663
The CO 2 uptake in different type guaiacol (GC)-based DESs was investigated by
the Liu et al. [132]. The DES composed of diethylamine hydrochloride as HBA and
GC as HBD (1:5) has the highest CO 2 loading capacity. However, the observed CO 2
solubility was lesser than the glycine DES. A comparison of CO 2 solubility in ChClbased DESs with different HBD has been presented in Fig. 11. The results show that
changing the HBDs has significant effect on the CO 2 uptake of DESs. Haider et al.
have synthesized 15 different DESs using ChCl and TBAB as HBA for investigating
CO 2 solubility [133]. The results show that increase in the chain length of HBA
increases CO 2 solubility. The effect of HBA on CO 2 solubility for a fixed HBD
(levulinic acid) has been shown in Fig. 12. It was observed that changing the HBA
significantly affects the CO 2 solubility. The DESs containing tetrabutylammonium
bromide (TBAB) have higher CO 2 capture ability than the other HBDs.
4.2.3 HBDs with NH Moiety
Further studies were focused on DESs consisting of HBDs with -NH moieties.
ChCl:urea (reline) DESs having molar ratios of 1:1.5, 1:2, and 1:2.5 were synthesized by Li et al. and Leron et al. [129, 134]. Highest CO 2 uptake was observed in
the DES having ChCl:urea molar ratio of 1:2. The amount of CO 2 absorb was comparable to imidazolium-based ILs and found to be higher than ethaline and glycine.
Effect of water addition in the DESs was also explored for CO 2 capture. The results
demonstrate that presence of water in reline reduces the CO 2 solubility [135].
Similar findings were also described by Maheswari et al. for alkanolamine- based
0
0.005
0.01
0.015
0.02
0.025
0.03
0
100
200
300
400
500
600
700
mole fraction of CO
2
Pressure(kPa)
ChCl:3Levulinic acid
ChCl:4Levulinic acid
ChCl:3Furfuryl
acohol
ChCl:4Furfuryl
acohol
ChCl:3GC
ChCl:4GC
ChCl:2EG
DH:3GC
Fig. 11 CO 2 solubility in ChCl-based DESs with different HBDs at 303.15 K
Potential Application of Ionic Liquids and Deep Eutectic Solvents in Reduction…
The CO 2 uptake in different type guaiacol (GC)-based DESs was investigated by
the Liu et al. [132]. The DES composed of diethylamine hydrochloride as HBA and
GC as HBD (1:5) has the highest CO 2 loading capacity. However, the observed CO 2
solubility was lesser than the glycine DES. A comparison of CO 2 solubility in ChClbased DESs with different HBD has been presented in Fig. 11. The results show that
changing the HBDs has significant effect on the CO 2 uptake of DESs. Haider et al.
have synthesized 15 different DESs using ChCl and TBAB as HBA for investigating
CO 2 solubility [133]. The results show that increase in the chain length of HBA
increases CO 2 solubility. The effect of HBA on CO 2 solubility for a fixed HBD
(levulinic acid) has been shown in Fig. 12. It was observed that changing the HBA
significantly affects the CO 2 solubility. The DESs containing tetrabutylammonium
bromide (TBAB) have higher CO 2 capture ability than the other HBDs.
4.2.3 HBDs with NH Moiety
Further studies were focused on DESs consisting of HBDs with -NH moieties.
ChCl:urea (reline) DESs having molar ratios of 1:1.5, 1:2, and 1:2.5 were synthesized by Li et al. and Leron et al. [129, 134]. Highest CO 2 uptake was observed in
the DES having ChCl:urea molar ratio of 1:2. The amount of CO 2 absorb was comparable to imidazolium-based ILs and found to be higher than ethaline and glycine.
Effect of water addition in the DESs was also explored for CO 2 capture. The results
demonstrate that presence of water in reline reduces the CO 2 solubility [135].
Similar findings were also described by Maheswari et al. for alkanolamine- based
0
0.005
0.01
0.015
0.02
0.025
0.03
0
100
200
300
400
500
600
700
mole fraction of CO
2
Pressure(kPa)
ChCl:3Levulinic acid
ChCl:4Levulinic acid
ChCl:3Furfuryl
acohol
ChCl:4Furfuryl
acohol
ChCl:3GC
ChCl:4GC
ChCl:2EG
DH:3GC
Fig. 11 CO 2 solubility in ChCl-based DESs with different HBDs at 303.15 K
Potential Application of Ionic Liquids and Deep Eutectic Solvents in Reduction…