Abstract:Deep eutectic solvents (DESs) have emerged as inexpensive and environmentally‐benign liquid media for potential usage in chemical sciences. CO2 capture and sequestration by various substances is an active area of research in green chemistry. CO2 capture ability of DES‐based systems composed of salt choline chloride mixed with hydrogen bond donors urea (named reline), ethylene glycol (named ethaline), and monoethanolamine (named MEACC), are assessed in the absence and presence of three superbases: 1,5‐diazabicy… Show more
“…DESs have been investigated for CO 2 capture, as they can absorb CO 2 through the entropic voids within the liquid, similar to nonreactive ILs. , A DES is a mixture for which the melting point is significantly lower than either of the parent compounds: a hydrogen bond acceptor (HBA), usually a halide salt, and a hydrogen bond donor (HBD), such as EG. Recent studies showed that DESs and DES-like mixtures with superbase additives, superbase HBAs, or superbases as the tertiary component have CO 2 capacities ranging from 3.6 to 17.34 wt % at 1 bar of CO 2 with typical absorption temperatures of 45–60 °C. The highest gravimetric CO 2 capacity at 33.7 wt % is reported for a mixture of monoethanolammonium chloride, [MEA.Cl], and ethlyenediamine at 1 bar of CO 2 and 30 °C .…”
Solvents made from a reactive ionic liquid, with an imidazolium cation and pyrrolide anion, and ethylene glycol at a wide compositional range were studied for separations of CO 2 at low partial pressures (≪0.1 bar up to 1 bar). Thermal analysis and measurements of viscosity and density show compacting of the liquid upon mixing with enhanced stability achieved by hydrogen bonding. A detailed mechanistic study was performed by IR, quantitative NMR, and ab initio calculations that show significant CO 2 absorption capacity below 5000 ppm of CO 2 in N 2 . Three reversible routes are found that yield carbonate (major product), carboxylate (moderate), and carbamate (minor) species. With CO 2 at 100% RH, bicarbonate along with carbonate species form. The CO 2 -ethlyene glycol reaction complex, the carbonate anion, is stabilized by the hydrogen bonding and Coulombic interactions, thus preventing evaporation of the solvent during regeneration. This study demonstrates a promising approach to designer green solvents for CO 2 separations in open systems such as direct air capture.
“…DESs have been investigated for CO 2 capture, as they can absorb CO 2 through the entropic voids within the liquid, similar to nonreactive ILs. , A DES is a mixture for which the melting point is significantly lower than either of the parent compounds: a hydrogen bond acceptor (HBA), usually a halide salt, and a hydrogen bond donor (HBD), such as EG. Recent studies showed that DESs and DES-like mixtures with superbase additives, superbase HBAs, or superbases as the tertiary component have CO 2 capacities ranging from 3.6 to 17.34 wt % at 1 bar of CO 2 with typical absorption temperatures of 45–60 °C. The highest gravimetric CO 2 capacity at 33.7 wt % is reported for a mixture of monoethanolammonium chloride, [MEA.Cl], and ethlyenediamine at 1 bar of CO 2 and 30 °C .…”
Solvents made from a reactive ionic liquid, with an imidazolium cation and pyrrolide anion, and ethylene glycol at a wide compositional range were studied for separations of CO 2 at low partial pressures (≪0.1 bar up to 1 bar). Thermal analysis and measurements of viscosity and density show compacting of the liquid upon mixing with enhanced stability achieved by hydrogen bonding. A detailed mechanistic study was performed by IR, quantitative NMR, and ab initio calculations that show significant CO 2 absorption capacity below 5000 ppm of CO 2 in N 2 . Three reversible routes are found that yield carbonate (major product), carboxylate (moderate), and carbamate (minor) species. With CO 2 at 100% RH, bicarbonate along with carbonate species form. The CO 2 -ethlyene glycol reaction complex, the carbonate anion, is stabilized by the hydrogen bonding and Coulombic interactions, thus preventing evaporation of the solvent during regeneration. This study demonstrates a promising approach to designer green solvents for CO 2 separations in open systems such as direct air capture.
“…Sulfur dioxide (SO 2 ), another greenhouse gas, is one of the main constituents responsible for acid deposition, which has adverse effects on materials, natural resources, and human health . In the past, in order to mitigate the emission of CO 2 and SO 2 gases, researchers have put forth enormous effort for the development of various technologies to capture them. − The most efficient and commonly used industrial technique to capture CO 2 is amine-based postcombustion CO 2 capture. , However, this technique has several drawbacks like amine degradation, equipment corrosion, and environmental issues. − Similarly, to mitigate SO 2 emission, most industrial processes use the wet limestone flue gas desulfurization technique. , However, this method is irreversible and leads to unwanted byproducts. , Therefore, the search for a superior method to overcome the drawbacks of conventional methods − led the researchers toward the use of novel materials such ionic liquids (ILs). − Owing to their unique properties, − ILs exhibited significant gas separation propensity. , Although gas absorption by ILs is a reversible process , with no side products, ILs are barely used in industries for gas capturing on a large scale because of their high production cost and low absorption capacity. , Recently, deep eutectic solvents (DESs) have emerged as alternative media for capturing gases − because of their biodegradable nature, ease of preparation, and lower cost of the starting materials. − DESs are commonly referred to as IL analogs because they share similar properties such as tunable character, high thermal stability, and low vapor pressure along with some new improved properties like biodegradability and low toxicity. − ...…”
Section: Introductionmentioning
confidence: 99%
“…Because of their numerous favorable properties, the role of DESs in the field of gas capture was explored through a series of experimental works. − Li et al highlighted the effect of temperature and pressure on the solubility of CO 2 at different compositions of choline–chloride ([Ch][Cl]) and urea . The authors showed that the solubility of CO 2 increased with increasing CO 2 pressure and decreased with increasing temperature.…”
Section: Introductionmentioning
confidence: 99%
“…Leron et al used a eutectic mixture of [Ch][Cl]/ethylene glycol (in molar ratio 1:2), called ethaline, to study the solubility of CO 2 at various temperatures and pressures, and the reported values of solubility were in the typical range as also found in ILs . Pandey and co-workers highlighted the effectiveness of superbases when added to [Ch][Cl]-based DESs for CO 2 sequestration . The authors showed that the CO 2 capture efficiency of reline and ethaline DESs increased with the addition of superbase.…”
Deep eutectic solvents (DESs) are emerging as an alternative media for the sequestration of greenhouse gases such as CO 2 and SO 2 . Herein, we performed ab initio molecular dynamics (AIMD) simulations to elucidate the solvation structure around CO 2 and SO 2 in choline chloride-based DESs, namely, reline and ethaline. We show that in all four systems the structures of the nearest neighbor shells around these molecules are distinct. We observe that because of the electrophilic character, the carbon atom of CO 2 and the sulfur atom of SO 2 are preferentially solvated by the chloride anions. The strength of the correlation between the chloride anions and the sulfur atom is much stronger because of charge transfer, which is more profound in ethaline DES. In both DESs, the choline cations are found to be closer to the oxygen atoms of CO 2 and SO 2 . We observe that upon changing the solute from CO 2 to SO 2 , the nearest neighbor solvation structure changes drastically; while the chloride anions prefer to stay in a circular shell around the carbon atom of CO 2 , they are found to be much more localized near the sulfur atom of SO 2 . The solvation shells formed by the urea molecules in reline and EG molecules in ethaline also overlap with that of the chloride anion around CO 2 . In ethaline, the hydroxyl group of the choline cation is found to be closer to the solute molecules as compared to its ammonium headgroup.
“…A lot of DESs have been prepared as CO 2 absorbents so far. Among them, amine-based DESs [ 12 , 13 , 14 , 15 , 16 ], anion-functionalized DESs [ 17 , 18 ], and superbase-based DESs [ 19 , 20 , 21 , 22 ] showed attractive CO 2 capacities through the reaction between CO 2 and active sites in the components at ambient pressure, suggesting that adjusting the structures of the components in the DESs can be an effective strategy to meet the particular demands. Moreover, the interactions between CO 2 and the functionalized DESs were also reported in the literatures.…”
Recently, deep eutectic solvents (DESs), a new type of solvent, have been studied widely for CO2 capture. In this work, the anion-functionalized deep eutectic solvents composed of phenol-based ionic liquids (ILs) and hydrogen bond donors (HBDs) ethylene glycol (EG) or 4-methylimidazole (4CH3-Im) were synthesized for CO2 capture. The phenol-based ILs used in this study were prepared from bio-derived phenols carvacrol (Car) and thymol (Thy). The CO2 absorption capacities of the DESs were determined. The absorption mechanisms by the DESs were also studied using nuclear magnetic resonance (NMR), Fourier transform infrared (FTIR), and mass spectroscopy. Interestingly, the results indicated that CO2 reacted with both the phenolic anions and EG, generating the phenol-based carbonates and the EG-based carbonates, when CO2 interacted with the DESs formed by the ILs and EG. However, CO2 only reacted with the phenolic anions when the DESs formed by the ILs and 4CH3-Im. The results indicated that the HBDs impacted greatly on the CO2 absorption mechanism, suggesting the mechanism can be tuned by changing the HBDs, and the different reaction pathways may be due to the steric hinderance differences of the functional groups of the HBDs.
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