661
4.1.5 Thermal Stability
Thermal stability of DESs largely depends on the type of precursor compounds and
their molar ratio. Strong intermolecular interaction among precursor compounds
results in high thermal stability of DESs. Some of the DESs are having higher thermal stability than those of hydrogen bond donors and ionic liquids [121].
4.1.6 Toxicity
Hayyan et al. investigated the toxicity of various DESs [122, 123] and found that
DESs are more toxic as compared to their individual compounds. The toxicity of
DESs varies with the type of salt and hydrogen bond donor. Natural DESs are less
toxic compared to the DESs precursors [124, 125]. Therefore, the toxicity of the
DESs can be tailored based on the choice of hydrogen bond donor and acceptor.
4.2 DESs for CO 2 Capture
Along the line of ILs, DESs have been considered to be a green solvent having
advantageous properties owing to biodegradability, non-flammability, simple synthesis, and high chemical as well as thermal stability. Li et al. first studied the CO 2
uptake in the DESs synthesized from urea and choline chloride having molar ratio
of 1.5:1, 2:1, and 2.5:1 in the temperature range from 40 to 60 °C up to a pressure
of 13 MPa [126]. Their results revealed that for a fixed pressure and temperature,
CO 2 solubility depends upon the DESs molar ratio and the highest CO 2 solubility
was observed for 1:2 molar ratio of choline chloride and urea. Much of the later
work was focused on CO 2 solubility in DESs; however, some studies were also done
for other gases such as CO, N 2 , CH 4 , and SO 2 .
4.2.1 CO 2 Solubility in Ammonium-Based DESs
Since the first synthesized DES by Abbott et al. was based on ammonium salt, therefore much of the later work was focused on the ammonium-based salt only. An
extensive study was done for investigation of CO 2 solubility in DESs having ammonium salts. The most commonly used ammonium salt was choline chloride and later
work extended to tetrabutylammonium bromide, tetrabutylammonium chloride, and
other ammonium salts.
Potential Application of Ionic Liquids and Deep Eutectic Solvents in Reduction…
4.1.5 Thermal Stability
Thermal stability of DESs largely depends on the type of precursor compounds and
their molar ratio. Strong intermolecular interaction among precursor compounds
results in high thermal stability of DESs. Some of the DESs are having higher thermal stability than those of hydrogen bond donors and ionic liquids [121].
4.1.6 Toxicity
Hayyan et al. investigated the toxicity of various DESs [122, 123] and found that
DESs are more toxic as compared to their individual compounds. The toxicity of
DESs varies with the type of salt and hydrogen bond donor. Natural DESs are less
toxic compared to the DESs precursors [124, 125]. Therefore, the toxicity of the
DESs can be tailored based on the choice of hydrogen bond donor and acceptor.
4.2 DESs for CO 2 Capture
Along the line of ILs, DESs have been considered to be a green solvent having
advantageous properties owing to biodegradability, non-flammability, simple synthesis, and high chemical as well as thermal stability. Li et al. first studied the CO 2
uptake in the DESs synthesized from urea and choline chloride having molar ratio
of 1.5:1, 2:1, and 2.5:1 in the temperature range from 40 to 60 °C up to a pressure
of 13 MPa [126]. Their results revealed that for a fixed pressure and temperature,
CO 2 solubility depends upon the DESs molar ratio and the highest CO 2 solubility
was observed for 1:2 molar ratio of choline chloride and urea. Much of the later
work was focused on CO 2 solubility in DESs; however, some studies were also done
for other gases such as CO, N 2 , CH 4 , and SO 2 .
4.2.1 CO 2 Solubility in Ammonium-Based DESs
Since the first synthesized DES by Abbott et al. was based on ammonium salt, therefore much of the later work was focused on the ammonium-based salt only. An
extensive study was done for investigation of CO 2 solubility in DESs having ammonium salts. The most commonly used ammonium salt was choline chloride and later
work extended to tetrabutylammonium bromide, tetrabutylammonium chloride, and
other ammonium salts.
Potential Application of Ionic Liquids and Deep Eutectic Solvents in Reduction…