Carbon dioxide absorbent comprising ionic liquid and alcohol solvent and method for separating carbon dioxide using the carbon dioxide absorbent

Abstract

The present invention relates to a carbon dioxide absorbent comprising an ionic liquid containing an imidazolium-based anion and an aliphatic alcohol, and the alcohol solvent contained in the carbon dioxide absorbent according to one embodiment has low toxicity and a very high boiling point, thus there is no problem of release into the atmosphere and environmental pollution caused thereby, and has chemical stability, so that the possibility of release of decomposition products into the atmosphere can be significantly reduced. Furthermore, a higher equivalent of carbon dioxide than the added equivalent of the absorbent can be absorbed, and carbon dioxide is easily desorbed due to low regeneration energy, thus being effective.

Description

Technical Field

[0001] This invention relates to a carbon dioxide absorbent comprising an ionic liquid and an alcohol solvent, and a method for separating carbon dioxide using the carbon dioxide absorbent. Background Technology

[0002] Due to rapid economic development and industrialization worldwide, energy use is increasing, and consequently, the use of fossil fuels, the primary source of energy, is also rising. Global warming, closely related to energy use, is a global concern. Carbon dioxide (CO2), the largest component of major greenhouse gases, is largely produced during the burning of fossil fuels and their conversion into energy.

[0003] Given that the carbon dioxide produced can be controlled, technologies for removing carbon dioxide have attracted much attention. Methods applied to combustion exhaust gases in carbon dioxide capture processes mainly include absorption, adsorption, and membrane separation, based on their separation characteristics. Among these, absorption is the most actively used method, which is further divided into physical absorption and chemical absorption.

[0004] Representative absorbents for the chemical absorption method include monoethanolamine (MEA), diethanolamine (DEA), N-methyldiethanolamine (MDEA), and other alkanolamine compounds. In particular, MEA, belonging to the primary amine class, is used in a 30% by weight aqueous solution and has the advantage of rapid reaction with carbon dioxide. However, its disadvantage lies in the high regeneration energy required during desorption after carbon dioxide absorption due to the high heat capacity of water (4.20 kJ / kg℃). Furthermore, amine absorbents are prone to degradation or corrosion of the equipment due to heat and oxygen, and their low-boiling-point decomposition products are released into the atmosphere, potentially causing environmental problems.

[0005] Therefore, there is a need to develop an absorbent that has a high boiling point, thus eliminating the possibility of release into the atmosphere, and that is chemically stable, thereby reducing the release of decomposition products into the atmosphere and desorbing carbon dioxide with low regeneration energy. Summary of the Invention

[0006] Technical problems to be solved

[0007] One specific embodiment aims to provide a carbon dioxide absorbent that can capture carbon dioxide with high performance and effectively desorb carbon dioxide under easy conditions.

[0008] Another objective of one particular embodiment is to provide a carbon dioxide supply agent comprising a compound formed by reacting the carbon dioxide absorbent with carbon dioxide.

[0009] Another objective of a particular embodiment is to provide a method for separating carbon dioxide, the method comprising the step of reacting the carbon dioxide absorbent.

[0010] Technical solution

[0011] To achieve the above objectives, one specific embodiment provides a carbon dioxide absorbent comprising: an ionic liquid containing an imidazole anion; and an aliphatic alcohol.

[0012] Another specific embodiment provides a carbon dioxide supply agent comprising a compound formed by reacting the carbon dioxide absorbent with carbon dioxide, and an aliphatic carbonate.

[0013] Another specific embodiment provides a method for separating carbon dioxide, the method comprising the steps of: contacting a carbon dioxide absorbent with a mixture containing carbon dioxide at a temperature of 20-80°C, wherein the carbon dioxide absorbent comprises an ionic liquid containing an imidazole anion and an aliphatic alcohol.

[0014] Beneficial effects

[0015] This invention relates to a carbon dioxide absorbent comprising an ionic liquid containing an imidazole anion and an aliphatic alcohol. According to one embodiment, the alcohol solvent in the carbon dioxide absorbent has low toxicity and a very high boiling point, thus eliminating the problem of release into the atmosphere and resulting environmental pollution. Furthermore, it possesses chemical stability, thereby significantly reducing the possibility of decomposition products being released into the atmosphere. In addition, it can absorb a higher equivalent of carbon dioxide than the amount added to the absorbent, and it is effective due to its low regeneration energy and easy desorption of carbon dioxide. Attached Figure Description

[0016] Figure 1 This demonstrates that, in order to confirm the simultaneous formation of carbamates and carbonates after carbon dioxide absorption and the regeneration of cations and imidazole anions after carbon dioxide desorption, the following procedures were performed: before absorption with the carbon dioxide absorbent according to Example 1, after absorption of carbon dioxide at 40°C, and after desorption at 90°C for 3.0 hours. 1 A graph showing the results of H NMR analysis.

[0017] Figure 2This demonstrates that, in order to confirm the simultaneous formation of carbamates and carbonates after carbon dioxide absorption and the regeneration of cations and imidazole anions after carbon dioxide desorption, the following procedures were performed: before absorption with the carbon dioxide absorbent according to Example 1, after absorption of carbon dioxide at 40°C, and after desorption for 1 hour at 60°C and 100°C, respectively. 13 A graph showing the results of C NMR analysis.

[0018] Figure 3 To demonstrate the desorption performance compared to that of the existing commercial absorbent MEA, the absorbent of Comparative Example 6 was used to absorb carbon dioxide at 40°C, followed by desorption at 130°C for 1 hour, 2 hours, and 3 hours, respectively. 13 A graph showing the results of CNMR analysis.

[0019] Best practice

[0020] The following provides a detailed description of a specific implementation scheme and example.

[0021] Furthermore, the implementation of a particular embodiment can be varied in various forms, and the scope of a particular embodiment is not limited to the embodiments described below. Moreover, the implementation of a particular embodiment is provided to provide a more specific description of a particular embodiment to those skilled in the art. Furthermore, throughout the specification, unless otherwise stated specifically to the contrary, "comprising" or "including" a component means that other components may also be included, not that other components are excluded.

[0022] One specific embodiment provides a carbon dioxide absorbent comprising: an ionic liquid containing an imidazole anion; and an aliphatic alcohol.

[0023] The imidazole anion can function as an anion (base) contained in the ionic liquid provided in one embodiment, as long as it is a compound containing imidazole (C3N2H4) and carrying a negative charge; therefore, its structure is not particularly limited. For example, the imidazole anion can be represented by the following chemical formula 1.

[0024] [Chemical Formula 1]

[0025]

[0026] In the chemical formula 1,

[0027] The R 1 R 2 and R 3 Each can be independently hydrogen, substituted or unsubstituted C. 1-10 Alkyl, substituted or unsubstituted C1-10 Alkyl carbonyl, substituted or unsubstituted C 1-10 Alkoxy, substituted or unsubstituted C 3-8 Cycloalkyl groups, heterocycloalkyl groups comprising 5-10 atoms of substituted or unsubstituted heteroatoms selected from N, O, and S, and substituted or unsubstituted C atoms. 5-10 aryl or heteroaryl containing 5-10 atoms of substituted or unsubstituted heteroatoms selected from N, O and S, or

[0028] The R 1 and R 2 They can connect with the carbon atoms they are bonded to to form substituted or unsubstituted C atoms. 3-8 Cycloalkyl groups, heterocycloalkyl groups comprising 5-10 atoms of substituted or unsubstituted heteroatoms selected from N, O, and S, and substituted or unsubstituted C atoms. 5-10 Aryl groups, heteroaryl groups comprising 5-10 atoms, either substituted or unsubstituted, of one or more heteroatoms selected from N, O, and S.

[0029] The substitution can be selected from halogen, oxo, cyano, amino, nitrile, C, etc. 1-10 Alkyl, C 1-10 alkyl carbonyl and C 1-10 One or more substituents in the alkoxy group are substituted.

[0030] Or, the R 1 R 2 and R 3 Each can be independently hydrogen, substituted or unsubstituted C. 1-8 Alkyl, substituted or unsubstituted C 1-8 Alkyl carbonyl, substituted or unsubstituted C 1-8 Alkoxy, substituted or unsubstituted C 3-6 Cycloalkyl groups, heterocycloalkyl groups containing 5-8 atoms of substituted or unsubstituted heteroatoms selected from N, O, and S, and substituted or unsubstituted C atoms. 5-8 Aryl or heteroaryl groups consisting of 5-8 substituted or unsubstituted atoms containing one or more heteroatoms selected from N, O and S.

[0031] Or, the R 1 R 2 and R 3 Each can be independently hydrogen, substituted or unsubstituted C. 1-5 Alkyl, substituted or unsubstituted C 1-5 Alkyl carbonyl or substituted or unsubstituted C 1-5 alkoxy, or

[0032] The R 1 and R 2They can connect with the carbon atoms they are bonded to to form substituted or unsubstituted C atoms. 5-8 Cycloalkyl groups, heterocycloalkyl groups containing 5-8 atoms of substituted or unsubstituted heteroatoms selected from N, O, and S, and substituted or unsubstituted C atoms. 5-8 Aryl groups, heteroaryl groups comprising 5-8 atoms, either substituted or unsubstituted, of one or more heteroatoms selected from N, O, and S.

[0033] The substitution can be selected from halogen, oxo group, and C, respectively. 1-5 One or more substituents in the alkyl group are used for substitution.

[0034] Or, the R 1 R 2 and R 3 Each can be independently hydrogen, substituted or unsubstituted C. 1-3 Alkyl, substituted or unsubstituted C 1-3 Alkyl carbonyl or substituted or unsubstituted C 1-3 alkoxy, or

[0035] The R 1 and R 2 They can connect with the carbon atoms they are bonded to to form substituted or unsubstituted C atoms. 5-6 Cycloalkyl groups, heterocycloalkyl groups containing 5-6 atoms of substituted or unsubstituted heteroatoms selected from N, O, and S, and substituted or unsubstituted C atoms. 5-6 Aryl groups, heteroaryl groups comprising 5-6 atoms, either substituted or unsubstituted, selected from one or more heteroatoms chosen from N, O, and S.

[0036] The substitution can be selected from halogen, oxo group, and C, respectively. 1-3 One or more substituents in the alkyl group are used for substitution.

[0037] Or, specifically, for example, imidazole anion can be listed. ), benzimidazole anion, ), purine ) or theophylline However, as mentioned above, as long as it is an imidazole anion, the nitrogen anion site can react effectively with carbon dioxide to absorb or capture carbon dioxide, so its structure is not restricted.

[0038] The ionic liquid further comprises cations, and the structure or type of cations is not limited, as long as they are positively charged compounds. For example, the cations can be one or more selected from ammonium, phosphonium, pyridinium, imidazolineium, sulfonium, pyrrolidineonium, piperidinium, pyrazolium, guanidineonium, morpholinium, and their derivatives. The derivatives can be in the form of the cation being substituted with any one or more substituents readily apparent to those skilled in the art, or in the form of two or more cations or their derivatives linked by a linker readily apparent to those skilled in the art, or in the form of the cation being combined with a cyclic compound, or, unrestricted, in the form of an aromatic compound being hydrogenated. For example, the substituents can be halogens, C... 1-30 Aliphatic hydrocarbons, C 5-30 Aromatic hydrocarbons, -OH, -COOH, -C 1-30 Alkyl-OH or -C 1-30 -COOH, but not necessarily limited to this, the linking group can be C 1-30 The hydrocarbon chain, and the carbon atoms in the hydrocarbon chain can be replaced by more than one heteroatom selected from N, O and S, but are not necessarily limited to this.

[0039] The aliphatic alcohol can be, for example, C. 1-30 aliphatic alcohols, C 2-30 aliphatic alcohols, C 2-15 aliphatic alcohols, C 2-12 aliphatic alcohols or C 2-10 The aliphatic alcohol can be, for example, a monohydric alcohol or a polyhydric alcohol having two or more hydroxyl groups. Alternatively, the polyhydric alcohol can be an alcohol having 2-4 hydroxyl groups. As long as the aliphatic alcohol has one or more hydroxyl groups, it can react with carbon dioxide as a solvent in the carbon dioxide absorbent provided in one embodiment to absorb or capture carbon dioxide, and therefore its type or structure is not limited.

[0040] According to one embodiment, the carbon dioxide absorbent contains an aliphatic alcohol as a solvent, and simultaneously forms a carbamate generated by the reaction of anion with carbon dioxide and an alkylcarbonate generated by the reaction of alcohol, thereby absorbing carbon dioxide with a higher capture performance than the added equivalent of the absorbent, thus being effective, and can desorb carbon dioxide even with low regeneration energy, thus also being effective as a carbon dioxide supplier.

[0041] The aliphatic alcohol can be, for example, a saturated aliphatic alcohol, an unsaturated aliphatic alcohol, or an alcohol containing a cyclic structure. Alternatively, it can be C 3-15 Branched alcohols, C4-15 Branched alcohols, C 5-15 Branched alcohols, C 5-10 Branched alcohols or C 2-15 polyols, C 2-10 The polyol may be, for example, selected from one or more of the following: 2-ethylhexanol, 2-methyl-1,3-propanediol, 1,3-propanediol, 2,2-dimethyl-1,3-propanediol, 1,4-butanediol, 1,3-butanediol, 1,2-butanediol, 2,3-butanediol, pinacol, ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, triethylene glycol, tetraethylene glycol, 3-methoxy-3-methyl-1-butanol, 3-methoxy-1-butanol, 1-methoxy-2-butanol, ethylene glycol monoether, n-propanol, isopropanol, 1-butanol, 2-butanol, isobutanol, tert-butanol, 2-pentanol, tert-pentanol, 1-hexanol, allyl alcohol, propargyl alcohol, 2-butenol, 3-butenol, and 4-penten-2-ol.

[0042] The aliphatic alcohol may have a boiling point of 130°C or higher. The boiling point is not necessarily limited to the above range; the boiling point of the aliphatic alcohol may be 140°C or higher, 150°C or higher, 160°C or higher, 170°C or higher, 180°C or higher, or 190°C or higher. Water, a solvent conventionally used as a carbon dioxide absorbent, has a boiling point as low as 100°C, thus posing a high possibility of decomposition products being released into the atmosphere. However, the alcohol solvent provided in one embodiment has a very high boiling point, therefore the possibility of release into the atmosphere is almost nonexistent, and it possesses chemical stability, thereby significantly reducing the possibility of decomposition products being released into the atmosphere.

[0043] The heat capacity of the aliphatic alcohol can be below 4.0 kJ / kg℃. However, the heat capacity is not necessarily limited to the above range; it can be below 3.5 kJ / kg℃, below 3.0 kJ / kg℃, below 2.8 kJ / kg℃, or below 2.5 kJ / kg℃. Conventionally, amine absorbents (e.g., monoethanolamine (MEA)) used as carbon dioxide absorbents employ a 30% by weight aqueous solution. Due to the high heat capacity of water (approximately 4.20 kJ / kg℃) used as the solvent, high regeneration energy is required during desorption. Furthermore, amine absorbents are prone to thermal or oxidative decomposition due to heat and oxygen, leading to environmental problems caused by the release of decomposition products into the atmosphere. In contrast, the carbon dioxide absorbent according to one embodiment uses an ionic liquid containing an imidazole anion and an alcohol solvent, thereby reducing the heat capacity and significantly improving the regeneration energy of the absorbent compared to conventional methods.

[0044] According to one embodiment, the carbon dioxide absorption equivalent of the carbon dioxide absorbent, expressed by the following formula 1, can be 0.7 or more.

[0045] [Formula 1]

[0046] Carbon dioxide absorption equivalent = (number of moles of carbon dioxide absorbed) / (number of moles of absorbent)

[0047] That is, this is the value of the equivalent amount of carbon dioxide absorbed relative to the amount of absorbent added.

[0048] The absorption equivalent can be 0.7 or more, or it can be 0.75 or more, 0.8 or more, 0.9 or more, 1.0 or more, 1.3 or more, or 1.5 or more.

[0049] In one embodiment, carbon dioxide can react with the imidazole anion of the absorbent to form a carbamate (reaction 1), and can also react with an alcohol to form a carbonate (reaction 2), thus exhibiting higher carbon dioxide absorption performance than the prior art.

[0050] [Reaction Formula 1]

[0051] CO2+ [cation] + [Imidazole-N] - ]→[cations] + [Imidazole-N-CO2] - ]

[0052] [Reaction 2]

[0053] CO2+ [cation] + [Imidazole-N-CO2] - ] + R-OH → [cation] + H-Imidazole + -N-CO2 - [RO-CO2] -

[0054] Another specific embodiment provides a carbon dioxide supply agent comprising a compound formed by reacting a carbon dioxide absorbent with carbon dioxide and an aliphatic carbonate, wherein the carbon dioxide absorbent comprises the ionic liquid containing an imidazole anion and an aliphatic alcohol.

[0055] The compound formed by reacting the carbon dioxide absorbent with carbon dioxide can be a compound represented by the following chemical formula 2.

[0056] [Chemical Formula 2]

[0057]

[0058] In the chemical formula 2, the R 1 R 2 and R 3 The above-mentioned content can be applied.

[0059] Another specific embodiment provides a method for separating carbon dioxide, the method comprising the steps of: contacting a carbon dioxide absorbent with a mixture containing carbon dioxide at a temperature of 20-80°C, wherein the carbon dioxide absorbent comprises an ionic liquid containing an imidazole anion and an aliphatic alcohol.

[0060] At this time, the temperature conditions are not necessarily limited to the above range and can be adjusted to a suitable temperature range for carbon dioxide absorption, such as 20-60°C, 25-55°C, 30-50°C, or 40°C. Furthermore, the step can be performed under pressure conditions such as 0.1-2.0 bar, 0.5-2.0 bar, 0.5-1.5 bar, 0.7-1.3 bar, or 1.0 bar, but the pressure conditions for the step are not limited to these.

[0061] The method for separating carbon dioxide may further include the following step: heat-treating the carbon dioxide absorbent for 30-250 minutes at a temperature of 70-150°C and an N2 flow rate of 100-300 ml / min (cc / min) to desorb the carbon dioxide adhering to the absorbent. The temperature conditions are not necessarily limited to the above ranges; for example, heat treatment can be performed at 80-130°C, 80-120°C, 80-110°C, 85-120°C, 85-110°C, or 90-110°C. Furthermore, the time conditions are not necessarily limited to the above ranges; for example, heat treatment can be performed for 30-210 minutes, 50-210 minutes, 60-250 minutes, 60-200 minutes, or 60-180 minutes. Additionally, the N2 flow rate is not necessarily limited to the above ranges; for example, it can be performed at 150-250 ml / min, 180-220 ml / min, or 200 ml / min.

[0062] Compared to conventional amine-based absorbents (e.g., MEA), the carbon dioxide desorption step according to one embodiment can be performed at a lower temperature and in a shorter time. Specifically, in the carbon dioxide absorbent according to one embodiment, by using an alcohol solvent to reduce the heat capacity and simultaneously generating urethane and carbonate, the regeneration energy is significantly reduced compared to existing absorbents, resulting in very high carbon dioxide desorption efficiency.

[0063] In addition, the method for separating carbon dioxide can be a method of continuously separating carbon dioxide by sequentially repeating the following steps: contacting the carbon dioxide absorbent with carbon dioxide to absorb carbon dioxide; and desorbing the carbon dioxide attached to the absorbent.

[0064] In a method for separating carbon dioxide according to one embodiment, the viscosity after carbon dioxide absorption is significantly improved compared to the viscosity before absorption, thereby enabling significantly more efficient absorption and desorption of carbon dioxide. When using existing carbon dioxide absorbents that form urethane or carbonate esters, the viscosity of the reaction solution increases, thus reducing the efficiency of continuous carbon dioxide absorption reactions, and requiring prolonged high-temperature conditions for subsequent desorption. The carbon dioxide absorbent according to one embodiment, however, exhibits a decrease in viscosity after capture, thus making it more effective for both absorption and desorption of carbon dioxide. Detailed Implementation

[0065] The following examples and experimental examples are specifically illustrated and described. However, the examples and experimental examples described below are only for illustrating a part of a specific implementation, and the specific implementation is not limited thereto.

[0066] <Preparation of Ionic Liquids (ILs)>

[0067] 1. Preparation of IL-01

[0068] In a 100 mL round-bottom flask (RBF), 8.56 g (14.6 mmol) of dioctadecyl dimethyl ammonium chloride, 1.31 g (14.6 mmol) of imidazole sodium, and 25 mL of ethanol were added and stirred at room temperature for 2 hours. After the reaction mixture was dried under vacuum, 30 mL of acetone was added and the mixture was stirred for 1 hour. The resulting solid was then filtered, and the filtrate was dried under vacuum at 50 °C for 15 hours to obtain 8.21 g (91%) of clear oil.

[0069] 1 H NMR (500MHz), d-acetone (acetone), 25℃: δ = 7.41 (s, 1H), 6.89 (s, 2H), 3.50 (m, 4H), 3.25 (s, 6H), 1.85 (br, 4H), 1.35 (br, 60H), 0.89 (t, 6H)

[0070] 2. Preparation of IL-02

[0071] 10.00 g (17.0 mmol) of dioctadecyl dimethyl ammonium chloride, 2.38 g (17.0 mmol) of sodium benzimidazole, and 30 mL of ethanol were added to 100 mL of RBF and stirred at room temperature for 2 hours. After vacuum drying of the reaction mixture, 30 mL of acetone was added and stirred for 1 hour. The resulting solid was then filtered, and the filtrate was vacuum dried at 50 °C for 15 hours to obtain 10.50 g (93%) of a white solid.

[0072] 1 H NMR (500MHz), d-acetone, 25℃: δ = 7.90 (s, 1H), 7.51 (d, 2H), 6.85 (d, 2H), 3.48 (m, 4H), 3.21 (s, 6H), 1.85 (br, 4H), 1.35 (br, 60H), 0.87 (t, 6H)

[0073] 3. Preparation of IL-03

[0074] 10.0 g (121.0 mmol) of methylimidazole and 12.3 g (97.4 mmol) of 1,4-dibromobutane were added to 100 mL of RBF, and the mixture was heated to 100 °C and stirred for 6 hours. The reactants were then added to 100 mL of ethyl acetate and stirred for 2 hours to form a white solid. This white solid was filtered and dried under vacuum for 3 hours. Next, 16.9 g (121.0 mmol) of sodium benzimidazole and 50 mL of ethanol were added to the formed white solid, and the mixture was stirred at room temperature for 2 hours. The formed solid was filtered off, and the filtrate was then dried under vacuum at 50 °C for 15 hours to obtain 21.2 g (95%) of white solid.

[0075] 1 H NMR (500MHz), d-DMSO, 25℃: δ=9.15(br,2H),7.75(s,4H),7.70(s,2H),7.35(d,4H),6.75(d,2H),4.15(br,4H),3.83(s,6H),1.69(br,4H)

[0076] 4. Preparation of IL-04

[0077] 10.0 g (121.0 mmol) of methylimidazole and 12.3 g (97.4 mmol) of 1,4-dibromobutane were added to 100 mL of RBF, and the mixture was heated to 100 °C and stirred for 6 hours. The reactants were then added to 100 mL of ethyl acetate and stirred for 2 hours to form a white solid. This white solid was filtered and dried under vacuum for 3 hours. Next, 10.9 g (121.0 mmol) of sodium imidazolate and 50 mL of ethanol were added to the formed white solid, and the mixture was stirred at room temperature for 2 hours. The formed solid was filtered off, and the filtrate was then dried under vacuum at 50 °C for 15 hours to obtain 17.6 g (91%) of white solid.

[0078] 1 H NMR (500MHz), d-DMSO, 25℃: δ = 7.75 (s, 2H), 7.70 (s, 2H), 7.09 (s, 2H), 6.65 (s, 4H), 4.17 (br, 4H), 3.81 (s, 6H), 1.71 (br, 4H)

[0079] 5. Preparation of IL-05

[0080] 4.60 g (27.8 mmol) of tetraethylammonium chloride, 2.50 g (27.8 mmol) of imidazole sodium, and 10 mL of distilled water were added to 100 mL of RBF and stirred at room temperature for 2 hours. The mixture was then vacuum dried at 50 °C for 5 hours. Next, 20 mL of ethanol was added, and the mixture was stirred at room temperature for 2 hours to form a white solid. This white solid was removed, and the filtrate was vacuum dried at 50 °C for 15 hours to obtain 5.1 g (93%) of a high-viscosity yellow liquid.

[0081] 1 H NMR (500MHz), D2O, 25℃: δ = 7.63 (s, 1H), 7.04 (s, 2H), 3.12 (m, 8H), 1.15 (m, 12H)

[0082] 6. Preparation of IL-06

[0083] 4.63 g (16.7 mmol) of tetrabutylammonium chloride, 1.50 g (16.7 mmol) of sodium imidazole, and 10 mL of distilled water were added to 100 mL of RBF and stirred at room temperature for 2 hours, then dried under vacuum at 50 °C for 5 hours. Next, 20 mL of ethanol was added, and the mixture was stirred at room temperature for 2 hours to form a white solid. This white solid was removed, and the filtrate was then dried under vacuum at 50 °C for 15 hours to obtain 4.7 g (92%) of a high-viscosity yellow liquid.

[0084] 1H NMR (500MHz), D2O, 25℃: δ = 7.70 (s, 1H), 7.10 (s, 2H), 3.13 (m, 8H), 1.59 (m, 8H), 1.31 (m, 8H), 0.91 (m, 12H)

[0085] 7. Preparation of IL-07

[0086] 5.00 g (21.2 mmol) of decyltrimethylammonium chloride, 1.44 g (21.2 mmol) of imidazole sodium, and 10 mL of ethanol were added to 100 mL of RBF and stirred at room temperature for 2 hours. The mixture was then vacuum dried at 50 °C for 5 hours. Next, 20 mL of acetone was added, and the mixture was stirred at room temperature for 2 hours to form a white solid. This white solid was removed, and the filtrate was vacuum dried at 50 °C for 15 hours to obtain 5.05 g (89%) of a high-viscosity yellow liquid.

[0087] 1 H NMR (500MHz), d-DMSO, 25℃: δ = 7.13 (s, 1H), 6.69 (s, 2H), 3.28 (t, 2H), 3.01 (s, 9H), 1.65 (m, 2H), 1.30 (m, 14H), 0.87 (m, 3H)

[0088] 8. Preparation of IL-08

[0089] 10.0 g (121 mmol) of methylimidazole and 20.1 g (107 mmol) of 1,2-bis(2-chloroethoxy)ethane were added to 100 mL of RBF, and the mixture was heated to 100 °C and stirred for 6 hours. Next, the reactants were added to 100 mL of ethyl acetate and stirred for 2 hours to form a white solid. This white solid was filtered and dried under vacuum for 3 hours. 10.9 g (121.0 mmol) of sodium imidazolate and 50 mL of ethanol were added to the resulting pale yellow oil, and the mixture was stirred at room temperature for 2 hours. The resulting solid was filtered off, and the filtrate was then dried under vacuum at 50 °C for 15 hours to obtain 24.2 g (97%) of pale yellow oil.

[0090] 1 H NMR (500MHz), d-DMSO, 25℃: δ = 7.71 (s, 4H), 7.09 (s, 2H), 6.66 (s, 4H), 4.30 (br, 4H), 3.85 (s, 6H), 3.73 (br, 4H), 3.52 (s, 4H)

[0091] 9. Preparation of IL-09

[0092] 10.0 g (121 mmol) of methylimidazole and 20.1 g (107 mmol) of 1,2-bis(2-chloroethoxy)ethane were added to 100 mL of RBF, and the mixture was heated to 100 °C and stirred for 6 hours. Next, the reactants were added to 100 mL of ethyl acetate and stirred for 2 hours to form a white solid. This white solid was filtered and dried under vacuum for 3 hours. 16.9 g (121.0 mmol) of sodium benzimidazole and 50 mL of ethanol were added to the resulting pale yellow oil, and the mixture was stirred at room temperature for 2 hours. The resulting solid was filtered off, and the filtrate was then dried under vacuum at 50 °C for 15 hours to obtain 24.8 g (95%) of pale yellow oil.

[0093] 1 H NMR (500MHz), d-DMSO, 25℃: δ = 9.15 (br, 2H), 7.75 (s, 2H), 7.70 (d, 4H), 6.77 (d, 4H), 4.30 (br, 4H), 3.85 (s, 6H), 3.71 (br, 4H), 3.51 (s, 4H)

[0094] 10. Preparation of IL-10

[0095] 2.00 g (3.41 mmol) of dioctadecyl dimethyl ammonium chloride, 0.69 g (3.14 mmol) of sodium theophylline, and 10 mL of ethanol were added to 50 mL of RBF, and the mixture was stirred at room temperature for 2 hours. After vacuum drying of the reaction mixture, 30 mL of acetone was added, and the mixture was stirred for 1 hour. The resulting solid was filtered, and the filtrate was then vacuum dried at 50 °C for 15 hours to obtain 2.26 g (91%) of a white solid.

[0096] 1 H NMR (500MHz), d-acetone, 25℃: δ=7.10(s,1H),3.38(s,3H),3.33(s,6H),3.23(br,4H),3.18(s,6H),1.62(br,4H),1.35(br,60H),0.87(t,6H)

[0097] 11. Preparation of IL-11

[0098] 5.26 g (37.6 mmol) of choline chloride, 3.77 g (37.6 mmol) of imidazole sodium, and 20 mL of ethanol were added to 100 mL of RBF and stirred at room temperature for 2 hours. The solid formed in the reaction mixture was filtered, and the filtrate was then vacuum dried at 50 °C for 15 hours to obtain 5.92 g (92%) of a pale yellow oil.

[0099] 1H NMR (500MHz), d-DMSO, 25℃: δ = 7.69 (s, 1H), 7.05 (s, 2H), 3.96 (br, 2H), 3.41 (br, 2H), 3.11 (s, 9)

[0100] 12. Preparation of IL-12

[0101] 2.0 g (8.8 mmol) of tetraethylphosphonium bromide, 1.0 g (8.8 mmol) of imidazole sodium, and 10 mL of distilled water were added to 100 mL of RBF and stirred at room temperature for 2 hours. The mixture was then vacuum dried at 50 °C for 5 hours. Next, 20 mL of ethanol was added, and the mixture was stirred at room temperature for 2 hours to form a white solid. This white solid was removed, and the filtrate was vacuum dried at 50 °C for 15 hours to obtain 1.75 g (93%) of a high-viscosity yellow liquid.

[0102] 1 H NMR (500MHz), D2O, 25℃: δ = 7.69 (s, 1H), 7.08 (s, 2H), 2.14 (m, 8H), 1.16 (m, 12H)

[0103] 13. Preparation of IL-13

[0104] 3.00 g (21.4 mmol) of choline chloride, 3.16 g (22.5 mmol) of benzimidazole sodium, and 12 mL of ethanol were added to 50 mL of RBF and stirred at room temperature for 2 hours. The solid formed in the reaction mixture was filtered, and the filtrate was then vacuum dried at 50 °C for 15 hours to obtain 4.4 g (93%) of a pale yellow oil.

[0105] 1 H NMR (500MHz), d-DMSO, 25℃: δ = 7.77 (s, 1H), 7.35 (d, 2H), 6.80 (d, 2H), 3.88 (br, 2H), 3.41 (br, 2H), 3.11 (s, 9)

[0106] 14. Preparation of IL-14

[0107] 5.00 g (32.5 mmol) of betaine hydrochloride, 2.93 g (32.5 mmol) of imidazole sodium, and 20 mL of ethanol were added to 50 mL of RBF and stirred at room temperature for 2 hours. The solid formed in the reaction mixture was filtered, and the filtrate was then vacuum dried at 50 °C for 15 hours to obtain 5.5 g (90%) of white solid.

[0108] 1H NMR (500MHz), d-DMSO, 25℃: δ = 7.61 (s, 1H), 7.00 (s, 2H), 3.61 (s, 2H), 3.13 (s, 9)

[0109] The structural formulas of the ionic liquids IL-01 to IL-14 prepared as described above are shown in Table 1 below.

[0110] [Table 1]

[0111]

[0112]

[0113] <Examples 1 to 16>

[0114] Carbon dioxide absorbents according to Examples 1 to 16 were prepared, comprising an alcohol solvent and 30% by weight of the ionic liquid (IL) prepared above. The ionic liquids and alcohol solvents contained in Examples 1 to 16 are described in Table 2.

[0115] <Comparative Examples 1 to 6>

[0116] Carbon dioxide absorbents according to Comparative Examples 1 to 5 were prepared, comprising water and 30% by weight of the ionic liquid (IL) prepared above. In Comparative Example 6, monoethanolamine (MEA), a 30% by weight aqueous solution conventionally used as a carbon dioxide absorbent, was prepared. The types of ionic liquids and solvents contained in Comparative Examples 1 to 6 are listed in Table 3 below.

[0117] <Experimental Example 1> Evaluation of Carbon Dioxide Absorption Performance

[0118] To evaluate the carbon dioxide absorption performance of the carbon dioxide absorbents according to Examples 1 to 16 and Comparative Examples 1 to 6, the carbon dioxide absorption performance was measured using a vapor-liquid equilibration (VLE) apparatus. The VLE apparatus consisted of a carbon dioxide storage cylinder (150 mL), a constant-temperature water bath, a stainless steel absorption reactor (73 mL) equipped with a thermometer, an electronic pressure gauge, and a stirrer. The cylinder and reactor were maintained at a constant temperature of 40°C using the constant-temperature water bath and a heating block, and the absorption capacity was measured. The measurement error range for the reactor was ±0.1°C and ±0.01 bar.

[0119] The evaluation of carbon dioxide absorption performance was conducted as follows. First, the interior of the carbon dioxide storage tank and the absorption reactor was fully purged with nitrogen. Then, carbon dioxide was filled into the storage tank and maintained at 1 bar and 40°C. Next, 30% by weight of an absorbent solution (6.0 g) according to Examples 1 to 16 and Comparative Examples 1 to 6 was added to the inside of the absorption reactor, and the temperature was maintained at 40°C. The valves connecting the tank and the reactor were then opened, and the pressure was measured after absorption equilibrium was reached. The equilibrium pressure was measured in 30-minute intervals, and the above process was repeated until there was no pressure change between the tank and the reactor. Next, the number of moles of carbon dioxide captured according to the pressure change was calculated using the ideal gas equation. The calculated number of moles of captured carbon dioxide divided by the number of moles of absorbent is shown in Tables 2 and 3 below.

[0120] <Experimental Example 2> Evaluation of Carbon Dioxide Desorption Performance

[0121] To evaluate the carbon dioxide desorption performance of the carbon dioxide absorbents according to Examples 1 to 16 and Comparative Examples 1 to 6, the carbon dioxide desorption performance was evaluated using a carbon dioxide desorption apparatus based on the samples evaluated in Experimental Example 1. The carbon dioxide desorption apparatus used included a nitrogen flow rate control device, a heating block, a magnetic stirrer, and an N2 bubbler. The absorbent was kept at a constant temperature using the heating block, and the desorption performance was evaluated at 90-130°C while N2 bubbling (200 mL / min). The measurement error range of the desorption reactor was ±1°C.

[0122] The evaluation of carbon dioxide desorption performance was conducted as follows. First, 3.0 g of the carbon dioxide absorbent used in the gas-liquid balance evaluation according to Examples 1 to 16 and Comparative Examples 1 to 6 in Experimental Example 1 was added to the reactor. Then, N2 was bubbled and stirred at a rate of 200 mL / min using a flow rate control device. Next, the reactor was heated to the target temperature, and small samples were taken every 1 hour. 1 1H NMR measurements were performed to observe the anion (imidazole anion) region. 1 The 1H NMR peak shift continues until the same peak as the absorbent before absorption is observed. 1 The 1H NMR peak shift was used to confirm the temperature and time at which the desorption was completed, thus evaluating the desorption performance. The results of the desorption performance evaluation are shown in Tables 2 and 3 below.

[0123] [Table 2]

[0124]

[0125]

[0126] [Table 3]

[0127]

[0128] As a result, it can be confirmed from Tables 2 and 3 that the carbon dioxide absorbents according to the embodiments all exhibit excellent absorption performance of 0.70 or higher. In particular, the absorbents of some embodiments, such as Examples 5, 9, and 10, have absorption performance exceeding 1.00. Therefore, it can be confirmed that the carbon dioxide absorption equivalent is higher than the added equivalent of the absorbent, and thus it is very effective.

[0129] On the other hand, the absorbent conventionally used as a carbon dioxide absorbent in Comparative Example 6 had an absorption performance of 0.53, exhibiting significantly lower performance compared to the absorbents in the examples. Furthermore, when the ionic liquid IL-01 was used with an alcohol solvent in Examples 1 and 2, the absorption performance was 1.01 and 1.03, respectively, demonstrating excellent performance with a higher carbon dioxide absorption equivalent compared to the added absorbent equivalent. However, when used in the aqueous phase of Comparative Example 1, the absorption performance was 0.20, indicating ineffective carbon dioxide absorption.

[0130] Furthermore, the absorbents of Comparative Examples 2 to 5 all exhibited absorption performance of 0.78 or higher, thus demonstrating absorption performance similar to that of the absorbents in the Examples. However, the absorbents of Comparative Examples 2 to 5 all formed solids after absorbing carbon dioxide, making it difficult to desorb carbon dioxide, and causing fouling or plugging during desorption, thus limiting their application in processes. In addition, the absorbent of Comparative Example 6, which was previously used as a carbon dioxide absorbent, did not desorb at a temperature of 100°C, indicating that the absorbent of Comparative Example 6 requires a temperature of 130°C or higher to desorb the absorbed carbon dioxide.

[0131] On the other hand, the absorbents of Examples 1 to 16 can be easily desorbed at a temperature of 90-100°C, and most of the examples can be desorbed in a short time of 3 hours. In particular, Examples 4 and 5 can be desorbed in a very short time of 1.5 hours, thus confirming that the carbon dioxide desorption performance is very excellent.

[0132] Therefore, the absorbent according to the above embodiment not only exhibits higher capture performance than the addition equivalent of the absorbent, but also desorbs carbon dioxide very easily due to its low regeneration energy, thus being very effective in the absorption and desorption of carbon dioxide.

[0133] <Experimental Example 3> Nuclear Magnetic Resonance (NMR) Analysis

[0134] The absorbent according to the embodiments uses an ionic liquid containing an imidazole anion and an aliphatic alcohol, simultaneously forming a carbamate generated by the reaction of the anion with carbon dioxide and an alkyl carbonate generated by the reaction of the alcohol. This allows for the absorption of carbon dioxide with a higher capture performance than the added equivalent of the absorbent, thus proving effective. To confirm this through NMR analysis, the absorbent of Example 1 before and after carbon dioxide absorption was analyzed. 1 H NMR and 13 C NMR analysis was performed, and the results are presented. Figure 1 and Figure 2 middle.

[0135] pass Figure 1 It can be confirmed that after the carbon dioxide absorption reaction, the imidazoline anion of IL-01 generates carbamate anions. 1 The 1H NMR proton peaks appeared at 7.5 ppm and 7.7 ppm, and a peak downshift of 0.3 ppm was observed compared to before the absorption reaction. The carbonate produced by the alcohol (2-ethylhexanol) as a solvent... 1 A new proton peak was observed at 3.7 ppm in the 1H NMR spectrum. Furthermore, this was confirmed after bubbling with N2 at 90°C for 3 hours. 1 The 1H NMR peak shifts to the same position as the imidazole anion before absorption, and the carbonate produced by the alcohol (2-ethylhexanol) as the solvent... 1 The H NMR peak disappeared. This confirms that the absorbent can be regenerated by ensuring that the same compound as the absorbent before absorption is obtained through carbon dioxide desorption.

[0136] pass Figure 2 It can be confirmed that after the carbon dioxide absorption reaction, IL-01... 13 The C10 NMR analysis results not only revealed the peak shift of the imidazole carbon caused by the formation of carbamate from the imidazole anion, but also two new peaks in the 156-160 ppm region. Therefore, it can be confirmed that... 1 The 1H NMR analysis results were consistent; IL-01 reacted with carbon dioxide to simultaneously produce carbamate and carbonate. Furthermore, desorption was performed at desorption temperatures of 60°C and 100°C. 13 The results of C NMR analysis show that carbonates can desorb carbon dioxide at lower temperatures than carbamates.

[0137] Next, to compare the desorption performance with that of the existing commercial absorbent MEA, carbon dioxide was absorbed using the absorbent of Comparative Example 6, and then desorbed at 130°C for 1 hour, 2 hours, and 3 hours, respectively, followed by [further testing / processing]. 13C NMR analysis was performed, and the results are presented. Figure 3 As a result, in Comparative Example 6, even at a high temperature of 130°C, carbon dioxide was not desorbed after 1 hour and 2 hours. It was only after approximately 3 hours of desorption that carbon dioxide was desorbed and the MEA was regenerated. This confirms that the absorbent of the embodiments described has very high desorption performance compared to Comparative Example 6, which is a commercially available absorbent.

[0138] <Experimental Example 4> Evaluation of viscosity before and after carbon dioxide absorption

[0139] The problem with existing wet carbon dioxide absorbents is that their viscosity increases after absorbing carbon dioxide, leading to mass transfer and making it difficult to desorb the absorbed carbon dioxide. Therefore, to confirm the desorption performance of the absorbents in Examples 1 to 16, the viscosity before and after carbon dioxide absorption was evaluated. A Brookfield viscometer (model DV2TCP) and a CPA-40z cone rotor were used for the viscosity evaluation.

[0140] First, adjust the distance between the conical rotor and the sample cup to ensure sufficient space for the absorbent sample to enter. Then, add 0.5 mL of the absorbent from Examples 1 to 16 to the sample cup, and fix the sample cup by rotating the lever after connecting it to the viscometer. The viscosity measurement conditions are set to 30-200 rpm, with a stop time of 1 minute, and the viscosity is measured at a sample cup temperature of 40°C. The viscosity is calculated directly in the device by measuring the torque generated in the spring connected to the rotor. The viscosity is calculated by averaging three Brinell viscosity measurements on a single sample, and the results are shown in Table 4 below.

[0141] [Table 4]

[0142]

[0143]

[0144] As a result, Table 4 confirms that the viscosity of the absorbents in Examples 1 to 3 decreased after absorption compared to before absorption. Furthermore, the absorbents in Examples 4 to 16 also exhibited viscosity as low as almost 30 cP after absorption. Therefore, the carbon dioxide absorbents according to these examples do not exhibit problems due to increased viscosity after carbon dioxide absorption, thus demonstrating ease of vaporization of liquid carbon dioxide and re-desorption of the carbon dioxide.

[0145] The above examples and experimental examples have provided a detailed description of a specific implementation scheme. However, the scope of a specific implementation scheme is not limited to the specific embodiment and should be interpreted according to the claims.

Claims

1. A carbon dioxide absorbent comprising: Ionic liquids containing imidazole anions; and Aliphatic alcohols, in, The ionic liquid contains a variety selected from and One or more cations in it.

2. The carbon dioxide absorbent according to claim 1, wherein, The imidazole anion is a compound represented by the following chemical formula 1: [Chemical Formula 1] In the chemical formula 1, The R 1 R 2 and R 3 Each is independently hydrogen, substituted or unsubstituted C 1-10 Alkyl, substituted or unsubstituted C 1-10 Alkyl carbonyl, substituted or unsubstituted C 1-10 Alkoxy, substituted or unsubstituted C 3-8 Cycloalkyl groups, heterocycloalkyl groups comprising 5-10 atoms of substituted or unsubstituted heteroatoms selected from N, O, and S, and substituted or unsubstituted C atoms. 5-10 aryl or heteroaryl containing 5-10 atoms of substituted or unsubstituted heteroatoms selected from N, O and S, or The R 1 and R 2 Together with the carbon atoms they are bonded to, they form substituted or unsubstituted C atoms. 3-8 Cycloalkyl groups, heterocycloalkyl groups comprising 5-10 atoms of substituted or unsubstituted heteroatoms selected from N, O, and S, and substituted or unsubstituted C atoms. 5-10 Aryl groups, heteroaryl groups comprising 5-10 atoms, either substituted or unsubstituted, of one or more heteroatoms selected from N, O, and S. The substitution is selected from halogen, oxo group, cyano group, amino group, nitrile group, C group, etc. 1-10 Alkyl, C 1-10 alkyl carbonyl and C 1-10 One or more substituents in the alkoxy group are substituted.

3. The carbon dioxide absorbent according to claim 2, wherein, The R 1 R 2 and R 3 Each is independently hydrogen, substituted or unsubstituted C 1-5 Alkyl, substituted or unsubstituted C 1-5 Alkyl carbonyl or substituted or unsubstituted C 1-5 alkoxy, or The R 1 and R 2 Together with the carbon atoms they are bonded to, they form substituted or unsubstituted C atoms. 5-8 Cycloalkyl groups, heterocycloalkyl groups containing 5-8 atoms of substituted or unsubstituted heteroatoms selected from N, O, and S, and substituted or unsubstituted C atoms. 5-8 Aryl groups, heteroaryl groups comprising 5-8 atoms, either substituted or unsubstituted, of one or more heteroatoms selected from N, O, and S. The substitution is selected from halogen, oxo group, and C, respectively. 1-5 One or more substituents in the alkyl group are used for substitution.

4. The carbon dioxide absorbent according to claim 1, wherein, The aliphatic alcohol is an aliphatic monohydric alcohol or an aliphatic polyhydric alcohol.

5. The carbon dioxide absorbent according to claim 1, wherein, The aliphatic alcohol is C 2-10 Aliphatic alcohols.

6. The carbon dioxide absorbent according to claim 1, wherein, The aliphatic alcohol has a boiling point of 130°C or higher.

7. The carbon dioxide absorbent according to claim 1, wherein, The heat capacity of the aliphatic alcohol is below 4.0 kJ / kg℃.

8. The carbon dioxide absorbent according to claim 1, wherein, The carbon dioxide absorption equivalent expressed by Equation 1 below is 0.7 or higher: [Formula 1] Carbon dioxide absorption equivalent = (number of moles of carbon dioxide absorbed) / (number of moles of absorbent).

9. A carbon dioxide supply agent comprising a compound formed by reacting the carbon dioxide absorbent of claim 1 with carbon dioxide, and an aliphatic carbonate.

10. The carbon dioxide supply agent according to claim 9, wherein, The compound formed by reacting the carbon dioxide absorbent with carbon dioxide is a compound represented by the following chemical formula 2: [Chemical Formula 2] In the chemical formula 2, The R 1 R 2 and R 3 Same as defined in claim 2.

11. A method for separating carbon dioxide, comprising the following steps: The carbon dioxide absorbent is contacted with a mixture containing carbon dioxide at a temperature of 20-80°C. The carbon dioxide absorbent comprises an ionic liquid containing an imidazole anion and an aliphatic alcohol. The ionic liquid contains a variety of... and One or more cations in it.

12. The method for separating carbon dioxide according to claim 11, wherein, The method further includes the following steps: heat-treating the carbon dioxide absorbent at a temperature of 70-150°C for 30-250 minutes to desorb the carbon dioxide adhering to the absorbent.

13. The method for separating carbon dioxide according to claim 12, wherein, The contact and desorption steps are repeated sequentially to continuously separate carbon dioxide.

Images