Solid absorber, and method for absorbing and desorbing acidic gas by using same

Abstract

This solid absorber reversibly absorbs an acidic gas, and comprises a porous base material and an acidic gas absorbing agent supported on the porous base material. The acidic gas absorbing agent contains at least one amine represented by any one of general formulae (1), (2), and (3). (In formulae (1), (2), and (3), R1 represents the group -(CH2)l-NH-[(CH2)2NH]m-(CH2)n-CH3, and, in R1, l represents 1 or 2, and m and n each independently represent an integer of 0-2.)

Description

Solid absorbent and method for absorbing and desorbing acidic gases using the same

[0001] The present invention relates to a solid absorbent material that reversibly absorbs acid gases, and a method for absorbing and desorbing acid gases using the same.

[0002] Conventionally, solid absorbents that reversibly absorb acidic gases such as carbon dioxide, NOx (nitrogen oxides), SOx (sulfur oxides), and HCl contained in combustion exhaust gases discharged from combustion facilities such as thermal power plants, steelworks blast furnaces, steelworks converters, and boilers have been known. Technology has also been developed for applying such solid absorbents to DAC (Direct Air Capture), which directly captures these acidic gases, particularly carbon dioxide, from the atmosphere. Such solid absorbents generally comprise a porous substrate (e.g., porous particles) carrying an amine, a liquid chemical that reversibly absorbs acidic gases.

[0003] As an example of such a solid absorbent, Patent Document 1 describes a carbon dioxide separating material containing a polyamine support in which a polyamine having at least two isopropyl groups on the nitrogen atom is supported on a support.

[0004] As another example of such a solid absorbent, Patent Document 2 describes an acidic gas absorbent comprising porous particles and an acidic gas absorbent (e.g., an amine) supported on the porous particles. In the acidic gas absorbent described in Patent Document 2, the porous particles have bimodal pores including mesopores having pore sizes in the nanometer range of 2 nm to 200 nm in diameter and macropores having pore sizes in the micrometer range of more than 0.2 μm in diameter, and the macropores are vacant, while the mesopores are filled with the acidic gas absorbent.

[0005] JP 2015-9185 A JP 2020-75215 A

[0006] An object of the present disclosure is to provide a solid absorbent material that has low hygroscopicity and is capable of efficiently absorbing acid gases, particularly carbon dioxide, in a reversible manner.

[0007] A solid absorbent according to a first aspect of the present disclosure is a solid absorbent that reversibly absorbs acidic gases, and includes a porous substrate and an acidic gas absorbing agent supported on the porous substrate, wherein the acidic gas absorbing agent includes at least one amine represented by any one of the following general formulas (1), (2), and (3): (In formulas (1), (2) and (3), R １ is a group: -(CH ２ ) ｌ -NH-[(CH ２ ) ２ N.H.] ｍ - (CH ２ ) ｎ -CH ３ and R １ In the formula, l represents 1 or 2, and m and n each independently represent an integer of 0 to 2.

[0008] Alternatively, another solid absorbent according to the first aspect of the present disclosure includes a porous substrate and an acidic gas absorbing agent supported on the porous substrate, wherein the acidic gas absorbing agent includes at least one amine represented by the following general formula (4): (In formula (4), two R ２ The groups may be the same or different in structure, p is 2 or 3, q ​​is an integer of 2 to 5, and R ２ is the following R ２ (1) ~R ２ (9): is a group represented by any one of the following:

[0009] A method for absorbing and desorbing acidic gases according to a second aspect of the present disclosure includes the steps of: bringing a gas to be treated into contact with either one of the solid absorbent material according to the first aspect and another solid absorbent material according to the first aspect, thereby absorbing the acidic gas; and bringing steam into contact with the solid absorbent material that has absorbed the acidic gas, thereby desorbing the acidic gas from the solid absorbent.

[0010] According to the present disclosure, it is possible to provide a solid absorbent material that has low hygroscopicity and is capable of efficiently absorbing acid gases, particularly carbon dioxide, in a reversible manner.

[0011] FIG. 1 shows the positions a-e of hydrogen in the amine represented by (1-1), which is the target of Example 1, and the measured 1H-NMR chart. FIG. 2 shows the positions a-e of hydrogen in the amine represented by (2-1), which is the target of Example 2, and the measured 1H-NMR chart. FIG. 3 shows the positions a-c of hydrogen in the amine represented by (3-1), which is the target of Example 3, and the measured 1H-NMR chart. FIG. 4 shows the positions a-g of hydrogen in the amine represented by (4-4), which is the target of Example 4, and the measured 1H-NMR chart. FIG. 5 shows the 1H-NMR chart measured in Example 5. FIG. 6 shows the positions a-i of hydrogen in the amine represented by (4-3), which is the target of Example 6, and the measured 1H-NMR chart. FIG. 7 is a graph showing the measurement results of the saturated carbon dioxide absorption capacity (mol / kg) per weight of the solid absorbent in the examples. FIG. 8 is a graph showing the measurement results of saturated water absorption per weight (mol / kg) of the solid absorbent material in the examples.

[0012] The solid absorbents that reversibly absorb acid gases as described above are generally used in acid gas separation systems (particularly carbon dioxide separation systems). Examples of acid gas separation systems include batch processing systems and moving bed systems (continuous processing systems). In these acid gas separation systems, a process of absorbing acid gases into the solid absorbent and a process of desorbing acid gases from the solid absorbent using steam or the like (i.e., a process of regenerating the solid absorbent) are repeatedly performed. Therefore, the solid absorbent is required to efficiently absorb and desorb acid gases, particularly carbon dioxide.

[0013] Furthermore, in such an acid gas separation system, if the solid absorbent absorbs excessive moisture, the solid absorbent becomes sticky and difficult to handle. Poor handling of the solid absorbent significantly reduces the acid gas absorption characteristics of the solid absorbent in a moving bed system involving the movement of the solid absorbent. Even in a batch treatment system, poor handling of the solid absorbent makes it difficult to replace the solid absorbent. Therefore, it is preferable for the solid absorbent to have low moisture absorption.

[0014] The present inventors have conducted extensive research into solid absorbents that are low in hygroscopicity and can efficiently absorb acidic gases, particularly carbon dioxide, reversibly. They have found that a solid absorbent comprising a porous substrate and an acidic gas absorbent supported on the porous substrate can exhibit such effects when the acidic gas absorbent contains at least one amine represented by a specific general formula. They have also found that the solid absorbent can desorb acidic gases using waste heat that cannot generally be effectively utilized.

[0015] In this specification, "waste heat" refers to low-temperature thermal energy of 40°C or higher and 100°C or lower that cannot generally be used effectively and that is inevitably generated from various manufacturing industries, power plants, etc., low-temperature thermal energy from sunlight that cannot generally be used effectively, etc. Therefore, the solid absorbent material in this embodiment is also excellent from an environmental perspective.

[0016] In this specification, the term "acid gas" refers to carbon dioxide, NOx (NO, NO), and the like, which are generally contained in combustion exhaust gas, the atmosphere, the atmosphere of a closed space, and the like. ２ , N ２ O, N ２ O ３ The term "acid gas" refers to acidic gases such as nitrogen oxides (SOx), sulfur oxides (SOx), and HCl. Of these, carbon dioxide is preferred as the acidic gas to be absorbed, from the viewpoint of achieving favorable effects on the environment.

[0017] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Note that the scope of the present invention is not limited to the embodiments described here, and various modifications can be made without departing from the spirit of the present invention.

[0018] 1. Solid Absorbent The solid absorbent of this embodiment will be described in detail below. In this specification, the term "solid absorbent" refers to a solid absorbent capable of reversibly absorbing acidic gases. In addition, in this specification, the term "capable of reversibly absorbing acidic gases (particularly carbon dioxide)" refers to the ability to absorb (or recover) and desorb (i.e., regenerate) acidic gases (particularly carbon dioxide). The solid absorbent of this embodiment includes a first solid absorbent and a second solid absorbent.

[0019] [First solid absorbent] The first solid absorbent includes a porous substrate and an acidic gas absorbent supported on the porous substrate. First, the acidic gas absorbent in the first solid absorbent will be described in detail below.

[0020] (Acidic gas absorbing agent) The acidic gas absorbing agent in the first solid absorbent contains at least one amine represented by any one of the following general formulas (1), (2) and (3) (hereinafter also referred to as "amine of the first solid absorbent").

[0021] In formulas (1), (2) and (3), R １ is a group: -(CH ２ ) ｌ -NH-[(CH ２ ) ２ N.H.] ｍ - (CH ２ ) ｎ -CH ３ and R １ In the formula, l represents 1 or 2, and m and n each independently represent an integer of 0 to 2.

[0022] R １In the formula, l is preferably 1. When l is 1, the amine of the first solid absorbent having a significantly stable structure can be obtained in high yield, and ultimately the production efficiency of the solid absorbent can be improved.

[0023] R １ In the formula (I), m preferably represents 0 or 1. When m is 0 or 1, it is possible to finally produce a solid absorbent material that has good low moisture absorption properties and can more efficiently desorb acid gases, particularly carbon dioxide.

[0024] R １ In the formula (I), n preferably represents 0 or 1, and more preferably represents 0. When n is 0, it is possible to finally produce a solid absorbent material that can reversibly absorb acid gases, particularly carbon dioxide, more efficiently.

[0025] The acid gas absorbing agent in the first solid absorbent may be a mixture of two or more amines represented by any one of the above general formulas (1), (2) and (3), or may contain a single amine selected from these, or may be a single amine selected from these.

[0026] More specifically, the amine of the first solid absorbent preferably has a structure represented by any one of the following (1-1), (1-2), (2-1) and (3-1).

[0027] When the amine of the first solid absorbent has any of the structures described above, it is possible to finally produce a solid absorbent that has good low moisture absorption properties and can reversibly absorb acid gases, particularly carbon dioxide, more efficiently.

[0028] The synthesis method of the amine of the first solid absorbent is not particularly limited, and may be any method known to those skilled in the art. For example, the amine of the first solid absorbent may be synthesized by the following method. Specifically, a benzaldehyde having multiple aldehyde groups may be used as a starting material, and an amine-containing modified chain may be introduced by a reductive amination reaction.

[0029] More specifically, for example, the amine of the first solid absorbent having a structure represented by any one of the above (1-1), (2-1) and (3-1) can be synthesized by a method described in detail in the examples below.

[0030] The amine content of the first solid absorbent relative to the total mass of the first solid absorbent is not particularly limited, but is preferably 10% by mass or more. When the amine content of the first solid absorbent is 25% by mass or more, the finally produced solid absorbent can more efficiently absorb and desorb acidic gases, particularly carbon dioxide. The amine content of the first solid absorbent is more preferably 10% by mass or more, and even more preferably 25% by mass or more. Furthermore, the upper limit of the amine content of the first solid absorbent is not particularly limited, but is, for example, 50% by mass or less.

[0031] The acidic gas absorbent may be composed only of at least one amine of the first solid absorbent, but may also contain other compounds as long as the effect of the first solid absorbent in this embodiment is exhibited. For example, the acidic gas absorbent may contain an amine compound other than the amine of the first solid absorbent, such as polyethyleneimine, tetraethylenepentamine, or an amine or non-amine by-product (unavoidably) contained during amine synthesis.

[0032] (Porous Substrate) The porous substrate supports the acid gas absorbing agent described above.

[0033] The type of porous substrate is not particularly limited. Specifically, the porous substrate can be made of any material known to those skilled in the art that can support the acid gas absorbing agent and has a large number of pores that can be used to reversibly absorb acid gases, particularly carbon dioxide.

[0034] Examples of porous substrates include silica such as silica gel or mesoporous silica, alumina such as activated alumina, zeolite, titania, zirconia, magnesia, activated carbon, and metal-organic frameworks (MOFs). The porous substrate may be a powder. The porous substrate may also be formed using a powder and an appropriate binder. For example, the porous substrate may be granulated (typically 1 mm to 5 mm) at the time of production.

[0035] (Method for manufacturing solid absorbent) The first solid absorbent includes a porous substrate and an acid gas absorbing agent supported on the porous substrate. A method for manufacturing the first solid absorbent will be described below.

[0036] (1) Preparation of Acidic Gas Absorbent Solution First, at least one of the amines of the first solid absorbent material contained in the acidic gas absorbent is dissolved in a solvent (water or alcohol) to prepare an acidic gas absorbent solution.

[0037] The temperature of the prepared amine-containing acidic gas absorbing agent solution of the first solid absorbent is not particularly limited, but is preferably 10° C. or higher and 100° C. or lower. Since it is known that the viscosity of a solution containing an amine decreases with increasing temperature, when the temperature of the acidic gas absorbing agent solution is 10° C. or higher, the amine can be uniformly supported on the porous substrate. Furthermore, when the temperature of the acidic gas absorbing agent solution is 100° C. or lower, oxidation and / or evaporation of the amine can be suppressed.

[0038] The concentration of the amine of the first solid absorbent in the acidic gas absorption agent solution is not particularly limited, but may be adjusted to an appropriate value in the range of 5% by mass to 70% by mass depending on the type of amine of the first solid absorbent. If the amine concentration of the first solid absorbent in the solution is too low, the amount of amine supported on the porous substrate may be insufficient. Furthermore, if the amine concentration of the first solid absorbent in the solution is too high, the amine may clog the pores of the porous substrate, reducing the acidic gas absorption performance of the first solid absorbent.

[0039] (2) Impregnation step Next, the porous substrate (for example, the porous particles described above) is placed in an immersion container filled with the acidic gas absorbing agent solution, and the porous substrate is impregnated with the acidic gas absorbing agent solution. The immersion time of the porous substrate is not particularly limited as long as the inside of the pores is sufficiently degassed. For example, the immersion time can be 24 hours. In this case, to shorten the immersion time, the acidic gas absorbing agent solution may be stirred or ultrasonic vibration may be applied to the immersion container.

[0040] (3) Drying step: The porous substrate is then removed from the acidic gas absorbing agent solution, and excess liquid is removed by suction filtration or other methods. The porous substrate impregnated with the acidic gas absorbing agent solution is then subjected to air drying or reduced pressure drying at a temperature close to room temperature. After drying, a first solid absorbent can be obtained.

[0041] [Second solid absorbent] The second solid absorbent also includes a porous substrate and an acidic gas absorbent supported on the porous substrate. First, the acidic gas absorbent in the second solid absorbent will be described in detail below.

[0042] (Acidic Gas Absorbent) The acidic gas absorbent in the second solid absorbent contains at least one amine represented by the following general formula (4) (hereinafter also referred to as "amine of the second solid absorbent").

[0043] In formula (4), two R ２ The groups may be the same or different in structure, p is 2 or 3, q ​​is an integer of 2 to 5, and R ２ is the following R ２ (1) ~R ２ (9): It is a group represented by any one of the following:

[0044] In this specification, "two R ２ The phrase "the two terminal R groups may have the same or different structures" refers to the general formula (4) above. ２ The group is the same as R ２ (1) ~R ２ (9) or the same group represented by any of the above R ２ (1) ~R２ (9) means that the groups may be different from each other.

[0045] Preferably, p is 3. When p is 3, it is possible to finally produce a solid absorbent material that has good low moisture absorption properties and can more efficiently desorb acid gases, especially carbon dioxide.

[0046] q preferably represents 2 or 3, and more preferably represents 2. When q is 2, it is possible to finally produce a solid absorbent material that has good low moisture absorption properties and can reversibly absorb acid gases, particularly carbon dioxide, more efficiently.

[0047] The acid gas absorbing agent in the second solid absorbent may be a mixture of two or more of the amines represented by the above general formula (4), or may contain a single amine selected from these, or may be a single amine selected from these.

[0048] More specifically, the amine of the second solid absorbent preferably has any one of the structures represented by the following (4-1) to (4-6).

[0049] When the amine of the second solid absorbent has any of the structures described above, it is possible to finally produce a solid absorbent that has good low moisture absorption properties and can reversibly absorb acid gases, particularly carbon dioxide, more efficiently.

[0050] Furthermore, it is more preferable that the amine of the second solid absorbent has any of the structures represented by (4-1) to (4-3) above. When the amine of the second solid absorbent has any of the structures represented by (4-1) to (4-3) above, it is possible to finally produce a solid absorbent that has good low moisture absorption properties and can reversibly absorb acidic gases, particularly carbon dioxide, more reliably and efficiently.

[0051] The method for synthesizing the amine of the second solid absorbent is not particularly limited, and any method known to those skilled in the art may be used. For example, the amine of the second solid absorbent can be synthesized by the following method. First, a chain alkyl group is introduced into a commercially available polyamine having an -NH group, or a polyamine having an -NH group obtained by any method known to those skilled in the art, by a reaction known to those skilled in the art, such as an addition reaction of an alkyl halide or a reductive amination reaction of a ketone with a terminal amino group.

[0052] More specifically, for example, the amine of the second solid absorbent having any of the structures represented by (4-1), (4-2), and (4-3) above can be synthesized by the method described in detail in the Examples below.

[0053] The preferred amount of the amine content of the second solid absorbent relative to the total mass of the second solid absorbent is the same as the preferred amount of the amine content of the first solid absorbent relative to the total mass of the first solid absorbent described above.

[0054] The acidic gas absorbing agent may be composed only of the amine of at least one of the second solid absorbents described above, but may also contain other compounds, as in the case of the first solid absorbent described above, as long as the effect of the second solid absorbent in this embodiment is achieved.

[0055] The details of the porous substrate and the method of manufacturing the solid absorbent material in the second solid absorbent material are similar to those of the first solid absorbent material described above.

[0056] As described above, the first and second solid absorbents of this embodiment have low hygroscopicity and can efficiently absorb acidic gases, particularly carbon dioxide, reversibly. Furthermore, the first and second solid absorbents of this embodiment are environmentally friendly because they can desorb acidic gases from the solid absorbents using waste heat that cannot generally be effectively utilized.

[0057] 2. Method for Absorbing and Desorbing Acidic Gases The method for absorbing and desorbing acidic gases (particularly carbon dioxide) in this embodiment includes a step of bringing a gas to be treated into contact with the first or second solid absorbent material in the above-described embodiment to absorb the acidic gas, and a step of bringing steam into contact with the solid absorbent material that has absorbed the acidic gas, thereby desorbing the acidic gas from the solid absorbent material.

[0058] In this specification, the term "gas to be treated" is not particularly limited as long as it is a gas containing acidic gas, particularly carbon dioxide. Examples of such gases include combustion exhaust gases emitted from combustion equipment such as thermal power plants fueled by coal, heavy oil, natural gas, etc., blast furnaces in steelworks that reduce iron oxide with coke, converters in steelworks that burn carbon in pig iron to make steel, and boilers in various manufacturing plants, as well as gases emitted from transportation equipment such as automobiles, ships, and aircraft that use gasoline, heavy oil, light oil, etc. as fuel. Other examples of gases to be treated include the atmosphere containing acidic gases, particularly carbon dioxide, and the ambient atmosphere containing carbon dioxide emitted by breathing by people in enclosed spaces such as submersible research vessels and space stations, and by energy conversion by equipment.

[0059] The acidic gas content and temperature of the gas to be treated are not particularly limited as long as they are conditions that allow the first or second solid absorbent material in the above-described embodiment to absorb the acidic gas when it comes into contact with the gas. For example, if the acidic gas is carbon dioxide, the carbon dioxide partial pressure may be 0.04 kPa to 50 kPa and the temperature may be 20°C to 60°C.

[0060] For example, when the acidic gas is carbon dioxide, the carbon dioxide may be desorbed by contacting the solid absorbent with steam at 50°C or higher, for example, as in any method known to those skilled in the art. Furthermore, from the viewpoint of efficiently desorbing carbon dioxide, the carbon dioxide desorption step preferably involves contacting the solid absorbent with steam under reduced pressure conditions. The reduced pressure conditions are preferably 5 kPa or more and 100 kPa or less, and more preferably 15 kPa or more and 30 kPa or less.

[0061] On the other hand, as described in the above embodiment, the first and second solid absorbents that have absorbed the acidic gas can desorb the acidic gas even using waste heat, which is generally not effectively utilized. Therefore, in the step of desorbing the acidic gas, from the viewpoint of being environmentally superior, it is preferable to desorb the acidic gas from the solid absorbent by contacting it with low-temperature steam generated by the waste heat. For example, when the acidic gas is carbon dioxide, the temperature of the waste heat is preferably 40°C or higher and 100°C or lower, more preferably 50°C or higher and 70°C or lower.

[0062] By adopting the method of this embodiment in, for example, a medium- or large-scale acid gas separation system (particularly a carbon dioxide separation system), it is possible to achieve a system that is environmentally friendly and capable of efficiently absorbing and desorbing acid gases (particularly carbon dioxide) from exhaust gas.

[0063] [Summary of the Disclosure] The specific embodiments described above include disclosures having the following configurations.

[0064] A solid absorbent according to a first aspect of the present disclosure is a solid absorbent that reversibly absorbs acidic gases, and includes a porous substrate and an acidic gas absorbing agent supported on the porous substrate, wherein the acidic gas absorbing agent includes at least one amine represented by any one of the following general formulas (1), (2), and (3): (In formulas (1), (2) and (3), R １ is a group: -(CH ２ ) ｌ -NH-[(CH ２ ) ２ N.H.] ｍ - (CH ２ ) ｎ -CH ３ and R １ In the formula, l represents 1 or 2, and m and n each independently represent an integer of 0 to 2.

[0065] The solid absorbent material of the first aspect has low moisture absorption and can reversibly absorb acid gases, particularly carbon dioxide, efficiently.

[0066] A solid absorbent according to a second aspect of the present disclosure is the solid absorbent according to the first aspect, wherein the amine has a structure represented by any one of the following (1-1), (1-2), (2-1), and (3-1):

[0067] The solid absorbent material of the second aspect has good low moisture absorption properties and can reversibly absorb acid gases, particularly carbon dioxide, more efficiently.

[0068] A solid absorbent according to a third aspect of the present disclosure is a solid absorbent that reversibly absorbs acidic gases, and includes a porous substrate and an acidic gas absorbing agent supported on the porous substrate, wherein the acidic gas absorbing agent includes at least one amine represented by the following general formula (4): (In formula (4), two R ２ The groups may be the same or different in structure, p represents 2 or 3, q ​​represents an integer of 2 to 5, and R2 represents the following R ２ (1) ~R ２ (9): is a group represented by any one of the following:

[0069] The solid absorbent material of the third aspect has low moisture absorption and can reversibly absorb acid gases, particularly carbon dioxide, efficiently.

[0070] A solid absorbent material according to a fourth aspect of the present disclosure is the solid absorbent material according to the third aspect, wherein the amine has a structure represented by any one of the following (4-1) to (4-6):

[0071] The solid absorbent material of the fourth aspect has good low moisture absorption properties and can reversibly absorb acid gases, particularly carbon dioxide, more efficiently.

[0072] A method for absorbing and desorbing acidic gases according to a fifth aspect of the present disclosure includes the steps of: bringing a gas to be treated into contact with the solid absorbent material according to any one of the first to fourth aspects to absorb the acidic gas; and bringing steam into contact with the solid absorbent material that has absorbed the acidic gas, thereby desorbing the acidic gas from the solid absorbent material.

[0073] According to the fifth aspect of the acid gas absorption and desorption method, since the solid absorbent has low hygroscopicity, it is possible to prevent a decrease in the handling performance of the solid absorbent, for example, in moving bed and batch treatment acid gas separation systems.

[0074] The present invention will be explained in more detail below with reference to examples, but the present invention is not limited to these examples in any way.

[0075] In this example, the first and second solid absorbents in this embodiment were actually manufactured, and the carbon dioxide saturated absorption capacity (kg / m) of the manufactured solid absorbents was measured. ３ ) and saturated water absorption (kg / m ３ ) measurements were carried out.

[0076] First, the synthesis method of the amine of the solid absorbent (i.e., acidic gas absorbing agent) used in each example and comparative example, the porous substrate used, and the method for producing the solid absorbent will be described in detail below. In addition, to confirm the target amine, except for Example 5, a proton nuclear magnetic resonance (H-NMR) device (manufactured by JEOL Ltd., "AL-400, ECZ400S"), a gas chromatography (GC) analyzer (manufactured by Shimadzu Corporation, "GC-2010 PlusAF"), and a gas chromatography mass spectrometry (GCMS) device (manufactured by Shimadzu Corporation, "GC / MS QP-2010Plus") were used.

[0077] [Method of synthesizing amine for solid absorbent] (Example 1) In Example 1, an amine having the structure represented by (1-1) above was used as the first amine for the solid absorbent. The synthesis method will be described in detail below.

[0078] First, 1,3,5-benzenetricarbaldehyde (reference substance) was added to an ethanol solution of N-Boc-methylethylenediamine, and the resulting solution was heated and stirred at 90°C for 1.5 hours. Thereafter, the reaction solution was cooled to around 0°C, and a reducing agent was added to reduce the imine. Next, a lipophilic component was recovered from the reaction product in which the imine had been reduced by liquid-liquid extraction separation using chloroform and water. Thereafter, trifluoroacetic acid was added to remove the protecting group of the imine, and the target product, presumably an amine having the structure represented by (1-1) above, was obtained from the recovered lipophilic component as a yellow oily substance. The yield was 54.6%.

[0079] Whether the obtained substance was the target amine having the structure represented by (1-1) above was confirmed as follows. 1H-NMR: Deuterated ethanol was used as the measurement solvent. Figure 1 shows the positions a to e of hydrogen atoms in the amine represented by (1-1) above, which was the target of Example 1, and the measured 1H-NMR chart. The 1H-NMR chart indicates which of the peaks a to e each corresponds to and the number of hydrogen atoms. As shown in Figure 1, the 1H-NMR chart confirmed that the amine represented by (1-1) above had been produced. GC and GCMS: The peaks of the product were confirmed by GC, and the product was subjected to mass analysis by GCMS, confirming the amine represented by (1-1) above.

[0080] Example 2 In Example 2, an amine having the structure represented by the above formula (2-1) was used as the first solid absorbent amine. The synthesis method will be described in detail below.

[0081] First, isophthalaldehyde (reference substance) was dissolved in toluene, and then a methylamine aqueous solution was added to the solution, followed by stirring at room temperature for 3 hours. After completion of the reaction, the toluene layer of the reaction solution was recovered, and the solvent in the recovered solution was removed by evaporation. The resulting intermediate substance was then dissolved in acetone, and while further adding methanol to the solution, the imine was reduced with a reducing agent. Next, the lipophilic component was recovered from the reaction product by liquid-liquid extraction separation using chloroform and water, and the target product, presumably an amine having the structure represented by (2-1) above, was obtained from the recovered lipophilic component as a brown oily substance. The yield was 83.3%.

[0082] Whether the obtained substance was the target amine having the structure represented by (2-1) above was confirmed as follows. 1H-NMR: Deuterated dimethyl sulfoxide was used as the measurement solvent. Figure 2 shows the positions a to e of hydrogen atoms in the amine represented by (2-1) above, which was the target of Example 2, and the measured 1H-NMR chart. The 1H-NMR chart indicates which of the peaks a to e each corresponds to and the number of hydrogen atoms. As shown in Figure 2, the 1H-NMR chart confirmed that the amine represented by (2-1) above had been produced. GC and GCMS: The peaks of the product were confirmed by GC, and the product was subjected to mass analysis by GCMS, confirming the amine represented by (2-1) above.

[0083] Example 3 In Example 3, an amine having the structure represented by (3-1) above was used as the amine of the first solid absorbent. The synthesis method was the same as in Example 2 above, except that terephthaldicarboxaldehyde (reference substance) was used instead of isophthalaldehyde as the starting material, and the target product, which was assumed to be the amine having the structure represented by (3-1) above, was obtained in a yield of 67.9%.

[0084] Whether the obtained substance was the target amine having the structure represented by (3-1) above was confirmed as follows. 1H-NMR: Deuterated dimethyl sulfoxide was used as the measurement solvent. Figure 3 shows the positions a to c of hydrogen atoms in the amine represented by (3-1), the target substance of Example 3, and the measured 1H-NMR chart. The 1H-NMR chart indicates which of the peaks a to c each corresponds to and the number of hydrogen atoms. As shown in Figure 3, the 1H-NMR chart confirmed that the amine represented by (3-1) above had been produced. GC and GCMS: The peaks of the product were confirmed by GC, and the product was subjected to mass analysis by GCMS, confirming the amine represented by (3-1) above.

[0085] Example 4 In Example 4, an amine having the structure represented by the above (4-4) was used as the second solid absorbent amine. The synthesis method will be described in detail below.

[0086] First, 3,3-diaminodipropylamine (reference material), methyl ethyl ketone, and palladium carbon were charged into an autoclave, and ethanol was added to homogenize the mixture. The mixture was then filled with hydrogen gas at 0.9 MPa. The mixture was then heated at 50°C for 90 hours. The reaction solution was then filtered, and the solvent was removed to obtain the target product, which was presumed to be an amine having the structure represented by (4-4) above, as a yellow oil. The yield was 99.6%.

[0087] Whether the obtained substance was the target amine having the structure represented by (4-4) above was confirmed as follows. 1H-NMR: Deuterated chloroform was used as the measurement solvent. Figure 4 shows the positions a to g of hydrogen atoms in the amine represented by (4-4) above, which was the target of Example 4, and the measured 1H-NMR chart. The 1H-NMR chart indicates which of the peaks a to g each corresponds to and the number of hydrogen atoms. As shown in Figure 4, the 1H-NMR chart confirmed that the amine represented by (4-4) above had been produced. GC and GCMS: The peaks of the product were confirmed by GC, and the product was subjected to mass analysis by GCMS, confirming the amine represented by (4-4) above.

[0088] Example 5 In Example 5, an amine having the structure represented by (4-2) above was used as the amine of the second solid absorbent. The synthesis method was the same as that for the amine having the structure represented by (4-4) above, and the target substance, presumably the amine having the structure represented by (4-2) above, was obtained in the same procedure as in Example 4 above, except that diethyl ketone was initially used instead of methyl ethyl ketone. The yield was 73.5%.

[0089] Whether the obtained substance was the target amine having the structure represented by (4-2) above was confirmed as follows. 1H-NMR: 1H-NMR was performed using a nuclear magnetic resonance apparatus (manufactured by Bruker, "BRUKER NMR 400 MHz"). CDCl3 (20 to 40 mg / mL) was used as the solvent. Figure 5 shows the measured 1H-NMR chart. From the 1H-NMR chart shown in Figure 5, it was confirmed that the amine represented by (4-2) above was produced.

[0090] Example 6 In Example 6, an amine having the structure represented by (4-3) above was used as the amine of the second solid absorbent. The synthesis method was the same as that for the amine having the structure represented by (4-4) above, and the target product, presumably the amine having the structure represented by (4-3) above, was obtained in the same procedure as in Example 4 above, except that methyl isobutyl ketone was used instead of methyl ethyl ketone at the beginning. The yield was 97.9%.

[0091] Whether the obtained substance was the target amine having the structure represented by (4-3) above was confirmed as follows. 1H-NMR: Deuterated chloroform was used as the measurement solvent. Figure 6 shows the positions a to i of hydrogen atoms in the amine represented by (4-3), the target substance of Example 6, and the measured 1H-NMR chart. The 1H-NMR chart indicates which of the peaks a to i each corresponds to and the number of hydrogen atoms. As shown in Figure 6, the 1H-NMR chart confirmed that the amine represented by (4-3) above had been produced. GC and GCMS: The peaks of the product were confirmed by GC, and the product was subjected to mass analysis by GCMS, confirming the amine represented by (4-3) above.

[0092] Comparative Example 1 In this comparative example, diethanolamine (DEA) was used as the amine supported on the porous substrate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., boiling point: 217°C / 760 mmHg). DEA is a liquid chemical amine that is widely used as a liquid chemical substance supported on a substrate to reversibly absorb carbon dioxide.

[0093] [Porous Substrate] Silica gel described in Japanese Patent No. 6055134 was used as the porous substrate.

[0094] [Method for manufacturing a solid absorbent] First, about 300 mL of the porous substrate was collected and its mass was measured. Next, using water or ethanol as a solvent, an amine solution with a concentration of 45% by mass of each of the amines synthesized above in Examples 1 to 6 or the DEA of the comparative example was prepared, and the prepared solution was placed in a bottle. The porous substrate was then placed therein, and all of the porous substrates were immersed in the liquid and left at room temperature for 8 hours or more. Thereafter, the porous substrate was removed from the bottle and centrifuged (1100 rpm, 1 minute). After centrifugation, the porous substrate was filled into another container, and dry gas (nitrogen gas at 40 ° C., 15 L / min) was flowed, and the porous substrate carrying each of the amines or DEA of Examples 1 to 6 was aerated and dried. After 2 hours had elapsed from the time when the gas temperature at the outlet of the drying tank for drying the porous substrate carrying each amine, etc. stabilized, drying was terminated and the solvent was completely removed. In this way, porous substrates carrying each amine or DEA, that is, solid absorbents in Examples 1 to 6 and the Comparative Example, were obtained.

[0095] The saturated carbon dioxide absorption capacity and saturated water absorption capacity of the solid absorbents of the Examples and Comparative Examples produced by the above-mentioned methods were measured by the following methods.

[0096] [Method for measuring saturated carbon dioxide absorption (mol / kg) and saturated water absorption (mol / kg) per weight of solid absorbent] The saturated carbon dioxide absorption and saturated water absorption per weight of the solid absorbent in Examples 1 to 6 and Comparative Example were measured by the following method. First, a cylindrical container with a volume of 150 mL was filled with the solid absorbent produced by the above method. Next, nitrogen gas at 40°C was supplied to the cylindrical container at a rate of 50 L / min to remove carbon dioxide or water (H ２O) was desorbed. Thereafter, the initial weight of the container filled with the solid absorbent was measured, and then gases prepared to a predetermined composition containing carbon dioxide or moisture were supplied into the container at 50 L / min. Thereafter, the weight of the container was measured at regular intervals, and when the weight change almost stopped, it was determined that the carbon dioxide absorption or moisture absorption had reached saturation. Then, from the change in the weight of the container at the initial time and the time of saturation, the saturated carbon dioxide absorption amount (mol / kg) per weight of the solid absorbent or the saturated moisture absorption amount (mol / kg) per weight of the solid absorbent was calculated. Note that when measuring the saturated carbon dioxide absorption amount, a gas mixture of carbon dioxide and nitrogen gas was used. On the other hand, when measuring the saturated moisture absorption amount, a gas in which the humidity was adjusted by permeating nitrogen gas into water was used.

[0097] The measurement results of the saturated carbon dioxide absorption amount and saturated water absorption amount per weight of the solid absorbents of each Example and Comparative Example are shown in the graphs of FIGS.

[0098] As shown in Figure 7, the solid absorbents of Examples 1 to 6, which are the first or second solid absorbents of this embodiment, were able to absorb carbon dioxide at a rate equal to or greater than that of the solid absorbent of the comparative example. In addition, as shown in Figure 8, the solid absorbents of Examples 1 to 6 had significantly lower hygroscopicity than the solid absorbent of the comparative example. That is, the solid absorbents of Examples 1 to 6 have lower hygroscopicity than the solid absorbent of the comparative example, and therefore have better handling properties and can efficiently desorb carbon dioxide. These results demonstrate that the first and second solid absorbents of this embodiment have low hygroscopicity and can efficiently absorb carbon dioxide reversibly.

[0099] This application is based on Japanese Patent Application No. 2023-200852 filed on November 28, 2023, the contents of which are incorporated herein by reference.

[0100] The embodiments and examples disclosed herein should be understood to be illustrative in all respects and not restrictive. The scope of the present invention is defined by the claims, not by the above description, and is intended to include all modifications within the meaning and scope of the claims.

Claims

1. A solid absorbent that reversibly absorbs acidic gases, comprising a porous substrate and an acidic gas absorbing agent supported on the porous substrate, wherein the acidic gas absorbing agent contains at least one amine represented by any one of the following general formulas (1), (2) and (3): (In formulas (1), (2) and (3), R １ is a group: -(CH ２ ) ｌ -NH-[(CH ２ ) ２ N.H. ｍ - (CH ２ ) ｎ -CH ３ and R １ In the formula, l represents 1 or 2, and m and n each independently represent an integer of 0 to 2.

2. The solid absorbent material according to claim 1, wherein the amine has a structure represented by any one of the following (1-1), (1-2), (2-1) and (3-1).

3. A solid absorbent that reversibly absorbs acidic gases, comprising a porous substrate and an acidic gas absorbing agent supported on the porous substrate, wherein the acidic gas absorbing agent comprises at least one amine represented by the following general formula (4): (In formula (4), two R ２ The groups may be the same or different structures, p is 2 or 3, q ​​is an integer from 2 to 5, and R ２ is the following R ２ (1) ~ R ２ (9): is a group represented by any one of the following:

4. The solid absorbent material according to claim 3, wherein the amine has a structure represented by any one of the following (4-1) to (4-6).

5. A method for absorbing and desorbing acidic gases, comprising the steps of: bringing a gas to be treated into contact with the solid absorbent material described in any one of claims 1 to 4 to absorb the acidic gas; and bringing steam into contact with the solid absorbent material that has absorbed the acidic gas, thereby desorbing the acidic gas from the solid absorbent material.

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