Transcript Ionic liquids and their heating behaviour during microwave

Ionic liquids and their heating behaviour
during microwave irradiation -a state of
the art report and challenge to
assessment
Graduate Student: D.N. Guo
Advisor: M.C. Hsiao
content
• Introduction
• Experimental
• Resluts and discussion
• Conclusions
Introduction
• The application of ionic liquids as
alternative reaction media was frequently
reported in literature during recent years.
• Properties of ionic liquids such as solubility,
solvation strength, acidity, and coordination
were selectively varied and in most cases
successfully validated.
Introduction
• However, extended reaction times of some
syntheses lead to the question of whether
higher temperatures and thus shorter
reaction times would result in higher product
yields and selectivities.
• Microwave-assisted reactions are known for
their short reaction times. This advantage
results from the way in which substances are
heated in the microwave field.
Introduction
• Microwaves directly excite polar molecules
(dipole relaxation) and ions (ionic conduction).
Therefore, the presence of ions and/or polar
molecules is necessary for substances to be heated
in the microwave field.
• Due to their broad application spectrum, a series
of 1,3-dialkylimidazolium compounds was
synthesised and their heating behaviour was
studied under multi-mode microwave conditions.
Experimental
selected mixtures of
aforementioned ionic
liquids with toluene
or cyclohexane were
prepared and
temperature-timecurves were registered.
5
4
6
5
7
4
3
8
3
2
9
2
1
11
6
7
8
9
1
10
Experimental
Microwave heating experiments
The temperature was recorded with a fibre optic sensor for different
microwave power settings in an ETHOS® 1600 microwave furnace
(MLS GmbH, Leutkirch, Germany). Furthermore, selected mixtures of
aforementioned ionic liquids with toluene or cyclohexane were prepared
and temperature–time-curves were registered.
Results and discussion
Results and discussion
Results and discussion
Results and discussion
Results and discussion
Conclusion
1. Only small amounts of ionic liquids are necessary in
order to significantly reduce the heating time of
toluene or cyclohexane under microwave conditions.
2. An increase in the microwave power further
amplifies this reduction in heating time.
3. Ionic liquids of the 1,3- alkylimidazoliumtype can be
advantageously employed as solvents and cosolvents
in synthesis as well as separations.