Grupo Especializado en Termodinámica de los Equilibrios entre Fasesenglish versionGETEF emblema


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Año 2004

  • Carmona, FJ; Gonzalez, JA; de la Fuente, IG; Cobos, JC; Thermodynamic properties of n-alkoxyethanols plus organic solvent mixtures - XVIII. Excess volumes at 298.15 K for 2-(2-alkoxyethoxy)ethanol plus n-polyether; Thermochim Acta, 409 (2) 2004 169-175
Excess molar volumes, VE at 298.15 K and atmospheric pressure for 2-(2-methoxyethoxy)ethanol or 2-(2-butoxyethoxy)ethanol +2,5-dioxahexane, +2,5,8-trioxanonane, +3,6,9-trioxaundecane, +5,8,11-trioxapentadecane, and +2,5,8,11,14-pentaoxapentadecane, or for 2-(2-ethoxyethoxy) ethanol + 2,5,8-trioxanonane, +3,6,9-trioxaundecane, and +5,8,11-pentaoxapentadecane have been obtained from densities measured with and Anton-Paar DMA 602 vibrating-tube densimeter.
The VE values are usually negative indicating that interactions between unlike molecules are predominant over other effects. The investigated mixtures behave similar to those with 2-methoxyethanol, 2-ethoxyethanol or 2-butoxyethanol and the same oxaalkanes.
  • Villa, S; Riesco, N; de la Fuente, IG; Gonzalez, JA; Cobos, JC; Thermodynamics of mixtures with strongly negative deviations from Raoult's law. Part 8. Excess molar volumes at 298.15 K for 1-alkanol + isomeric amine (C6H15N) systems - Characterization in terms of the ERAS model; Fluid Phase Equilibr, 216 (1) 2004 123-133
Excess molar volumes, VE, 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 hexylamine (HxA) and of 1-propanol, 1-pentanol, 1-hexanol, 1-heptanol and 1-octanol with triethylamine (TEA) 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. These interactions are stronger for the solutions with methanol or ethanol. The corresponding values of the molar excess enthalpies, HE, and of the molar excess internal energies confirm this point.
At equimolar composition, VE values for the 1-alkanol + HxA systems behave similarly to those of other systems previously investigated such as 1-alkanol + dipropylamine (DPA), + dibutylamine, or + methyl butylamine. For these mixtures, the main contribution to the VE seems to be due to the interactional term. In contrast, packing effects are much more important in 1-alkanol + TEA mixtures.
VE and HE of the studied solutions are consistently described by the ERAS model. The ERAS parameters point out that the strongest interactions between unlike molecules are encountered in the solutions including methanol.
  • Gonzalez, JA; Thermodynamics of mixtures containing a very strongly polar compound: V - Application of the extended real associated solution model to 1-alkanol plus secondary amide mixtures; Phys Chem Liq, 42 (2) 2004 159-172
The extended real associated solution (ERAS) model is applied to 1-alkanol + secondary amide mixtures. The amides considered are: N-methylformamide (NMF), N-methylacetamide (NMA) and 2-pyrrolidone (2-PY). The ERAS parameters for pure amides and for the mixtures are reported. For pure amides, our enthalpy of association is constant (-25 kJ mol-1) and is in good agreement with values obtained using different method, e.g., the optimized potentials for liquid simulations. For the mixtures, the ERAS parameters change regularly with molecular structure of the components. In general, ERAS describes quite well molar excess enthalpies and molar excess volumes. In contrast, the model cannot represent molar excess Gibbs energies. Discrepancies between experimental and calculated values are ascribed to: (a) large combinatorial entropies as in methanol +NMA, or +2-PY systems; (b) association effects are less important than dipole-dipole interactions between amide molecules.
  • Mozo, I; Gonzalez, JA; de la Fuente, IG; Cobos, JC; Thermodynamics of mixtures containing ethers. Part III. Liquid-liquid equilibria for 2,5,8,11-tetraoxadodecane or 2,5,8,11,14-pentaoxapentadecane plus selected n-alkanes; J Chem Eng Data, 49 (4) 2004 1091-1094
Liquid-liquid equilibria temperatures for systems of 2,5,8,11-tetraoxadodecane with decane and tetradecane and of 2,5,8,11,14-pentaoxapentadecane with heptane, octane, and tetradecane have been measured between 264.85 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. For a given alkane, the UCST is higher for mixtures containing the pentaether. This reveals that dipole-dipole interactions between oxaalkane molecules are stronger in such solutions.
  • Gonzalez, JA; Cobos, JC; de la Fuente, IG; Thermodynamics of liquid mixtures containing a very strongly polar compound - Part 6. DISQUAC characterization of N,N-dialkylamides; Fluid Phase Equilibr, 224 (2) 2004 169-183
Systems of N,N-di(n-alkylamides) (hereafter, N,N-dialkylamides) with alkane, benzene, toluene, 1-alkanol or 1-alkyne have been investigated in the framework of the DISQUAC model. The corresponding interaction parameters are reported. They change regularly with the molecular structure of the mixture components. This variation is similar to those encountered when treating other systems in terms of DISQUAC. The model describes consistently a whole set of thermodynamic properties: liquid-liquid equilibria (LLE), vapor-liquid equilibria (VLE), solid-liquid equilibria (SLE), molar excess Gibbs energies (GE), molar excess enthalpies (HE), molar excess heat capacities at constant pressure (CPE), partial molar excess properties at infinite dilution, enthalpies and heat capacities. The model also provides good results for the Kirkwood-Buff integrals and for the linear coefficients of preferential solvation. For ternary systems, DISQUAC predictions on VLE and HE, obtained using binary parameters only, are in good agreement with the experimental data. A short comparison between DISQUAC and Dortmund UNIFAC results is shown. DISQUAC improves UNIFAC results on HE and CPE, magnitudes which strongly depend on the molecular structure. The investigated mixtures behave similarly to those characterized by thermodynamic properties which arise from dipolar interactions. Association/solvation effects do not play, as a whole, an important role in the studied systems. This may explain that the ERAS model fails when representing the thermodynamic properties of dimethy/formamide + 1-alkanol mixtures.
  • Gonzalez, JA; Cobos, JC; de la Fuente, IG; Thermodynamics of binary mixtures containing N-alkylamides; J Mol Liq, 115 (2-3) 2004 93-103
N-alkylamide + organic solvent mixtures have been investigated in the framework of a purely physical theory [dispersive-quasichemical (DISQUAC)]. The amides considered are n-methylformamide (NMF), n-methylacetamide (NMA), n-ethylacetamide (NEA), n-methylpropanamide (NMPA), 2-pyrrolidone and caprolactam. The solvents are alkanes, benzene, toluene or 1-alkanols. The DISQUAC interaction parameters are reported. The model describes consistently thermodynamic properties such as vapor-liquid equilibria (VLE), excess molar Gibbs energies, GmE, and excess molar enthalpies, HE, solid-liquid equilibria (SLE), or the concentration -concentration structure factor, Scc(0). DISQUAC improves results from other models, such as the extended real associated solution model (ERAS) or UNIFAC. Interactions present in the studied mixtures are discussed. Solutions with alkanes are characterized by strong dipole-dipole interactions between amide molecules. n-Methylformamide + aromatic compound mixtures behave similarly to associated systems. The heterocoordination observed in some solutions involving methanol where interactions between like molecules are almost cancelled by interactions between unlike molecules may partially be ascribed to size effects. For other alcoholic solutions, the ability of the alcohol for the breakage of the amide-amide interactions is prevalent over solvation effects.
  • Gonzalez, JA; Mozo, I; de la Fuente, IG; Cobos, JC; DISQUAC predictions on thermodynamic properties of ternary and higher multicomponent mixtures. 3. Results for HE of ternary mixtures containing one alcohol, one polar compound, and one hydrocarbon or two alcohols and one hydrocarbon or a polar compound, or three alkanols; Ind Eng Chem Res, 43 (23) 2004 7622-7634
DISQUAC predictions on molar excess enthalpies, HE, are shown for a set of 67 ternary mixtures formed by one alcohol, one active compound (not self-associated), and one hydrocarbon; two alkanols and one hydrocarbon; two alkanols and one polar compound; or three alkanols. DISQUAC provides reliable predictions on HE (approximate to 8%) for the ternary mixtures considered using binary interaction parameters only, i.e., neglecting ternary interactions. Differences between experimental results and theoretical calculations are of the same order for the ternary mixtures and for the constituent binaries. On the other hand, predictions are practically independent of the mixture compounds or of the number of contacts present in the solution. The poorer results are obtained for systems with a binary that shows strongly negative deviations from Raoult's law. A systematic comparison between DISQUAC results and those from the Dortmund UNIFAC model is presented. DISQUAC improves UNIFAC predictions, as well as those from ERAS for 1-alkanol + oxaalkane + alkane mixtures. More complex association models yield results that are similar to those from DISQUAC. Therefore, DISQUAC should. be applied when the interaction parameters used are available. The interaction parameters used are valid for the description of the thermodynamic properties of binary mixtures (vapor-liquid, solid-liquid, and liquid-liquid equilibria, HE, and the molar excess heat capacity at constant pressure, (CPE) as well as for predictions on vapor-liquid equilibria, HE, and CPE for ternary mixtures.



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