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Año 1999

- Gonzalez, JA; de la Fuente, IG; Cobos, JC; Proximity effects and
cyclization in oxaalkanes plus CCl
_{4}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 (G^{E}), molar
excess
enthalpies (H^{E}) and
natural logarithms of activity
coefficients at
infinite dilution (ln γ_{i}^{∞}) or partial molar
excess
enthalpies at infinite dilution (H_{i}^{E,∞})
of
mixtures of
oxaalkanes, Linear or cyclic monoethers, diethers or acetals, and CCl_{4}
are studied in the framework of DISQUAC. The oxygen/CCl_{4}
contacts are
characterized by dispersive (DIS) and quasichemical (QUAC) interaction
parameters, which are reported. Contacts of the type (polar group)/CCl_{4}
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 + CCl_{4}
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, G^{E},
and molar excess
enthalpies,
H^{E}. So, the mean
deviations between experimental and
calculated
results are about 2% for pressure, and 8% for H^{E}. 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 H^{E},
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 (x_{1},
x_{2}) 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, CCl_{4} 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, G^{E}.

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.

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, CCl

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, G

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 CHCl
_{3}or CH_{2}Cl_{2}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 CHCl_{3} or CH_{2}Cl_{2} 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 (H^{E}),
molar excess heat capacities at constant
pressure
(C_{P}^{E}) or natural logarithms
of activity
coefficients at infinite
dilution (ln γ_{i}^{∞}). 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, x_{1}, for systems
with 2-methoxyethanol, and to the region of lower x_{1} values for the
mixtures including the other two hydroxyethers. The (x_{1}, T) data were
fitted to the equation T = T_{c}
+
k¦y-y_{c}¦^{m} where y = γ x_{1}/{1
+ x_{1}(γ - 1)} and y_{c}
=
γ x_{1c}/{1 + x_{1c}(γ - 1)}.
T_{c} and x_{1c} 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 V_{m}^{E}
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
V_{m}^{E}
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 CH_{3}-(O-CH_{2}CH_{2})_{m}-CH_{3}.
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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