WO2025163832A1 - Honeycomb structure, method for manufacturing same, and carbon dioxide recovery device - Google Patents

Abstract

This honeycomb structure has a plurality of cell channels (cells 108) that pass through the interior of the honeycomb structure 100 and are partitioned by a partition wall 112. The partition wall 112 contains a carbon dioxide adsorbent, a water-resistance-imparting agent, and an organic binder.

Description

Honeycomb structure, its manufacturing method, and carbon dioxide recovery device

The present invention relates to a honeycomb structure, a manufacturing method thereof, and a carbon dioxide capture device.

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. Among these, in the solid adsorption method, a _CO2 adsorption (absorbing) material is generally supported on a substrate. As a substrate to be used in the solid adsorption method, honeycomb structures, which have a proven track record in purifying automobile exhaust gases, are expected to be used.

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, resulting in the generation of _CO2 . Furthermore, when an organic binder is used as the binder, combustion during firing generates additional _CO2 .

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.

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 the inlet end to the 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 that absorb CO ₂ 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 CO ₂ capture.

Japanese Patent Application Laid-Open No. 2020-019690 Special table 2018-538137 publication Special table 2015-508018 publication

The honeycomb substrate described in Patent Document 3 uses an amine polymer and has a functional structural unit group that absorbs _CO2 , making it possible to capture _CO2 . Furthermore, since 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 a water-soluble amine polymer that easily dissolves in water. Furthermore, much of the organic binder that remains without firing is also water-soluble. Therefore, the water resistance of the honeycomb substrate described in Patent Document 3 leaves room for improvement.

The present invention was made to solve the above-mentioned problems, and aims to provide a honeycomb structure with excellent water resistance, a manufacturing method thereof, and a carbon dioxide capture device.

As a result of extensive research to solve the above problems, the inventors discovered that water resistance could be improved by using a combination of a carbon dioxide adsorbent, a water resistance imparting agent, and an organic binder as materials for honeycomb structures, leading to the completion of the present invention. Specifically, the present invention is exemplified as follows:

[1] A honeycomb structure,
a plurality of cell channels passing through the honeycomb structure and separated by partition walls;
The honeycomb structure, wherein the partition walls contain a carbon dioxide adsorbent, a water resistance imparting agent, and an organic binder.

[2] The honeycomb structure described in [1], wherein the partition walls further contain an inorganic binder.

[3] The honeycomb structure according to [1] or [2], wherein the water-resistant agent is one or more selected from silicones, partially benzalized polyvinyl alcohol, (meth)acrylic resin, polyacrylate resin, polynitrile resin, polychloroprene, polyvinyl chloride, polyvinylidene fluoride, polyolefins, poly(tetrafluoroethylene), polyurethanes, phenols, urethanes, polyvinyl butyral, ethylene-vinyl acetates, and synthetic rubbers.

[4] A honeycomb structure according to any one of [1] to [3], wherein the partition walls have a peak attributable to the Si-C bending angle when measured by FT-IR (Fourier transform infrared spectroscopy).

[5] The honeycomb structure described in any one of [1] to [4], wherein the carbon dioxide adsorbent is dispersed in the partition walls.

[6] A honeycomb structure according to any one of [1] to [5], wherein the organic binder is one or more selected from methyl cellulose, hydroxypropyl methyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, carboxymethyl cellulose, polyvinyl alcohol, hydroxyethyl methyl cellulose, polyethylene oxide, polybutadiene, acrylic acid esters, methacrylic acid esters, and ethyl cellulose.

[7] A honeycomb structure according to any one of [1] to [6], having a water-resistant layer on the surface of the partition walls.

[8] The honeycomb structure described in [7], wherein the water-resistant layer contains one or more materials selected from silicones, partially benzalized polyvinyl alcohol, (meth)acrylic resin, polyacrylate resin, polynitrile resin, polychloroprene, polyvinyl chloride, polyvinylidene fluoride, polyolefins, poly(tetrafluoroethylene), polyurethanes, phenols, urethanes, polyvinyl butyral, ethylene-vinyl acetates, and synthetic rubbers.

[9] A honeycomb structure according to any one of [1] to [8], having a carbon dioxide adsorption capacity of 0.5 mol/kg or more.

[10] The honeycomb structure according to any one of [1] to [9], wherein the carbon dioxide adsorbent is a solid organic compound having an amino group.

[11] The honeycomb structure according to [10], wherein the solid organic compound is a weakly basic anion exchange resin having an amino group.

[12] The honeycomb structure described in [10], wherein the solid organic compound contains at least one selected from a styrene-divinylbenzene copolymer having an amino group and a (meth)acrylic acid-divinylbenzene copolymer having an amino group.

[13] A step of kneading a molding raw material containing a solvent, a carbon dioxide adsorbent, a water resistance imparting agent, and an organic binder to prepare a clay;
a step of forming the clay into a honeycomb formed body, the honeycomb formed body having a plurality of cell channels passing through the interior and separated by partition walls;
and drying the honeycomb formed body.

[14] The method for manufacturing a honeycomb structure according to [13], wherein the forming raw material further contains an inorganic binder.

[15] The method for manufacturing a honeycomb structure according to [13] or [14], wherein the water-resistant agent is one or more selected from silicones, partially benzalized polyvinyl alcohol, (meth)acrylic resin, polyacrylate resin, polynitrile resin, polychloroprene, polyvinyl chloride, polyvinylidene fluoride, polyolefins, poly(tetrafluoroethylene), polyurethanes, phenols, urethanes, polyvinyl butyral, ethylene-vinyl acetates, and synthetic rubbers.

[16] A method for manufacturing a honeycomb structure according to any one of [13] to [15], wherein the organic binder is one or more selected from methyl cellulose, hydroxypropyl methyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, carboxymethyl cellulose, polyvinyl alcohol, hydroxyethyl methyl cellulose, polyethylene oxide, polybutadiene, acrylic acid esters, methacrylic acid esters, and ethyl cellulose.

[17] A method for manufacturing a honeycomb structure according to any one of [13] to [16], further comprising a step of forming a water-resistant layer on the surface of the partition wall.

[18] A method for manufacturing a honeycomb structure according to any one of [13] to [17], wherein the carbon dioxide adsorbent is a solid organic compound having an amino group.

[19] The method for manufacturing a honeycomb structure according to [18], wherein the solid organic compound is a weakly basic anion exchange resin having an amino group.

[20] The method for manufacturing a honeycomb structure according to [18], wherein the solid organic compound contains at least one selected from a styrene-divinylbenzene copolymer having an amino group and a (meth)acrylic acid-divinylbenzene copolymer having an amino group.

[21] A carbon dioxide capture device comprising one or more honeycomb structures described in any one of [1] to [12].

The present invention provides a honeycomb structure with excellent water resistance, a method for manufacturing the same, and a carbon dioxide capture device.

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

The honeycomb structure of the present invention has a plurality of cell channels that pass through the honeycomb structure and are separated by partition walls, and the partition walls contain a carbon dioxide adsorbent, a water resistance imparting agent, and an organic binder. This configuration of the honeycomb structure of the present invention can improve water resistance. Therefore, when carbon dioxide (hereinafter sometimes referred to as " _CO2 ") is desorbed from the carbon dioxide adsorbent that has adsorbed carbon dioxide using a desorption gas (which may be heated), such as water vapor, outflow and deterioration of the carbon dioxide adsorbent can be suppressed. Furthermore, the honeycomb structure of the present invention is highly practical as a product that adsorbs carbon dioxide from the atmosphere, and is believed to greatly contribute to the realization of a decarbonized society.

Embodiments of the present invention will now be described in detail with reference to the drawings. The present invention is not limited to the following embodiments, and it should be understood that modifications and improvements made to the following embodiments, based on the common knowledge of those skilled in the art, as long as they do not deviate from the spirit of the present invention, also fall within the scope of the present invention.

(1. Honeycomb structure)
Fig. 1 shows a schematic perspective view of a honeycomb structure according to an embodiment of the present invention, and 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.

As shown in FIGS. 1 and 2 , a honeycomb structure 100 includes an outer peripheral wall 102 and partition walls 112 disposed on the inner peripheral side of the outer peripheral wall 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 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.

The end face shape of the honeycomb structure 100 is not particularly limited, but can 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 100 can typically be a columnar shape. The honeycomb structure 100 shown in Figure 1 has a circular end face shape and is cylindrical overall.

When the honeycomb structure 100 is a columnar body, there are no particular restrictions on its height (the length from the first end face 104 to the second end face 106) and it may be set appropriately depending on the application and required performance. There are also no particular restrictions on the relationship between the height of the honeycomb structure 100 and the maximum diameter of each end face (referring to the maximum length of the diameter passing through the center of gravity of each end face of the honeycomb structure 100). Therefore, the height of the honeycomb structure 100 may be longer than the maximum diameter of each end face, or the height of the honeycomb structure 100 may be shorter than the maximum diameter of each end face.

There is no particular limitation on the length in the extension direction (height direction) of the cells 108 of the honeycomb structure 100. However, while a longer length can increase the amount of _CO2 adsorption, if the length is too long, pressure loss increases, so the length is preferably 20 to 350 mm, more preferably 20 to 300 mm, and even more preferably 20 to 250 mm.

There is no particular limitation on the maximum diameter of each end face of the honeycomb structure 100. However, while a larger maximum diameter can increase the amount of _CO2 adsorption, if the maximum diameter is too large, manufacturing becomes more difficult. Therefore, the maximum diameter is preferably 20 to 450 mm, more preferably 20 to 400 mm, and even more preferably 20 to 350 mm.

The partition walls 112 that make up the honeycomb structure 100 contain a carbon dioxide adsorbent, a water resistance agent, and an organic binder. Similarly to the partition walls 112, the outer peripheral walls 102 that make up the honeycomb structure 100 can also contain a carbon dioxide adsorbent, a water resistance agent, and an organic binder. The carbon dioxide adsorbent, water resistance agent, and organic binder may each contain one type alone, or two or more types in combination.

The carbon dioxide adsorbent is preferably dispersed in the partition walls 112. Similarly, the carbon dioxide adsorbent is preferably dispersed in the outer peripheral wall 102. By dispersing the carbon dioxide adsorbent in the partition walls 112 and the outer peripheral wall 102 in this manner, the amount of _CO2 adsorption can be increased.

The carbon dioxide adsorbent is not particularly limited, and known adsorbents can be used. Among them, the carbon dioxide adsorbent is preferably a solid organic compound having an amino group (one or more selected from _-NH2 , -NHR, and -NRR' (R and R' represent organic groups)). Although the present invention is not intended to be limited by theory, a solid organic compound having an amino group can adsorb _CO2 by reacting with _CO2 to produce a carbamate or bicarbonate.

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.

Specific examples of solid organic compounds having amino groups include weakly basic anion exchange resins having amino groups. Therefore, for example, the solid organic compound having amino groups can contain one or more compounds selected from a styrene-divinylbenzene copolymer having amino groups and a (meth)acrylic acid-divinylbenzene copolymer having amino groups.

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.

The content of the carbon dioxide adsorbent in the partition wall 112 (and the outer peripheral wall 102 as necessary) is not particularly limited, but from the viewpoint of achieving a good balance between _CO2 adsorption performance, crack suppression during drying, and water resistance, it is preferably 40 to 94 mass%, more preferably 40 to 90 mass%, and even more preferably 40 to 80 mass%.

The water resistance imparting agent is not particularly limited, and any known agent can be used. By using the water resistance imparting agent, the water resistance of the honeycomb structure 100 can be improved.
Examples of water-resistance-imparting agents include silicones, partially benzalated polyvinyl alcohol, (meth)acrylic resins, polyacrylate resins, polynitrile resins such as carboxylated acrylic nitrile-butadiene copolymers, polychloroprene, polyvinyl chloride, polyvinylidene fluoride, polyolefins, poly(tetrafluoroethylene), polyurethanes, phenols, urethanes, polyvinyl butyral, ethylene-vinyl acetates, and synthetic rubbers. These can be used alone or in combination of two or more. Among these, resins with high _CO2 permeability are preferred as water-resistance-imparting agents, and silicones are particularly preferred. Because silicones have high _CO2 permeability, _CO2 adsorption performance can be maintained even if the surface of the carbon dioxide adsorbent is covered with silicones.

Silicones are not particularly limited, but include silicone resin, silicone wax, silicone rubber, silicone oil, and copolymers of silicone and other monomers. These can be used alone or in combination of two or more types.

The partition walls 112 (and the outer peripheral wall 102, if necessary) preferably have a peak derived from a Si-C bending angle when measured by Fourier transform infrared spectroscopy (FT-IR). If such a peak is present, it can be considered that silicones are contained in the partition walls 112 (and the outer peripheral wall 102, if necessary).
Here, in FT-IR, the peak due to the Si—C bending angle is a peak in the vicinity of 1250 to 1270 cm ⁻¹ in the FT-IR spectrum. The FT-IR spectrum is obtained by crushing the honeycomb structure 100 in an agate mortar and measuring the resulting crushed material with a Fourier transform infrared spectrophotometer.

The content of the water-resistance imparting agent in the partition wall 112 (and the outer peripheral wall 102, if necessary) is not particularly limited, but from the viewpoint of water resistance, it is preferably 2 to 20% by mass, more preferably 3 to 18% by mass, and even more preferably 4 to 15% by mass.

The organic binder is not particularly limited, and any known organic binder can be used. By using an organic binder, the moldability can be improved and the strength of the honeycomb structure 100 can be improved.
Examples of organic binders include methyl cellulose, hydroxypropyl methyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, carboxymethyl cellulose, polyvinyl alcohol, hydroxyethyl methyl cellulose, polyethylene oxide, polybutadiene, acrylic acid esters, methacrylic acid esters, and ethyl cellulose. These can be used alone or in combination of two or more. Furthermore, among these, 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, and polyethylene oxide can reduce environmental impact, the risk of organic solvent vapor during drying, and production costs.

For example, 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, cooling to 20°C after stirring is complete, removing the liquid portion by suction filtration using filter paper type 5C specified in JIS P3801:1995, and drying the solid portion, which preferably has a mass of 1 g or less. More preferably, the organic binder is prepared by adding 21 g of the substance to be tested to 1 L of water at 60°C, stirring at 500 rpm for 30 minutes, cooling to 20°C after stirring is complete, removing the liquid portion by suction filtration using filter paper type 5C specified in JIS P3801:1995, and drying the solid portion, which preferably has a mass of 1 g or less. Furthermore, it is even more preferable that the mass of the organic binder when the test substance is added to 1 L of water at 60°C, stirred at 500 rpm for 30 minutes, cooled to 20°C after stirring is complete, and the liquid portion is removed by suction filtration using filter paper type 5C specified in JIS P3801:1995, and the solid portion is dried has a mass of 1 g or less.

The organic binder content in the partition wall 112 (and the outer peripheral wall 102, if necessary) is not particularly limited, but from the viewpoint of water resistance, it is preferably 2 to 20% by mass, more preferably 3 to 18% by mass, and even more preferably 5 to 15% by mass.

The partition walls 112 (and the outer peripheral wall 102 as required) constituting the honeycomb structure 100 may further contain an inorganic binder in addition to the above components.
The inorganic binder is not particularly limited, and any known binder can be used. By using an inorganic binder, the water resistance of the honeycomb structure 100 can be improved and cracks during drying can be suppressed. In particular, since inorganic binders are generally water-insoluble, a decrease in water resistance can be suppressed.
Here, 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.

Specific examples of inorganic binders include clay, diatomaceous earth, layered clay minerals, montmorillonite, hydrotalcite, activated clay, acid clay, hectorite, halloysite, attapulgite, silica, silica gel, alumina, talc, chlorite, vermiculite, mica, illite, pyrophyllite, sericite, kaolin, sepiolite, boehmite, palygorskite, and bentonite. These can be used alone or in combination of two or more.

In addition to the above components, the partition walls 112 (and the peripheral wall 102, if necessary) that make up the honeycomb structure 100 may further contain known additives such as surfactants and pore-forming materials, as long as they do not impair the effects of the present invention.

Specific examples of the surfactant include ethylene glycol, dextrin, fatty acid soap, polyalcohol, etc. These may be used alone or in combination of two or more.
Specific examples of the pore-forming material include wood flour, activated carbon, hollow resin, porous resin, hollow inorganic material, porous inorganic material, etc. These may be used alone or in combination of two or more.

The average thickness of the partition walls 112 (and the peripheral wall 102, if necessary) constituting the honeycomb structure 100 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 112 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 112 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 112 is defined as the length of the portion of the line segment connecting the centers of gravity of adjacent cells 108 that passes through the partition wall 112 in a cross section perpendicular to the extension direction of the cells 108. Furthermore, the average thickness of the partition walls 112 refers to the average value of the thicknesses of all the partition walls 112 in the honeycomb structure 100.

The cell density (number of cells per unit cross-sectional area) of the honeycomb structure 100 is not particularly limited, but from the viewpoint of improving the contact area between the carbon dioxide adsorbent contained in the partition walls 112 and the gas being vented, it is preferably 30 cells/ ^inch2 (4.65 cells/ ^cm2 ) or more, more preferably 40 cells/ ^inch2 (6.20 cells/ ^cm2 ) or more, and even more preferably 50 cells/ ^inch2 (7.75 cells/ ^cm2 ) or more. Furthermore, from the viewpoint of ensuring a gas flow path and reducing pressure loss, the cell density is preferably 2000 cells/ ^inch2 (310.00 cells/ ^cm2 ) or less, more preferably 1200 cells/ ^inch2 (186.00 cells/ ^cm2 ) or less, and even more preferably 900 cells/ ^inch2 (139.50 cells/ ^cm2 ) or less. Therefore, the cell density is preferably, for example, 30 to 2000 cells/inch ² (4.65 to 310.00 cells/cm ² ), more preferably 40 to 1200 cells/inch ² (6.20 to 186.00 cells/cm ² ), and even more preferably 50 to 900 cells/inch ² (7.75 to 139.50 cells/cm ² ). In this specification, the cell density is calculated by dividing the number of cells 108 in the honeycomb structure 100 by the area of one end face of the honeycomb structure 100 excluding the outer wall 102.

There are no restrictions on the shape of the cells 108 in a cross section perpendicular to the extension direction of the cells 108 (the height direction of the honeycomb structure 100), but a square, hexagon, octagon, circle, or a combination of these is preferred. Of these, the shape of the cells 108 is preferably a square or hexagon. By shaping the cells 108 in this way, pressure loss when a fluid is passed through the honeycomb structure 100 is reduced.

The honeycomb structure 100 may further have a water-resistant layer on the surface of the partition wall 112 (and the outer peripheral wall 102 as necessary). By providing the water-resistant layer, the water resistance of the honeycomb structure 100 can be further improved.
The water-resistant layer is not particularly limited, but preferably contains a water-resistance imparting agent. The same water-resistance imparting agents as those described above can be used. Among them, silicones are preferred as the water-resistance imparting agent. Silicones have high _CO2 permeability, so even if the surface of the partition wall 112 (and the outer peripheral wall 102, if necessary) is covered with silicones, the _CO2 adsorption performance can be maintained.

The honeycomb structure 100 preferably has a carbon dioxide (CO ₂ ) adsorption amount of 0.5 mol/kg or more, more preferably 0.8 mol/kg or more. Such a CO ₂ adsorption amount can be said to have good CO ₂ adsorption performance.
The _CO2 adsorption capacity can be measured, for example, as follows. First, a cubic sample measuring 20 mm x 20 mm x 40 mm (length in the extension direction of the cells 108) is cut from near the center of the honeycomb structure 100. Next, this sample is placed in a sealed container, and _CO2 concentration sensors are installed on the inlet and outlet sides of the sample's cells 108. Next, as a pretreatment, nitrogen gas heated to 90-100°C is passed through the sample at a flow rate of 1.5 L/min until the _CO2 concentration on the outlet side reaches 0 ppm. Then, heating is stopped while the nitrogen gas continues to flow until the sample reaches 25°C (room temperature). After reaching 25°C, 25°C air is passed through the sample at a flow rate of 15 L/min, and the _CO2 adsorption capacity (mol) until saturation is measured. The measured _CO2 adsorption capacity (mol) can be divided by the mass (kg) of the sample to calculate the _CO2 adsorption capacity per mass of the sample (mol/kg).

When the following residual _CO2 ratio, which is an index of the carbon dioxide ( _CO2 ) adsorption rate, is measured, the honeycomb structure 100 is preferably less than 50%, more preferably less than 40%. Such a residual _CO2 ratio can be said to have good _CO2 adsorption performance.
The residual _CO2 ratio can be measured, for example, as follows. First, a cubic sample equivalent to 1.0 g is cut out from near the center of the honeycomb structure 100. Next, as a pretreatment, the sample is heated at 80°C for 10 minutes to desorb _CO2 . Next, the sample is left in a 4 L sealed container for 100 seconds to absorb _CO2 from the atmosphere. A _CO2 concentration sensor is installed in the sealed container, and the residual _CO2 ratio is calculated from the _CO2 concentration in the sealed container before and after leaving the sample in the sealed container according to the following formula.
_CO2 remaining ratio (%) = _CO2 concentration after leaving sample / _CO2 concentration before leaving sample × 100

The honeycomb structure 100 is preferably such that a cubic sample having a side length of 20 mm is cut out from the bone-dry honeycomb structure 100, and the sample is immersed in water for 24 hours, and then the B-axis compressive strength (compressive strength in a direction perpendicular to the extension direction of the cells 108) is 0.05 MPa or more. A B-axis compressive strength in this range can be said to have good water resistance.
The B-axis compressive strength can be measured by placing a weight on the side surface of the honeycomb structure 100, applying a compressive load of 0.05 MPa to the honeycomb structure, and visually evaluating the degree of deformation. If there is no or only a small amount of deformation in this evaluation, it can be said that the honeycomb structure can withstand a load of 0.05 MPa.

(2. _CO2 capture and desorption methods)
According to an embodiment of the present invention, a method for capturing and desorbing CO ₂ using a honeycomb structure 100 is provided.
Specifically, a _CO2 recovery method according to an embodiment of the present invention includes flowing a gas to be treated ( _CO2 -containing gas) containing _CO2 through multiple cell channels of a honeycomb structure 100, adsorbing the _CO2 in the gas to be treated by a carbon dioxide adsorbent while the gas to be treated passes through the multiple cell channels, and discharging the gas to be treated with a reduced _CO2 concentration from the honeycomb structure 100.
The gas to be treated is not particularly limited as long as it contains _CO2 , but examples include environmental air (outdoor air as well as indoor or indoor air), factory exhaust gas, ship exhaust gas, and power plant exhaust gas.

In addition, a _CO2 desorption method according to an embodiment of the present invention includes flowing a desorbed gas or a heated desorbed gas through a plurality of cell channels of a honeycomb structure 100 in which _CO2 is adsorbed, and desorbing _CO2 from the carbon dioxide adsorbent into the desorbed gas while the desorbed gas passes through the plurality of cell channels.
The desorbed gas is not particularly limited as long as it is a gas capable of desorbing _CO2 , and for example, water vapor can be used. The water vapor is preferably at a high temperature of 80°C or higher. The desorbed gas may be heated by a heater or by mixing with a high-temperature gas.

(3. Manufacturing method of honeycomb structure)
A preferred example of a method for manufacturing a honeycomb structure according to an embodiment of the present invention will be described below.
A method for manufacturing a honeycomb structure according to an embodiment of the present invention includes a step A of kneading a forming raw material containing a solvent, a carbon dioxide adsorbent, a water resistance agent, and an organic binder to prepare a clay, a step B of forming the clay into a honeycomb formed body (the honeycomb formed body has a plurality of cell channels that pass through the interior and are separated by partition walls), and a step C of drying the honeycomb formed body.

(Process A)
In step A, a molding raw material containing a solvent, a carbon dioxide adsorbent, a water resistance imparting agent, and an organic 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.

From the viewpoint of achieving a good balance between CO ₂ adsorption performance, crack suppression during drying, and water resistance, the content of carbon dioxide adsorbent excluding the solvent in the forming raw material is 40 to 94% by mass, the content of water resistance imparting agent excluding the solvent in the forming raw material is 2 to 20% by mass, and the content of organic binder excluding the solvent in the forming raw material is preferably 2 to 20% by mass. Also, the content of carbon dioxide adsorbent excluding the solvent in the forming raw material is 50 to 90% by mass, the content of water resistance imparting agent excluding the solvent in the forming raw material is 3 to 18% by mass, and the content of organic binder excluding the solvent in the forming raw material is more preferably 3 to 18% by mass. Furthermore, the content of carbon dioxide adsorbent excluding the solvent in the forming raw material is 60 to 85% by mass, the content of water resistance imparting agent excluding the solvent in the forming raw material is 5 to 15% by mass, and the content of organic binder excluding the solvent in the forming raw material is even more preferably 5 to 15% by mass.

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 the value (mm) at this time 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.

The preferred properties, types, and compounding ratios of the carbon dioxide adsorbent have already been described, but the following supplementary information is provided. The carbon dioxide adsorbent used as a molding raw material is preferably porous. Furthermore, the median diameter (D50) of the carbon dioxide adsorbent, based on the volume-based cumulative particle size distribution obtained by laser diffraction/scattering, 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 carbon dioxide adsorbent is preferably 0.1 μm or more, more preferably 0.5 μm or more, and even more preferably 1 μm or more, for reasons of ease of availability and suppression of secondary aggregation. Therefore, the median diameter (D50) of the carbon dioxide adsorbent 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.

The preferred properties, types, and blending ratios of water-resistant agents have already been described, but water-resistant agents can be blended in various forms, including emulsions in water or polar solvents, organic solvent-diluted types such as lacquers, solvent-free types, and solid particle solvent dispersion types. Therefore, there are no particular restrictions on shape or size.

The preferred properties, types, and blending ratios of organic binders have already been described. Water-soluble organic binders dissolve during kneading. Therefore, there are no particular restrictions on shape or size, and it is sufficient to use organic binders in a commonly available form. When using water-insoluble organic binders, they will dissolve during kneading if an organic solvent is used. Therefore, there are no particular restrictions on shape or size, and it is sufficient to use organic binders in a commonly available form.

The molding raw material may further contain an inorganic binder.
The content of the inorganic binder excluding the solvent in the forming raw material is preferably 3 to 50 mass %, more preferably 4 to 40 mass %, and even more preferably 5 to 35 mass %, from the viewpoints of water resistance and suppression of cracking during drying.

The preferred properties, types, and compounding ratios of inorganic binders have already been discussed, but we will add a few more details below. It is preferable that the inorganic binder used as a molding material be porous.

The molding raw materials containing the above components can be kneaded using a known kneading machine, but it is desirable to knead them for the time required for each component to be uniformly distributed throughout the clay.

(Process B)
In step B, a honeycomb formed body having a plurality of cell channels that pass through the interior of the honeycomb formed body and are partitioned by partition walls is formed from the clay.
Typically, in step B, a honeycomb formed body having an outer peripheral wall and partition walls disposed on the inner peripheral side of the outer peripheral wall, extending from the first end face to the second end face, and defining 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.

(Process C)
In step C, the honeycomb formed body is dried.
Since the honeycomb formed body immediately after forming contains a solvent, the solvent is removed by drying. For drying, 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, dielectric drying, or a combination thereof is preferred, as it allows the entire honeycomb formed body to be dried quickly and uniformly. From the viewpoint of suppressing decomposition of the carbon dioxide adsorbent, water resistance imparting agent, and organic binder during drying, it is preferable to dry the honeycomb formed body in an air atmosphere at 20 to 150°C, more preferably in an air atmosphere at 30 to 140°C, and even more preferably in an air atmosphere at 40 to 130°C.

The method for manufacturing a honeycomb structure according to an embodiment of the present invention may further include a step of forming a water-resistant layer on the surface of the partition wall. This step may be performed before or after the step C.
The method for forming the water-resistant layer is not particularly limited, and may be, for example, by applying a slurry containing a water-resistance imparting agent and a solvent to the partition walls. For example, the water-resistant layer can be formed on the surface of the partition walls by immersing the honeycomb formed body (or honeycomb structure) in the slurry and drying it.

(4. Carbon dioxide capture device)
A carbon dioxide capture device according to an embodiment of the present invention includes one or more of the above-described honeycomb structures 100. Because the honeycomb structures 100 have good water resistance, this carbon dioxide capture device can suppress outflow and deterioration of the carbon dioxide adsorbent when carbon dioxide (hereinafter also referred to as " _CO2 ") is desorbed from the carbon dioxide adsorbent that has adsorbed carbon dioxide using a desorption gas such as water vapor.

The carbon dioxide capture device according to the embodiment of the present invention may further include a housing that accommodates the honeycomb structure 100. The housing is preferably connected to pipes that can supply and discharge the _CO2 -containing gas to be treated and the desorbed gas. A carbon dioxide capture device having such a structure can easily achieve the capture and desorption of _CO2 .

The present invention will be explained in detail below using examples, but the present invention should not be construed as being limited to these examples.

(1. Raw materials)
The following commercially available water-insoluble weakly basic anion exchange resin (a styrene-based divinylbenzene polymer having a primary amine functional group with an exchange capacity of 2.0 meq/mL) was prepared as a carbon dioxide ( _CO2 ) adsorbent. This ion exchange resin was porous and granular. Furthermore, the median diameter (D50) of the volume-based cumulative particle size distribution measured by laser diffraction/scattering was 10 μm.

Commercially available silicones (silicone rubber) were used as water resistance agents.

Commercially available methyl cellulose was prepared as the organic binder. 31 g of this methyl cellulose was added to 1 L of 60°C water and stirred at 500 rpm for 30 minutes. After stirring was complete, the mixture was cooled to 20°C 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 when dried was 1 g or less.

The following commercially available inorganic binders were used:
Inorganic binder A: diatomaceous earth Inorganic binder B: sepiolite

Industrial water was used as the solvent.

(2. Manufacturing of honeycomb structure)
A molding raw material was obtained by blending the components and solvent shown in Table 1. The contents of the carbon dioxide adsorbent, water resistance imparting agent, organic binder, and inorganic binder in Table 1 refer to the contents when the total of these is taken as 100% by mass (i.e., when the total of the components excluding the solvent is taken as 100% by mass). The amount of solvent blended was adjusted so that the clay hardness measured with an NGK hardness tester (model number: NGK-01) manufactured by NGK Insulators, Ltd. was 17 mm. Next, the molding raw material was kneaded for 30 minutes in a vacuum kneader to prepare a cylindrical clay.

Next, the obtained cylindrical clay was molded using an extrusion molding machine with a predetermined die structure to obtain a cylindrical honeycomb molded body in which each cell shape in a cross section perpendicular to the cell extension direction was square. The honeycomb structure during extrusion molding was visually measured to evaluate the moldability of the honeycomb molded body. The moldability was evaluated according to the following criteria. The results are shown in the "Moldability" column of Table 2.
◯: No cracks in the partition walls and a honeycomb structure was formed. △: Cracks were observed in the partition walls, but a honeycomb structure was formed. ×: Shape retention was insufficient and the honeycomb structure could not be maintained.

Next, the obtained honeycomb molded body was dried by high-frequency dielectric heating, and then dried for 2 minutes in an atmospheric atmosphere at 100°C using a microwave dryer. Both end faces were then cut off by a predetermined amount to produce a honeycomb structure. The honeycomb structure obtained by the above manufacturing method had circular end faces with a diameter of 60 mm and a height (length in the cell extension direction) of 120 mm. The cell density was 300 cells/ ^inch2 (46.50 cells/ ^cm2 ), and the average thickness of the partition walls was 200 μm. The honeycomb structures were produced in the number required for various tests, and the following evaluations were performed.

(3. Evaluation of honeycomb structures)

<B-axis compressive strength>
A cubic sample having a side length of 20 mm was cut out from the honeycomb structure, and the B-axis compressive strength was evaluated according to the above-mentioned method. The evaluation was performed according to the following criteria. The results are shown in the "B-axis compressive strength" column in Table 2.
○: No or little deformation (can withstand a load of 0.05 MPa)
×: Large deformation (cannot withstand a load of 0.05 MPa, and the honeycomb structure cannot be maintained)

< _CO2 adsorption amount>
A cubic sample measuring 20 mm x 20 mm x 40 mm (length in the extension direction of the cells 108) was cut from near the center of the honeycomb structure, and the _CO2 adsorption amount (mol) until saturation was reached was measured according to the method described above, and the _CO2 adsorption amount (mol/kg) per mass (kg) of the sample was calculated. This evaluation was performed according to the following criteria. The results are shown in the " _CO2 adsorption amount" column of Table 2.
◎: Adsorption amount is 0.8 mol/kg or more. ○: Adsorption amount is 0.5 mol/kg or more and less than 0.8 mol/kg. △: Adsorption amount is 0.1 mol/kg or more and less than 0.5 mol/kg. ×: Adsorption amount is less than 0.1 mol/kg.

< _CO2 adsorption rate (remaining _CO2 ratio)>
A cubic sample equivalent to 1.0 g was cut out from near the center of the honeycomb structure, and the residual _CO2 ratio was determined according to the method described above. This evaluation was performed according to the following criteria. The results are shown in the " _CO2 adsorption rate" column in Table 2.
◎: The remaining percentage of _CO2 is less than 40%. ○: The remaining percentage of _CO2 is 40% or more and less than 50%. △: The remaining percentage of _CO2 is 50% or more and less than 60%. ×: The remaining percentage of _CO2 is 60% or more.

<Component analysis>
The honeycomb structure was crushed in an agate mortar, and the crushed material was measured using a Fourier transform infrared spectrophotometer to obtain an FT-IR spectrum.
In addition, in the FT-IR spectrum, a peak (near 1250 to 1270 cm ⁻¹ ) due to Si—C bending was confirmed and represented as ◯ (silicones were included), and if no peak was confirmed, represented as × (silicones were not included).

As shown in Table 2, the honeycomb structures of Examples 1 to 3, which contained a carbon dioxide adsorbent, a water resistance imparting agent, and an organic binder, showed little deformation even when a load was applied and had excellent water resistance. In addition, other evaluation results showed that the results of moldability, _CO2 adsorption performance, and _CO2 adsorption rate were also good.
In contrast, the honeycomb structures of Comparative Examples 1 and 2, which did not contain a water-resistance imparting agent, were significantly deformed when a load was applied, and had insufficient water resistance.

As can be seen from the above results, the present invention can provide a honeycomb structure with excellent water resistance, a method for manufacturing the same, and a carbon dioxide recovery device.

1: Hardness meter 2: Spring material 3: Support portion 4: Tip portion 5: Sheath portion 6, 7: Clay a1, a2: Protruding length 100: Honeycomb structure 102: Peripheral wall 104: First end face 106: Second end face 108: Cell 112: Partition wall

Claims (21)

A honeycomb structure,
a plurality of cell channels passing through the honeycomb structure and separated by partition walls;
The honeycomb structure, wherein the partition walls contain a carbon dioxide adsorbent, a water resistance imparting agent, and an organic binder. The honeycomb structure according to claim 1, wherein the partition walls further contain an inorganic binder. The honeycomb structure according to claim 1 or 2, wherein the water-resistance imparting agent is one or more selected from silicones, partially benzalized polyvinyl alcohol, (meth)acrylic resin, polyacrylate resin, polynitrile resin, polychloroprene, polyvinyl chloride, polyvinylidene fluoride, polyolefins, poly(tetrafluoroethylene), polyurethanes, phenols, urethanes, polyvinyl butyral, ethylene-vinyl acetates, and synthetic rubbers. The honeycomb structure according to claim 1 or 2, wherein the partition walls have a peak attributable to Si-C bending angles when measured by FT-IR (Fourier transform infrared spectroscopy). The honeycomb structure according to claim 1 or 2, wherein the carbon dioxide adsorbent is dispersed in the partition walls. The honeycomb structure according to claim 1 or 2, wherein the organic binder is one or more selected from methyl cellulose, hydroxypropyl methyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, carboxymethyl cellulose, polyvinyl alcohol, hydroxyethyl methyl cellulose, polyethylene oxide, polybutadiene, acrylic acid esters, methacrylic acid esters, and ethyl cellulose. The honeycomb structure according to claim 1 or 2, having a water-resistant layer on the surface of the partition walls. The honeycomb structure according to claim 7, wherein the water-resistant layer contains one or more materials selected from silicones, partially benzalized polyvinyl alcohol, (meth)acrylic resin, polyacrylate resin, polynitrile resin, polychloroprene, polyvinyl chloride, polyvinylidene fluoride, polyolefins, poly(tetrafluoroethylene), polyurethanes, phenols, urethanes, polyvinyl butyral, ethylene-vinyl acetates, and synthetic rubbers. The honeycomb structure according to claim 1 or 2, having a carbon dioxide adsorption capacity of 0.5 mol/kg or more. The honeycomb structure according to claim 1 or 2, wherein the carbon dioxide adsorbent is a solid organic compound having an amino group. The honeycomb structure according to claim 10, wherein the solid organic compound is a weakly basic anion exchange resin having an amino group. The honeycomb structure according to claim 10, wherein the solid organic compound contains at least one selected from a styrene-divinylbenzene copolymer having an amino group and a (meth)acrylic acid-divinylbenzene copolymer having an amino group. a step of kneading a molding raw material including a solvent, a carbon dioxide adsorbent, a water resistance imparting agent, and an organic binder to prepare a clay;
a step of forming the clay into a honeycomb formed body, the honeycomb formed body having a plurality of cell channels passing through the interior and separated by partition walls;
and drying the honeycomb formed body. The method for manufacturing a honeycomb structure according to claim 13, wherein the forming raw material further contains an inorganic binder. The method for manufacturing a honeycomb structure according to claim 13 or 14, wherein the water-resistance imparting agent is one or more selected from silicones, partially benzalized polyvinyl alcohol, (meth)acrylic resin, polyacrylate resin, polynitrile resin, polychloroprene, polyvinyl chloride, polyvinylidene fluoride, polyolefins, poly(tetrafluoroethylene), polyurethanes, phenols, urethanes, polyvinyl butyral, ethylene-vinyl acetates, and synthetic rubbers. The method for manufacturing a honeycomb structure according to claim 13 or 14, wherein the organic binder is one or more selected from the group consisting of methyl cellulose, hydroxypropyl methyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, carboxymethyl cellulose, polyvinyl alcohol, hydroxyethyl methyl cellulose, polyethylene oxide, polybutadiene, acrylic acid esters, methacrylic acid esters, and ethyl cellulose. The method for manufacturing a honeycomb structure according to claim 13 or 14, further comprising a step of forming a water-resistant layer on the surface of the partition walls. The method for manufacturing a honeycomb structure according to claim 13 or 14, wherein the carbon dioxide adsorbent is a solid organic compound having an amino group. The method for manufacturing a honeycomb structure according to claim 18, wherein the solid organic compound is a weakly basic anion exchange resin having an amino group. The method for manufacturing a honeycomb structure according to claim 18, wherein the solid organic compound contains at least one selected from a styrene-divinylbenzene copolymer having an amino group and a (meth)acrylic acid-divinylbenzene copolymer having an amino group. A carbon dioxide recovery device comprising one or more of the honeycomb structures described in claim 1 or 2.