Grupo Especializado en Termodinámica de los Equilibrios entre Fasesenglish versionGETEF emblema


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Año 2003

  • Villa, S; Riesco, N; de la Fuente, IG; Gonzalez, JA; Cobos, JC; Thermodynamics of mixtures with strongly negative deviations from Raoult's law. VII. Excess molar volumes at 25 ºC for 1-alkanol plus N-methylbutylamine systems - Characterization in terms of the ERAS model; J Solut Chem, 32 (2) 2003 179-194
Excess molar volumes, VmE, at 25 ºC 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-methylbutylamine are reported. They are calculated from densities measured with a vibrating-tube densimeter. All the excess volumes are large and negative over the entire composition range. This indicates strong interactions between unlike molecules, which are greatest for the system involving methanol, characterized by the most negative VmE. For the other solutions, VmE at equimolar composition, is approximately the same. The VmE curves vs. mole fraction are nearly symmetrical. The ERAS model is applied to 1-alkanol + N-methylbutylamine, and 1-alkanol + diethylamine systems. The ERAS parameters confirm that the strongest interactions between unlike molecules are encountered in solutions with methanol. The model consistently describes VmE and excess molar enthalpies HmE of the mixtures studied.
  • Domanska, U; Gonzalez, JA; Solid-liquid and liquid-liquid equilibria for 1,3,5-trioxane, or 1,4,7,10,13,16-hexaoxacyclooctadecane plus selected n-alkane mixtures - Analysis in terms of DISQUAC; Fluid Phase Equilibr, 205 (2) 2003 317-338
Solid-liquid and liquid-liquid equilibrium temperatures for mixtures of 1,3,5-trioxane, or 1,4,7,10,13,16-hexaoxacyclooctadecane with n-heptane, or with n-tridecane, or with n-hexadecane are reported. The equilibrium temperatures were measured by a dynamic method. Mixtures with n-tridecane, or n-hexadecane show a eutectic point. 1,4,7,10,13,16-Hexaoxacyclooctadecane present a transition point in solid phase, which depends on the solvent. Dipole-dipole interactions are stronger in solutions with 1,3,5-trioxane.
Mixtures were investigated in terms of DISQUAC and the corresponding interaction parameters are given. The model describes in the correct range of temperature and composition the coordinates of the eutectic and critical points.
The influence of proximity effects and cyclization on the interaction parameters is discussed. So, proximity effects are found to be important for interaction parameters of systems involving crown ethers. Departures from the observed behavior of the interaction parameters for solutions with more simple oxaalkanes are ascribed to the existence of liquid-liquid equilibria in the studied solutions.
  • Gonzalez, JA; Villa, S; Riesco, N; de la Fuente, IG; Cobos, JC; Thermodynamics of mixtures containing alkoxyethanols: Part XVII - ERAS characterization of alkoxyethanol plus alkane systems; Can J Chem-Rev Can Chim, 81 (4) 2003 319-329
Alkoxyethanol + alkane systems have been examined in the framework of the ERAS model. An exact expression for the molar excess heat capacity at constant pressure, CPE, of solutions formed by a self-associated compound and an inert solvent has been derived. The CPE and the molar excess enthalpies (HE) and excess volumes (VE), as well as the molar enthalpies of vaporization of the pure alkoxyethanols, are represented accurately by ERAS. The calculated curves for HE and VE are skewed towards high mole fractions of the alkane. The experimental curves are more symmetrical. The opposite behaviour is observed for CPE in solutions with 2-ethoxyethanol, 2-propoxyethanol, or 2-butoxyethanol. The differences between the experimental and theoretical values arise because ERAS does not properly take into account the enhanced dipole-dipole interactions due to the formation of intramolecular H-bonds in alkoxyethanols. As in previous applications, ERAS cannot simultaneously represent molar excess Gibbs energies and liquid-liquid equilibria. DISQUAC, a purely physical theory, improves ERAS predictions for HE (except at high temperatures and pressures) and for CPE. Liquid-liquid equilibria are also described more consistently. The self-association of alkoxyethanols via intramolecular H-bonds and the strong dipole-dipole interactions lead to values of the self-association enthalpy and of the adjustable parameter of the physical contribution to HE and VE that are higher than those of the homomorphic 1-alkanols. In contrast, the equilibrium constants are lower. There is good agreement between the partial molar excess enthalpies at 298.15 K and infinite dilution of 2-alkoxyethanol in 2-alkoxyethanol(1) + n-heptane(2) mixtures and the values of the self-association enthalpies.
  • Riesco, N; Gonzalez, JA; Villa, S; de la Fuente, IG; Cobos, JC; Thermodynamics of organic mixtures containing amines - III: Molar excess volumes at 298.15 K for tripropylamine plus n-alkane systems - Application of the Flory theory to N,N,N-trialkylamine plus n-alkane mixtures; Phys Chem Liq, 41 (3) 2003 309-321
Molar excess volumes at 298.15 K and atomospheric pressure for tripropylamine + n-hexane, + n-octane, + n-decane, + n-dodecane or + n-hexadecane systems determined from densities measured with an Anton-Paar DMA 602 vibrating-tube densimeter are reported. N,N,N-trialkylamihe + n-alkane systems have been studied using the Flory theory. Better results on excess enthalpies are obtained when the difference in size between the mixture components is large.
The dependence of the excess volume at equimolar composition with the length of the n-alkane is correctly described. The simultaneous analysis of the experimental excess volumes and of the excess enthalpies reveal that free volume effects are important in systems formed by triethylamine or tripropylamine and longer alkanes, as well as in those involving tripropylamine or tributylamine and the shorter alkanes.
The Patterson effect is present in the studied mixtures. The more globular amines, triethylamine, tripropylamine or tributylamine are order breakers of the longer alkanes. The amines of very large size, e.g., tridodecylamine, show an ordered structure.
  • Carmona, FJ; Gonzalez, JA; Villa, S; de la Fuente, IG; Cobos, JC; Thermodynamic properties of n-alkoxyethanols plus organic solvent mixtures - XVI. Excess molar volumes at 298.15 K for 2-alkoxyethanol plus n-polyether systems; Thermochim Acta, 403 (2) 2003 223-229
Excess molar volumes (VmE) at 298.15 K and atmospheric pressure for 2-methoxyethanol or 2-butoxyethanol + 2,5-dioxahexane, + 2,5,8-trioxanonane, + 3,6,9-trioxaundecane, + 5,8,11-trioxapentadecane, or +2,5,8,11,14-pentaoxapentadecane, or for 2-ethoxyethanol + 2,5,8-trioxanonane, + 3,6,9-trioxaundecane, or + 5,8,11-pentaoxapentadecane have been obtained from densities measured with and Anton-Paar DMA 602 vibrating-tube densimeter. They are usually small in absolute value. It is due to a compensation between positive and negative contributions to the excess molar volume. For example, free volume effects present in solutions with the pentaether are compensated by the positive contribution to VmE from the rupture of dipole-dipole interactions between ether molecules.
  • Gonzalez, J; Domanska, U; Lachwa, J; Thermodynamics of binary mixtures containing a very strongly polar compound - Part 3: DISQUAC characterization of NMP plus organic solvent mixtures,  Can J Chem-Rev Can Chim, 81 (12) 2003 1415-1461
Binary mixtures of 1-methyl pyrrolidin-2-one (NMP) with alkanes, benzene, toluene, 1-alkanol, or 1-alkyne have been investigated in the framework of the DISQUAC model. The reported interaction parameters change regularly with the molecular structure of the mixture components. The model consistently describes a set of thermodynamic properties, including liquid-liquid equilibria, vapor-liquid equilibria, solid-liquid equilibria, and molar excess enthalpies. A brief comparison of the DISQUAC results and those obtained from the UNIFAC and ERAS models is presented. The experimental excess enthalpies are better represented by DISQUAC than by UNIFAC because this quantity strongly depends on molecular structure. For NMP + alkane mixtures, the liquid-liquid equilibria data are also better represented by DISQUAC, while UNIFAC more accurately describes the vapor-liquid equilibria measurements at temperatures close to the critical point. This result suggests that a mean field theory is not able to represent simultaneously, with the same set of interaction parameters, liquid-liquid and vapor-liquid equilibria at the mentioned temperatures. ERAS fails when treating mixtures with 1-alkanols. This has been attributed to the strong dipole-dipole interactions between NMP molecules, characteristic of the investigated systems. Mixture structure is briefly studied in terms of the concentration-concentration structure factor.
  • Sporzynski, A; Szurgocinska, M; Domanska, U; Gonzalez, JA; Thermodynamics of mixtures containing organic carbonates. 14. Excess molar Gibbs energies for 1-hexanol plus dimethyl or diethyl carbonate systems at 353.15 and 363.15 K. Comparison with ERAS results; Ind Eng Chem Res, 42 (19) 2003 4382-4388
Vapor-liquid equilibria (P-x measurements) at 353.15 and 363.15 K for 1-hexanol + dimethyl carbonate or + diethyl carbonate are determined by an ebullometric method. The data are reduced using Barker's method. All of the systems present positive deviations from Raoult's law. Mixtures are studied in the framework of the ERAS model assuming that 1-alkanols are the only self-associated compounds in the investigated solutions. According to the high HE (excess molar enthalpy) values of 1-alkanol + linear organic carbonate systems, the model predicts a weak cross association between the mixture components. The deviations between the experimental GE (excess molar Gibbs energy) and HE values and the ERAS results can be ascribed to the existence of strong polar interactions between carbonate molecules, not described properly by the model.
  • Gonzalez, JA; Villa, S; Riesco, N; de la Fuente, IG; Cobos, JC; Thermodynamics of mixtures containing a very strongly polar compound: IV - Application of the DISQUAC, UNIFAC and ERAS models to DMSO plus organic solvent systems; Phys Chem Liq, 41 (6) 2003 583-597
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 HE. 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.



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