Carbon dioxide absorbent containing an ionic substance containing cyclic ammonium cations and hydroxide anions, and method for separating carbon dioxide using the same.

Abstract

This invention provides a carbon dioxide absorbent containing an ionic substance and a method for separating carbon dioxide using the same. [Solution] A carbon dioxide absorbent is provided that contains an ionic substance containing a cyclic ammonium cation and a hydroxide anion. The carbon dioxide absorbent according to one embodiment contains a hydroxide anion with a small molecular weight and high basicity, which effectively improves the absorption performance per unit volume of the absorbent. Furthermore, since the carbon dioxide absorbent according to one embodiment is soluble in water, it does not cause the problem of layer separation.

Description

[Technical Field]

[0001] This disclosure relates to a carbon dioxide absorbent containing an ionic substance containing a cyclic ammonium cation and a hydroxide anion, and a method for separating carbon dioxide using the same. [Background technology]

[0002] As global economic development and industrialization progress rapidly, energy use is increasing, and so is the use of fossil fuels, the main source of energy. Global warming, which is closely related to energy use, is a matter of global concern. Carbon dioxide (CO2), which accounts for the largest proportion of the major greenhouse gases, is almost entirely produced in the process of burning fossil fuels to convert them into energy.

[0003] Because the carbon dioxide generated in this way is controllable, technologies for removing carbon dioxide are attracting considerable attention. Methods applied to combustion exhaust gas during the carbon dioxide capture process can be broadly categorized into absorption, adsorption, and membrane separation methods, depending on their separation characteristics. Among these, absorption is the most actively used method, and absorption is further divided into physical absorption and chemical absorption. In chemical absorption, aqueous solutions of amines such as monoethanolamine (MEA), N-methyldiethanolamine (MDEA), and diethanolamine (DEA) are the most widely used, and much research is also being conducted on the synthesis of ionic substances combining cations and anions and their use as absorbents. [Overview of the project] [Problems that the invention aims to solve]

[0004] One embodiment aims to provide a carbon dioxide absorbent containing an ionic substance. Another embodiment aims to provide a method for separating carbon dioxide using a carbon dioxide absorbent containing an ionic substance. [Means for solving the problem]

[0005] One embodiment provides a carbon dioxide absorbent comprising an ionic substance containing a cyclic ammonium cation represented by the following chemical formula 1 and a hydroxide anion.

[0006]

Chemical formula

[0007] In the above chemical formula 1, R 5-20 ~R 4 are each independently -H, C 1-20 alkyl group, C 1-20 alkoxy group, C 1-10 alkoxy C 1-10 alkyl group, C 5-20 cycloalkyl group, or a 5- to 20-member heterocycloalkyl group, and R 5 and R 6 are each independently -H, C 1-20 alkyl group, C 1-10 alkoxy C 1-10 alkyl group, C 5-20 cycloalkyl group, or a 5- to 20-member heterocycloalkyl group, L 1 is a single bond, -O-, -NR 7 -, or C 1-8 alkylene group, and the above R 7 is -H, or C 1-10 alkyl group, or the above R 7 is the above R 5 may combine with the above R 1 ~R 7 The C 1-20 alkyl group, C 1-20 alkoxy group, C 1-10 alkoxy C 1-10 alkyl group, C 5-20 cycloalkyl group, and the 5- to 20-member heterocycloalkyl group may each independently be substituted with a halogen group, -OH, -NH2, or -NO2.

[0008] In one embodiment, in the chemical formula 1, the R 1 ~R 4 These are, independently, -H and C 1-10 Alkyl alkyl group, C 1-10 Alkoxy group, C 1-5 Alkoxy C 1-5 Alkyl alkyl group, C 5-10 A cycloalkyl group, or a 5- to 10-membered heterocycloalkyl group, and the R 5 and R 6 These are, independently, -H and C 1-10 Alkyl alkyl group, C 1-5 Alkoxy C 1-5 Alkyl alkyl group, C 5-10 A cycloalkyl group, or a 5- to 10-membered heterocycloalkyl group, and the L 1 These are single bonds, -O-, -NR 7 -, or C 1-5 It is an alkylene group, and the R 7 is -H, or C 1-5 is an alkyl group, or the R 7 is the aforementioned R 5 It may bond with R to form a ring, and the R 1 ~R 7 C 1-10 Alkyl alkyl group, C 1-10 Alkoxy group, C 1-5 Alkoxy C 1-5 Alkyl alkyl group, C 5-10 The cycloalkyl groups and the 5- to 10-membered heterocycloalkyl groups may each be independently substituted with a halogen group, -OH, -NH2, or -NO2.

[0009] In one embodiment, the cyclic ammonium cation may be represented by the following chemical formula 2.

[0010] [ka]

[0011] In the aforementioned chemical formula 2, R 5 and R 6 These are, independently, -H and C1-20 an alkyl group, C 1-10 an alkoxy C 1-10 an alkyl group, C 5-20 a cycloalkyl group, or a 5- to 20-membered heterocycloalkyl group, and L 1 is a single bond, -O-, -NR 7 -, or C 1-8 an alkylene group, and the R 7 is -H, or C 1-10 an alkyl group, or the R 7 is the R 5 may combine with the R 5 to form a ring, and the R 7 to R 1-10 The C of the alkyl group, C 1-20 alkyl group, C 1-10 alkoxy C 1-10 alkyl group, C 5-20 cycloalkyl group, and 5- to 20-membered heterocycloalkyl group may each independently be substituted with a halogen group, -OH, -NH2, or -NO2.

[0012] In one embodiment, in Chemical Formula 2, the R 5 and R 6 are each independently a C 1-10 alkyl group, C 1-5 alkoxy C 1-5 alkyl group, C 5-10 cycloalkyl group, or a 5- to 10-membered heterocycloalkyl group, and the L 1 is a single bond, -O-, -NR 7 -, or C 1-8 alkylene group, and the R 7 is -H, or C 1-5 alkyl group, and the R 5 to R 7 The C of the alkyl group, C 1-10 alkyl group, C 1-5 alkoxy C 1-5 alkyl group, C 5-10 cycloalkyl group, and 5- to 10-membered heterocycloalkyl group may each independently be substituted with -OH, -NH2, or -NO2.

[0013] In one embodiment, in Chemical Formula 2, the R 5 and R 6 are each independently a C 1-5 alkyl group or a C 1-3 alkoxy C 1-3 alkyl group, the L 1 is -O- or a methylene group, and the C 5 alkyl group of R 6 and R 1-5 and the C 1-3 alkoxy C 1-3 alkyl group may each independently be substituted with -OH.

[0014] In one embodiment, the cyclic ammonium cation may be any one selected from the group of compounds consisting of

Chemical formula

[0015] In one embodiment, the carbon dioxide absorbent may further contain water. In one embodiment, the carbon dioxide absorbent may further contain one or more solvents in addition to the water.

[0016] In one embodiment, the solvent may contain an amine compound. In one embodiment, the amine compound may contain any one or more selected from the group consisting of monoethanolamine (MEA), N-methyldiethanolamine (MDEA), diethanolamine (DEA), triethanolamine (TEA), 2-amino-2-methyl-1-propanol (AMP), and piperazine (PZ).

[0017] In one embodiment, the ionic substance may be contained at 5% to 50% by weight based on the total weight of the carbon dioxide absorbent. In one embodiment, the water may be contained at 30% to 90% by weight based on the total weight of the carbon dioxide absorbent. In one embodiment, the amine compound may be present in an amount of 10% to 50% by weight relative to the total weight of the carbon dioxide absorbent.

[0018] Another embodiment provides a method for separating carbon dioxide, which includes the step of contacting the carbon dioxide absorbent according to the above embodiment with a mixture containing carbon dioxide at a temperature of 20°C to 80°C.

[0019] In one embodiment, the carbon dioxide separation method may further include the step of heat-treating the carbon dioxide absorbent at a temperature of 70°C to 150°C for 30 to 250 minutes to desorb the carbon dioxide attached to the carbon dioxide absorbent.

[0020] In one embodiment, the carbon dioxide separation method may involve sequentially repeating the contact step and the desorption step to continuously separate the carbon dioxide. [Effects of the Invention]

[0021] One embodiment relates to a carbon dioxide absorbent containing an ionic substance containing a cyclic ammonium cation and a hydroxide anion. The carbon dioxide absorbent according to this embodiment contains a hydroxide anion with a small molecular weight and high basicity, which effectively improves the absorption performance per unit volume of the absorbent. Furthermore, since the carbon dioxide absorbent according to this embodiment is soluble in water, it does not cause the problem of layer separation. [Modes for carrying out the invention]

[0022] The embodiments described herein may be modified into various different forms, and the technology according to one embodiment is not limited to the embodiments described later. Furthermore, throughout the specification, when a component is described as "comprising, including, containing," "providing," "containing," or "having," it means that it may further include other components, rather than excluding other components, and does not exclude elements, materials, or processes that are not additionally listed.

[0023] Numerical ranges as used herein include lower and upper limits, all values ​​within that range, increments logically derived from the form and width of the defined range, all limited values ​​among them, and all possible combinations of upper and lower limits of numerical ranges limited in different forms. For example, if the content of a composition is limited to 10% to 80% or 20% to 50%, the numerical ranges of 10% to 50% or 50% to 80% must also be interpreted as being described herein. Unless otherwise defined herein, values ​​outside the numerical range that may occur due to experimental error or rounding of values ​​are also included in the defined numerical range.

[0024] Hereafter, unless otherwise defined, “approximately” in this specification may be considered to be a value within 30%, 25%, 20%, 15%, 10%, 5%, 3%, 2%, 1%, or 0.5% of the explicitly stated value.

[0025] As used herein, the term "alkylene group" means a diradical of a straight or branched chain with a saturated carbon bond, which may be substituted with any substituent.

[0026] As used herein, the term "alkyl group" means a linear or branched radical of a carbon-saturated bond, which may be substituted with any substituent. As used herein, the term "cycloalkyl group" means a carbon ring radical with a saturated carbon bond, which may be substituted with any substituent.

[0027] As used herein, the term "heterocycloalkyl group" means a ring radical containing one or more heteroatoms selected from the group consisting of oxygen (O), nitrogen (N), and sulfur (S), which may be substituted with any substituent. For example, "5-membered to 20-membered heterocycloalkyl group" means that the ring contains 5 to 20 carbon, oxygen, nitrogen, and / or sulfur atoms, and does not include the number of substituent atoms such as hydrogen substituted on carbon.

[0028] The present disclosure will be described in detail below with reference to the attached drawings. However, this is illustrative only, and the present disclosure is not limited to the specific embodiments described illustratively.

[0029] One embodiment provides a carbon dioxide absorbent comprising an ionic substance containing a cyclic ammonium cation and a hydroxide anion represented by the following chemical formula 1.

[0030] [ka]

[0031] In the aforementioned chemical formula 1, R 1 ~R 4 These are, independently, -H and C 1-20 Alkyl alkyl group, C 1-20 Alkoxy group, C 1-10 Alkoxy C 1-10 Alkyl alkyl group, C 5-20 A cycloalkyl group, or a 5- to 20-membered heterocycloalkyl group, R 5 and R 6 These are, independently, -H and C 1-20 Alkyl alkyl group, C 1-10 Alkoxy C 1-10 Alkyl alkyl group, C 5-20 A cycloalkyl group, or a 5- to 20-membered heterocycloalkyl group, L 1 These are single bonds, -O-, -NR 7 -, or C 1-8It is an alkylene group, and the R 7 is -H, or C 1-10 is an alkyl group, or the R 7 is the aforementioned R 5 It may bond with R to form a ring, and the R 1 ~R 7 C 1-20 Alkyl alkyl group, C 1-20 Alkoxy group, C 1-10 Alkoxy C 1-10 Alkyl alkyl group, C 5-20 The cycloalkyl groups and the 5- to 20-membered heterocycloalkyl groups may each be independently substituted with a halogen group, -OH, -NH2, or -NO2.

[0032] One embodiment of the carbon dioxide absorbent is an anion used in conventional carbon dioxide absorbents (acetate anions, phosphate anions, halogen anions, fluorine anions (BF4) - PF6 - etc.), NO3 - Compared to other materials, etc., it has a very small molecular weight and contains an ionic substance that combines a highly basic hydroxide anion (-OH) with an ammonium cation, which effectively increases the carbon dioxide scavenging (absorption) capacity per unit volume of the absorbent.

[0033] Furthermore, the ionic substances contained in the carbon dioxide absorbent according to one embodiment are all soluble in water and dissolve in the solvent before and after carbon dioxide absorption, so layer separation does not occur. On the other hand, anions conventionally used, such as phenolates, are converted to phenol by receiving protons during the carbon dioxide absorbent's absorption process, and since phenol is insoluble in water, it causes layer separation of the absorbent. This layer separation destabilizes the flow rate of the absorbent in the continuous circulation device, and additional steps such as adding additional solvent are required to eliminate the layer separation, making it less economical than the carbon dioxide absorbent according to one embodiment.

[0034] Furthermore, the absorbent according to one embodiment significantly improves the problem of viscosity increase after carbon dioxide absorption compared to before absorption, thereby enabling significantly more efficient adsorption and desorption of carbon dioxide. When phenol, carbamate, or carbonate is produced using conventional carbon dioxide absorbents, the viscosity of the reaction solution increases, reducing the efficiency of the continuous carbon dioxide absorption reaction. Moreover, high temperature conditions are required for a long time when carbon dioxide is desorbed again after absorption. However, the carbon dioxide absorbent according to one embodiment does not significantly increase viscosity after capture, making it effective for carbon dioxide absorption and desorption.

[0035] In one embodiment, the R 1 ~R 4 These are, independently, -H and C 1-15 Alkyl alkyl group, C 1-10 Alkyl alkyl group, C 1-8 Alkyl alkyl group, C 1-5 Alkyl alkyl group, C 1-3 Alkyl group, methyl group, ethyl group, C 1-15 Alkoxy group, C 1-10 Alkoxy group, C 1-8 Alkoxy group, C 1-5 Alkoxy group, C 1-3 Alkoxy group, methoxy group, ethoxy group, C 1-8 Alkoxy C 1-8 Alkyl alkyl group, C 1-5 Alkoxy C 1-5 Alkyl alkyl group, C 1-3 Alkoxy C 1-3 Alkyl group, ethoxymethyl group, methoxymethyl group, C 5-15 Cycloalkyl groups, C 5-10 Cycloalkyl groups, C 5-8 Cycloalkyl groups, C 6-8 The group may be a cycloalkyl group, a cyclopentyl group, a cyclohexyl group, or a heterocycloalkyl group with 5 to 15 members, 5 to 10 members, 5 to 8 members, or 6 to 8 members.

[0036] In one embodiment, the R 5 and R 6 These are, independently, -H and C 1-15Alkyl alkyl group, C 1-10 Alkyl alkyl group, C 1-8 Alkyl alkyl group, C 1-5 Alkyl alkyl group, C 1-3 Alkyl group, methyl group, ethyl group, C 1-8 Alkoxy C 1-8 Alkyl alkyl group, C 1-5 Alkoxy C 1-5 Alkyl alkyl group, C 1-3 Alkoxy C 1-3 Alkyl group, ethoxymethyl group, methoxymethyl group, C 5-15 Cycloalkyl groups, C 5-10 Cycloalkyl groups, C 5-8 Cycloalkyl groups, C 6-8 The group may be a cycloalkyl group, a cyclopentyl group, a cyclohexyl group, or a heterocycloalkyl group with 5 to 15 members, 5 to 10 members, 5 to 8 members, or 6 to 8 members.

[0037] In one embodiment, L 1 These are single bonds, -O-, -NR 7 -, C 1-8 Alkylene group, C 1-3 The group is an alkylene group, a methylene group, or an ethylene group, and the R 7 is -H, C 1-10 Alkyl alkyl group, C 1-8 Alkyl alkyl group, C 1-5 Alkyl alkyl group, C 1-3 The R is an alkyl group, a methyl group, or an ethyl group, or the R 7 is the aforementioned R 5 It may combine with R to form a ring. In this case, the R 7 R 5 When bonded to form a ring (bicyclo), it may be represented by the following chemical formula 3.

[0038] [ka]

[0039] In the above chemical formula 3, substituent R 1 ~R 6 and L 1This is the same as the definition in chemical formula 1 or chemical formula 2, L 2 C 1-5 Alkylene group, C 1-3 Alkylene group, C 1-2 It may be an alkylene group, a methylene group, or an ethylene group.

[0040] In one embodiment, the R 1 ~R 7 The alkyl group, alkoxy group, alkoxyalkyl group, cycloalkyl group, and heterocycloalkyl group may each be independently substituted with any substituent, for example, one or more halogen groups selected from the group consisting of I, Br, Cl, and F, -OH, -NH2, or -NO2.

[0041] Alternatively, in one embodiment, the R 1 ~R 4 These are, independently, -H and C 1-10 Alkyl alkyl group, C 1-10 Alkoxy group, C 1-5 Alkoxy C 1-5 Alkyl alkyl group, C 5-10 A cycloalkyl group, or a 5- to 10-membered heterocycloalkyl group, and the R 5 and R 6 These are, independently, -H and C 1-10 Alkyl alkyl group, C 1-5 Alkoxy C 1-5 Alkyl alkyl group, C 5-10 A cycloalkyl group, or a 5- to 10-membered heterocycloalkyl group, and the L 1 These are single bonds, -O-, -NR 7 -, or C 1-5 It is an alkylene group, and the R 7 is -H, or C 1-5 is an alkyl group, or the R 7 is the aforementioned R 5 It may bond with R to form a ring, and the R 1 ~R 7 C 1-10 Alkyl alkyl group, C 1-10 Alkoxy group, C 1-5Alkoxy C 1-5 Alkyl alkyl group, C 5-10 The cycloalkyl groups and the 5- to 10-membered heterocycloalkyl groups may each be independently substituted with a halogen group, -OH, -NH2, or -NO2.

[0042] In one embodiment, the cyclic ammonium cation may be represented by the following chemical formula 2.

[0043] [ka]

[0044] In the aforementioned chemical formula 2, R 5 and R 6 These are, independently, -H and C 1-20 Alkyl alkyl group, C 1-10 Alkoxy C 1-10 Alkyl alkyl group, C 5-20 A cycloalkyl group, or a 5- to 20-membered heterocycloalkyl group, L 1 These are single bonds, -O-, -NR 7 -, or C 1-8 It is an alkylene group, and the R 7 is -H, or C 1-10 is an alkyl group, or the R 7 is the aforementioned R 5 It may bond with R to form a ring, and the R 5 ~R 7 C 1-10 Alkyl alkyl group, C 1-20 Alkyl alkyl group, C 1-10 Alkoxy C 1-10 Alkyl alkyl group, C 5-20 The cycloalkyl groups and the 5- to 20-membered heterocycloalkyl groups may each be independently substituted with a halogen group, -OH, -NH2, or -NO2.

[0045] In one embodiment, the substituent R of chemical formula 2 5 , R 6 , and L 1The definition is the same as in the above chemical formula 1, and specifically, in one embodiment, the R 5 and R 6 Each of them is independent of C 1-10 Alkyl alkyl group, C 1-5 Alkoxy C 1-5 Alkyl alkyl group, C 5-10 The L 1 These are single bonds, -O-, -NR 7 -, or C 1-8 It is an alkylene group, and the R 7 is -H, or C 1-5 It is an alkyl group, and the R 5 ~R 7 C 1-10 Alkyl alkyl group, C 1-5 Alkoxy C 1-5 Alkyl alkyl group, C 5-10 The cycloalkyl groups and the 5- to 10-membered heterocycloalkyl groups may each be independently substituted with -OH, -NH2, or -NO2.

[0046] Alternatively, in one embodiment, in the chemical formula 2, the R 5 and R 6 Each of them is independent of C 1-5 Alkyl alkyl group, or C 1-3 Alkoxy C 1-3 It is an alkyl group, and the L 1 is -O- or a methylene group, and the R 5 and R 6 C 1-5 Alkyl alkyl groups, and C 1-3 Alkoxy C 1-3 Each alkyl group may be independently substituted with an -OH group.

[0047] In one embodiment, the cyclic ammonium cation is [ka] That's fine.

[0048] In one embodiment, the carbon dioxide absorbent may further contain water as a solvent. Alternatively, in one embodiment, the carbon dioxide absorbent may further contain one or more solvents other than water, such as an amine compound. In one embodiment, the amine compound is not particularly limited, but may include, for example, monoethanolamine (MEA), N-methyldiethanolamine (MDEA), diethanolamine (DEA), triethanolamine (TEA), 2-amino-2-methyl-1-propanol (AMP), and / or piperazine (PZ). Alternatively, it may further contain a non-aqueous solvent, such as ethylene glycol, propylene glycol, methyl glycol, methyl isopropyl carboxylate, methyl diethyl carboxylate, triethylene glycol, dimethyl sulfonate, and / or diethyl sulfonate.

[0049] In one embodiment, the ionic substance may be present in amounts of 5% to 50% by weight, 5% to 40% by weight, 10% to 50% by weight, 10% to 40% by weight, 20% to 50% by weight, 20% to 40% by weight, 25% to 40% by weight, 25% to 30% by weight, about 25% by weight, or about 30% by weight, relative to the total weight of the carbon dioxide absorbent, but is not necessarily limited to these ranges.

[0050] In one embodiment, if the carbon dioxide absorbent contains water as a solvent, the amount of water may be 30% to 90% by weight, or 40% to 80% by weight, based on the total weight of the carbon dioxide absorbent, but is not necessarily limited to these ranges. In one embodiment, if the carbon dioxide absorbent contains only water as a solvent, the amount of water may be 50% to 90% by weight, 50% to 80% by weight, 60% to 80% by weight, or about 70% by weight, but is not necessarily limited to these ranges. In one embodiment, if the carbon dioxide absorbent further contains a solvent other than water as a solvent, the amount of water may be 30% to 60% by weight, 30% to 50% by weight, 40% to 50% by weight, or about 45% by weight, but is not necessarily limited to these ranges.

[0051] In one embodiment, if the carbon dioxide absorbent further contains a solvent other than water, the solvent other than water may be present in amounts of 10% to 50% by weight, 10% to 40% by weight, 20% to 50% by weight, 20% to 40% by weight, 25% to 40% by weight, 25% to 30% by weight, about 25% by weight, or about 30% by weight relative to the total weight of the carbon dioxide absorbent, but is not necessarily limited to these ranges. For example, the solvent other than water may be an amine compound.

[0052] In one embodiment, the capture (or absorption) performance (unit: mmol / mL) of the carbon dioxide absorbent may be 0.5 or higher, 0.9 or higher, 1.0 or higher, 1.5 or higher, 1.8 or higher, 3.0 or higher, 3.5 or higher, 4.0 or higher, or 4.3 or higher. In this case, the upper limit may be, for example, 2.0 or lower, 3.0 or lower, 4.8 or lower, 5.0 or lower, or 5.5 or lower. The capture performance refers to the number of moles of carbon dioxide captured per unit volume of the carbon dioxide absorbent.

[0053] In one embodiment, the capture (or absorption) equivalent (unit: mol / mol) of the carbon dioxide absorbent may be 0.7 or more, 1.0 or more, 1.3 or more, 1.8 or more, or 2.0 or more. In this case, the upper limit may be, for example, 4.0 or less, 3.0 or less, or 2.5 or less. The capture equivalent refers to the number of moles of carbon dioxide captured per unit mole of ionic substance and amine compound in the carbon dioxide absorbent.

[0054] Another embodiment provides a carbon dioxide supply agent comprising a compound formed by reacting carbon dioxide with the carbon dioxide absorbent. Another embodiment provides a method for separating carbon dioxide, which includes the step of contacting the carbon dioxide absorbent according to the above embodiment with a mixture containing carbon dioxide at a temperature of 20°C to 80°C.

[0055] In one embodiment, the temperature conditions may be, for example, 20°C to 60°C, 30°C to 60°C, 30°C to 50°C, or about 40°C. The step may also be carried out under pressure conditions of, for example, 0.1 bar to 2.0 bar, 0.5 bar to 2.0 bar, 0.5 bar to 1.5 bar, 0.7 bar to 1.3 bar, or 1.0 bar, but is not necessarily limited thereto.

[0056] The carbon dioxide separation method may further include a step of heat-treating the carbon dioxide absorbent at a temperature of 70°C to 150°C and an N2 flow rate of 100 cc / min to 300 cc / min for 30 minutes to 250 minutes to desorb the carbon dioxide attached to the absorbent. In this case, the temperature conditions are not necessarily limited to the above range, and the heat treatment may be performed at, for example, 80°C to 130°C, 80°C to 120°C, 80°C to 110°C, 85°C to 120°C, 85°C to 110°C, or 90°C to 110°C. Similarly, the time conditions are not necessarily limited to the above range, and the heat treatment may be performed for, for example, 30 minutes to 210 minutes, 50 minutes to 210 minutes, 60 minutes to 250 minutes, 60 minutes to 200 minutes, or 60 minutes to 180 minutes. Furthermore, the N2 flow conditions are not necessarily limited to the range mentioned above; for example, conditions of 150cc / min to 250cc / min, 180cc / min to 220cc / min, or 200cc / min may also be used.

[0057] Furthermore, the carbon dioxide separation method may also be a method that continuously separates carbon dioxide by sequentially repeating the steps of bringing carbon dioxide into contact with an absorbent to absorb it, and desorbing the carbon dioxide attached to the absorbent.

[0058] In one embodiment of the carbon dioxide separation method, the decomposition of the carbon dioxide absorbent is inhibited in the step of desorbing carbon dioxide under high temperature and basic conditions, thereby reducing the rate of decrease of the absorbent after carbon dioxide desorption. As a result, the carbon dioxide separation method has less loss of absorbent due to the number of steps compared to conventional carbon dioxide absorption methods using carbon dioxide absorbents, and the amount of absorbent that must be replenished after each step can be reduced, making the process more economical to operate.

[0059] Examples and experimental cases are described below with specific illustrations. However, the examples and experimental cases described later are merely illustrative of a part of one embodiment, and should not be construed as limiting the technology described herein.

[0060] <Manufacturing Examples 1 and 2> Manufacturing of Ionic Substances 133.6 mmol of iodide of each cation listed in Table 1 below, 133.6 mmol of silver(I) oxide, and 80 mL of water were added and the mixture was stirred at room temperature for 4 hours. The resulting silver iodide solid was removed by filtration, and the excess water was vacuum-dried at 50°C to obtain an ionic substance in aqueous solution. 1 1H NMR was measured, and the results are shown in Table 1 below.

[0061] <Manufacturing Example 3> Manufacturing of Ionic Substances 133.6 mmol of the cation chloride listed in Table 1 below, 140.3 mmol of potassium hydroxide, and 80 mL of ethanol were added, and the mixture was stirred at room temperature for 4 hours. The resulting potassium chloride solid was filtered off, excess water was added, and the mixture was vacuum-dried at 50°C to remove the ethanol and obtain an aqueous solution of the ionic substance. 1 1H NMR was measured, and the results are shown in Table 1 below.

[0062] <Manufacturing Example 4> Manufacturing of Ionic Substances 133.6 mmol of N-methylpiperidine, 140.3 mmol of propylene oxide, and 80 mL of ethanol were added, and the mixture was stirred at room temperature for 4 hours. After adding excess water, the mixture was vacuum-dried at 50°C to remove the ethanol and obtain an ionic substance in aqueous solution. 1 1H NMR was measured, and the results are shown in Table 1 below.

[0063] <Manufacturing Example 5> Manufacturing of Ionic Substances 133.6 mmol of the cation bromide listed in Table 1 below, 133.6 mmol of silver(I) oxide, and 80 mL of water were added and stirred at room temperature for 4 hours. The resulting silver bromide solid was removed by filtration, and the excess water was vacuum-dried at 50°C to obtain an ionic substance in aqueous solution. 1 1H NMR was measured, and the results are shown in Table 1 below.

[0064] <Manufacturing Example 6> Manufacturing of Ionic Substances After adding 133.6 mmol of ethyl sulfate of the cation shown in Table 1 below, 6.68 mmol of sulfuric acid, and 80 mL of water, the mixture was refluxed with stirring at 110°C for 16 hours. After adding excess ethanol, the mixture was vacuum-dried at 50°C to remove the water, and then 140.3 mmol of potassium hydroxide and 80 mL of ethanol were added, followed by stirring at room temperature for 4 hours. The resulting potassium sulfate solid was removed by filtration, excess water was added, and the mixture was vacuum-dried at 50°C to remove the ethanol, obtaining an ionic substance in aqueous solution. 1 1H NMR was measured, and the results are shown in Table 1 below.

[0065] <Manufacturing Examples 7 and 8> Manufacturing of Ionic Substances 133.6 mmol of chloride of each cation shown in Table 1 below, 140.3 mmol of potassium hydroxide, and 80 mL of ethanol were added, and the mixture was stirred at room temperature for 4 hours. The resulting potassium chloride solid was removed by filtration, excess water was added, and the mixture was vacuum-dried at 50°C to remove the ethanol and obtain an aqueous solution of the ionic substance. 1 1H NMR was measured, and the results are shown in Table 1 below.

[0066] [Table 1]

[0067] <Manufacturing Example 9> Manufacturing of Ionic Substances 133.6 mmol of N-methylpiperidine, 133.6 mmol of methyl iodide, and 40 mL of tetrahydrofuran were added, and the mixture was stirred at room temperature for 18 hours. The mixture was vacuum-dried at 50°C for 15 hours to remove the tetrahydrofuran and obtain a solid ionic substance. 1 1H NMR was measured, and the results are shown in Table 1 below.

[0068] <Manufacturing Examples 10 and 11> Manufacturing of Ionic Substances 133.6 mmol of the ionic substance from Production Example 2 in Table 1 above, 133.6 mmol of phenol or imidazole, and 40 mL of water were added and stirred at room temperature for 1 hour to obtain an aqueous solution of the ionic substance. 1 1H NMR was measured, and the results are shown in Table 2 below.

[0069] <Manufacturing Examples 12-13> Manufacturing of Ionic Substances 133.6 mmol of the ionic substance from Production Example 9 in Table 2 below, 133.6 mmol of silver(I) acetate or silver(I) tetrafluoroborate, and 40 mL of water were added and the mixture was stirred at room temperature for 4 hours. The resulting silver iodide solid was filtered off to obtain the ionic substance in aqueous solution. 1 1H NMR was measured, and the results are shown in Table 1 below.

[0070] <Manufacturing Example 14> Manufacturing of Ionic Substances 133.6 mmol of the ionic substance from Production Example 2 in Table 1, 133.6 mmol of phosphoric acid, and 40 mL of water were added and stirred at room temperature for 1 hour to obtain an aqueous solution of the ionic substance. 1 1H NMR was measured, and the results are shown in Table 1 below.

[0071] [Table 2]

[0072] <Examples 1-16> Production of carbon dioxide absorbent Examples 1 to 16 of carbon dioxide absorbents were manufactured using the compositions shown in Table 3 below, containing the ionic substances and solvents of Manufacturing Examples 1 to 8. Specifically, the carbon dioxide absorbents were manufactured by adding the ionic substances and solvents in the weight percentages (based on the total weight of the carbon dioxide absorbent) shown in Table 3 below, regardless of the order of addition, and mixing at a temperature of approximately 30°C for approximately 40 minutes.

[0073] [Table 3]

[0074] <Comparative Examples 1-12> Manufacturing of carbon dioxide absorbent Comparative Examples 1 to 12 carbon dioxide absorbents were manufactured using the compositions shown in Table 4 below, containing the ionic substances and solvents of Manufacturing Examples 9 to 14. Specifically, the carbon dioxide absorbents were manufactured by adding the ionic substances and solvents in the weight percentages (based on the total weight of the carbon dioxide absorbent) shown in Table 4 below, regardless of the order of addition, and mixing at a temperature of approximately 30°C for approximately 40 minutes.

[0075] [Table 4]

[0076] <Experimental Example 1> Evaluation of carbon dioxide absorption performance To evaluate the carbon dioxide absorption performance of the carbon dioxide absorbents in the examples and comparative examples, the carbon dioxide absorption performance was measured using a vapor-liquid equilibrium (VLE) apparatus. The vapor-liquid equilibrium apparatus included 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 measuring instrument, and a stirrer. During this process, the cylinder and reactor were maintained at a constant temperature of 40°C using a constant-temperature water bath and a heating block, respectively, while measuring their absorption capacity. The measurement error range for the reactor was ±0.1°C and ±0.01 bar.

[0077] The carbon dioxide absorption performance was evaluated using the following method. First, the carbon dioxide storage cylinder and the inside of the absorption reactor were thoroughly purged with nitrogen, and then carbon dioxide was filled into the carbon dioxide storage cylinder and maintained at 1 bar and 40°C. Next, the carbon dioxide absorbent solutions (6.0 g) of the examples and comparative examples were added to the absorption reactor and maintained at 40°C. Then, the valve connecting the cylinder and the reactor was 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 continuously until there was no pressure change between the cylinder and the reactor. Next, the number of moles of carbon dioxide captured due to the pressure change was calculated using the ideal gas equation.

[0078] The calculated number of moles (mmol) of carbon dioxide captured, divided by the volume (mL) of the carbon dioxide absorbent added, is shown in Tables 5 and 6 below. In addition, after evaluating the carbon dioxide absorption performance, the presence or absence of layer separation of the absorbent was observed visually, and the results are also shown. X indicates the absence of layer separation, and O indicates the presence of layer separation.

[0079] [Table 5]

[0080] [Table 6]

[0081] As can be seen from Tables 5 and 6, the carbon dioxide capture capacity of Examples 1 to 8, which used only ionic substances, was 1.6 mmol-CO2 / mL-absorbent or higher, showing improved carbon dioxide absorption performance compared to Comparative Examples 1 to 6, which also used only ionic substances. Furthermore, the carbon dioxide capture capacity of Examples 8 to 16, which further used amine compounds as solvents, was 4.2 mmol-CO2 / mL-absorbent or higher, showing improved carbon dioxide absorption performance compared to Comparative Examples 7 to 12. Moreover, since no layer separation was observed in any of the absorbents in the examples, there are no factors that destabilize the flow rate of the absorbent in the continuous circulation system, and there is no need for additional solvent additions to eliminate layer separation, making it far more efficient and economical.

[0082] Although one embodiment has been described in detail above with reference to examples and experimental examples, the scope of this embodiment is not limited to a specific example and must be interpreted according to the attached claims.

Claims

1. A carbon dioxide absorbent comprising an ionic substance containing a cyclic ammonium cation and a hydroxide anion represented by the following chemical formula 1. 【Chemistry 1】 In the aforementioned chemical formula 1, R １ ~R ４ These are, independently, -H and C １－２０ alkyl group, C １－２０ Alkoxy group, C １－１０ Alkoxy C １－１０ alkyl group, C ５－２０ A cycloalkyl group, or a 5- to 20-membered heterocycloalkyl group, R ５ and R ６ are each independently -H, C １－２０ alkyl group, C １－１０ alkoxy C １－１０ alkyl group, C ５－２０ cycloalkyl group, or a 5- to 20-membered heterocycloalkyl group, and L １ This is a single bond, -O-, -NR ７ -, or C １－８ It is an alkylene group, and the R ７ is -H, or C １－１０ is an alkyl group, or the R ７ is the aforementioned R ５ They may combine to form a ring, and The aforementioned R １ ~R ７ C １－２０ alkyl group, C １－２０ Alkoxy group, C １－１０ Alkoxy C １－１０ alkyl group, C ５－２０ Cycloalkyl groups and 5- to 20-membered heterocycloalkyl groups each independently consist of a halogen group, -OH, and -NH. ２ , or -NO ２ It may be replaced with .

2. In the aforementioned chemical formula 1, The aforementioned R １ ~R ４ These are, independently, -H and C １－１０ alkyl group, C １－１０ Alkoxy group, C １－５ Alkoxy C １－５ alkyl group, C ５－１０ A cycloalkyl group, or a 5- to 10-membered heterocycloalkyl group, The aforementioned R ５ and R ６ These are, independently, -H and C １－１０ alkyl group, C １－５ Alkoxy C １－５ alkyl group, C ５－１０ A cycloalkyl group, or a 5- to 10-membered heterocycloalkyl group, Said L １ This is a single bond, -O-, -NR ７ -, or C １－５ It is an alkylene group, and the R ７ is -H, or C １－５ is an alkyl group, or the R ７ is the aforementioned R ５ They may combine to form a ring, and The aforementioned R １ ~R ７ C １－１０ alkyl group, C １－１０ Alkoxy group, C １－５ Alkoxy C １－５ alkyl group, C ５－１０ Cycloalkyl groups and 5- to 10-membered heterocycloalkyl groups are each independently a halogen group, -OH, and -NH. ２ , or -NO ２ The carbon dioxide absorbent according to claim 1, which may be substituted with

3. The carbon dioxide absorbent according to claim 1, wherein the cyclic ammonium cation is represented by the following chemical formula 2. 【Chemistry 2】 In the aforementioned chemical formula 2, R ５ and R ６ These are, independently, -H and C １－２０ alkyl group, C １－１０ Alkoxy C １－１０ alkyl group, C ５－２０ A cycloalkyl group, or a 5- to 20-membered heterocycloalkyl group, L １ This is a single bond, -O-, -NR ７ -, or C １－８ It is an alkylene group, and the R ７ is -H, or C １－１０ is an alkyl group, or the R ７ is the aforementioned R ５ They may combine to form a ring, and The aforementioned R ５ ~R ７ C １－１０ alkyl group, C １－２０ alkyl group, C １－１０ Alkoxy C １－１０ alkyl group, C ５－２０ Cycloalkyl groups and 5- to 20-membered heterocycloalkyl groups each independently consist of a halogen group, -OH, and -NH. ２ , or -NO ２ It may be replaced with .

4. In the aforementioned chemical formula 2, The aforementioned R ５ and R ６ Each of them is independent of C １－１０ alkyl group, C １－５ Alkoxy C １－５ alkyl group, C ５－１０ These are cycloalkyl groups and 5- to 10-membered heterocycloalkyl groups. The aforementioned L １ is a single bond, -O-, -NR ７ -, or C １－８ alkylene group, and the aforementioned R ７ is -H, or C １－５ alkyl group, and The above R ５ to R ７ 's C １－１０ alkyl group, C １－５ alkoxy C １－５ alkyl group, C ５－１０ cycloalkyl group, and 5- to 10-membered heterocycloalkyl group may each independently be substituted with -OH, -NH ２ , or -NO ２ , and the carbon dioxide absorbent according to claim 3 may also be substituted.

5. In the aforementioned chemical formula 2, The aforementioned R ５ and R ６ Each of them is independent of C １－５ alkyl group, or C １－３ Alkoxy C １－３ It is an alkyl group, Said L １ is -O- or a methylene group, The aforementioned R ５ and R ６ C １－５ Alkyl alkyl groups, and C １－３ Alkoxy C １－３ The carbon dioxide absorbent according to claim 3, wherein each alkyl group may be independently substituted with -OH.

6. The carbon dioxide absorbent according to claim 1, wherein the cyclic ammonium cation is one selected from the following group of compounds. 【Transformation 3】

7. The carbon dioxide absorbent according to claim 1, further comprising water.

8. The carbon dioxide absorbent according to claim 7, further comprising one or more solvents in addition to water.

9. The carbon dioxide absorbent according to claim 8, wherein the solvent comprises an amine compound.

10. The carbon dioxide absorbent according to claim 9, wherein the amine compound comprises one or more selected from the group consisting of monoethanolamine (MEA), N-methyldiethanolamine (MDEA), diethanolamine (DEA), triethanolamine (TEA), 2-amino-2-methyl-1-propanol (AMP), and piperazine (PZ).

11. The carbon dioxide absorbent according to claim 1, wherein the ionic substance is contained in an amount of 5% to 50% by weight relative to the total weight of the carbon dioxide absorbent.

12. The carbon dioxide absorbent according to claim 7, wherein the water is contained in an amount of 30% to 90% by weight relative to the total weight of the carbon dioxide absorbent.

13. The carbon dioxide absorbent according to claim 9, wherein the amine compound is contained in an amount of 10% to 50% by weight relative to the total weight of the carbon dioxide absorbent.

14. A method for separating carbon dioxide, comprising the step of contacting a carbon dioxide absorbent according to any one of claims 1 to 13 with a mixture containing carbon dioxide under temperature conditions of 20°C to 80°C.

15. The method for separating carbon dioxide according to claim 14, further comprising the step of heat-treating the carbon dioxide absorbent at a temperature of 70°C to 150°C for 30 to 250 minutes to desorb carbon dioxide attached to the carbon dioxide absorbent.

16. The method for separating carbon dioxide according to claim 15, wherein the steps of contacting and detaching are repeated sequentially to continuously separate carbon dioxide.

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