Composition for carbon dioxide separation, solid absorbent material for carbon dioxide separation using same, and method for producing solid absorbent material for carbon dioxide separation

Abstract

[Problem] To provide a means which is capable of efficiently separating or recovering carbon dioxide from a carbon dioxide-containing gas composition that has a low partial pressure and / or a low concentration. [Solution] Provided is a composition for carbon dioxide separation, which includes an oligoamine compound that has a boiling point of 200°C or higher, and a modifier that has a boiling point of 200°C or higher, wherein: some of all nitrogen atoms in the oligoamine compound form carbamic acid or a salt structure thereof; and the ratio of the nitrogen atoms forming carbamic acid or a salt structure thereof in the oligoamine compound is 0.1% to 20% with respect to all nitrogen atoms in the oligoamine compound.

Description

Composition for carbon dioxide separation, solid absorbent for carbon dioxide separation using the same, and method for producing solid absorbent for carbon dioxide separation

[0001] The present invention relates to a composition for separating carbon dioxide, a solid absorbent material for separating carbon dioxide using the composition for separating carbon dioxide, and a method for producing a solid absorbent material for separating carbon dioxide.

[0002] In recent years, various carbon dioxide separation and capture technologies have been developed to achieve carbon neutrality. Representative carbon dioxide separation and capture technologies include chemical absorption, physical absorption, and membrane separation (Patent Documents 1 and 2, and Non-Patent Document 1).

[0003] Chemical absorption is a technology that separates carbon dioxide by utilizing a chemical reaction between the carbon dioxide and a medium such as an amine compound that binds to the carbon dioxide, and requires a large amount of energy input to absorb and release the carbon dioxide. On the other hand, it is an essential technology for recovering carbon dioxide from gases containing low partial pressure or low concentration of carbon dioxide, such as from the atmosphere (Non-Patent Document 2).

[0004] Chemical absorption methods include liquid absorption systems and solid absorption systems, and when recovering carbon dioxide from a gas containing carbon dioxide at a low partial pressure or a low concentration, a large amount of gas needs to be brought into contact with the absorbing component, so a solid absorption system with small pressure loss is considered promising. In a solid absorption system, a solid absorption material in which the absorbing component is immobilized or supported on a porous material is used to absorb or adsorb carbon dioxide (Non-Patent Document 3).

[0005] For example, Non-Patent Document 4 reports that a system in which regular mesoporous silica, typified by SBA-15, is used as a porous material and polyethylene glycol and polyethyleneimine are blended as absorption components is effective for recovering carbon dioxide from a carbon dioxide-containing gas at a low partial pressure or concentration, such as the atmosphere.

[0006] International Publication No. 2019 / 040445 International Publication No. 2017 / 146231

[0007] Tomoki Kamiya et al, "CO2 Separation from Air by Nanoparticle-Supported Liquid Membranes of Amine and Ionic Liquid Mixtures", JOURNAL OF CHEMICAL ENGINEERING OF JAPAN, Vol. 49(7), p. 607 - 613, 2016, The Chemical Engineering Society of JapanM. M. Faruque Hasan et al, "Modeling, Simulation, and Optimization of Postcombustion CO2 Capture for Variable Feed Concentration and Flow Rate. 2. Pressure Swing Adsorption and Vacuum Swing Adsorption Processes", Industrial & Engineering Chemistry Research 2012, Vol. 51, p. 15665 - 15682Dr. Xinhua Shen et al, "Polyethylenimine Applications in Carbon Dioxide Capture and Separation: From Theoretical Study to Experimental Work", ENERGY TECHNOLOGY 2017, Vol. 5, p. 822 - 833Miles A Sakwa-Nova k et al, "Role of Additives in Composite PEI / Oxide CO2 Adsorbents: Enhancement in the Amine Efficiency of Supported PEI by PEG in CO2 Capture from Simulated Ambient Air", APPLIED MATERIALS & INTERFACES, 2015, Vol. 7, p. 24748 - 24759

[0008] However, there are two major challenges to the widespread use and commercialization of solid absorbents using this ordered mesoporous silica: (1) availability of porous materials and (2) adsorption / desorption performance. Each of these challenges is explained below.

[0009] (1) Issues related to the availability of porous materials: Regular mesoporous silica, typified by SBA-15, is characterized by a structure in which meso-sized pores of uniform diameter are regularly arranged and by a large surface area, but requires a complicated manufacturing process to precisely control the pore structure. For example, according to Non-Patent Document 4, SBA-15 is synthesized by using a surfactant such as Pluronic (registered trademark) P123 as a template compound, adding a silica raw material such as tetraalkoxysilane, forming a regular liquid crystal layer such as a hexagonal structure in which rod-like micelles are aggregated, and then baking the resulting organic-inorganic composite material.

[0010] Regular mesoporous silica, which requires such a complicated manufacturing process, is difficult to obtain as a porous material and is expensive. Therefore, there was a need to develop a solid absorbent material that utilizes a highly versatile porous material in order to realize the social implementation and large-scale dissemination of a solid absorbent system that can handle low partial pressure or low concentration carbon dioxide-containing gases.

[0011] (2) Issues related to adsorption / desorption performance: In a solid absorbent that uses regular mesoporous silica as the porous material, it is important that carbon dioxide diffuses into the pores of the through-hole structure that retains the absorbing component. According to Non-Patent Document 4, a research group at the Georgia Institute of Technology added polyethylene glycol to polyethyleneimine, which is used as the absorbing component, to facilitate the diffusion of carbon dioxide into the pores, and the amount of carbon dioxide adsorbed and desorbed per mole of amine (hereinafter also referred to as "amine efficiency") was 0.2 mmol-CO ２ They have reported that it is possible to achieve superior performance exceeding 10 ...

[0012] However, even with the excellent solid absorbent disclosed in Non-Patent Document 4, the amount of carbon dioxide adsorption and desorption from a 400 ppm carbon dioxide-containing gas, assuming atmospheric conditions, did not reach 0.8 mmol / g per gram of solid absorbent, and the amount of carbon dioxide recovered in one cycle was low, at 35 g per kg of solid absorbent even in theory, and there was a large discrepancy with respect to practical performance levels in solid absorbent systems intended for low partial pressure or low concentration carbon dioxide-containing gases.

[0013] As described above, a solid absorbent that simultaneously solves (1) the problem of the availability of porous materials and (2) the problem of adsorption / desorption performance and enables efficient capture of carbon dioxide from carbon dioxide-containing gases at low partial pressures or low concentrations has not yet been developed. Therefore, in order to realize the social implementation and large-scale spread of solid absorbent systems that are compatible with carbon dioxide-containing gases at low partial pressures or low concentrations, there has been a need for the development of a solid absorbent that can achieve both high levels of amine efficiency and high levels of carbon dioxide capture per unit weight.

[0014] Therefore, an object of the present invention is to provide a means for efficiently separating or recovering carbon dioxide from a carbon dioxide-containing gas composition having a low partial pressure and / or a low concentration.

[0015] The present inventors have conducted extensive research into methods for solving the above-mentioned problems, and as a result, have found that the above-mentioned object can be achieved by a composition for carbon dioxide separation that contains an oligoamine compound having a boiling point of 200°C or higher and a modifier having a boiling point of 200°C or higher, in which a portion of all nitrogen atoms of the oligoamine compound have a carbamic acid or salt structure, thereby completing the present invention.

[0016] The following describes in detail the embodiments of the present invention. The embodiments shown here are merely examples for embodying the technical concept of the present invention and are not intended to limit the present invention. Therefore, all other embodiments, methods of use, and operational techniques that can be conceived by those skilled in the art without departing from the spirit of the present invention are included within the scope and spirit of the present invention, as well as within the scope of the inventions described in the claims and their equivalents. The embodiments described in this specification can be arbitrarily combined to create other embodiments. Unless otherwise specified, operations and measurements of physical properties are performed at room temperature (20-25°C) and a relative humidity of 45-55% RH.

[0017] In this specification, the term "X to Y" indicating a range means "X or more and Y or less." In addition, in this specification, "and / or" is used to mean including at least one of the components listed before and after it. For example, "A and / or B" includes A only, B only, and a combination of A and B. In this specification, the expression "~acid (salt)" means "~acid and / or its salt." In addition, in this specification, "weight" and "mass," "wt %" and "mass %," and "parts by weight" and "parts by mass" are treated as synonyms.

[0018] <<Examples of the Invention>> The present invention includes the following aspects and configurations.

[0019] [1] A carbon dioxide separation composition comprising an oligoamine compound having a boiling point of 200°C or higher and a modifier having a boiling point of 200°C or higher, wherein a part of all nitrogen atoms of the oligoamine compound have a carbamic acid or salt structure thereof, and the proportion of nitrogen atoms forming the carbamic acid or salt structure thereof in the oligoamine compound is 0.1% to 20% of all nitrogen atoms of the oligoamine compound; [2] The carbon dioxide separation composition according to [1] above, wherein the water content is 1% by weight to 30% by weight of the total weight of the carbon dioxide separation composition; [3] The carbon dioxide separation composition according to [1] or [2] above, wherein the oligoamine compound is a polyethyleneimine having a number average molecular weight of 200 or more and less than 2000; [4] The carbon dioxide separation composition according to any of [1] to [3] above, wherein the oligoamine compound is a compound in which primary amine structures account for 5% or more of all amine structures; [5] The carbon dioxide separation composition according to any one of [1] to [4] above, wherein the HSP values ​​of the modifier are ΔD of 12 or more and 22 or less, ΔP of 5 or more and 15 or less, and ΔH of 3 or more and 30 or less; [6] The carbon dioxide separation composition according to any one of [1] to [5] above, wherein the modifier is a compound having a polyethylene glycol structure; [7] A solid absorbent for carbon dioxide separation, wherein the carbon dioxide separation composition according to any one of [1] to [6] above is supported on a hydrophilic silica gel; [8] The solid absorbent for carbon dioxide separation according to [7] above, wherein the physical properties of the hydrophilic silica gel satisfy one or more selected from the group consisting of the following (i) to (iv): (i) a pore volume of 0.6 cm ３ / g to 3.0 cm ３ / g; (ii) an average pore diameter of 5 nm to 80 nm; (iii) a specific surface area of ​​70 m ２ / g~800m ２ / g; (iv) a bulk density of 0.10 g / cm ３[9] The solid absorbent for carbon dioxide separation according to [7] or [8] above, which satisfies one or more selected from the group consisting of the following (i) and (ii): (i) in a carbon dioxide adsorption / desorption test using air having a carbon dioxide concentration of 300 ppm by volume to 500 ppm by volume and an absolute humidity of 2 g / kg or less, in a step of releasing carbon dioxide absorbed by the solid absorbent at 40°C at 70°C, the amount of carbon dioxide adsorbed / desorbed per gram of the solid absorbent is 0.90 mmol or more, and the amount of carbon dioxide adsorbed / desorbed per mole of amine contained in the solid absorbent is 0.20 mol or more; (ii) In a carbon dioxide adsorption / desorption test using air having a carbon dioxide concentration of 9000 volume ppm to 11000 volume ppm and an absolute humidity of 2 g / kg or less, in a step of releasing carbon dioxide absorbed by the solid absorbent at 70°C at 100°C, the amount of carbon dioxide adsorbed and desorbed per gram of the solid absorbent is 1.30 mmol or more, and the amount of carbon dioxide adsorbed and desorbed per mole of amine contained in the solid absorbent is 0.20 mol or more;

[10] A method for producing a solid absorbent for separating carbon dioxide, comprising: (1) a first step of preparing an impregnation liquid containing an oligoamine compound having a boiling point of 200°C or higher, a modifier having a boiling point of 200°C or higher, and water; (2) a second step of impregnating a hydrophilic silica gel with the impregnation liquid; (3) a third step of separating the hydrophilic silica gel impregnated with the impregnation liquid from excess of the impregnation liquid; and (4) a fourth step of drying the hydrophilic silica gel impregnated with the impregnation liquid by evaporating water in an atmosphere containing carbon dioxide;

[11] A method for producing a solid absorbent for separating carbon dioxide according to

[10] above, which satisfies one or more of the following (a) to (c): (a) the second step is carried out at a temperature range of 20°C to 90°C; (b) the second step includes a step of degassing the porous pores under a reduced pressure of -0.08 MPaG to -0.004 MPaG; (c) The fourth step is carried out using air as the carbon dioxide-containing atmosphere at a temperature in the range of 30°C to 100°C.

[0020] When the carbon dioxide separation composition is supported on a carrier such as a porous material (particularly hydrophilic silica gel) (i.e., when a solid absorbent is formed), it can efficiently separate or recover carbon dioxide from a low partial pressure and / or low concentration carbon dioxide-containing gas composition. More specifically, the carbon dioxide separation composition makes it easy to form absorption sites excellent for absorbing and desorbing carbon dioxide within the micropores and mesopores of the hydrophilic silica gel. Therefore, when the carbon dioxide separation composition is supported on a carrier such as a porous material (i.e., when a solid absorbent is formed), the solid absorbent can efficiently absorb and desorb carbon dioxide from a low partial pressure and / or low concentration carbon dioxide-containing gas composition. In other words, the carbon dioxide separation composition according to this embodiment can be suitably supported on hydrophilic silica gel and can be a carbon dioxide separation composition supported on hydrophilic silica gel.

[0021] Furthermore, the above-mentioned solid absorbent material can provide a solid absorbent material that achieves a high level of both the amount of carbon dioxide adsorption and desorption per gram of solid absorbent material and the amount of carbon dioxide adsorption and desorption per mole of amine (amine efficiency), thereby providing a technology for efficiently separating or recovering carbon dioxide from a carbon dioxide-containing gas composition having a low partial pressure and / or a low concentration.

[0022] Furthermore, according to the method for producing a solid absorbent, the carbon dioxide separation composition is permeated into the micropores and mesopores of the hydrophilic silica gel, and the composition is easily concentrated while remaining in the micropores and mesopores of the hydrophilic silica gel. This makes it possible to obtain a solid absorbent having absorption sites that are excellent at absorbing and desorbing carbon dioxide, and to provide a solid absorbent that can efficiently absorb and desorb carbon dioxide from a carbon dioxide-containing gas composition at a low partial pressure and / or a low concentration.

[0023] In completing the carbon dioxide separation composition according to this embodiment, the present inventors conducted extensive research as follows. First, they investigated a carrier for supporting the carbon dioxide separation composition. The present inventors focused on silica gel as a widely available porous material. Silica gel, which is synthesized by a gel process using sodium silicate and mineral acid as raw materials, is readily available and inexpensive. Furthermore, because silica gel has large macropores connected to micropores and mesopores within its structure, they envisioned that if an absorbing component could be effectively supported in the micropores and mesopores, it would be possible to accelerate the diffusion of carbon dioxide within the pores and prepare a high-performance solid absorbent.

[0024] However, since general-purpose silica gel has a complex, intricate, mesh-like pore structure, it is not easy to penetrate and impregnate the amine component, making it difficult to use general-purpose silica gel as a porous material constituting a solid absorbent (Non-Patent Document 3: ENERGY TECHNOLOGY 2017, 5, pp. 822-833).

[0025] As a result of extensive research, the present inventors have discovered that the reason why it is difficult to use silica gel as a porous material for a solid absorbent is due to the carbon dioxide separation composition. It is known that the ordered mesoporous silica employed as a porous material in the prior art has hydrophobic properties on the inner surface of the pores (Non-Patent Document 5: David P. Serrano et al., "Adsorption and Hydrophobic Properties of Mesostructured MCM-41 and SBA-15 Materials for Volatile Organic Compound Removal", Industrial & Engineering Chemistry Research 2004, Vol. 43, pp. 7010-7018), and organic solvents such as methanol and ethanol have been used as dilution solvents for carrying the absorbing component (Non-Patent Document 4: Miles A. Sakwa-Novak et al., “Role of Additives in Composite PEI / Oxide CO2 Adsorbents: Enhancement in the Amine Efficiency of Supported PEI by PEG in CO2 Capture from Simulated Ambient Air”, APPLIED MATERIALS & INTERFACES, 2015, Vol. 7, p. 24748-24759).

[0026] On the other hand, the inner pore surfaces of silica gel are hydrophilic and rich in silanol groups, and it has been difficult for carbon dioxide separation compositions formulated for regular mesoporous silica to penetrate and retain absorbing components in the micropores and mesopores of the silica gel.

[0027] Therefore, the present inventors have invented a carbon dioxide separation composition with properties suitable for the hydrophilic inner pore surface of silica gel, thereby making it possible to effectively support the absorbing component in the micropores and mesopores of silica gel.

[0028] Specifically, the present inventors discovered that by using a composition containing a specific amount of an oligoamine compound having a carbamic acid (salt) structure and a modifier, it is possible to effectively penetrate and retain absorbent components in the micropores and mesopores inside hydrophilic silica gel, thereby completing the present invention.

[0029] Therefore, the present invention aims to provide a solid absorbent material that (1) is constructed using a commonly available porous material and (2) can achieve both a high level of carbon dioxide recovery amount per unit weight of the solid absorbent material and a high level of carbon dioxide adsorption / desorption efficiency per mole of amine, with the aim of social implementation and large-scale dissemination of a solid absorbent material system that is compatible with low partial pressure and / or low concentration carbon dioxide-containing gases. Furthermore, the present invention provides a means for efficiently separating or recovering carbon dioxide from a low partial pressure and / or low concentration carbon dioxide-containing gas composition.

[0030] A. Composition for Carbon Dioxide Separation The composition for carbon dioxide separation according to this embodiment comprises an oligoamine compound having a boiling point of 200°C or higher and a modifier having a boiling point of 200°C or higher, wherein a portion of all nitrogen atoms in the oligoamine compound have a carbamic acid or salt structure thereof, and the proportion of nitrogen atoms forming the carbamic acid or salt structure of the oligoamine compound is 0.1% to 20% of all nitrogen atoms in the oligoamine compound. Hereinafter, the carbamic acid or salt structure thereof will be referred to as a "carbamic acid (salt) structure."

[0031] <Oligoamine Compound> An oligoamine compound is a compound having multiple amino groups. In this specification, the term "oligoamine compound" refers to a polyamine compound having a number average molecular weight of less than 2,000. In the carbon dioxide separation composition according to this embodiment, the oligoamine compound has a boiling point of 200°C or higher at normal pressure. In addition, in the carbon dioxide separation composition according to this embodiment, a portion of all nitrogen atoms (amino groups) of the oligoamine compound have a carbamic acid (salt) structure, and the proportion of nitrogen atoms forming the carbamic acid or salt structure of the oligoamine compound is 0.1% to 20% of the total nitrogen atoms of the oligoamine compound.

[0032] Here, the carbamic acid or salt structure is —N ＋ HR １ R ２ -COOH or -N ＋ HR １ R ２ -COO － (R １ and R ２ are each independently a hydrogen atom or a hydrocarbon group which may have a substituent. １ and R ２ corresponds to the group possessed by the amino group of the oligoamine compound. １ and R ２ is preferably a hydrogen atom or a hydrocarbon group having 1 to 20 carbon atoms, and R １ and R ２ The substituents on the amine compound are preferably primary, secondary, or tertiary amino groups. The carbamic acid or salt structure in the oligoamine compound is formed by reaction with carbon dioxide as represented by the following formula (i) or (ii):

[0033]

[0034] In the carbon dioxide separation composition according to this embodiment, some of the amino groups (amine structures) of the oligoamine compound constitute a carbamic acid (salt) structure. In the oligoamine compound, the proportion of nitrogen atoms forming the carbamic acid (salt) structure is 0.1% to 20% of the total nitrogen atoms in the oligoamine compound. If the proportion of carbamic acid (salt) structures in the oligoamine compound (the proportion of nitrogen atoms forming the carbamic acid (salt) structure in the oligoamine compound) is less than 0.1%, the oligoamine compound will not be sufficiently hydrophilic, and when the oligoamine compound is supported on hydrophilic silica gel to form a solid absorbent for carbon dioxide separation, the impregnation liquid will be less likely to penetrate into the micropores and mesopores, making it more difficult to retain the carbon dioxide separation composition in the micropores and mesopores, and reducing the carbon dioxide adsorption and desorption performance. If the proportion of carbamic acid (salt) structures in the oligoamine compound (the proportion of nitrogen atoms forming the carbamic acid (salt) structure in the oligoamine compound) exceeds 20%, the number of amino groups that effectively act on the adsorption and desorption of carbon dioxide will decrease, resulting in a decrease in the carbon dioxide adsorption and desorption performance. In the oligoamine compound, the proportion of nitrogen atoms forming the carbamic acid (salt) structure is preferably 0.2% to 18%, more preferably 0.3% to 15%, even more preferably 0.4% to 10%, particularly preferably 0.5% to 8%, and most preferably 1% to 5%, relative to the total nitrogen atoms of the oligoamine compound. According to one embodiment, the ratio of nitrogen atoms forming a carbamic acid or salt structure of the oligoamine compound to the total nitrogen atoms of the oligoamine compound is 0.1% to 10%, 0.1% to 5%, 0.5% to 10%, 0.5% to 5%, 0.8% to 10%, 0.8% to 5%, 1% to 10%, 1% to 4%, or 1% to 3%.

[0035] When the proportion of carbamic acid (salt) structures in the oligoamine compound (the proportion of nitrogen atoms forming the carbamic acid (salt) structure in the oligoamine compound) is within this range, the hydrophilicity of the oligoamine compound is improved, resulting in improved water retention. As a result, when carbon dioxide is separated using the carbon dioxide separation composition, an increase in viscosity of the absorbing component is suppressed even under low-humidity operating conditions, and carbon dioxide adsorption and desorption performance can be maintained. In addition, because the affinity of the oligoamine compound with the hydrophilic silica gel surface is improved, when the oligoamine compound is supported on the hydrophilic silica gel to form a solid absorbent for carbon dioxide separation, the impregnation liquid can easily penetrate into the micropores and mesopores, forming absorption sites in which the carbon dioxide separation composition is retained in the micropores and mesopores. A method for converting some of the amino groups into an oligoamine compound with a carbamic acid (salt) structure will be described later.

[0036] To confirm the formation of a carbamic acid (salt) structure in an oligoamine compound, dissolve the oligoamine compound or the carbon dioxide separation composition in heavy water, etc. １３ C-NMR can be measured to confirm the presence of a signal (peak) around 160 ppm. Furthermore, by integrating the peak around 160 ppm and comparing the area with that of an internal standard or other carbon atoms, the ratio of carbamic acid (salt) structures to all nitrogen atoms in the oligoamine compound can be determined. Furthermore, IR spectra can be measured to determine the ratio of carbamic acid (salt) structures to all nitrogen atoms in the oligoamine compound. －１ ~1550cm －１ The production of a carbamic acid (salt) structure can also be determined by confirming that a peak derived from the carbamic acid (salt) structure appears in the vicinity of the peak (Non-Patent Document 6: Chenhu Sun et al., "Infrared Spectroscopic Study of Reaction of Carbon Dioxide with Aqueous Monoethanolamine Solutions", Industrial & Engineering Chemistry Research 2016, Vol. 55, pp. 6276-6283).

[0037] In the carbon dioxide separation composition according to this embodiment, the oligoamine compound is preferably a compound that has a low vapor pressure and is not easily volatilized in the treated gas. The boiling point of the oligoamine compound is 200°C or higher at normal pressure, preferably 300°C or higher, more preferably 350°C or higher, even more preferably 400°C or higher, particularly preferably 450°C or higher, and most preferably has no boiling point. In practical terms, if the oligoamine compound has a boiling point, the boiling point of the oligoamine compound is preferably 1000°C or lower at normal pressure. The boiling point of the oligoamine compound can be measured by detecting a differential thermal peak due to evaporation using differential thermal analysis.

[0038] In the carbon dioxide separation composition according to this embodiment, the total amine value of the oligoamine compound is preferably, for example, 400 KOHmg / g to 1500 KOHmg / g, more preferably 600 KOHmg / g to 1400 KOHmg / g, even more preferably 800 KOHmg / g to 1350 KOHmg / g, and particularly preferably 900 KOHmg / g to 1300 KOHmg / g. Oligoamine compounds having such an amine value have excellent reactivity with carbon dioxide, and are therefore advantageous in increasing the amount of carbon dioxide adsorption and desorption in solid absorbents carrying the carbon dioxide separation composition. The total amine value is expressed as the weight (mg) of potassium hydroxide equivalent to the acid required to neutralize 1 g of sample, and can be measured, for example, by a method conforming to ASTM D2074. Since the carbamic acid (salt) structure of the oligoamine compound releases carbon dioxide when the total amine value is measured, the nitrogen atom that formed the carbamic acid (salt) structure is calculated as an amine. Therefore, the total amine value of the oligoamine compound is the same for both the oligoamine compound having a carbamic acid (salt) structure and the raw material oligoamine compound described below.

[0039] In the carbon dioxide separation composition according to this embodiment, the oligoamine compound preferably contains a primary amino group (primary amine structure) from the viewpoint of quickly reacting with carbon dioxide. The proportion of primary amino groups among all amino groups in the oligoamine compound (proportion of primary amine structures among all amine structures in the oligoamine compound) is preferably 5% or more, more preferably 10% to 70%, even more preferably 12% to 60%, particularly preferably 15% to 50%, and most preferably 20% to 40%. The proportion of primary amino groups in the oligoamine compound (proportion of primary amine structures in the oligoamine compound) is １３ The ratio of primary amino groups in the oligoamine compound is determined by measuring C-NMR and comparing the area of ​​the carbon atom adjacent to the amine. Note that the ratio of primary amino groups in the oligoamine compound herein refers to the ratio of primary amino groups in the oligoamine compound having a carbamic acid (salt) structure, and differs from the ratio of primary amino groups in the raw material of the oligoamine compound (raw material oligoamine compound) described below.

[0040] The number average molecular weight of the oligoamine compound is preferably 200 or more and less than 2000, more preferably 200 to 1500, even more preferably 200 to 1000, still more preferably 250 to 900, particularly preferably 280 to 800, and most preferably 300 to 700. According to one embodiment, the number average molecular weight of the oligoamine compound is 200 to 800, 300 to 900, 300 to 800, or 200 to 600. An oligoamine compound having such a number average molecular weight is advantageous in that it can reduce both the vapor pressure and viscosity and thereby increase the amount of adsorption and desorption while reducing volatility.

[0041] The number average molecular weight of an oligoamine compound can be measured by boiling point elevation using an ebullometer or the like. In the boiling point elevation method, a fixed amount of solvent is sampled and the boiling point is measured; then, a trace amount of solute is dissolved in the solvent, the boiling point of the solution is measured, and the molecular weight is calculated using the following formula. This makes it possible to determine the molar mass of the solute, and when an oligoamine compound is used as the solute, this molar mass can be used as the number average molecular weight. Examples of solvents that can be used include methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, ethylene glycol monomethyl ether, ethylene glycol dimethyl ether, and diethylene glycol dimethyl ether.

[0042] ・Δtb = ΔKb × m (boiling point elevation: Δtb [K], molar boiling point elevation: ΔKb [K], molar concentration of solute: m [mol / kg]) ・m = w / M × 1000 / W (molar concentration of solute: m [mol / kg], mass of solute: w [g], molar mass of solute: M [g / mol], mass of solvent: W [g]).

[0043] The molecular weight distribution (weight average molecular weight (Mw) / number average molecular weight (Mn)) of the oligoamine compound is, for example, 1 to 20, preferably 1 to 15, more preferably 1 to 10, and even more preferably 1 to 5.

[0044] Specific examples of oligoamine compounds include polyethyleneimine, modified polyethyleneimine in which some of the primary amino groups of polyethyleneimine have been converted to secondary amino groups by introducing organic groups, diethylenetriamine, modified diethylenetriamine in which some of the primary amino groups of diethylenetriamine have been converted to secondary amino groups by introducing organic groups, triethylenetetramine, modified triethylenetetramine in which some of the primary amino groups of triethylenetetramine have been converted to secondary amino groups by introducing organic groups, tetraethylenepentamine, modified tetraethylenepentamine in which some of the primary amino groups of tetraethylenepentamine have been converted to secondary amino groups by introducing organic groups, pentaethylenehexamine, modified pentaethylenehexamine in which some of the primary amino groups of pentaethylenehexamine have been converted to secondary amino groups by introducing organic groups. Examples of such an amino acid include ethylenehexamine, hexaethyleneheptamine, modified hexaethyleneheptamine in which some of the primary amino groups of hexaethyleneheptamine have been converted to secondary amino groups by introducing organic groups, heptaethyleneoctamine, modified heptaethyleneoctamine in which some of the primary amino groups of heptaethyleneoctamine have been converted to secondary amino groups by introducing organic groups, tris(2-aminoethyl)amine, modified tris(2-aminoethyl)amine in which some of the primary amino groups of tris(2-aminoethyl)amine have been converted to secondary amino groups by introducing organic groups, tetrakis(2-aminoethyl)ethylenediamine, and modified tetrakis(2-aminoethyl)ethylenediamine in which some of the primary amino groups of tetrakis(2-aminoethyl)ethylenediamine have been converted to secondary amino groups by introducing organic groups.

[0045] Among these, polyethyleneimine, modified polyethyleneimine in which some of the primary amino groups of polyethyleneimine have been converted to secondary amino groups by introducing organic groups, modified tetraethylenepentamine in which some of the primary amino groups of tetraethylenepentamine have been converted to secondary amino groups by introducing organic groups, pentaethylenehexamine, modified pentaethylenehexamine in which some of the primary amino groups of pentaethylenehexamine have been converted to secondary amino groups by introducing organic groups, hexaethyleneheptamine, and hexaethyleneheptamine in which some of the primary amino groups of hexaethyleneheptamine have been converted to secondary amino groups by introducing organic groups, are particularly preferred because of their low vapor pressure and low volatility in the treatment gas. Preferred are modified hexaethyleneheptamine, heptaethyleneoctamine, and heptaethyleneoctamine in which some of the primary amino groups have been converted to secondary amino groups by introducing organic groups; modified tris(2-aminoethyl)amine in which some of the primary amino groups have been converted to secondary amino groups by introducing organic groups; tetrakis(2-aminoethyl)ethylenediamine; and modified tetrakis(2-aminoethyl)ethylenediamine in which some of the primary amino groups have been converted to secondary amino groups by introducing organic groups.

[0046] From the viewpoints of availability and low volatility, the oligoamine compound is most preferably polyethyleneimine. According to one embodiment, the oligoamine compound is polyethyleneimine having a number average molecular weight of 200 or more and less than 2000 (preferably 200 to 1000). According to one embodiment, the carbon dioxide separation composition according to this embodiment includes polyethyleneimine having a boiling point of 200°C or more and a number average molecular weight of 200 or more and less than 2000 (preferably 200 to 1000), and a modifier having a boiling point of 200°C or more, and a part of all nitrogen atoms of the polyethyleneimine has a carbamic acid or a salt structure thereof.

[0047] The oligoamine compound may be a commercially available product. A commercially available oligoamine compound that does not have a carbamic acid (salt) structure may be converted into a carbamic acid (salt) structure by the method described below, and used as the oligoamine compound for the carbon dioxide separation composition of this embodiment. Examples of oligoamine compounds that do not have a carbamic acid (salt) structure include commercially available polyethyleneimine products such as SP-003, SP-006, SP-012, and SP-018 manufactured by Nippon Shokubai Co., Ltd.

[0048] The oligoamine compounds may be used singly or in combination of two or more.

[0049] The weight ratio of the oligoamine compound to the modifier described below (weight of the oligoamine compound:weight of the modifier) ​​is preferably 10:90 to 95:5, more preferably 12:88 to 90:10, even more preferably 15:85 to 85:15, particularly preferably 20:80 to 82:18, and most preferably 30:70 to 80:20. By containing the oligoamine compound and the modifier in the above ranges, the amount of carbon dioxide adsorption and desorption can be further increased in the solid absorbent supporting the carbon dioxide separation composition.

[0050] The content of the oligoamine compound is preferably 30% to 99% by weight, more preferably 35% to 95% by weight, and even more preferably 40% to 90% by weight, based on the total weight of the nonvolatile content of the carbon dioxide separation composition. According to one embodiment, the content of the oligoamine compound is 32% to 99% by weight, 32% to 98% by weight, 32% to 95% by weight, 33% to 92% by weight, 33% to 90% by weight, 35% to 92% by weight, 35% to 90% by weight, 35% to 85% by weight, or 35% to 80% by weight, based on the total weight of the nonvolatile content of the carbon dioxide separation composition. According to one embodiment, the content of the oligoamine compound is 20% to 60% by weight, 40% to 60% by weight, 40% to 80% by weight, 50% to 80% by weight, or 60% to 80% by weight, based on the total weight of the nonvolatile content of the carbon dioxide separation composition. By containing the oligoamine compound in the above range, the amount of carbon dioxide adsorption and desorption in the solid absorbent material carrying the carbon dioxide separation composition can be further increased. Note that the non-volatile content of the carbon dioxide separation composition is the non-volatile content when dried at 120°C for 6 hours.

[0051] To obtain an oligoamine compound in which some of the amino groups have a carbamic acid (salt) structure, the raw material oligoamine compound (hereinafter referred to as raw material oligoamine compound) is brought into contact with carbon dioxide. The carbon dioxide is not limited to a gas containing 100% by volume of carbon dioxide, but may be any gas containing carbon dioxide. For example, air may be used as the carbon dioxide-containing gas.

[0052] For example, to form a carbamic acid (salt) structure in the starting oligoamine compound, the starting oligoamine compound may be contacted with carbon dioxide or a gas containing carbon dioxide (e.g., air) before being supported on a support such as a porous material, or the starting oligoamine compound may be contacted with carbon dioxide or a gas containing carbon dioxide (e.g., air) after being supported on a support such as a porous material. Specifically, carbon dioxide or a gas containing carbon dioxide (e.g., air) may be introduced into an impregnation liquid containing the starting oligoamine compound and a modifier, or a support such as a porous material may be impregnated with an impregnation liquid containing the starting oligoamine compound and a modifier, and then carbon dioxide or a gas containing carbon dioxide (e.g., air) may be introduced into the support carrying the impregnation liquid. Alternatively, the impregnation liquid containing the starting oligoamine compound and a modifier may be impregnated into a support such as a porous material, and the impregnation liquid may be concentrated in air while the impregnation liquid is being impregnated into the support such as a porous material. Examples of concentration methods include a method of impregnating the starting oligoamine compound and the modifier while evaporating water using a rocking mixer or the like.

[0053] The starting oligoamine compound is preferably contacted with carbon dioxide or a gas containing carbon dioxide (e.g., air) at a temperature of preferably 30 to 100°C, more preferably 40 to 98°C, even more preferably 50 to 95°C, particularly preferably 50 to 90°C, and most preferably 55 to 85°C. The time for contacting the starting oligoamine compound with carbon dioxide or a gas containing carbon dioxide (e.g., air) is preferably 0.1 to 48 hours, more preferably 0.2 to 24 hours, even more preferably 0.5 to 12 hours, particularly preferably 1 to 10 hours, and most preferably 2 to 8 hours. According to one embodiment, the time for contacting the starting oligoamine compound with carbon dioxide or a gas containing carbon dioxide (e.g., air) is 1 to 8 hours, 3 to 8 hours, 4 to 8 hours, or 2 to 10 hours. According to one embodiment, the starting oligoamine compound is contacted with carbon dioxide or a gas containing carbon dioxide (e.g., air) at 50°C to 95°C (or 55 to 90°C) for 0.5 to 12 hours (or 1 to 10 hours).

[0054] From the viewpoint of improving the solubility of the carbamic acid (salt) structure, the contact of the raw oligoamine compound with carbon dioxide or a gas containing carbon dioxide (e.g., air) is preferably carried out in the presence of water. Therefore, it is preferable to impregnate a carrier such as a porous material with an impregnation liquid containing the raw oligoamine compound, a modifier, and water, and then introduce carbon dioxide or a gas containing carbon dioxide (e.g., air) into the carrier carrying the impregnation liquid, thereby contacting the raw oligoamine compound with carbon dioxide. By introducing carbon dioxide or a gas containing carbon dioxide (e.g., air) into the carrier carrying the impregnation liquid, the carrier carrying the impregnation liquid can be dried, thereby obtaining a solid absorbent carrying a carbon dioxide separation composition.

[0055] As described above, upon contact with carbon dioxide, some of the nitrogen atoms of the oligoamine compound form a carbamic acid (salt) structure. The raw material for such an oligoamine compound (raw material oligoamine compound) preferably has a total amine value of, for example, 400 KOHmg / g to 1500 KOHmg / g. The total amine value of the raw material oligoamine compound is more preferably 600 KOHmg / g to 1400 KOHmg / g, even more preferably 800 KOHmg / g to 1350 KOHmg / g, and particularly preferably 900 KOHmg / g to 1300 KOHmg / g. A raw material oligoamine compound having such an amine value can increase the amount of carbon dioxide adsorption and desorption even after forming a carbamic acid (salt) structure. The total amine value is expressed as the weight (mg) of potassium hydroxide equivalent to the acid required to neutralize 1 g of sample, and can be measured, for example, by a method conforming to ASTM D2074.

[0056] Furthermore, the raw material of the oligoamine compound (raw material oligoamine compound) preferably contains a primary amino group (primary amine structure) in order to react quickly with carbon dioxide. The raw material oligoamine compound is a compound having primary amino groups (primary amine structures) in an amount of preferably 10% to 70%, more preferably 20% to 60%, and even more preferably 30% to 50% of all amino groups. The proportion of primary amino groups in the raw material oligoamine compound (proportion of primary amine structures in the oligoamine compound) is １３ It can be determined by measuring C-NMR and comparing the areas of the carbon atoms adjacent to the amine.

[0057] <Modifier> The modifier is preferably a compound that can dissolve or disperse the oligoamine compound or the raw material oligoamine compound. For this reason, the modifier can also be called a solvent, and therefore is preferably liquid at 25°C. In the carbon dioxide separation composition according to this embodiment, the modifier has a boiling point of 200°C or higher at atmospheric pressure. The boiling point of the modifier is preferably 250°C or higher, more preferably 300°C or higher, and even more preferably 350°C or higher. The modifier may be a compound that does not have a boiling point. In practice, when the modifier has a boiling point, the boiling point of the modifier is preferably 1000°C or lower at atmospheric pressure. The boiling point of the modifier can be measured by detecting a differential thermal peak due to evaporation using differential thermal analysis.

[0058] The modifier is preferably a compound that remains in a liquid state within the operating temperature range (0°C to 120°C) of the solid absorbent for carbon dioxide separation, has a low vapor pressure (i.e., a boiling point of 200°C or higher), and is unlikely to volatilize in the treated gas. Use of a modifier with such characteristics can suppress evaporation of the carbon dioxide separation composition during operation, making it advantageous for application under a wide range of operating conditions.

[0059] The Hansen solubility parameters (HSP values) of the modifier are, for example, preferably ΔD of 12 to 22, ΔP of 5 to 15, and ΔH of 3 to 30; more preferably ΔD of 14 to 20, ΔP of 6 to 14, and ΔH of 4 to 28; even more preferably ΔD of 14.5 to 19, ΔP of 6.5 to 13.5, and ΔH of 5 to 25; and particularly preferably ΔD of 15 to 18, ΔP of 7 to 13, and ΔH of 12 to 22. If the HSP value is within the range, the oligoamine compound can be effectively dissolved or dispersed. Specific examples of HSP values ​​include triethanolamine (ΔD: 17.3, ΔP: 7.6, ΔH: 21 / boiling point 335.4°C), triethylene glycol (ΔD: 16, ΔP: 12.5, ΔH: 18.6 / boiling point 285°C), 1,6-hexanediol (ΔD: 15.7, ΔP: 8.4, ΔH: 17.8 / boiling point 250°C), and 1,9-nonanediol (ΔD: 15.7, ΔP: 7, ΔH: 15.1 / boiling point 288°C). , N-methylpyrrolidone (ΔD: 18, ΔP: 12.3, ΔH: 7.2 / boiling point 202 ° C), dimethyl phthalate (ΔD: 18.6, ΔP: 10.8, ΔH: 4.9 / boiling point 284 ° C), catechol (ΔD: 20, ΔP: 11.3, ΔH: 21.8 / boiling point 245 ° C), diethylene glycol butyl methyl ether (ΔD: 15.89, ΔP: 4.75, ΔH: 5.61 / boiling point 215 ° C), tripropylene glycol Dimethyl ether (ΔD: 15.83, ΔP: 6.35, ΔH: 4.82 / boiling point 215 ° C.), 1,3-dimethyl-2-imidazolidinone (ΔD: 18.01, ΔP: 9.58, ΔH: 8.57 / boiling point 225 ° C.), diethylene glycol monobutyl ether (ΔD: 16.29, ΔP: 6.18, ΔH: 10.46 / boiling point 230 ° C.), triethylene glycol monomethyl ether (ΔD: 16.52, ΔP: 7.45, ΔH: 11.69 / boiling point 249 ° C), diethylene glycol dibutyl ether (ΔD: 15.85, ΔP: 3.98, ΔH: 4.68 / boiling point 256 ° C), triethylene glycol butyl methyl ether (ΔD: 15.95, ΔP: 4.85, ΔH: 5.89 / boiling point 261 ° C), tetraethylene glycol dimethyl ether (ΔD: 16.08, ΔP: 5.69, ΔH: 6.98 / boiling point 275 ° C),Adiponitrile (ΔD: 16.7, ΔP: 15.66, ΔH: 6.72 / boiling point 295°C), tetraethylene glycol (ΔD: 16.73, ΔP: 9.02, ΔH: 14.58 / boiling point 314°C), tricresyl phosphate (ΔD: 18.96, ΔP: 12.26, ΔH: 4.76 / boiling point 410°C), polyethylene glycol monomethyl ether 350 (ΔD: 15.97, ΔP: 6.46, ΔH: 9.23 / boiling point > 350°C), polyethylene glycol monomethyl ether 450 (ΔD: 15.73, ΔP: 6.26, ΔH: 8.84 / boiling point > 350°C) , polyethylene glycol monomethyl ether 550 (ΔD: 15.46, ΔP: 6.08, ΔH: 8.62 / boiling point > 350 ° C), polyethylene glycol monomethyl ether 750 (ΔD: 15.21, ΔP: 5.95, ΔH: 8.71 / boiling point > 350 ° C), polyethylene glycol 200 (ΔD: 16.73, ΔP: 9.02, ΔH: 14.58 / boiling point > 300 ° C but not more than 350 ° C), polyethylene glycol 300 (ΔD: 16.24, ΔP: 8.15, ΔH: 11.8 / boiling point > 350 ° C), polyethylene glycol 400 (ΔD: 15.73, ΔP : 7.47, ΔH: 9.68 / boiling point > 350 ° C), polyethylene glycol 500 (ΔD: 15.49, ΔP: 7.2, ΔH: 8.9 / boiling point > 350 ° C), polyethylene glycol 600 (ΔD: 15.3, ΔP: 7.01, ΔH: 8.39 / boiling point > 350 ° C), polyethylene glycol 700 (ΔD: 15.16, ΔP: 6.87, ΔH: 8.06 / boiling point > 350 ° C), polyethylene glycol 800 (ΔD: 14.99, ΔP: 6.72, ΔH: 7.78 / boiling point > 350 ° C), polyethylene glycol 1000 (ΔD: 14.85, ΔP: 6.58, ΔH: 7.67 / boiling point > 350°C), polyethylene glycol 1200 (ΔD: 14.75, ΔP: 6.47, ΔH: 7.78 / boiling point > 350°C), polypropylene glycol 400 (ΔD: 16.4, ΔP: 5.56, ΔH: 7.03 / boiling point > 350°C), polypropylene glycol 600 (ΔD: 16.59, ΔP: 5.02, ΔH: 5.54 / boiling point > 350°C), polypropylene glycol 800 (ΔD: 16.89, ΔP: 4.53, ΔH: 4.74 / boiling point > 350°C), polypropylene glycol 1000 (ΔD: 17.4, ΔP: 3.9,Examples include polypropylene glycol 1200 (ΔD: 17.84, ΔP: 3.4, ΔH: 4.03 / boiling point > 350°C), and polypropylene glycol 1200 (ΔD: 17.84, ΔP: 3.4, ΔH: 4.03 / boiling point > 350°C). The HSP value can be determined by the methods described in <1> to <3> below.

[0060] HSP value calculation method <1> Hansen, Charles (2007). Hansen Solubility Parameters: A user's handbook, Second Edition. Boca Raton, Fla.: CRC Press. <2> Emmanuel Stefanis and Costas Panayiotou, Int J Thermophys (2008) 29:568-585 <3> HSPiP: Hansen Solubility Parameter in Practice. http: / / www. hansen-solubility.com / .

[0061] Specific examples of the modifier include N-methylpyrrolidone (202°C), diethylene glycol butyl methyl ether (215°C), tripropylene glycol dimethyl ether (215°C), 1,3-dimethyl-2-imidazolidinone (225°C), diethylene glycol monobutyl ether (230°C), catechol (245°C), triethylene glycol monomethyl ether (249°C), 1,6-hexanediol (250°C), diethylene glycol dibutyl ether (256°C), triethylene glycol butyl methyl ether (261°C), tetraethylene glycol dimethyl ether (275°C), triethylene glycol (285°C), dimethyl phthalate (284°C), 1,9-nonanediol (288°C), adiponitrile (295°C), tetraethylene glycol (314°C), triethanolamine (335.4°C), tricresyl phosphate (410°C), °C), polyethylene glycol monomethyl ether 350 (>350°C), polyethylene glycol monomethyl ether 450 (>350°C), polyethylene glycol monomethyl ether 550 (>350°C), polyethylene glycol monomethyl ether 750 (>350°C), polyethylene glycol 200 (over 300°C and up to 350°C), polyethylene glycol 300 (>350°C), polyethylene glycol 400 (>350°C), polyethylene glycol 500 (>350°C), polyethylene glycol 600 (>350°C), polyethylene glycol 800 (>200°C → >350°C), polyethylene glycol 1000 (boiling point >350°C), polyethylene glycol 1200 (boiling point >350°C), polyethylene glycol 2000 (boiling point >350°C), polyethylene glycol 3000 (boiling point >350°C) etc. (The boiling point of each substance is shown in parentheses).

[0062] The modifier is preferably one having a polyethylene glycol structure, such as triethylene glycol monomethyl ether, triethylene glycol butyl methyl ether, tetraethylene glycol dimethyl ether, triethylene glycol, tetraethylene glycol, polyethylene glycol monomethyl ether (preferably polyethylene glycol monomethyl ether 350, polyethylene glycol monomethyl ether 450, polyethylene glycol monomethyl ether 550, polyethylene glycol monomethyl ether 750), or polyethylene glycol (preferably polyethylene glycol 200, polyethylene glycol 300, polyethylene glycol 400, polyethylene glycol 500, polyethylene glycol 600, or polyethylene glycol 800), more preferably polyethylene glycol monomethyl ether and / or polyethylene glycol, and particularly preferably polyethylene glycol monomethyl ether 350, polyethylene glycol monomethyl ether 450, polyethylene glycol monomethyl ether 550, polyethylene glycol monomethyl ether 750, polyethylene glycol 200, polyethylene glycol 300, polyethylene glycol 400, polyethylene glycol 500, polyethylene glycol 600, or polyethylene glycol 800.

[0063] According to one embodiment, the modifier is a compound having a polyethylene glycol structure. When the modifier has a polyethylene glycol structure, the amount of carbon dioxide adsorption and desorption can be further increased in a solid absorbent supported with a carbon dioxide separation composition. The number-average molecular weight of the compound having a polyethylene glycol structure used as a modifier is preferably 200 to 3,000, more preferably 200 to 2,500, even more preferably 200 to 2,000, even more preferably 200 to 1,500, particularly preferably 280 to 1,200, and most preferably 300 to 1,000. According to one embodiment, the number-average molecular weight of the compound having a polyethylene glycol structure used as a modifier is 200 to 1,000, 300 to 800, 300 to 700, 300 to 600, or 200 to 600. When the number-average molecular weight of the compound having a polyethylene glycol structure is within the above range, the oligoamine compound can be more effectively supported on the carrier, and the amount of carbon dioxide adsorption and desorption can be further increased in a solid absorbent supported with a carbon dioxide separation composition.

[0064] The number average molecular weight of a compound having a polyethylene glycol structure can be measured by boiling point elevation method using an ebullometer or the like. In the boiling point elevation method, a fixed amount of solvent is sampled and the boiling point is measured; then, a trace amount of solute is dissolved in the solvent, and the boiling point of the solution is measured and calculated using the following formula. This makes it possible to determine the molar mass of the solute, and when the solute is a compound having a polyethylene glycol structure, this molar mass can be used as the number average molecular weight. As the solvent, methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, ethylene glycol monomethyl ether, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, etc. can be used.

[0065] According to one embodiment, the carbon dioxide separation composition according to this embodiment includes polyethyleneimine as the oligoamine compound and a compound having a polyethylene glycol structure as the modifier. This allows the oligoamine compound to be more effectively supported on the carrier, thereby further increasing the amount of carbon dioxide adsorption and desorption in a solid absorbent supported with the carbon dioxide separation composition. Furthermore, according to one embodiment, the carbon dioxide separation composition according to this embodiment includes polyethyleneimine having a number-average molecular weight of 200 or more but less than 2,000 (preferably 200-1,000) as the oligoamine compound, and a compound having a polyethylene glycol structure and having a number-average molecular weight of 200 or more but less than 3,000 (preferably 200-1,000) as the modifier. This allows for better support of the oligoamine compound on the carrier, thereby further increasing the amount of carbon dioxide adsorption and desorption in a solid absorbent supported with the carbon dioxide separation composition.

[0066] Another specific example of the modifier is an ionic liquid. The ionic liquid is not particularly limited, and may be, for example, a combination of a cation such as an imidazolium ion, a pyridinium ion, a pyrrolidinium ion, a piperidinium ion, an ammonium ion, or a phosphonium ion with an anion such as a halide ion, tetrafluoroborate, hexafluorophosphate, or bis(trifluoromethylsulfonyl)amide. Due to their high affinity with oligoamine compounds, preferred are combinations of cations having a relatively small organic group and less than 13 carbon atoms, such as dialkylimidazolium ions, alkylpyridinium ions, tetraalkylammonium ions, or tetraalkylphosphonium ions, with anions such as carboxylate anions such as lactate ions, trifluoromethanesulfonate ions, or methanesulfonate ions.

[0067] The modifier may be used alone or in combination of two or more kinds.

[0068] The content of the modifier is preferably 1 wt% to 80 wt%, more preferably 5 wt% to 75 wt%, and even more preferably 10 wt% to 70 wt%, based on the total weight of the non-volatile content of the carbon dioxide separation composition. According to one embodiment, the content of the modifier is 5 wt% to 70 wt%, 15 wt% to 70 wt%, 15 wt% to 65 wt%, 15 wt% to 60 wt%, 20 wt% to 70 wt%, 20 wt% to 65 wt%, or 20 wt% to 60 wt%, based on the total weight of the non-volatile content of the carbon dioxide separation composition. By containing the modifier in the above range, the amount of carbon dioxide adsorption and desorption can be further increased in a solid absorbent material supporting the carbon dioxide separation composition. The non-volatile content of the carbon dioxide separation composition is the non-volatile content when dried at 120 ° C for 6 hours.

[0069] According to one embodiment, the content of the modifier is preferably 6 wt% to 70 wt%, more preferably 8 wt% to 65 wt%, and even more preferably 10 wt% to 60 wt%, based on the total weight of the non-volatile content of the carbon dioxide separation composition. According to one embodiment, the content of the modifier is 20 wt% to 50 wt%, 30 wt% to 60 wt%, 40 wt% to 60 wt%, or 20 wt% to 40 wt%, based on the total weight of the non-volatile content of the carbon dioxide separation composition.

[0070] <Water> The carbon dioxide separation composition according to this embodiment preferably contains water. When the carbon dioxide separation composition contains water, mixing and / or dissolution of the oligoamine compound and the modifier can be facilitated, and precipitation of carbamic acid (salt) of the oligoamine compound that occurs when carbon dioxide is absorbed can be suppressed.

[0071] The water content is not limited as long as the carbon dioxide absorption performance is maintained. The water content contained in the carbon dioxide separation composition is preferably 1 wt % to 30 wt %, more preferably 1.5 wt % to 29 wt %, even more preferably 2 wt % to 28 wt %, particularly preferably 2.5 wt % to 27 wt %, and most preferably 3 wt % to 26 wt %, relative to the total weight of the carbon dioxide separation composition. According to one embodiment, the water content contained in the carbon dioxide separation composition is 0.1 wt % to 5 wt %, 0.1 wt % to 10 wt %, 1 wt % to 20 wt %, 0.1 wt % to 25 wt %, 0.1 wt % to 20 wt %, 0.1 wt % to 30 wt %, 0.5 wt % to 10 wt %, 0.5 wt % to 20 wt %, 0.5 wt % to 25 wt %, 0.5 wt % to 25 wt %, 0.5 wt % to 50 ... The water content is preferably 0.5% to 20% by weight, 0.5% to 30% by weight, 1% to 20% by weight, 1% to 15% by weight, 1% to 10% by weight, 1% to 5% by weight, 5% to 30% by weight, 5% to 25% by weight, 5% to 20% by weight, 5% to 15% by weight, 5% to 10% by weight, 8% to 30% by weight, 8% to 25% by weight, 8% to 20% by weight, or 8% to 15% by weight. When the water content is within the above range, mixing and / or dissolution of the oligoamine compound and the modifier is facilitated, and precipitation of carbamic acid (salt) of the oligoamine compound that occurs when carbon dioxide is absorbed can be suppressed.

[0072] <Solvents Other Than Water> The carbon dioxide separation composition may further contain a solvent other than water. This can be expected to have the effect of facilitating the mixing and / or dissolution of the oligoamine compound and the modifier. The solvent other than water is a component that has a molecular weight of less than 500 and is liquid at room temperature (25°C), excluding the oligoamine compound, the modifier, and water. Examples of solvents other than water include methanol, ethanol, isopropanol, butanol, acetone, methyl ethyl ketone, acetonitrile, N,N-dimethylformamide, dimethyl sulfoxide, ethylene glycol, methyl cellosolve (ethylene glycol monomethyl ether), and tetrahydrofuran. The above solvents other than water may be used alone or in combination of two or more. Of these, acetonitrile, N,N-dimethylformamide, dimethyl sulfoxide, and ethylene glycol are preferably used as solvents other than water, with acetonitrile being more preferred.

[0073] The content of the solvent other than water in the carbon dioxide separation composition is not limited as long as the carbon dioxide absorption performance is maintained, but is preferably 0.01% by weight to 20% by weight, more preferably 0.01% by weight to 10% by weight, and even more preferably 0.01% by weight to 5% by weight, relative to the total weight of the carbon dioxide separation composition. According to one embodiment, the content of the solvent other than water in the carbon dioxide separation composition is 0.01% by weight to 3% by weight, 0.01% by weight to 2% by weight, or 0.01% by weight to 1% by weight, relative to the total weight of the carbon dioxide separation composition.

[0074] <Other Components> The carbon dioxide separation composition may further contain components (optional components) other than the oligoamine compound and the modifier, as long as the effects of the present invention are obtained. The content of such optional components and their content ratios can be appropriately selected depending on the purpose, etc.

[0075] Optional components that can be selected depending on the purpose include, for example, surfactants, antioxidants, and crystallization inhibitors.

[0076] The surfactant may be a nonionic surfactant, anionic surfactant, cationic surfactant, or amphoteric surfactant, and the HLB (hydrophilic-lipophilic balance) of the surfactant may be 10 or more, preferably 12 or more, and more preferably 15 or more (the upper limit is, for example, 20 or less).

[0077] As the antioxidant, a radical scavenger, a peroxide decomposer, or a metal deactivator can be used. As the radical scavenger, a phenol-based antioxidant or an amine-based antioxidant can be used, and an amine-based antioxidant is preferred. As the peroxide decomposer, there is no particular limitation as long as it can effectively decompose peroxides, and sulfur-based antioxidants and phosphorus-based antioxidants can be used. As the metal deactivator, there is no particular limitation as long as it can effectively chelate with transition metals such as copper, iron, chromium, and nickel, and ethylenediaminetetraacetic acid (EDTA) is effectively used.

[0078] Examples of the crystallization inhibitor include water-soluble polymers such as polyvinylpyrrolidone, polyvinyl alcohol, hydroxyethyl cellulose, etc. By using a water-soluble polymer as a crystallization inhibitor, it is possible to suppress the formation of an insoluble salt due to a secondary interaction between the oligoamine compound and a carbamic acid (salt) generated by the reaction between the oligoamine compound and carbon dioxide.

[0079] The optional components may be contained within a range that does not impair the performance of the carbon dioxide separation composition. For example, the optional components are contained in an amount of preferably 0.01% by weight to 30% by weight, more preferably 0.1% by weight to 20% by weight, and even more preferably 0.5% by weight to 10% by weight, relative to the carbon dioxide separation composition.

[0080] The optional components may be used singly or in combination of two or more.

[0081] <Preparation Method> The carbon dioxide separation composition can be prepared by mixing a raw material oligoamine compound (raw material oligoamine compound), a modifier, and optional components under temperature conditions that allow a liquid mixture to be obtained, for example, at a temperature of 20° C. to 100° C. According to one embodiment, the carbon dioxide separation composition can be prepared by mixing a raw material oligoamine compound, a modifier, water, and optional components under temperature conditions of 20° C. to 100° C.

[0082] In this case, an oligoamine compound having a carbamic acid (salt) structure in advance may be used as a raw material. The oligoamine compound may be a raw material not having a carbamic acid (salt) structure. During the preparation of the carbon dioxide separation composition, for example, during the preparation of an impregnation solution containing the raw oligoamine compound, a modifier, and, if necessary, water and optional components, the raw oligoamine compound may be contacted with carbon dioxide to convert some of the nitrogen atoms to a carbamic acid (salt) structure. In this case, the impregnation solution containing the raw oligoamine compound, a modifier, water, and optional components may be impregnated into a hydrophilic silica gel described below, and then the impregnation solution may be contacted with carbon dioxide during evaporation of the water content of the impregnation solution retained in the pores, thereby converting some of the nitrogen atoms to a carbamic acid (salt) structure. The contact conditions between the raw oligoamine compound and carbon dioxide are as described above.

[0083] According to one embodiment, the carbon dioxide separation composition is prepared by preparing an impregnation liquid containing an oligoamine compound (raw material oligoamine compound), a modifier, water, and an optional component under a temperature condition of 20°C to 100°C, causing the impregnation liquid to be supported on a carrier, and drying the carrier impregnated with the impregnation liquid, thereby preparing a carrier (solid absorbent) supported with the carbon dioxide separation composition.

[0084] <B. Solid absorbent for carbon dioxide separation> The carbon dioxide separation composition described in Section A can be applied to a solid absorbent for carbon dioxide separation for separating carbon dioxide from a gas containing carbon dioxide. The carbon dioxide separation composition according to this embodiment can be used by being supported on a carrier. That is, the present invention also provides a solid absorbent for carbon dioxide separation in which the carbon dioxide separation composition according to this embodiment is supported on a porous material (e.g., hydrophilic silica gel). The solid absorbent for carbon dioxide separation comprises a porous material (e.g., hydrophilic silica gel) and the carbon dioxide separation composition supported on the hydrophilic silica gel.

[0085] <Porous Material> A porous material is preferred as the carrier. Silica gel (hydrophilic silica gel and hydrophobic silica gel) is preferred as the porous material, with hydrophilic silica gel being more preferred. Any hydrophilic silica gel can be used as the hydrophilic silica gel. Hydrophilic silica gel has pores classified into micropores, mesopores, and macropores. The inner surface of the hydrophilic silica gel can effectively retain the carbon dioxide separation composition according to this embodiment and water. Furthermore, from the viewpoint of versatility, it is preferable to use hydrophilic silica gel produced by a gel method. Hydrophilic silica gel is generally obtained by drying and pulverizing silica gel synthesized from sodium silicate and mineral acid as raw materials. For example, commercially available products such as MIZUKASIL (registered trademark) manufactured by Mizusawa Industrial Chemicals and SYLYSIA (registered trademark) manufactured by Fuji Silysia Chemical Ltd. can be used. Furthermore, the hydrophilic silica gel can be formed into a desired shape using a binder or the like.

[0086] The pore volume of the porous material (e.g., hydrophilic silica gel) is preferably 0.6 cm ３ / g to 3.0 cm ３ / g, more preferably 0.7 cm ３ / g ~ 2.5cm ３ / g, and more preferably 0.8 cm ３ / g to 2.0 cm ３ / g, and particularly preferably 0.9 cm ３ / g to 2.0 cm ３ / g, and most preferably 1.0 cm３ / g ~ 1.8cm ３ / g.

[0087] If the pore volume of the porous material (e.g., hydrophilic silica gel) is within the above range, it can support a sufficient amount of the carbon dioxide separation composition to exhibit its performance, and the mechanical strength of the porous material (e.g., hydrophilic silica gel) can also be sufficiently ensured.

[0088] The average pore diameter of the porous material (e.g., hydrophilic silica gel) is preferably 5 nm to 80 nm, more preferably 10 nm to 60 nm, even more preferably 12 nm to 55 nm, particularly preferably 12 nm to 50 nm, and most preferably 15 nm to 40 nm.

[0089] The specific surface area of ​​the porous material (e.g., hydrophilic silica gel) is preferably 70 m ２ / g~800m ２ / g, more preferably 80m ２ / g~650m ２ / g, and more preferably 100m ２ / g~500m ２ / g, and particularly preferably 100m ２ / g~450m ２ / g, and most preferably 100m ２ / g~400m ２ / g.

[0090] The bulk density of the porous material (e.g., hydrophilic silica gel) is preferably 0.10 g / cm ３ 0.7g / cm or more ３ or less, more preferably 0.15 g / cm ３ 0.6g / cm or more ３ More preferably, it is 0.20 g / cm or less. ３ 0.5g / cm or more ３ The inner surfaces of the pores of the porous material (e.g., hydrophilic silica gel) are preferably hydrophilic. In this specification, the water adsorption amount per unit surface area calculated by the following method is 0.00002 g / m or less. ２For example, a porous material having a water adsorption amount per unit surface area of ​​0.00002 g / m or more calculated by the following method is defined as a hydrophilic porous material. ２ The silica gel having the above properties is called hydrophilic silica gel.

[0091] <Evaluation of hydrophilicity of pore inner surface: measurement of moisture adsorption amount in low-humidity nitrogen> Using a TG-DTA (TG-DTA8120, 8122 manufactured by Rigaku Corporation), the humidity of the supply gas is measured at an absolute humidity of 1 g / kg. A porous material is heated to 130°C and dried, and then cooled to 40°C, and its weight increase is measured.

[0092] The weight of the porous material when water is adsorbed and the weight of the porous material when dry are measured by TG-DTA, and the amount of water adsorbed per unit surface area is calculated using the following formula.

[0093] [Evaluation of hydrophilicity of pore inner surface] Water adsorption amount per unit surface area (g / m ２ ) = ((weight of porous material when moisture is adsorbed (mg) - weight of porous material when dry (mg)) ÷ weight of porous material when dry (mg)) ÷ specific surface area of ​​porous material (m ２ / g).

[0094] According to one embodiment, in the solid absorbent for separating carbon dioxide, the physical properties of the hydrophilic silica gel satisfy one or more selected from the group consisting of the following (i) to (iv): (i) a pore volume of 0.6 cm ３ / g to 3.0 cm ３ / g; (ii) an average pore diameter of 5 nm to 80 nm; (iii) a specific surface area of ​​70 m ２ / g~800m ２ / g; (iv) a bulk density of 0.10 g / cm ３ That's all.

[0095] When the hydrophilic silica gel satisfies one or more of the above (i) to (iv), the amount of carbon dioxide adsorption and desorption can be further increased in the solid absorbent material carrying the carbon dioxide separation composition.

[0096] The shape of hydrophilic silica gel can be selected as desired to suit the adsorption / desorption system. Powder is preferred when used as a fluidized bed, spherical when used as a mobile phase, pellet or ring shape when used as a stationary phase, and molded bodies processed into honeycomb or filter shapes that enable low pressure loss are preferred for stationary phases that require particularly large air volumes.

[0097] The amount of nonvolatile content of the carbon dioxide separation composition supported on the porous material (e.g., hydrophilic silica gel) is not limited as long as the effects of the present invention are obtained, and is, for example, 20% by weight to 80% by weight, preferably 25% by weight to 75% by weight, more preferably 30% by weight to 70% by weight, even more preferably 35% by weight to 65% by weight, particularly preferably 35% to 60% by weight, and most preferably 35% to 58% by weight, relative to the total weight of the nonvolatile content of the solid absorbent for carbon dioxide separation. The amount of nonvolatile content of the carbon dioxide separation composition supported on the hydrophilic silica gel can be calculated by the following method.

[0098] <Calculation of the amount of non-volatile content of the carbon dioxide separation composition supported on the porous material by thermogravimetry> To determine the amount of non-volatile content of the carbon dioxide separation composition, a TG-DTA (TG-DTA8120, 8122 manufactured by Rigaku Corporation) is used, and compressed air is supplied into the TG-DTA oven at 200 ml / min using a mass flow controller, to perform thermogravimetry.

[0099] The solid absorbent is treated by thermogravimetry at 120°C for 1 hour, and the weight of the non-volatile content of the solid absorbent in a state where carbon dioxide and water have been completely desorbed is measured to determine the total weight of the non-volatile content of the carbon dioxide separation composition and the porous material. The solid absorbent is treated at 500°C for 1 hour, and the weight of the non-volatile content of the solid absorbent in a state where the organic components have been completely oxidatively decomposed is measured to determine the weight of the non-volatile content of the porous material.

[0100] Non-volatile content ratio (parts by weight) of carbon dioxide separation composition = (total non-volatile weight (g) of carbon dioxide separation composition and porous material - non-volatile weight (g) of porous material) ÷ ​​total non-volatile weight (g) of carbon dioxide separation composition and porous material × 100.

[0101] The water content in the solid absorbent for carbon dioxide separation is not limited as long as the carbon dioxide absorption performance is maintained. The water content contained in the solid absorbent for carbon dioxide separation is preferably 0.1 wt% to 20 wt%, more preferably 0.2 wt% to 18 wt%, even more preferably 0.5 wt% to 15 wt%, particularly preferably 1 wt% to 12 wt%, and most preferably 4 wt% to 12 wt%, based on the total weight of the solid absorbent for carbon dioxide separation. According to one embodiment, the water content contained in the solid absorbent for carbon dioxide separation is 0.1 wt% to 5 wt%, 0.1 wt% to 10 wt%, 1 wt% to 10 wt%, 1 wt% to 20 wt%, 2 wt% to 15 wt%, 3 wt% to 15 wt%, or 3 wt% to 12 wt%, based on the total weight of the solid absorbent for carbon dioxide separation. When the water content is within the above range, mixing and / or dissolution of the oligoamine compound and the modifier can be facilitated, and precipitation of carbamic acid (salt) of the oligoamine compound that occurs when carbon dioxide is absorbed can be suppressed.

[0102] <Method of driving solid absorbent for carbon dioxide separation> The method of carbon dioxide adsorption / desorption of the solid absorbent for carbon dioxide separation is not particularly limited, but examples include a method using temperature swing, a method using pressure swing, a method using reduced pressure regeneration, a method using steam regeneration, and a method using a combination of these.

[0103] As an example, a solid absorbent for carbon dioxide separation absorbs carbon dioxide by contacting it with a feed gas containing carbon dioxide at 0°C to 80°C. The treated gas is discharged, and then the evaporated carbon dioxide is recovered by heating it to 60°C to 120°C. Carbon dioxide can be separated and recovered by switching the flow paths for the feed gas and the recovered gas during operation.

[0104] As an example, a solid absorbent for carbon dioxide separation absorbs carbon dioxide by contacting it under pressure with a feed gas containing carbon dioxide at 0°C to 80°C. After the treated gas is discharged, the carbon dioxide that is released is recovered by heating it to 60°C to 120°C. Carbon dioxide can be separated and recovered by switching the flow paths for the feed gas and the recovered gas during operation.

[0105] As an example, a solid absorbent material for carbon dioxide separation absorbs carbon dioxide by contacting it with a feed gas containing carbon dioxide at 0°C to 80°C, and recovers the carbon dioxide that is released by reducing the pressure to 1 kPa to 20 kPa at 40°C to 80°C. Carbon dioxide can be separated and recovered by switching the flow paths for the feed gas and the recovered gas during operation.

[0106] As an example, a solid absorbent material for carbon dioxide separation absorbs carbon dioxide by contacting it with a supply gas containing carbon dioxide at 0°C to 80°C, and recovers the carbon dioxide that is released by supplying steam at 20 kPa to 100 kPa at 60°C to 100°C. Carbon dioxide can be separated and recovered by switching the flow paths for the supply gas and the recovered gas during operation.

[0107] In a carbon dioxide adsorption / desorption test of the solid absorbent for carbon dioxide separation using air with a carbon dioxide concentration of 300 ppm by volume to 500 ppm by volume (e.g., 400 ppm by volume) and an absolute humidity of 2 g / kg or less (e.g., 1 g / kg or more and 2 g / kg or less), the solid absorbent has the ability to release carbon dioxide absorbed at 40°C at 70°C in an amount of carbon dioxide adsorbed / desorbed per gram of solid absorbent of 0.90 mmol or more (preferably 1.0 mol or more, more preferably 1.1 mol or more), and an amount of carbon dioxide adsorbed / desorbed per mole of amine contained in the solid absorbent of 0.20 mol or more (preferably 0.21 mol or more, more preferably 0.22 mol or more).

[0108] In a carbon dioxide adsorption / desorption test of the solid absorbent for carbon dioxide separation using air with a carbon dioxide concentration of 9000 ppm by volume to 11000 ppm by volume (e.g., 10000 ppm by volume) and an absolute humidity of 2 g / kg or less (e.g., 1 g / kg or more and 2 g / kg or less), the performance of the solid absorbent at 70 ° C. to release carbon dioxide absorbed at 100 ° C. is 1.30 mmol or more (preferably 1.40 mol or more, more preferably 1.50 mol or more) per gram of solid absorbent, and the carbon dioxide adsorption / desorption amount per mole of amine contained in the solid absorbent is 0.20 mol or more (preferably 0.22 mol or more, more preferably 0.24 mol or more). These adsorption / desorption tests can be performed using the following method.

[0109] <Carbon dioxide adsorption / desorption test using carbon dioxide-containing gas simulating dry air> To measure the amount of carbon dioxide absorbed and desorbed, a TG-DTA (TG-DTA8120, 8122 manufactured by Rigaku Corporation) was used to measure the weight at the absorption temperature (40°C) and the desorption temperature (70°C). A mass flow controller was used to adjust the flow rates of nitrogen and carbon dioxide, and the carbon dioxide-containing gas was supplied into the TG-DTA oven at 200 ml / min. The carbon dioxide concentration of the simulated gas was approximately 400 ppm by volume, and the humidity of the supplied gas was kept constant at an absolute humidity of 2 g / kg.

[0110] The weight of the solid absorbent when absorbing carbon dioxide at each temperature and the weight of the solid absorbent when desorbing carbon dioxide by heating are measured by TG-DTA, and the carbon dioxide adsorption / desorption amount and amine efficiency are calculated using the following formula.

[0111] [Carbon dioxide adsorption / desorption amount] Carbon dioxide adsorption / desorption amount (mmol / g) = (weight (g) of solid absorbent after carbon dioxide absorption - weight (g) of solid absorbent after carbon dioxide desorption) ÷ molecular weight of carbon dioxide (g / mmol) ÷ weight of solid absorbent (g) [Amine efficiency] Amine efficiency (mol / mol) = carbon dioxide adsorption / desorption amount (mmol / g) / number of amine moles per gram of solid absorbent (mmol / g).

[0112] <Carbon dioxide adsorption / desorption test using carbon dioxide-containing gas simulating a dry closed space> To measure the amount of carbon dioxide absorbed and desorbed, a TG-DTA (TG-DTA8120, 8122 manufactured by Rigaku Corporation) was used to measure the weight at the absorption temperature (70°C) and the desorption temperature (100°C). Using a mass flow controller, the supply amounts of nitrogen and carbon dioxide were adjusted so that the carbon dioxide concentration was approximately 10,000 ppm by volume, and the gases were supplied into the TG-DTA oven at a total flow rate of 200 ml / min. The humidity of the supplied gas was kept constant at an absolute humidity of 2 g / kg.

[0113] From the TG-DTA measurement, the weight of the solid absorbent material when absorbing carbon dioxide at each temperature and the weight of the solid absorbent material when desorbing carbon dioxide by heating are measured, and the amount of carbon dioxide adsorption and desorption is calculated in the same manner as in a carbon dioxide adsorption / desorption test using a carbon dioxide-containing gas that simulates dry air.

[0114] According to one embodiment, the solid absorbent for separating carbon dioxide satisfies one or more selected from the group consisting of the following (i) and (ii): (i) in a carbon dioxide adsorption / desorption test using air having a carbon dioxide concentration of 300 ppm by volume to 500 ppm by volume (for example, 400 ppm by volume) and an absolute humidity of 2 g / kg or less, in a step of releasing carbon dioxide absorbed by the solid absorbent at 40°C at 70°C, the amount of carbon dioxide adsorbed and desorbed per gram of the solid absorbent is 0.9 mmol or more, and the amount of carbon dioxide adsorbed and desorbed per mole of amine contained in the solid absorbent is 0.2 mol or more; (ii) In a carbon dioxide adsorption / desorption test using air having a carbon dioxide concentration of 9,000 ppm by volume to 11,000 ppm by volume (for example, 10,000 ppm by volume) and an absolute humidity of 2 g / kg or less, in a step in which the solid absorbent material releases carbon dioxide absorbed at 70°C at 100°C, the amount of carbon dioxide adsorbed and desorbed per gram of the solid absorbent is 1.3 mmol or more, and the amount of carbon dioxide adsorbed and desorbed per mole of amine contained in the solid absorbent is 0.2 mol or more.

[0115] When the solid absorbent for carbon dioxide separation satisfies one or more selected from the group consisting of (i) and (ii) above, the amount of carbon dioxide adsorption and desorption can be further increased in the solid absorbent carrying the carbon dioxide separation composition.

[0116] <C. Method for producing a solid absorbent for carbon dioxide separation> The solid absorbent for carbon dioxide separation described in Section B can be obtained by fixing the carbon dioxide separating composition in the pores of the silica gel through the following steps: (1) a first step of preparing an impregnation liquid containing an oligoamine compound having a boiling point of 200°C or higher, a modifier having a boiling point of 200°C or higher, and water; (2) a second step of impregnating a hydrophilic silica gel with the impregnation liquid; (3) a third step of separating the hydrophilic silica gel impregnated with the impregnation liquid from excess impregnation liquid; and (4) a fourth step of drying the hydrophilic silica gel impregnated with the impregnation liquid by evaporating water in an atmosphere containing carbon dioxide.

[0117] By using the method described above to support a carbon dioxide separation composition on hydrophilic silica gel, it is possible to distribute the oligoamine component evenly among the micropores and mesopores within the pores of the hydrophilic silica gel, while maintaining the macropores necessary for gas diffusion, thereby creating a solid absorbent material with a high carbon dioxide adsorption / desorption capacity per mole of amine.

[0118] In another example of a method for producing a solid absorbent for carbon dioxide separation, a mixture containing an oligoamine compound having a boiling point of 200°C or higher and a modifier having a boiling point of 200°C or higher may be prepared, then diluted with water to form an impregnation liquid, which is then impregnated into a porous material (hydrophilic silica gel), and the water may be evaporated to form a carbon dioxide separation composition in the pores of the hydrophilic silica gel.In yet another example, all of the components may be mixed together to prepare an impregnation liquid, which is then impregnated into the hydrophilic silica gel, and the water may be evaporated to form carbon dioxide absorption sites in the pores of the hydrophilic silica gel.

[0119] (1) First step of preparing an impregnation liquid containing an oligoamine compound having a boiling point of 200°C or higher, a modifier having a boiling point of 200°C or higher, and water <Oligoamine compound, modifier> The oligoamine compound (raw material oligoamine compound) and / or the modifier can be those described in <A. Composition for carbon dioxide separation>.

[0120] <Water> In the step of preparing the impregnation solution, water is used as a solvent from the viewpoints of viscosity reduction effect and safety. The amount of water added is preferably 0.1 to 9 times the total weight of the oligoamine compound and the modifier. The amount of water added is more preferably 0.2 to 7 times, even more preferably 0.3 to 5 times, and most preferably 0.4 to 4 times the total weight of the oligoamine compound and the modifier. Using water as a solvent during the production of a solid absorbent for carbon dioxide separation improves the hydrophilicity of the carbon dioxide separation composition, allowing the carbon dioxide separation composition to be effectively supported in the micropores and mesopores of the hydrophilic silica gel. Furthermore, using water as a solvent during the production of a solid absorbent for carbon dioxide separation allows water to remain in the supported carbon dioxide separation composition, thereby suppressing the precipitation of carbamates from the oligoamine compound when carbon dioxide is absorbed.

[0121] <Solvent other than water> The impregnation liquid may contain a solvent other than water. By using a solvent other than water, the solubility and viscosity of the carbon dioxide separation composition can be adjusted.

[0122] The solvent other than water can be any solvent that is miscible with water, the starting oligoamine compound, and the modifier, and for example, the solvents other than water that can be contained in the carbon dioxide separation composition described above can be similarly applied. As the solvent other than water, acetonitrile, ethylene glycol, N,N-dimethylformamide, and dimethyl sulfoxide are preferably used, and acetonitrile is more preferred because of its ease of miscibility with the oligoamine compound, the modifier, and / or water, and its ease of removal in a subsequent process.

[0123] Two or more solvents other than water may be used in combination, and the oligoamine compound, modifier, and water may be mixed in any order.

[0124] The content of the solvent other than water is preferably 1 to 200 parts by weight, more preferably 10 to 100 parts by weight, per 100 parts by weight of water.

[0125] The oligoamine compound used to prepare the impregnation solution may contain a carbamic acid (salt) structure. When an oligoamine compound not containing a carbamic acid (salt) structure is used as a raw material, the oligoamine compound can be converted into an oligoamine compound having a carbamic acid (salt) structure by the fourth step (4) described below. Alternatively, when an oligoamine compound not containing a carbamic acid (salt) structure is used as a raw material, the oligoamine compound may be brought into contact with a gas containing carbon dioxide in the step of preparing the impregnation solution to form a carbamic acid (salt) structure.

[0126] (2) Second step of impregnating hydrophilic silica gel with impregnation solution Any known method, such as immersion, impregnation, or liquid passage, can be used to impregnate the pores of the hydrophilic silica gel with the impregnation solution prepared in the first step of (1).

[0127] Specifically, the hydrophilic silica gel may be immersed in the impregnation liquid prepared in the first step of (1), or the impregnation liquid may be added dropwise to the hydrophilic silica gel, or the hydrophilic silica gel may be filled in a container such as a column and then the impregnation liquid may be passed through the column to impregnate the hydrophilic silica gel.

[0128] In this case, it is preferable to employ the immersion method from the viewpoint of ease of operation and equipment.

[0129] The pressure during the treatment can be selected from normal pressure and reduced pressure. Treatment under reduced pressure is preferred to remove air bubbles from the pores of the hydrophilic silica gel and efficiently penetrate the impregnation liquid. Specific treatment pressures are preferably −0.08 MPaG to −0.004 MPaG, more preferably −0.07 MPaG to −0.01 MPaG, and even more preferably −0.06 MPaG to −0.02 MPaG. According to one embodiment, the step of impregnating the hydrophilic silica gel with the impregnation liquid includes a step of degassing the porous pores under a reduced pressure of −0.08 MPaG to −0.004 MPaG.

[0130] The step of impregnating the hydrophilic silica gel with the impregnation solution is preferably carried out at a temperature in the range of 20° C. to 90° C. The treatment temperature is more preferably 30° C. to 80° C., and even more preferably 40° C. to 70° C.

[0131] The oligoamine compound used to prepare the impregnation solution may contain a carbamic acid (salt) structure. When an oligoamine compound not containing a carbamic acid (salt) structure is used as a raw material, the oligoamine compound can be converted into an oligoamine compound having a carbamic acid (salt) structure by the fourth step (4) described below. Alternatively, when an oligoamine compound not containing a carbamic acid (salt) structure is used as a raw material, the oligoamine compound may be contacted with a gas containing carbon dioxide in this step to form a carbamic acid (salt) structure.

[0132] (3) A third step of separating the hydrophilic silica gel impregnated with the impregnation solution from the excess impregnation solution. Any solid-liquid separation method such as filtration, decantation, centrifugation, etc. can be used for the separation. From the viewpoint of simplicity of the procedure, separation by filtration is preferred.

[0133] (4) A fourth step of drying the hydrophilic silica gel impregnated with the impregnation solution by evaporating water in an atmosphere containing carbon dioxide. Any method for drying water can be employed.

[0134] The drying temperature is preferably 30°C to 100°C, more preferably 40°C to 98°C, even more preferably 50°C to 95°C, and most preferably 50°C to 90°C.

[0135] The treatment time is preferably from 0.1 to 48 hours, more preferably from 0.2 to 24 hours, and even more preferably from 0.5 to 12 hours.

[0136] The pressure during the treatment can be selected from normal pressure and reduced pressure. It is preferable to perform the treatment at normal pressure in order to utilize the interaction between the hydrophilic silica gel and the composition and to slowly evaporate the water while maintaining the composition in the pores.

[0137] Within the above range of conditions, the carbon dioxide separation composition can be efficiently supported in the mesopores / micropores while drying the macropores, and carbon dioxide absorption sites can be efficiently produced (i.e., carbamic acid (salt) structures can be formed).

[0138] <Carbon dioxide> In the step of evaporating water, in order to allow the impregnation liquid to effectively penetrate into the micropores / mesopores in the hydrophilic silica gel, a part of the oligoamine compound is converted into a carbamic acid (salt) structure in an atmosphere containing carbon dioxide.

[0139] The treatment in an atmosphere containing carbon dioxide can be carried out by any method and under any conditions. For example, the treatment may be carried out by ventilating the atmosphere or in a sealed space. The treatment time is preferably 5 to 900 minutes, more preferably 10 to 600 minutes, and particularly preferably 15 to 300 minutes.

[0140] The carbon dioxide concentration in the carbon dioxide-containing atmosphere is preferably 0.01 vol% to 20 vol%, more preferably 0.02 vol% to 15 vol%, even more preferably 0.03 vol% to 10 vol%, and particularly preferably 0.035 vol% to 5 vol%. By setting the carbon dioxide concentration within the above range, a carbamic acid (salt) structure is efficiently produced. When a portion of the oligoamine compound has a carbamic acid (salt) structure, the affinity of the impregnation liquid with the hydrophilic silica gel surface is improved, making it easier for the impregnation liquid to penetrate into the micropores and mesopores of the hydrophilic silica gel. After evaporation of water, the carbon dioxide separation composition is retained in the micropores and mesopores, forming absorption sites. The carbon dioxide-containing atmosphere may contain nitrogen, oxygen, argon, etc. in addition to carbon dioxide.

[0141] The operation of converting a part of the amine structure into a carbamic acid (salt) structure may be carried out in the step of preparing an impregnation solution and the step of impregnating hydrophilic silica gel with the impregnation solution, in addition to the step of evaporating water.

[0142] According to one embodiment, the method for producing a solid absorbent for separating carbon dioxide satisfies one or more conditions selected from the group consisting of the following (a) to (c): (a) the second step is carried out at a temperature range of 20°C to 90°C; (b) the second step includes a step of degassing the inside of hydrophilic silica gel pores under a reduced pressure of -0.08 MPaG to -0.004 MPaG; (c) the fourth step is carried out at a temperature range of 30°C to 100°C using air as the carbon dioxide-containing atmosphere.

[0143] By producing a solid absorbent for carbon dioxide separation by a production method that satisfies one or more of the above (a) to (c), it is possible to further increase the amount of carbon dioxide adsorption and desorption in the solid absorbent that supports the carbon dioxide separation composition.

[0144] The present invention will be specifically described below using examples, but the present invention is not limited to these examples. Unless otherwise specified, "parts" means "parts by weight" and "%" means "% by weight." Unless otherwise specified, each operation is carried out at room temperature (25°C).

[0145] The oligoamine compounds used in the following examples and comparative examples are as follows: Polyethyleneimine (Mn=600): "Epomin (registered trademark) SP-006" manufactured by Nippon Shokubai Co., Ltd. (containing 35% primary amino groups (primary amine structures) among all amines) Polyethyleneimine (Mn=300): "Epomin (registered trademark) SP-003" manufactured by Nippon Shokubai Co., Ltd. (containing 45% primary amino groups (primary amine structures) among all amines).

[0146] The modifiers used in the following examples and comparative examples are as follows: PEG200 (Mn=200): Polyethylene glycol 200 manufactured by Fujifilm Wako Pure Chemical Industries, Ltd. (ΔD: 16.73, ΔP: 9.02, ΔH: 14.58 / boiling point greater than 300°C and equal to or less than 350°C) PEG300 (Mn=300): Polyethylene glycol 300 manufactured by Fujifilm Wako Pure Chemical Industries, Ltd. (ΔD: 16.24, ΔP: 8.15, ΔH: 11.8 / boiling point greater than 350°C) PEG400 (Mn=400): Polyethylene glycol 400 manufactured by Tokyo Chemical Industry Co., Ltd. (ΔD: 15.73, ΔP: 7.47, ΔH: 9.68 / boiling point greater than 350°C) MePEG450 (Mn=450): Tokyo Chemical Industry Co., Ltd. Polyethylene glycol monomethyl ether 450 (ΔD: 15.73, ΔP: 6.26, ΔH: 8.84 / boiling point > 350°C).

[0147] The porous materials used in the following examples and comparative examples are as follows:

[0148] As a comparative porous material, regular mesoporous silica precisely synthesized using tetraalkoxysilane and a template compound was used: SBA-15 (particle size 150 μm or less): mesoporous silica manufactured by Aldrich Chemicals.

[0149] The porous materials used in the comparative examples and examples were the following commercially available hydrophilic silica gels, which were classified or crushed. Q-10 (particle size range 75-212 μm): Cariact® Q-10 (particle size range 75-500 μm) manufactured by Fuji Silysia Chemical Ltd. was classified and used. Q-30CR (particle size 53-212 μm): Cariact® Q-30 (particle size range 1.18-2.36 mm) manufactured by Fuji Silysia Chemical Ltd. was crushed and classified and used. Q-50CR (particle size range 53-212 μm): Cariact® Q-50 (particle size range 1.18-2.36 mm) manufactured by Fuji Silysia Chemical Ltd. was crushed and classified and used.

[0150] The following commercially available hydrophilic silica gels were used as porous materials in the comparative examples and examples: P-78F (average particle size 18 μm): MIZUKASIL® P-78F manufactured by Mizusawa Chemical Industries, Ltd. Q-15 (particle size range 180-500 μm): CARIACT® Q-15 manufactured by Fuji Silysia Ltd. Q-30 (particle size range 75-500 μm): CARIACT® Q-30 manufactured by Fuji Silysia Ltd.

[0151] Table 1 shows the properties of the porous materials used in the comparative examples and examples.

[0152]

[0153] The values ​​in Table 1 above were catalog values, and values ​​that were not published were measured. For Q-10, Q-30CR, and Q-50CR, the pore volume, average pore diameter, and specific surface area were measured using a BELSORP MAX manufactured by Microtrackbell, and it was confirmed that the pore volume, average pore diameter, and specific surface area were unchanged from the silica gel before classification, or crushing and classification. For P-78, Q-15, and Q-30, the catalog values ​​were used for the pore volume, average pore diameter, and specific surface area.

[0154] The pore volume, average pore diameter, and specific surface area of ​​SBA-15 were measured using a BELSORP MAX manufactured by Microtrackbell. The bulk density of each silica gel was calculated by filling a certain weight of porous material into a measuring cylinder and measuring the volume in accordance with JIS R 1628-1997. The particle size range of each silica gel was recorded as the mesh size of the sieve used for classification. That is, "particle size range 75-212 μm" indicates that the silica gel particles passed through a sieve with a mesh size of 212 μm but did not pass through a sieve with a mesh size of 75 μm. The moisture adsorption amount of each silica gel was measured according to the method described above in <Evaluation of hydrophilicity of pore inner surfaces: moisture adsorption amount measurement in low-humidity nitrogen>, and the moisture adsorption amount was 0.00002 g / m ２ The silica gel thus obtained was designated as hydrophilic silica gel.

[0155] For the formulation examples of the impregnation solutions used in the comparative examples and examples, the blending ratios of the raw material oligoamine compounds and modifiers are shown in Table 2. Table 2 also shows the total amine value and the content of primary amino groups of the raw material oligoamine compounds before the formation of the carbamic acid (salt) structure.

[0156]

[0157] [Manufacturing Example 1: Preparation of Solid Absorbents for Carbon Dioxide Separation of Comparative Examples 1 to 5] An oligoamine compound and a modifier were weighed out in a glass container in a total amount of 1 g in the blending ratios shown in Table 2, and 10 g of methanol was added. The mixture was then stirred and mixed at room temperature for 30 minutes using a magnetic stirrer to prepare an impregnation solution for a carbon dioxide separation composition. 1 g of the powdery porous material shown in Tables 3 and 4 was added to the impregnation solution, and the mixture was impregnated with stirring for 30 minutes. Next, a solvent removal step was performed using an evaporator (bath temperature 60°C, 50 kPa), followed by a drying step under reduced pressure at 60°C and 20 Pa. A solid absorbent for carbon dioxide separation was obtained, in which the carbon dioxide separation composition containing the oligoamine compound and modifier of Blending Examples 1 and 2 was supported on the porous material.

[0158] [Manufacturing Example 2: Preparation of Solid Absorbents for Carbon Dioxide Separation of Examples 1 to 9] A total of 10 g of oligoamine compound and modifier were weighed into a glass container in the blending ratios shown in Table 2, and 10 g of water was added. The mixture was then stirred and mixed at room temperature for 30 minutes using a magnetic stirrer to prepare an impregnation solution for a carbon dioxide separation composition. 1 g of the powdery porous material shown in Tables 3 and 4 was added to the impregnation solution and stirred for 5 minutes. The impregnation solution in which the porous material was immersed was then reduced in pressure to 50 kPa at 40 °C to remove air bubbles inside the porous material, allowing the impregnation solution to penetrate into the pores. Next, the excess impregnation solution was removed by suction filtration, and the mixture was dried for 6 hours at 60 °C under a carbon dioxide-containing atmosphere (nitrogen gas containing 400 ppm by volume of carbon dioxide). This yielded a solid absorbent for carbon dioxide separation in which the porous material was supported with a carbon dioxide separation composition containing the oligoamine compound and modifier of Blending Examples 3 to 10.

[0159] [Manufacturing Example 3: Preparation of solid absorbents for carbon dioxide separation of Comparative Examples 6 to 8, and 10] An oligoamine compound and a modifier were weighed out into a glass container in the blending ratios shown in Table 2 so that the total amount was 10 g, and 10 g of water was added. The mixture was then stirred and mixed at room temperature for 30 minutes using a magnetic stirrer to prepare an impregnation solution for a carbon dioxide separation composition. 1 g of a powdery porous material shown in Tables 3 and 4 was added to the impregnation solution and stirred for 5 minutes. Next, after a step of removing excess impregnation solution by suction filtration, the mixture was left to stand overnight in air at room temperature to obtain a solid absorbent for carbon dioxide separation in which the porous material carried a carbon dioxide separation composition containing the oligoamine compound and modifier of Blending Examples 3 and 10 above.

[0160] [Manufacturing Example 4: Preparation of a solid absorbent for carbon dioxide separation of Comparative Example 9] An oligoamine compound and a modifier were weighed out into a glass container in the blending ratio shown in Table 2 so that the total amount was 10 g, and 10 g of water was added. After that, an impregnation solution of a carbon dioxide separation composition was prepared by stirring and mixing for 30 minutes at room temperature using a magnetic stirrer. 1 g of the powdery porous material shown in Tables 3 and 4 was added to the impregnation solution, and the mixture was shaken by ultrasonic irradiation at 40°C for 30 minutes, and dried at 80°C and 0.1 kPa for 2 hours to obtain a solid absorbent for carbon dioxide separation in which the porous material carried the carbon dioxide separation composition containing the oligoamine compound and modifier of Blending Example 10 above.

[0161] [Content and content of carbamic acid (salt) structure in oligoamine compound in carbon dioxide separation composition] The carbamic acid (salt) structure in the oligoamine compound is generated by dissolving the carbon dioxide separation composition in the solid absorbent for carbon dioxide separation in heavy water. １３ C-NMR was measured, and the signal (peak) derived from the carbamic acid (salt) structure 13C at 163 to 166 ppm was integrated to determine the area Ac, and the signal (peak) derived from the methylene structure 13C at 36 to 58 ppm was integrated to determine the area Am, and the content C (%) of the carbamic acid (salt) structure was calculated using the following formula. Note that the factor F for correcting the intensity of the signal derived from the carbamic acid (salt) structure 13C and the signal (peak) derived from the methylene structure 13C is the ratio of monoethanolamine and CO ２was dissolved in heavy water, and the equimolar area ratio of the signal (peak) derived from the carbamic acid (salt) structure and the signal (peak) derived from the methylene structure was measured, and the value F=0.366 was used.

[0162] Content of carbamic acid (salt) structure: C (%) = (area of ​​carbamic acid (salt) structure 13C: Ac) ÷ (area of ​​methylene structure 13C: Am) ÷ (intensity correction factor: F).

[0163] [Total amine value and primary amino group content in oligoamine compound] In the carbon dioxide separation composition, the total amine value and the primary amino group content of the oligoamine compound were calculated and are shown in Tables 3 and 4. Note that, because the carbamic acid (salt) structure of the oligoamine compound releases carbon dioxide when the total amine value is measured, the nitrogen atom that formed the carbamic acid (salt) structure is calculated as an amine. Therefore, the total amine value of the oligoamine compound is the same value as the total amine value of the raw material oligoamine compound described above.

[0164] [Measurement of Water Content in Carbon Dioxide Separation Composition] The solid absorbents for carbon dioxide separation of Examples 1 to 9 were dried in a dry nitrogen stream at 120°C for 1 hour by differential thermal analysis to measure the water content in the carbon dioxide separation composition contained in the solid absorbent for carbon dioxide separation.

[0165] The water content in the carbon dioxide separation composition contained in the solid absorbent for carbon dioxide separation of Examples 1 to 9 was 1 wt % to 30 wt % relative to the total weight of the carbon dioxide separation composition. The water content in each carbon dioxide separation composition is shown in Tables 3 and 4.

[0166] [Measurement of Moisture Content in Solid Absorbent] The solid absorbents for carbon dioxide separation of Examples 1 to 9 were dried in a dry nitrogen stream at 120°C for 1 hour to measure the moisture content in the solid absorbent by differential thermal analysis.

[0167] The water content of the solid absorbent for carbon dioxide separation in Examples 1 to 9 was 4% by weight to 12% by weight, based on the total weight of the solid absorbent for carbon dioxide separation. The water content of each solid absorbent for carbon dioxide separation can be calculated as follows using the water content of the carbon dioxide separation composition shown in Tables 3 and 4.

[0168] [Conversion formula for moisture content in solid absorbent] Moisture content (wt %) contained in solid absorbent = [(parts by weight of blend of oligoamine compound and modifier in solid absorbent: non-volatile content) × (moisture content of carbon dioxide separation composition) ÷ {100 - (moisture content of carbon dioxide separation composition)}] ÷ (100 + [(parts by weight of blend of oligoamine compound and modifier in solid absorbent: non-volatile content) × (moisture content of carbon dioxide separation composition) ÷ {100 - (moisture content of carbon dioxide separation composition)}]. [Calculation of the amount of non-volatile content of carbon dioxide separation composition supported in solid absorbent for carbon dioxide separation] The amount of non-volatile content of the carbon dioxide separation composition was calculated according to the method described above in <Calculation of the amount of non-volatile content of carbon dioxide separation composition supported on hydrophilic silica gel by thermogravimetry>. The calculated non-volatile content of the carbon dioxide separation composition in the solid absorbent for carbon dioxide separation is shown in Tables 3 and 4 as the weight ratio between the porous material and the blending example (blend of oligoamine compound and modifier).

[0169] [Carbon dioxide desorption test] Using the obtained solid absorbent for carbon dioxide separation, two carbon dioxide desorption tests were carried out according to the above-mentioned methods of <Carbon dioxide adsorption / desorption test using carbon dioxide-containing gas simulating dry atmosphere> and <Carbon dioxide adsorption / desorption test using carbon dioxide-containing gas simulating dry closed space>. The respective results are shown in Tables 3 and 4.

[0170]

[0171] According to the results in Table 3, as shown in Comparative Examples 3 to 5, the conventional manufacturing method (Manufacturing Example 1) showed inferior results in terms of adsorption / desorption capacity and amine efficiency compared to Comparative Examples 1 and 2, which used regular mesoporous silica, even when Formulation Example 2, an improved carbon dioxide separation composition, was supported on silica gel. On the other hand, by carrying out the manufacturing method (Manufacturing Example 2) according to the present invention, the adsorption / desorption capacity and amine efficiency were improved, making it possible to demonstrate performance comparable to that of Comparative Example 2 (SBA-15: mesoporous silica, confirmation of reproducibility of Non-Patent Document 4). Furthermore, as shown in Examples 1 to 8, by using a solid absorbent for carbon dioxide separation supported on the composition of the present invention, it became possible to create a solid absorbent that achieves a large adsorption / desorption capacity and high amine efficiency, which greatly exceeds the performance of solid absorbents of the prior art.

[0172]

[0173] According to the results in Table 4, as shown in Comparative Examples 3 to 5, in the conventional manufacturing method: Manufacturing Example 1, even when Formulation Example 2, which is an improved composition for carbon dioxide separation, was supported on silica gel, no significant advantages were observed in terms of adsorption / desorption amount and amine efficiency compared to Comparative Examples 1 and 2, which used regular mesoporous silica. Furthermore, even when Manufacturing Method: Manufacturing Example 3 was carried out, no significant advantages were observed in terms of adsorption / desorption amount and amine efficiency in Comparative Examples 7 and 8. On the other hand, as shown in Examples 1 to 3 and 6 to 9, by using a solid absorbent for carbon dioxide separation supported with the composition of the present invention, it became possible to create a solid absorbent that achieves a large adsorption / desorption amount and high amine efficiency that greatly exceeds the performance of solid absorbents of the prior art.

[0174] As shown in Tables 3 and 4, the solid absorbents for carbon dioxide separation of the examples show that they can efficiently separate or recover carbon dioxide from low partial pressure or low concentration carbon dioxide-containing gas compositions under temperature and humidity conditions expected in actual operation.

[0175] The carbon dioxide separation composition and solid absorbent for carbon dioxide separation of the present invention can be suitably used, for example, for carbon dioxide separation and capture (DAC) from air, for carbon dioxide separation and capture from exhaust gases from power plants and factories, and for carbon dioxide removal in closed spaces such as submarines and spacecraft.

[0176] This application is based on Japanese Patent Application No. 2023-188170 filed on November 2, 2023, the disclosure of which is incorporated herein by reference in its entirety.

Claims

1. A composition for separating carbon dioxide, comprising: an oligoamine compound having a boiling point of 200°C or higher; and a modifier having a boiling point of 200°C or higher; a portion of the total nitrogen atoms of the oligoamine compound having a carbamic acid or salt structure, and the proportion of nitrogen atoms forming the carbamic acid or salt structure of the oligoamine compound is 0.1% to 20% relative to the total nitrogen atoms of the oligoamine compound.

2. The carbon dioxide separating composition according to claim 1, wherein the water content is 1% by weight to 30% by weight based on the total weight of the carbon dioxide separating composition.

3. A composition for carbon dioxide separation according to claim 1 or 2, wherein the oligoamine compound is a polyethyleneimine having a number average molecular weight of 200 or more and less than 2,000.

4. A composition for separating carbon dioxide described in claim 1 or 2, wherein the oligoamine compound is a compound in which primary amine structures account for 5% or more of the total amine structures.

5. A composition for carbon dioxide separation according to claim 1 or 2, wherein the HSP value of the modifier is ΔD of 12 or more and 22 or less, ΔP of 5 or more and 15 or less, and ΔH of 3 or more and 30 or less.

6. A composition for carbon dioxide separation according to claim 1 or 2, wherein the modifier is a compound having a polyethylene glycol structure.

7. A solid absorbent for separating carbon dioxide, comprising the composition for separating carbon dioxide according to claim 1 or 2 supported on hydrophilic silica gel.

8. The solid absorbent for separating carbon dioxide according to claim 7, wherein the physical properties of the hydrophilic silica gel satisfy one or more selected from the group consisting of the following (i) to (iv): (i) a pore volume of 0.6 cm ３ / g to 3.0 cm ３ / g; (ii) an average pore diameter of 5 nm to 80 nm; (iii) a specific surface area of ​​70 m ２ / g~800m ２ / g; (iv) a bulk density of 0.10 g / cm ３ The end.

9. A solid absorbent for separating carbon dioxide according to claim 7, which satisfies one or more selected from the group consisting of the following (i) and (ii): (i) in a carbon dioxide adsorption / desorption test using air having a carbon dioxide concentration of 300 ppm by volume to 500 ppm by volume and an absolute humidity of 2 g / kg or less, in a step of releasing carbon dioxide absorbed by the solid absorbent at 40°C at 70°C, the amount of carbon dioxide adsorbed / desorbed per gram of the solid absorbent is 0.90 mmol or more, and the amount of carbon dioxide adsorbed / desorbed per mole of amine contained in the solid absorbent is 0.20 mol or more; (ii) In a carbon dioxide adsorption / desorption test using air having a carbon dioxide concentration of 9,000 ppm by volume to 11,000 ppm by volume and an absolute humidity of 2 g / kg or less, in a step of releasing carbon dioxide absorbed by the solid absorbent at 70°C at 100°C, the amount of carbon dioxide adsorbed and desorbed per gram of the solid absorbent is 1.30 mmol or more, and the amount of carbon dioxide adsorbed and desorbed per mole of amine contained in the solid absorbent is 0.20 mol or more.

10. A method for producing a solid absorbent for separating carbon dioxide, comprising: (1) a first step of preparing an impregnation liquid containing an oligoamine compound having a boiling point of 200°C or higher, a modifier having a boiling point of 200°C or higher, and water; (2) a second step of impregnating hydrophilic silica gel with the impregnation liquid; (3) a third step of separating the hydrophilic silica gel impregnated with the impregnation liquid from excess impregnation liquid; and (4) a fourth step of drying the hydrophilic silica gel impregnated with the impregnation liquid by evaporating water in an atmosphere containing carbon dioxide.

11. A method for producing a solid absorbent for separating carbon dioxide according to claim 10, which satisfies one or more of the following conditions selected from the group consisting of (a) to (c): (a) the second step is carried out at a temperature range of 20°C to 90°C; (b) the second step includes a step of degassing the inside of hydrophilic silica gel pores under a reduced pressure of -0.08 MPaG to -0.004 MPaG; (c) the fourth step is carried out at a temperature range of 30°C to 100°C using air as an atmosphere containing carbon dioxide.

Images