Solid absorber and sour gas absorption and desorption method using the same

Abstract

To provide a solid absorber having low hygroscopic property and capable of efficiently absorbing a sour gas, especially reversibly absorbing carbon dioxide.SOLUTION: A solid absorber reversibly absorbs a sour gas and includes a porous base material and a sour gas absorption chemical agent carried with the porous base material. The sour gas absorption chemical agent includes at least one amine expressed as any one of general formula (1), (2) and (3). (In formula (1), (2) and (3), R1 is expressed as group:-(CH2)l-NH-[(CH2)2NH]m-(CH2)n-CH3 and in R1, l is expressed as 1 or 2 and m and n are independently expressed as an integer of 0-2.)SELECTED DRAWING: Figure 1

Description

Technical Field

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

Background Art

[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, blast furnaces in steel mills, converters in steel mills, and boilers are known. In addition, technologies for applying such solid absorbents to DAC (Direct Air Capture) for directly collecting these acidic gases, particularly carbon dioxide, from the atmosphere and the like have also been developed. Such solid absorbents generally comprise a porous substrate (e.g., porous particles) supporting an amine, which is a liquid chemical substance that reversibly absorbs acidic gases.

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

[0004] Further, 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., amine) supported on the porous particles. In the acidic gas absorbent described in Patent Document 2, the porous particles have a bimodal pore structure including mesopores having a pore diameter in the nanometer region of 2 nm or more and 200 nm or less, and macropores having a pore diameter in the micrometer region exceeding 0.2 μm, where the macropores are voids and the mesopores are filled with the acidic gas absorbent.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] Such a solid absorbent that reversibly absorbs acidic gas is generally used in an acidic gas separation system (especially a carbon dioxide separation system). Examples of the acidic gas separation system include systems such as a batch process system and a moving bed system (continuous process system). In these acidic gas separation systems, a step of allowing the solid absorbent to absorb the acidic gas and a step of desorbing the acidic gas from the solid absorbent using steam or the like (i.e., a step of regenerating the solid absorbent) are repeatedly performed. Therefore, the solid absorbent is required to efficiently absorb and desorb acidic gas, particularly carbon dioxide.

[0007] Also, in such an acidic gas separation system, if the solid absorbent absorbs excessive moisture, the solid absorbent exhibits adhesiveness and handling becomes poor. When the handling of the solid absorbent is poor, in a moving bed system involving the movement of the solid absorbent, the acidic gas absorption characteristics of the solid absorbent are significantly reduced. Also, in a batch process system, when the handling of the solid absorbent is poor, the replacement work of the solid absorbent becomes difficult. Therefore, it is preferable that the solid absorbent has low hygroscopicity.

[0008] Therefore, an object of the present invention is to provide a solid absorbent that has low hygroscopicity and can efficiently and reversibly absorb acidic gas, particularly carbon dioxide.

Means for Solving the Problems

[0009] As a result of intensive studies to solve the above problems, the present inventors have reached the present invention. That is, the present invention includes the following preferred aspects.

[0010] The solid absorbent according to the first aspect of the present disclosure is a solid absorbent that reversibly absorbs acidic gas, and It includes a porous substrate and an acidic gas absorption agent supported on the porous substrate. The acidic gas absorption agent contains at least one amine represented by any of the following general formulas (1), (2), and (3).

Chemical formula

[0011] Alternatively, another solid absorbent according to the first aspect of the present disclosure includes a porous substrate and an acidic gas absorption agent supported on the porous substrate. The acidic gas absorption agent contains at least one amine represented by the following general formula (4).

Chemical formula

Chemical formula

[0012] The method for absorbing and desorbing acidic gas according to the second aspect of the present disclosure includes a step of bringing the gas to be treated into contact with any one of the solid absorbents according to the first aspect and another solid absorbent according to the first aspect to absorb the acidic gas. And a step of desorbing the acidic gas from the solid absorbent by bringing steam into contact with the solid absorbent that has absorbed the acidic gas.

Advantages of the Invention

[0013] According to the present invention, it is possible to provide a solid absorbent that has low hygroscopicity and can efficiently and reversibly absorb acidic gas, particularly carbon dioxide.

Brief Description of the Drawings

[0014]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Mode for Carrying Out the Invention

[0015] The inventors have conducted various studies on solid absorbents that have low hygroscopicity and can efficiently and reversibly absorb acidic gases, particularly carbon dioxide. And it has been found that in a solid absorbent containing a porous substrate and an acidic gas absorbent carried on the porous substrate, such an effect can be exhibited when the acidic gas absorbent contains at least one amine represented by a predetermined general formula. It has also been found that the solid absorbent can desorb acidic gases using waste heat that is generally not effectively utilizable.

[0016] In this specification, "waste heat" means low-temperature thermal energy that is generally not effectively utilizable and is unavoidably generated from various manufacturing industries, power plants, etc., at 40°C or higher and 100°C or lower, and low-temperature thermal energy that is generally not effectively utilizable by sunlight, etc. Therefore, the solid absorbent in this embodiment is also excellent in terms of the environment.

[0017] In this specification, "acidic gas" generally means acidic gases such as carbon dioxide, NOx (nitrogen oxides), SOx (sulfur oxides), and HCl contained in combustion exhaust gases, the atmosphere, closed-space atmospheres, etc. Among these, from the viewpoint of exhibiting a good effect in terms of the environment, the acidic gas to be absorbed is preferably carbon dioxide.

[0018] 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.

[0019] 1. Solid absorbent The solid absorbent in the present embodiment will be described in detail below. In this specification, the "solid absorbent" means a solid absorbent that can reversibly absorb acidic gas. Further, in this specification, "can reversibly absorb acidic gas (particularly carbon dioxide)" means that acidic gas (particularly carbon dioxide) can be absorbed (or recovered) and desorbed (i.e., the solid absorbent is regenerated). The solid absorbent in the present embodiment includes a first solid absorbent and a second solid absorbent.

[0020] [First Solid Absorbent] The first solid absorbent includes a porous substrate and an acidic gas absorbent carried on the porous substrate. First, the acidic gas absorbent in the first solid absorbent will be described in detail below.

[0021] (Acidic Gas Absorbent) The acidic gas absorbent in the first solid absorbent contains at least one amine represented by any of the following general formulas (1), (2), and (3) (hereinafter, also referred to as "amine of the first solid absorbent"). [Chemical Formula]

[0022] In formulas (1), (2), and (3), R 1 is a group: -(CH 2 ) l -NH-[(CH 2 ) 2 NH] m -(CH 2 ) n -CH 3 represented by, and in R 1 , l represents 1 or 2, and m and n each independently represent an integer from 0 to 2.

[0023] R 1 In, it is preferable that l is 1. When l is 1, an amine of the first solid absorbent with a significantly stable structure can be obtained in a high yield, and ultimately the production efficiency of the solid absorbent can be improved.

[0024] R 1 In this case, m preferably represents 0 or 1. When m is 0 or 1, ultimately, a solid absorbent having good low hygroscopicity characteristics and capable of more efficiently desorbing acidic gas, particularly carbon dioxide, can be produced.

[0025] R 1 In this case, n preferably represents 0 or 1, and more preferably 0. When n is 0, ultimately, a solid absorbent capable of more efficiently and reversibly absorbing acidic gas, particularly carbon dioxide, can be produced.

[0026] The acidic gas absorbent in the first solid absorbent may be a mixture of two or more amines represented by any of the general formulas (1), (2), and (3) above, may contain a single amine among these, or may be a single amine among these.

[0027] More specifically, the amine of the first solid absorbent preferably has a structure represented by any of the following (1-1), (1-2), (2-1), and (3-1).

Chemical formula

[0028] When the amine of the first solid absorbent has a structure represented by any of the above, ultimately, a solid absorbent having good low hygroscopicity and capable of more efficiently and reversibly absorbing acidic gas, particularly carbon dioxide, can be produced.

[0029] The synthesis method of the amine of the first solid absorbent is not particularly limited, and it may be synthesized by any method known to those skilled in the art. For example, the amine of the first solid absorbent can be synthesized by the following method. Specifically, using benzaldehyde having a plurality of aldehyde groups as a starting material, a modified chain having an amine may be introduced by a reductive amination reaction.

[0030] 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 the method described in detail in the following examples.

[0031] The content of the amine of the first solid absorbent with respect to the total mass of the first solid absorbent is not particularly limited, but is preferably 10% by mass or more. When the content of the amine of the first solid absorbent is 25% by mass or more, the finally produced solid absorbent can absorb and desorb acidic gas, particularly carbon dioxide, more efficiently. The content of the amine of the first solid absorbent is more preferably 10% by mass or more, and even more preferably 25% by mass or more. Also, the upper limit value of the content of the amine of the first solid absorbent is not particularly limited, but is, for example, 50% by mass or less.

[0032] The acidic gas absorbent may be composed only of the amine of at least one of the above first solid absorbents, but may 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, polyethyleneimine, tetraethylenepentamine, amine-based or non-amine-based by-products inevitably contained during amine synthesis, and the like.

[0033] (Porous substrate) The porous substrate supports the acidic gas absorbent described above.

[0034] The type of the porous substrate is not particularly limited. Specifically, the porous substrate can be a substrate made of any material known to those skilled in the art that can support the above-described acidic gas absorbent and has a large number of pores that can be used to reversibly absorb acidic gas, particularly carbon dioxide.

[0035] Examples of the porous substrate include silica such as silica gel or mesoporous silica, alumina such as activated alumina, zeolite, titania, zirconia, magnesia, activated carbon, metal-organic framework (MOF), etc. The porous substrate may be in the form of powder. Further, the porous substrate may be formed by appropriately using a binder with the powder, and for example, it may be made granular (typically 1 mm to 5 mm) at the time of manufacturing the porous substrate.

[0036] (Method for manufacturing a solid absorbent) The first solid absorbent contains a porous substrate and an acidic gas absorbent carried on the porous substrate. A method for manufacturing the first solid absorbent will be described below.

[0037] (1) Preparation step of acidic gas absorbent solution First, at least one of the amines of the first solid absorbent contained in the acidic gas absorbent is dissolved in a solvent (water or alcohol) to prepare an acidic gas absorbent solution.

[0038] The temperature of the prepared acidic gas absorbent solution containing the amine 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 as the temperature rises, when the temperature of the acidic gas absorbent solution is 10°C or higher, the amine can be uniformly supported on the porous substrate. Also, when the temperature of the acidic gas absorbent solution is 100°C or lower, oxidation and / or evaporation of the amine can be suppressed.

[0039] The concentration of the amine of the first solid absorbent in the acidic gas absorbent solution is not particularly limited, but may be adjusted to an appropriate value in the range of 5% by mass or more and 70% by mass or less according to the type of the 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. Also, if the amine concentration of the first solid absorbent in the solution is too high, the amine may block the pores of the porous substrate, reducing the acidic gas absorption performance of the first solid absorbent.

[0040] (2) Impregnation process Next, a porous substrate (for example, the aforementioned porous particles) is put into an immersion container filled with an acidic gas absorption agent solution, and the porous substrate is impregnated with the acidic gas absorption 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. At this time, in order to shorten the immersion time, the acidic gas absorption agent solution may be stirred or ultrasonic vibration may be applied to the immersion container.

[0041] (3) Drying process Thereafter, the porous substrate is lifted from the acidic gas absorption agent solution, and the excess liquid adhering thereto is removed by a method such as suction filtration. Further, thereafter, the porous substrate impregnated with the acidic gas absorption agent solution is dried by air drying or vacuum drying at a temperature close to room temperature. After drying, the first solid absorbent can be obtained.

[0042] [Second solid absorbent] The second solid absorbent also includes a porous substrate and an acidic gas absorption agent supported on the porous substrate. First, the acidic gas absorption agent in the second solid absorbent will be described in detail below.

[0043] (Acidic gas absorption agent) The acidic gas absorption agent 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").

Chemical formula

[0044] In formula (4), the two R 2 groups may have the same or different structures, p represents 2 or 3, q represents an integer from 2 to 5, and R 2 is the following R 2 (1) to R 2 (9):

Chemical formula

[0045] In this specification, "the two Rs 2 groups may have the same or different structures" means that the two R 2 groups at the ends in the above general formula (4) may be the same group represented by any of the above R 2 (1) to R 2 (9), or may be different groups represented by any of the above R 2 (1) to R 2 (9).

[0046] p is preferably 3. When p is 3, ultimately, a solid absorbent having good low hygroscopicity characteristics and capable of more efficiently desorbing acidic gases, particularly carbon dioxide, can be produced.

[0047] q preferably represents 2 or 3, and more preferably 2. When q is 2, ultimately, a solid absorbent having good low hygroscopicity and capable of more efficiently and reversibly absorbing acidic gases, particularly carbon dioxide, can be produced.

[0048] The acidic gas absorbent in the second solid absorbent may be a mixture of two or more amines represented by the above general formula (4), may contain a single amine among them, or may be a single amine among them.

[0049] More specifically, the amine of the second solid absorbent preferably has a structure represented by any of the following (4-1) to (4-6).

Chemical formula

[0050] When the amine of the second solid absorbent has a structure represented by any of the above, ultimately, a solid absorbent having good low hygroscopicity and capable of more efficiently and reversibly absorbing acidic gases, particularly carbon dioxide, can be produced.

[0051] Furthermore, the amine of the second solid absorbent preferably has a structure represented by any one of the above (4-1) to (4-3). When the amine of the second solid absorbent has a structure represented by any one of the above (4-1) to (4-3), ultimately, a solid absorbent with better and more reliable low hygroscopicity and more efficient reversible absorption of acidic gases, particularly carbon dioxide, can be produced.

[0052] The synthesis method of the amine of the second solid absorbent is not particularly limited, and it may be synthesized by any method known to those skilled in the art. 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 a group -NH or a polyamine having a group -NH obtained by any method known to those skilled in the art through a reaction known to those skilled in the art, such as an addition reaction of an alkyl halide or a reaction by reductive amination of a ketone and a terminal amino group.

[0053] More specifically, for example, the amine of the second solid absorbent having a structure represented by any one of the above (4-1), (4-2), and (4-3) can be synthesized by the method described in detail in the following examples.

[0054] 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.

[0055] The acidic gas absorbent may be composed only of the amine of at least one of the above second solid absorbents, but as long as the effect of the second solid absorbent in this embodiment is achieved, other compounds may be included as in the case of the first solid absorbent described above.

[0056] Details of the manufacturing method of the porous base material and the solid absorbent in the second solid absorbent are also the same as those of the first solid absorbent described above.

[0057] As described above, the first and second solid absorbents in the present embodiment have the property of low hygroscopicity and can efficiently and reversibly absorb acid gas, particularly carbon dioxide. Further, the first and second solid absorbents in the present embodiment are excellent in terms of the environment because they can desorb acid gas from the solid absorbent using waste heat that is generally not effectively utilizable.

[0058] 2. Method for Absorbing and Desorbing Acid Gas The method for absorbing and desorbing acid gas (particularly carbon dioxide) in the present embodiment includes a step of bringing the gas to be treated into contact with the first or second solid absorbent in the above-described embodiment to absorb the acid gas, and a step of desorbing the acid gas from the solid absorbent by bringing steam into contact with the solid absorbent that has absorbed the acid gas.

[0059] In this specification, the "gas to be treated" is not particularly limited as long as it is a gas containing acid gas, particularly carbon dioxide. Examples of such gases include combustion exhaust gases discharged from combustion facilities such as thermal power plants using coal, heavy oil, natural gas, etc. as fuel, blast furnaces in steel mills that reduce iron oxide with coke, converters in steel mills that burn carbon in pig iron to produce steel, boilers in various manufacturing plants, etc., and gases discharged from transportation equipment such as automobiles, ships, and airplanes using gasoline, heavy oil, light oil, etc. as fuel. Further, as other examples of the gas to be treated, the atmosphere containing acid gas, particularly carbon dioxide, the breathing of people in enclosed spaces such as submersible survey ships and space stations, and the ambient atmosphere containing carbon dioxide discharged during energy conversion of equipment, etc. can also be mentioned.

[0060] The acid gas content and temperature in the gas to be treated are not particularly limited as long as they are conditions under which the first or second solid absorbent in the above-described embodiment can absorb the acid gas when they come into contact. For example, when the acid 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.

[0061] For example, when the acid gas is carbon dioxide, in the step of desorbing carbon dioxide, carbon dioxide may be desorbed by contacting a solid absorbent with steam at, for example, 50°C or higher, in any method known to those skilled in the art. Further, from the viewpoint of efficiently desorbing carbon dioxide, in the step of desorbing carbon dioxide, it is preferable to contact 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.

[0062] On the other hand, as described in the foregoing embodiments, the first and second solid absorbents that have absorbed the acid gas can desorb the acid gas even by using waste heat that is generally not effectively utilizable. Therefore, in the step of desorbing the acid gas, from the viewpoint of being excellent in environmental aspects, it is preferable to desorb the acid gas from the solid absorbent by contacting it with low-temperature steam generated by waste heat. For example, when the acid gas is carbon dioxide, the temperature of the waste heat is preferably 40°C or higher and 100°C or lower, and more preferably 50°C or higher and 70°C or lower.

[0063] By adopting the method in this embodiment, for example, in a medium-scale or large-scale acid gas separation system (especially a carbon dioxide separation system), a system that is excellent in environmental aspects and can efficiently absorb and desorb acid gas (especially carbon dioxide) from exhaust gas can be achieved.

[0064] [Summary of the Present Disclosure] The specific embodiments described above include the following disclosures.

[0065] The solid absorbent according to the first aspect of the present disclosure is a solid absorbent that reversibly absorbs an acid gas, including a porous substrate and an acid gas absorbent carried on the porous substrate, wherein the acid gas absorbent contains at least one amine represented by any one of the following general formulas (1), (2), and (3). [Chemical formula] (In formulas (1), (2), and (3), R 1 is a group: -(CH 2 ) l -NH-[(CH 2 ) 2 NH] m -(CH 2 ) n -CH 3 represented by, and in R 1 , l represents 1 or 2, and m and n each independently represent an integer from 0 to 2.)

[0066] The above solid absorbent has low hygroscopicity and can efficiently and reversibly absorb acidic gases, particularly carbon dioxide.

[0067] In the above solid absorbent, the amine preferably has a structure represented by any one of the following (1-1), (1-2), (2-1), and (3-1). [Chemical formula]

[0068] The above solid absorbent has good low hygroscopicity and can more efficiently and reversibly absorb acidic gases, particularly carbon dioxide.

[0069] Alternatively, another solid absorbent according to the first aspect of the present disclosure is a solid absorbent that reversibly absorbs acidic gases, and includes a porous substrate and an acidic gas absorbent carried on the porous substrate, The acidic gas absorbent includes at least one amine represented by the following general formula (4). [Chemical formula] (In formula (4), the two R 2 groups may have the same or different structures, p represents 2 or 3, q represents an integer from 2 to 5, and R 2 is the following R2 (1) to R 2 (9):

Chemical

[0070] The above solid absorbent has low hygroscopicity and can efficiently and reversibly absorb acidic gases, particularly carbon dioxide.

[0071] In the above solid absorbent, the amine preferably has a structure represented by any one of the following (4-1) to (4-6).

Chemical

[0072] The above solid absorbent has good low hygroscopicity and can more efficiently and reversibly absorb acidic gases, particularly carbon dioxide.

[0073] The method for absorbing and desorbing acidic gas according to the second aspect of the present disclosure includes a step of bringing the gas to be treated into contact with any one of the solid absorbent according to the first aspect and another solid absorbent according to the first aspect to absorb the acidic gas, and a step of desorbing the acidic gas from the solid absorbent by bringing steam into contact with the solid absorbent that has absorbed the acidic gas.

[0074] According to the above method, since the solid absorbent has low hygroscopicity, it is possible to prevent a decrease in the handling performance of the solid absorbent in, for example, a moving bed type and a batch process type acidic gas separation system.

Examples

[0075] Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited by the examples at all.

[0076] In this example, the first and second solid absorbents in this embodiment were actually manufactured, and the carbon dioxide saturation absorption amount (kg / m 3 ) and the moisture saturation absorption amount (kg / m 3 ) of the manufactured solid absorbent were measured.

[0077] First, the synthesis method of the amine (i.e., the acid gas absorbent) of the solid absorbent used in each example and comparative example, the porous substrate used, and the manufacturing method of the solid absorbent will be described in detail below. In addition, for the confirmation of the target amine, except for Example 5, a proton nuclear magnetic resonance (1H-NMR) apparatus (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) apparatus (manufactured by Shimadzu Corporation, "GC / MS QP-2010Plus") were used.

[0078] [Synthesis Method of Amine in Solid Absorbent] (Example 1) In Example 1, the amine having the structure represented by the above (1-1), which is the amine of the first solid absorbent, was used. The synthesis method will be described in detail below.

[0079] First, 1,3,5-benzenetricarboxaldehyde (reference substance) was added to an ethanol solution of N-Boc-methylethylenediamine, and the added solution was heated and stirred at 90 °C for 1.5 hours. Then, the reaction solution was cooled to around 0 °C, and a reducing agent was added to reduce the imine. Next, the lipophilic component was recovered from the reactant in which the imine was reduced by liquid-liquid extraction separation using chloroform and water. Then, the protecting group of the imine was removed by adding trifluoroacetic acid, and the target substance assumed to be the amine having the structure represented by the above (1-1) was obtained as a yellow oily substance from the recovered lipophilic component. The yield was 54.6%.

[0080] Whether the obtained substance was the amine having the structure represented by the above (1-1) of the target substance was confirmed as follows. 1H-NMR: Ethanol-d6 was used as the measurement solvent. Figure 1 shows the positions a to e of hydrogen in the amine represented by the above (1-1), which is the target product of Example 1, and the measured 1H-NMR chart. The 1H-NMR chart shows which of the peaks a to e each peak corresponds to and the number of hydrogens. As shown in Figure 1, it was confirmed from the 1H-NMR chart that the amine represented by the above (1-1) was generated. GC and GCMS: The peaks of the product were confirmed by GC, and the mass spectrometry of the product was performed by GCMS to confirm the amine represented by the above (1-1).

[0081] (Example 2) In Example 2, an amine having the structure represented by the above (2-1), which is the amine of the first solid absorbent, was used. The synthesis method will be described in detail below.

[0082] First, isophthalaldehyde (reference substance) was dissolved in toluene, an aqueous solution of methylamine was further added to the solution, and the mixture was stirred 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. Then, the obtained intermediate substance was 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 a target product assumed to be an amine having the structure represented by the above (2-1) was obtained as a brown oily substance. The yield was 83.3%.

[0083] Whether the obtained substance was an amine having the structure represented by the above (2-1) as the target product was confirmed as follows. 1H-NMR: As the measurement solvent, deuterated dimethyl sulfoxide was used. Figure 2 shows the positions a to e of hydrogen in the amine represented by the above (2-1), which is the target product of Example 2, and the measured 1H-NMR chart. The 1H-NMR chart shows which of the peaks a to e each corresponds to and the number of hydrogens. As shown in Figure 2, it was confirmed from the 1H-NMR chart that the amine represented by the above (2-1) was generated. GC and GCMS: The peaks of the product were confirmed by GC, and the mass spectrometry of the product was performed by GCMS to confirm the amine represented by the above (2-1).

[0084] (Example 3) In Example 3, an amine having the structure represented by the above (3-1), which is the amine of the first solid absorbent, was used. The synthesis method was the same as that of Example 2 except that terephthalaldehyde (reference substance) was used instead of isophthalaldehyde as the starting material, and a target product assumed to be an amine having the structure represented by the above (3-1) was obtained. The yield was 67.9%.

[0085] Whether the obtained substance was an amine having the structure represented by the above (3-1) of the target product was confirmed as follows. 1H-NMR: As the measurement solvent, deuterated dimethyl sulfoxide was used. Figure 3 shows the positions a to c of hydrogen in the amine represented by the above (3-1), which is the target product of Example 3, and the measured 1H-NMR chart. The 1H-NMR chart shows which of the peaks a to c each corresponds to and the number of hydrogens. As shown in Figure 3, it was confirmed from the 1H-NMR chart that the amine represented by the above (3-1) was generated. GC and GCMS: The peaks of the product were confirmed by GC, and the mass spectrometry of the product was performed by GCMS to confirm the amine represented by the above (3-1).

[0086] (Example 4) In Example 4, an amine having the structure represented by the above (4-4), which is the amine of the second solid absorbent, was used. The synthesis method will be described in detail below.

[0087] First, 3,3-diaminodipropylamine (reference substance), methyl ethyl ketone, and palladium carbon were charged into an autoclave, and ethanol was added thereto to homogenize the mixture. Then, the mixture was filled with hydrogen gas at 0.9 MPa. Next, the mixture was heated at 50 °C for 90 hours. Thereafter, the reaction solution was filtered, and further, the solvent was removed to obtain a target substance assumed to be an amine having the structure represented by the above (4-4) as a yellow oily substance. The yield was 99.6%.

[0088] Whether the obtained substance was an amine having the structure represented by the above (4-4) of the target substance was confirmed as follows. 1H-NMR: As the measurement solvent, deuterated chloroform was used. Fig. 4 shows the positions a to g of the hydrogen present in the amine represented by the above (4-4), which is the target substance of Example 4, and the measured 1H-NMR chart. The 1H-NMR chart shows which of a to g each peak corresponds to and how many hydrogens there are. As shown in Fig. 4, it was confirmed from the 1H-NMR chart that the amine represented by the above (4-4) was generated. GC and GCMS: The peak of the product was confirmed by GC, and the mass spectrometry of the product was performed by GCMS to confirm the amine represented by the above (4-4).

[0089] (Example 5) In Example 5, an amine having the structure represented by the above (4-2), which is the amine of the second solid absorbent, was used. The synthesis method was the same as that of the amine having the structure represented by the above (4-4). A target substance assumed to be an amine having the structure represented by the above (4-2) was obtained in the same procedure as in Example 4 above, except that diethyl ketone was used instead of methyl ethyl ketone at first. The yield was 73.5%.

[0090] Whether the obtained substance was an amine having the structure represented by the above (4-2) of the target substance was confirmed as follows. 1H-NMR: 1H-NMR was carried out using a nuclear magnetic resonance apparatus (manufactured by Bruker, "BRUKER NMR 400MHz"). CDCl3 (20 - 40 mg / mL) was used as the solvent. The measured 1H-NMR chart is shown in Figure 5. From the 1H-NMR chart shown in Figure 5, it was confirmed that the amine represented by the above (4-2) was generated.

[0091] (Example 6) In Example 6, an amine having the structure represented by the above (4-3), which is the amine of the second solid absorbent, was used. The synthesis method was the same as that of the amine having the structure represented by the above (4-4). A target substance assumed to be an amine having the structure represented by the above (4-3) was obtained in the same procedure as in Example 4 above, except that methyl isobutyl ketone was used instead of methyl ethyl ketone first. The yield was 97.9%.

[0092] Whether the obtained substance was an amine having the structure represented by the above (4-3) of the target substance was confirmed as follows. 1H-NMR: Deuterated chloroform was used as the measurement solvent. Figure 6 shows the positions a - i of the hydrogen atoms in the amine represented by the above (4-3), which is the target substance of Example 6, and the measured 1H-NMR chart. The 1H-NMR chart shows which of the peaks a - i each peak corresponds to and the number of hydrogen atoms. As shown in Figure 6, it was confirmed from the 1H-NMR chart that the amine represented by the above (4-3) was generated. GC and GCMS: The peaks of the product were confirmed by GC, and mass spectrometry of the product was carried out by GCMS to confirm the amine represented by the above (4-3).

[0093] (Comparative Example 1) In the comparative example, diethanolamine (DEA) (manufactured by FUJIFILM Wako Pure Chemical Corporation, boiling point: 217 °C / 760 mmHg) was used as the amine supported on the porous substrate. DEA is widely used as an amine, which is a liquid chemical substance for reversibly absorbing carbon dioxide by being supported on a substrate.

[0094] [Porous substrate] As the porous substrate, silica gel described in Patent No. 6055134 was used.

[0095] [Method for manufacturing solid absorbent] First, about 300 mL of the above-mentioned 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 amine of Examples 1 to 6 synthesized above or DEA of the comparative example was prepared, and the prepared solution was put into a bottle. The porous substrate was put into this, and while immersing all the porous substrates in the liquid, it was left at room temperature for 8 hours or more. Then, the porous substrate was taken out from the bottle and centrifuged (1100 rpm, 1 minute). After centrifugation, the porous substrate was filled into another container, and a drying gas (nitrogen gas at 40 °C, 15 L / min) was passed through to aerodynamically dry the porous substrates supporting each amine of Examples 1 to 6 or DEA. Drying was terminated 2 hours after the gas temperature at the outlet of the drying tank for drying the porous substrates supporting each amine etc. became stable, and the solvent was completely removed. In this way, porous substrates supporting each amine or DEA, that is, solid absorbents in Examples 1 to 6 and the comparative example were obtained.

[0096] The carbon dioxide saturation absorption amount and water saturation absorption amount of the solid absorbents of each example and comparative example manufactured by the above method were measured by the following method.

[0097] [Method for measuring carbon dioxide saturation absorption amount (mol / kg) and water saturation absorption amount (mol / kg) per unit weight of solid absorbent] The carbon dioxide saturation absorption amount and moisture saturation absorption amount per unit weight of the solid absorbent in Examples 1 to 6 and the 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 50 L / min to desorb carbon dioxide or moisture (H 2

[0098]

[0099] O) that had been previously absorbed by the solid absorbent. After that, after measuring the initial weight of the container filled with the solid absorbent, a gas prepared to each predetermined composition containing carbon dioxide or moisture was supplied into the container at 50 L / min. Then, the weight of the container was measured at regular intervals, and when the change almost disappeared, it was determined that the absorption of carbon dioxide or moisture had reached saturation. Then, from the weight change of the container at the initial and saturation times, the carbon dioxide saturation absorption amount (mol / kg) per unit weight of the solid absorbent or the moisture saturation absorption amount (mol / kg) per unit weight of the solid absorbent was calculated. When measuring the carbon dioxide saturation absorption amount, a gas obtained by mixing carbon dioxide and nitrogen gas was used. On the other hand, when measuring the moisture saturation absorption amount, a gas with adjusted humidity was used by permeating nitrogen gas into water. The measurement results of the carbon dioxide saturation absorption amount and moisture saturation absorption amount per unit weight of the solid absorbents in each example and the comparative example are shown in the graphs of FIGS. 7 and 8. As shown in FIG. 7, the solid absorbents of Examples 1 to 6, which are the first or second solid absorbents in the present embodiment, were able to absorb carbon dioxide equal to or more than the solid absorbent of the comparative example. In addition, as shown in FIG. 8, the solid absorbents of Examples 1 to 6 had significantly lower hygroscopicity compared to the solid absorbent of the comparative example. That is, the solid absorbents of Examples 1 to 6 had good handling due to their lower hygroscopicity compared to the solid absorbent of the comparative example, and thus were able to desorb carbon dioxide efficiently. From these results, it was found that the first and second solid absorbents in the present embodiment have low hygroscopicity and can reversibly absorb carbon dioxide efficiently.

Claims

1. A solid absorbent for reversibly absorbing acid gas, comprising a porous substrate and an acid gas absorbent carried on the porous substrate, wherein the acid gas absorbent contains at least one amine represented by any one of the following general formulas (1), (2), and (3): a solid absorbent. 【Chemical 1】 (In formulas (1), (2) and (3), R １ represents a group: -(CH ２ ) ｌ -NH-[(CH ２ ) ２ NH] ｍ -(CH ２ ) ｎ -CH ３ and in R １ , l represents 1 or 2, and m and n each independently represent an integer from 0 to 2.)

2. The solid absorbent 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). 【Chemical Formula 2】

3. A solid absorbent for reversibly absorbing acid gas, comprising a porous substrate and an acid gas absorbent carried on the porous substrate, wherein the acid gas absorbent contains at least one amine represented by the following general formula (4): a solid absorbent. [Chemical Formula 3] (In formula (4), the two Rs ２ groups may have the same or different structures, p represents 2 or 3, q represents an integer from 2 to 5, and R ２ is the following R ２ (1) to R ２ (9): 【Chemical Formula 4】 It is a group represented by any one of them.)

4. The solid absorbent according to Claim 3, wherein the amine has a structure represented by any one of the following (4-1) to (4-6). 【Chemical Formula 5】

5. A step of bringing the gas to be treated into contact with the solid absorbent according to any one of Claims 1 to 4 to absorb the acid gas, and a step of desorbing the acid gas from the solid absorbent by bringing steam into contact with the solid absorbent that has absorbed the acid gas: a method for absorbing and desorbing acid gas.

Images