KR20100093960A - Pyrrolidinium- and piperidinium-based ioic liquids for carbon dioxide absorption - Google Patents

Abstract

PURPOSE: The vapor pressure of itself nearly has no and the thermal stability excels. The property of well absorbing the carbon dioxide has. The demount of the absorbed carbon dioxide can be proceed in the relatively low temperature. The initial uptake knuckle can be kept nearly even when reiterating the absorption, and degassing. CONSTITUTION: The ionic liquid carbon dioxide absorbent. With the cation selected from the chemical formula 1 and chemical formula 2 of one kind or 2 kind. It is included of the negative ion selected from the dialkyl phosphate of the alkyl phosphate of the chemical formula 3 and chemical formula 4 of one kind or 2 kind. In the chemical formula 1. R1 and R2 the alkyl group of the respective H or the carbon number 1 ~ 8.

Description

Pyrrolidinium- and piperidinium-based ioic liquids for carbon dioxide absorption

The present invention relates to a method of using pyrrolidinium and piperidinium-based room temperature ionic liquid as a CO ₂ absorbent. More specifically, an ionic liquid comprising a cation selected from pyrrolidinium or piperidinium having a heterocyclic structure of Formula 1 or Formula 2 and an anion selected from alkyl phosphate or dialkyl phosphate having structure of Formula 3 or Formula 4 To a CO ₂ absorbent.

Absorption, adsorption, separation membrane, deep cooling, etc. are used to separate CO ₂ from the exhaust gas and natural gas of chemical plants, power plants, and large boilers. In particular, when the concentration of CO ₂ emitted is low, absorption or adsorption methods are often used. Absorption or adsorption methods can be selectively separated only some gas that is absorbed or adsorbed to the absorbent or adsorbent is widely used industrially, but there is a disadvantage that the periodic replacement is necessary because the absorbent and the adsorbent is chemically modified during the separation process. Therefore, in the case of using a solid adsorbent, it is advantageous to apply only when the adsorbent replacement cycle is long because the chemical modification of the adsorbent is small. On the other hand, the absorbent method uses a liquid absorbent so that the absorbent can be easily replaced. Therefore, the absorbent is widely used for purifying a large amount of exhaust gas or separating gas. However, the absorbent is chemically modified.

As the carbon dioxide absorbent, amines such as MEA (monoethanolamine), MDEA (N-methyldiethanolamine), and DEA (diethanolamine) are most widely used.The amine absorber forms a chemical bond with CO ₂ and breaks when the bond is heated. This is because CO ₂ is stripped off and recovered and the absorbent can be regenerated. However, this process has some serious problems. In particular, problems of decomposition of amines by impurities such as SOx and NOx contained in absorbent gases and irreversible decomposition of amines due to high temperatures used to break chemical bonds between CO ₂ and the absorbent in the regeneration of the absorbent are problematic. In addition, the disadvantages of the degradation of the absorbent performance and the problem of replenishing the absorbent, corrosion of the absorber by the amine itself or decomposition products, contamination of the gas regenerated by the vapor pressure of the absorbent has been pointed out.

In order to compensate for the disadvantages of aqueous amine-based absorbents, methods for physically absorbing CO ₂ using organic solvents such as Selexol, IFPexol, and NFM have been reported, as shown in US Patent 4581052, 6342091 and US Patent Publication 2005/0129598. The most important advantage of the organic solvent absorbent is that CO ₂ absorption requires much lower energy for CO ₂ recovery and solvent regeneration because it is achieved only by the physical interaction between the solvent and carbon dioxide, not by the chemical bonds as in aqueous amines. Indeed, with amine absorbers, carbon dioxide recovery and absorbent regeneration require energy-intensive high temperature stripping processes, but in the case of physical absorption, CO ₂ dissolved in the solvent can be recovered simply by changing the pressure without increasing the temperature. Can be. However, the physical absorption process also has the following disadvantages.

First, the CO ₂ absorption capacity is low. Organic solvents generally exhibit much lower CO ₂ absorption capacity than aqueous amine solutions, so the circulation rate of the absorbent is high and therefore larger equipment is required. On the other hand, CO ₂ uptake by physical interactions tends to increase as the concentration of CO ₂ increases, which can be efficient for CO ₂ separation in gases with high CO ₂ concentrations.

Second, it has a high circulation rate. The physical absorption process by organic solvents usually requires twice as much absorbent circulation rate as in the case of amine solutions, which requires more capital and equipment costs.

Third, loss of solvent occurs. Solvents used for physical absorption do not have high boiling points and tend to be lost during treatment absorption and regeneration. This loss of solvent can be minimized through cooling or washing, but has the disadvantage of requiring additional equipment installation costs. Therefore, there is a need to develop new absorbents having high thermal and chemical stability and low vapor pressure that can overcome the disadvantages of amine absorbents and organic solvent absorbents.

In order to overcome the shortcomings of the recent absorbents, as described in US Patent No. 6,849,774, 6,623,659 and US Patent Publication No. 2008/0146849, an ionic liquid having no volatile and high thermal stability and maintaining a liquid phase at a temperature below 100 ° C. Attempts have been made to use ionic liquids as absorbents. Ionic liquids are polar salt compounds composed of organic cations and organic or inorganic anions. CO, CO ₂ , SO ₂ And gas molecules such as N ₂ O, which dissolve well. The solubility of the gas absorbed in the ionic liquid depends on the degree of interaction between the gas and the ionic liquid. Therefore, the polarity, acidity, basicity ( Basicity and nucleophilicity can be controlled to a certain degree of solubility in certain gases.

Typical ionic quaternary in liquid ammonium, already imidazolium, pyrazolium, triazolium, pyridinium, pyridinium Dodge titanium, pyrimidinyl titanium, organic cations containing nitrogen, and Cl ^-, Br ^-, I ^- halogens, such as, BF _{^{4 -, PF 6 -, (}} CF 3 SO) 2 N -, CF 3 SO 3 -, MeSO 3 -, NO 3 -, CF 3 CO 2 - and CH ₃ CO ₂ ^- Compounds composed of anions such as these have been known, and especially when anions contain fluorine atoms, they have been reported to have a relatively high carbon dioxide absorption capacity.

Borate (BF ₄ ^-) tetrafluoroborate, hexafluorophosphate (PF ₆ ^-), an ionic liquid having a sulfone imide (CF3SO2) 2N-) an anion containing a fluorine atom such as trifluoromethyl is carbon dioxide, and carbon disulfide, and Although it has the property of dissolving the same acidic gas well, in order to synthesize these ionic liquids, not only has to go through a complicated two-step manufacturing process, but also the production cost is too high, there are many problems to use industrially.

The present invention not only has high thermal and chemical stability and low viscosity, but also has a low temperature and easy synthesis, so that the room temperature is an ionic liquid, that is, a cation is pyrrolidinium or piperidinium and an anion. It is an object to provide an ionic liquid absorbent composed of this phosphate or phosphate.

An object of the present invention is to prepare an ionic liquid having a high absorption capacity for carbon dioxide, which can be prepared in a one-step reaction and simple in order to solve the problems of complexity and price of the manufacturing process, which is a disadvantage of the ionic liquid having a fluorine anion. To provide. The present inventors have found that an ionic liquid comprising a cation selected from pyrrolidinium or piperidinium having a heterocyclic structure of Formula 1 or Formula 2 and an anion selected from alkyl phosphate or dialkyl phosphate having structure of Formula 3 or Formula 4 In order to provide these ionic liquids as carbon dioxide absorbents by finding that they have excellent thermal and chemical stability, are not flammable, have a low viscosity while maintaining a liquid phase at room temperature, and have a high CO ₂ absorption capacity comparable to fluorine-based ionic liquids. do.

R ₁ in Chemical Formula ₁ And R ₂ each represent H or an alkyl group having 1 to 8 carbon atoms.

In Formula 2, R ₁ And R ₂ each represent H or an alkyl group having 1 to 8 carbon atoms.

R ₁ in the phosphate anion of Formula 3 represents an alkyl group having 1 to 4 carbon atoms.

R ₁ in the phosphate anion of Formula 4 And R ₂ each represent an alkyl group having 1 to 4 carbon atoms.

According to the present invention, the room temperature ionic liquid consisting of pyrrolidinium or piperidinium cation and an alkyl phosphate or dialkyl phosphate anion has almost no vapor pressure of its own, excellent thermal stability, and absorbs carbon dioxide as well as absorption. Removal of the carbon dioxide can also be carried out at a relatively low temperature, and can be used as an effective carbon dioxide separation medium because the initial absorption capacity can be maintained almost even after repeated absorption and degassing.

The present invention is one selected from dialkylpyrrolidinium of the general formula (1) and dialkylpiperidinium of the general formula (2) with one or two cations and an alkyl phosphate of the formula (3) and a dialkyl phosphate of the formula (4) Or it relates to a carbon dioxide absorbent which is an ionic liquid consisting of two kinds of anions.

[Formula 1]

R ₁ in Chemical Formula ₁ And R ₂ are each H or an alkyl group having 1 to 8 carbon atoms,

[Formula 2]

R ₁ in Chemical Formula 2 And R ₂ are each H or an alkyl group having 1 to 8 carbon atoms,

(3)

In Formula 3, R ₁ is an alkyl group having 1 to 4 carbon atoms,

[Formula 4]

R ₁ in Chemical Formula 4 And R ₂ each represent an alkyl group having 1 to 4 carbon atoms.

Preferably the ionic liquid is methylpyrrolidinium methyl phosphate ([MPyrr] [MHPO ₃ ]), ethyl methyl pyrrolidinium ethyl phosphate ([EMPyrr] [EHPO ₃ ]), butyl ethyl pyrrolidinium ethyl Phosphate ([BEPyrr] [EHPO ₃ ]), dibutylpyrrolidinium butylphosphate ([DBPyrr] [BHPO ₃ ]), hexylpyrrolidinium hexylphosphate ([HxPyrr] [HxHPO ₃ ]), octylpyrrolidinium octylphosphate ([OcPyrr] [OcHPO ₃ ]), ethylpiperidinium ethylphosphate ([EPiper] [EHPO ₃ ]), butylmethylpiperidinium butylphosphate ([BMPiper] [BHPO ₃ ]), hexylmethylpiperidinium methyl phosphate (I H x MPiper] [MHPO ₃ ]) and butyl methylpyrrolidinium butyl phosphate ([BMPyrr] [BHPO ₃ ]) is one or more ionic liquids selected from the group will be.

In addition, the present invention is selected from dialkylpyrrolidinium of the general formula (1) and dialkylpiperidinium of the general formula (2) and one or two cations selected from alkyl phosphate of the formula (3) and dialkyl phosphate of the formula (4) A method of absorbing carbon dioxide under conditions in the range of 0 to 80 ° C. and atmospheric pressure to 60 atm using an ionic liquid composed of one or two kinds of anions.

[Formula 1]

R ₁ in Chemical Formula ₁ And R ₂ are each H or an alkyl group having 1 to 8 carbon atoms,

[Formula 2]

R ₁ in Chemical Formula 2 And R ₂ are each H or an alkyl group having 1 to 8 carbon atoms,

(3)

In Formula 3, R ₁ is an alkyl group having 1 to 4 carbon atoms,

[Formula 4]

R ₁ in Chemical Formula 4 And R ₂ each represent an alkyl group having 1 to 4 carbon atoms.

Preferably the ionic liquid is methylpyrrolidinium methyl phosphate ([MPyrr] [MHPO ₃ ]), ethyl methyl pyrrolidinium ethyl phosphate ([EMPyrr] [EHPO ₃ ]), butyl ethyl pyrrolidinium ethyl Phosphate ([BEPyrr] [EHPO ₃ ]), dibutylpyrrolidinium butylphosphate ([DBPyrr] [BHPO ₃ ]), hexylpyrrolidinium hexylphosphate ([HxPyrr] [HxHPO ₃ ]), octylpyrrolidinium octylphosphate ([OcPyrr] [OcHPO ₃ ]), ethylpiperidinium ethylphosphate ([EPiper] [EHPO ₃ ]), butylmethylpiperidinium butylphosphate ([BMPiper] [BHPO ₃ ]), hexylmethylpiperidinium methyl phosphate ([HxMPiper] [MHPO ₃ ]) and butylmethylpyrrolidinium butyl phosphate ([BMPyrr] [BHPO ₃ ]), or a method for absorbing carbon dioxide, characterized in that it is an ionic liquid of two or more kinds. .

Amine-based absorbents such as monoethanolamine, diethanolamine, and triethanolamine, which are currently widely used industrially, have weak alkalinity and thus exhibit excellent performance in absorbing carbon dioxide. However, these amine-based absorbents have high vapor pressures, which are accompanied by the loss of absorbents when they are degassed, and the problem that the recovered CO ₂ is contaminated with the absorbents. It was prone to some destruction. Heterocyclic cation containing nitrogen and ^{_{AlCl 4 -, BF 4 -,}} PF 6 -, (CF 3 SO) 2 N -, CF 3 SO 3 -, MeSO 3 -, NO 3 -, CF 3 CO 2 -, CH ₃ CO ₂ ^- Among the salts combined with various anions, such as ionic liquids that maintain a liquid state even near room temperature, is known as a gas absorbent, various ionic liquids have been proposed as carbon dioxide and sulfur dioxide gas absorbers. However, these ionic liquids are vulnerable to moisture, and thus have a problem in that gas absorption ability gradually decreases due to a tendency to be decomposed by the water contained in the mixed gas, or the ionic liquid is expensive and difficult to use for general purposes. In order to overcome this problem, the present invention proposes an ionic liquid which is inexpensive, durable, and has good carbon dioxide absorption.

The ionic liquid used in the present invention uses dialkylpyrroridium (dialkylpyrroridium) having a structure of formula (1) or dialkyl piperidinium (dialkylpiperidinium) having a structure of formula (2) as a cation, and as an anion It consists of a combination of these cations and anions using alkyl phosphite or dialkylphosphate based anions such as formula (4).

[Formula 1]

R ₁ in Chemical Formula ₁ And R ₂ each represent H or an alkyl group having 1 to 8 carbon atoms.

[Formula 2]

In Formula 2, R ¹ And R ² each represent H or an alkyl group having 1 to 8 carbon atoms.

(3)

R ¹ in the phosphate anion of Formula 3 represents an alkyl group having 1 to 4 carbon atoms.

[Formula 4]

R ¹ in the phosphate anion of Formula 4 And R ² each represent an alkyl group having 1 to 4 carbon atoms.

In Formula 1-2, R ¹ and R ² are each H or an alkyl group having 1 to 8 carbon atoms, that is, methyl (CH ₃ ), ethyl (C ₂ H ₅ ), n-butyl (nC ₄ H ₉ ), and n-hexyl (nC ₆ H ₁₁₎ or n- octyl (nC ₈ H ₁₇₎ in configuration and in formula 3 R ¹ R ¹ is an alkyl group in the formula (IV) of 1 to 4 carbon atoms And R ² each represent an alkyl group having 1 to 4 carbon atoms.

In the context of the present invention CO ₂ The use process of the ionic liquid used to absorb is shown in FIG. CO ₂ Absorption test apparatus is a stainless steel absorption reactor 100, a high pressure (0 ~ 1000) is attached to the thermometer 120 psi Pressure transducer for pressure  transducer 200, thermometer 310 attached CO ₂  It consists of a storage cylinder 300 and the stirrer 110, at a constant temperature CO ₂  To measure the absorption ability Thermostat  Installed in.

CO ₂ Absorption performance experiment was conducted in the following manner. After weighing the prepared ionic liquid, it was put in the absorption reactor 100 of Figure 1 together with the magnetic rod at 40 ~ 80 ℃ With stirring Vacuum dry . After closing the valve 102 connected to the absorption reactor 100, CO ₂  Constant pressure (50 ~ 60) in the storage cylinder (300) psig )of CO ₂ And equilibrate and record the pressure and temperature ( Initial value ). Similarly, after opening valve 102, record the pressure and temperature at equilibrium, Stirring  Start and record the final pressure and temperature ( equilibrium value). After closing the valve 102, while gradually increasing the pressure (60 to 500 psig ) Initial and Equilibrium value  Obtain 4 to 10 measurements. Strip  In the case of an experiment CO ₂  After the absorption experiment, open the valve 101, lower the pressure, and raise the temperature to 50 ~ 100 ℃ Degassing .

The process shown in FIG. 1 is similar to that commonly used in physical absorption processes. The removal of carbon dioxide absorbed by ionic liquids requires much lower energy than the high temperature stripping process required to recover CO ₂ in processes using amine absorbers, which is more expensive than in amine solutions that chemically bond with CO _2. in the ionic liquid which is absorbed by the _second physical interaction it is because it is much easier to remove the CO _2. Ionic liquids are also more efficient than organic solvent absorbers because ionic liquids have a higher CO ₂ absorption capacity than organic solvent absorbents, thereby reducing the circulation circulation of the absorbents and thus reducing the size of the device. In addition, since ionic liquids have a very low absorption rate of hydrocarbons compared to organic solvent absorbents, the loss of hydrocarbons can be minimized because only CO ₂ is selectively absorbed when the hydrocarbons containing CO ₂ impurities are used for purification.

An additional advantage of the processes and methods used in the present invention is the very low loss of ionic liquid absorbent. Since the ionic liquid absorbent used in the present invention has a very low vapor pressure, there is little possibility of loss of the ionic liquid absorbent, and since it is chemically stable, there is also little loss of the ionic liquid through the decomposition process.

When the carbon dioxide is absorbed using the ionic liquid of the present invention, the temperature is in the range of 0 ° C to 80 ° C, preferably in the range of 20 ° C to 50 ° C, and the pressure is absorbed at normal pressure to 60 atm, and then at room temperature to In the range of 100 ° C., preferably in the range of 40 to 80 ° C., the pressure is degassed to normal pressure. When absorbing carbon dioxide, the lower the temperature and the higher the pressure, the higher the amount of carbon dioxide absorbed. In particular, as the absorption pressure increases, the amount of carbon dioxide absorbed increases almost linearly. The ionic liquids presented in the present invention exhibit excellent absorption of carbon dioxide and maintain their absorption to the same extent as the first time even in repeated use.

For example, using butylmethylpyrrolidinium butylphosphate ([BMPyrr] [BHPO ₃ ]), when absorbing carbon dioxide at 15 atmospheres and 40 ° C., it reaches 95% of its apparent equilibrium value within 40 minutes. This value corresponds to 0.26 moles of CO ₂ absorption per mole, which corresponds to 52% of 0.5 moles of CO ₂ per mole of amine, the maximum theoretical absorption of amine-based absorbents, and butylmethylimide, one of the best ionic liquids. imidazolium tetrafluoro borate as a numerical value exceeding the CO ₂ absorption capacity of _{0.23 mol CO 2 / mol [BIMIm} ] BF 4 in ([BIMIm] BF _4). Here, the apparent equilibrium value refers to the absorption value when the absorption amount no longer changes by measuring the absorption amount of carbon dioxide with time. When the absorption amount of carbon dioxide reaches the apparent equilibrium value, the pressure is lowered to atmospheric pressure and degassed at 70 ° C. After the absorption of carbon dioxide reached the apparent equilibrium value, the pressure was lowered to normal pressure and the temperature was raised to 70 ° C. to degas CO ₂ , and when CO ₂ absorption experiments were conducted under the same conditions, the amount of CO ₂ absorption per mole of ionic liquid after 30 minutes was It was 0.256 moles, and even after 10 times of absorption / degassing under the same conditions, the final absorption capacity was almost the same as the initial absorption capacity. In addition, when absorbed at 30 ℃ by increasing the carbon dioxide pressure to 20 ℃ to reach 94% of the apparent equilibrium value within 25 minutes, if absorbed by the apparent equilibrium value, the pressure is reduced to atmospheric pressure to degassing at 70 ℃, the same process is repeated 10 times In this case, the final absorption capacity is reduced by about 1% compared to the initial carbon dioxide absorption capacity. In contrast, in the case of using conventional amine compounds used as carbon dioxide absorbents, for example, diethanol amine as an absorbent, carbon dioxide is absorbed at 1 atm and 30 ° C. and degassed at atmospheric pressure and 110 ° C. under the same conditions. At twice absorption and degassing, the final absorption capacity is reduced by 15% compared to the initial absorption capacity. Therefore, by using the phosphorus-based ionic liquid proposed in the present invention it can be repeatedly absorbed, degassed, separated for a long time compared to the existing amine-based absorbent can greatly save energy.

The present invention as described above will be described in more detail based on the following examples, but the present invention is not limited to these examples.

Example  One. CO ₂  Absorption experiment

The absorption reactor 100 of FIG. 1 was charged with 10 g of butyl methylpyrrolidinium butyl phosphate ([BMPyrr] [BHPO ₃ ]) and the CO ₂ absorption experiment was carried out while maintaining the temperature of the thermostat at 40 ° C. It was done. After filling the CO ₂ cylinder 300 with a certain pressure, the connection valve 102 is opened to expand the gas into the absorption reactor 100 so that the initial pressure of the absorption reactor 100 and the whole system is 1 atm, and then absorption. Until the equilibrium was reached, the degree of decrease in the pressure of the CO ₂ cylinder 300 was tracked, and the amount of CO ₂ dissolved in the ionic liquid was measured using a gaseous equation.

In the same way, the CO ₂ initial pressure of the absorption reactor 100 was increased to 5, 10, 15, 30, 50 atm, respectively, and the pressure of the total system was increased to measure the amount of carbon dioxide absorption according to the pressure. As illustrated in FIG. 2, the carbon dioxide uptake of [BMPyrr] [BHPO ₃ ] also increased in proportion to the increase in carbon dioxide pressure.

Example  2-12. According to the type of ionic liquid CO ₂  Absorption experiment

Table 1 shows the results of CO ₂ absorption experiments with different kinds of phosphate-based ionic liquids in the same manner as in Example 1.

Example Ionic Liquid (IL) Absorption temperature
(℃) CO ₂ pressure
(atmospheric pressure) CO ₂ absorption
(gmole / IL gmole) 2 [MPyrr] [MHPO ₃ ] 40 10 0.125 3 [EMPyrr] [EHPO ₃ ] 40 30 0.374 4 [BEPyrr] [EHPO ₃ ] 30 Atmospheric pressure 0.030 5 [DBPyrr] [BHPO ₃ ] 40 20 0.293 6 [HxPyrr] [HxHPO ₃ ] 40 10 0.221 7 [OcPyrr] [OcHPO ₃ ] 40 10 0.240 8 [EPiper] [EHPO ₃ ] 40 60 0.826 9 [BMPiper] [BHPO ₃ ] 40 40 0.483 10 [HxMPiper] [MHPO ₃ ] 40 10 0.207 11 [MPyrr] [MHPO ₃ ] 20 20 0.221 12 [MPyrr] [MHPO ₃ ] 50 20 0.198 13 [BMPyrr] [BHPO ₃ ] 30 20 0.223

The above ionic liquid is as follows. Methylpyrrolidinium methylphosphate ([MPyrr] [MHPO ₃ ]), ethylmethylpyrrolidinium ethylphosphate ([EMPyrr] [EHPO ₃ ]), butylethylpyrrolidinium ethylphosphate ([BEPyrr] [EHPO ₃ ]), Dibutylpyrrolidinium butylphosphate ([DBPyrr] [BHPO ₃ ]), hexylpyrrolidinium hexylphosphate ([HxPyrr] [HxHPO ₃ ]), octylpyrrolidinium octylphosphate ([OcPyrr] [OcHPO ₃ ]), ethyl Piperidinium ethylphosphate ([EPiper] [EHPO ₃ ]), butylmethylpiperidinium butylphosphate ([BMPiper] [BHPO ₃ ]), hexylmethylpiperidinium methyl phosphate ([HxMPiper] [MHPO ₃ ]), butyl Methylpyrrolidinium butylphosphate ([BMPyrr] [BHPO ₃ ]).

Comparative example  One. [ BIMIm ] BF ₄ Using CO ₂  Absorption experiment

Example 1, in a similar way [BIMIm] carbon dioxide when sikyeoteul absorb carbon dioxide at 15 atm, 40 ℃ using BF ₄ as absorbent [BIMIm] has been absorbed by _{0.23 CO 2 / mol [BIMIm]} BF 4 for BF ₄ .

Example  14-22. Repeated according to the type of ionic liquid CO ₂  Absorption experiment

In the same manner as in Example 1, the ionic liquids used in Examples 1 and 2 were absorbed with carbon dioxide at 10 or 20 atm and 30 ° C., and the apparent equilibrium value was measured. When the first absorption and degassing of the first carbon dioxide is finished, the absorption and degassing are repeated 10 times, and the results are shown in Table 2 by comparing the initial carbon dioxide absorption capacity with the 10th absorption capacity.

Example Ionic Liquid (IL) Absorption pressure
(atmospheric pressure) CO ₂ absorption
(gmole / gmole IL) 1 time absorption 10 times absorption 14 [MPyrr] [MHPO ₃ ] 10 0.125 0.121 15 [EMPyrr] [EHPO ₃ ] 20 0.224 0.223 16 [BEPyrr] [EHPO ₃ ] 10 0.167 0.154 17 [DBPyrr] [BHPO ₃ ] 20 0.293 0.280 18 [HxPyrr] [HxHPO ₃ ] 10 0.221 0.214 19 [OcPyrr] [OcHPO ₃ ] 20 0.412 0.400 20 [EPiper] [EHPO ₃ ] 10 0.160 0.159 21 [BMPiper] [BHPO ₃ ] 10 0.151 0.148 22 [HxMPiper] [MHPO ₃ ] 10 0.208 0.196

Example  23-31. According to the type of ionic liquid CO ₂  Absorption experiment

Table 3 shows the results of CO ₂ absorption experiments with different kinds of phosphate-based ionic liquids in the same manner as in Example 1.

Example Ionic Liquid (IL) Absorption temperature
(℃) CO ₂ pressure
(atmospheric pressure) CO ₂ absorption
(gmole / gmole IL) 23 [MPyrr] [MHPO ₄ ] 40 10 0.117 24 [EMPyrr] [EHPO ₄ ] 40 40 0.469 25 [BEPyrr] [EHPO ₄ ] 30 Atmospheric pressure 0.028 26 [DBPyrr] [BHPO ₄ ] 40 20 0.281 27 [HxPyrr] [HxHPO ₄ ] 40 10 0.210 28 [OcPyrr] [OcHPO ₄ ] 40 Atmospheric pressure 0.050 29 [EPiper] [EHPO ₄ ] 40 60 0.802 30 [BMPiper] [BHPO ₄ ] 40 30 0.365 31 [HxMPiper] [MHPO ₄ ] 40 10 0.194

The above ionic liquid is as follows. Methylpyrrolidinium methylphosphate ([MPyrr] [MHPO ₄ ]), ethylmethylpyrrolidinium ethylphosphate ([EMPyrr] [EHPO ₄ ]), butylethylpyrrolidinium ethylphosphate ([BEPyrr] [EHPO ₄ ]), Dibutylpyrrolidinium butylphosphate ([DBPyrr] [BHPO ₄ ]), hexylpyrrolidinium hexylphosphate ([HxPyrr] [HxHPO ₄ ]), octylpyrrolidinium octylphosphate ([OcPyrr] [OcHPO ₄ ]), ethyl Piperidinium ethylphosphate ([EPiper] [EHPO ₄ ]), butylmethylpiperidinium butylphosphate ([BMPiper] [BHPO ₄ ]), hexylmethylpiperidinium methyl phosphate ([HxMPiper] [MHPO ₄ ]).

Example  32-40. Repeated according to the type of ionic liquid CO ₂  Absorption experiment

In the same manner as in Example 1, the ionic liquid used in Example 4 was absorbed with carbon dioxide at 10 atm or 20 atm and 30 ° C to measure the apparent equilibrium value, and then the pressure was lowered to atmospheric pressure to degas at 70 ° C. When the first absorption and degassing of the first carbon dioxide is finished, the absorption and degassing were repeated 10 times, and the initial carbon dioxide absorption capacity was compared with the absorption capacity of the 10th time.

Example Ionic liquid Absorption pressure
(atmospheric pressure) CO ₂ absorption
(gmole / gmole IL) 1 time absorption 10 times absorption 32 [MPyrr] [MHPO ₄ ] 10 0.117 0.116 33 [EMPyrr] [EHPO ₄ ] 20 0.219 0.214 34 [BEPyrr] [EHPO ₄ ] 20 0.255 0.248 35 [DBPyrr] [BHPO ₄ ] 10 0.177 0.170 36 [HxPyrr] [HxHPO ₄ ] 10 0.210 0.197 37 [OcPyrr] [OcHPO ₄ ] 20 0.395 0.381 38 [EPiper] [EHPO ₄ ] 10 0.149 0.141 39 [BMPiper] [BHPO ₄ ] 20 0.223 0.215 40 [HxMPiper] [MHPO ₄ ] 10 0.194 0.182

Comparative example  2. Diethanolamine  Repeat used CO ₂  Absorption experiment

In a similar manner to Example 3, the experiment of absorbing carbon dioxide at 1 atm and 30 ° C. and degassing at 110 ° C. using diethanol amine as an absorbent was repeated twice. In the first absorption, carbon dioxide was absorbed by 0.1769 gmole / gmole in the solvent, but the second absorption by 0.1440 gmol / gmole reduced the solvent's absorption capacity by about 19%.

Therefore, it can be seen that the absorption capacity of the solvent is relatively reduced compared to the case of the above embodiment.

1 is a schematic diagram of a carbon dioxide absorption and degassing apparatus.

2 is a carbon dioxide absorption amount (40 ° C.) of [BMPyrr] [BHPO ₃ ] according to pressure.

<Description of the symbols for the main parts of the drawings>

100 carbon dioxide absorption reactor 101 valve

102 valve 110 agitator

120: thermometer 200: high pressure pressure transducer

300: carbon dioxide storage cylinder 301: valve

310: thermometer 400: pressure gauge

500: carbon dioxide supply container 501: valve

502: Valve

Claims (4)

One or two kinds of cations selected from dialkylpyrrolidinium of formula (1) and dialkylpiperidinium of formula (2) and one or two species selected from alkylphosphates of formula (3) and dialkylphosphates of formula (4) Carbon dioxide absorbent, an ionic liquid consisting of anions of: [Formula 1]

R ₁ in Chemical Formula ₁ And R ₂ are each H or an alkyl group having 1 to 8 carbon atoms, [Formula 2]

R ₁ in Chemical Formula 2 And R ₂ are each H or an alkyl group having 1 to 8 carbon atoms, (3)

In Formula 3, R ₁ is an alkyl group having 1 to 4 carbon atoms, [Formula 4]

R ₁ in Chemical Formula 4 And R ₂ each represent an alkyl group having 1 to 4 carbon atoms. The method of claim 1, The ionic liquid is methylpyrrolidinium methyl phosphate ([MPyrr] [MHPO ₃ ]), ethyl methyl pyrrolidinium ethyl phosphate ([EMPyrr] [EHPO ₃ ]), butyl ethyl pyrrolidinium ethyl phosphate ([BEPyrr ] [EHPO ₃ ]), dibutylpyrrolidinium butylphosphate ([DBPyrr] [BHPO ₃ ]), hexylpyrrolidinium hexylphosphate ([HxPyrr] [HxHPO ₃ ]), octylpyrrolidinium octylphosphate ([OcPyrr] [OcHPO ₃ ]), ethylpiperidinium ethylphosphate ([EPiper] [EHPO ₃ ]), butylmethylpiperidinium butylphosphate ([BMPiper] [BHPO ₃ ]), hexylmethylpiperidinium methylphosphate ([HxMPiper] A carbon dioxide absorbent, which is an ionic liquid, characterized in that it is one or two or more ionic liquids selected from [MHPO ₃ ]) and butylmethylpyrrolidinium butylphosphate ([BMPyrr] [BHPO ₃ ]). One or two kinds of cations selected from dialkylpyrrolidinium of formula (1) and dialkylpiperidinium of formula (2) and one or two species selected from alkylphosphates of formula (3) and dialkylphosphates of formula (4) Method of absorbing carbon dioxide under conditions in the range of 0 to 80 ° C. and atmospheric pressure to 60 atm using an ionic liquid composed of anions of: [Formula 1]

R ₁ in Chemical Formula ₁ And R ₂ are each H or an alkyl group having 1 to 8 carbon atoms, [Formula 2]

R ₁ in Chemical Formula 2 And R ₂ are each H or an alkyl group having 1 to 8 carbon atoms, (3)

In Formula 3, R ₁ is an alkyl group having 1 to 4 carbon atoms, [Formula 4]

R ₁ in Chemical Formula 4 And R ₂ each represent an alkyl group having 1 to 4 carbon atoms. The method of claim 3, wherein The ionic liquid is methylpyrrolidinium methyl phosphate ([MPyrr] [MHPO ₃ ]), ethyl methyl pyrrolidinium ethyl phosphate ([EMPyrr] [EHPO ₃ ]), butyl ethyl pyrrolidinium ethyl phosphate ([BEPyrr] [ EHPO ₃ ]), dibutylpyrrolidinium butylphosphate ([DBPyrr] [BHPO ₃ ]), hexylpyrrolidinium hexylphosphate ([HxPyrr] [HxHPO ₃ ]), octylpyrrolidinium octylphosphate ([OcPyrr] [OcHPO ₃ ]), ethylpiperidinium ethylphosphate ([EPiper] [EHPO ₃ ]), butylmethylpiperidinium butylphosphate ([BMPiper] [BHPO ₃ ]), hexylmethylpiperidinium methylphosphate ([HxMPiper] [MHPO ₃ ]) and butylmethylpyrrolidinium butylphosphate ([BMPyrr] [BHPO ₃ ]) is a method of absorbing carbon dioxide, characterized in that one or more ionic liquids selected from.

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