Honeycomb structure and gas recovery device

Abstract

A honeycomb structure includes an outer peripheral wall 10 and a partitioning wall 14 that is provided inside the outer peripheral wall 10 and partitions / forms a plurality of cells 13 that extend from an inflow end surface 11 to an outflow end surface 12. The outer peripheral wall 10 and the partitioning wall 11 contain an adsorbent that can adsorb and desorb a greenhouse gas. In a cross-section that is orthogonal to the extension direction of the cells 13, when the region to 20% of the direct distance from the center of the honeycomb structure to the outer peripheral wall 10 is a center region R1 and the region from 80% of the direct distance is an outer peripheral region R2, the ratio of the thickness of the outer peripheral wall 10 to the thickness of the partitioning wall 14 in the center region R1 is 2.0–10.0, the ratio of the open area of the outer peripheral region R2 to the open area of the center region R1 is 0.69–0.96, and the ratio of the open area of the entire honeycomb structure to the open area of the center region R1 is at least 0.94.

Description

Honeycomb structure and gas recovery device

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

[0002] To mitigate global warming, there is a growing need for technologies that capture and utilize greenhouse gases (e.g., carbon dioxide) from gases such as the atmosphere and exhaust gases. For example, a technology for adsorbing atmospheric CO2 (DAC: Direct Air Capture) has been developed as a typical conventional carbon dioxide (CO2) capture technology. There are several types of DAC, including liquid absorption, membrane separation, and solid adsorption. Among these, solid adsorption generally involves supporting a CO2 adsorbent (absorbent) material on a substrate. Because substrates used in solid adsorption require a high specific surface area, pellet-type, sheet-type, and fiber-type supports have been mainstream. However, these supports have a high pressure loss during gas flow and require a large amount of energy in the CO2 adsorption process. Therefore, honeycomb structures are being considered as the support.

[0003] For example, Patent Document 1 describes a honeycomb structure (CO2 capture absorption structure) having a plurality of partition walls extending axially from an inlet end to an outlet end, thereby forming a plurality of cells (flow channels), and a honeycomb substrate comprising a mixture of inorganic powder components and a binder, with an amine polymer having functional structural unit groups that absorb CO2 dispersed in the inorganic powder components of the partition walls. The honeycomb structure described in Patent Document 1 can adsorb CO2 by flowing a CO2-containing process gas through the cells. Furthermore, the CO2 adsorbed in the honeycomb structure can be desorbed by flowing a purge gas (desorption gas) such as water vapor through the cells.

[0004] Special table 2015-508018 publication

[0005] As described above, CO2 adsorbed in a honeycomb structure is desorbed by passing a purge gas such as water vapor through the cells. During this process, the adsorbent (amine polymer) absorbs water and expands. As a result, the honeycomb structure expands more during CO2 desorption than during CO2 adsorption, which can lead to cracks in the peripheral wall. One possible way to prevent cracks in the peripheral wall is to increase its strength by, for example, increasing its thickness. However, the pressure caused by the expansion is concentrated in the partition walls constituting the cells on the peripheral side, making the cells more likely to twist or crack in the partition walls on the peripheral side. If cracks exist in the peripheral wall or partition walls of a honeycomb structure, repeated expansion during CO2 desorption and contraction during CO2 adsorption will cause the cracks to grow larger, ultimately resulting in damage to the honeycomb structure. Furthermore, cell twisting can cause increased pressure loss. While the above description has been given using CO2 as an example of a greenhouse gas, similar phenomena can occur when adsorbing other greenhouse gases.

[0006] The present invention has been made to solve the above-mentioned problems, and aims to provide a honeycomb structure and a gas recovery device that can suppress cracks and cell twisting in the outer wall and partition wall, have high durability, and reduce pressure loss.

[0007] The present inventors have conducted extensive research into honeycomb structures containing adsorbents capable of adsorbing and desorbing greenhouse gases, and have found that the above-mentioned problems can be solved by controlling the ratio of the thickness of the peripheral walls to the thickness of the partition walls in the central region and the ratio of the opening ratio of the peripheral region to the opening ratio of the central region within predetermined ranges, thereby completing the present invention. That is, the present invention is exemplified as follows.

[0008] <1> A honeycomb structure having a peripheral wall and partition walls disposed inside the peripheral wall and defining a plurality of cells extending from an inflow end face to an outflow end face, wherein the peripheral wall and the partition walls contain an adsorbent capable of adsorbing and desorbing greenhouse gases, wherein, in a cross section perpendicular to the direction in which the cells extend, a region that is 20% or less of a linear distance from a center of the honeycomb structure to the peripheral wall is defined as a central region, and a region that is 80% or more of the linear distance is defined as a peripheral region, the ratio of the thickness of the peripheral wall to the thickness of the partition walls in the central region is 2.0 to 10.0, the ratio of the opening rate of the peripheral region to the opening rate of the central region is 0.69 to 0.96, and the ratio of the opening rate of the entire honeycomb structure to the opening rate of the central region is 0.94 or more.

[0009] <2> The honeycomb structure according to <1>, wherein the ratio of the thickness of the outer peripheral wall to the thickness of the partition wall in the central region is 2.0 to 8.0.

[0010] <3> The honeycomb structure according to <1> or <2>, wherein the ratio of the opening ratio of the outer peripheral region to the opening ratio of the central region is 0.80 to 0.95.

[0011] <4> The honeycomb structure according to any one of <1> to <3>, wherein the thickness of the partition walls in the central region is 51 to 508 μm.

[0012] <5> The cell density of the central region is 7.8 to 93.0 cells / cm 2 <4> The honeycomb structure according to any one of <1> to <4>,

[0013] <6> The honeycomb structure according to any one of <1> to <5>, wherein the thickness of the partition walls in the outer peripheral region is 102 to 635 μm.

[0014] <7> The cell density of the outer peripheral region is 15.5 to 139.5 cells / cm 2 <6> The honeycomb structure according to any one of <1> to <6>,

[0015] <8> The honeycomb structure according to any one of <1> to <7>, wherein the cross section of the honeycomb structure perpendicular to the cell extension direction has a quadrangular shape.

[0016] <9> The honeycomb structure according to any one of <1> to <8>, wherein the shape of the cells in a cross section perpendicular to the cell extension direction is quadrangular.

[0017] <10> The honeycomb structure according to <9>, wherein in the outer peripheral region, rounded portions are formed at corners of the quadrangular cells, and the curvature radius of the rounded portions is 0.1 to 0.5 mm.

[0018] <11> The honeycomb structure according to any one of <1> to <10>, wherein a coating layer containing a water repellent agent is provided on a surface of the outer peripheral wall, and the water repellent agent permeates into the inside of the outer peripheral wall.

[0019] <12> The honeycomb structure according to any one of <1> to <11>, wherein the adsorbent is an amine compound.

[0020] <13> The honeycomb structure according to <12>, wherein the amine compound contains at least one selected from the group consisting of a weakly basic anion exchange resin having an amino group and a strongly basic anion exchange resin having an ammonium group.

[0021] <14> The honeycomb structure according to <12>, wherein the amine compound contains at least one selected from a styrene-divinylbenzene copolymer having an amino group and / or an ammonium group, and an acrylic copolymer having an amino group.

[0022] <15> The honeycomb structure according to any one of <1> to <14>, wherein the greenhouse gas is carbon dioxide.

[0023] <16> A gas recovery device including the honeycomb structure according to any one of <1> to <15>.

[0024] According to the present invention, it is possible to provide a honeycomb structure and a gas recovery device that are capable of suppressing cracks in the outer peripheral wall and partition walls and twisting of cells, and that are highly durable and capable of reducing pressure loss.

[0025] 1A is a schematic diagram of a cross section perpendicular to the cell extension direction of a honeycomb structure according to an embodiment of the present invention. FIG. 1B is a schematic diagram of a cross section taken along line a-a' of the honeycomb structure shown in FIG. 1A. FIG. 1C is a schematic diagram of a cross section perpendicular to the cell extension direction of another honeycomb structure according to an embodiment of the present invention. FIG. 1D is a schematic diagram of a cross section perpendicular to the cell extension direction of another honeycomb structure according to an embodiment of the present invention.

[0026] The honeycomb structure of the present invention has a peripheral wall and partition walls disposed inside the peripheral wall and defining a plurality of cells extending from an inflow end face to an outflow end face, the peripheral wall and partition walls containing an adsorbent capable of adsorbing and desorbing greenhouse gases. In a cross section perpendicular to the cell extension direction, when a region that is 20% or less of the linear distance from the center of the honeycomb structure to the peripheral wall is defined as a central region and a region that is 80% or more of the linear distance from the center of the honeycomb structure to the peripheral wall is defined as a peripheral region, the ratio of the thickness of the peripheral wall to the thickness of the partition walls in the central region is 2.0 to 10.0, the ratio of the opening ratio of the peripheral region to the opening ratio of the central region is 0.69 to 0.96, and the ratio of the opening ratio of the entire honeycomb structure to the opening ratio of the central region is 0.94 or more. In the honeycomb structure of the present invention, the ratio of the thickness of the peripheral wall to the thickness of the partition wall in the central region, the ratio of the aperture ratio of the peripheral region to the aperture ratio of the central region, and the ratio of the aperture ratio of the entire honeycomb structure to the aperture ratio of the central region are controlled within predetermined ranges, thereby making it possible to suppress cracks in the peripheral wall and partition walls and cell distortion, and therefore the honeycomb structure of the present invention has high durability and can reduce pressure loss.

[0027] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings as necessary. 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 ordinary knowledge of those skilled in the art without departing from the spirit of the present invention are also within the scope of the present invention.

[0028] (1. Honeycomb Structure) The honeycomb structure according to the embodiment of the present invention can be suitably used to recover greenhouse gases contained in a process gas. Examples of the process gas include, but are not limited to, exhaust gases emitted from factories and power plants, and the atmosphere. Examples of the exhaust gas include, but are not limited to, combustion exhaust gases generated when burning fossil fuels, coal gas produced by gasifying coal, and natural gas in thermal power plants and steelworks. Examples of the greenhouse gas include, but are not limited to, carbon dioxide (CO2), methane (CH4), nitrogen oxides such as nitrous oxide (NO), hydrofluorocarbons, perfluorocarbons, sulfur hexafluoride (SF6), and the like. 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 the atmosphere.

[0029] Fig. 1A is a schematic diagram of a cross section perpendicular to the cell extension direction of a honeycomb structure according to an embodiment of the present invention. Fig. 1B is a schematic diagram of a cross section of the honeycomb structure shown in Fig. 1A taken along line a-a' (schematic diagram of a cross section parallel to the cell extension direction). The honeycomb structure shown in Figs. 1A and 1B has an outer peripheral wall 10 and partition walls 14 disposed inside the outer peripheral wall 10 and defining a plurality of cells 13 extending from an inflow end face 11 to an outflow end face 12, and the outer peripheral wall 10 and the partition walls 14 contain an adsorbent (hereinafter abbreviated as "adsorbent") capable of adsorbing and desorbing greenhouse gases. The plurality of cells 13 are arranged parallel to one another. The honeycomb structure is a flow-through type in which both end faces (inlet end face 11 and outlet end face 12) of each cell 13 are open. When a process gas (e.g., air) containing greenhouse gases flows in from the inlet end face 11, the greenhouse gases are adsorbed as it passes through the multiple cells 13, and the process gas with a reduced concentration of greenhouse gases flows out from the outlet end face 12.

[0030] In a cross section ( FIG. 1A ) of the honeycomb structure perpendicular to the direction in which the cells 13 extend, a central region R1 (shaded area) is defined as a region that is 20% or less of the linear distance from the center P of the honeycomb structure to the peripheral wall 10, and a peripheral region R2 (shaded area) is defined as a region that is 80% or more of the linear distance. The ratio of the thickness of the partition walls 14 in the central region R1 to the thickness of the peripheral wall 10 is 2.0 to 10.0, preferably 2.0 to 8.0. Furthermore, the ratio of the aperture ratio of the peripheral region R2 to the aperture ratio of the central region R1 is 0.69 to 0.96, preferably 0.80 to 0.95. Furthermore, the ratio of the aperture ratio of the entire honeycomb structure to the aperture ratio of the central region R1 is 0.94 or more, preferably 0.95 or more, more preferably 0.96 or more. The upper limit of the ratio of the overall opening rate of the honeycomb structure to the opening rate of the central region R1 is not particularly limited, but is generally 1.10 or less, preferably 1.05 or less, and more preferably 1.00 or less. By controlling these ratios within the above ranges, the strength of the peripheral wall 10 can be increased and durability can be ensured that the honeycomb structure can withstand the stress associated with expansion of the honeycomb structure during desorption of greenhouse gases. Furthermore, cell distortion in the peripheral region R2 due to expansion of the honeycomb structure during desorption of greenhouse gases can be suppressed, thereby reducing pressure loss.

[0031] Here, the boundary of the central region R1 (a position at 20% of the linear distance from the center P of the honeycomb structure to the peripheral wall 10) is present in the partition wall 14 in Fig. 1A, but may be present in the cell 13 as shown in Fig. 2. Similarly, the boundary of the peripheral region R2 (a position at 80% of the linear distance from the center P of the honeycomb structure to the peripheral wall 10) is present in the partition wall 14 in Fig. 1A, but may be present in the cell 13 as shown in Fig. 2. Note that Fig. 2 is a schematic diagram of a cross section perpendicular to the cell extension direction of another honeycomb structure according to an embodiment of the present invention.

[0032] The thickness of the peripheral wall 10 in this specification refers to the length in the normal direction of the peripheral surface from the boundary between the peripheral wall 10 and the outermost cell 13 or partition wall 14 to the peripheral surface of the honeycomb structure in a cross section ( FIG. 1A ) perpendicular to the extension direction of the cells 13 of the honeycomb structure. The thickness of the partition wall 14 in this specification refers to the length of the portion of the line segment connecting the centers of gravity of adjacent cells 13 that passes through the partition wall 14 in a cross section ( FIG. 1A ) perpendicular to the extension direction of the cells 13 of the honeycomb structure. Furthermore, the thickness of the partition wall 14 in a predetermined region means the average value of the thicknesses of all the partition walls 14 present in the predetermined region. The opening ratio in this specification refers to the value obtained by dividing the total area of ​​the cells 13 present in a predetermined region by the area of ​​the predetermined region in a cross section ( FIG. 1A ) perpendicular to the extension direction of the cells 13 of the honeycomb structure. Therefore, the opening ratio of the central region R1 is a value obtained by dividing the total area of ​​the cells 13 present in the central region R1 by the area of ​​the central region R1 (total area of ​​the cells 13 and partition walls 14) in a cross section ( FIG. 1A ) perpendicular to the extension direction of the cells 13 of the honeycomb structure. Also, the opening ratio of the peripheral region R2 is a value obtained by dividing the total area of ​​the cells 13 present in the peripheral region R2 by the area of ​​the peripheral region R2 (total area of ​​the peripheral wall 10, cells 13, and partition walls 14) in a cross section ( FIG. 1A ) perpendicular to the extension direction of the cells 13 of the honeycomb structure.

[0033] The aperture ratio of each of the above-mentioned regions and the entire region can be controlled by adjusting the thickness of the outer wall 10 and the partition walls 14, the shape and size of the cells 13, and the like.

[0034] The shape of the honeycomb structure in a cross section perpendicular to the extension direction of the cells 13 is not particularly limited, and may be, for example, a round shape such as a circle, an ellipse, a racetrack shape, or an oval, a polygonal shape such as a triangle or a rectangle, or other irregular shape. Among these, a quadrangle is preferable as the cross-sectional shape of the honeycomb structure. The outer shape of the honeycomb structure can typically be a columnar shape. The honeycomb structure shown in Figures 1A and 1B has a quadrangle cross-sectional shape and is an example of a quadrangular columnar shape as a whole.

[0035] The length of the honeycomb structure in the direction in which the cells 13 extend (the length from the inlet end face 11 to the outlet end face 12) is not particularly limited and may be set appropriately depending on the application and required performance. However, while a longer length of the honeycomb structure in the direction in which the cells 13 extend can increase the amount of greenhouse gases adsorbed, if the length is too long, pressure loss increases. For this reason, the length is preferably 20 to 350 mm, more preferably 20 to 300 mm, and even more preferably 20 to 250 mm.

[0036] The diameter of the cross section perpendicular to the extension direction of the cells 13 of the honeycomb structure is not particularly limited and may be set appropriately depending on the application and required performance. However, while a larger diameter of the cross section of the honeycomb structure can increase the amount of greenhouse gases adsorbed, if the diameter is too large it increases the difficulty of manufacturing, so the diameter is preferably 20 to 450 mm, more preferably 20 to 400 mm, and even more preferably 20 to 350 mm. Here, the diameter of the cross section of the honeycomb structure in this specification means the diameter if the honeycomb structure is circular, and means the circle-equivalent diameter if the honeycomb structure is other than circular.

[0037] The thickness of the partition walls 14 in the central region R1 is not particularly limited, but is preferably 30 to 600 μm, more preferably 40 to 550 μm, and even more preferably 51 to 508 μm. By controlling the thickness of the partition walls 14 in the central region R1 within such a range, the effect of suppressing cracks and cell twisting in the outer peripheral wall 10 and the partition walls 14 can be stably obtained.

[0038] The thickness of the partition walls 14 in the outer peripheral region R2 is not particularly limited, but is preferably 50 to 700 μm, more preferably 80 to 650 μm, and even more preferably 102 to 635 μm. By controlling the thickness of the partition walls 14 in the outer peripheral region R2 within such a range, the effect of suppressing cracks and cell twisting in the outer peripheral wall 10 and the partition walls 14 can be stably obtained.

[0039] The thickness of the partition walls 14 in the region other than the central region R1 and the outer peripheral region R2 is not particularly limited, but is preferably 30 to 600 μm, more preferably 40 to 550 μm, and even more preferably 51 to 508 μm. By controlling the thickness of the partition walls 14 in the region other than the central region R1 and the outer peripheral region R2 within such a range, the effect of suppressing cracks and cell twisting in the outer peripheral wall 10 and the partition walls 14 can be stably obtained.

[0040] The thickness of the outer wall 10 is not particularly limited, but is preferably 100 to 4000 μm, more preferably 200 to 3500 μm, and even more preferably 300 to 3000 μm. By controlling the thickness of the outer wall 10 within such a range, it becomes easier to improve the strength (durability) of the honeycomb structure.

[0041] The cell density (the number of cells 13 per unit cross-sectional area) of the central region R1 is not particularly limited, but is preferably 6.0 to 110.0 cells / cm 2 , more preferably 7.0 to 100.0 cells / cm 2 , more preferably 7.8 to 93.0 cells / cm 2 By controlling the cell density of the central region R1 within such a range, it becomes easier to reduce the pressure loss of the honeycomb structure.

[0042] The cell density (the number of cells 13 per unit cross-sectional area) of the outer peripheral region R2 is not particularly limited, but is preferably 10.0 to 150.0 cells / cm 2 , more preferably 12.0 to 140.0 cells / cm 2 , more preferably 15.5 to 139.5 cells / cm 2 By controlling the cell density of the outer peripheral region R2 within such a range, it becomes easier to improve the strength (durability) of the honeycomb structure.

[0043] The cell density (the number of cells 13 per unit cross-sectional area) of the region other than the central region R1 and the peripheral region R2 is preferably 6.0 to 110.0 cells / cm 2 , more preferably 7.0 to 100.0 cells / cm 2 , more preferably 7.8 to 93.0 cells / cm 2By controlling the cell density of the region in this range, it becomes easier to reduce the pressure loss of the honeycomb structure.

[0044] Here, the cell density in this specification refers to a value obtained by dividing the number of cells 13 present in a predetermined region in a cross section ( FIG. 1A ) of the honeycomb structure perpendicular to the direction in which the cells 13 extend by the area of ​​the predetermined region. Therefore, the cell density of the central region R1 is a value obtained by dividing the number of cells 13 present in the central region R1 by the area of ​​the central region R1 (the total area of ​​the cells 13 and the partition walls 14) in a cross section ( FIG. 1A ) of the honeycomb structure perpendicular to the direction in which the cells 13 extend. Furthermore, the cell density of the peripheral region R2 is a value obtained by dividing the number of cells 13 present in the peripheral region R2 by the area of ​​the peripheral region R2 (the total area of ​​the peripheral wall 10, the cells 13, and the partition walls 14) in a cross section ( FIG. 1A ) of the honeycomb structure perpendicular to the direction in which the cells 13 extend.

[0045] The shape of the cells 13 in the cross section (FIG. 1A) of the honeycomb structure perpendicular to the extension direction of the cells 13 is not particularly limited, but is preferably a rectangle, a hexagon, an octagon, a circle, or a combination thereof. Among these, the shape of the cells 13 is preferably a rectangle (e.g., a square) or a hexagon, and more preferably a square. By configuring the cells 13 in this shape, it becomes easier to reduce the pressure loss of the honeycomb structure.

[0046] In the peripheral region R2, it is preferable that rounded portions are formed at the quadrangular corners of the cells 13. Here, a schematic diagram of a honeycomb structure having cells 13 with rounded portions formed at the quadrangular corners is shown in FIG. 3. Note that FIG. 3 is a schematic diagram of a cross section perpendicular to the cell extension direction of the honeycomb structure. In the honeycomb structure shown in FIG. 3, rounded portions are formed at the quadrangular corners of the cells 13 in the peripheral region R2. It is preferable that the radius of curvature of the rounded portions is 0.1 to 0.5 mm. By providing cells 13 with such rounded portions, it is possible to improve the durability of the honeycomb structure against expansion during desorption of greenhouse gases.

[0047] The outer peripheral wall 10 and partition walls 14 that constitute the honeycomb structure contain an adsorbent. By incorporating an adsorbent into the outer peripheral wall 10 and partition walls 14, it becomes possible to adsorb and desorb greenhouse gases. Furthermore, compared to conventional honeycomb structures in which the surfaces of the outer peripheral wall 10 and partition walls 14 are coated with an adsorbent, this structure is manufactured without undergoing a firing process that requires high heating temperatures, which makes it possible to reduce greenhouse gases generated during manufacturing. Furthermore, since the amount of greenhouse gas carried can be increased, the amount of greenhouse gas adsorption can also be increased.

[0048] The adsorbent is not particularly limited as long as it is capable of adsorbing and desorbing greenhouse gases, but is preferably an amine compound. Specifically, the amine compound is preferably a solid organic compound having one or more amino groups (one or more selected from -NH, -NHR, and -NRR' (R and R' represent organic groups)) and one or more ammonium groups. While not intending to limit the present invention by theory, a solid organic compound having one or more amino groups and ammonium groups can adsorb greenhouse gases (particularly carbon dioxide) by reacting with the greenhouse gas to produce a carbamate or bicarbonate.

[0049] From the viewpoint of water resistance, a solid organic compound having one or more selected from an amino group and an ammonium group is desirably water-insoluble. Furthermore, a solid organic compound having one or more selected from an amino group and an ammonium 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 to have a primary amine (-NH2) as a functional group. It is also preferable that a solid organic compound having one or more selected from an amino group and an ammonium group contains an aromatic ring.

[0050] Specific examples of solid organic compounds having one or more selected from amino groups and ammonium groups include weakly basic anion exchange resins having amino groups and strongly basic anion exchange resins having ammonium groups. Therefore, for example, solid organic compounds having one or more selected from amino groups and ammonium groups can be styrene-divinylbenzene copolymers having amino groups and / or ammonium groups (e.g., copolymers of styrene and divinylbenzene) or acrylic copolymers having amino groups (e.g., copolymers of divinylbenzene with one or both of acrylic acid and methacrylic acid). Furthermore, OH-type, Cl-type, and HCO3-type resins can also be used as strongly basic anion exchange resins, but for applications involving carbon dioxide adsorption, OH-type or HCO3-type resins are preferred.

[0051] From the viewpoint of greenhouse gas 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. From the viewpoint of greenhouse gas adsorption performance, the exchange capacity of the strongly basic anion exchange resin is preferably 0.6 meq / mL or more, more preferably 0.8 meq / mL or more, and even more preferably 1.0 meq / mL or more. Here, the exchange capacity of the weakly basic anion exchange resin is measured by the tapping method, where 10 mL of the ion exchange resin is treated with hydrochloric acid, the excess hydrochloric acid is washed away with ethanol, and the amount of chloride ions that flow out when aqueous ammonia is passed through. The exchange capacity of the strongly basic anion exchange resin is measured by the tapping method, where 10 mL of the ion exchange resin is treated with hydrochloric acid, the excess hydrochloric acid is washed away with ethanol, and the amount of chloride ions that flow out when aqueous sodium hydroxide is passed through.

[0052] The content of the adsorbent in the outer peripheral wall 10 and the partition walls 14 is not particularly limited, but is preferably 40 to 94 mass%, more preferably 50 to 90 mass%, and even more preferably 60 to 80 mass%. By setting the content within such a range, the proportion of the adsorbent can be increased, thereby improving the adsorption performance of greenhouse gases.

[0053] The outer wall 10 and the partition walls 14 may further contain a binder in addition to the adsorbent. By including a binder, the strength of the honeycomb structure can be increased. The binder is not particularly limited, but an organic binder or an inorganic binder can be used.

[0054] Examples of organic binders include methyl cellulose, hydroxypropyl methyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, carboxymethyl cellulose, polyvinyl alcohol, hydroxyethyl methyl cellulose, polyvinyl acetal, polyethylene oxide, polyvinyl butyral, polybutadiene, methacrylic acid ester, acrylic, ethyl cellulose, silicone, polyolefin, etc. In particular, the use of water-soluble organic binders such as methyl cellulose, hydroxypropyl methyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, carboxymethyl cellulose, polyvinyl alcohol, hydroxyethyl methyl cellulose, polyvinyl acetal, polyethylene oxide, etc. can reduce environmental impact, the risk of organic solvent vapor during drying, and production costs.

[0055] Examples of inorganic binders include clay, diatomaceous earth, layered clay minerals, montmorillonite, hydrotalcite, activated clay, acid clay, hectorite, halloysite, attapulgite, silica, alumina, talc, chlorite, vermiculite, mica, illite, pyrophyllite, sericite, kaolin, sepiolite, boehmite, palygorskite, and bentonite.

[0056] The content of the organic binder in the outer peripheral wall 10 and the partition walls 14 is not particularly limited, but is preferably 3 to 20 mass%, more preferably 5 to 15 mass%, and even more preferably 5 to 10 mass%. The content of the inorganic binder in the outer peripheral wall 10 and the partition walls 14 is not particularly limited, but is preferably 0 to 55 mass%, more preferably 0 to 50 mass%, and even more preferably 0 to 40 mass%.

[0057] In addition to the above components, the outer peripheral wall 10 and the partition walls 14 may further contain known additives such as surfactants and pore-forming materials, as long as the effects of the present invention are not impaired. Specific examples of surfactants include ethylene glycol, dextrin, fatty acid soap, and polyalcohol. These may be used alone or in combination of two or more. Specific examples of pore-forming materials include wood flour, activated carbon, hollow resins, porous resins, hollow inorganic materials, and porous inorganic materials. These may be used alone or in combination of two or more.

[0058] It is preferable that a coating layer containing a water repellent agent is provided on the surface of the outer peripheral wall 10. Since the outer peripheral wall 10 has pores, by forming a coating layer on the surface of the outer peripheral wall 10, the water repellent agent penetrates into the interior of the outer peripheral wall 10. By providing such a coating layer, the water resistance of the honeycomb structure can be improved. There are no particular limitations on the water repellent agent, and known agents can be used. Examples of water repellents include stearic acid, fluororesin, and silicone resin.

[0059] (2. Greenhouse gas recovery method and desorption method) The greenhouse gas recovery method and desorption method according to the embodiment of the present invention are carried out using the above-mentioned honeycomb structure. Specifically, the greenhouse gas recovery method according to the embodiment of the present invention includes flowing a process gas containing a greenhouse gas through the cells 13 of the honeycomb structure, and adsorbing the greenhouse gas in the process gas by an adsorbent during the process.

[0060] Furthermore, a method for desorbing greenhouse gases according to an embodiment of the present invention includes flowing the greenhouse gas through the cells 13 of the honeycomb structure in which the greenhouse gas has been adsorbed, and desorbing the greenhouse gas from the adsorbent into the desorbed gas during this process. The desorbed 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 desorbed gas may be heated by a heater or by mixing with a high-temperature gas.

[0061] (3. Manufacturing Method of Honeycomb Structure) The manufacturing method of the honeycomb structure according to the embodiment of the present invention is not particularly limited as long as it is a method that can manufacture the above-mentioned honeycomb structure. Hereinafter, a method suitable for manufacturing the honeycomb structure according to the embodiment of the present invention will be described.

[0062] The honeycomb structure manufacturing method according to an embodiment of the present invention is manufactured by a method including a clay preparation process (first process), a molding process into a honeycomb molded body (second process), and a drying process of the honeycomb molded body (third process).

[0063] The clay preparation step (first step) is a step of kneading a molding raw material containing an adsorbent and a binder (organic binder and inorganic binder) to prepare a clay. The molding raw material may further contain a solvent. The solvent (dispersion medium) is not particularly limited, and examples thereof include water and a mixed solvent of water and an organic solvent such as alcohol, but water is particularly preferred.

[0064] The content of the adsorbent excluding the solvent in the forming raw material is preferably 40 to 94% by mass, more preferably 50 to 92% by mass, and even more preferably 60 to 90% by mass, from the viewpoint of achieving a good balance between greenhouse gas adsorption performance, crack suppression during drying, and water resistance. From the same viewpoint, the organic binder content excluding the solvent in the forming raw material is preferably 3 to 20% by mass, more preferably 5 to 15% by mass, and even more preferably 5 to 10% by mass. The inorganic binder content excluding the solvent in the forming raw material is preferably 0 to 55% by mass, more preferably 0 to 50% by mass, and even more preferably 0 to 40% by mass. The solvent content in the forming raw material is adjusted so as to obtain a clay with a hardness suitable for forming (particularly, extrusion forming).

[0065] The molding raw materials containing the above-mentioned components can be kneaded using a known kneader, and it is desirable to carry out the kneading for a time required for each component to be uniformly distributed in the clay.

[0066] The forming step (second step) into a honeycomb formed body is a step of forming the clay obtained in the first step into a honeycomb formed body. Specifically, in the second step, the honeycomb formed body is extruded to have an outer peripheral wall 10 and partition walls 14 disposed inside the outer peripheral wall 10 and defining a plurality of cells 13 extending from an inlet end face 11 to an outlet end face 12. In the extrusion forming, a die having a desired overall shape, cell shape, partition wall thickness, cell density, etc. can be used.

[0067] The honeycomb formed body drying step (third step) is a step of drying the honeycomb formed body obtained in the second step. Since the honeycomb formed body immediately after molding 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 because it allows the entire honeycomb formed body to be dried quickly and uniformly. From the viewpoint of suppressing decomposition of the adsorbent and organic binder, 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.

[0068] When forming a coating layer containing a water repellent on the surface of the outer peripheral wall 10, the coating method is not particularly limited, and known methods can be used. For example, a slurry containing a water repellent and a solvent (e.g., water) may be applied to the outer peripheral wall 10 and dried. The drying conditions are not particularly limited, but may be the same as those in the third step described above.

[0069] (4. Gas Recovery Apparatus) A gas recovery apparatus according to an embodiment of the present invention includes the above-described honeycomb structure. Since this gas recovery apparatus includes the above-described honeycomb structure, it has high durability and can reduce pressure loss.

[0070] The gas recovery device according to the embodiment of the present invention may further include a housing that accommodates the honeycomb structure. The housing is preferably connected to a pipe through which a treatment gas containing greenhouse gases and a desorbed gas can be supplied and discharged. A gas recovery device having such a structure can easily achieve the recovery and desorption of greenhouse gases.

[0071] The present invention will be described in detail below with reference to examples, but the present invention should not be construed as being limited to these examples.

[0072] <Materials Used> The following commercially available water-insoluble weakly basic anion exchange resin (a styrene-divinylbenzene polymer having a primary amine functional group with an exchange capacity of 2.0 meq / mL) was prepared as a carbon dioxide adsorbent. Stearic acid was prepared as a water repellent. Methylcellulose was prepared as an organic binder. Sepiolite was prepared as an inorganic binder. Industrial water was prepared as a solvent.

[0073] A carbon dioxide adsorbent, an organic binder, an inorganic binder, and a solvent were blended to obtain a molding raw material. The carbon dioxide adsorbent content in the molding raw material (excluding the solvent) was 75 mass%, the organic binder content was 15 mass%, and the inorganic binder content was 10 mass%. The amount of solvent blended was adjusted so that the clay had a hardness suitable for molding. Next, the clay was molded using an extrusion molding machine with a predetermined die structure to obtain a honeycomb molded body. The die structure was selected so that the honeycomb molded body (honeycomb structure) after drying would meet the conditions shown in Table 1 and below. Outer shape: rectangular pillar-shaped Cross-sectional shape perpendicular to the cell extension direction of the honeycomb structure: 120 mm x 120 mm square Length in the cell extension direction of the honeycomb structure: 150 mm

[0074] Next, the obtained honeycomb molded body was subjected to high-frequency dielectric drying, and then dried for 2 minutes in an air atmosphere at a temperature of 100°C using a microwave dryer, and both end faces were cut off by a predetermined amount to prepare a honeycomb structure. In addition, in some of the examples and comparative examples, a coating layer was formed by applying a slurry containing a water repellent agent and water to the outer wall and drying it at 100°C.

[0075]

[0076] Next, the honeycomb structure obtained above was evaluated as follows.

[0077] <Mechanical strength> A weight of 2 kg (corresponding to the mass of approximately four honeycomb structures) (the width of the weight was the same as that of the honeycomb structure) was placed on the honeycomb structure and left for approximately 30 seconds. Similar weights were placed on the other three sides, and the presence or absence of damage such as cracks was visually confirmed. In this evaluation, the case where damage such as cracks was observed was represented as 0, and the case where damage such as cracks was not observed was represented as 1.

[0078] <Water Resistance Strength> A honeycomb structure was placed in a 170 mm x 170 mm x 200 mm container filled with standing water and left for approximately one hour. The honeycomb structure was then removed and the end and side surfaces of the honeycomb structure were inspected for cracks and cell twist at the end surfaces. Cracks and cell twist were observed using a microscope at 50x magnification. Cell twist was evaluated by measuring the lengths of two straight lines passing through the center of gravity of the cell between opposing sides of the cell. If the difference between the lengths of these two lines was 10% or less, it was determined that there was no cell twist. If the difference exceeded 10%, it was determined that there was cell twist. In this evaluation, a score of 0 was given if cracks and / or cell twist were observed, and a score of 1 was given if no cracks or cell twist were observed.

[0079] <Pressure Loss> After the honeycomb structure was placed in a holder and placed in a sealed container, pressure sensors were installed on the inlet end and outlet end of the honeycomb structure. Air at 25°C was then flowed at a flow rate of 3,000 kg / h, and the pressure difference between the inlet end and the outlet end was determined as the pressure loss. Because the pressure loss varied significantly depending on the aperture ratio of the central region, one of the comparative examples with the same aperture ratio of the central region was used as a comparison standard, and the following relative evaluation was performed relative to the comparison standard (excluding Comparative Examples 14 and 15). Details of the comparison standard are shown in Table 2. A score of 0 indicates a pressure difference (pressure loss) increase of 20% or more compared to the comparison standard, and a score of 1 indicates a comparison standard (including Comparative Examples 14 and 15, which had no comparison) or an increase in the pressure difference (pressure loss) of less than 20% compared to the comparison standard.

[0080] <Overall Evaluation> The overall evaluation was calculated by multiplying the scores (0 or 1) for mechanical strength, water resistance, and pressure loss. An overall evaluation of 0 means that durability against stress during expansion is insufficient and / or the pressure loss is equal to or less than that of existing technologies, while an overall evaluation of 1 means that durability against stress during expansion is sufficient and the pressure loss is better than that of existing technologies.

[0081] The results of the above evaluation are shown in Table 2.

[0082]

[0083] As shown in Table 1, the honeycomb structures of the examples in which the ratio of the thickness of the outer wall to the thickness of the partition wall in the central region was 2.0 to 10.0, the ratio of the opening rate of the outer region to the opening rate of the central region was 0.69 to 0.96, and the ratio of the opening rate of the entire honeycomb structure to the opening rate of the central region was 0.94 or more were given an overall rating of 1. In contrast, the honeycomb structures of the comparative examples were given an overall rating of 0 because at least one of the ratio of the thickness of the outer wall to the thickness of the partition wall in the central region, the ratio of the opening rate of the outer region to the opening rate of the central region, and the ratio of the opening rate of the entire honeycomb structure to the opening rate of the central region was outside the predetermined range.

[0084] As can be seen from the above results, the present invention can provide a honeycomb structure and a gas recovery device that can suppress cracks in the outer peripheral wall and partition walls and cell twisting, have high durability, and reduce pressure loss.

[0085] 10: outer peripheral wall 11: inlet end face 12: outlet end face 13: cell 14: partition wall P: center R1: central region R2: outer peripheral region

Claims

1. A honeycomb structure having an outer peripheral wall and partition walls arranged inside the outer peripheral wall and defining a plurality of cells extending from the inflow end face to the outflow end face, wherein the outer peripheral wall and the partition walls contain an adsorbent capable of adsorbing and desorbing greenhouse gases, wherein, in a cross section perpendicular to the direction in which the cells extend, when a region that is 20% or less of the linear distance from the center of the honeycomb structure to the outer peripheral wall is defined as a central region and a region that is 80% or more of the linear distance from the center of the honeycomb structure to the outer peripheral wall is defined as a peripheral region, the ratio of the thickness of the outer peripheral wall to the thickness of the partition walls in the central region is 2.0 to 10.0, the ratio of the opening rate of the outer peripheral region to the opening rate of the central region is 0.69 to 0.96, and the ratio of the opening rate of the entire honeycomb structure to the opening rate of the central region is 0.94 or more.

2. A honeycomb structure according to claim 1, wherein the ratio of the thickness of said outer peripheral wall to the thickness of said partition wall in said central region is 2.0 to 8.

0.

3. A honeycomb structure according to claim 1 or 2, wherein the ratio of the opening ratio of said peripheral region to the opening ratio of said central region is 0.80 to 0.

95.

4. A honeycomb structure according to claim 1 or 2, wherein the thickness of the partition walls in the central region is 51 to 508 μm.

5. The cell density of the central region is 7.8 to 93.0 cells / cm 2 The honeycomb structure according to claim 1 or 2, wherein 6. A honeycomb structure according to claim 1 or 2, wherein the thickness of the partition walls in the outer peripheral region is 102 to 635 μm.

7. The cell density of the outer peripheral region is 15.5 to 139.5 cells / cm 2 The honeycomb structure according to claim 1 or 2, wherein 8. A honeycomb structure according to claim 1 or 2, wherein the cross section of said honeycomb structure perpendicular to the direction in which said cells extend is quadrangular.

9. A honeycomb structure according to claim 1 or 2, wherein the shape of the cells in a cross section perpendicular to the direction in which the cells extend is quadrangular.

10. A honeycomb structure according to claim 9, wherein in the outer peripheral region, rounded portions are formed at the corners of the quadrangular cells, and the radius of curvature of the rounded portions is 0.1 to 0.5 mm.

11. A honeycomb structure according to claim 1 or 2, wherein a coating layer containing a water repellent agent is provided on the surface of the outer peripheral wall, and the water repellent agent permeates into the interior of the outer peripheral wall.

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

13. The honeycomb structure according to claim 12, wherein the amine compound contains at least one selected from the group consisting of a weakly basic anion exchange resin having an amino group and a strongly basic anion exchange resin having an ammonium group.

14. A honeycomb structure according to claim 12, wherein the amine compound contains at least one selected from a styrene-divinylbenzene copolymer having an amino group and / or an ammonium group, and an acrylic copolymer having an amino group.

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

16. A gas recovery device comprising the honeycomb structure according to claim 1 or 2.

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