Characters and Applications of imidazolium ionic liquid Mesoscopic Aggregation and Carbon dioxide fixation
Date Issued
2010
Date
2010
Author(s)
Wu, Tsao-Dong
Abstract
Recently, the topics of substituting volatile organic solvents with ionic-liquids takes
advantages of the flexibility in designed functionalities. Ionic-liquids improves the
reaction capabilities with specific functionalities and also becomes more eco friendly.
We have synthesized ionic liquids built-in with mononuclear, binuclear and
multinuclear imidazolium cations and have probed the molecular interactions of
monoimidazolium ionic liquids with 1H-NMR and TEM. We have found that the
property of mesoscopic aggregation of ionic liquids are with two dominant forces, the
hydrogen bonding (Brønsted acid-base pair) and the π-acid (Lewis acid-base pair)
besides the charge attraction and repellence.
The application on catalytic conversion of ROH to RBr with mononuclear
ionic-liquids have been shown that the ionic-liquid catalysts could be recovered and
reused for six times without loss of reactivity. In D2O at pH 7, we have found that the
binuclear ionic liquids spontaneously form carbene species as an important
intermeatiale on dynamic H-D exchange phenomena and are employed as initially
agents for the caprolactone ring-open polymerization to synthesis the bio-degradation
polycaprolactone.
We have also developed a carbene derivative, N,N’-dimethylimidiazolium-2
-carboxylate (1-1-CO2, a masked carbene). According the TGA results, 1-1-CO2 would
be sublimed instead of thermally decomposed at 130℃. Hence 1-1-CO2 was used in the
CO2 fixation reaction, to catalyze the conversion of propylene epoxide into propylene
carbonate, 1-1-CO2 being reused as catalyst for 10 times.
Multinuclear imidazolium ionic-liquids could also be the catalyst for cycloaddition
reaction of carbon dioxide and epoxy species, and have been reused for 8 times.
Furthermore, this catalyst system fixed at high molecular weight skeleton is easy for the
V
separation of products by simple filtration utilizing SiO2.
In conclusion, this exploratory work was being devoted to the capability of
ionic-liquids, on catalytic halide substitution reaction for hydroxyl group of an alcohol,
ring-open polymerization of caprolactone, and cycloaddition reaction with carbon
dioxide and epoxide. The reactions are all improved to more friendly towards the
environments.
Subjects
ionic liquids
aggregation
substitution reaction
H-D exchange
NHC-carbene
Carbon dioxide fixation
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