Adsorbent

Abstract

The present invention provides a solid adsorbent which can efficiently recover an acidic gas and can increase the amount of acidic gas recovered. This adsorbent contains an inorganic porous body and an amine compound, wherein the inorganic porous body has a peak diameter of pores of 20-100 nm as determined on the basis of a nitrogen adsorption method, and has an oil absorption amount of at least 230 ml / 100 g or a pore volume of 1.2-3.5 cm3 / g.

Description

[Technical Field]

[0001] The present invention relates to an adsorbent, and more particularly to a solid adsorbent that adsorbs acidic gases contained in a gas to be treated, especially carbon dioxide. [Background technology]

[0002] In recent years, the separation and capture of carbon dioxide, a greenhouse gas, has attracted attention as a measure against global warming, and methods for separating carbon dioxide from exhaust gases emitted from automobiles and factories, as well as from the atmosphere, are being developed.

[0003] Among the currently proposed technologies for separating and recovering carbon dioxide, the wet chemical absorption method, which involves absorbing carbon dioxide in an aqueous amine solution, is common. While this chemical absorption method using an aqueous amine solution can process large amounts of carbon dioxide, it has handling problems, such as being unsuitable for directly treating high-temperature gases. Furthermore, the regeneration of the amine solution that has absorbed carbon dioxide consumes a large amount of energy, resulting in high processing costs.

[0004] Therefore, in recent years, attention has been focused on the development of solid adsorption methods using solid adsorbents, which are a dry chemical absorption method. Solid adsorbents are made by imparting carbon dioxide adsorption capacity to the pore surface of a porous material, and can be obtained, for example, by immobilizing amines on a porous material. Compared to aqueous amine solutions, solid adsorbents have lower toxicity, corrosiveness, and flammability, making them safe, easy to handle, and environmentally friendly materials. Furthermore, since they can adsorb carbon dioxide with low energy, cost reductions can also be expected.

[0005] Various solid adsorbents have been proposed for use in such solid adsorption methods. For example, Patent Document 1 describes a solid adsorbent with a particle size of 1 mm to 5 mm, an average pore size of 10 nm to 100 nm, and a pore volume of 0.1 cm³. 3 / g or more 1.3cm 3A carbon dioxide adsorbent is proposed which is obtained by supporting an amine compound on silica gel having a specific surface area of 50 m 2 / g or more and 1000 m 2 / g or less, and having a pore volume of 0.1 cm 3 / g to 2.3 cm 3 / g. Further, Non-Patent Document 1 states that the amount of carbon dioxide adsorbed depends on the amount of the amine compound supported on the solid adsorbent.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Non-Patent Documents

[0007]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0008] However, conventional solid adsorbents have a problem that their carbon dioxide adsorption capacity is not sufficient. The demand for adsorbents for treating acidic gases such as carbon dioxide is on the increase, and new adsorbents that can increase the recovery amount of acidic gases are required. Therefore, an object of the present invention is to provide a solid adsorbent that can efficiently recover acidic gases and increase the recovery amount of acidic gases.

Means for Solving the Problems

[0009] As a result of diligent research, the inventors of the present invention have found that the above problem can be solved by using an inorganic porous material having a specific range of pore diameters and an oil absorption amount or pore volume within a specific range for adsorbing amines, and have completed the present invention.

[0010] The present invention relates to the following (1) to (12). (1) An adsorbent comprising an inorganic porous body and an amine compound, wherein the inorganic porous body has an oil absorption capacity of 230 ml / 100 g or more, and the peak diameter of the pore size determined by the nitrogen adsorption method is 20 nm or more and 100 nm or less. (2) A material containing an inorganic porous body and an amine compound, wherein the inorganic porous body has a pore volume of 1.2 cm³. 3 / g or more 3.5cm 3 An adsorbent having a concentration of less than or equal to / g, and a peak pore diameter determined by the nitrogen adsorption method being between 20nm and 100nm. (3) The adsorbent according to (1) or (2) above, wherein the adsorbent is an adsorbent that adsorbs carbon dioxide. (4) The adsorbent according to any one of (1) to (3) above, wherein the average pore size determined by the nitrogen adsorption method of the inorganic porous body is 15 nm or more and 100 nm or less. (5) The adsorbent according to any one of (1) to (4) above, wherein the nitrogen atom content in the adsorbent is 1N% or more and 40N% or less by mass ratio. (6) The adsorbent according to any one of (1) to (5) above, wherein the inorganic porous body comprises at least one selected from the group consisting of silica, zeolite, alumina, silica alumina, activated carbon, titania, silica gel, aluminum silicate, magnesium silicate, and clay minerals. (7) The adsorbent according to any one of (1) to (6) above, wherein the amine compound is an amine compound containing silicon in its molecule or a polyamine compound containing three or more amino groups in its molecule. (8) The adsorbent according to any one of (1) to (7), wherein the amine compound is fixed to at least one of the surface and the inner surface of the pores of the inorganic porous body. (9) The adsorbent according to any one of (1) to (7), wherein the amine compound is filled in the pores of the inorganic porous body. (10) The adsorbent according to any one of (1) to (9), wherein the inorganic porous body is in the form of a powder with an average particle size of 1 μm to 1 mm. (11) The adsorbent according to (10), wherein the inorganic porous body is spherical with a circularity of 0.8 or more. (12) The adsorbent according to any one of (1) to (9) above, wherein the inorganic porous body is a molded body with a maximum diameter of 1 mm to 50 mm. [Effects of the Invention]

[0011] According to the present invention, the amount of acidic gas recovered can be increased. Therefore, acidic gases, especially carbon dioxide, contained in exhaust gases emitted from automobiles and factories, as well as in the atmosphere, can be efficiently recovered, thereby reducing the costs associated with the separation and recovery of acidic gases. Furthermore, since it is a solid adsorbent, it is easy to handle and safe to use. [Modes for carrying out the invention]

[0012] The present invention will be described below, but the present invention is not limited by the examples in the following description. In this specification, "mass" is synonymous with "weight."

[0013] (Adsorbent material) The adsorbent of the present invention can adsorb a wide range of acidic gases. Examples of acidic gases include carbon dioxide, sulfur oxides (sulfur dioxide, sulfur trioxide, etc.), nitrogen oxides (NO, NO2, NO3, etc.), and hydrogen chloride. The adsorbent of the present invention is particularly suitable for adsorbing carbon dioxide.

[0014] The adsorbent of the present invention contains an inorganic porous material and an amine compound. The inorganic porous material has an oil absorption capacity of 230 ml / 100 g or more, and the peak diameter of the pore size determined by the nitrogen adsorption method is between 20 nm and 100 nm. Alternatively, the inorganic porous body has a pore volume of 1.2 cm 3 / g or more and 3.5 cm 3 / g or less, and the peak diameter of the pore diameter determined based on the nitrogen adsorption method is 20 nm or more and 100 nm or less. The inorganic porous body used in the present invention has a sufficiently large oil absorption amount or pore volume, and in addition, a sufficiently large pore diameter. By using an inorganic porous body having an oil absorption amount or pore volume within the above range and a pore diameter within the above range, an amine compound necessary for adsorbing an acidic gas can be sufficiently supported, and the acidic gas easily enters the pores of the adsorbent, and its diffusibility is also improved. Therefore, it is presumed that the recovery amount of the acidic gas can be improved.

[0015] The inorganic porous body has pores, and an amine compound can be supported on the surface and inside the pores of the inorganic porous body. Examples of the material constituting the inorganic porous body include silica, zeolite, alumina, silica alumina, activated carbon, titania, silica gel, aluminum silicate, magnesium silicate, clay minerals, and the like. The inorganic porous body only needs to contain at least one selected from the group consisting of these, and among them, it is more preferable to contain at least one selected from the group consisting of silica, zeolite, and alumina.

[0016] The inorganic porous body has an oil absorption amount of 230 ml / 100 g or more. The oil absorption amount affects the supported amount of the amine compound. When the oil absorption amount is large, more amine compounds can be supported in the pores, and the adsorption amount of the acidic gas can be increased. The oil absorption amount is preferably 270 ml / 100 g or more, more preferably 280 ml / 100 g or more, still more preferably 300 ml / 100 g or more, and the upper limit is preferably 1000 ml / 100 g or less, more preferably 800 ml / 100 g or less, and still more preferably 600 ml / 100 g or less.

[0017] Here, the amount of oil absorbed can be measured in accordance with JIS K 5101. Specifically, boiled linseed oil is added to the sample while kneading it until the entire sample forms a single mass. The amount of oil absorbed is expressed as the volume of boiled linseed oil per 100g of the sample when the entire sample forms a single mass. Hereafter, the amount of oil absorbed by this measurement method will simply be referred to as the amount of oil absorbed.

[0018] The inorganic porous material has a pore volume of 1.2 cm³. 3 / g or more 3.5cm 3 It is less than / g. Pore volume affects the amount of amine compound that can be supported in an inorganic porous material and the strength of the inorganic porous material. The larger the pore volume, the more amine compound can be supported, and a pore volume of 1.2 cm³ is... 3 If the pore volume is greater than or equal to 3.5 cm³, the amount of acidic gas adsorbed can be increased. Furthermore, if the pore volume becomes too large, the strength of the inorganic porous material decreases, making it impossible to maintain the strength required for an adsorbent. Therefore, the pore volume of the inorganic porous material should be 3.5 cm³. 3 The amount should be less than or equal to / g. The pore volume of the inorganic porous material is 1.3 cm³. 3 It is preferable that it be 1.6 cm or more. 3 More preferably 1.7cm or more per gram. 3 More preferably 3.5cm or more, and also 3.5cm 3 It is less than / g and 3.4cm 3 Preferably less than / g, and 3.3cm 3 Less than / g is preferable.

[0019] Pore ​​volume is measured by obtaining an adsorption isotherm using the nitrogen adsorption method, and then measuring the amount of nitrogen gas adsorbed when the relative pressure (adsorption equilibrium pressure / saturated vapor pressure) is 0.95 (BET method). Furthermore, the pore volume of relatively large pores with a diameter of 0.02 μm or more can be measured using a mercury porosimeter. When an inorganic porous material is a molded body formed from a powdered inorganic porous material, voids with a diameter of 0.02 μm or more may form between the particles. Pores and other structures resulting from such voids can be measured using a mercury porosimeter. The pore volume of an inorganic porous material is 3.5 cm³ even when measured using a mercury porosimeter. 3 It is less than / g.

[0020] Furthermore, the inorganic porous material has a peak pore diameter of 20 nm to 100 nm, determined based on the nitrogen adsorption method. The peak pore diameter affects the diffusivity of acidic gases and the strength of the inorganic porous material. A larger peak diameter indicates that there are larger pore spaces on the surface and inside the inorganic porous material, improving the diffusivity of acidic gases. A peak diameter of 20 nm or more can increase the amount of acidic gas adsorbed. However, if the peak diameter becomes too large, the strength of the inorganic porous material decreases, making it impossible to maintain the strength required for an adsorbent. Therefore, the peak pore diameter should be 100 nm or less. The peak diameter of the pore size of the inorganic porous material is 20 nm or more, preferably 24 nm or more, more preferably 30 nm or more, and 100 nm or less, preferably 70 nm or less, and more preferably 60 nm or less.

[0021] The peak diameter of the pore size is determined from the pore size that gives the peak top when the pore volume is plotted against the pore size as a pore diameter distribution curve obtained by the nitrogen adsorption method.

[0022] The inorganic porous material used in this invention preferably has an average pore diameter of 15 nm or more and 100 nm or less, as determined by the nitrogen adsorption method. The average pore diameter affects the diffusivity of acidic gases and the strength of the inorganic porous material. The larger the average pore diameter, the more pore spaces of an appropriate size (width) exist on the surface and inside the inorganic porous material, thus improving the diffusivity of acidic gases. An average pore diameter of 15 nm or more can increase the amount of acidic gases adsorbed. However, if the average pore diameter becomes too large, the strength of the inorganic porous material decreases, and it becomes impossible to maintain the strength required for an adsorbent. Therefore, it is preferable to keep the average pore diameter of the inorganic porous material at 100 nm or less. The average pore size of the inorganic porous material is preferably 15 nm or more, more preferably 18 nm or more, even more preferably 23 nm or more, and also preferably 100 nm or less, more preferably 50 nm or less, and even more preferably 40 nm or less.

[0023] The average pore size of an inorganic porous material can be calculated by using the specific surface area (S) of the sample, which is determined based on the adsorption isotherm obtained by the nitrogen adsorption method, and the pore volume (V) of the sample, using the formula: D = 4V / S [wherein D represents the average pore size (average pore diameter) of the sample, V represents the pore volume of the sample, and S represents the specific surface area of ​​the sample].

[0024] The inorganic porous material has a specific surface area of ​​1 m² determined by the nitrogen adsorption method. 2 / g or more 1000m 2 It is preferable that the specific surface area is less than or equal to / g. The specific surface area affects the density of amine compounds per unit area and the diffusivity of acidic gases. A specific surface area of ​​1000m 2 When the specific surface area is less than 1 m², the density of the amine compound supported on the inorganic porous material increases, causing the amino groups of the amine compounds to come into close proximity and bond with the acidic gas, thereby increasing the adsorption capacity of the acidic gas. In addition, the number of very fine pores is reduced, and the pore space within the inorganic porous material is of an appropriate size (width), improving the diffusivity of the acidic gas and making adsorption easier. If the specific surface area is too large, cracking may occur during the drying process to prepare the inorganic porous material. 2 When the amount is greater than / g, it can exhibit the ability to adsorb acidic gases. The specific surface area of ​​an inorganic porous material is 1 m². 2 Preferably 50m / g or more. 2 More preferably 100m / g or more, 2 More preferably 1000m 2 Preferably less than / g, 800m 2 Less than / g is more preferable, 500m 2 A value of less than / g is even more preferable.

[0025] The specific surface area can be calculated using BET's theory after obtaining adsorption isotherms by the nitrogen adsorption method.

[0026] The shape of the inorganic porous material is not particularly limited, and may be any shape, such as powder, granules, plate, block, or thin film. However, considering the filling efficiency into the separation and recovery device, gas resistance, strength, etc., it is preferable to have a powder or granular shape.

[0027] Furthermore, the inorganic porous material may be primary particles, secondary particles (aggregates) formed by the aggregation of primary particles, or a molded body obtained by granulating primary and / or secondary particles.

[0028] The first embodiment of an inorganic porous material is in powder form, and the average particle size (50% particle size, D) in the cumulative particle size distribution based on volume. 50 The particle size is preferably 1 μm to 1 mm. If the average particle size of the inorganic porous material is 1 μm or more, the pressure drop when the gas to be treated is passed through the adsorbent can be prevented from becoming too high, and if it is 1 mm or less, an inorganic porous material with higher strength can be obtained. Average particle size (D) of powdered inorganic porous material 50 The thickness is preferably 1 μm or more, more preferably 10 μm or more, preferably 1 mm or less, more preferably 500 μm or less, and even more preferably 100 μm or less.

[0029] Average particle diameter (D 50 This can be measured by the electrical detection band method (Coulter counter method) in accordance with JIS Z 8832 (2010).

[0030] When the inorganic porous material is in powder form, it is preferable that the inorganic porous material is spherical with a circularity of 0.8 or greater. By using a spherical inorganic porous material with a circularity of 0.8 or greater, the packing efficiency of the adsorbent into the separation and recovery device is increased, the amount of acidic gas adsorbed can be improved, and the pressure loss of the adsorbent is also reduced, thus increasing the energy utilization efficiency. Furthermore, when the inorganic porous material is molded, the size of the voids is easier to control compared to irregularly shaped particles, and the amount of oil absorbed by amine compounds can be increased. In addition, when supported on a filter, sandwiched between nonwoven fabrics, or folded after being sandwiched, there is less damage to the fibers and particle leakage is less likely to occur. The circularity of the powdered inorganic porous material is preferably 0.8 or higher, and more preferably 0.85 or higher. There is no particular upper limit to the circularity, but it is most preferably 1.

[0031] The circularity can be calculated by obtaining an image from a particle image analyzer (for example, Sysmex Corporation's "FPIA-3000S" (product name)), determining the particle area and perimeter using the image analysis software included with the device, and then applying these values ​​to the following formula. Circularity = Perimeter of circles with equal projected area / Perimeter of a particle The circumference of a circle with the same projected area: When a particle is observed from directly above, the area of ​​the shadow cast by the particle on the plane below is calculated, and a circle with an area equal to this is calculated, and the length of the outline of that circle is determined. Particle circumference: The length of the outline of the particle's shadow projected onto the plane below when the particle is observed from directly above.

[0032] A second embodiment of the inorganic porous material is a molded body, preferably with a maximum diameter of 1 mm to 50 mm. Here, the "maximum diameter" of the molded body refers to the diameter of the smallest circumscribed circle that circumscribes the molded body. If the maximum diameter of the molded inorganic porous body is 1 mm or more, the pressure loss when the gas to be treated is passed through can be reduced, and if it is 50 mm or less, the mechanical strength of the molded body can be kept sufficiently high. The maximum diameter of the molded body is preferably 1 mm or more, more preferably 1.5 mm or more, even more preferably 2 mm or more, and also preferably 50 mm or less, more preferably 30 mm or less, and even more preferably 10 mm or less.

[0033] Examples of molded body shapes include common fixed / irregular shapes such as spheres, ellipses, cylinders, polygonal prisms, rods, cones, polygonal pyramidal shapes, and combinations thereof, as well as honeycomb shapes, and special shapes such as Raschig rings, Berl saddles, and pole rings. When variable filling efficiency is desired, it is preferable to use molded bodies of general shapes, while when it is desirable to improve the mixing efficiency of the gas to be treated, it is preferable to use molded bodies of special shapes. Molded bodies of special shapes disrupt the gas flow, intensifying mixing and increasing the gas diffusion rate inside the molded body, and allowing for uniform distribution of adsorbent material within the molded body containment space in the separation and recovery device, even if the space is large. When molding molded bodies into special shapes, the shapes are not limited to those described above, as long as they increase the porosity.

[0034] The preferred range for the mechanical strength of the molded body is a compressive strength of 3 kgf or more, and more preferably 10 kgf or more. A compressive strength of 3 kgf or more prevents the molded body from breaking and turning into powder during handling.

[0035] When an inorganic porous material is used as the molded body, one method of manufacturing the molded body is to granulate the powdered inorganic porous material. Granulation methods include dry molding such as tableting and briquetting, as well as wet granulation such as spray granulation, tumbling granulation, agitation granulation, and extrusion molding. It is also possible to produce the molded body by injection molding.

[0036] In tableting or briquetting, a small amount of lubricant or excipient is added to inorganic porous powder, and the mixture is molded in a tableting machine or briquetting machine to obtain molded bodies with a diameter of 1 mm to 20 mm and a thickness of several 1 mm to 20 mm.

[0037] Wet granulation is a method of granulating inorganic porous powder by adding a binder and a solvent such as water or alcohol. While organic and inorganic binders are available, it is preferable to select a binder that can produce a high-mechanism molded body even with a small amount added. Organic and inorganic binders may be used in combination. Examples of organic binders include polyvinyl alcohol, butyral resin, and acrylic resin. Examples of inorganic binders include flaky silica, silica sol, alumina sol, and montmorillonite clay minerals. When using an inorganic binder for molding, the solvent (water or alcohol) may be removed by drying, followed by firing at a high temperature. This is because firing at a high temperature strengthens the chemical bond between the inorganic porous powder and the inorganic binder, resulting in a molded body with high mechanical strength.

[0038] Spray granulation is a method in which an inorganic porous powder and a binder are mixed with a solvent to form a slurry, and the solvent is dried while spraying the slurry from a spray nozzle. Relatively small spherical molded bodies with a diameter of about 1 mm to 10 mm can be obtained. Rolling granulation is a method in which inorganic porous powder and a binder are placed in a pan of a pan-type granulator, and a solvent is added while the pan is rotated at a speed of several tens of revolutions per minute to granulate. Due to the surface tension of the solvent, the inorganic porous powder and binder aggregate and form into spheres, and then the solvent is dried to obtain spherical molded bodies with a diameter of 1 mm to 50 mm. If the amount of solvent added is too little, only small molded bodies will be obtained, on the other hand, if the amount of solvent added is too much, the whole thing will become a clay-like mass and it may not be possible to form it into a sphere. Stir granulation is a method of granulation in which inorganic porous powder and a binder are placed in the container of a stir granulator, and a solvent is added while the stirring blades are rotated at a speed of several thousand revolutions per minute. Due to the surface tension of the solvent, the inorganic porous powder and binder agglomerate and form into spheres, and then the solvent is dried to obtain relatively small spherical molded bodies with a diameter of 1 mm to 10 mm. If the amount of solvent added is too little, only small molded bodies will be obtained, on the other hand, if the amount of solvent added is too much, the whole thing may become a clay-like mass and may not be able to be molded into a sphere. Extrusion molding involves mixing inorganic porous powder and a binder with a small amount of solvent to create a clay-like substance, which is then extruded through an extrusion machine to form pellets or cylinders, for example, with a diameter of 1 mm to 10 mm and a length of 1 mm to 30 mm. The solvent is then dried to form a molded body. Spherical molded bodies can also be obtained by sizing the extruded material in a sizing machine and then drying the solvent.

[0039] Injection molding is a molding method in which a mixture of inorganic porous powder, a binder, and a solvent is injected into a cavity with the same shape as the target object, and then dried to obtain a molded product.

[0040] When an inorganic porous material is used as the molded body, another method for producing the molded body, which is specific to silica, involves mixing sodium silicate with a mineral acid such as sulfuric acid to generate primary silica particles with a size of several nanometers to several tens of nanometers, and then generating a gel in which these primary silica particles aggregate three-dimensionally. This gel is then washed with water, dried, and pulverized to form particles with a maximum diameter of 1 mm to 50 mm, or the gel is formed into spherical gels with a maximum diameter of 1 mm to 50 mm by methods such as spraying or forming droplets in an organic solvent, and then washed with water and dried to obtain a silica molded body.

[0041] The inorganic porous material used in this invention may be obtained by synthesis or may be a commercially available material. Examples of commercially available products include "Sunsphere L-123" (product name) manufactured by AGC SI-TEC Co., Ltd. For synthesis, for example, it can be synthesized according to the method described in Japanese Patent Publication No. 6241252.

[0042] Inorganic porous materials may be used individually or in combination of two or more types. When using two or more types in combination, examples include combining two or more powdered inorganic porous materials with different particle sizes, combining two or more molded inorganic porous materials with different shapes (molded materials of a general shape), or combining powdered inorganic porous materials with two or more molded inorganic porous materials (molded materials of a general shape).

[0043] Amine compounds have an amino group in their structure and react with acidic gases, selectively absorbing the acidic gases in the gas being treated. When an acidic gas comes into contact with the adsorbent, the amino group of the amine compound reacts with the acidic gas, and one hydrogen atom of the amino group is replaced by a carboxyl group. As a result, the acidic gas in the gas being treated is adsorbed onto the adsorbent.

[0044] Examples of amine compounds containing an amino group include 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, N-methyl-3-aminopropyltriethoxysilane, N-methyl-3-aminopropyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropyltriethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, (3-trimethoxysilylpropyl)diethylenetriamine, ammonia, alkanolamines (methylamine, ethylamine, n-propylamine, isopropylamine, n-butylamine, tert-butylamine, etc.), monoethanolamine, diethanolamine, N-methyldiethanolamine, isopropylaminoethanol, 2-amino-2-methyl-1-propanol, ethylenediamine, and diethylene Examples include triamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, hexaethyleneheptamine, polyethyleneimine (PEI), 1,11-bis(isopropylamino)-3,6,9-triazoundecane, tetraisopropylated N,N,N',N'-tetrakis(3-aminopropyl)-1,4-butanediamine, 1,14-bis(isopropylamino)-3,6,9,12-tetraazatetradecane, 1,17-bis(isopropylamino)-3,6,9,12,15-pentazaheptadecane, N,N'-bis(3-(isopropylamino)propyl)-1,4-butanediamine, piperazine, N-(2-aminoethyl)piperazine, melamine, imidazole, guanidine, and amino acids (alanine, glycine, arginine, glutamine, lysine, etc.). These amine compounds may be used as single compounds or as mixtures. In particular, from the viewpoint of raw material availability, boiling point, and viscosity, it is preferable to use amine compounds containing silicon in the molecule or polyamine compounds containing three or more amino groups in the molecule. Specifically, 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropyltriethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, (3-trimethoxysilylpropyl)diethylenetriamine, diethylenetriamine, polyethyleneimine, and arginine are preferred.

[0045] Amine compounds are supported on the surface and within the pores of an inorganic porous material. "Supported" means that the amine compound is attached to or bound to the surface and inner surface of the pores of the inorganic porous material. It is preferable that the amine compound is supported by adhering to or binding to at least one of the surface and the inner surface of the pores of the inorganic porous material, or by filling the pores of the inorganic porous material and adhering to the inner surface of the pores.

[0046] If the amine compound is an amine compound containing silicon in its molecule, the silicon-containing functional group chemically reacts with the surface of the inorganic porous material, and the amine compound is supported on the surface or inner surface of the pores of the inorganic porous material. If the amine compound is a polyamine compound containing three or more amino groups in its molecule, the amine compound is physically packed into the pores of the inorganic porous material.

[0047] The amount of amine compound supported in an inorganic porous material can be determined by the nitrogen atom content in the adsorbent. It is preferable that the amine compound is supported such that the nitrogen atom content in the adsorbent is between 1N% and 40N% by mass. A nitrogen atom content of 1N% or more by mass improves the adsorption of acidic gases, while a content of 40N% or less reduces the likelihood of the adsorbent becoming sticky due to excess amine compound exceeding the pore volume of the inorganic porous material, making it easier to handle. The nitrogen atom content in the adsorbent is preferably 1N% or more by mass, more preferably 2N% or more, even more preferably 3N% or more, and preferably 40N% or less, more preferably 35N% or less, and even more preferably 30N% or less.

[0048] The nitrogen atom content in the adsorbent can be calculated by the mass ratio of nitrogen atoms to the total atomic mass of the inorganic porous material and the supported amine compound.

[0049] The adsorbent of the present invention may contain components other than inorganic porous materials and amine compounds, as long as they do not impair the effects of the present invention. Other components include, for example, binder compounds used during granulation. The binder compound can be any material capable of binding inorganic porous materials, such as polymers like polyvinyl alcohol, butyral resin, and acrylic resin, as well as sol gels, cements, flake silica, silica sol, alumina sol, montmorillonite clay minerals, silicates, and phosphates. These binder compounds are either commercially available or can be easily manufactured by known methods.

[0050] The shape of the adsorbent according to the present invention is not particularly limited and may be a shape similar to that of an inorganic porous body or a molded body thereof, for example, it may be in the form of a powder, granules, plate, block, thin film, or any other shape. Considering the filling efficiency into the separation and recovery device, gas resistance, strength, etc., the adsorbent is preferably in the form of a powder, granules, or cylinder.

[0051] The first aspect of the adsorbent is the average particle size (50% particle size, D) in the cumulative particle size distribution based on volume. 50 The adsorbent is in powder form with particles ranging from 1 μm to 1 mm in size. If the average particle size of the adsorbent is 1 μm or larger, the pressure drop when passing the gas to be treated through it can be prevented from becoming too high, and if it is 1 mm or smaller, a stronger adsorbent can be obtained. The average particle size of the adsorbent is preferably 1 μm or more, more preferably 10 μm or more, preferably 1 mm or less, more preferably 500 μm or less, and even more preferably 100 μm or less.

[0052] Average particle diameter (D 50 As mentioned above, this can be measured by the electrical detection band method (Coulter counter method) in accordance with JIS Z 8832 (2010).

[0053] If the adsorbent is in powder form, its circularity will be similar to that of an inorganic porous material. Preferably, the adsorbent is spherical with a circularity of 0.8 or higher. A circularity of 0.8 or higher improves the filling efficiency into the separation and recovery device, increases the amount of acidic gas adsorbed, and reduces pressure loss, thus improving energy utilization efficiency. The circularity of the adsorbent is preferably 0.8 or higher, and more preferably 0.85 or higher. There is no particular upper limit to the circularity, but it is most preferably 1.

[0054] Furthermore, as mentioned above, the circularity can be calculated using the image analysis software attached to the particle image analyzer, based on the image obtained from the analyzer.

[0055] A second form of the adsorbent is a molded body, preferably with a maximum diameter (the diameter of the smallest circumscribed circle circumscribed around the molded body) of 1 mm to 50 mm. If the maximum diameter of the molded body is 1 mm or more, the pressure loss when the gas to be treated is passed through can be reduced, and if it is 50 mm or less, the mechanical strength of the molded body can be kept sufficiently high. The maximum diameter of the molded body is preferably 1 mm or more, more preferably 1.5 mm or more, even more preferably 2 mm or more, and also preferably 50 mm or less, more preferably 30 mm or less, and even more preferably 10 mm or less.

[0056] When the adsorbent is a molded body, the shape of the molded body is not particularly limited, and should be chosen considering factors such as the efficiency of filling the separation and recovery device and the mixing efficiency of the gas to be treated. Examples of molded body shapes include general fixed / irregular shapes such as spherical, elliptical, cylindrical, polygonal prism, rod, conical, polygonal pyramidal, and combinations thereof, as well as honeycomb shapes, and special shapes such as Raschig rings, Berl saddles, and pole rings.

[0057] Furthermore, if the adsorbent is a molded body, its mechanical strength will also be in accordance with the aspect ratio of the molded inorganic porous body. The mechanical strength of the molded body (adsorbent) is preferably 3 kgf or more in compressive strength, and more preferably 10 kgf or more. A compressive strength of 3 kgf or more prevents it from breaking and turning into powder during handling.

[0058] (Manufacturing of adsorbents) The adsorbent of the present invention can be manufactured, for example, by the following method (1) or (2). (1) A method for fixing an amine compound to at least one of the surface and the inner surface of the pores of an inorganic porous material. (2) A method for filling amine compounds into the pores of an inorganic porous material. The adsorbent of the present invention may be obtained by either method (1) or method (2), or by a combination of both methods.

[0059] In method (1), an amine compound containing silicon in its molecule is used as the amine compound. The adsorbent of the present invention can be obtained by contacting a silicon-containing amine compound with an inorganic porous material and allowing it to react over time or by heating. The amine compound may be dissolved in a solvent, or multiple amine compounds may be mixed together.

[0060] Suitable solvents for amine solutions include, for example, water, alcohols, ethers, esters, amines, and amides. Among these, alcohols are preferred from the viewpoint of availability and ease of removal after contact with inorganic porous materials. More preferably, the amine compound is brought into contact directly without a solvent, as this eliminates the need for a removal step.

[0061] The concentration of the amine compound in the amine solution is preferably 20 to 100% by mass, from the viewpoint of increasing the contact efficiency and loading capacity with the inorganic porous material. A concentration of 25% by mass or higher is more preferable, and 50% by mass or higher is even more preferable.

[0062] The amine solution may contain other components, to the extent that it does not impair the effects of the present invention. Examples of other components include platinum, ruthenium, and rhodium.

[0063] Contact between an amine solution and an inorganic porous material can be carried out by conventionally known methods, such as immersing the inorganic porous material in an amine solution, dropping or spraying the amine solution onto the inorganic porous material, or precipitating the inorganic porous material in an amine solution. Among these, dropping or spraying the amine solution onto the inorganic porous material is preferred from the viewpoint of ease of operation.

[0064] It is preferable to bring the amine solution into contact with the inorganic porous material and then react it at 20-150°C for 1-48 hours. When the reaction temperature is 20°C or higher, the reaction between the silicon-containing functional group of the amine compound and the hydroxyl group on the surface of the inorganic porous material proceeds rapidly. When the temperature is 150°C or lower, the oxidation of the amine compound is suppressed, and the scattering of the amine compound before the reaction can be prevented. The reaction temperature is preferably 20°C or higher, more preferably 40°C or higher, preferably 150°C or lower, and more preferably 100°C or lower. If the reaction time is 1 hour or more, the silicon-containing functional group of the amine compound and the hydroxyl group on the surface of the inorganic porous material react sufficiently, and if it is 48 hours or less, the manufacturing process can be shortened. The reaction time is preferably 1 hour or more, more preferably 2 hours or more, preferably 48 hours or less, and more preferably 24 hours or less.

[0065] After the reaction, a drying process can be carried out under reduced pressure if necessary. Drying should be done at 20-150°C for 1-24 hours.

[0066] In method (2), a polyamine compound containing three or more amino groups in its molecule is used as the amine compound. The adsorbent of the present invention is obtained by contacting an amine solution, obtained by dissolving a polyamine compound in a solvent, with an inorganic porous body, heating it as necessary, and holding the solution in that state.

[0067] Suitable solvents for amine solutions include, for example, water, alcohols, ethers, esters, amines, and amides. Among these, alcohols are preferred from the viewpoint of availability and ease of removal after contact with inorganic porous materials. More preferably, the amine compound is brought into contact directly without a solvent, as this eliminates the need for a removal step.

[0068] The concentration of the amine compound in the amine solution is preferably 20 to 100% by mass, from the viewpoint of increasing the contact efficiency and loading capacity with the inorganic porous material. A concentration of 25% by mass or more is more preferable, and 50% by mass or more is even more preferable.

[0069] The amine solution may contain other components as long as they do not impair the effects of the present invention. Examples of other components include amine compounds containing one to two amino groups in their molecule.

[0070] Contact between an amine solution and an inorganic porous material can be carried out by conventionally known methods, such as immersing the inorganic porous material in an amine solution, dropping or spraying the amine solution onto the inorganic porous material, or precipitating the inorganic porous material in an amine solution. Among these, dropping or spraying the amine solution onto the inorganic porous material is preferred from the viewpoint of ease of operation.

[0071] After bringing the amine solution into contact with the inorganic porous material, it can be left at 20-150°C for 1-48 hours, and stirring may be performed if necessary. When the reaction temperature is 20°C or higher, the viscosity of the amine compound decreases, making it easier for the amine compound to fill the pores of the inorganic porous material. When the reaction temperature is 150°C or lower, oxidation of the amine compound is suppressed, preventing the amine compound from scattering before the reaction. The reaction temperature is preferably 20°C or higher, more preferably 25°C or higher, preferably 150°C or lower, and more preferably 100°C or lower. If the reaction time is 1 hour or more, the amine compound will be sufficiently filled into the pores of the inorganic porous material, and if it is 48 hours or less, the manufacturing process can be shortened. The reaction time is preferably 1 hour or more, more preferably 2 hours or more, preferably 48 hours or less, and more preferably 24 hours or less.

[0072] After the reaction, a drying process can be carried out if necessary. Drying should be performed at 20-150°C for 1-24 hours. The drying process may also be carried out under reduced pressure.

[0073] (Adsorption and desorption methods using adsorbent materials) The adsorbent of the present invention can be used for the adsorption and removal of acidic gases from gases containing acidic gases.

[0074] The gas to be treated using the adsorbent of the present invention can be any gas containing an acidic gas. Examples of gases to be treated include gases containing carbon dioxide (CO2), carbon monoxide (CO), hydrocarbons (HC), sulfur oxides (sulfur dioxide, sulfur trioxide, etc.), nitrogen oxides (NOx), hydrogen chloride, water vapor, particulate matter (PM), etc. More specifically, examples include atmospheric gas, fuel exhaust gas from automobiles and factories, industrial gases such as helium and nitrogen gas, and gases emitted in enclosed spaces such as space stations due to human respiration or energy conversion by equipment.

[0075] The concentration of acidic gas in the gas to be treated is not particularly limited as long as the adsorbent can withstand the conditions, but is preferably 100% by volume or less, more preferably 50% by volume or less, and even more preferably 30% by volume or less. The lower limit is not particularly limited, but is preferably 0.01% by volume or more. When the acidic gas contains carbon dioxide, the concentration of carbon dioxide in the gas to be treated is preferably 30% by volume or less. The adsorbent of the present invention can exhibit sufficient adsorption capacity for gases to be treated that contain carbon dioxide at a concentration of 30% by volume or less. The gas to be treated may be at atmospheric pressure or under pressurization.

[0076] Methods for adsorption and desorption of acidic gases include the pressure swing method (PSA method), which uses a pressure difference for adsorption and desorption; the thermal swing method (TSA method), which uses a temperature difference for adsorption and desorption; and a method in which the gas to be treated, which contains acidic gas, is brought into contact with an adsorbent material for adsorption, and then an inert gas that does not contain acidic gas is brought into contact with the adsorbent material for desorption.

[0077] In the PSA method, the amount of acidic gas adsorbed increases as the total pressure of the atmosphere in which the adsorbent is present (for example, the total pressure inside the container containing the adsorbent) increases. Therefore, it is preferable to change the total pressure of the desorption process to be lower than the total pressure of the adsorption process. The total pressure may be adjusted by increasing or decreasing pressure, or by using both increasing and decreasing pressure in combination.

[0078] In the TSA method, for example, the temperature of the adsorbent in the desorption process is made higher than in the adsorption process. Methods for heating the adsorbent include directly contacting the heated gas to be treated with the adsorbent, heating the adsorbent by heat conduction from the heat transfer surface using heat transfer tubes, etc., and heating the adsorbent using an electric furnace, etc.

[0079] In a method of adsorption and desorption using an inert gas that does not contain acidic gas, the gas to be treated is brought into contact with an adsorbent to adsorb the acidic gas, and then the adsorbent with the adsorbent is brought into contact with an inert gas. As a result, the acidic gas adsorbed on the adsorbent is replaced by the inert gas, and the acidic gas can be recovered. Any inert gas can be used as long as the adsorbent is stable in that gas, but examples include water vapor, argon, and nitrogen.

[0080] The adsorbent material of the present invention can be used for repeated adsorption by performing a desorption process after the adsorption process. [Examples]

[0081] The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples. Unless otherwise specified, "parts" and "%" represent "parts by mass" and "% by mass," respectively. Examples 1-2 and 6-13 are examples, and Examples 3-5, 14 and 15 are comparative examples.

[0082] <Evaluation Method> The evaluations performed on the adsorbents in Examples 1 to 15 are shown below.

[0083] (Pore volume, peak diameter, and average pore diameter) The pore volume, peak diameter, and average pore diameter of the inorganic porous material were measured using the BET method and BJH method based on nitrogen adsorption with the specific surface area and pore distribution analyzer "BELSORP-miniII" (product name, manufactured by Microtrac-Bel Co., Ltd.).

[0084] (Oil absorption amount) The oil absorption capacity of the inorganic porous material was measured in accordance with JIS K 5101. The inorganic porous material sample was kneaded until it formed a single mass, and boiled linseed oil was added to the sample as it was kneaded. The volume of boiled linseed oil per 100g of the sample was then determined.

[0085] (Average particle diameter (D 50 )) Average particle size of adsorbent (D 50 The particle size distribution was measured using the electrical detection zone method with the precision particle size distribution analyzer "Multisizer3" (product name, manufactured by Beckman Coulter, Inc.).

[0086] (Circularity) The circularity of the adsorbent was measured by image analysis using the flow-type particle image analyzer "FPIA-3000S" (product name, manufactured by Sysmex Corporation), and judged based on a circularity of 0.8.

[0087] (Nitrogen atom content) The nitrogen atom content of the adsorbent was determined by dividing the mass of nitrogen atoms in the supported amine compound by the sum of the atomic masses of each atom in the inorganic porous material and the atomic masses of each atom in the amine compound supported on the inorganic porous material.

[0088] (Carbon dioxide adsorption capacity) Using the Microtrac-Bel "BELCAT II" (product name) as the measuring device, the change in carbon dioxide adsorption amount over time (carbon dioxide adsorption curve) was measured according to the following procedure, and the amount of carbon dioxide adsorbed by the adsorbent was calculated. 1. A sample tube (inner diameter: 10 mm) in the measuring device was filled with 0.1 g of an inorganic porous material supporting an amine compound, and the temperature inside the sample tube was set to 23°C. 2. Carbon dioxide diluted to a concentration of 10% by volume with helium was introduced into the sample tube at a flow rate of 30 ml / s through a mass flow controller. 3. The gas that passed through the sample tube was detected by a TCD mounted in the apparatus, and it was confirmed that the carbon dioxide concentration reached 10% by volume (i.e., saturated adsorption was achieved). The adsorption process was then terminated, and a carbon dioxide adsorption curve was obtained for the inorganic porous material supported with the amine compound. 4. Next, in step 1 above, steps 1-3 were performed without adding any sample to obtain a blank carbon dioxide adsorption curve. 5. The amount of carbon dioxide adsorbed by the adsorbent was determined by subtracting the carbon dioxide adsorption curve of the inorganic porous material supported with the amine compound from the blank carbon dioxide adsorption curve.

[0089] The inorganic porous materials and amine compounds used in Examples 1-15 are as follows: (Inorganic porous material) • Inorganic porous material A: Silica, specific surface area: 277 m² 3 / g, pore volume: 2.0 cm³ 3 / g, peak diameter of pore size: 50nm • Inorganic porous material B: Silica, specific surface area: 735 m² 3 / g, pore volume: 1.6cm³ 3 / g, peak diameter of pore size: 20nm • Inorganic porous material C: Silica, specific surface area: 296 m² 3 / g, pore volume: 2.2cm³ 3 / g, peak diameter of pore size: 42nm • Inorganic porous material D: Silica, specific surface area: 363 m² 3 / g, pore volume: 2.1cm³ 3 / g, peak diameter of pore size: 30nm • Inorganic porous material E: Silica, specific surface area: 660 m² 3 / g, pore volume: 3.1cm³ 3 / g, peak diameter of pore size: 24nm • Inorganic porous material F: Silica, specific surface area: 1000 m² 3 / g, pore volume: 1.0 cm³ 3 / g, peak diameter of pore size: 3.3nm • Inorganic porous material G: Silica, specific surface area: 700 m² 3 / g, pore volume: 1.1cm³ 3 / g, peak diameter of pore size: 6.0nm • Inorganic porous material H: Silica, specific surface area: 836 m² 3 / g, pore volume: 0.8cm³ 3 / g, peak diameter of pore size: 4.0nm • Inorganic porous material I: Silica molded body, specific surface area: 462 m²3 / g, pore volume: 1.4cm³ 3 / g, peak diameter of pore size: 24nm • Inorganic porous material J: Silica, specific surface area: 296 m² 3 / g, pore volume: 1.6cm³ 3 / g, peak diameter of pore size: 22nm • Inorganic porous material K: Silica, specific surface area: 235 m² 3 / g, pore volume: 2.6cm³ 3 / g, peak diameter of pore size: 45nm • Inorganic porous material L: Silica, specific surface area: 461 m² 3 / g, pore volume: 1.5cm³ 3 / g, peak diameter of pore size: 12nm (Amine compounds) • Amine compound a: 3-aminopropyltriethoxysilane (APS) • Amine compound b: Diethylenetriamine (triamine)

[0090] (Example 1) Inorganic porous material A (silica, specific surface area: 277 m²) 3 / g, pore volume: 2.0 cm³ 3 An adsorbent was prepared by supporting amine compound a (3-aminopropyltriethoxysilane) on a pore size (peak diameter: 50 nm) as follows. The required amount of inorganic porous material A was weighed into a flask, and the pore volume was calculated from its weight. Amine compound a, equivalent to 95-100% of the calculated pore volume, was weighed into a separate container. A small amount of amine compound a was collected using a glass pipette and added dropwise to inorganic porous material A in a flask. The flask was then covered and shaken to ensure sufficient contact between inorganic porous material A and amine compound a. This process was repeated several times until all of the weighed amine compound a was in contact with inorganic porous material A, and the flask was then held at room temperature for 1 hour. Next, the flask was placed in an inert oven at 80°C and dried under reduced pressure for 16 hours. After drying, the flask was returned to room temperature and atmospheric pressure to obtain the adsorbent.

[0091] (Examples 2-5) Adsorbent materials were prepared in the same manner as in Example 1, except that the inorganic porous material was changed to one of those listed in Table 1.

[0092] (Example 6) Inorganic porous material A (silica, specific surface area: 277 m²) 3 / g, pore volume: 2.0 cm³ 3 An adsorbent was prepared by packing amine compound b (diethylenetriamine) into a pore size (peak diameter: 50 nm) as follows. The required amount of inorganic porous material A was weighed into a flask, and the pore volume was calculated from its weight. Amine compound b, equivalent to 95-100% of the calculated pore volume, was weighed into a separate container. A small amount of amine compound b was collected using a glass pipette and added dropwise to inorganic porous material A in a flask. The flask was then covered and shaken to ensure sufficient contact between inorganic porous material A and amine compound b. This process was repeated several times until all of the weighed amine compound b was in contact with inorganic porous material A, and the flask was then kept at room temperature for 1 hour. Next, it was placed in an inert oven at 50°C and dried for 24 hours. After drying, it was returned to room temperature to obtain the adsorbent.

[0093] (Examples 7-10, 12-15) Adsorbent materials were prepared in the same manner as in Example 6, except that the inorganic porous material was changed to one of those listed in Table 2.

[0094] (Example 11) Inorganic porous material I (silica molded body, specific surface area: 462 m²) 3 / g, pore volume: 1.4cm³ 3 The sample ( / g, peak pore diameter: 24 nm) was first prepared as follows. 16.1 parts of spherical porous silica powder with a particle size of 3 μm (Sunsphere H32, manufactured by AGC SI-TEC), 15.9 parts of spherical porous silica powder with a particle size of 35 μm (Sunspera L-303, manufactured by AGC SI-TEC), 68.0 parts of flake silica slurry as an inorganic binder (Sunlovely, manufactured by AGC SI-TEC, solid content concentration = 5.0%), and 26.0 parts of ion-exchanged water were mixed and kneaded. The kneaded mixture was then extruded to form a cylindrical shape with a diameter of 5 mm and a length of 5 mm, and then dried at 110°C for 2 hours to obtain a molded body (inorganic porous body I). The mechanical strength of the obtained inorganic porous material I was 5 kgf. A digital hardness tester, model KHT-40N (manufactured by Fujiwara Seisakusho Co., Ltd.), was used to measure the mechanical strength. Furthermore, when the pore volume of inorganic porous material I was measured using a mercury porosimeter, it was found to be 2.0 cm³. 3 It was / g. Then, an adsorbent was prepared in the same manner as in Example 6, except that inorganic porous material I was used instead of inorganic porous material A.

[0095] Using the adsorbent obtained above, the average particle size (D 50 The circularity or size of the molded body, nitrogen atom content, and carbon dioxide adsorption amount were measured. The results are shown in Tables 1 and 2.

[0096] [Table 1]

[0097] [Table 2]

[0098] As shown in Table 1, while Examples 1-5 involved immobilizing amine compounds on the surface of inorganic porous materials, Examples 1 and 2 exhibited higher carbon dioxide adsorption capacity compared to Examples 3-5, demonstrating superior carbon dioxide adsorption capabilities. Example 1, in particular, showed remarkably high carbon dioxide adsorption. As shown in Table 2, while Examples 6-15 involved filling the pores of an inorganic porous material with an amine compound, Examples 6-13 showed higher carbon dioxide adsorption capacity compared to Examples 14-15, indicating superior carbon dioxide adsorption capabilities.

[0099] Although the present invention has been described in detail and with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the invention. This application is based on Japanese Patent Application No. 2020-190362, filed on 16 November 2020, the contents of which are incorporated herein by reference.

Claims

1. It contains an inorganic porous material and an amine compound. The inorganic porous material is an adsorbent for carbon dioxide, having an oil absorption capacity of 230 ml / 100 g or more, and a peak pore diameter determined by the nitrogen adsorption method being 20 nm to 100 nm, and being in the form of a powder with an average particle diameter of 1 μm to 1 mm or a molded body with a maximum diameter of 1 mm to 50 mm.

2. It contains an inorganic porous material and an amine compound. The inorganic porous material has a pore volume of 1.2 cm³. ３ / g or more 3.5cm ３ An adsorbent for adsorbing carbon dioxide, having a concentration of less than or equal to / g, and a peak pore diameter determined by the nitrogen adsorption method being between 20 nm and 100 nm, and being in the form of a powder with an average particle diameter of 1 μm to 1 mm or a molded body with a maximum diameter of 1 mm to 50 mm.

3. The adsorbent according to claim 1 or 2, wherein the average pore size determined by the nitrogen adsorption method of the inorganic porous body is 15 nm or more and 100 nm or less.

4. The adsorbent according to any one of claims 1 to 3, wherein the nitrogen atom content in the adsorbent is 1 N% or more and 40 N% or less by mass ratio.

5. The adsorbent according to any one of claims 1 to 4, wherein the inorganic porous body comprises at least one selected from the group consisting of silica, zeolite, alumina, silica-alumina, activated carbon, titania, silica gel, aluminum silicate, magnesium silicate, and clay minerals.

6. The adsorbent according to any one of claims 1 to 5, wherein the amine compound is an amine compound containing silicon in its molecule or a polyamine compound containing three or more amino groups in its molecule.

7. The adsorbent according to any one of claims 1 to 6, wherein the amine compound is fixed to at least one of the surface and the inner surface of the pores of the inorganic porous body.

8. The adsorbent according to any one of claims 1 to 6, wherein the amine compound is filled in the pores of the inorganic porous body.

9. The adsorbent according to any one of claims 1 to 8, wherein the inorganic porous body is in powder form, and the inorganic porous body is spherical with a circularity of 0.8 or more.

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