KR20230114191A - Carbon dioxide absorbent containing phenolate-based ionic liquid and aliphatic alcohol and carbon dioxide separation method using same - Google Patents

Abstract

The present disclosure provides a carbon dioxide absorbent containing an ionic liquid containing a choline-based cation and a phenolate-based anion and an aliphatic alcohol, and a method for separating carbon dioxide using the same. The carbon dioxide absorbent of the present disclosure is thermally and chemically stable, It is environmentally friendly because it can reduce by-products emitted into the atmosphere, and the carbon dioxide separation method using this is an economical method that can save energy with low renewable energy.

Description

Carbon dioxide absorbent containing phenolate-based ionic liquid and aliphatic alcohol and carbon dioxide separation method using the same

The present disclosure relates to a carbon dioxide absorbent including an ionic liquid including a choline-based cation and a phenolate-based anion and an aliphatic alcohol.

In addition, the present disclosure relates to a method for separating carbon dioxide using the carbon dioxide absorbent.

BACKGROUND OF THE INVENTION Due to the rapid progress of economic development and industrialization worldwide, the consumption of fossil fuel, which is a major source of energy, has been continuously increasing. In particular, carbon dioxide (CO ₂ ) accounts for the largest portion of the major greenhouse gases formed in the process of burning fossil fuels and converting them into energy, and is known to have a close relationship with global warming. Due to the increase and long-term use of energy, the global warming problem has been intensified and global attention has been focused. In order to solve this problem, the research field related to carbon dioxide has also become important.

As a method for separating carbon dioxide from exhaust gas and natural gas of chemical plants, power plants, and large boilers, absorption, adsorption, separation membrane, deep cooling, and the like are used. In particular, when the concentration of carbon dioxide emitted is low, an absorption method or an adsorption method is often used. The absorption method or adsorption method is widely used industrially because it can selectively separate only some gases that are well absorbed or adsorbed by the absorbent or adsorbent. However, the absorbent and adsorbent are chemically transformed during the separation process, so periodic replacement is required. .

When using a solid adsorbent, it is advantageous to apply it when the adsorbent replacement cycle is long because the adsorbent has little chemical transformation. Although widely used for gas separation, there is a disadvantage that the absorbent is chemically modified.

As carbon dioxide absorbents, aqueous solutions of amines such as monoethanolamine (MEA), N-methyldiethanolamine (NDEA), and diethanolamine (DEA) are generally most widely used. This is because, after forming a chemical bond with carbon dioxide, when heat is applied, the bond is broken, and carbon dioxide is degassed and recovered, and the absorbent can be regenerated.

However, the process using an amine aqueous solution has some serious problems. In particular, MEA belonging to primary amines is used as a 30% by weight aqueous solution, but has the disadvantage of requiring high regeneration energy in the desorption process after absorbing carbon dioxide due to the high heat capacity of water (4.2 kJ/kg K). Irreversible decomposition of amine due to high temperature used to break the chemical bond between absorbent and absorbent, problem of decomposition of amine by impurities such as SOx and NOx contained in the absorption gas, performance of absorbent according to irreversible decomposition of the amine Problems of deterioration and replenishment of the absorbent, problems of corrosion of the absorber by amine itself or decomposition products, and problems of contamination of gaseous carbon dioxide regenerated by the vapor pressure of the absorbent have been pointed out as disadvantages.

An alternative to this is an ionic liquid. Ionic liquids contain large organic symmetric cations, such as quaternary ammonium, imidazolium, pyridinium, and phosphonium ions, and relatively asymmetric small sized [ Cl] ^- , [Br] ^- , [I] ^- , [BF ₄ ] ^- , [PF ₆ ] ^- , [Tf ₂ N] ^- composed of inorganic substances such as or organic substances such as [RCO ₂ ^{] -} It is composed of negative ions. Due to the characteristics of ionic liquids that can be converted into various properties through infinite combinations of cations, anions, and functional groups, they are also called "designer solvents."

Based on imidazolium cations and [Cl] ^- , [BF ₄ ] ^- , [PF ₆ ] ^- , [CH ₃ SO ₃ ] ^- , [CF ₃ BF ₃ ] ^- , [C ₂ F ₅ BF ₃ ] ^- anions In the case of ionic liquids containing fluorine, high CO ₂ absorption capacity can be expected, but they are difficult to biodegrade, which is environmentally harmful, and the price of fluorinated anions is very expensive. .

Therefore, it is a liquid material with optimal properties for carbon dioxide separation, thermally stable with no possibility of atmospheric emission, chemically stable to reduce atmospheric emission of decomposition products, and an absorbent capable of desorbing carbon dioxide with low renewable energy. need to develop

Korean registered patent 10-0975897 Korean Registered Patent No. 10-1122714

An object of the present disclosure is to provide an economical carbon dioxide absorbent that is thermally and chemically stable, can reduce atmospheric emission of decomposition products when applied to a process, and can desorb carbon dioxide with low renewable energy.

Another object of the present disclosure is to provide a carbon dioxide absorbent that does not produce solids after absorbing carbon dioxide, does not clog pipes by controlling viscosity increase, and has excellent processability.

Another object of the present disclosure is to provide an eco-friendly and economical method for separating carbon dioxide using the carbon dioxide absorbent.

The present disclosure relates to an ionic liquid comprising a choline-based cation and a phenolate-based anion; And aliphatic alcohol; it provides a carbon dioxide absorbent containing.

The carbon dioxide absorbent according to an embodiment of the present disclosure may include 5 to 70% by weight of the ionic liquid and 30 to 95% by weight of the aliphatic alcohol.

The phenolate-based anion according to the present disclosure may be a compound represented by Formula 1 or 2 below.

[Formula 1]

[Formula 2]

[In Chemical Formulas 1 and 2,

R ₁ to R ₉ are each independently hydrogen, amino, carboxamido, C1-C10 alkyl, C1-C10 alkylcarbonyl, C1-C10 alkoxy or C3-C8 cycloalkyl;

Wherein amino, carboxamido, alkyl, alkylcarbonyl, alkoxy and cycloalkyl are halogen, cyano, amino, nitro, C1-C10 alkyl, C1-C10 alkylcarbonyl, C1-C10 alkoxy and C3-C8 cyclo It may be substituted with one or two or more substituents selected from alkyl.]

Specifically, R ₁ to R ₉ are each independently hydrogen, amino, carboxamido, C1-C5alkyl, C1-C5alkylcarbonyl or C1-C5alkoxy, wherein amino, carboxamido, alkyl, alkyl Carbonyl and alkoxy may be substituted with one or more substituents selected from halogen, cyano, amino, nitro, C1-C10 alkyl, C1-C10 alkylcarbonyl, C1-C10 alkoxy and C3-C8 cycloalkyl. .

More specifically, R ₁ to R ₉ are each independently hydrogen, amino or carboxamido, provided that at least one is amino or carboxamido, and the amino or carboxamido is C1-C3alkylcarbonyl can be substituted.

The aliphatic alcohol according to an embodiment of the present disclosure may be an aliphatic monohydric alcohol or an aliphatic polyhydric alcohol, may be a C2-C10 aliphatic alcohol, and may have a boiling point of 120° C. or higher at 1 atmospheric pressure.

In addition, the aliphatic alcohol may have a heat capacity of 4.0 kJ/kg·K or less.

The carbon dioxide absorbent according to an embodiment of the present disclosure may have a carbon dioxide absorption equivalent represented by Equation 1 below of 0.7 or more.

[Equation 1]

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

In addition, the present disclosure provides a carbon dioxide separation method using the above-described carbon dioxide absorbent, and the carbon dioxide separation method according to the present disclosure includes a first step of contacting the carbon dioxide absorbent with a mixture containing carbon dioxide; and a second step of heat-treating the carbon dioxide absorbent to desorb carbon dioxide attached to the absorbent.

The first step of the carbon dioxide separation method may be performed at 20 ° C to 80 ° C, and the second step may be performed at 70 ° C to 150 ° C for 30 to 250 minutes. As a unit process, it may be a method of continuously separating carbon dioxide by repeating the unit process two or more times.

The carbon dioxide absorbent according to the present disclosure is thermally and chemically stable, so when applied to a process, it is possible to reduce the emission of decomposition products into the atmosphere, and it is very economical because it can desorb carbon dioxide with low renewable energy, and it is very economical to generate solids after absorbing carbon dioxide. There is no viscosity increase phenomenon is controlled, so it can be easily applied industrially.

Hereinafter, an ionic liquid containing a choline-based cation and a phenolate-based anion of the present disclosure; And aliphatic alcohol; a carbon dioxide absorbent containing and a carbon dioxide separation method using the same will be described in detail.

The singular form used in this disclosure may be intended to include the plural form as well, unless the context dictates otherwise.

As described in the present disclosure, “comprising” is an open-ended description having the same meaning as expressions such as “comprises”, “includes”, “has” or “characterized by”, and elements not additionally listed, No materials or processes are excluded.

"Alkyl" as described in this disclosure includes both straight-chain and branched forms, and may be from 1 to 20 carbon atoms, preferably from 1 to 10 carbon atoms.

“Halogen” and “halo” as used in this disclosure means fluorine, chlorine, bromine or iodine.

“Alkoxy” as described in this disclosure means -OCH ₃ , -OCH ₂ CH ₃ , -O(CH ₂ ) ₂ CH ₃ , -O(CH ₂ ) ₃ CH ₃ , -O(CH ₂ ) ₄ CH ₃ , -O (CH ₂ ) ₅ CH ₃ and the like; wherein alkyl is as defined above.

As used herein, "alkylcarbonyl" may mean -(C(=0)-alkyl), where alkyl is as defined above. In addition, "alkylcarbonyl" may mean a carbonyl containing C1-10 alkyl, that is, -(C(=O)-C1-10 alkyl), and as an example, methylcarbonyl (acetyl, -( C(=O)CH ₃ )), ethylcarbonyl, n-propylcarbonyl, iso-propylcarbonyl, n-butylcarbonyl, sec-butylcarbonyl, isobutylcarbonyl, tert-butylcarbonyl, n -octylcarbonyl, cyclopropylcarbonyl, cyclobutylcarbonyl, cyclopentylcarbonyl, or cyclohexylcarbonyl, etc. may be included, but is not limited thereto.

As used in this disclosure, “nitro” means -NO ₂ , “cyano”” means -CN, “amino” means -NR ₂ , and “carboxamido” means -(C( =O)NR ₂ ), where R means hydrogen or hydrocarbyl.

The present disclosure relates to an ionic liquid comprising a choline-based cation and a phenolate-based anion; and an aliphatic alcohol. The carbon dioxide absorbent of the present disclosure is thermally and chemically stable, so that when applied to a process, emission of decomposition products into the atmosphere can be reduced, and carbon dioxide can be desorbed with low renewable energy. It is very economical and can be easily applied industrially because there is no generation of solids after absorption of carbon dioxide and the phenomenon of viscosity increase is controlled.

The carbon dioxide absorbent according to an embodiment of the present disclosure may include 5 to 70% by weight of the ionic liquid and 30 to 95% by weight of the aliphatic alcohol, preferably 10 to 50% by weight of the ionic liquid and 30 to 95% by weight of the aliphatic alcohol. Silver may be included in 50 to 90% by weight.

The phenolate-based anion according to the present disclosure may be a compound represented by Formula 1 or 2 below.

[Formula 1]

[Formula 2]

[In Chemical Formulas 1 and 2,

R ₁ to R ₉ are each independently hydrogen, amino, carboxamido, C1-C10 alkyl, C1-C10 alkylcarbonyl, C1-C10 alkoxy or C3-C8 cycloalkyl;

Wherein amino, carboxamido, alkyl, alkylcarbonyl, alkoxy and cycloalkyl are halogen, cyano, amino, nitro, C1-C10 alkyl, C1-C10 alkylcarbonyl, C1-C10 alkoxy and C3-C8 cyclo It may be substituted with one or two or more substituents selected from alkyl.]

Specifically, R ₁ to R ₉ are each independently hydrogen, amino, carboxamido, C1-C5alkyl, C1-C5alkylcarbonyl or C1-C5alkoxy, wherein amino, carboxamido, alkyl, alkyl Carbonyl and alkoxy may be substituted with one or more substituents selected from halogen, cyano, amino, nitro, C1-C10 alkyl, C1-C10 alkylcarbonyl, C1-C10 alkoxy and C3-C8 cycloalkyl. .

More specifically, R ₁ to R ₉ are each independently hydrogen, amino, carboxamido or C1-C3alkyl, wherein amino, carboxamido and alkyl are C1-C5alkyl, C1-C5alkylcarbonyl and It may be substituted with one or two or more substituents selected from C1-C5 alkoxy.

More specifically, R ₁ to R ₉ are each independently hydrogen, amino or carboxamido, provided that at least one is amino or carboxamido, and the amino or carboxamido is C1-C3alkylcarbonyl can be substituted.

The phenolate-based anion according to the present disclosure may be a compound represented by Formula 3 or 4 below.

[Formula 3]

[Formula 4]

[In Chemical Formulas 3 and 4,

R ₁₁ and R ₁₂ are each independently -NH ₂ or -NHCOCH ₃ .]

The aliphatic alcohol according to an embodiment of the present disclosure may be an aliphatic monohydric alcohol or an aliphatic polyhydric alcohol, and specifically, the aliphatic polyhydric alcohol may have 2 to 6 hydroxyl groups, specifically 2 to 4 hydroxyl groups. there is.

The aliphatic alcohol according to an embodiment of the present disclosure may be a C2-C10 aliphatic alcohol, and may be, for example, a saturated aliphatic alcohol, an unsaturated aliphatic alcohol, or an alcohol containing a cyclic structure. It may be a C2-C10 straight or branched chain alcohol.

Specifically, the C2-C10 aliphatic alcohol is 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, diethylene glycol monoethyl ether, n-propyl alcohol, isopropyl alcohol, 1-butanol, 2-butanol, may be one or more selected from isobutyl alcohol, t-butyl alcohol, 2-pentanol, t-pentyl alcohol, 1-hexanol, allyl alcohol, propargyl alcohol, 2-butenyl alcohol and 3-butenyl alcohol However, it is not limited now.

The aliphatic alcohol may have a boiling point of 120 °C or more at 1 atm, specifically 140 °C to 250 °C, and more specifically 160 °C to 230 °C. Water used as a solvent for conventional carbon dioxide absorbents has a low boiling point of 100 ° C. or less, so there is a high possibility that decomposition products will be released into the atmosphere. However, the aliphatic alcohol solvent according to an embodiment of the present disclosure has a very high boiling point, so It has little possibility of release and is chemically stable, so the possibility of release of decomposition products into the atmosphere can be drastically reduced.

In addition, the aliphatic alcohol may have a heat capacity of 4.0 kJ/kg·K or less. The heat capacity is not necessarily limited to the above range, and may be 3.5 kJ/kg·K or less, 3.0 kJ/kg·K or less, 2.8 kJ/kg·K or less, or 2.5 kJ/kg·K or less. Amine-based absorbents (eg, MEA (mono-ethanolamine)), which are used as conventional carbon dioxide absorbents, are used as aqueous solutions of 30% by weight. There was a problem requiring high renewable energy. In addition, the amine-based absorbent is easily thermally decomposed or oxidatively decomposed by heat and oxygen, and decomposition products are released into the atmosphere, causing environmental problems. In comparison, the carbon dioxide absorbent according to an embodiment of the present disclosure uses an ionic liquid including a choline-based cation and a phenolate-based anion together with an alcohol solvent, thereby lowering the heat capacity and dramatically improving regenerative energy of the absorbent compared to the existing ones.

The cationic material of the ionic liquid included in the carbon dioxide absorbent according to an embodiment of the present disclosure is a choline-based cationic material and may be represented by Chemical Formula 5 below.

[Formula 5]

[In Formula 5,

L is C2-C10 alkylene;

R ₂₁ is hydrogen, C1-C20 alkyl or C1-C20 alkylcarbonyl;

R ₂₂ to R ₂₄ are each independently C1-C4 alkyl.]

Specifically, in Formula 5, L is C2-C6alkylene, R ₂₁ is hydrogen, C1-C10alkyl or C1-C10alkylcarbonyl, and R ₂₂ to R ₂₄ are each independently C1-C3alkyl.

More specifically, L in Formula 5 is C2-C4 alkylene, R ₂₁ is hydrogen, C1-C5 alkyl or C1-C5 alkylcarbonyl, and R ₂₂ to R ₂₄ are each independently C1-C2 alkyl.

In one embodiment of the present disclosure, the choline-based cationic material may be choline, acetylcholine, propionylcholine or butyrylcholine, specifically choline, but is not limited thereto.

The carbon dioxide absorbent according to an embodiment of the present disclosure may have a carbon dioxide absorption equivalent represented by Equation 1 below of 0.7 or more, preferably 0.72 to 1.5, and more preferably 0.75 to 1.5.

[Equation 1]

Carbon dioxide absorption equivalent = (number of moles of carbon dioxide absorbed) / (number of moles of ionic liquid)

Since the carbon dioxide absorbent according to an embodiment of the present disclosure can form carbamate by reacting carbon dioxide with phenolate-based anions of the absorbent (Scheme 1) and simultaneously react with alcohol to form carbonate (Scheme 2), conventional technology It can show high carbon dioxide absorption performance.

[Scheme 1]

CO ₂ + [Choline-N ⁺ ][Phenolate-O ^- ] → [Choline-N ⁺ ][Phenolate-O-CO ₂ ^- ]

[Scheme 2]

CO ₂ + [choline-N ⁺ ][phenolate-O ^- ] + R-OH → [choline-N ⁺ ][H-phenolate ⁺ -O-CO ₂ ^- ][RO-CO ₂ ] ^-

[In Scheme 2 above,

R is a C2-C10 aliphatic hydrocarbyl.]

In addition, the present disclosure provides a carbon dioxide separation method using the carbon dioxide absorbent according to an embodiment of the present disclosure, and the carbon dioxide separation method according to the present disclosure includes a first step of contacting the carbon dioxide absorbent with a mixture containing carbon dioxide; and a second step of heat-treating the carbon dioxide absorbent to desorb carbon dioxide attached to the absorbent.

The first step of the carbon dioxide separation method may be performed at 20 °C to 80 °C, specifically 25 °C to 65 °C, and more specifically 30 °C to 50 °C, but is not limited thereto.

In addition, the first step of the carbon dioxide separation method may be performed at 0.1 bar to 2.0 bar, specifically 0.3 bar to 1.7 bar, and more specifically 0.6 bar to 1.4 bar, but is not limited thereto.

The second step of the carbon dioxide separation method may be performed at 70 °C to 150 °C for 30 to 250 minutes, specifically at 80 °C to 130 °C for 40 to 200 minutes, more specifically at 90 °C to 110 °C. It may be performed for 60 to 180 minutes in, but is not limited thereto.

The second step of the carbon dioxide separation method may be performed under 100 cc/min to 300 cc/min N ₂ flow conditions, specifically 150 cc/min to 250 cc/min N ₂ flow conditions. , More specifically, 180 cc/min to 220 cc/min N ₂ It may be performed under flow conditions, but is not limited thereto.

The carbon dioxide separation method according to an embodiment of the present disclosure may be a method of continuously separating carbon dioxide by using the first step and the second step as unit processes and repeating the unit process two or more times.

In the second step of the carbon dioxide separation method according to an embodiment of the present disclosure, desorption is possible at a lower temperature and in a shorter time than amine-based absorbents (eg, MEA) used as conventional absorbents. That is, the carbon dioxide absorbent according to the present disclosure has very high carbon dioxide desorption efficiency by lowering heat capacity by using an alcohol solvent and significantly lowering regeneration energy compared to existing absorbents by simultaneously generating carbamate and carbonate.

The carbon dioxide separation method according to an embodiment of the present disclosure remarkably improves the adsorption and desorption of carbon dioxide by significantly improving the viscosity after absorption compared to before absorption of carbon dioxide. When carbamates or carbonates are produced using existing carbon dioxide absorbents, the viscosity of the reaction solution increases and the efficiency of the continuous carbon dioxide absorption reaction decreases, and high temperature conditions are required for a long time to desorb carbon dioxide after carbon dioxide absorption. . Since the carbon dioxide absorbent according to an embodiment of the present disclosure rather decreases in viscosity after capturing, it is much more effective in absorbing and desorbing carbon dioxide.

Hereinafter, a carbon dioxide absorbent including an ionic liquid including a choline-based cation and a phenolate-based anion and an aliphatic alcohol and a carbon dioxide separation method using the same according to the present disclosure will be described in more detail through specific examples.

[Preparation Example 1] Preparation of ionic liquid-1

After adding 10.00 g (46 wt%, 38.0 mmol) of choline hydroxide aqueous solution (TCI, C0326) and 4.15 g (38.0 mmol) of 2-aminophenol (Sigma-aldrich, A71301) to 100 mL RBF, the mixture was stirred at room temperature for 2 hours. did The reaction was vacuum dried at 60° C. for 15 hours to give 7.58 g (94%) of a dark brown oil.

1H NMR (500 MHz), D ₂ O, 25 ° C.: δ = 6.79 (m, 1H), 6.71 (m, 1H), 6.61 (m, 1H), 6.50 (m, 1H), 4.02 (m, 2H) , 3.46(m, 2H), 3.15(s, 9H)

[Preparation Example 2] Preparation of ionic liquid-2

After adding 10.00 g (46 wt%, 38.0 mmol) of choline hydroxide aqueous solution and 4.15 g (38.0 mmol) of 4-aminophenol (Sigma-aldrich, A71328) to 100 mL RBF, the mixture was stirred at room temperature for 2 hours. The reaction was vacuum dried at 60 °C for 15 hours to obtain 7.66 g (95%) of a dark brown solid.

1H NMR (500 MHz), d-DMSO, 25 ℃: δ = 6.20 (d, 2H), 6.00 (d, 2H), 3.79 (m, 2H), 3.32 (m, 2H), 3.51 (br, 2H) , 3.10(s, 9H)

[Preparation Example 3] Preparation of ionic liquid-3

After adding 10.00 g (46 wt%, 38.0 mmol) of choline hydroxide aqueous solution and 5.74 g (38.0 mmol) of 4-acetylaminophenol (Sigma-aldrich, A7085) to 100 mL RBF, the mixture was stirred at room temperature for 2 hours. The reaction was vacuum dried at 60° C. for 15 hours to give 9.18 g (95%) of a dark brown oil.

1H NMR (500 MHz), D2O, 25 ° C: δ = 7.04 (d, 2H), 6.58 (d, 2H), 4.03 (tr, 2H), 3.48 (tr, 2H), 3.17 (s, 9H), 2.10 (s, 3H)

[Comparative Preparation Example 1] Preparation of Ionic Liquid-4

5.00 g (18.0 mmol) of tetrabutylammonium chloride (Sigma-aldrich, 86870), 1.37 g (18.0 mmol) of sodium imidazolate (Sigma-aldrich, 197637), and 20 mL of ethanol were added to 100 mL RBF, followed by 2 hours at room temperature. Stir. After filtering the solid produced from the reaction, the filtrate was vacuum dried at 50 °C for 15 hours to obtain 5.46 g (98%) of a pale yellow oil.

1H NMR (500 MHz), d-DMSO, 25 ° C: δ = 7.06 (s, 1H), 6.65 (s, 2H), 3.18 (tr, 8H), 1.58 (m, 8H), 1.33 (m, 8H) , 0.94(m, 12H)

[Comparative Preparation Example 2] Preparation of ionic liquid-5

After adding 5.00 g (14.7 mmol) of tetrabutylphosphonium bromide (Sigma-aldrich, 189138), 1.12 g (14.7 mmol) of sodium imidazolate, and 20 mL of ethanol to 100 mL RBF, the mixture was stirred at room temperature for 2 hours. After filtering the solid produced from the reaction, the filtrate was vacuum dried at 50 °C for 15 hours to obtain 4.66 g (97%) of a pale yellow oil.

1H NMR (500 MHz), d-DMSO, 25 ° C: δ = 7.73 (s, 1H), 7.10 (s, 2H), 2.14 (m, 8H), 1.23 (m, 8H), 1.43 (m, 8H) , 0.91(m, 12H)

[Comparative Preparation Example 3] Preparation of Ionic Liquid-6

After adding 10.00 g (46 wt%, 38.0 mmol) of choline hydroxide aqueous solution and 2.85 g (38.0 mmol) of glycine (Sigma-aldrich, G7126) to 100 mL RBF, the mixture was stirred at room temperature for 2 hours. The reaction was vacuum dried at 60° C. for 15 hours to obtain 6.64 g (98%) of a clear oil.

1H NMR (500 MHz), d-DMSO, 25 ℃: δ = 3.85 (br, 2H), 3.41 (br, 2H), 3.12 (s, 9H), 2.68 (s, 2H), 1.23 (br, 2H)

[Comparative Preparation Example 4] Preparation of Ionic Liquid-7

5.00 g (28.6 mmol) of 1-butyl-3-methylimidazolium chloride (Sigma-aldrich, 94128), 3.33 g (28.6 mmol) of sodium phenoxide (Sigma-aldrich, 318191), and 20 mL of ethanol were added to 100 mL RBF. After adding, the mixture was stirred at room temperature for 2 hours. After filtering the solid produced in the reaction, the filtrate was vacuum dried at 50 °C for 15 hours to obtain 6.51 g (98%) of a dark brown oil.

1H NMR (500 MHz), d-DMSO, 25 ° C: δ = 9.35 (br, 1H), 7.77 (s, 1H), 7.70 (s, 1H), 6.73 (br, 2H), 6.14 (br, 2H) , 5.94(br, 1H), 4.15(m, 2H), 3.84(s, 3H), 1.75(m, 2H), 1.26(m, 2H), 0.88(m, 3H)

[Examples 1 to 5] Preparation of carbon dioxide absorbent

Carbon dioxide absorbents according to Examples 1 to 5 containing 30% by weight of the total ionic liquid according to the configuration shown in Table 1 below were prepared. When preparing the carbon dioxide absorbent, the ionic liquid and the solvent were added according to the weight ratio regardless of the order of addition, and mixed at 10 °C to 100 °C for 5 minutes to 60 minutes.

[Comparative Examples 1 to 4] Preparation of carbon dioxide absorbent

Carbon dioxide absorbents according to Comparative Examples 1 to 4 containing 30% by weight of the ionic liquid according to the configuration shown in Table 1 below were prepared.

[Comparative Example 5] Preparation of carbon dioxide absorbent

A carbon dioxide absorbent according to Comparative Example 5 containing only the ionic liquid of Preparation Example 1 was prepared.

ionic liquid menstruum Example 1 Preparation Example 1 monoethylene glycol Example 2 Preparation Example 1 2-Ethylhexanol Example 3 Preparation Example 2 monoethylene glycol Example 4 Preparation Example 2 2-Ethylhexanol Example 5 Preparation Example 3 2-Ethylhexanol Comparative Example 1 Comparative Preparation Example 1 2-Ethylhexanol Comparative Example 2 Comparative Preparation Example 2 2-Ethylhexanol Comparative Example 3 Comparative Preparation Example 3 2-Ethylhexanol Comparative Example 4 Comparative Preparation Example 4 2-Ethylhexanol Comparative Example 5 Preparation Example 1 -

[Experimental Example 1] Carbon dioxide absorption performance evaluation

In order to evaluate the carbon dioxide absorption performance of the carbon dioxide absorbents according to Examples 1 to 5 and Comparative Examples 1 to 5, vapor-liquid equilibrium ( Carbon dioxide absorption performance was measured using a Vapor Liquid Equiribrium (VLE) device. The vapor-liquid equilibrium device was a device including a carbon dioxide storage cylinder (150 mL), a constant temperature water bath, a stainless steel absorption reactor (73 mL) with a thermometer attached, an electronic pressure gauge, and an agitator. At this time, the cylinder and the reactor were maintained at a constant temperature of 40 ° C using a constant temperature water bath and a heating block, respectively, to measure the absorption capacity. The measurement error range of the reactor was ±0.1 °C ±0.01 bar.

Carbon dioxide absorption performance was specifically evaluated in the following manner. First, the carbon dioxide storage cylinder and the inside of the absorption reactor were sufficiently substituted with nitrogen, and then the carbon dioxide storage cylinder was filled with carbon dioxide and maintained at 1 bar and 40 °C. Then, the absorbent (6.0 g) solution according to Examples 1 to 5 and Comparative Examples 1 to 5 was introduced into the absorption reactor, maintained at 40 ° C, opened the valve connecting the cylinder and the reactor, and reached absorption equilibrium. The pressure was measured. The equilibrium pressure was measured every 30 minutes, and the above process was repeated until there was no pressure change between the cylinder and the reactor. Then, the number of moles of carbon dioxide absorbed according to the pressure change was calculated using the ideal gas equation. The carbon dioxide absorption equivalent calculated by Equation 1 using the number of moles of carbon dioxide absorbed, the viscosity of the absorbent before and after absorption, and whether solids were formed after absorption were analyzed and are shown in Table 2 below.

[Equation 1]

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

carbon dioxide
absorption equivalent
(CO ₂ -mol/mol) after absorption
Whether to create a solid Viscosity before absorption
(mPa S, 40℃) Viscosity after absorption
(mPa S, 40℃) Example 1 0.970 X 19.7 25.0 Example 2 0.984 X 15.2 7.3 Example 3 0.830 X 21.3 28.3 Example 4 0.775 X 7.4 17.4 Example 5 0.775 X 13.1 28.8 Comparative Example 1 0.884 O 17.6 analysis impossible Comparative Example 2 0.714 X 14.2 37.1 Comparative Example 3 0.421 O 11.1 analysis impossible Comparative Example 4 0.617 X 11.8 33.8 Comparative Example 5 analysis impossible analysis impossible 13,340 analysis impossible

As shown in Table 2, the carbon dioxide absorption performance of the examples all showed excellent absorption performance of 0.75 or more, and in particular, examples 1 and 2 showed very improved absorption performance of 0.95 or more.

On the other hand, Comparative Examples 2 to 4 exhibited lower absorption performance than Examples. In particular, in Comparative Examples 1 and 3, it can be seen that solids are formed after absorbing carbon dioxide, making repeated use impossible.

In Comparative Example 5, in which aliphatic alcohol was excluded, the initial viscosity was very high, so it was impossible to evaluate the carbon dioxide absorption performance.

The carbon dioxide absorbent containing an aliphatic alcohol according to the present disclosure has a low viscosity before absorption, and controls the viscosity to a level of 30 mPa·S or less after adsorption of carbon dioxide to compensate for the problem of increasing the viscosity after adsorption of the ionic liquid carbon dioxide absorbent. It is possible to use repeatedly because no formation occurs, and the carbon dioxide absorption capacity is also excellent. Therefore, the carbon dioxide absorbent according to the present disclosure is expected to be very useful industrially.

As described above, the present disclosure has been described with specific details, limited examples, and comparative examples, but these are only provided to help a more general understanding of the present disclosure, and the present disclosure is not limited to the above examples. Those skilled in the art can make various modifications and variations from these descriptions.

Therefore, the spirit of the present disclosure should not be limited to the described embodiments, and it will be said that not only the claims described below but also all modifications equivalent or equivalent to these claims belong to the scope of the present disclosure. .

Claims (14)

ionic liquids containing choline-based cations and phenolate-based anions; and
fatty alcohol;
A carbon dioxide absorbent comprising a. According to claim 1,
The carbon dioxide absorbent contains 5 to 70% by weight of an ionic liquid and 30 to 95% by weight of an aliphatic alcohol. According to claim 1,
The carbon dioxide absorbent wherein the phenolate anion is a compound represented by Formula 1 or 2 below.
[Formula 1]

[Formula 2]

[In Chemical Formulas 1 and 2,
R ₁ to R ₉ are each independently hydrogen, amino, carboxamido, C1-C10 alkyl, C1-C10 alkylcarbonyl, C1-C10 alkoxy or C3-C8 cycloalkyl;
Wherein amino, carboxamido, alkyl, alkylcarbonyl, alkoxy and cycloalkyl are halogen, cyano, amino, nitro, C1-C10 alkyl, C1-C10 alkylcarbonyl, C1-C10 alkoxy and C3-C8 cyclo It may be substituted with one or two or more substituents selected from alkyl.] According to claim 3,
R ₁ to R ₉ are each independently hydrogen, amino, carboxamido, C1-C5 alkyl, C1-C5 alkylcarbonyl or C1-C5 alkoxy;
Said amino, carboxamido, alkyl, alkylcarbonyl and alkoxy are selected from halogen, cyano, amino, nitro, C1-C10 alkyl, C1-C10 alkylcarbonyl, C1-C10 alkoxy and C3-C8 cycloalkyl A carbon dioxide absorbent which may be substituted with one or two or more substituents. According to claim 3,
wherein R ₁ to R ₉ are each independently hydrogen, amino or carboxamido, provided that at least one is amino or carboxamido;
Wherein the amino or carboxamido may be substituted with C1-C3 alkylcarbonyl. According to claim 1,
Wherein the aliphatic alcohol is an aliphatic monohydric alcohol or an aliphatic polyhydric alcohol. According to claim 1,
The aliphatic alcohol is a C2-C10 aliphatic alcohol, carbon dioxide absorbent. According to claim 1,
The aliphatic alcohol has a boiling point of 120 ℃ or more at 1 atm, carbon dioxide absorbent. According to claim 1,
The aliphatic alcohol has a heat capacity of 4.0 kJ / kg K or less, carbon dioxide absorbent. According to claim 1,
A carbon dioxide absorbent having a carbon dioxide absorption equivalent represented by the following formula 1 of 0.7 or more.
[Equation 1]
Carbon dioxide absorption equivalent = (number of moles of carbon dioxide absorbed) / (number of moles of absorbent) A first step of contacting the carbon dioxide absorbent of claim 1 with a mixture containing carbon dioxide; and
a second step of heat-treating the carbon dioxide absorbent to desorb carbon dioxide attached to the absorbent;
Including, carbon dioxide separation method. According to claim 11,
The first step is a carbon dioxide separation method that is performed at 20 ℃ to 80 ℃ conditions. According to claim 11,
The second step is carried out for 30 to 250 minutes at 70 ℃ to 150 ℃ conditions, carbon dioxide separation method. According to claim 11,
A carbon dioxide separation method in which the first step and the second step are unit processes, and the unit process is repeated two or more times to continuously separate carbon dioxide.