Grupo Especializado en Termodinámica de los Equilibrios entre Fasesenglish versionGETEF emblema


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Año 1999

  • Gonzalez, JA; de la Fuente, IG; Cobos, JC; Proximity effects and cyclization in oxaalkanes plus CCl4 mixtures DISQUAC characterization of the Cl-O interactions. Comparison with Dortmund UNIFAC results; Fluid Phase Equilibr, 154 (1) 1999 11-31
Thermodynamic properties, vapor-liquid equilibria (VLE), molar excess Gibbs energies (GE), molar excess enthalpies (HE) and natural logarithms of activity coefficients at infinite dilution (ln γi) or partial molar excess enthalpies at infinite dilution (HiE,∞) 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 Lsing 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.
  • Gonzalez, JA; de la Fuente, IG; Cobos, JC; DISQUAC structure-dependent interaction parameters for mixtures containing sec-alkanols and benzene, toluene, or n-alkanones; Can J Chem-Rev Can Chim, 76 (10) 1999 1418-1428
Mixtures containing sec-alkanols and benzene, toluene, or n-alkanones are characterized in terms of DISQUAC by means of structure-dependent interaction parameters. The quasichemical (QUAC) interchange coefficients are independent of the size alcohol for a given organic solvent; while the dispersive (DIS) ones change with the size of the alcohol. This behaviour has been found for other many alcoholic solutions. DISQUAC represents well the thermodynamic properties of these mixtures: vapor-liquid equilibria, VLE, molar excess Gibbs energies, GE, and molar excess enthalpies, HE. So, the mean deviations between experimental and calculated results are about 2% for pressure, and 8% for HE. A Short comparison between DISQUAC results and those given by the Dortmund version of UNIFAC, the UNIQUAC association theory and other similar model is also presented. In the case of the Dortmund version of UNIFAC, poorer predictions are obtained for HE, as this property is more sensitive to molecular structure. Association theories provide better results because are used as correlation equations.
  • Gonzalez, JA; Carmona, J; de la Fuente, IG; Cobos, JC; DISQUAC predictions on thermodynamic properties of ternary and higher multicomponent mixtures. I. Results for total pressure measurements at isothermal conditions of ternary systems; Thermochim Acta, 326 (1-2) 1999 53-67
The ability of DISQUAC to represent vapor-liquid equilibria, VLE, particularly pressures for sets of (x1, x2) values at a given temperature, of ternary mixtures is investigated. Results are obtained using binary interaction parameters only, that is, ternary interactions are neglected.
At this end, a set of 39 ternary systems and of 98 related binaries is analyzed. The ternary mixtures treated are of widely different classes. They may be formed by only hydrocarbons; by one or two polar, but not self-associated, compounds and hydrocarbons; or by one or two alcohols and organic solvents, such as hydrocarbons, CCl4 or polar components.
Deviations for ternary and binary systems are similar. The mean relative standard deviation in pressure is 0.020 for the former, and 0.017 for the latter. This means that good predictions on VLE of ternary mixtures can be obtained, taking into account binary interactions only. Moreover, DISQUAC results are practically independent of the system considered, and are valid over a wide range of temperature. Poorer predictions are obtained for those solutions with a binary showing a miscibility gap.
It is also noteworthy that, in most of the cases, the interaction parameters needed are already available in the literature. Only for a few binary systems considered, the VLE data are correlated to obtain interchange coefficients which are later used to predict VLE of the related ternary.
For the binary mixtures, DISQUAC predicts correctly: the coordinates of azeotropes and excess Gibbs energies, GE.
A comparison between DISQUAC results and those obtained using different association models is also presented. DISQUAC and the UNIQUAC association theory yield similar predictions for ternary systems containing two alcohols and one n-alkane.
  • Gonzalez, JA; de la Fuente, IG; Cobos, JC; Thermodynamics of mixtures with strongly negative deviations from Raoult's law - Part 2. Application of the DISQUAC model to mixtures of CHCl3 or CH2Cl2 with oxaalkanes. Comparison with Dortmund UNIFAC results; PCCP Phys Chem Chem Phys, 1 (2) 1999 275-283
Binary mixtures of linear and cyclic oxaalkanes and CHCl3 or CH2Cl2 are characterized in the framework of the DISQUAC model. The interaction parameters for the corresponding O/Cl contacts are reported. The enthalpic quasichemical interchange coefficients are negative, as in other mixtures which also show strong negative deviations from Raoult's law. There are proximity effects on both dispersive and quasichemical interaction parameters of diethers and acetals. DISQUAC represents fairly well the thermodynamic properties examined: vapor-liquid equilibria (VLE), molar excess enthalpies (HE), molar excess heat capacities at constant pressure (CPE) or natural logarithms of activity coefficients at infinite dilution (ln γi). DISQUAC provides much better results than the Dortmund version of UNIFAC using the published geometrical and interaction parameters. From this comparison, it seems that one should distinguish, at least, between linear monoethers, polyethers or acetals. Each cyclic molecule should be treated separately. A short comparison between DISQUAC and the ideal associated solution theory is also included. Both models yield similar results.
  • Carmona, FJ; Gonzalez, JA; de la Fuente, IG; Cobos, JC; Thermodynamic properties of n-alkoxyethanols plus organic solvent mixtures. X. Liquid-liquid equilibria of systems containing 2-methoxyethanol, 2-(2-methoxyethoxy) or 2-(2-ethoxyethoxy)ethanol, and selected alkanes; J Chem Eng Data, 44 (5) 1999 892-895
Liquid-liquid equilibria (LLE) data are reported for 2-methoxyethanol + heptane, + methylcyclohexane, or + 2,2,4-trimethylpentane and for 2-(2-methoxyethoxy)ethanol + 2,2,4-trimethylpentane and 2-(2-ethoxyethoxy)ethanol + methylcyclohexane mixtures between 281.8 K and the upper critical solution temperatures (UCSTs). The coexistence curves were determined visually. They have a rather horizontal top and are skewed to the region of higher mole fractions of the alkoxyethanol, x1, for systems with 2-methoxyethanol, and to the region of lower x1 values for the mixtures including the other two hydroxyethers. The (x1, T) data were fitted to the equation T = Tc + k¦y-yc¦m where y = γ x1/{1 + x1(γ - 1)} and yc = γ x1c/{1 + x1c(γ - 1)}. Tc and x1c are the coordinates of the critical points fitted together with k, m, and alpha. Results are briefly discussed on the basis of the existence of inter- and intramolecular H-bonds as well as of dipole interactions, which occur in solutions containing hydroxyethers.
  • Carmona, FJ; Arroyo,  FJ; de la Fuente, IG; Gonzalez, JA; Cobos, JC; Excess molar volumes of methanol or ethanol plus n-polyethers at 298.15 K; Can J Chem-Rev Can Chim, 77 (10) 1999 1608-1616
Excess molar volumes VmE at 298.15 K and atmospheric pressure for methanol and ethanol + 2,5-dioxahexane, + 3,6-dioxaoctane, + 2,5,8-trioxanonane, + 3,6,9-trioxaundecane, + 5,8,11-trioxapentadecane, + 2,5,8,11-tetraoxadodecane, and + 2,5,8,11,14-pentaoxapentadecane have been obtained from densities measured with an Anton-Paar DMA 602 vibrating-tube densimeter. All the excess volumes are negative over the whole mole fraction range. The VmE curves are shifted to the region rich in the alkanol, increasing their asymmetry with the number of oxygen groups in the polyethers. Results seem to remark the predominant contribution of free volume effects on interactional effects, particularly when the ethers are of the type CH3-(O-CH2CH2)m-CH3. In the case of polyethers with longer n-alkyl chain ends, self-association of methanol and ethanol is more relevant. A short comparative study with results for mixtures with higher 1-alkanols and polyethers is also presented.



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