Grupo Especializado en Termodinámica de los Equilibrios entre Fasesenglish versionGETEF emblema


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Año 2001

  • Carmona, FJ; Bhethanabotla, VR; Campbell, SW; Gonzalez, JA; de la Fuente, IG; Cobos, JC; Thermodynamic properties of (n-alkoxyethanols plus organic solvents). XII. Total vapour pressure measurements for (n-hexane, n-heptane or cyclohexane+2-methoxyethanol) at different temperatures; J Chem Thermodyn, 33 (1) 2001 47-59
Total pressure measurements are reported for (n-hexane + 2-methoxyethanol) at T = (313.15 and 323.15) K, (n-heptane + 2-methoxyethanol) at T = 323.15 K, and (cyclohexane + 2-methoxyethanol) at T = (303.15, 313.15, and 323.15) K. Results were obtained by using a Van Ness type apparatus and were fitted with the five-parameter modified Margules equation by Barker's method. Measurements are represented to within an average absolute deviation of approximately 0.02 kPa. Mixtures show positive deviation from Raoult's law and show azeotropic behaviour at the temperatures considered in this work.
  • Domanska, U; Gonzalez, JA; Thermodynamics of mixtures containing a very strongly polar compound. Part I. Experimental phase equilibria (solid-liquid and liquid-liquid) for sulfolane+alkan-1-ols systems. Analysis of some mixtures including sulfolane in terms of disquac; PCCP Phys Chem Chem Phys, 3 (6) 2001 1034-1042
Equilibrium temperatures for liquid-liquid and solid-liquid transitions of systems containing sulfolane and propan-1-ol, butan-1-ol, octan-1-ol or tetradecan-1-ol were measured by a dynamic method. From butan-1-ol, the mixtures show an upper critical solution temperature, which increases with the length of the alcohol. It may attributed to a decreasing of the effective dipole moment of the alkan-1-ol which markedly decreases the interactions between unlike molecules. The coexistence curves become shifted to the high molar fractions of sulfolane in solutions with longer alkan-1-ols, probably due to size effects. Binary systems of sulfolane with cycloalkanes, n-alkanes, benzene or toluene, CCl4 or alkan-1-ols were analyzed in terms of a purely physical model, DISQUAC. The corresponding interaction parameters are reported. DISQUAC represents fairly well, over a rather wide range of temperature, a complete set of thermodynamic properties: liquid-liquid equilibria, LLE, solid-liquid equilibria, SLE, vapor-liquid equilibria, VLE, molar excess Gibbs energies, GE, molar excess enthalpies, HE and natural logarithms of activity coefficients at infinite dilution, ln γi. Deviations observed for LLE are typical for mean field theories as calculations are developed assuming that thermodynamic properties close to the critical points are analytical. Experimental data show that sulfolane may play the role of an almost inert diluent, because of the steric hindrance of its globular nature.
  • Serna, A; Villa, S; de la Fuente, IG; Gonzalez, JA; Cobos, JC; Excess molar volumes of binary mixtures of hexanol and polyethers at 25 ºC; J Solut Chem, 30 (3) 2001 253-261
Excess molar volumes VmE at 25 ºC and atmospheric pressure over the entire composition range for binary mixtures of 1-hexanol with n-polyethers: 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 are reported from densities measured with a vibrating-tube densimeter. Systems containing 2,5-dioxahexane, 2,5,8-trioxanonane, 2,5,8,11-tetraoxadodecane or 2,5,8,11,14-pentaoxapentadecane are characterized by VmE > 0, probably due to predominant positive contributions to VmE from the disruption of H bonds of 1-hexanol and to physical interactions. In contrast, mixtures with 3,6-dioxaoctane, 3,6,9-trioxaundecane. and 5,8,11-trioxapentadecane are characterized by VmE < 0, indicating that the negative contribution to VmE from interstitial accommodation is more important.
  • Gonzalez, JA; Riesco, N; de la Fuente, IG; Cobos, JC; Vergara, LA; Cocero, MJ; Thermodynamics of mixtures containing ethers. PART II - Isothermal x-y data for the ternary system MTBE plus methanol+1-butanol and for two constituent binaries: DISQUAC predictions on VLE of ternary mixtures containing tertiary-alkyl ethers and organic solvents; Thermochim Acta, 373 (2) 2001 161-171
VLE data at 298.15 K (x-y measurements, where x and y are the mole fractions in liquid and vapor phase, respectively) for methanol or 1-butanol + methyl tert-butyl ether (MTBE) and for MTBE + methanol + 1-butanol systems are reported. These data and those available on literature on VLE at isothermal conditions for ternary systems containing tertiary-alkyl ethers (MTBE. tert-amyl methyl ether (TAME)) and organic solvents (hydrocarbons and 1-alkanols) are analyzed in terms of DISQUAC. The model correctly predicts VLE of this type of mixtures using binary parameters only, i.e. neglecting ternary interactions. Results are independent of the mixture considered.
  • Gonzalez, JA; Cobos, JC; Carmona, FJ; de la Fuente, IG; Bhethanabotla, VR; Campbell, SW; Thermodynamics of mixtures containing alkoxyethanols - Part XV. DISQUAC characterization of systems of alkoxyethanols with n-alkanes or cyclohexane; PCCP Phys Chem Chem Phys, 3 (14) 2001 2856-2865
Binary mixtures of alkoxyethanols, CH3-(CH2)n-O-(CH2CH2O)mOH and n-alkanes or cyclohexane are characterized in terms of DISQUAC. The corresponding dispersive (DIS) and quasichemical (QUAC) interchange coefficients, Ceh,lDIS/QUAC for the (e,h) contacts (type e, -O-; type h, -OH) are given. In comparison with the values for 1-alkanol + monooxalkane systems, the proximity effects in CH3-(CH2)n-O-CH2-CH2-OH + n-alkane mixtures lead to an increase in the Ceh, lDIS and Ceh,lQUAC coefficients and to a decrease in Ceh,2DIS. For other hydroxyethers (3-methoxypropanol, 4-methoxybutanol), the Ceh,lQUAC (l =1, 2) coefficients approach those of 1-alkanol + monooxalkane mixtures with increasing separation between the -O- and -OH- groups. However, the Ceh,2DIS coefficient is still lower than in alcoholic solutions, indicating that proximity effects in the framework of DISQUAC remain. DISQUAC yields a consistent description of the vapor-liquid equilibria, VLE, and of liquid-liquid equilibria, LLE. Good results are obtained for azeotropic data. The coordinates of the critical points are represented over a reasonable range of composition and temperature. Excess molar enthalpies HmE and the excess molar heat capacity at constant pressure, CPmE, are well reproduced. The typical large deviations for properties at infinite dilution, excess molar partial enthalpies, HmE,∞ and natural logarithms of activity coefficients, ln γi, of the associated compound are found. Thermodynamic properties of alkoxyethanol + alkane mixtures are determined by the self-association of the polar compound via both inter- and intramolecular H-bonds, as well as by dipole-dipole interactions between alkoxyethanol molecules. These interactions are analyzed in terms of the effective dipole moments (μ) and are more important than in 1-alkanol + alkane mixtures. The dipole-dipole interactions in systems with alkoxyethanols decrease along a homologous series, and are enhanced by the presence of two ether atoms. Intramolecular H-bonds are more relevant than the intermolecular H-bonds and become weakened with the separation between the -O- and -OH groups of the hydroxyethers.
  • Gonzalez, JA; Carmona, J; Riesco, N; de la Fuente, IG; Cobos, JC; DISQUAC predictions on thermodynamic properties of ternary and higher multicomponent mixtures. II. Results for HE of ternary mixtures containing nonpolar components, or one polar compound, two polar compounds, or one alcohol and hydrocarbons, or CCl4; Can J Chem-Rev Can Chim, 79 (10) 2001 1447-1459
The ability of the DISQUAC model for predicting excess enthalpies (HE) of ternary systems on the basis of binary parameters only, i.e., neglecting ternary interactions is analyzed. At this end, DISQUAC results for a set of 95 ternary systems are examined. The solutions studied are formed by only hydrocarbons (or CCl4); or by one polar compound (not alcohols) and two hydrocarbons (or CCl4); or by two polar compounds (not alcohols) and one hydrocarbon (or CCl4); or by one alcohol and two hydrocarbons (or CCl4). Most of the HEs analyzed are endothermic, and valid at 298.15 K and atmospheric pressure. The mean deviation between experimental values and DISQUAC results is 5.5% for the ternary systems and 6.5% for the constituent binaries (181 mixtures). The interaction parameters used are valid for the description of thermodynamic properties of binary systems: vapor-liquid equilibria (VLE), liquid-liquid (LLE), and solid-liquid equilibria (SLE), HE and excess heat capacities at constant pressure (CPE), as well as HE and VLE of ternary solutions. Predictions are, in most of the cases, independent of the mixture compounds, or the number of groups present in the system. Larger deviations underline typical shortcomings of the group contributions methods (e.g., Patterson's effect; branching). Note that results for the ternaries and for the constituent binaries are of the same order. This is not the case for the Dortmund version of UNIFAC. The mean deviations obtained using this model are 10.5% and 14% for the ternary and binary mixtures, respectively. Results from other models (original UNIFAC, Flory's theory, Nitta-Chao, UNIQUAC association model) for a number of systems are also compared to those obtained using DISQUAC.
  • Villa, S; Riesco, N; de la Fuente, IG; Gonzalez, JA; Cobos, JC; Thermodynamics of mixtures with strongly negative deviations from Raoult's law. Part 5. Excess molar volumes at 298.15 K for 1-alkanols plus dipropylamine systems: characterization in terms of the ERAS model; Fluid Phase Equilibr, 190 (1-2) 2001 113-125
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 dipropylamine are reported 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 system involving methanol, characterized by the most negative VmE. For the remainder mixtures, VmE at equimolar composition, is approximately constant. The VmE curves are nearly symmetrical.
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 + dipropylamine system.
  • Domanska, U; Szurgocinska, M; Gonzalez, JA; Thermodynamics of binary mixtures containing organic carbonates Part XI. SLE measurements for systems of diethyl carbonate with long n-alkanes: comparison with DISQUAC and modified UNIFAC predictions; Fluid Phase Equilibr, 190 (1-2) 2001 15-31
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) is investigated. Six sets of the SLE temperatures for diethyl carbonate + n-alkane (octadecane, eicosane, docosane, tetracosane, hexacosane, octacosane) systems have been measured by a dynamic method from 278.65 K to the melting point of the long chain n-alkane. The 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 0.31 to 0.34 K and depend on the particular equation used.
The SLE curves are usually well predicted by DISQUAC and modified UNIFAC models with average standard deviation of < 1.35 K.



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