Grupo Especializado en Termodinámica de los Equilibrios entre Fasesenglish versionGETEF emblema


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Año 2000

  • Gonzalez, JA; de la Fuente, IG; Cobos, JC; Thermodynamics of mixtures with strongly negative deviations from Raoult's Law - Part 4. Application of the DISQUAC model to mixtures of 1-alkanols with primary or secondary linear amines. Comparison with Dortmund UNIFAC and ERAS results; Fluid Phase Equilibr, 168 (1) 2000 31-58
Binary mixtures of l-alkanols with primary or secondary linear amines have been characterized in the framework of DISQUAC, The interaction parameters for the corresponding OH/NH2, and OH/NH contacts are reported. DISQUAC represents fairly well the thermodynamic properties examined, which are critically evaluated: vapor-liquid equilibria (VLE), molar excess Gibbs energies (GE) and molar excess enthalpies (HE). For example, polyazeotropy of the methanol + diethylamine mixture is well reproduced. The methanol + ammonia system can be treated similarly to other l-alkanols + primary amine systems (i.e., ammonia is assumed, as in a previous work, to be a primary amine without C atoms). The results are discussed in terms of effective dipole moments. The information derived from the concentration-concentration structure factors is briefly analyzed. DISQUAC provides better results than the Dortmund version of UNIFAC using the published geometrical and interaction parameters. Particularly, DISQUAC improves results on GE and for systems containing methanol, DISQUAC results on HE are also compared to those obtained from the ERAS model. For systems containing primary amines, parameters available in literature were used along calculations. In the case of methanol + diethylamine and 1-alkanols + dibutylamine mixtures, new ERAS parameters are reported in this work. The mean standard deviations for HE Obtained using DISQUAC and ERAS, are 151 and 216 J mol-1, respectively. DISQUAC also improves results on GE, while ERAS describes properly the available excess volume (VE) data.
  • Gonzalez, JA; Carmona, FJ; Riesco, N; de la Fuente, IG; Cobos, JC; Thermodynamics of mixtures containing ethers. Part I. DISQUAC characterization of systems of MTBE, TAME or ETBE with n-alkanes, cyclohexane, benzene, alkan-1-ols or alkan-2-ols. Comparison with Dortmund UNIFAC results; PCCP Phys Chem Chem Phys, 2 (11) 2000 2587-2597
Binary mixtures of methyl tert-butyl ether (MTBE), tert-amyl methyl ether (TAME) or ethyl tert-butyl ether (ETBE) and n-alkanes, cyclohexane, benzene, alkan-1-ols or alkan-2-ols are characterized in terms of DISQUAC. The corresponding interaction parameters are reported. Systems with isomeric monooxaalkanes (linear or branched) and n-alkanes are characterized by the same QUASICHEMICAL (QUAC) interaction parameters. The DISPERSIVE (DIS) parameters are larger for those mixtures with tertiary-alkyl ethers. It is remarkable that in systems with alkan-1-ols, the first and third QUAC parameters are kept constant. The same trend is observed in many other alcoholic solutions previously studied. Mixtures with alkan-1-ols or alkan-2-ols differ only in the DIS parameters, which are larger for those systems with alkan-2-ols. Vapour-liquid equilibria (VLE), molar excess enthalpies (HE), logarithms of activity coefficients at infinite dilution (ln γi) or solid-liquid equilibria (SLE) are correctly described by DISQUAC. HE values of ternary systems, including compounds considered in this work, are also represented by DISQUAC using binary parameters only. A complete comparison between DISQUAC calculations and those obtained from the Dortmund version of UNIFAC using the parameters available in the literature is included. DISQUAC improves results, except for VLE of mixtures including n-alkanes, which are slightly better represented by UNIFAC. This may be attributed to the fact that the empirical combinatorial term used in UNIFAC is more suitable, particularly for those systems with components very different in size. DISQUAC also improves results obtained from the ERAS model for HE of alcoholic solutions (where association is expected). Thermodynamic properties are analysed in terms of the effective dipole moments (μ). The importance of structural effects is remarked.
  • Carmona, FJ; Gonzalez, JA; de la Fuente, IG; Cobos, JC; Bhethanabotla, VR; Campbell, SW; Thermodynamic properties of n-alkoxyethanols plus organic solvent mixtures. XI. Total vapor pressure measurements for n-hexane, cyclohexane or n-heptane+2-ethoxyethanol at 303.15 and 323.15 K; J Chem Eng Data, 45 (4) 2000 699-703
Total vapor pressures at 303.15 and 323.15 K were measured for binary systems of n-hexane, cyclohexane, or n-heptane + 2-ethoxyethanol. Measurements were made with a Van Ness type apparatus and were fitted to the modified Margules equation using Barker's method. The five-parameter modified Margules equation represents the measurements to within an average absolute deviation of approximately 0.01 kPa. The measurements reveal positive deviations from Raoult's law. Mixtures with n-heptane and cyclohexane show azeotropic behavior at both temperatures.
  • Arroyo, FJ; Carmona, FJ; de la Fuente, IG; Gonzalez, JA; Cobos, JC; Excess molar volumes of binary mixtures of 1-heptanol or 1-nonanol with n-polyethers at 25 ºC; J Solut Chem, 29 (8) 2000 743-756
Excess molar volumes VmE at 25 ºC and atmospheric pressure over the entire composition range for binary mixtures of 1-heptanol with 2,5-dioxahexane, 2,5,8-trioxanonane, 5,8,11-trioxapentadecane, 2,5,8,11-tetraoxadodecane, or 2,5,8,11, 14-pentaoxapentadecane, and mixtures of 1-nonanol with 2,5-dioxahexane, 3,6-dioxaoctane, 2,5,8-trioxanonane, 3,6,9-trioxaundecane, 5,8,11-trioxapentadecane, 2,5,8,11-tetraoxadodecane, or 2,5,8,11,14-pentaoxapentadecane are reported from densities measured with a vibrating-tube densimeter. VmE curves are nearly symmetrical at about 0.5 mole fraction. Excess molar volumes are usually positive, indicating predominance of positive contributions to VmE from the disruption of H bonds of alcohols and from physical interactions. When chain lengths of both components of the mixture are increased, the contribution from interstitial accommodation appears to be sufficiently negative, such that VmE becomes negative (e.g., 1-nonanol + 5,8,11-tetraoxapentadecane).
  • Gonzalez, JA; de la Fuente, IG; Cobos, JC; Thermodynamics of mixtures with strongly negative deviations from Raoult's law. Part 3. Application of the DISQUAC model to mixtures of triethylamine with alkanols. Comparison with Dortmund UNIFAC and ERAS results; Can J Chem-Rev Can Chim, 78 (10) 2000 1272-1284
Binary mixtures of triethylamine (TEA) and alkanols have been investigated in the framework of DISQUAC. The systems are built by three contacts: aliphatic-hydroxyl, aliphatic-nitrogen, and hydroxyl-nitrogen. The corresponding interaction parameters are reported and discussed. The former are avalilable in the literature but were modified (particularly the third dispersive (DIS) and quasichemical (QUAC) interchange coefficients) for sec- and tert-alkanols + n-alkanes using recent data on excess heat capacities at constant pressure (CPE) for systems of these alkanols with n-heptane. The interaction parameters for aliphatic-nitrogen contacts are purely dispersive. The structure dependence of the DIS and QUAC interchange coefficients of the hydroxyl-nitrogen contacts in 1-alkanols + TEA systems is similar to that found in other solutions previously investigated. The QUAC interchange coefficients remain constant from ethanol and are also valid for 2-alkanols and tert-butanol. Methanol behaves differently. A short discussion in terms of effective dipole moments is also included. DISQUAC represents well the thermodynamic properties examined: vapor-liquid equilibria (VLE), molar excess Gibbs energies (GE) and molar excess enthalpies (HE). DISQUAC provides better results than the Dortmund version of UNIFAC using the published geometrical and interaction parameters. ERAS parameters for 1-alkanols + TEA systems are also reported. Interactions between unlike molecules are stronger for solutions with methanol or ethanol. DISQUAC improves ERAS results on HE, while both models give similar results for GE. However, ERAS needs an specific parameter, with unknown temperature-dependence, to describe properly GE. The main advantage of ERAS is its ability to provide information on VE. Its main limitation is that can be only applied to those systems where association is expected. DISQUAC, a purely physical model, can be applied to any type of binary mixture, as it is followed from this and previous studies.
  • Villa, S; Riesco, N; Carmona, FJ; de la Fuente, IG; Gonzalez, JA; Cobos, JC; Temperature dependence of excess properties in alcohols plus ethers mixtures. I. Excess molar volumes of 1-propanol or 1-hexanol plus ethers at 318.15 K; Thermochim Acta, 362 (1-2) 2000 169-177
Excess molar volumes VmE at 318.15 K and atmospheric pressure for 1-propanol or 1-hexanol + dibutyl ether, 1-propanol or 1-hexanol + 2,5-dioxahexane, 1-propanol or 1-hexanol + 2,5,8-trioxanonane, 1-propanol or 1-hexanol + 3,6,9-trioxaundecane and 1-propanol or 1-hexanol + 5,8,11-trioxapentadecane, 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, except for the systems 1-propanol + 2,5,8-trioxanonane, which is S-shaped, and for 1-hexanol + 2,5-dioxahexane or 1-hexanol + 2,5,8-trioxanonane which are positive over the whole mole fraction range. For the systems with 1-propanol the VmE curves are shifted to the region rich in the alkanol, increasing their asymmetry with the number of oxygen groups in the ether. For 1-hexanol systems the VmE curves are symmetrical. This behaviour can be attributed to free volume effects.
The sign of dVmE/dT is discussed. Systems with 1-propanol are characterized by dVmE/dT > 0 which may be due to the more self-associated character of the alcohol. In solutions with 1-hexanol, the sign of dVmE/dT depends on the ether considered, i.e. on the balance between the interactional and structural contributions. So, if the latter are more important, then dVmE/dT > 0.
Results remark the differences between systems containing n-alkanols and monoethers or polyethers.
  • Riesco, N; Villa, S; Gonzalez, JA; de la Fuente, IG; Cobos, JC; Thermodynamic properties of n-alkoxyethanols plus organic solvent mixtures - XIII. Application of the Flory theory to 2-methoxyethanol plus n-alkoxyethanols systems; Thermochim Acta, 362  (1-2) 2000 89-97
The Flory theory has been applied to the following binary mixtures: 2-methoxyethanol (2ME) + 2-ethoxyethanol (2EE), or + 2-butoxyethanol (2BE), and + 2-(2-methoxyethoxy)ethanol (22MEE), 2-(2-ethoxyethoxy)ethanol (22EEE), or + 2-(2-buthoxyethoxy)ethanol (22BEE).
For pure compounds, the coefficients of thermal expansion α and isothermal compressibility κT were estimated in order to compute the Flory characteristic parameters, pressure pi* and volume vi*.
For each mixture, the energetic parameter χ12was fitted to excess enthalpy data HE at 298.15 K and used to predict correctly the corresponding excess volume VE. The variation of χ12 versus the numberof C atoms + -O- groups in alkoxyethanols is similar to that found previously for 1-alkanol mixtures.
  • Martinez, R; Gonzalez, JA; de la Fuente, IG; Cobos, JC; Thermodynamic properties of n-alkoxyethanols plus organic solvent mixtures. XIV. Liquid-liquid equilibria of systems containing 2-(2-ethoxyethoxy)ethanol and selected alkanes; J Chem Eng Data, 45 (6) 2000 1036-1039
Liquid-liquid equilibria (LLEs) data are reported for 2-(2-ethoxyethoxy)ethanol + hexane, heptane, octane, decane, dodecane, and hexadecane mixtures between 274.5 K and the upper critical solution temperatures (UCSTs). The coexistence curves were determined visually. They have a rather horizontal top, and their symmetry depends on the size of the alkane. For systems with dodecane or hexadecane, they are skewed to the region of higher mole fractions of 2-(2-ethoxyethoxy)ethanol. An opposite behavior is observed when hexane or heptane is involved. The (x1, T) data were fitted to the equation T = Tc + k|y-yc|m where y = α x1/[1 + x1(α - 1)] and yc = α x1c/[1 + x1c(α - 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.



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