Honeycomb structure and gas recovery device

Abstract

This honeycomb structure includes: an outer peripheral wall 11; partition walls 15 disposed inside the outer peripheral wall 11 and partitioning and forming a plurality of cells 14 extending from an inflow end face 12 to an outflow end face 13; and coat layers 16 formed at least on the surfaces of the partition walls 15 and containing adsorbents capable of adsorbing and desorbing greenhouse gas. In the honeycomb structure, at least some of the partition walls 15 have a bent structure in a cross section parallel to the direction in which the cells 14 extend, and the degree of bending of the partition walls 15 having the bent structure is 1.01-1.09.

Description

Honeycomb Structure and Gas Recovery Device

[0001] The present invention relates to a honeycomb structure and a gas recovery device.

[0002] In order to realize a carbon-neutral society, there is increasing demand for technologies that recover and utilize greenhouse gases (e.g., carbon dioxide) from the atmosphere and exhaust gas. As a typical conventional carbon dioxide (CO₂) recovery technology, direct air capture (DAC), which is a technology for adsorbing CO₂ from the atmosphere, is known. There are several types of DAC technologies, such as liquid absorption, membrane separation and solid adsorption. Among them, in the solid adsorption method, it is common to support an adsorbent such as a CO₂ adsorbent (absorbent) on a base material. For example, Patent Document 1 proposes a honeycomb structure in which a CO₂ adsorbent is supported in or on the surface of cell walls (partition walls). This honeycomb structure can adsorb CO₂ by causing a processing gas containing CO₂ to flow through the cells. Furthermore, CO₂ adsorbed in the honeycomb structure can be desorbed by causing a purge gas (desorption gas) such as water vapor to flow through the cells. Accordingly, the honeycomb structure can repeatedly perform adsorption and desorption of CO₂.

[0003] Japanese National Publication of International Patent Application No. 2013-540573

[0004] CO₂ adsorbed in the honeycomb structure is desorbed by causing a purge gas such as water vapor to flow through the cells as described above, but at this time the adsorbent absorbs water and expands. Therefore, in a honeycomb structure having a coating layer containing the adsorbent formed on the surface of the partition walls (base material), repeated adsorption and desorption of CO₂ easily causes the coating layer to peel off due to the expansion and contraction of the adsorbent, and the coating layer may fall off from the honeycomb structure due to the flow of the processing gas containing CO₂. Note that, although the case where the greenhouse gas is CO₂ has been described as an example above, a similar phenomenon may occur when adsorbing other greenhouse gases.

[0005] The present invention has been made to solve the problems described above, and an object of the present invention is to provide a honeycomb structure and a gas recovery device in which the coating layer containing the adsorbent is less prone to falling off.

[0006] The inventors of the present invention have diligently researched honeycomb structures having a coating layer on the surface of the partition walls that contains an adsorbent capable of adsorbing and desorbing greenhouse gases. As a result, they have found that the above problems can be solved by configuring at least some of the partition walls to have a bent structure with a predetermined degree of curvature, and have completed the present invention. That is, the present invention is illustrated as follows.

[0007] <1> A honeycomb structure comprising an outer perimeter wall, partition walls disposed inside the outer perimeter wall and forming a plurality of cells extending from an inlet end face to an outlet end face, and a coating layer formed on at least the surface of the partition walls and containing an adsorbent capable of adsorbing and desorbing greenhouse gases, wherein at least a portion of the partition walls has a bent structure in a cross section parallel to the direction in which the cells extend, and the degree of curvature of the partition walls having the bent structure is 1.01 to 1.09.

[0008] <2> The honeycomb structure according to <1>, wherein in a cross section parallel to the direction in which the cells extend, the degree of curvature of the cells partitioned by the partition wall having the bending structure is 1.01 to 1.04.

[0009] <3> The honeycomb structure according to <1> or <2>, wherein, in a cross section parallel to the direction in which the cell extends, the bending structure of the two partition walls facing one of the cells is symmetrical with respect to the axial center of the cell.

[0010] <4> The bending structure of the partition wall is a honeycomb structure according to any one of <1> to <3>, wherein the period is 4.5 to 5.5 mm and the amplitude is 1.0 to 2.5 mm.

[0011] <5> The honeycomb structure according to any one of <1> to <4>, wherein the bending structure of the partition wall is formed in a region of the partition wall parallel to the direction in which the cells extend, excluding a region from each end face to 10% of the total length.

[0012] <6> The honeycomb structure according to any one of <1> to <5>, wherein the bending structure of the partition wall is formed in the partition wall that partitions at least the central cell in a cross section perpendicular to the direction in which the cell extends.

[0013] <7> The bending structure of the partition wall is a honeycomb structure according to any one of <1> to <6>, which is formed on all of the partition walls.

[0014] <8> The honeycomb structure according to any one of <1> to <7>, wherein the adsorbent is an amine compound.

[0015] <9> The honeycomb structure according to <8>, wherein the amine compound is a weakly basic anion exchange resin having an amino group.

[0016] <10> The honeycomb structure according to <8>, wherein the amine compound contains one or more selected from styrene copolymers having amino groups and acrylic copolymers having amino groups.

[0017] <11> The honeycomb structure according to any one of <1> to <10>, wherein the greenhouse gas is carbon dioxide.

[0018] <12> A gas recovery device comprising a honeycomb structure as described in any one of <1> to <11>.

[0019] According to the present invention, it is possible to provide a honeycomb structure and a gas recovery device in which the coating layer containing the adsorbent is less likely to fall off.

[0020] This is a schematic diagram of a cross-section perpendicular to the direction in which the cells of a honeycomb structure according to an embodiment of the present invention extend. This is a schematic diagram of the cross-section of the honeycomb structure of Figure 1A along the line a-a'. This is an enlarged view of region R1 in Figure 1B. This is a schematic diagram for explaining how to determine the degree of curvature of the partition wall.

[0021] The honeycomb structure of the present invention comprises an outer perimeter wall, partition walls disposed inside the outer perimeter wall and forming partitions for a plurality of cells extending from the inlet end face to the outlet end face, and a coating layer formed on at least the surface of the partition walls and containing an adsorbent (hereinafter abbreviated as "adsorbent") capable of adsorbing and desorbing greenhouse gases. Furthermore, in a cross-section parallel to the direction in which the cells extend, at least a portion of the partition walls has a bent structure, and the degree of curvature of the partition walls having a bent structure is 1.01 to 1.09. By having such a structure, even if the adsorbent expands and contracts due to repeated adsorption and desorption of greenhouse gases and a portion of the coating layer peels off, the bent structure of the partition walls makes it difficult for the coating layer to fall off the honeycomb structure.

[0022] The embodiments of the present invention will be described in detail below with reference to the drawings. The present invention is not limited to the following embodiments, and it should be understood that modifications, improvements, etc., to the following embodiments, based on the ordinary knowledge of those skilled in the art, without departing from the spirit of the invention, also fall within the scope of the present invention.

[0023] (1. Honeycomb Structure) Figure 1A is a schematic diagram of a cross-section perpendicular to the direction in which the cells of a honeycomb structure according to an embodiment of the present invention extend. Figure 1B is a schematic diagram of a cross-section of the honeycomb structure of Figure 1A along line a-a' (a cross-section parallel to the direction in which the cells extend). Figure 1C is an enlarged view of region R1 in Figure 1B. The honeycomb structure according to an embodiment of the present invention comprises an outer peripheral wall 11, partition walls 15 disposed inside the outer peripheral wall 11 and forming partitions for a plurality of cells 14 extending from an inlet end face 12 to an outlet end face 13, and a coating layer 16 formed on at least the surface of the partition walls 15 and containing an adsorbent capable of adsorbing and desorbing greenhouse gases. With such a structure, greenhouse gases can be adsorbed and desorbed by the coating layer 16.

[0024] As shown in the enlarged view of Figure 1C, the honeycomb structure according to the embodiment of the present invention has a bent structure in which at least a portion of the partition walls 15 are bent in a cross section parallel to the direction in which the cells 14 extend. By having a bent structure in which at least a portion of the partition walls 15 are bent, even if a portion of the coating layer 16 peels off due to the expansion and contraction of the adsorbent, it is possible to suppress the detachment of the coating layer 16 from the honeycomb structure. Here, in this specification, "bent structure" means a structure having a bend. Examples of bent structures are not particularly limited, but for example, a wavy structure as shown in Figure 1C.

[0025] The degree of curvature of the partition wall 15 having a bent structure is 1.01 to 1.09, preferably 1.02 to 1.08, and more preferably 1.03 to 1.07. By controlling the degree of curvature of the partition wall 15 within this range, even if a part of the coating layer 16 peels off due to the expansion and contraction of the adsorbent, it is possible to suppress the detachment of the coating layer 16 from the honeycomb structure. Here, in this specification, "degree of curvature of the partition wall 15" is an index indicating the degree of curvature of the partition wall 15.

[0026] The degree of curvature of the partition wall 15 can be determined by the following method. A measurement sample cut from a part of the honeycomb structure is used, and structural analysis is performed by X-ray CT (Computed Tomography). The measurement sample is, for example, sized to include two cells 14 in both the vertical and horizontal directions in a cross section perpendicular to the direction in which the cells 14 of the honeycomb structure extend. Structural analysis by X-ray CT can be performed using a commercially available X-ray CT system, by capturing projection data by X-ray irradiation. The various conditions for X-ray CT are not particularly limited as long as they allow the internal structure of the measurement sample (honeycomb structure) to be identified. Next, an image of a cross section parallel to the direction in which the cells 14 extend is obtained from the projection data obtained by X-ray CT, and then image processing (e.g., binarization) is performed to separate the partition wall 15, the coating layer 16, and the space (cells 14). Next, as shown in Figure 2, a straight line L1 is drawn perpendicular to the direction in which the cells 14 extend at a pitch of 60 μm on the partition wall 15 separated by image processing. The midpoint P1 of the straight line L1 within the partition wall 15 is connected by a straight line L2, and the total length of the straight line L2 is calculated. Then, the calculated length of the straight line L2 is divided by the total length L3 of the measurement sample in the direction in which the cell 14 extends, and this value is taken as the degree of curvature of the partition wall 15.

[0027] In the honeycomb structure according to the embodiment of the present invention, it is preferable that the degree of curvature of the cells 14, which are partitioned by partition walls 15 having a bent structure, is 1.01 to 1.04. By controlling the degree of curvature of the cells 14 within this range, it is possible to stably suppress the detachment of the coating layer 16 from the honeycomb structure while suppressing an increase in pressure loss. Here, the degree of curvature of the cells 14 can be determined in the same manner as the degree of curvature of the partition walls 15 described above. That is, for the cells 14 separated by the image processing described above, the total length of the straight line L2 is calculated in the same manner as above, and the value obtained by dividing the calculated length of the straight line L2 by the total length L3 of the measurement sample in the direction in which the cells 14 extend is taken as the degree of curvature of the cells 14.

[0028] In the honeycomb structure according to the embodiment of the present invention, as shown in Figure 1C, it is preferable that the bending structure of the two partition walls 15 facing one cell 14 is symmetrical with respect to the axial center P2 of the cell 14 in a cross section parallel to the direction in which the cell 14 extends. By adopting such a structure, it becomes easier to control the degree of bending of the cell 14 within the above range, thereby stably suppressing the detachment of the coating layer 16 from the honeycomb structure while suppressing an increase in pressure loss.

[0029] The bending structure of the partition wall 15 is not particularly limited as long as the degree of bending of the partition wall 15 satisfies the above range, but it is preferable that the period W1 is 4.5 to 5.5 mm and the amplitude W2 is 1.0 to 2.5 mm. By controlling the period W1 and amplitude W2 in this way, the shedding of the coating layer 16 from the honeycomb structure can be stably suppressed. Here, in this specification, "period W1 of the bending structure of the partition wall 15" means the length between the convex portions (or between the concave portions) of the bending structure of the partition wall 15, as shown in Figure 1C. Also, "amplitude W2 of the bending structure of the partition wall 15" means the height of the convex portion (or depth of the concave portion).

[0030] The bent structure of the partition wall 15 is preferably formed in region R3, which is excluding region R2, which is 10% of the total length from each end face (inlet end face 12 and outlet end face 13) of the partition wall 15 that is parallel to the direction in which the cell 14 extends (see Figure 1B). By providing the bent structure of the partition wall 15 in region R3, the shedding of the coating layer 16 from the honeycomb structure can be stably suppressed.

[0031] The bending structure of the partition wall 15 is preferably formed on the partition wall 15 that partitions at least the central cells 14 in a cross section perpendicular to the direction in which the cells 14 extend. In the central cells 14, the flow rate of processing gas and purge gas increases, which tends to cause the coating layer 16 to easily fall off the honeycomb structure. However, this problem can be solved by providing a bending structure on the partition wall 15 that partitions the central cells 14. Here, in this specification, "central cells 14" means the cells 14 located at the center C1 of the honeycomb structure in a cross section perpendicular to the direction in which the cells 14 extend, or, if the partition wall 15 is located at the center C1 of the honeycomb structure, the cells 14 closest to the center C1 (see Figure 1A).

[0032] It is preferable that the bent structure of the partition wall 15 is formed on all partition walls 15. By providing a bent structure on all partition walls 15, it is possible to stably suppress the detachment of the coating layer 16 from the honeycomb structure even in various cases where the flow rate of the processing gas and purge gas differs depending on the position of the honeycomb structure.

[0033] The shape of the honeycomb structure according to the embodiment of the present invention is not particularly limited. For example, the outer shape of the cross-section perpendicular to the direction in which the cells 14 of the honeycomb structure extend can be a polygon such as a triangle, square, hexagon, or octagon, or a round shape such as a circle, ellipse, oval, egg, oblong, or rounded square (a square composed of curves overall, where each side and each corner is composed of curves, and the radius of curvature of each side is greater than the radius of curvature of each corner). Among these, from the viewpoint of manufacturability, it is preferable that the outer shape of the cross-section and end faces (inlet end face 12 and outlet end face 13) of the honeycomb structure is square (i.e., the shape of the honeycomb structure is a rectangular prism).

[0034] The honeycomb structure according to the embodiment of the present invention preferably has a rectangular prism shape in which the length of one side of the inlet end face 12 and the outlet end face 13 is 100 to 500 mm (preferably 200 to 400 mm), and the length in the direction in which the cell 14 extends is 100 to 1000 mm (preferably 300 to 500 mm). With a honeycomb structure of such size, a sufficient amount of adsorbent can be secured in the cell 14, and thus its practicality can be ensured when used in a gas recovery device.

[0035] The shape of the cell 14 is not particularly limited, but in a cross-section perpendicular to the direction in which the cell 14 of the honeycomb structure extends, it can be a polygon such as a triangle, square, hexagon, or octagon, or a round shape such as a circle, ellipse, oval, egg-shaped, or oblong. The shape of the cell 14 may be single, or two or more shapes may be combined. Among these shapes of cell 14, a square or hexagon is preferred. By providing cells 14 of such shapes, the pressure loss when the processed gas flows can be reduced. The shape of the cell 14 in the cross-section is the same as the shape of the cell 14 at the end face.

[0036] The material of the honeycomb structure (outer wall 11 and partition wall 15) is not particularly limited, but from the viewpoint of ensuring the strength of the honeycomb structure, it is preferable that one or more selected from cordierite, mullite, alumina, silica, silicon carbide, and Si-bonded silicon carbide be used as the main component. Herein, in this specification, "main component" means a component that accounts for more than 50% by mass of the total components.

[0037] The thickness of the partition wall 15 is not particularly limited, but from the viewpoint of ensuring the strength of the honeycomb structure and reducing pressure loss when the processed gas passes through the cell 14, it is preferably 0.05 mm to 5 mm, more preferably 0.10 mm to 4.5 mm, and even more preferably 0.15 mm to 4 mm. In this specification, "thickness of partition wall 15" refers to the length over which a line segment connecting the centroids of adjacent cells 14 intersects the partition wall 15 in a cross section perpendicular to the direction in which the cells 14 of the honeycomb structure extend. The thickness of the partition wall 15 refers to the average value of the thicknesses of all partition walls 15.

[0038] The porosity of the partition wall 15 is not particularly limited, but from the viewpoint of ensuring the strength of the honeycomb structure and reducing pressure loss when the processed gas passes through the cell 14, it is preferably 30% or more and less than 80%, more preferably 35% to 75%, and even more preferably 40% to 70%. In this specification, "porosity of the partition wall 15" means the porosity of the partition wall 15 measured by the mercury intrusion method in accordance with JIS R1655:2003.

[0039] The average pore diameter of the partition walls 15 is not particularly limited, but from the viewpoints of securing the strength of the honeycomb structure and reducing pressure loss when a processing gas passes through the cells 14, the average pore diameter is preferably 10 µm to 300 µm, more preferably 15 µm to 280 µm, and still more preferably 20 µm to 260 µm. In this specification, the "average pore diameter of partition walls 15" means the pore diameter of partition walls 15 at an integrated value of 50% in the pore distribution obtained by mercury porosimetry in accordance with JIS R1655:2003.

[0040] The thickness of the outer peripheral wall 11 is not particularly limited, but from the viewpoint of securing the strength of the honeycomb structure, the thickness is preferably 0.05 mm to 10 mm, more preferably 0.20 mm to 8 mm, and still more preferably 0.30 mm to 6 mm. In this specification, the thickness of the outer peripheral wall 11 refers to the length in the normal direction of the outer peripheral surface from the boundary between the outer peripheral wall 11 and the outermost cells 14 or partition walls 15 to the outer peripheral surface of the honeycomb structure in a cross section orthogonal to the direction in which the cells 14 of the honeycomb structure extend.

[0041] The cell density of the honeycomb structure is not particularly limited, but from the viewpoints of securing the strength of the honeycomb structure and increasing the loading amount of a functional material, the cell density is 0.05 cells / cm 2 to 25 cells / cm 2 , preferably 0.1 cells / cm 2 to 20 cells / cm 2 , more preferably 0.5 cells / cm 2 to 15 cells / cm 2 , and even more preferably. In this specification, "cell density" is a value obtained by dividing the number of cells by the area of one end face of the honeycomb structure (the total area of the partition walls 15 and the cells 14, excluding the outer peripheral wall 11).

[0042] The coating layer 16 is formed on at least the surface of the partition wall 15 and contains an adsorbent capable of adsorbing and desorbing greenhouse gases. The coating layer 16 can also be formed on the surface of the outer peripheral wall 11 facing the cell 14. As the adsorbent contained in the coating layer 16, amine compounds, organometallic complexes, etc., can be used. Alternatively, nanoporous ceramics or mesoporous silica on which amine compounds and / or organometallic complexes are supported may be used. Among these, amine compounds are preferred from the viewpoint of greenhouse gas adsorption performance and manufacturing cost. Examples of amine compounds include monoethanolamine (MEA) and N-methyldiethanolamine (MDEA). The amine compound is preferably a solid organic compound having an amino group (one or more selected from -NH2, -NHR, -NRR' (R and R' represent organic groups)). While the present invention is not intended to be limited by theory, solid organic compounds having an amino group can adsorb greenhouse gases (particularly carbon dioxide) by reacting with them to produce carbamates or bicarbonates.

[0043] From the viewpoint of water resistance, it is desirable that solid organic compounds containing amino groups be water-insoluble. Furthermore, solid organic compounds containing amino groups may contain any of -NH2, -NHR, -NRR' (where R and R' represent organic groups), or a combination of two or more of these. Among amino groups, it is particularly preferable to contain a primary amine (-NH2) as a functional group. It is also preferable that solid organic compounds containing amino groups contain aromatic rings.

[0044] Specific examples of solid organic compounds having an amino group include weakly basic anion exchange resins having an amino group. Therefore, for example, a styrene-based copolymer having an amino group and an acrylic copolymer having an amino group can be used as the solid organic compound having an amino group. These may be used alone or in combination of two or more. Examples of the styrene-based copolymer having an amino group include a styrene-divinylbenzene copolymer. Examples of the acrylic copolymer having an amino group include a (meth)acrylic acid-divinylbenzene copolymer.

[0045] The thickness of the coat layer 16 may be determined according to the size of the cells 14, and is not particularly limited. For example, from the viewpoint of sufficiently ensuring contact with the processing gas and the purge gas, the thickness of the coat layer 16 is preferably 20 µm or more, more preferably 25 µm or more, and still more preferably 30 µm or more. On the other hand, from the viewpoint of suppressing peeling of the coat layer 16, the thickness of the coat layer 16 is preferably 400 µm or less, more preferably 380 µm or less, and still more preferably 350 µm or less.

[0046] (2. Method for recovering and desorbing greenhouse gases) The method for recovering and desorbing greenhouse gases according to an embodiment of the present invention is performed using the honeycomb structure described above. Specifically, the method for recovering greenhouse gases according to an embodiment of the present invention includes flowing a processing gas containing greenhouse gases into the cells 14 of the honeycomb structure, and causing the adsorbent to adsorb the greenhouse gases in the processing gas during this process.

[0047] Herein, "processed gas" refers to various gases containing greenhouse gases. Processed gases are not particularly limited, but include exhaust gases emitted from factories and power plants, and atmospheric air. Exhaust gases are not particularly limited, but include combustion exhaust gases generated when burning fossil fuels, coal gas (calculated from gasified coal), and natural gas at thermal power plants and steel mills. Greenhouse gases are not particularly limited, but include carbon dioxide (CO2), methane (CH4), nitrogen oxides such as nitrous oxide (N2O), hydrofluorocarbons, perfluorocarbons, and sulfur hexafluoride (SF6). Among these, the honeycomb structure according to the embodiment of the present invention is particularly useful for recovering carbon dioxide (CO2) contained in combustion exhaust gas and atmospheric air.

[0048] Furthermore, the greenhouse gas desorption method according to the embodiment of the present invention includes flowing the greenhouse gas through a cell 14 of a honeycomb structure on which the greenhouse gas has been adsorbed, and during this process, the greenhouse gas is desorbed from the adsorbent into the desorption gas. Here, the desorption gas is not particularly limited as long as it is a gas capable of desorbing carbon dioxide, but for example, water vapor can be used. The water vapor is preferably at a high temperature of 80°C or higher. The desorption gas may be heated by a heater or by mixing it with a high-temperature gas.

[0049] (3. Method for Manufacturing a Honeycomb Structure) The method for manufacturing a honeycomb structure according to the embodiment of the present invention is not particularly limited as long as it is a method capable of manufacturing the above-described honeycomb structure. A method suitable for manufacturing a honeycomb structure according to the embodiment of the present invention will be described below.

[0050] A method for manufacturing a honeycomb structure according to an embodiment of the present invention includes the steps of: manufacturing a honeycomb structure having an outer peripheral wall 11 and partition walls 15 disposed inside the outer peripheral wall 11 and partitioning a plurality of cells 14 extending from an inlet end face 12 to an outlet end face 13 (Step A); and forming a coating layer 16 containing an adsorbent on at least the surface of the partition walls 15 of the honeycomb structure (Step B).

[0051] In step A, the method for manufacturing the honeycomb structure is not particularly limited and can be carried out in accordance with methods known in the art. For example, the honeycomb structure can be manufactured as follows. First, a clay containing ceramic powder is extruded into a desired shape to produce a honeycomb molded body. At this time, the shape and density of the cells 14, the shape and thickness of the partition walls 15 and the outer peripheral walls 11 can be controlled by selecting a die and jig of an appropriate shape. In addition, the partition walls 15 having a bent structure can be formed by intentionally stopping the rotation of the roller that receives the honeycomb molded body during extrusion. Furthermore, by preparing a die with a wider outer width and a narrower central width, and increasing the extrusion speed of the clay in the central part compared to the outer part, a bent structure can be formed in the partition walls 15 that constitute the cells 14 in the central part. In addition, a bent structure can also be formed in the partition walls 15 by applying vibration during extrusion or intentionally varying the extrusion speed.

[0052] As the ceramic powder, the aforementioned ceramic powder or raw material powder that becomes the aforementioned ceramic after firing (for example, cordierite-forming raw material) can be used. Cordierite-forming raw material is a raw material that becomes cordierite upon firing. The cordierite-forming raw material preferably has a chemical composition of alumina (Al2O3) (including the portion of aluminum hydroxide that is converted to alumina): 30-45% by mass, magnesia (MgO): 11-17% by mass, and silica (SiO2): 42-57% by mass. The clay can also contain a binder, pore-forming agent, dispersant, water, organic solvent, etc. The porosity and average pore diameter of the partition wall 15 can be controlled by appropriately selecting the type and amount of ceramic powder, binder, pore-forming agent, and dispersant used.

[0053] Next, a honeycomb structure can be obtained by drying and firing the honeycomb molded body obtained above. The drying method is not particularly limited, and conventional 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, a drying method combining hot air drying with microwave drying or dielectric drying is preferred because it can dry the entire honeycomb molded body quickly and uniformly.

[0054] In step B, the method for forming the coating layer 16 is not particularly limited, but for example, it can be formed by the following method. The honeycomb structure is immersed in a slurry containing an adsorbent, an organic binder, and a dispersion medium for a predetermined time, and excess slurry from the end faces and outer circumference of the honeycomb structure is removed by blowing and wiping. The dispersion medium can be water, an organic solvent (e.g., toluene, xylene, ethanol, n-butanol, ethyl acetate, butyl acetate, terpineol, dihydroterpineol, texanol, ethylene glycol monobutyl ether acetate, diethylene glycol monoethyl ether acetate, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether acetate, diethylene glycol monobutyl ether), or a mixture thereof. After that, the functional material can be supported on the surface of the partition wall 15, etc., by drying the slurry. Drying can be done by heating the honeycomb structure to a temperature of, for example, 120 to 600°C. However, when using an adsorbent whose adsorption performance deteriorates in a high-temperature environment, the drying temperature should be limited to a temperature that does not degrade the adsorption performance. In this case, the drying temperature is preferably 100°C or lower, and more preferably 70°C or lower. The series of steps of immersion, slurry removal, and drying may be performed only once, but by repeating them multiple times, a desired amount of adsorbent can be supported.

[0055] (4. Gas Recovery Device) The gas recovery device according to the embodiment of the present invention includes the honeycomb structure described above. Because this gas recovery device is equipped with the honeycomb structure described above, even if the adsorbent expands and contracts due to repeated adsorption and desorption of greenhouse gases and a part of the coating layer 16 peels off, the bending structure of the partition wall 15 makes it difficult for the coating layer 16 to fall off the honeycomb structure. For this reason, this gas recovery device can perform adsorption and desorption of greenhouse gases over a long period of time and has a longer lifespan than conventional gas recovery devices.

[0056] A gas recovery device according to an embodiment of the present invention may further include a housing that accommodates a honeycomb structure. Preferably, the housing is connected to pipes through which a processed gas containing greenhouse gases and a desorbed gas can be supplied and discharged. With a gas recovery device having such a structure, the recovery and desorbing of greenhouse gases can be easily achieved.

[0057] The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples.

[0058] (Examples 1-4 and Comparative Example 1) Alumina, aluminum hydroxide, kaolin, talc, and silica were used as cordierite raw materials. To 100 parts by mass of these cordierite raw materials, 10 parts by mass of a pore-forming agent, 20 parts by mass of a dispersion medium, 1 part by mass of an organic binder, and 0.5 parts by mass of a dispersant were added, and the mixture was kneaded to prepare a clay body. Water was used as the dispersion medium, coke with an average particle size of 15 μm as the pore-forming agent, hydroxypropyl methylcellulose as the organic binder, and ethylene glycol as the dispersant. Next, the obtained clay body was molded using an extrusion molding machine having a predetermined die structure to obtain a quadrangular prism-shaped honeycomb molded body in which the shape of each cell in a cross section perpendicular to the direction in which the cells extend is quadrangular. In Examples 1-4, the degree of curvature of the partitions and cells was controlled to a predetermined range by adjusting the time for which the rotation of the roller receiving the honeycomb molded body was intentionally stopped. In Comparative Example 1, the rotation of the roller receiving the honeycomb molded body was not stopped. Next, the honeycomb molded body was dried in a microwave dryer, then dried in a hot air dryer, and then both ends of the honeycomb molded body were cut to the predetermined dimensions. Next, the honeycomb molded body was degreased in air at 200 to 1000°C for 3 hours, and then fired in an Ar atmosphere at 1420°C for 2 hours to obtain a honeycomb structure.

[0059] Next, a slurry containing a weakly basic anion exchange resin having amino groups, an organic binder, and water was prepared. After immersing the honeycomb structure in this slurry for a predetermined time, excess slurry from the end faces and outer circumference of the honeycomb structure was removed by blowing and wiping, and a coating layer was formed by drying at a temperature of 100°C or lower.

[0060] The degree of curvature of the partitions and cells of the obtained honeycomb structure was measured using the method described above. Furthermore, 90±5°C heated steam was circulated through the cells of the honeycomb structure for 1 hour, followed by circulating room-temperature air (with moisture removed) through the cells for 12 minutes. Afterward, the presence or absence of detachment of the coating layer was visually confirmed. The evaluation results are shown in Table 1.

[0061]

[0062] As shown in Table 1, the honeycomb structures of Examples 1 to 4, in which the degree of curvature of the partition walls was within a predetermined range, did not experience any shedding of the coating layer, whereas the honeycomb structure of Comparative Example 1, in which the degree of curvature of the partition walls was outside the predetermined range, experienced shedding of the coating layer.

[0063] As can be seen from the above results, the present invention provides a honeycomb structure and a gas recovery device in which the adsorbent-containing coating layer is less likely to fall off.

[0064] 11 Outer wall 12 Inlet end face 13 Outlet end face 14 Cell 15 Partition wall 16 Coat layer

Claims

1. A honeycomb structure comprising an outer perimeter wall, partition walls disposed inside the outer perimeter wall and forming a plurality of cells extending from an inlet end face to an outlet end face, and a coating layer formed on at least the surface of the partition walls and containing an adsorbent capable of adsorbing and desorbing greenhouse gases, wherein at least a portion of the partition walls has a bent structure in a cross section parallel to the direction in which the cells extend, and the degree of curvature of the partition walls having the bent structure is 1.01 to 1.

09.

2. The honeycomb structure according to claim 1, wherein in a cross section parallel to the direction in which the cells extend, the degree of curvature of the cells partitioned by the partition wall having the bending structure is 1.01 to 1.

04.

3. The honeycomb structure according to claim 1 or 2, wherein, in a cross section parallel to the direction in which the cell extends, the bending structure of the two partition walls facing one of the cells is symmetrical with respect to the axial center of the cell.

4. The honeycomb structure according to claim 1 or 2, wherein the bending structure of the partition wall has a period of 4.5 to 5.5 mm and an amplitude of 1.0 to 2.5 mm.

5. The honeycomb structure according to claim 1 or 2, wherein the bending structure of the partition wall is formed in a region of the partition wall parallel to the direction in which the cells extend, excluding a region from each end face to 10% of the total length.

6. The honeycomb structure according to claim 1 or 2, wherein the bending structure of the partition wall is formed in the partition wall that partitions at least the central cells in a cross section perpendicular to the direction in which the cells extend.

7. The honeycomb structure according to claim 1 or 2, wherein the bending structure of the partition wall is formed on all of the partition walls.

8. The honeycomb structure according to claim 1 or 2, wherein the adsorbent is an amine compound.

9. The honeycomb structure according to claim 8, wherein the amine compound is a weakly basic anion exchange resin having an amino group.

10. The honeycomb structure according to claim 8, wherein the amine compound contains one or more selected from styrene copolymers having amino groups and acrylic copolymers having amino groups.

11. The honeycomb structure according to claim 1 or 2, wherein the greenhouse gas is carbon dioxide.

12. A gas recovery device comprising the honeycomb structure described in claim 1 or 2.

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