In
this work, isobaric vapor–liquid equilibrium data for
the binary mixtures of the isobutyl acetate + isoamyl acetate and
isobutyl acetate + ethyl acetate were measured using an all-glass
dynamic-recirculation still equipped with a Cottrell circulation pump
(Labodest VLE 602D). For the system of isobutyl acetate + isoamyl
acetate the measurements were carried out at 100 and 150 kPa, while
for the system isobutyl acetate + ethyl acetate they were performed
at 50, 100, and 150 kPa. Vapor pressures of the pure components were
also measured to verify the performance and reliability of the equilibrium
still, and data were correlated with an Antoine-type expression. The
equilibrium data for the pure components were in agreement with literature
reports and the data for the binary solutions show a fairly ideal
behavior. Binary parameters for nonrandom two liquid (NRTL) and universal
quasichemical (UNIQUAC) equations were correlated with experimental
data, and both models showed good agreement with experiments and can
be used for process design. It was found that, in the absence of experimental
data, phase equilibrium in mixtures of acetates formed in the direct
esterification of the fusel oil can be confidently predicted using
the UNIFAC-DMD model or even the Ideal Model.
In
this work, diethyl citrate (DEC) was synthesized and isolated
for further physicochemical characterization and phase equilibria
study. The synthesis was performed via partial esterification of citric
acid with ethanol, and the final product was separated from the resulting
mixture using a pH-controlled solvent extraction method. Characterization
using 1H NMR and 13C NMR spectroscopy confirmed
the presence of both DEC isomers with few impurities. Results indicate
that a 6:5 molar ratio of the symmetric to the nonsymmetric ester
structures was attained during synthesis. Thermogravimetric analysis
and differential scanning calorimetry allowed us to measure, for the
first time, glass transition temperature (228 K) and decomposition
temperature (493 K) of diethyl citrate. Additionally, P–x data for the vapor–liquid equilibrium of the binary mixtures
diethyl citrate + ethanol and diethyl citrate + water were collected
at 308 K using an accurate dynamic device. Data were regressed to
generate binary interaction parameters for the UNIQUAC equation. The
regressed model shows good agreement with experiments, and it can
be used for further process design in the esterification of citric
acid.
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