entropy. The data in the DMSO-rich region suggest that DMSO molecules form clusters which protect H₂O molecules from exposure to the nonpolar alkyl groups of DMSO.     

Thermodynamics of mixtures containing a very strongly polar compound: IV – application of the DISQUAC,UNIFAC and ERAS models to DMSO+ organic solvent systems

Binary mixtures of dimethylsulfoxide (DMSO) with alkane, benzene, toluene 1-alkanol, or 1-alkyne have been investigated in terms of DISQUAC. The corresponding interaction parameters are reported. ERAS parameters for 1-alkanol + DMSO mixtures are also given. ERAS calculations were developed considering DMSO as a not self-associated compound.

DISQUAC represents fairly well a complete set of thermodynamic properties: molar excess enthalpies, molar excess Gibbs energies, vapor–liquid equilibria, natural logarithms of activity coefficients at infinite dilution, or partial molar excess enthalpies at infinite dilution. DISQUAC improves UNIFAC calculations for H ^E . Both models yield similar results for VLE. In addition, DISQUAC also improves, ERAS results for 1-alkanol + DMSO mixtures. This may be due to ERAS cannot represent the strong dipole–dipole interactions present in such solutions.     

Thermodynamics of the ternary mixture propan-1-ol + tetrahydrofuran + n-heptane at 298.15 K. Experimental results and ERAS model calculations of G, H and V

Excess molar enthalpies H^E and excess molar volumes V^E have been measured at 298.15 K and 0.1 MPa for the ternary mixture tetrahydrofuran (THF) + propan-1-ol (PrOH) + n-heptane including the three binary mixtures using flow calorimetry and a vibrating tube densitometer, respectively.

Molar excess Gibbs energies G^E have been measured at 298.15 K using a static VLE apparatus equipped with a chromatographic sampling technique for the vapor phase as well as for the liquid phase. Experimental results have been compared with predictions of the ERAS model.     

Thermodynamics of isomeric hexynes + MTBE binary mixtures

The vapor pressures of liquid hex-1-yne or hex-2-yne + methyl 1,1-dimethylethyl ether (MTBE) binary mixtures and of the three pure components were measured by a static method at several temperatures between 263 and 343 K. These data were correlated with the Antoine equation. Excess molar Gibbs energies G^E were calculated for several constant temperatures, taking into account the vapor-phase imperfection in terms of the second molar virial coefficients, and were fitted to the Redlich–Kister equation. Calorimetric excess enthalpy H^E measurements, for these binary mixtures, are also reported at 298.15 K. The experimental VLE and H^E data were used, examining the binary mixtures hex-1-yne or hex-2-yne + MTBE in the framework of the DISQUAC and modified UNIFAC (Do) models. The DISQUAC calculations, reporting a new set of interaction parameters for the contact carbon–carbon triple bond/oxygen ether, is regarded as a preliminary approach.     

Association model of fluids. Simultaneous representation of excess Gibbs energies and excess enthalpies for liquid mixtures with alkanols

The binary excess Gibbs energies and excess enthalpies of liquid mixtures of alkanols and hydrocarbons, acetone, methyl acetate, acetonitrile, organic acid, etc., are simultaneously correlated with a new association model whose equilibrium constants are defined in terms of the modified segment fractions of chemical species. The model predicts ternary vapor-liquid, liquid-liquid equilibria and excess molar enthalpies of those mixtures well using only binary parameters.