Honeycomb structure and method for producing same

Abstract

Provided is a honeycomb structure which has adsorption performance of CO2, is easy to form, generates less amount of CO2 during the production process, is not susceptible to the occurrence of a crack during the time of drying, and has improved water resistance. Disclosed is a honeycomb structure which has a plurality of cell channels that pass through the inside of the honeycomb structure and are partitioned by partition walls. The partition walls contain a solid organic compound having an amino group, an organic binder, and an inorganic binder.

Description

Honeycomb structure and manufacturing method thereof

[0001] The present invention relates to a honeycomb structure and a manufacturing method thereof, and more particularly to a honeycomb structure having a CO2 adsorption capability and a manufacturing method thereof.

[0002] To realize a decarbonized society, there is a growing need for technologies that capture and utilize carbon dioxide (CO2) from the atmosphere and exhaust gases. A typical conventional CO2 capture technology is Direct Air Capture (DAC), which adsorbs CO2 from the atmosphere. There are several types of DAC, including liquid absorption, membrane separation, and solid adsorption. In the solid adsorption method, a CO2 adsorption (absorbing) material is generally supported on a substrate. Honeycomb structures, which have a proven track record in purifying automobile exhaust gases, are expected to be a promising substrate for the solid adsorption method.

[0003] Conventional honeycomb structures have generally been manufactured by kneading raw materials containing ceramic raw materials, water, binders, etc. to form a clay, extruding the resulting clay to produce a honeycomb molded body, and then subjecting the honeycomb molded body to a heat treatment such as firing (Patent Document 1). However, heat treatments such as firing require a large amount of energy and often involve the combustion of hydrocarbon fuel, which generates CO2. Furthermore, when an organic binder is used as the binder, combustion during firing generates additional CO2.

[0004] Patent Document 2 describes a honeycomb ceramic substrate for CO2 capture. This honeycomb ceramic substrate for CO2 capture includes a honeycomb ceramic substrate having porous partition walls, a plurality of inorganic support particles in at least one pore of the porous partition walls, and an organic carbon dioxide sorbent supported by at least one of the inorganic support particles. This honeycomb ceramic substrate for CO2 capture is manufactured through a high-temperature heat treatment. Specifically, the honeycomb ceramic substrate obtained through the molding and firing processes is contacted with a support precursor slurry, followed by calcination at a temperature of about 100°C to about 600°C for about 1 hour to about 10 hours, further contacted with an organic CO2 sorbent, and then dried at about 50°C to about 100°C.

[0005] In light of this background, a technique for manufacturing a honeycomb structure without firing is also known. Patent Document 3 describes a honeycomb substrate having a plurality of partition walls extending axially from an inlet end to an outlet end, thereby forming a plurality of flow channels, the honeycomb substrate comprising a mixture of inorganic powder components and an organic binder, in which an amine polymer having functional structural unit groups capable of absorbing CO2 is dispersed in the inorganic powder components of the partition walls of the honeycomb substrate. This honeycomb substrate is formed by a method including the steps of dry-blending inorganic oxide powder components and the organic binder into a mixture, adding a solution of the amine polymer and a solvent to the mixture to form a precursor, kneading the precursor, extruding the kneaded precursor to form a connected monolith having a plurality of partition walls extending axially from the inlet end to the outlet end, thereby forming a plurality of flow channels, and drying the connected monolith to remove the solvent, thereby forming an absorbent structure for capturing CO2.

[0006] Japanese Patent Application Laid-Open No. 2020-019690 Special Publication No. 2018-538137 Special Publication No. 2015-508018

[0007] The honeycomb substrate described in Patent Document 3 uses an amine polymer and has functional structural unit groups that absorb CO2, making it possible to capture CO2. Furthermore, because the honeycomb substrate is manufactured without a high-temperature firing process, it is possible to reduce the amount of CO2 generated during manufacturing. However, the honeycomb substrate described in Patent Document 3 uses an amine polymer, which is easily soluble in water. Furthermore, many of the organic binders that remain without firing are water-soluble. Therefore, the water resistance of the honeycomb substrate described in Patent Document 3 needs improvement. Furthermore, there is also room for improvement in terms of suppressing cracking during drying.

[0008] In view of the above circumstances, an object of the present invention is to provide, in one embodiment, a honeycomb structure that has CO adsorption performance, is easy to form, generates little CO during manufacturing, is less likely to crack during drying, and has improved water resistance.An object of the present invention is, in another embodiment, to provide a method for manufacturing such a honeycomb structure.

[0009] The present inventors have conducted extensive research to solve the above problems and have found that it is advantageous to use a combination of a predetermined CO2 adsorbent, an organic binder, and an inorganic binder as materials for a honeycomb structure. The present invention was completed based on the above findings and is exemplified below.

[0010] [Aspect 1] A honeycomb structure having a plurality of cell channels passing through the honeycomb structure and separated by partition walls, the partition walls containing a solid organic compound having an amino group, an organic binder, and an inorganic binder. [Aspect 2] The honeycomb structure according to Aspect 1, wherein the solid organic compound having an amino group is water-insoluble. [Aspect 3] The honeycomb structure according to Aspect 1 or 2, wherein the content of the solid organic compound having an amino group in the partition walls is 40 to 94 mass%, the content of the inorganic binder in the partition walls is 3 to 50 mass%, and the content of the organic binder in the partition walls is 3 to 20 mass%. [Aspect 4] The honeycomb structure according to Aspect 1 or 2, wherein the content of the solid organic compound having an amino group in the partition walls is 40 to 90 mass%, the content of the inorganic binder in the partition walls is 5 to 35 mass%, and the content of the organic binder in the partition walls is 5 to 10 mass%. [Aspect 5] The honeycomb structure according to any one of Aspects 1 to 4, wherein the solid organic compound having an amino group is a weakly basic anion exchange resin having an amino group. [Aspect 6] The honeycomb structure according to any one of Aspects 1 to 5, wherein the solid organic compound having an amino group contains one or more selected from a styrene-based divinylbenzene polymer having an amino group and an acrylic-based divinylbenzene polymer having an amino group. [Aspect 7] The honeycomb structure according to any one of Aspects 1 to 6, wherein the solid organic compound having an amino group contains a primary amine as a functional group. [Aspect 8] The honeycomb structure according to any one of Aspects 1 to 7, wherein the solid organic compound having an amino group contains an aromatic ring. [Aspect 9] The honeycomb structure according to any one of Aspects 1 to 8, wherein the inorganic binder contains one or more inorganic binders selected from fibrous and granular inorganic binders. [Embodiment 10] The honeycomb structure according to any one of embodiments 1 to 9, wherein the inorganic binder contains one or more inorganic binders selected from clay, diatomaceous earth, layered clay minerals, montmorillonite, hydrotalcite, activated clay, acid clay, hectorite, halloysite, attapulgite, silica, alumina, talc, chlorite, vermiculite, mica, illite, pyrophyllite, sericite, kaolin, sepiolite, boehmite, palygorskite, and bentonite.[Aspect 11] The honeycomb structure according to Aspect 10, wherein the inorganic binder contains one or more selected from sepiolite, boehmite, bentonite, silica, kaolin, and talc. [Aspect 12] The honeycomb structure according to Aspect 11, wherein the inorganic binder contains sepiolite. [Aspect 13] A method for manufacturing a honeycomb structure, comprising the steps of kneading a forming raw material containing a solvent, a solid organic compound having an amino group, an organic binder, and an inorganic binder to prepare a clay, and molding the clay into a honeycomb structure having a plurality of cell channels that pass through the interior of the honeycomb structure and are separated by partition walls. [Aspect 14] The method for manufacturing a honeycomb structure according to Aspect 13, wherein the solid organic compound having an amino group is water-insoluble. [Aspect 15] The method for manufacturing a honeycomb structure according to Aspect 13 or 14, wherein the content of the solid organic compound having an amino group excluding the solvent in the forming raw material is 40 to 94 mass%, the content of the inorganic binder excluding the solvent in the forming raw material is 3 to 50 mass%, and the content of the organic binder excluding the solvent in the forming raw material is 3 to 20 mass%. [Aspect 16] The method for manufacturing a honeycomb structure according to Aspect 13 or 14, wherein the content of the solid organic compound having an amino group excluding the solvent in the forming raw material is 40 to 90 mass%, the content of the inorganic binder excluding the solvent in the forming raw material is 5 to 35 mass%, and the content of the organic binder excluding the solvent in the forming raw material is 5 to 10 mass%. [Aspect 17] The method for manufacturing a honeycomb structure according to any of Aspects 13 to 16, wherein the solid organic compound having an amino group is a weakly basic anion exchange resin having an amino group. [Aspect 18] The method for manufacturing a honeycomb structure according to any one of Aspects 13 to 17, wherein the solid organic compound having an amino group contains one or more selected from a styrene-based divinylbenzene polymer having an amino group and an acrylic-based divinylbenzene polymer having an amino group. [Aspect 19] The method for manufacturing a honeycomb structure according to any one of Aspects 13 to 18, wherein the solid organic compound having an amino group contains a primary amine as a functional group. [Aspect 20] The method for manufacturing a honeycomb structure according to any one of Aspects 13 to 19, wherein the solid organic compound having an amino group contains an aromatic ring.[Embodiment 21] The method for manufacturing a honeycomb structure according to any one of embodiments 13 to 20, wherein the inorganic binder contains one or more inorganic binders selected from fibrous and granular inorganic binders. [Embodiment 22] The method for manufacturing a honeycomb structure according to any one of embodiments 13 to 21, wherein the inorganic binder contains one or more inorganic binders selected from clay, diatomaceous earth, layered clay minerals, montmorillonite, hydrotalcite, activated clay, acid clay, hectorite, halloysite, attapulgite, silica, alumina, talc, chlorite, vermiculite, mica, illite, pyrophyllite, sericite, kaolin, sepiolite, boehmite, palygorskite, bentonite, colloidal silica, and alumina sol. [Aspect 23] The method for manufacturing a honeycomb structure according to Aspect 22, wherein the inorganic binder contains one or more selected from the group consisting of sepiolite, boehmite, bentonite, colloidal silica, alumina sol, kaolin, and talc. [Aspect 24] The method for manufacturing a honeycomb structure according to Aspect 23, wherein the inorganic binder contains sepiolite.

[0011] A honeycomb structure according to one embodiment of the present invention has CO2 adsorption properties, is easy to mold, generates little CO2 during manufacturing, is less likely to crack during drying, and has improved water resistance. Furthermore, the honeycomb structure can be manufactured without high-temperature heat treatment, which reduces the amount of CO2 generated during manufacturing. The honeycomb structure is highly practical as a product that adsorbs CO2 from the atmosphere, and is believed to contribute greatly to the realization of a decarbonized society.

[0012] Fig. 1 is a schematic perspective view of a honeycomb structure according to one embodiment of the present invention. Fig. 2 is a schematic view of a cross section parallel to the height direction (cell extension direction) of a honeycomb structure according to one embodiment of the present invention. Fig. 3 is a diagram for schematically explaining a method for measuring the hardness of a clay using a hardness meter. Fig. 4 is an enlarged view showing the shape and dimensions of the tip of a hardness meter. Fig. 5 is a graph showing the spring properties of a spring material used in a hardness meter.

[0013] Next, an embodiment of the present invention will be described in detail with reference to the drawings. It should be understood that the present invention is not limited to the following embodiment, and that appropriate design changes and improvements may be made based on the ordinary knowledge of those skilled in the art without departing from the spirit of the present invention.

[0014] (1. Honeycomb structure) Fig. 1 shows a schematic perspective view of a honeycomb structure according to one embodiment of the present invention. Fig. 2 shows a schematic view of a cross section parallel to the height direction (cell extension direction) of the honeycomb structure shown in Fig. 1.

[0015] The honeycomb structure 100 according to this embodiment includes an outer peripheral sidewall 102 and partition walls 112 disposed on the inner peripheral side of the outer peripheral sidewall 102, extending from a first end face 104 to a second end face 106, and partitioning a plurality of cells 108 that form fluid flow paths (cell channels). The plurality of cells 108 are arranged parallel to one another. The honeycomb structure 100 according to this embodiment is a flow-through type in which both ends of each cell 108 are open to the first end face 104 and the second end face 106. When a CO2-containing gas such as the atmosphere flows in through the first end face 104 where the inlets of the plurality of cells 108 are located, CO2 is adsorbed as the gas passes through the plurality of cells 108, and a gas with a reduced CO2 concentration flows out from the second end face 106 where the outlets of the plurality of cells 108 are located.

[0016] The end face shape of the honeycomb structure is not particularly limited, and may be, for example, a circular shape, an elliptical shape, a round shape such as a racetrack shape or an oval shape, a polygonal shape such as a triangular shape or a square shape, or other irregular shapes. The overall outer shape of the honeycomb structure may typically be a columnar shape. The honeycomb structure 100 shown in FIG. 1 has a circular end face shape and is cylindrical as a whole.

[0017] When the honeycomb structure is a columnar structure, its height (the length from the first end face to the second end face) is not particularly limited and may be set appropriately depending on the application and required performance. There is also no particular limit on the relationship between the height of the honeycomb structure and the maximum diameter of each end face (the maximum length of the diameters passing through the center of gravity of each end face of the honeycomb structure). Therefore, the height of the honeycomb structure may be longer or shorter than the maximum diameter of each end face.

[0018] The length of the honeycomb structure in the cell extension direction (height direction) is not particularly limited. However, while a longer length can increase the CO adsorption amount, if the length is too long, pressure loss increases. Therefore, the length is preferably 20 to 350 mm, more preferably 20 to 300 mm, and even more preferably 20 to 250 mm.

[0019] There is no particular limitation on the maximum diameter of each end face of the honeycomb structure. However, while a larger maximum diameter can increase the CO adsorption amount, if the maximum diameter is too large it increases the difficulty of manufacturing. Therefore, the maximum diameter is preferably 20 to 450 mm, more preferably 20 to 400 mm, and even more preferably 20 to 350 mm.

[0020] The partition walls and the outer peripheral side walls of the honeycomb structure contain a solid organic compound having an amino group (one or more selected from —NH, —NHR, and —NRR′ (R and R′ represent organic groups)), an organic binder, and an inorganic binder. The solid organic compound having an amino group, the organic binder, and the inorganic binder may each contain one type alone or two or more types simultaneously.

[0021] Although the present invention is not intended to be limited by theory, solid organic compounds having amino groups adsorb CO by reacting with CO to form carbamates or bicarbonates. While both organic and inorganic binders contribute to ensuring the strength of honeycomb structures, organic binders also contribute to improving formability, while inorganic binders also contribute to improving water resistance and suppressing cracking during drying. While using a water-soluble organic binder is preferable to ensure formability, the inclusion of a water-soluble organic binder in a honeycomb structure reduces water resistance. Therefore, adding a generally water-insoluble inorganic binder to a honeycomb structure can have the effect of suppressing the reduction in water resistance.

[0022] In this specification, "water-insoluble" refers to the property that, when 11 g of a substance to be tested is added to 1 L of water at 20°C and stirred at 500 rpm for 30 minutes, the liquid portion is removed by suction filtration using filter paper type 5C specified in JIS P3801-1995, and the solid portion is dried, the mass is 10 g or more.

[0023] From the viewpoint of achieving a good balance between CO adsorption performance, crack suppression during drying, and water resistance, in a preferred embodiment, the content of the solid organic compound having an amino group in the partition walls and the outer peripheral side wall is 40 to 94 mass%, the content of the inorganic binder in the partition walls and the outer peripheral side wall is 3 to 50 mass%, and the content of the organic binder in the partition walls and the outer peripheral side wall is 3 to 20 mass%. In a more preferred embodiment, the content of the solid organic compound having an amino group in the partition walls and the outer peripheral side wall is 40 to 90 mass%, the content of the inorganic binder in the partition walls and the outer peripheral side wall is 5 to 40 mass%, and the content of the organic binder in the partition walls and the outer peripheral side wall is 5 to 15 mass%. In an even more preferred embodiment, the content of the solid organic compound having an amino group in the partition walls and the outer peripheral side wall is 40 to 90 mass%, the content of the inorganic binder in the partition walls and the outer peripheral side wall is 5 to 35 mass%, and the content of the organic binder in the partition walls and the outer peripheral side wall is 5 to 10 mass%.

[0024] The partition walls and the outer peripheral side wall may contain components other than the solid organic compound having an amino group, the inorganic binder, and the organic binder. For example, a surfactant, a pore-forming material, and the like may be added. However, in a typical embodiment, the total content of the solid organic compound having an amino group, the inorganic binder, and the organic binder in the partition walls and the outer peripheral side wall is 90% by mass or more. In a more typical embodiment, the total content of the solid organic compound having an amino group, the inorganic binder, and the organic binder in the partition walls and the outer peripheral side wall is 95% by mass or more. Furthermore, the total content of the solid organic compound having an amino group, the inorganic binder, and the organic binder in the partition walls and the outer peripheral side wall may be 99% by mass or more.

[0025] From the viewpoint of water resistance, it is desirable that the solid organic compound having an amino group be water-insoluble. Furthermore, the solid organic compound having an amino group may have any of -NH2, -NHR, and -NRR' (R and R' represent organic groups), or may have a combination of two or more of these. Among amino groups, it is particularly preferable that the solid organic compound have a primary amine (-NH2) as a functional group. It is also preferable that the solid organic compound having an amino group contain an aromatic ring.

[0026] A specific example of the solid organic compound having an amino group is a weakly basic anion exchange resin having an amino group. Thus, for example, the solid organic compound having an amino group contains one or more selected from a styrene-based divinylbenzene polymer having an amino group (e.g., a copolymer of styrene and divinylbenzene) and an acrylic-based divinylbenzene polymer having an amino group (e.g., a copolymer of divinylbenzene with one or both of acrylic acid and methacrylic acid).

[0027] From the viewpoint of CO2 adsorption performance, the exchange capacity of the weakly basic anion exchange resin is preferably 0.6 meq / mL or more, more preferably 1.0 meq / mL or more, and even more preferably 1.4 meq / mL or more. The exchange capacity of the weakly basic anion exchange resin is measured by the tapping method, in which 10 mL of the ion exchange resin is treated with hydrochloric acid, the excess hydrochloric acid is washed off with ethanol, and ammonia water is passed through, and the amount of chloride ions that flow out is measured.

[0028] Examples of organic binders include methyl cellulose, hydroxypropyl methyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, carboxymethyl cellulose, polyvinyl alcohol, hydroxyethyl methyl cellulose, polyvinyl acetal, polyethylene oxide, polyvinyl butyral, polybutadiene, methacrylic acid esters, acrylic, ethyl cellulose, silicone, and polyolefin. In particular, the use of water-soluble organic binders such as methyl cellulose, hydroxypropyl methyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, carboxymethyl cellulose, polyvinyl alcohol, hydroxyethyl methyl cellulose, polyvinyl acetal, and polyethylene oxide can reduce environmental impact, the risk of organic solvent vapors during drying, and manufacturing costs. The organic binder is prepared by adding 11 g of the substance to be tested to 1 L of water at 60°C, stirring at 500 rpm for 30 minutes, and cooling to 20°C after stirring. The liquid portion is removed by suction filtration using filter paper type 5C as specified in JIS P3801-1995, and the mass of the solid portion when dried is preferably 1 g or less. The organic binder is more preferably such that 21 g of the substance to be tested is added to 1 L of water at 60°C, the mixture is stirred at 500 rpm for 30 minutes, the mixture is cooled to 20°C after stirring is complete, the liquid portion is removed by suction filtration using filter paper type 5C specified in JIS P3801-1995, and the mass of the dried solid portion is 1 g or less.The organic binder is even more preferably such that 31 g of the substance to be tested is added to 1 L of water at 60°C, the mixture is stirred at 500 rpm for 30 minutes, the mixture is cooled to 20°C after stirring is complete, the liquid portion is removed by suction filtration using filter paper type 5C specified in JIS P3801-1995, and the mass of the dried solid portion is 1 g or less.

[0029] Examples of inorganic binders include one or more inorganic binders selected from fibrous and granular binders, with fibrous inorganic binders being preferred. Inorganic binders are generally water-insoluble, and therefore enhance the water resistance of honeycomb structures. They also suppress cracking during drying. Here, "fibrous" inorganic binders refer to inorganic binders with an average aspect ratio of 3 or greater. "Granular" inorganic binders refer to inorganic binders with an average aspect ratio of less than 3. The average aspect ratio of an inorganic binder is determined by the following procedure: A test piece of the honeycomb structure is cut to an appropriate size, placed in a crucible, and heated to 500°C in an electric furnace to remove organic matter. The remaining inorganic binder is then dispersed on a scanning electron microscope (SEM) stage, and the magnification is adjusted to the inorganic binder so that all 20 inorganic binder particles fit within a single field of view. The longest diameter and the shortest diameter of any 20 inorganic binders among them are measured, and the average value of the longest diameter / shortest diameter is taken as the average aspect ratio of the inorganic binder. The longest diameter of one inorganic binder refers to the longest distance between two parallel lines sandwiching the inorganic binder on an SEM image. The shortest diameter of one inorganic binder refers to the shortest distance between two parallel lines sandwiching the inorganic binder on an SEM image.

[0030] Specific examples of inorganic binders include one or more selected from clay, diatomaceous earth, layered clay minerals, montmorillonite, hydrotalcite, activated clay, acid clay, hectorite, halloysite, attapulgite, silica, alumina, talc, chlorite, vermiculite, mica, illite, pyrophyllite, sericite, kaolin, sepiolite, boehmite, palygorskite, and bentonite.

[0031] Among these, the inorganic binder preferably contains one or more selected from sepiolite, boehmite, bentonite, silica, kaolin and talc, and more preferably contains sepiolite.

[0032] Therefore, the total content of one or more selected from sepiolite, boehmite, bentonite, silica, kaolin, and talc in the partition walls and the outer peripheral side wall is preferably 3 to 50 mass%, more preferably 5 to 40 mass%, and even more preferably 5 to 35 mass%. Furthermore, the content of sepiolite in the partition walls and the outer peripheral side wall is preferably 3 to 50 mass%, more preferably 5 to 40 mass%, and even more preferably 5 to 35 mass%.

[0033] The average thickness of the partition walls is not particularly limited, but is preferably 50 μm or more, more preferably 60 μm or more, and even more preferably 70 μm or more, from the viewpoint of ensuring strength. Furthermore, the average thickness of the partition walls is preferably 600 μm or less, more preferably 550 μm or less, and even more preferably 500 μm or less, from the viewpoint of suppressing pressure loss. Therefore, the average thickness of the partition walls 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 walls is defined as the length of the portion of the line segment connecting the centers of gravity of adjacent cells that passes through the partition walls in a cross section perpendicular to the cell extension direction. Furthermore, the average thickness of the partition walls refers to the average thickness of all the partition walls in the honeycomb structure.

[0034] The partition walls can be porous. When the partition walls are porous, the porosity of the partition walls is preferably 5% or more, more preferably 10% or more, and even more preferably 15% or more, from the viewpoint of improving the adsorption performance of the CO adsorbent and from the viewpoint of reducing the pressure loss when a fluid is passed through the cells. Furthermore, the porosity of the partition walls is preferably 80% or less, more preferably 75% or less, and even more preferably 70% or less, from the viewpoint of ensuring the strength of the honeycomb structure. Therefore, the porosity of the partition walls is, for example, preferably 5 to 80%, more preferably 10 to 75%, and even more preferably 15 to 70%. In this specification, the porosity is measured by mercury intrusion porosimetry using a mercury porosimeter in accordance with JIS R1655:2003.

[0035] There is no particular restriction on the cell density (the number of cells per unit cross-sectional area), but from the viewpoint of improving the contact area between the adsorbent on the partition wall and the gas being vented, it is preferable that the cell density be 30 cells / cm. 2 Preferably, the number of cells is 40 or more. 2 More preferably, 50 cells / cm or more. 2 From the viewpoint of ensuring a gas flow path and reducing pressure loss, the cell density is preferably 2000 cells / cm. 2 Preferably, the number of cells per square centimeter is 1200 or less. 2 More preferably, it is 900 cells / cm or less. 2 Therefore, the cell density is, for example, 30 to 2000 cells / cm. 2 It is preferable that the density is 40 to 1200 cells / cm 2 More preferably, it is 50 to 900 cells / cm 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 excluding the outer peripheral side wall.

[0036] Although there are no limitations on the shape of the cells in a cross section perpendicular to the cell extension direction (height direction of the honeycomb structure), a square, hexagon, octagon, circle, or a combination thereof is preferred. Among these, a square and a hexagon are preferred. By using such a cell shape, pressure loss when a fluid is passed through the honeycomb structure is reduced.

[0037] (2. CO2 Capture Method) According to one embodiment of the present invention, there is provided a CO2 capture method using the honeycomb structure according to the embodiment described above. Specifically, according to one embodiment of the present invention, there is provided a CO2 capture method including: flowing a first gas through a plurality of cell channels of the honeycomb structure according to the embodiment described above; adsorbing CO2 in the first gas by a solid organic compound having an amino group while the first gas passes through the plurality of cell channels; and discharging the first gas with a reduced CO2 concentration from the honeycomb structure.

[0038] The first gas is not particularly limited as long as it contains CO2, and examples thereof include environmental air (outdoor air as well as indoor air), factory exhaust gas, ship exhaust gas, and power plant exhaust gas.

[0039] (3. Manufacturing method of honeycomb structure) A preferred example of the manufacturing method of the honeycomb structure of the present invention will be described below. In one embodiment, the manufacturing method of the honeycomb structure of the present invention includes a step A of kneading a forming raw material containing a solvent, a solid organic compound having an amino group, an organic binder, and an inorganic binder to prepare a clay, and a step B of molding, from the clay, a honeycomb structure having a plurality of cell channels that pass through the interior of the honeycomb structure and are partitioned by partition walls.

[0040] (Step A) In step A, a molding raw material containing a solvent, a solid organic compound having an amino group, an organic binder, and an inorganic binder is kneaded to prepare a clay. Examples of the solvent (dispersion medium) include water and a mixed solvent of water and an organic solvent such as alcohol, but water is particularly preferred.

[0041] 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 the solid organic compound having an amino group excluding the solvent in the forming raw material is 40 to 94% by mass, the content of the inorganic binder excluding the solvent in the forming raw material is 3 to 50% by mass, and the content of the organic binder excluding the solvent in the forming raw material is 3 to 20% by mass. In a more preferred embodiment, the content of the solid organic compound having an amino group excluding the solvent in the forming raw material is 40 to 90% by mass, the content of the inorganic binder excluding the solvent in the forming raw material is 5 to 40% by mass, and the content of the organic binder excluding the solvent in the forming raw material is 5 to 15% by mass. In an even more preferred embodiment, the content of the solid organic compound having an amino group excluding the solvent in the forming raw material is 40 to 90% by mass, the content of the inorganic binder excluding the solvent in the forming raw material is 5 to 35% by mass, and the content of the organic binder excluding the solvent in the forming raw material is 5 to 10% by mass.

[0042] The solvent content in the molding raw material is determined to achieve a clay hardness suitable for extrusion. The clay hardness is preferably in the range of 14 to 26 mm, more preferably 15 to 25 mm, and even more preferably 16 to 24 mm. Herein, clay hardness is measured by the following method. Figure 3 is a diagram illustrating a method for measuring clay hardness using a hardness tester. (a) is an overall view of the hardness tester, (b) is the measurement state when the clay is soft, and (c) is the measurement state when the clay is hard. Figure 4 is an enlarged view showing the shape and dimensions of the tip of the hardness tester. The hardness tester 1 is configured by connecting a conical tip 4 and a support portion 3 via a spring material 2, which are housed in a cylindrical sheath portion 5 (Figure 3(a)). Figure 5 is a graph showing the spring properties of the spring material 2 used. To measure the hardness of the puddle, first, a 20 mm x 20 mm x 20 mm cubic sample is taken from the puddle. The sample is placed on a flat surface, and the tip 4 of the hardness meter 1 is inserted vertically from above into the puddle 6, 7 until the sheath 5 contacts it. The insertion is performed at a sheath speed of 1 mm / s. Next, the length (a1, a2) of the support 3 protruding above the sheath 5 is read 3 seconds after the sheath 5 contacts the puddle 6, 7, and this value (mm) is defined as the hardness of the puddle 6, 7. Therefore, the larger the value, the higher the hardness of the puddle. In this specification, the average value of measurements taken at two arbitrary locations is defined as the hardness measurement value of the puddle. Note that L0, L1, and L2 indicate the length of the spring material 2. Hardness testers employing such a hardness measurement method are commercially available, and for example, the NGK-type hardness tester (model number: NGK-01) manufactured by NGK Insulators, Ltd. can be used.

[0043] The preferred properties, types, and compounding ratios of the solid organic compound having an amino group have already been described, but are supplemented below. The solid organic compound having an amino group used as a molding raw material is preferably porous. Furthermore, the median diameter (D50) of the solid organic compound having an amino group, based on a volume-based cumulative particle size distribution obtained by a laser diffraction / scattering method, is preferably 200 μm or less, more preferably 100 μm or less, even more preferably 50 μm or less, even more preferably 30 μm or less, and even more preferably 15 μm or less, to prevent clogging during extrusion. The median diameter (D50) of the solid organic compound having an amino group is preferably 0.1 μm or more, more preferably 0.5 μm or more, and even more preferably 1 μm or more, to prevent clogging during extrusion. Therefore, the median diameter (D50) of the solid organic compound having an amino group 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 even more preferably 1 to 15 μm.

[0044] The preferred properties, types, and compounding ratios of the organic binder have been described above. Water-soluble organic binders dissolve during kneading. Therefore, there are no particular limitations on the shape and size, and it is sufficient to use an organic binder in a generally available form. When a water-insoluble organic binder is used, it dissolves during kneading if an organic solvent is used. Therefore, there are no particular limitations on the shape and size, and it is sufficient to use an organic binder in a generally available form.

[0045] The preferred properties, types, and compounding ratios of the inorganic binder have already been described, but are supplemented below. The inorganic binder used as a molding raw material is preferably porous. Furthermore, the inorganic binder preferably has a median diameter (D50) determined from the volume-based cumulative particle size distribution obtained by a laser diffraction / scattering method of 200 μm or less, more preferably 100 μm or less, even more preferably 50 μm or less, even more preferably 30 μm or less, and even more preferably 15 μm or less, in order to prevent clogging during extrusion molding. The median diameter (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, in order to prevent clogging during extrusion molding. Therefore, the median diameter (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.

[0046] The honeycomb molded body can be produced by kneading a raw material composition containing ceramic raw materials, a dispersion medium, a pore-forming material, and a binder to form a puddle, and then extruding the puddle. Additives such as dispersants can be blended into the raw material composition as needed. During extrusion molding, a die having the desired overall shape, cell shape, partition wall thickness, cell density, etc. can be used.

[0047] The kneading can be carried out using a known kneader, and it is desirable to carry out the kneading for a time required for each forming raw material to be uniformly distributed in the clay.

[0048] (Step B) In step B, a honeycomb structure having a plurality of cell channels that pass through the interior of the honeycomb structure and are separated by partition walls is formed from the clay. Typically, in step B, a honeycomb structure having an outer peripheral side wall and partition walls that are disposed on the inner peripheral side of the outer peripheral side wall, extend from the first end face to the second end face, and separate a plurality of cells that form fluid flow paths (cell channels) is extrusion-molded. During extrusion molding, a die having a desired overall shape, cell shape, partition wall thickness, cell density, etc. can be used.

[0049] Since the honeycomb structure immediately after molding contains a solvent, it is desirable to remove the solvent by a drying process. In the drying process, conventionally known drying methods such as hot air drying, microwave drying, dielectric drying, reduced pressure drying, vacuum drying, and freeze drying can be used. Among these, hot air drying, microwave drying, and dielectric drying, or a combination thereof, are preferred because they can dry the entire molded body quickly and uniformly. From the viewpoint of suppressing decomposition of the solid organic compound having an amino group and the organic binder during drying, it is preferable to dry the honeycomb structure in an air atmosphere at 50 to 150°C, more preferably in an air atmosphere at 60 to 140°C, and even more preferably in an air atmosphere at 70 to 130°C.

[0050] The following examples are provided to provide a better understanding of the present invention and its advantages, but the present invention is not limited to these examples.

[0051] (1. Raw Materials) The following commercially available water-insoluble weakly basic anion exchange resins were prepared as solid organic compounds having amino groups: a styrene-based divinylbenzene polymer having a primary amine as a functional group with an exchange capacity of 2.0 meq / mL; and an acrylic divinylbenzene polymer having a primary amine as a functional group with an exchange capacity of 2.7 meq / mL. These ion exchange resins were porous granular. The median diameter (D50) of the cumulative particle size distribution on a volume basis measured by laser diffraction / scattering is shown in Table 1.

[0052] Commercially available inorganic binders were prepared: sepiolite, boehmite, bentonite, colloidal silica, alumina sol, kaolin, and talc. Table 1 shows the shape of each binder and the median diameter (D50) of each binder measured by a volume-based cumulative particle size distribution using a laser diffraction / scattering method.

[0053] As an organic binder, commercially available methyl cellulose was prepared. 31 g of this methyl cellulose was added to 1 L of water at 60°C, stirred at 500 rpm for 30 minutes, cooled to 20°C after stirring, and the liquid portion was removed by suction filtration using filter paper type 5C specified in JIS P3801-1995. The mass of the solid portion after drying was 1 g or less.

[0054] Industrial water was used as the solvent.

[0055] (2. Manufacturing of honeycomb structure) A solid organic compound having an amino group, an inorganic binder, an organic binder, and a solvent were blended in the mass ratios shown in Table 1 according to the test number to obtain a forming raw material for each test number. The amount of solvent blended was adjusted for each test number so that the clay hardness measured using an NGK hardness tester (model number: NGK-01) manufactured by NGK Insulators, Ltd. was 17 mm. Next, the forming raw material was kneaded for 30 minutes using a vacuum kneader to prepare a cylindrical clay. The contents of the solid organic compound having an amino group, the inorganic binder, and the organic binder in Table 1 refer to the contents when the total is 100 mass%. The amount of solvent refers to parts by mass relative to a total of 100 parts by mass of the solid organic compound having an amino group, the organic binder, and the inorganic binder. The colloidal silica was provided as a dispersion with a solid content of 50% by mass, and the alumina sol was provided as a dispersion with a solid content of 5% by mass, but only the solid content was included in Table 1.

[0056]

[0057] The obtained cylindrical clay was molded using an extrusion molding machine having a predetermined die structure to obtain a cylindrical undried honeycomb structure in which each cell had a square shape in a cross section perpendicular to the cell extension direction. For the undried honeycomb structure corresponding to each test number, the honeycomb structure during extrusion molding was visually measured to evaluate its moldability. The moldability was evaluated according to the following criteria. The results are shown in the "Moldability" column in Table 2. ◯: A honeycomb structure was molded without any cracks occurring in the partition walls. △: Cracks were observed in the partition walls, but a honeycomb structure was molded. ×: Shape retention was insufficient, and the honeycomb structure could not be maintained.

[0058] The obtained undried honeycomb structure was dried by high-frequency dielectric heating, and then dried for 2 minutes in an air atmosphere at a temperature of 100°C using a microwave dryer, and both end faces were cut to a predetermined length to prepare a honeycomb structure. The honeycomb structure obtained by the above manufacturing method according to each test number had a circular end face with a diameter of 60 mm and a height (length in the cell extension direction) of 120 mm. The cell density was 300 cells / cm. 2 The average thickness of the partition walls was 200 μm, and the porosity varied depending on the test number but was in the range of 15 to 70%. The honeycomb structures were prepared in the number required for each test.

[0059] (3. Component Analysis of Honeycomb Structures) (a) Organic Binder The honeycomb structures according to each test number obtained by the above manufacturing method were crushed in an agate mortar, dispersed in water at 20°C, and stirred for 24 hours with a magnetic stirrer. This allowed the organic binder to dissolve in the water. The solid residue was then dried to determine the mass loss. It was found that for each honeycomb structure according to the test number, the mass loss essentially corresponded to the mass of the organic binder in the raw material excluding the solvent. Therefore, it was found that the organic binder content could be quantitatively analyzed from the honeycomb structure. Furthermore, the molecular structure of the water into which the organic binder had been dissolved was analyzed by Fourier transform infrared spectroscopy (FT-IR), and the molecular structure shown in Table 2 was detected. This confirmed that the organic binder had dissolved in the water.

[0060] (b) Inorganic Binder: The honeycomb structures obtained by the above manufacturing method were ignited at 800°C for 3 hours to remove the organic binder and the solid organic compound having an amino group. The solid residue was then dried and its mass was determined. It was found that for all honeycomb structures, the mass of the solid residue substantially corresponded to the mass of the inorganic binder in the raw material excluding the solvent. Therefore, it was found that the inorganic binder content can be quantitatively analyzed from the honeycomb structure. Furthermore, the solid residue was analyzed for crystalline substances using X-ray diffraction (XRD), and the substances shown in Table 2 were detected.

[0061] (c) Solid organic compound having an amino group When the molecular structure of the solid residue was analyzed by Fourier transform infrared spectroscopy (FT-IR), the molecular structure shown in Table 2 was detected. This confirmed the presence of a water-insoluble solid organic compound having an amino group. Furthermore, from the results of (a) and (b), for the honeycomb structures related to any test number, the amount of the solid organic compound having an amino group substantially corresponded to the remaining mass obtained by subtracting the mass of the organic binder and the inorganic binder from the mass of the honeycomb structure.

[0062] (4. Characteristics of Honeycomb Structure) The honeycomb structures having the respective test numbers obtained by the above manufacturing method were evaluated as follows.

[0063] (a) Evaluation of cracks occurring during drying A cylindrical honeycomb structure with a diameter of 60 mm and a height of 120 mm was cut in a direction perpendicular to the height direction to cut out a cylindrical honeycomb structure with a diameter of 60 mm and a height of 100 mm. The state of cracks in the partition walls when observing the cut surface of the cut honeycomb structure and the state of fissure-like cracks when observing the outer peripheral surface were confirmed visually and with a scale, and evaluated according to the following criteria. The results are shown in the "Cracks during drying" column in Table 2. ◯: No cracks observed visually △: Cracks observed visually but less than 3 mm wide ×: Cracks with a width of more than 3 mm occurred

[0064] (b) Evaluation of Water Resistance A cube of 25 mm x 25 mm x 25 mm (length in the cell extension direction) was cut out from near the center of a cylindrical honeycomb structure having a diameter of 60 mm and a height of 120 mm. Moist air (humidity 96% or more) at 55°C was poured into the cells of the cut cube to a depth of 0.01 m. 3 / s for 1 hour. Thereafter, the state of the cube was checked visually and using a scale, and evaluated according to the following criteria. The results are shown in the "Water Resistance" column in Table 2. ◯: The cube was placed on a horizontal surface with its three perpendicular faces at the bottom, and the height (the maximum value from the horizontal plane was taken as the height) was measured, and the difference between the maximum and minimum heights measured in the three directions was less than 2 mm. △: The difference between the maximum and minimum heights measured in the three directions by the above method was 2 mm or more. ×: The honeycomb structure was not maintained during ventilation and collapsed.

[0065] (c) Evaluation of CO2 adsorption performance The following test was carried out on the honeycomb structure. The honeycomb structure was cut into a size of 20 mm x 20 mm x 10 mm. As a pretreatment, the honeycomb structure was heated to 60°C in a dryer to desorb CO2. Then, it was left in a 4 L sealed container for 20 minutes to absorb CO2 from the atmosphere. A CO2 concentration sensor was installed in the container, and the decrease in CO2 concentration after 20 minutes was visually confirmed. The CO2 adsorption performance in this test was evaluated according to the following criteria. The results are shown in the "CO2 adsorption performance" column in Table 2. ◯: The decrease in CO2 concentration from the initial value was more than 100 vol ppm. △: The decrease in CO2 concentration from the initial value was more than 50 vol ppm and 100 ppm or less. ×: The decrease in CO2 concentration from the initial value was 50 vol ppm or less.

[0066]

[0067] The honeycomb structures of Examples 1 to 16, which contained a solid organic compound having an amino group, an organic binder, and an inorganic binder, had CO2 adsorption capabilities, generated little CO2 during manufacturing, and also had excellent properties in formability, cracking during drying, and water resistance. In particular, Examples 2 to 8, which contained a predetermined amount of fibrous sepiolite, had the highest evaluation of cracking during drying. On the other hand, the honeycomb structure of Comparative Example 1 contained a solid organic compound having an amino group and an organic binder but no inorganic binder, and therefore was insufficient in the evaluation of cracking during drying and water resistance. The honeycomb structure of Comparative Example 2 contained a solid organic compound having an amino group and an inorganic binder but no organic binder, and therefore could not be formed.

[0068] REFERENCE SIGNS LIST 1: Hardness tester 2: Spring material 3: Support portion 4: Tip portion 5: Sheath portion 6, 7: Clay a1, a2: Projecting length 100: Honeycomb structure 102: Peripheral side wall 104: First end face 106: Second end face 108: Cell 112: Partition wall

Claims

1. A honeycomb structure having a plurality of cell channels passing through the interior of the honeycomb structure and separated by partition walls, the partition walls containing a solid organic compound having an amino group, an organic binder and an inorganic binder.

2. The honeycomb structure according to claim 1, wherein the solid organic compound having an amino group is water-insoluble.

3. A honeycomb structure as described in claim 1 or 2, wherein the content of the solid organic compound having an amino group in the partition walls is 40 to 94 mass%, the content of the inorganic binder in the partition walls is 3 to 50 mass%, and the content of the organic binder in the partition walls is 3 to 20 mass%.

4. A honeycomb structure as described in claim 1 or 2, wherein the content of the solid organic compound having an amino group in the partition walls is 40 to 90 mass%, the content of the inorganic binder in the partition walls is 5 to 35 mass%, and the content of the organic binder in the partition walls is 5 to 10 mass%.

5. A honeycomb structure according to claim 1 or 2, wherein the solid organic compound having an amino group is a weakly basic anion exchange resin having an amino group.

6. A honeycomb structure according to claim 1 or 2, wherein the solid organic compound having an amino group contains at least one 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.

7. A honeycomb structure according to claim 1 or 2, wherein the solid organic compound having an amino group contains a primary amine as a functional group.

8. A honeycomb structure according to claim 1 or 2, wherein the solid organic compound having an amino group contains an aromatic ring.

9. The honeycomb structure according to claim 1 or 2, wherein the inorganic binder contains one or more inorganic binders selected from fibrous and granular inorganic binders.

10. A honeycomb structure as described in 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, hectorite, halloysite, attapulgite, silica, alumina, talc, chlorite, vermiculite, mica, illite, pyrophyllite, sericite, kaolin, sepiolite, boehmite, palygorskite, and bentonite.

11. The honeycomb structure according to claim 10, wherein the inorganic binder contains one or more selected from the group consisting of 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: a step of kneading a forming raw material containing a solvent, a solid organic compound having an amino group, an organic binder, and an inorganic binder to prepare a clay; and a step of forming a honeycomb structure from the clay, the honeycomb structure having a plurality of cell channels that pass through the inside of the honeycomb structure and are separated by partition walls.

14. The method for manufacturing a honeycomb structure according to claim 13, wherein the solid organic compound having an amino group is water-insoluble.

15. A method for manufacturing a honeycomb structure as described in claim 13 or 14, wherein the content of the solid organic compound having an amino group excluding the solvent in the forming raw material is 40 to 94 mass%, the content of the inorganic binder excluding the solvent in the forming raw material is 3 to 50 mass%, and the content of the organic binder excluding the solvent in the forming raw material is 3 to 20 mass%.

16. A method for manufacturing a honeycomb structure as described in claim 13 or 14, wherein the content of the solid organic compound having an amino group excluding the solvent in the forming raw material is 40 to 90 mass %, the content of the inorganic binder excluding the solvent in the forming raw material is 5 to 35 mass %, and the content of the organic binder excluding the solvent in the forming raw material is 5 to 10 mass %.

17. A method for manufacturing a honeycomb structure according to claim 13 or 14, wherein the solid organic compound having an amino group is a weakly basic anion exchange resin having an amino group.

18. A method for manufacturing a honeycomb structure according to claim 13 or 14, wherein the solid organic compound having an amino group contains one or more selected from a styrene-based divinylbenzene polymer having an amino group and an acrylic-based divinylbenzene polymer having an amino group.

19. A method for manufacturing a honeycomb structure according to claim 13 or 14, wherein the solid organic compound having an amino group contains a primary amine as a functional group.

20. A method for manufacturing a honeycomb structure according to claim 13 or 14, wherein the solid organic compound having an amino group contains an aromatic ring.

21. A method for manufacturing a honeycomb structure according to claim 13 or 14, wherein the inorganic binder contains one or more kinds of inorganic binders selected from fibrous and granular inorganic binders.

22. A method for manufacturing a honeycomb structure as described in 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, hectorite, halloysite, attapulgite, silica, alumina, talc, chlorite, vermiculite, mica, illite, pyrophyllite, sericite, kaolin, sepiolite, boehmite, palygorskite, bentonite, colloidal silica, and alumina sol.

23. A method for manufacturing a honeycomb structure according to claim 22, wherein the inorganic binder contains one or more selected from the group consisting of 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.

Images