Principal Miembros Historia Investigación Laboratorio Publicaciones Proyectos Enlaces

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/NH_{2}, 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 (G^{E})
and
molar excess enthalpies (H^{E}).
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 G^{E} and for systems
containing
methanol, DISQUAC results on H^{E}
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 H^{E} Obtained
using DISQUAC and ERAS, are 151 and 216 J mol^{-1},
respectively. DISQUAC also improves results on G^{E}, while
ERAS describes
properly the available excess volume (V^{E})
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 (H^{E}),
logarithms of activity coefficients at
infinite
dilution (ln γ_{i}^{∞}) or solid-liquid equilibria
(SLE) are
correctly described by DISQUAC. H^{E}
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 H^{E}
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 V_{m}^{E}
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. V_{m}^{E}
curves are nearly symmetrical at about 0.5 mole fraction. Excess
molar volumes are usually positive, indicating predominance of positive
contributions to V_{m}^{E}
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 V_{m}^{E}
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 (C_{P}^{E}) 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 (G^{E})
and molar excess enthalpies
(H^{E}).
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 H^{E}, while both
models give
similar results for G^{E}.
However, ERAS needs an specific parameter,
with unknown temperature-dependence, to describe properly G^{E}.
The
main advantage of ERAS is its ability to provide information on V^{E}.
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 V_{m}^{E}
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 V_{m}^{E}
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 V_{m}^{E}
curves are symmetrical. This behaviour can be attributed to free volume
effects.

The sign of dV_{m}^{E}/dT is discussed. Systems with
1-propanol are
characterized by dV_{m}^{E}/dT > 0 which may be due
to the more
self-associated character of the alcohol. In solutions with 1-hexanol,
the sign of dV_{m}^{E}/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 dV_{m}^{E}/dT >
0.

Results remark the differences between systems containing n-alkanols and monoethers or polyethers.

The sign of dV

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 κ_{T} were estimated in order to
compute the
Flory characteristic parameters, pressure p_{i}^{*} and
volume v_{i}^{*}.

For each mixture, the energetic parameter χ_{12}was fitted to
excess
enthalpy data H^{E}
at 298.15 K and used to predict correctly
the
corresponding excess volume V^{E}.
The variation of χ_{12}
versus the
numberof C atoms + -O- groups in alkoxyethanols is similar to that
found previously for 1-alkanol mixtures.

For pure compounds, the coefficients of thermal expansion α and isothermal compressibility κ

For each mixture, the energetic parameter χ

- 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 (x_{1},
T) data were fitted
to the
equation T = T_{c} +
k_{c}^{m} where y = α x_{1}/[1
+ x_{1}(α - 1)] and y_{c}
= α x_{1c}/[1 + x_{1c}(α
- 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.

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Principal Miembros Historia Investigación Laboratorio Publicaciones Proyectos Enlaces