What we are studying
Topic: Phase equilibria in systems of low molar mass components
Methodology of measurement and development of experimental techniques for vapour–liquid equilibrium (VLE) determination is a traditional research of the group.
This research started in the late 1940s by Professor E. Hála and co-workers, and it was transformed later into the “Prague thermodynamic school”.
Their first book (Pergamon Press, 1958, 1968) became the basic world textbook dealing with all related problems: besides of the thermodynamic description and prediction
of phase equilibria with new approaches, it includes also mathematical processing of data, measurement and control of system variables, and the first bibliography of published data.
All those items have been supplemented, extended and continued since the group became integrated into the ICPF (1964). As a result, many scientific papers and books were published
with high international impact; the last large publication - based on 35 years long effort - is represented by two volumes of Landolt-Börnstein Encyclopaedia
(2007, 2008). The group gained worldwide reputation
in high quality measurements, accurate interpretation, and statistically sound data processing.
During the last 100 years, data for more than 20000 VLE systems have been published yielding approximately 300000 experimental points what was partly sufficient to enable
for example the development of the UNIFAC group contribution prediction method, however many data are still missing in this database. In the 1990s, the group has been involved
in the large IUPAC project dealing with alkane + alkanol + ether systems. In parallel, the best software in the world was developed for very reliable data processing.
VLE data have been measured also during 2010–2014 in binary and ternary systems of compounds with selected functional groups as a natural continuation of the above mentioned
IUPAC project. Investigated systems were: tert-amyl methyl ether + tert-butanol + isooctane, isooctane + isobutanol + 4-methyl-2-pentanone, isopropanol + isooctane +
2,4-dimethyl-3-pentanone, and dimethylbutane + diisopropylether + 3-methyl-2-butanone. All binary data were correlated using the Wilson and the NRTL models and subsequently used
for successful prediction of data for ternary systems.
Complex combination of phase and chemical equilibria has already been experimentally studied earlier. Recently, these investigations were completed by the data determined isothermally
in the system with chemical reaction (transesterification), namely in the quaternary ethyl ethanoate + ethanol + propyl ethanoate + propanol system and in all six binary subsystems.
Good prediction was achieved with use of correlated NRTL binary parameters.
This topic can continue for many years by supplementing the database with new data, particularly if practically all once-leading European and American labs have quitted experiments
since measurements are “difficult and expensive”; it is easier to use prediction methods which unfortunately do not always lead to the reliable results. In final stage,
a pilot plant (i.e. unavoidable experiment again) must be run to verify the design of separation unit.
Topic: Vapour–liquid equilibria in systems containing polymer
This topic has been split from the above mentioned topic and it represents the extension to systems containing components with high molar mass. The demand for the data of such
systems has been raised in connection with polymeric flow improvers necessary for facilitation of oil transport. New data were necessary to develop/improve prediction methods based
on the group contribution concept. The phenomena of vapour–liquid equilibria (VLE) is essentially the same as for low molar mass components, however experimental techniques
had to be modified due to problems with smooth boiling, and downsized because polymers were available in small amount only.
The first microebulliometer for total pressure measurement was developed, tested and used to measure the component activities in mixtures of polymers with organic solvents in 2010.
During five years, this still has been three times redesigned to enable measurement even under more unfeasible conditions. At the beginning, several polymeric flow improvers such as
copolymers of octadecyl methacrylate or dodecyl methacrylate with acrylic acid or with 1-vinyl-2-pyrrolidone were investigated with several organic solvents (toluene, hexane, chloroform).
Later, this ebulliometric techniques has been successfully used for VLE measurements of other systems like the poly(acrylic acid) + water, the poly(methyl methacrylate) + acetone
or 2-butanone, and the polystyrene + toluene system. All those data have been measured at three isotherms in the region of low polymer concentrations and correlated using
the UNIQUAC-FV model. The three prediction models (the GC-Flory EoS, the UNIFAC-vdW-FV, and the Entropic-FV model) were tested against the new experimental data.
Novelty of the topic: Several stills were developed and designed for total pressure measurement by ebulliometric method. This technique has not been practically used and described
earlier in literature. In parallel, three correlation and prediction methods were successfully applied to the newly obtained data.
Topic: Ionic liquids
Ionic liquids are class of organic salts that consist of bulky, assymetric organic cations and smaller, mostly symmetric organic or
inorganic anions, showing interesting chemical, physical, and physicochemical properties and a promising application potential.
The number of ion combinations means a large number of possible ionic liquid structures, allowing for a fine tuning of their properties
to various applications. For instance, ionic liquids have already found their way into separation processes as azeotrope breakers or
sorbents in mercury separation from fuels. Further, ionic liquids may be used as novel electrolytes or reaction media.
To contribute to the steadily increasing knowledge base of physicochemical properties of ionic liquids, thermodynamic and thermophysical
properties of pure ionic liquids are studied in our group, particularly their heat capacities and PVT properties. In homogeneous systems
of ionic liquids with molecular liquids excess properties (volume and heat capacity) are studied, whereas in systems showing limited
miscibility liquid-liquid equilibria are determined. In collaboration with other research groups both of the ICPF and of other Czech and
international research institutions, properties of novel ionic liquids, both pure and in mixtures with molecular solvents, are investigated,
principally in terms of the structure-property relationships, but also from the point of view of their practical applications, such as
their use as electrolytes or in CO2 capture.
Comprehensive studies of the above-mentioned systems is performed using the following equipment. Apparatuses for the determination of LLE
built in-house (a battery of LLE equilibrium cells, cloud-point, and volumetric method apparatuses), Anton Paar U-tube vibration
densitometers, and a Setaram μDSC III evo differential scanning calorimeter are available. The experimental data are then correlated using
relevant thermodynamic relationships (GE models such as Redlich-Kister, NRTL, or the modified Flory-Huggins equations, equations of
state, etc.). Unique computational skills based on mathematical gnostics are used in data processing. Data assessment, experimental
method diagnostics, and model parameter optimization are possible even in cases of a very small size of the data sample for which the
assumption of normality of experimental error cannot be verified or is violated.
Last revision was made on 20 June 2015
