Honeycomb structure and method for producing same

Abstract

Provided is a honeycomb structure which has CO2 adsorption performance, is easy to mold, generates less CO2 during production, is unlikely to crack during drying, and has improved water resistance. The honeycomb structure has a plurality of cell channels that pass through the inside of the honeycomb structure and are defined by partition walls containing a solid organic compound having an amino group, an organic binder, and an inorganic binder.

Description

TECHNICAL FIELD

[0001] The present application relates to a honeycomb structure and a method for manufacturing the same. More specifically, the present application relates to a honeycomb structure having a CO2 adsorption property and a method for manufacturing the same. BACKGROUND

[0002] In order to realize a decarbonized society, the demand for a technology for recovering and utilizing carbon dioxide (CO2) from the atmosphere or exhaust gas is increasing. As a representative CO2 recovery technology in the past, a technology for adsorbing CO2 in the atmosphere (DAC: Direct Air Capture) is being developed. DAC has several types such as a liquid absorption method, a membrane separation method, and a solid adsorption method. Among them, in the solid adsorption method, a CO2 adsorption (absorption) material is generally supported on a substrate. As a substrate used in the solid adsorption method, a honeycomb structure that has many achievements in the purification of automobile exhaust and the like is expected.

[0003] A conventional honeycomb structure is generally produced by kneading a molding raw material containing a ceramic raw material, water, a binder, and the like to obtain a green material, extrusion molding the green material to produce a honeycomb molded body, and then applying heat treatment such as firing to the honeycomb molded body (Patent Document 1). However, heat treatment such as firing requires a large amount of energy, and in most cases, combustion of a hydrocarbon fuel is involved, so CO2 is generated. In addition, if an organic binder is used as the binder, it is burned at the time of firing, further generating CO2.

[0004] A honeycomb ceramic substrate for CO2 recovery is described in Patent Document 2. The honeycomb ceramic substrate for CO2 recovery has a honeycomb ceramic substrate having porous partition walls, a plurality of inorganic support particles present in at least one pore within the porous partition walls, and an organic carbon dioxide adsorbent supported by at least one of the inorganic support particles. The honeycomb ceramic substrate for CO2 recovery is manufactured by heat treatment at a high temperature. Specifically, it is manufactured by bringing a honeycomb ceramic substrate obtained by a molding step and a firing step into contact with a support precursor slurry, then performing pre-firing at a temperature of about 100°C to about 600°C for about 1 hour to about 10 hours, and further bringing it into contact with an organic CO2 adsorbent, and then performing drying at about 50°C to about 100°C.

[0005] Under such background art, a technique of manufacturing a honeycomb structure without performing a firing process is also known. Patent Literature 3 describes a honeycomb substrate having a plurality of partition walls extending in an axial direction from an inlet end portion to an outlet end portion, thereby forming a plurality of flow channels, and the honeycomb substrate is obtained by dispersing an amine polymer having a functional structural unit group that absorbs CO2 in inorganic powder components of a mixture containing inorganic powder components and an organic binder in the partition walls of the honeycomb substrate. The honeycomb substrate is formed by a method including the steps of: dry-mixing inorganic oxide powder components and an organic binder into a mixture; adding a solution of an amine polymer and a solvent to the mixture to form a precursor; kneading the precursor; extrusion-molding the kneaded precursor to form a connected-type monolithic structure having a plurality of partition walls extending in an axial direction from an inlet end portion to an outlet end portion, thereby forming a plurality of flow channels; and performing drying to remove the solvent from the connected-type monolithic structure to form an absorbent structure for capturing CO2.

[0006] Prior Art Documents

[0007] Patent Literature

[0008] Patent Literature 1: Japanese Patent Application Laid-Open No. 2020-019690

[0009] Patent Literature 2: Japanese Patent Application Laid-Open No. 2018-538137

[0010] Patent Literature 3: Japanese Patent Application Laid-Open No. 2015-508018 SUMMARY

[0011] The honeycomb substrate described in Patent Literature 3 uses an amine polymer having a functional structural unit group that absorbs CO2, and thus, CO2 capture is possible. In addition, the honeycomb substrate is manufactured without a firing process at a high temperature, and thus, CO2 generated at the time of manufacturing can be reduced. However, the honeycomb substrate described in Patent Literature 3 uses an amine polymer, which is easily dissolved in water. In addition, the organic binder remaining due to the non-firing process is also water-soluble. Therefore, the honeycomb substrate described in Patent Literature 3 has room for improvement in terms of water resistance. In addition, there is also room for improvement from the viewpoint of suppressing cracks at the time of drying.

[0012] In view of the above, in one embodiment, an object of the present application is to provide a honeycomb structure having an adsorption property of CO2, being easily molded, generating less CO2 at the time of manufacturing, being less likely to generate cracks at the time of drying, and further having improved water resistance. In another embodiment, an object of the present application is to provide a method of manufacturing such a honeycomb structure.

[0013] The present inventors have intensively studied in order to solve the above-described problems, and as a result, have found that it is advantageous to use a prescribed CO2 adsorbing material, an organic binder, and an inorganic binder in combination as a material of a honeycomb structure. The present invention was completed based on the above-described insight, and will be illustrated below.

[0014] [Solution 1]

[0015] A honeycomb structure, wherein

[0016] has a plurality of cell passages passing through the inside of the honeycomb structure, formed by cell walls,

[0017] The cell walls contain a solid organic compound having an amino group, an organic binder, and an inorganic binder.

[0018] [Solution 2]

[0019] The honeycomb structure according to Solution 1, wherein

[0020] The solid organic compound having an amino group is water-insoluble.

[0021] [Solution 3]

[0022] The honeycomb structure according to Solution 1 or 2, wherein

[0023] The content ratio of the solid organic compound having an amino group in the cell walls is 40 to 94 mass%, the content ratio of the inorganic binder in the cell walls is 3 to 50 mass%, and the content ratio of the organic binder in the cell walls is 3 to 20 mass%.

[0024] [Solution 4]

[0025] The honeycomb structure according to Solution 1 or 2, wherein

[0026] The content ratio of the solid organic compound having an amino group in the cell walls is 40 to 90 mass%, the content ratio of the inorganic binder in the cell walls is 5 to 35 mass%, and the content ratio of the organic binder in the cell walls is 5 to 10 mass%.

[0027] [Solution 5]

[0028] The honeycomb structure according to any one of Solutions 1 to 4, wherein

[0029] The solid organic compound having an amino group is a weakly basic anion exchange resin having an amino group.

[0030] [Solution 6]

[0031] The honeycomb structure according to any one of Solutions 1 to 5, wherein

[0032] The solid organic compound having an amino group contains one or more kinds selected from the group consisting of a styrene-based divinylbenzene polymer having an amino group and an acrylic-based divinylbenzene polymer having an amino group.

[0033] [Scheme 7]

[0034] The honeycomb structure according to any one of Schemes 1 to 6, wherein

[0035] The solid organic compound having an amino group contains a primary amine as a functional group.

[0036] [Scheme 8]

[0037] The honeycomb structure according to any one of Schemes 1 to 7, wherein

[0038] The solid organic compound having an amino group contains an aromatic ring.

[0039] [Scheme 9]

[0040] The honeycomb structure according to any one of Schemes 1 to 8, wherein

[0041] The inorganic binder contains one or two or more kinds selected from the group consisting of fibrous and particulate inorganic binders.

[0042] [Scheme 10]

[0043] The honeycomb structure according to any one of Schemes 1 to 9, wherein

[0044] The inorganic binder contains one or two or more kinds selected from the group consisting of clay, diatomite, a layered clay mineral, montmorillonite, hydrotalcite, acid clay, acid clay, hectorite, halloysite, attapulgite, silica, alumina, talc powder, chlorite, vermiculite, mica, illite, pyrophyllite, sericite, kaolin, sepiolite, boehmite, palygorskite, and bentonite.

[0045] [Scheme 11]

[0046] The honeycomb structure according to Scheme 10, wherein

[0047] The inorganic binder contains one or two or more kinds selected from the group consisting of sepiolite, boehmite, bentonite, silica, kaolin, and talc powder.

[0048] [Scheme 12]

[0049] The honeycomb structure according to Scheme 11, wherein

[0050] The inorganic binder contains sepiolite.

[0051] [Scheme 13]

[0052] A method for manufacturing a honeycomb structure, comprising the steps of:

[0053] kneading a molding raw material containing a solvent, a solid organic compound having an amino group, an organic binder, and an inorganic binder to produce a blank; and

[0054] molding the blank into a honeycomb structure having a plurality of cell passages which pass through the inside of the honeycomb structure and are formed by cell walls.

[0055] [Solution 14]

[0056] The method for manufacturing a honeycomb structure according to Solution 13, wherein

[0057] The solid organic compound having an amino group is non-water-soluble.

[0058] [Solution 15]

[0059] The method for manufacturing a honeycomb structure according to Solution 13 or 14, wherein

[0060] The content rate of the solid organic compound having an amino group other than the solvent in the molding raw material is 40 to 94 mass%, the content rate of the inorganic binder other than the solvent in the molding raw material is 3 to 50 mass%, and the content rate of the organic binder other than the solvent in the molding raw material is 3 to 20 mass%.

[0061] [Solution 16]

[0062] The method for manufacturing a honeycomb structure according to Solution 13 or 14, wherein

[0063] The content rate of the solid organic compound having an amino group other than the solvent in the molding raw material is 40 to 90 mass%, the content rate of the inorganic binder other than the solvent in the molding raw material is 5 to 35 mass%, and the content rate of the organic binder other than the solvent in the molding raw material is 5 to 10 mass%.

[0064] [Solution 17]

[0065] The method for manufacturing a honeycomb structure according to any one of Solutions 13 to 16, wherein

[0066] The solid organic compound having an amino group is a weakly basic anion exchange resin having an amino group.

[0067] [Solution 18]

[0068] The method for manufacturing a honeycomb structure according to any one of Solutions 13 to 17, wherein

[0069] The amino-containing solid organic compound contains one or more selected from amino-containing styrene-based divinylbenzene polymers and amino-containing acrylic-based divinylbenzene polymers.

[0070] [Option 19]

[0071] The method for manufacturing a honeycomb structure according to any one of claims 13 to 18, wherein...

[0072] Solid organic compounds with amino groups contain primary amines as functional groups.

[0073] [Option 20]

[0074] The method for manufacturing a honeycomb structure according to any one of claims 13 to 19, wherein...

[0075] Solid organic compounds containing amino groups have aromatic rings.

[0076] [Option 21]

[0077] The method for manufacturing a honeycomb structure according to any one of claims 13 to 20, wherein...

[0078] Inorganic adhesives contain one or more inorganic adhesives selected from fibrous and granular forms.

[0079] [Option 22]

[0080] The method for manufacturing a honeycomb structure according to any one of claims 13 to 21, wherein,

[0081] The inorganic binder contains one or more inorganic binders selected from clay, diatomaceous earth, layered clay minerals, montmorillonite, hydrotalcite, activated clay, acid clay, lithium montmorillonite, halloysite, palygorskite, silica, alumina, talc, chlorite, vermiculite, mica, illite, pyrophyllite, sericite, kaolin, sepiolite, boehmite, palygorskite, bentonite, colloidal silica, and alumina sol.

[0082] [Option 23]

[0083] According to the manufacturing method of the honeycomb structure described in Scheme 22, wherein,

[0084] Inorganic binders contain one or more of the following: sepiolite, boehmite, bentonite, colloidal silica, alumina sol, kaolin, and talc.

[0085] [Option 24]

[0086] According to the method for manufacturing the honeycomb structure described in Scheme 23, wherein...

[0087] The inorganic binder contains sepiolite.

[0088] Invention Effects

[0089] One embodiment of the present invention relates to a honeycomb structure that possesses CO2 adsorption properties, is easy to mold, generates less CO2 during manufacturing, is less prone to cracking during drying, and thus exhibits improved water resistance. Furthermore, this honeycomb structure can be manufactured without high-temperature heat treatment, thereby reducing CO2 generation during manufacturing. Regarding this honeycomb structure, it is considered to have high practicality as a product for adsorbing atmospheric CO2 and can make a significant contribution to the realization of a decarbonized society. Attached Figure Description

[0090] Figure 1 This is a schematic perspective view of a honeycomb structure according to one embodiment of the present invention.

[0091] Figure 2 This is a schematic diagram of a cross-section of a honeycomb structure according to one embodiment of the present invention, parallel to the height direction (the direction of compartment extension).

[0092] Figure 3 The attached figure is a schematic illustration of a method for measuring the hardness of a blank using a hardness tester.

[0093] Figure 4 It is an enlarged view showing the shape and size of the front end of the hardness tester.

[0094] Figure 5 It is a chart showing the spring properties of the spring material used in a hardness tester. Detailed Implementation

[0095] Next, embodiments of the present invention will be described in detail with reference to the accompanying drawings. The present invention is not limited to the following embodiments, and it should be understood that appropriate modifications and alterations can be made based on the ordinary knowledge of those skilled in the art without departing from the spirit of the invention.

[0096] (1. Honeycomb structure)

[0097] Figure 1 The figure shows a schematic perspective view of a honeycomb structure according to one embodiment of the present invention. Figure 2 The middle shows Figure 1 A schematic diagram of a cross-section of the honeycomb structure parallel to the height direction (the direction in which the compartments extend).

[0098] The honeycomb structure 100 of this embodiment includes an outer peripheral sidewall 102 and a partition wall 112. The partition wall 112 is disposed on the inner peripheral side of the outer peripheral sidewall 102 and divides it into multiple compartments 108. The multiple compartments 108 extend from a first end face 104 to a second end face 106, forming a fluid flow path (compartment channel). The multiple compartments 108 are arranged parallel to each other. The honeycomb structure 100 of this embodiment is a flow-through type in which both ends of each compartment 108 are open at the first end face 104 and the second end face 106. When CO2-containing gas such as air flows in from the first end face 104 where the inlet of the multiple compartments 108 is located, CO2 is adsorbed during the passage through the multiple compartments 108, and the gas with a reduced CO2 concentration flows out from the second end face 106 where the outlet of the multiple compartments 108 is located.

[0099] The end face shape of a honeycomb structure is not particularly limited; for example, it can be a circle, ellipse, racetrack shape, or oblong shape with curves, a polygonal shape such as a triangle or quadrilateral, or other irregular shapes. The overall shape of a honeycomb structure is typically a column. (Regarding...) Figure 1 The honeycomb structure 100 shown has a round end face and is cylindrical in shape.

[0100] When the honeycomb structure is a column, its height (the length from the first end face to the second end face) is not particularly limited and can be appropriately set according to the application or required performance. There is also no particular limitation on the relationship between the height of the honeycomb structure and the maximum diameter of each end face (the maximum length of the diameter passing through the centroid of each end face of the honeycomb structure). Therefore, the height of the honeycomb structure can be longer than the maximum diameter of each end face, or it can be shorter than the maximum diameter of each end face.

[0101] There is no particular limitation on the length of the cell extension direction (height direction) of the honeycomb structure. However, a longer length can increase the CO2 adsorption capacity, but if it is too long, the pressure loss will be greater. Therefore, the length is preferably 20 to 350 mm, more preferably 20 to 300 mm, and even more preferably 20 to 250 mm.

[0102] There is no particular limitation on the maximum diameter of each end face of the honeycomb structure. However, a larger maximum diameter can increase the CO2 adsorption capacity, but if it is too large, the manufacturing difficulty increases. Therefore, the maximum diameter is preferably 20 to 450 mm, more preferably 20 to 400 mm, and even more preferably 20 to 350 mm.

[0103] The septa and outer sidewalls of the honeycomb structure contain solid organic compounds, organic binders, and inorganic binders containing amino groups (selected from -NH2, -NHR, -NRR' (R and R' represent organic groups)). The solid organic compound containing amino groups, the organic binder, and the inorganic binder may each contain one type individually or two or more types simultaneously.

[0104] This invention is not intended to be theoretically limited; however, solid organic compounds containing amino groups react with CO2 to form carbamates or bicarbonates, thereby adsorbing CO2. Both organic and inorganic binders contribute to ensuring the strength of the honeycomb structure; however, organic binders also contribute to improved formability, while inorganic binders contribute to improved water resistance and crack suppression during drying. To ensure formability, water-soluble organic binders are preferred; however, the inclusion of water-soluble organic binders in the honeycomb structure reduces water resistance. Therefore, adding normally non-water-soluble inorganic binders to the honeycomb structure helps to suppress the reduction in water resistance.

[0105] In this instruction manual, "non-water soluble" refers to the following property: 11g of the substance used as the test object is placed in 1L of water at 20°C and stirred at 500rpm for 30 minutes. The liquid part is then removed by suction filtration using filter paper 5-C as specified in JIS P3801-1995, and the solid part is dried. The mass at this point is 10g or more.

[0106] From the viewpoint of achieving a good balance between CO2 adsorption performance, crack suppression during drying, and water resistance, in a preferred embodiment, the content of amino-containing solid organic compounds in the partition wall and outer peripheral sidewalls is 40-94% by mass, the content of inorganic binders in the partition wall and outer peripheral sidewalls is 3-50% by mass, and the content of organic binders in the partition wall and outer peripheral sidewalls is 3-20% by mass. In a more preferred embodiment, the content of amino-containing solid organic compounds in the partition wall and outer peripheral sidewalls is 40-90% by mass, the content of inorganic binders in the partition wall and outer peripheral sidewalls is 5-40% by mass, and the content of organic binders in the partition wall and outer peripheral sidewalls is 5-15% by mass. In a further preferred embodiment, the content of amino-containing solid organic compounds in the partition wall and outer peripheral sidewalls is 40-90% by mass, the content of inorganic binders in the partition wall and outer peripheral sidewalls is 5-35% by mass, and the content of organic binders in the partition wall and outer peripheral sidewalls is 5-10% by mass.

[0107] The partition wall and outer peripheral sidewalls may contain components other than amino-containing solid organic compounds, inorganic binders, and organic binders. For example, surfactants and pore-forming materials may be added. However, in a typical embodiment, the total content of amino-containing solid organic compounds, inorganic binders, and organic binders in the partition wall and outer peripheral sidewalls is 90% by mass or more. In a more typical embodiment, the total content of amino-containing solid organic compounds, inorganic binders, and organic binders in the partition wall and outer peripheral sidewalls is 95% by mass or more. Furthermore, the total content of amino-containing solid organic compounds, inorganic binders, and organic binders in the partition wall and outer peripheral sidewalls may also be set to 99% by mass or more.

[0108] From the viewpoint of water resistance, solid organic compounds containing amino groups are preferably non-water-soluble. Furthermore, solid organic compounds containing amino groups may have any one of -NH2, -NHR, or -NRR' (R and R' represent organic groups), or combinations of two or more of them. Among the amino groups, those containing primary amines (-NH2) are particularly preferred as functional groups. Solid organic compounds containing amino groups also preferably contain aromatic rings.

[0109] As a specific example of a solid organic compound containing an amino group, a weakly basic anion exchange resin containing an amino group can be cited. Therefore, for example, a solid organic compound containing an amino group contains one or more selected from styrene-based divinylbenzene polymers containing an amino group (e.g., copolymers of styrene and divinylbenzene) and acrylic-based divinylbenzene polymers containing an amino group (e.g., copolymers of one or both of acrylic acid or methacrylic acid and divinylbenzene).

[0110] From the viewpoint of CO2 adsorption performance, the exchange capacity of a weakly basic anion exchange resin is preferably 0.6 meq / mL or higher, more preferably 1.0 meq / mL or higher, and even more preferably 1.4 meq / mL or higher. Regarding the exchange capacity of the weakly basic anion exchange resin, 10 mL of the resin, measured using the tap method, is treated with hydrochloric acid, excess hydrochloric acid is washed away with ethanol, and ammonia water is allowed to flow through. The amount of chloride ions flowing out at this time is used to determine the capacity.

[0111] Examples of organic adhesives include: methylcellulose, hydroxypropyl methylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, carboxymethylcellulose, polyvinyl alcohol, hydroxyethyl methylcellulose, polyvinyl acetal, polyethylene oxide, polyvinyl butyral, polybutadiene, methacrylate, acrylic, ethylcellulose, silicone, and polyolefins. In particular, the use of water-soluble organic adhesives such as methylcellulose, hydroxypropyl methylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, carboxymethylcellulose, polyvinyl alcohol, hydroxyethyl methylcellulose, polyvinyl acetal, and polyethylene oxide can reduce environmental impact, the hazards posed by organic solvent vapors during drying, and manufacturing costs. A preferred method for preparing the organic adhesive involves placing 11g of the test substance into 1L of water at 60°C, stirring at 500rpm for 30 minutes, cooling to 20°C after stirring, removing the liquid portion by suction filtration using filter paper 5-C as specified in JIS P3801-1995, and drying the solid portion to a mass of 1g or less. A more preferred method for the organic binder is as follows: 21g of the substance being tested is placed in 1L of water at 60°C and stirred at 500rpm for 30 minutes. After stirring, the mixture is cooled to 20°C, and the liquid portion is removed by suction filtration using filter paper 5-C as specified in JIS P3801-1995. The solid portion is then dried, and the mass at this point is 1g or less. A further preferred method for the organic binder is as follows: 31g of the substance being tested is placed in 1L of water at 60°C and stirred at 500rpm for 30 minutes. After stirring, the mixture is cooled to 20°C, and the liquid portion is removed by suction filtration using filter paper 5-C as specified in JIS P3801-1995. The solid portion is then dried, and the mass at this point is 1g or less.

[0112] As inorganic binders, one or more inorganic binders selected from fibrous and granular forms can be cited, with fibrous inorganic binders being preferred. Inorganic binders are generally water-insoluble, thus exhibiting an effect of improving the water resistance of the honeycomb structure. Additionally, they exhibit an effect of inhibiting cracking during drying. Here, "fibrous" inorganic binders refer to inorganic binders with an average aspect ratio of 3 or more. "Granular" inorganic binders refer to inorganic binders with an average aspect ratio of less than 3. The average aspect ratio of the inorganic binder is calculated in the following order: A honeycomb structure test piece is cut to an appropriate size and placed in a crucible, where organic matter is removed by heating in an electric furnace at 500°C. Next, the remaining inorganic binder is dispersed on a scanning electron microscope (SEM) stage, with the magnification matched to the inorganic binder so that 20 inorganic binder particles fall into one field of view. The lengths of the longest and shortest diameters of any 20 inorganic binders are measured, and the average of the longest / shortest diameter is taken as the average aspect ratio of the inorganic binder. The longest diameter of an inorganic adhesive is the longest distance between two parallel lines enclosing the adhesive in an SEM image. The shortest diameter of an inorganic adhesive is the shortest distance between two parallel lines enclosing the adhesive in an SEM image.

[0113] Specific examples of inorganic binders include one or more selected from clay, diatomaceous earth, layered clay minerals, montmorillonite, hydrotalcite, activated clay, acid clay, lithium montmorillonite, halloysite, palygorskite, silica, alumina, talc, chlorite, vermiculite, mica, illite, pyrophyllite, sericite, kaolin, sepiolite, boehmite, palygorskite, and bentonite.

[0114] The inorganic binder preferably contains one or more of the following: sepiolite, boehmite, bentonite, silica, kaolin, and talc; more preferably, it contains sepiolite.

[0115] Therefore, the total content of one or more selected from sepiolite, boehmite, bentonite, silica, kaolin, and talc in the partition wall and outer peripheral sidewall is preferably 3-50% by mass, more preferably 5-40% by mass, and even more preferably 5-35% by mass. Furthermore, the content of sepiolite in the partition wall and outer peripheral sidewall is preferably 3-50% by mass, more preferably 5-40% by mass, and even more preferably 5-35% by mass.

[0116] The average thickness of the partition wall is not particularly limited, but from the viewpoint of ensuring strength, it is preferably 50 μm or more, more preferably 60 μm or more, and even more preferably 70 μm or more. Furthermore, from the viewpoint of suppressing pressure loss, the average thickness of the partition wall is preferably 600 μm or less, more preferably 550 μm or less, and even more preferably 500 μm or less. Therefore, the average thickness of the partition wall is preferably, for example, 50 to 600 μm, more preferably 60 to 550 μm, and even more preferably 70 to 500 μm. In this specification, the thickness of the partition wall is defined as the length of the portion of the line segment connecting the centroids of adjacent compartments in a cross-section perpendicular to the direction of compartment extension, passing through the partition wall. Additionally, the average thickness of the partition wall refers to the average thickness of all partition walls in the honeycomb structure.

[0117] The partition wall can be made of porous material. When the partition wall is porous, from the viewpoint of improving the adsorption performance of the CO2 adsorbent material and suppressing pressure loss when fluid flows through the compartment to a low level, the porosity of the partition wall is preferably 5% or more, more preferably 10% or more, and even more preferably 15% or more. Furthermore, from the viewpoint of ensuring the strength of the honeycomb structure, the porosity of the partition wall is preferably 80% or less, more preferably 75% or less, and even more preferably 70% or less. Therefore, the porosity of the partition wall is preferably, for example, 5 to 80%, more preferably 10 to 75%, and even more preferably 15 to 70%. In this specification, a mercury porosimeter is used to determine the porosity using the mercury infiltration method according to JIS R1655:2003.

[0118] There is no particular limitation on the compartment density (the number of compartments per unit cross-sectional area), but from the viewpoint of increasing the contact area between the adsorbent material on the compartment walls and the introduced gas, 30 compartments / cm² is preferred. 2 The above is more preferably 40 compartments / cm. 2 The above is further preferred to be 50 compartments / cm. 2 That's all. Furthermore, from the viewpoint of ensuring gas flow and minimizing pressure loss, a compartment density of 2000 compartments / cm³ is preferred. 2 The following is more preferably 1200 compartments / cm 2 The following is a further preferred value: 900 compartments / cm² 2 Therefore, the compartment density is preferably, for example, 30 to 2000 compartments / cm². 2 More preferably, it is 40 to 1200 compartments / cm². 2 More preferably, it is 50–900 compartments / cm². 2 In this specification, the cell density is calculated by dividing the number of cells in the honeycomb structure by the area of ​​one end face of the honeycomb structure other than its peripheral sidewalls.

[0119] The shape of the compartments in a cross-section orthogonal to the direction in which the compartments extend (the height direction of the honeycomb structure) is not limited, but is preferably quadrilateral, hexagonal, octagonal, circular, or a combination thereof. Squares and hexagons are particularly preferred. By setting the compartment shape in this way, the pressure loss when fluid flows through the honeycomb structure is reduced.

[0120] (2. CO2 recovery methods)

[0121] According to one embodiment of the present invention, a method for recovering CO2 using the honeycomb structure described in the above embodiments is provided. Specifically, according to one embodiment of the present invention, a method for recovering CO2 is provided, the method comprising: circulating a first gas through a plurality of compartment channels of the honeycomb structure described in the above embodiments; during the passage of the first gas through the plurality of compartment channels, adsorbing CO2 in the first gas by a solid organic compound having an amino group, thereby reducing the CO2 concentration of the first gas as it flows out of the honeycomb structure.

[0122] As the first gas, any gas containing CO2 is acceptable, without any special restrictions. Examples include: ambient air (external atmosphere, indoor or building air), factory exhaust, ship exhaust, and power plant exhaust.

[0123] (3. Manufacturing method of honeycomb structure)

[0124] The following describes a preferred embodiment of the method for manufacturing a honeycomb structure according to the present invention. In one embodiment, the method for manufacturing a honeycomb structure according to the present invention includes: step A, mixing a molding raw material containing a solvent, an amino-containing solid organic compound, an organic binder, and an inorganic binder to prepare a blank; and step B, molding the blank into a honeycomb structure having a plurality of compartment channels that pass through the interior of the honeycomb structure and are formed by partition walls.

[0125] (Process A)

[0126] In step A, molding raw materials containing solvents, amino-containing solid organic compounds, organic binders, and inorganic binders are mixed to produce blanks. Examples of solvents (dispersion media) include water or mixtures of water and organic solvents such as alcohols; water is particularly preferred.

[0127] From the viewpoint of achieving a good balance between CO2 adsorption performance, crack suppression during drying, and water resistance, in a preferred embodiment, the molding raw material contains 40-94% by mass of amino-containing solid organic compounds (excluding solvent), 3-50% by mass of inorganic binders (excluding solvent), and 3-20% by mass of organic binders (excluding solvent). In a more preferred embodiment, the molding raw material contains 40-90% by mass of amino-containing solid organic compounds (excluding solvent), 5-40% by mass of inorganic binders (excluding solvent), and 5-15% by mass of organic binders (excluding solvent). In a further preferred embodiment, the molding raw material contains 40-90% by mass of amino-containing solid organic compounds (excluding solvent), 5-35% by mass of inorganic binders (excluding solvent), and 5-10% by mass of organic binders (excluding solvent).

[0128] The solvent content in the molding raw material is determined in a manner that produces a blank hardness suitable for extrusion. The blank hardness is preferably in the range of 14–26 mm, more preferably 15–25 mm, and even more preferably 16–24 mm. Here, in this specification, the blank hardness is determined using the following method. Figure 3 The attached diagram schematically illustrates the method for measuring the hardness of a billet using a hardness tester. (a) is an overall view of the hardness tester, (b) shows the measurement state when the billet is soft, and (c) shows the measurement state when the billet is relatively hard. Additionally, Figure 4 This is an enlarged view showing the shape and dimensions of the front end of the hardness tester. The conical front end 4 and the support portion 3 are connected by a spring material 2, and they are housed within a cylindrical sheath portion 5, thus forming the hardness tester 1. Figure 3 (a) in the middle. Figure 5This is a graph showing the spring properties of the spring material 2 used. When measuring the hardness of the blank, firstly, a 20mm × 20mm × 20mm cubic sample is taken from the blank. This sample is placed on a flat surface, and the front end 4 of the hardness tester 1 is vertically inserted into the blank 6 or 7 from above until the sheath 5 contacts the blank 6 or 7. Insertion is performed at a sheath speed of 1mm / s. Next, after 3 seconds from when the sheath 5 contacts the blank 6 or 7, the length (a1, a2) of the support 3 protruding above the sheath 5 is read. This value (mm) is defined as the hardness of the blank 6 or 7. Therefore, the larger the value, the higher and harder the blank. In this specification, the average value of measurements taken at any two locations with different measurement positions is taken as the measured hardness value of the blank. It should be noted that L0, L1, and L2 represent the length of the spring material 2. Hardness testers that use this type of hardness measurement method are commercially available, such as the NGK hardness tester (model: NGK-01) manufactured by Nippon Kee Co., Ltd.

[0129] The preferred characteristics, types, and proportions of amino-containing solid organic compounds are as described above, but further details are provided below. The amino-containing solid organic compound used as a molding raw material is preferably porous. Furthermore, regarding the amino-containing solid organic compound, from the perspective of preventing clogging during extrusion, the median particle size (D50) of the cumulative particle size distribution based on the volume scattering method obtained by laser diffraction is preferably 200 μm or less, more preferably 100 μm or less, further preferably 50 μm or less, even more preferably 30 μm or less, and still more preferably 15 μm or less. From the perspective of ease of acquisition, this median particle size (D50) of the amino-containing solid organic compound is preferably 0.1 μm or more, more preferably 0.5 μm or more, and even more preferably 1 μm or more. Therefore, the median particle size (D50) of the amino-containing solid organic compound is, for example, preferably 0.1 to 100 μm, more preferably 0.5 to 50 μm, even more preferably 1 to 50 μm, even more preferably 1 to 30 μm, and still more preferably 1 to 15 μm.

[0130] The preferred properties, types, and proportions of the organic adhesives are as described above. Water-soluble organic adhesives dissolve during mixing. Therefore, there are no particular limitations on shape and size; any organic adhesive in a commonly available form can be used. In the case of non-water-soluble organic adhesives, if an organic solvent is used, it dissolves during mixing. Therefore, there are no particular limitations on shape and size; any organic adhesive in a commonly available form can be used.

[0131] The preferred characteristics, types, and proportions of inorganic binders are as described above; however, the following supplementary information is provided. The inorganic binder used as a molding raw material is preferably porous. Furthermore, regarding the inorganic binder, for the reason of preventing clogging during extrusion molding, the median particle size (D50) determined based on the cumulative particle size distribution using a volume reference obtained by laser diffraction scattering is preferably 200 μm or less, more preferably 100 μm or less, further preferably 50 μm or less, even more preferably 30 μm or less, and still more preferably 15 μm or less. For the reason of ease of acquisition, this median particle size (D50) of the inorganic binder is preferably 0.01 μm or more, more preferably 0.05 μm or more, and even more preferably 0.1 μm or more. Therefore, the median particle size (D50) of the inorganic binder is, for example, preferably 0.01 to 200 μm, more preferably 0.05 to 100 μm, and even more preferably 0.1 to 100 μm.

[0132] Honeycomb structures can be manufactured as follows: a raw material composition containing ceramic raw materials, a dispersion medium, a pore-forming material, and a binder is mixed to form a preform, which is then extruded. Additives such as dispersants can be added to the raw material composition as needed. During extrusion molding, a die with the desired overall shape, cell shape, cell wall thickness, and cell density can be used.

[0133] The mixing can be carried out using a known mixing machine, preferably with the time required for each molding material to be evenly distributed in the billet.

[0134] (Process B)

[0135] In step B, the preform is formed into a honeycomb structure having multiple compartment channels that pass through the interior of the honeycomb structure and are divided by partition walls. Typically, in step B, a honeycomb structure is obtained by extrusion molding. This honeycomb structure has outer peripheral sidewalls and partition walls disposed on the inner peripheral side of the outer peripheral sidewalls and divided into multiple compartments that extend from a first end face to a second end face, forming fluid flow paths (compartment channels). During extrusion molding, a die with a desired overall shape, compartment shape, partition wall thickness, compartment density, etc., can be used.

[0136] Since the freshly formed honeycomb structure contains solvent, it is preferable to remove the solvent through a drying process. The drying process can employ conventionally known drying methods such as hot air drying, microwave drying, dielectric drying, reduced pressure drying, vacuum drying, and freeze drying. Among these, hot air drying, microwave drying, dielectric drying, or a combination thereof are preferred for the purpose of rapidly and uniformly drying the entire formed body. From the viewpoint of suppressing the decomposition of amino-containing solid organic compounds and organic binders during drying, it is preferable to dry the honeycomb structure in an atmospheric atmosphere at 50–150°C, more preferably in an atmospheric atmosphere at 60–140°C, and even more preferably in an atmospheric atmosphere at 70–130°C.

[0137] Example

[0138] The following examples illustrate embodiments for a better understanding of the invention and its advantages; however, the invention is not limited to these examples.

[0139] (1. Raw materials)

[0140] As a solid organic compound containing amino groups, the following commercially available, water-insoluble, weakly basic anion exchange resin is prepared.

[0141] • Styrene-based divinylbenzene polymers with primary amine functional groups and an exchange capacity of 2.0 meq / mL

[0142] • Acrylic divinylbenzene polymers with primary amine functional groups and an exchange capacity of 2.7 meq / mL

[0143] These ion exchange resins are porous granular. The median particle size (D50) when the cumulative particle size distribution on a volume basis was determined using laser diffraction scattering is shown in Table 1.

[0144] Commercially available sepiolite, boehmite, bentonite, colloidal silica, alumina sol, kaolin, and talc were prepared as inorganic binders. The shapes of each and the median particle size (D50) when the cumulative particle size distribution on a volume basis was determined using laser diffraction scattering are shown in Table 1.

[0145] Commercially available methylcellulose was prepared as an organic binder. 31g of the methylcellulose was placed in 1L of water at 60°C and stirred at 500rpm for 30 minutes. After stirring, the mixture was cooled to 20°C. The liquid portion was removed by suction filtration using filter paper 5-C as specified in JIS P3801-1995, and the solid portion was dried. The mass of the solid portion at this point was less than 1g.

[0146] As a solvent, it is used to prepare industrial water.

[0147] (2. Manufacturing of honeycomb structures)

[0148] According to the test number, the amino-containing solid organic compound, inorganic binder, organic binder, and solvent were combined in the mass ratios listed in Table 1 to obtain the molding raw materials for each test number. It should be noted that for each test number, the amount of solvent was adjusted so that the blank hardness measured using an NGK hardness tester (model: NGK-01) manufactured by Nippon Insulator Co., Ltd. reached 17 mm. Next, the molding raw materials were mixed in a vacuum ply mill for 30 minutes to produce cylindrical blanks. The content of the amino-containing solid organic compound, inorganic binder, and organic binder in Table 1 refers to the content when their total is set to 100% by mass. Furthermore, the solvent amount refers to the parts by mass relative to 100 parts by mass of the total amino-containing solid organic compound, organic binder, and inorganic binder. It should be noted that colloidal silica is provided in the form of a dispersion with a solid content concentration of 50% by mass, and alumina sol is provided in the form of a dispersion with a solid content concentration of 5% by mass; however, only the solid content is listed in Table 1.

[0149] Table 1

[0150]

[0151] An extrusion molding machine with a specified die structure was used to form a cylindrical preform, resulting in an undried cylindrical honeycomb structure with quadrilateral cells in a cross-section perpendicular to the direction of cell extension. For each test number of the undried honeycomb structure, the honeycomb structure during extrusion molding was measured visually to evaluate its formability. The formability evaluation was conducted according to the following criteria. The results are shown in the "Formability" column of Table 2.

[0152] 〇: No cracks appeared in the partition wall, and the honeycomb structure was able to take shape.

[0153] △: Cracks can be seen next door, however, the honeycomb structure can still be formed.

[0154] ×: Insufficient shape retention; the honeycomb structure cannot be maintained.

[0155] After high-frequency dielectric heating and drying, the undried honeycomb structure was dried using a microwave dryer in an atmospheric atmosphere at 100°C for 2 minutes. The two end faces were then cut by a specified amount to fabricate the honeycomb structure. For each test number of the honeycomb structure obtained using the above manufacturing method, the end faces were circular with a diameter of 60 mm, and the height (length in the direction of cell extension) was 120 mm. The cell density was 300 cells / cm³. 2The average thickness of the partition walls was 200 μm, and the porosity varied depending on the test number, but all ranged from 15% to 70%. It should be noted that the honeycomb structures were fabricated in quantities required for various tests.

[0156] (3. Composition analysis of honeycomb structures)

[0157] (a) Organic adhesives

[0158] The honeycomb structures obtained using the above manufacturing method were pulverized using an agate mortar and pestle, then dispersed in water at 20°C and stirred for 24 hours using an electromagnetic stirrer. This caused the organic binder to dissolve in the water. The solid residue was then dried, and the mass reduction was calculated. The results showed that for any given honeycomb structure, the mass reduction substantially corresponded to the mass of the organic binder in the molding raw material after solvent removal. Therefore, it can be concluded that the organic binder content can be quantitatively analyzed from the honeycomb structure. Furthermore, the molecular structure of the water in which the organic binder had dissolved was analyzed using Fourier transform infrared spectroscopy (FT-IR), and the molecular structures shown in Table 2 were detected. This confirmed that the organic binder had dissolved in the water.

[0159] (b) Inorganic adhesives

[0160] The honeycomb structures obtained using the above manufacturing method were subjected to intense heating at 800°C for 3 hours to remove the organic binder and amino-containing solid organic compounds. The solid residue was then dried, and its mass was determined. The results showed that for any given honeycomb structure, the mass of the solid residue substantially corresponded to the mass of the inorganic binder in the molding raw material after solvent removal. Therefore, it can be concluded that the content of inorganic binder can be quantitatively analyzed from the honeycomb structure. Furthermore, X-ray diffraction (XRD) was used to analyze the crystalline substances in the solid residue, and the substances shown in Table 2 were detected.

[0161] (c) Solid organic compounds containing amino groups

[0162] For the solid residue, the molecular structure was analyzed using Fourier transform infrared spectroscopy (FT-IR), and the molecular structures shown in Table 2 were detected. This confirmed the presence of a non-water-soluble solid organic compound containing amino groups. Furthermore, based on the results in (a) and (b), for any honeycomb structure with any test number, the solid organic compound containing amino groups substantially corresponds to the remaining mass obtained by subtracting the mass of the organic and inorganic binders from the mass of the honeycomb structure.

[0163] (4. Characteristics of honeycomb structures)

[0164] The following evaluations were conducted on the honeycomb structures of each test number obtained using the manufacturing method described above.

[0165] (a) Evaluation of cracks that develop during drying

[0166] A cylindrical honeycomb structure with a diameter of 60 mm and a height of 120 mm was cut along a direction perpendicular to the height direction to obtain a cylindrical honeycomb structure with a diameter of 60 mm and a height of 100 mm. The state of cracks in the septa when observing the cut surface of the honeycomb structure and the state of crazing-like cracks when observing the outer peripheral surface were confirmed by visual inspection and a ruler, and evaluated according to the following criteria. The results are shown in the "Cracks during drying" column of Table 2.

[0167] 〇: No cracks were observed to the naked eye.

[0168] △: Cracks visible to the naked eye have appeared, but their width is less than 3mm.

[0169] ×: Cracks exceeding 3mm in width will occur.

[0170] (b) Evaluation of water resistance

[0171] A 25mm × 25mm × 25mm cube (length in the direction of compartment extension) was cut near the center of a cylindrical honeycomb structure with a diameter of 60mm and a height of 120mm. Humid air at 55℃ (humidity above 96%) was introduced at a speed of 0.01m... 3 A flow rate of / s was circulated within the compartment of the cut cube for 1 hour. Afterward, the condition of the cube was confirmed by visual inspection and a scale, and evaluated according to the following criteria. The results are shown in the "Water Resistance" column of Table 2.

[0172] 〇: When a cube is placed on a horizontal plane with its three mutually perpendicular faces as the base, the height (with the maximum value measured from the horizontal plane as the height) is measured separately. The difference between the maximum and minimum heights in the three directions is less than 2mm.

[0173] △: The difference between the maximum and minimum height values ​​in the three directions measured using the above method is more than 2 mm.

[0174] ×: During ventilation, the honeycomb structure was not maintained and collapsed.

[0175] (c) Evaluation of CO2 adsorption performance

[0176] The following experiment was conducted on the honeycomb structure. The honeycomb structure was cut into 20mm × 20mm × 10mm pieces. As a pretreatment, the honeycomb structure was heated to 60°C using a dryer to remove CO2. Afterward, it was placed in a 4L sealed container for 20 minutes to absorb atmospheric CO2. A CO2 concentration sensor was placed inside the container, and the decrease in CO2 concentration after 20 minutes was visually observed. The CO2 adsorption performance in this experiment was evaluated according to the following criteria. The results are shown in the "CO2 Adsorption Performance" column of Table 2.

[0177] 〇: A decrease of more than 100 volppm relative to the initial value of CO2 concentration.

[0178] △: A decrease of more than 50 volppm but less than 100 ppm relative to the initial CO2 concentration.

[0179] ×: The reduction in CO2 concentration relative to the initial value is below 50 volppm.

[0180] Table 2

[0181]

[0182] The honeycomb structures of Examples 1-16, which contain amino-containing solid organic compounds, organic binders, and inorganic binders, exhibit CO2 adsorption properties, generate less CO2 during manufacturing, and possess excellent formability, resistance to cracking during drying, and water resistance. In particular, Examples 2-8, which contain a specified amount of fibrous sepiolite, showed the highest evaluation for cracking during drying.

[0183] On the other hand, regarding the honeycomb structure of Comparative Example 1, although it contains a solid organic compound with amino groups and an organic binder, it does not contain an inorganic binder, and the evaluation of cracking and water resistance during drying is insufficient.

[0184] Regarding the honeycomb structure of Comparative Example 2, although it contains a solid organic compound with amino groups and an inorganic binder, it does not contain an organic binder and therefore cannot be molded.

[0185] Explanation of reference numerals in the attached figures

[0186] 1: Hardness tester

[0187] 2: Spring material

[0188] 3: Support section

[0189] 4: Front end

[0190] 5: Sheath

[0191] 6, 7: Billet

[0192] a1, a2: Prominent length

[0193] 100: Honeycomb structure

[0194] 102: Peripheral sidewall

[0195] 104: First end face

[0196] 106: Second end face

[0197] 108: Compartment

[0198] 112: Next door

Claims

1. A honeycomb structure, wherein, It has multiple compartmentalized passages that pass through the interior of the honeycomb structure and are formed by partition walls. The partition wall contains an amino-containing solid organic compound, an organic binder, and an inorganic binder.

2. The honeycomb structure according to claim 1, wherein, Solid organic compounds containing amino groups are insoluble in water.

3. The honeycomb structure according to claim 1 or 2, wherein, The partition wall contains 40-94% by mass of amino-containing solid organic compounds, 3-50% by mass of inorganic binders, and 3-20% by mass of organic binders.

4. The honeycomb structure according to claim 1 or 2, wherein, The partition wall contains 40-90% by mass of amino-containing solid organic compounds, 5-35% by mass of inorganic binders, and 5-10% by mass of organic binders.

5. The honeycomb structure according to claim 1 or 2, wherein, Solid organic compounds containing amino groups are weakly basic anion exchange resins containing amino groups.

6. The honeycomb structure according to claim 1 or 2, wherein, The amino-containing solid organic compound contains one or more selected from amino-containing styrene-based divinylbenzene polymers and amino-containing acrylic-based divinylbenzene polymers.

7. The honeycomb structure according to claim 1 or 2, wherein, Solid organic compounds with amino groups contain primary amines as functional groups.

8. The honeycomb structure according to claim 1 or 2, wherein, Solid organic compounds containing amino groups have aromatic rings.

9. The honeycomb structure according to claim 1 or 2, wherein, Inorganic adhesives contain one or more inorganic adhesives selected from fibrous and granular forms.

10. The honeycomb structure according to claim 1 or 2, wherein, The inorganic binder contains one or more inorganic binders selected from clay, diatomaceous earth, layered clay minerals, montmorillonite, hydrotalcite, activated clay, acid clay, lithium montmorillonite, halloysite, palygorskite, silica, alumina, talc, chlorite, vermiculite, mica, illite, pyrophyllite, sericite, kaolin, sepiolite, boehmite, palygorskite, and bentonite.

11. The honeycomb structure according to claim 10, wherein, Inorganic binders contain one or more of the following: sepiolite, boehmite, bentonite, silica, kaolin, and talc.

12. The honeycomb structure according to claim 11, wherein, The inorganic binder contains sepiolite.

13. A method for manufacturing a honeycomb structure, comprising the following steps: Molding raw materials containing solvents, amino-containing solid organic compounds, organic binders, and inorganic binders are mixed to produce blanks; and The blank is formed into a honeycomb structure having multiple compartment channels that pass through the interior of the honeycomb structure and are formed by partition walls.

14. The method for manufacturing a honeycomb structure according to claim 13, wherein, Solid organic compounds containing amino groups are insoluble in water.

15. The method for manufacturing a honeycomb structure according to claim 13 or 14, wherein, The molding raw material contains 40-94% by mass of amino-containing solid organic compounds other than solvents, 3-50% by mass of inorganic binders other than solvents, and 3-20% by mass of organic binders other than solvents.

16. The method for manufacturing a honeycomb structure according to claim 13 or 14, wherein, The molding raw material contains 40-90% by mass of amino-containing solid organic compounds other than solvents, 5-35% by mass of inorganic binders other than solvents, and 5-10% by mass of organic binders other than solvents.

17. The method for manufacturing a honeycomb structure according to claim 13 or 14, wherein, Solid organic compounds containing amino groups are weakly basic anion exchange resins containing amino groups.

18. The method for manufacturing a honeycomb structure according to claim 13 or 14, wherein, The amino-containing solid organic compound contains one or more selected from amino-containing styrene-based divinylbenzene polymers and amino-containing acrylic-based divinylbenzene polymers.

19. The method for manufacturing a honeycomb structure according to claim 13 or 14, wherein, Solid organic compounds with amino groups contain primary amines as functional groups.

20. The method for manufacturing a honeycomb structure according to claim 13 or 14, wherein, Solid organic compounds containing amino groups have aromatic rings.

21. The method for manufacturing a honeycomb structure according to claim 13 or 14, wherein, Inorganic adhesives contain one or more inorganic adhesives selected from fibrous and granular forms.

22. The method for manufacturing a honeycomb structure according to claim 13 or 14, wherein, The inorganic binder contains one or more inorganic binders selected from clay, diatomaceous earth, layered clay minerals, montmorillonite, hydrotalcite, activated clay, acid clay, lithium montmorillonite, halloysite, palygorskite, silica, alumina, talc, chlorite, vermiculite, mica, illite, pyrophyllite, sericite, kaolin, sepiolite, boehmite, palygorskite, bentonite, colloidal silica, and alumina sol.

23. The method for manufacturing a honeycomb structure according to claim 22, wherein, Inorganic binders contain one or more of the following: sepiolite, boehmite, bentonite, colloidal silica, alumina sol, kaolin, and talc.

24. The method for manufacturing a honeycomb structure according to claim 23, wherein, The inorganic binder contains sepiolite.

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