Grupo Especializado en Termodinámica de los Equilibrios entre Fasesenglish versionGETEF emblema


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Año 2002

  • Gonzalez, JA; Villa, S; Riesco, N; de la Fuente, IG; Cobos, JC; DISQUAC characterization of mixtures containing alkynes and alkanes or 1-alkanols. Comparison with ERAS model; Thermochim Acta, 381 (2) 2002 103-117
Mixtures formed by alkynes and n-alkanes, cycloalkanes or 1-alcohols have been examined in the framework of the DISQUAC group contribution model. The corresponding interaction parameters are reported. These ones follow some simple rules: (a) the quasichemical (QUAC) interchange coefficients for the aliphatic/acetylene contacts are independent of the alkyne; (b) the dispersive (DIS) parameters for such contacts when isomeric non-terminal alkynes are involved are also independent of the alkyne; (c) in 1-alkanols + alkynes mixtures, the QUAC parameters for the hydroxyl/acetylenic contacts do not depend on the mixture compounds. Thermodynamic properties such as vapor-liquid equilibria (VLE), including coordinates of azeotropes or activity coefficients at infinite dilution (γi), and excess molar enthalpies (HE) are correctly described by DISQUAC. The model can be applied over a wide range of temperature. 1-Alkanols + 1-alkynes, or + 3-hexyne systems have been also characterized in terms of the ERAS model. Calculations were developed neglecting the possible self-association of 1-alkynes. This is reasonable in view of the good results provided by DISQUAC (a purely physical model), and of the very low values of the equilibrium constants obtained from the ERAS model when analyzing 1-alkynes + n-alkanes mixtures. ERAS results on HE are improved by DISQUAC. Both models provide similar results on excess molar Gibb's energies (GE) of 1-alkanols + 3-hexyne mixtures. Excess molar volumes of solutions containing 1-alkanols and 1-alkynes are represented qualitatively by ERAS. Interactions in the treated solutions are analyzed in terms of the effective dipole moment (μ). So, the higher HE of 1-alkynes + n-alkanes mixtures compared to that of non-terminal isomeric alkynes + n-alkanes solutions may be attributed to the higher μ of 1-alkynes. Structural effects are also relevant. In 1-alkanols + 1-alkynes systems, interactions between unlike molecules become weaker with the size increase of the mixture components.
  • Cobos, JC; de la Fuente, IG; Gonzalez, JA; Molar excess enthalpies for some systems containing the OH and (or) O groups in the same or in different molecules; Can J Chem-Rev Can Chim, 80 (3) 2002 292-301
In this work, HmE data at 298.15 K for the systems 1-nonanol + n-C12; 1-nonanol + n-C14; 1-hexanol + 3,6,9-trioxaundecane; and 2-(2-butoxyethoxyethanol) + n-C7 are reported. Measurements were carried out with a standard Calvet-type microcalorimeter. Molar excess functions, including enthalpies and entropies, are carefully examined to report on the main features of the studied solutions. Dipole-dipole interactions between ether molecules are, therefore, of great importance in both 1-alkanols + polyoxaalkanes mixtures and between hydroxyether molecules in alkoxy ethanols + n-alkanes systems. In the second case, it has been attributed to the existence of intramolecular H-bonds in alkoxy ethanols as well as to their higher effective-dipole moment in comparison to that of homologous 1-alkanols. DISQUAC is the only model that can be used to accurately represent thermodynamic functions (except molar excess volumes, VmE) of all of the solutions under study. UNIFAC underestimates dipole-dipole interactions in 1-alkanols + polyoxaalkanes and alkoxyethanols + n-alkanes systems. In exchange, the self-association of the alcohol is overestimated in mixtures of 1-nonanol with n-alkanes. Currently, the ERAS model can only be used to examine these solutions. The variation of the VmE with the size of the n-alkanes is well described.
  • Domanska, U; Gonzalez, JA; Thermodynamics of mixtures containing a very strongly polar compound. Part II. Solid-liquid equilibria for sulfolane plus nitrile systems and characterization of the sulfolane-nitrile and sulfolane-1-alkyne interactions in terms of DISQUAC; Can J Chem-Rev Can Chim, 80 (5) 2002 476-482
Equilibrium temperatures for solid-liquid transitions of mixtures formed by sulfolane and ethanenitrile, propanenitrile, butanenitrile, or pentanenitrile were measured by a dynamic method. The solid-liquid equilibria phase diagrams show positive deviations from Raoult's law, except for the system with ethanenitrile, which is nearly ideal. The sulfolane-nitrile and sulfolane-1-alkyne interactions have been characterized in terms of the DISQUAC group contribution model. DISQUAC properly represents a complete set of thermodynamic properties: solid-liquid equilibria, molar excess enthalpies, and natural logarithms of activity coefficients. DISQUAC predictions are valid over a wide temperature range.
  • Villa, S; Riesco, N; de la Fuente, IG; Gonzalez, JA; Cobos, JC; Thermodynamics of mixtures with strongly negative deviations from Raoult's law. Part 6. Excess molar volumes at 298.15 K for 1-alkanols+dibutylamine systems. Characterization in terms of the ERAS model; Fluid Phase Equilibr, 198 (2) 2002 313-329
Excess molar volumes, VmE, at 298.15 K and atmospheric pressure over the entire composition range for binary mixtures of methanol, ethanol, 1-propanol, 1-butanol, 1-pentanol, 1-hexanol, 1-heptanol and 1-octanol with dibutylamine are reported. They are calculated from densities measured with a vibrating-tube densimeter. All the excess volumes are large and negative over the whole mole fraction range, indicating strong interactions between unlike molecules, which are more important for the systems involving methanol or ethanol, characterized by the most negative VmE. For the other mixtures, VmE at equimolar composition, is approximately constant. The VmE curves are nearly symmetrical. The VmE and excess molar enthalpies (HmE) of the mixtures studied are consistently described by the ERAS model. The ERAS parameters confirm that the strongest interactions between unlike molecules are encountered in the methanol + dibutylamine system.
  • Domanska, U; Szurgocinska, M; Gonzalez, JA; Thermodynamics of binary mixtures containing organic carbonates. 12. SLE and LLE measurements for systems of dimethyl carbonate with long n-alkanes. Comparison with DISQUAC and modified UNIFAC predictions; Ind Eng Chem Res, 41 (13) 2002 3253-3259
Using the available interaction parameters for organic carbonate + alkane mixtures, the ability of the. DISQUAC, and modified UNIFAC group contribution model to predict solid-liquid equilibria (SLE). and liquid-liquid equilibria (LLE) is investigated. Six sets of the SLE and LLE temperatures for dimethyl carbonate + n-alkane (octadecane,,eicosane, docosane, tetracosane, hexacosane, and octacosane) systems have been measured by a dynamic method from 278.65 K to the; melting point of the long-chain n-alkane and to the upper critical temperature of two coexisting phases. The SLE data have been correlated by three equations: Wilson, UNIQUAC, and NRTL. The existence of a solid-solid first-order phase transition in n-alkanes has been taken into consideration in the solubility calculations. The relative standard deviations of the solubility temperature correlation for all measured data vary from 0.2 to 1.3 K and depend on the particular equation used. The LLE coexistence curves' are very asymmetrical with respect to mole fraction, with the asymmetry increasing with the size of the n-alkane. The critical solution points vary almost linearly with the number of carbon atoms of the n-alkane. The SLE curves are usually well predicted by DISQUAC and modified UNIFAC models with an average standard deviation of less than 1.6 K.
  • Aboy, M; Villa, S; Riesco, N; de la Fuente, IG; Gonzalez, JA; Cobos, JC; Liquid-liquid equilibria for acetic anhydride plus selected alkanes; J Chem Eng Data, 47 (4) 2002 950-953
Liquid-liquid equilibria (LLE) temperatures for systems of acetic anhydride with hexane, heptane, octane, decane, cyclohexane, and methylcyclohexane have been measured between 314 K and the upper critical solution temperature (UCST). The coexistence curves were determined visually. They have a rather horizontal top, and their symmetry depends on the size of the alkane. Interaction parameters in the framework of the DISQUAC model for anhydride (CO-O-CO)/cyclohexane contacts are reported. The same set of interaction parameters can be used to represent, LLE, vapor-liquid equilibria, and molar excess enthalpies.
  • Gonzalez, JA; Szurgocinska, M; Domanska, U; Thermodynamics of mixtures containing organic carbonates - Part XIII. Solid-liquid equilibria of long-chain 1-alkanol plus dimethyl or diethyl carbonate systems: DISQUAC and ERAS analysis of the hydroxyl/carbonate interactions; Fluid Phase Equilibr, 200 (2) 2002 349-374
Solid-liquid equilibrium temperatures for systems of 1-tetradecanol, 1-hexadecanol, 1-octadecanol or 1-icosanol with dimethyl or diethyl carbonate have been measured using a dynamic method. The alcohols present two first order transitions.
1-Alkanols + linear organic carbonates mixtures are studied using DISQUAC and ERAS models. The corresponding interaction parameters are reported. They behave similarly in both models. In DISQUAC, the QUAC parameters are independent of the mixture compounds, as in many other alcoholic solutions previously analyzed. The DIS parameters increase with the size of the alcohol. They remain constant for the longer alcohols. In ERAS, ΔυAB* is independent of the mixture components, while ΔhAB* depends only on the carbonate.
DISQUAC yields a consistent description of the thermodynamic properties examined: vapor-liquid equilibria molar excess Gibbs energies, Solid-liquid equilibria and molar excess enthalpies.
DISQUAC improves ERAS results on excess molar enthalpies, as the calculated curves using ERAS are shifted to the region of low concentration in alcohol. This means that, in terms of ERAS, the contribution to the excess molar enthalpy from the self-association of the alcohol is overestimated. Molar excess volumes are well represented by ERAS.
From the analysis of the excess molar enthalpy curves, it is concluded that they are determined mainly by dipolar interactions between carbonate molecules. Excess molar volumes are relatively low indicating strong structural effects.
  • Romero, T; Riesco, N; Villa, S; de la Fuente, IG; Gonzalez, JA; Cobos, JC; Excess molar volumes at 298.15 K of binary liquid organic mixtures containing n-alkanones and linear ethers - Application of Flory's theory; Fluid Phase Equilibr, 202 (1) 2002 13-27
Excess molar volumes, VmE, at 298.15 K and, atmospheric pressure over the entire composition range for binary mixtures of 2-butanone with di-n-butyl ether and 2-pentanone and 3-pentanone with di-n-butyl ether and 2,5-dioxahexane, 2-heptanone and 4-heptanone with di-n-butyl ether, 2,5-dioxahexane and 3,6,9-trioxaundecane are reported from densities measured with a vibrating-tube densimeter. All the excess volumes present strong contractions when compared to those of n-alkanone + n-alkane systems.
Molar excess enthalpies HmE and VmE of the considered mixtures vary similarly. This may be attributed to interactional effects which prevail over structural effects.
Flory's theory has been applied to the systems under study. As expected, results for HmE are better when the difference in polarity of the components of the mixture decreases. VmE is often poorly represented.
  • Riesco, N; Villa, S; de la Fuente, IG; Gonzalez, JA; Cobos, JC; Thermodynamics of organic mixtures containing amines I. Excess molar volumes at 298.15 K for triethylamine or tributylamine plus n-alkane systems. Comparison with Flory results; Fluid Phase Equlibr, 202 (2) 2002 345-358
Excess molar volumes at 298.15 K and atmospheric pressure over the entire composition range for binary mixtures of triethylamine (TEA) or tributylamine (TBA) with n-hexane, n-octane, n-decane, n-decane, n-tetradecane, or n-hexadecane, or of TBA with n-dodecane are reported from densities measured with a vibrating-tube densimeter.
At equimolar composition, the excess molar volume for TEA + n-alkane systems increases up to heptane and then decreases, being negative for the larger alkanes. In the case of TBA mixtures, the excess molar volume increases regularly with the chain length of the alkane, and is negative when a shorter alkane is the second component. The negative values of the excess molar volumes indicate that the contribution from free volume effects to excess volume is predominant over the interactional contribution. For the investigated solutions, the Flory theory represents the dependence of the excess molar enthalpy and of the excess molar volume with the size of the n-alkane.
  • Villa, S; Gonzalez, JA; de la Fuente, Riesco, N; IG; Cobos, JC; Thermodynamics of organic mixtures containing amines. II. Excess molar volumes at 25 ºC for methylbutylamine plus alkane systems and eras characterization of linear secondary amine plus alkane mixtures; J Solut Chem, 32 (12) 2002 1019-1038
Excess molar volumes, at 25 ºC and atmospheric pressure for methylbutyl amine C n-hexane; + cyclohexane; + n-octane; n-decane; + n-dodecane; + n-tetradecane, or + n-hexadecane systems are reported from densities measured with a vibrating-tube densimeter. The excess functions, molar enthalpy, and volume, for linear secondary amine + n-alkane systems are discussed in terms of interactional and structural effects. In addition, these solutions, which include amines from dimethyl to dioctylamine, are studied in the framework of the ERAS model. The corresponding ERAS parameters are reported. The agreement between experimental data and ERAS results is good for excess enthalpies, excess Gibbs energies, and excess molar volumes. The larger discrepancies are found for the excess volumes when strong free-volume effects are present in the investigated mixtures. The variation with temperature of the thermodynamic properties is well described by ERAS.



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