Honeycomb structure

Abstract

This honeycomb structure (10) comprises a peripheral wall (11), partition walls (12) that partition the interior of the peripheral wall (11) into a plurality of cells (S) extending in the axial direction of the peripheral wall (11), a carrier supported on the surface of the partition walls (12), and a carbon dioxide adsorbent supported on the carrier. The partition walls (12) have a skeleton portion mainly composed of ceramic, and metallic silicon that fills gaps in the skeleton portion and covers the surface of the skeleton portion. The metallic silicon content of the partition walls (12) is 20-40 mass%. The porosity of the honeycomb structure 10 is 15% or less.

Description

Honeycomb structure

[0001] This disclosure relates to a honeycomb structure having partition walls inside a peripheral wall.

[0002] It is widely known that carbon dioxide concentration strongly influences global warming. Therefore, various methods are being explored to effectively reduce carbon dioxide concentration by adsorbing carbon dioxide released into the atmosphere.

[0003] For example, Patent Document 1 discloses an adsorption structure for recovering carbon dioxide. The adsorption structure has a honeycomb substrate with partitions. The honeycomb substrate has reaction channels through which a carbon dioxide gas flow passes and heat exchange channels through which a heat exchange medium such as water flows. The heat exchange channels have an impermeable coating layer made of a polymer material.

[0004] Special table 2015-514011 publication

[0005] However, in the adsorption structure disclosed in Reference 1, the heat exchange channel has an impermeable coating layer made of polymer material, resulting in poor thermal conductivity between the heat exchange channel and the reaction channel. In other words, it takes time for the reaction channel to reach the reaction temperature necessary to adsorb and release carbon dioxide gas. On the other hand, if there is no impermeable coating layer, although thermal conductivity is improved, the waterproofness of the reaction channel cannot be guaranteed. In other words, the amount of carbon dioxide gas adsorbed by the reaction channel may decrease.

[0006] This invention has been made in view of these circumstances, and its purpose is to provide a honeycomb structure that combines excellent waterproofing and thermal conductivity.

[0007] The honeycomb structure for solving the above problems comprises a peripheral wall, a partition wall that divides the interior of the peripheral wall into a plurality of cells extending in the axial direction of the peripheral wall, a carrier supported on the surface of the partition wall, and a carbon dioxide adsorbent supported on the carrier, wherein the partition wall has a skeletal portion mainly composed of ceramic and metallic silicon that fills the gaps in the skeletal portion and covers the surface of the skeletal portion, the content of the metallic silicon in the partition wall is 20% by mass or more and 40% by mass or less, and the porosity of the honeycomb structure is 15% or less.

[0008] This configuration allows for excellent waterproofing and thermal conductivity. Therefore, when recovering carbon dioxide using the above honeycomb structure, water can be used as a heat exchange medium, for example. Since water is inexpensive as a heat exchange medium, carbon dioxide can be recovered efficiently and at low cost.

[0009] Regarding the above honeycomb structure, it is preferable that the ceramic is at least one selected from silicon carbide, alumina, and cordierite. This configuration allows for a further improvement in the heat resistance of the partition walls. Furthermore, when the ceramic is silicon carbide, the thermal conductivity of the partition walls can be further improved.

[0010] Regarding the above honeycomb structure, the thickness of the partition wall is preferably 0.05 mm or more and 0.6 mm or less. With this configuration, both waterproofing and thermal conductivity can be fully demonstrated.

[0011] Regarding the above-described honeycomb structure, it is preferable that the carbon dioxide adsorbent is an amine compound. With this configuration, carbon dioxide can be recovered by a chemical reaction between the amine compound and carbon dioxide. In this case, since the amine compound is placed on the surface of the partition wall, the contact area with carbon dioxide can be increased, and carbon dioxide can be recovered efficiently.

[0012] In the above-described honeycomb structure, it is preferable that the skeletal portion is composed of multiple ceramic particles in contact with each other. With this configuration, if stress is applied to the honeycomb structure and a crack occurs in the skeletal portion, the propagation of the crack can be suppressed.

[0013] Figure 1 is a perspective view of a honeycomb structure. Figure 2(a) is a perspective view of the honeycomb structure, and Figure 2(b) shows the components that make up the partition wall of the honeycomb structure. Figures 3(a) to 3(c) are schematic diagrams showing the flow of a waterproofing test.

[0014] An embodiment of the honeycomb structure according to the present invention will be described. As shown in Figure 1, the honeycomb structure 10 is configured in a prismatic shape. The honeycomb structure 10 comprises a peripheral wall 11, a partition wall 12 that divides the interior of the peripheral wall 11 into a plurality of cells S extending in the axial direction of the peripheral wall 11, a carrier supported on the surface of the partition wall 12, and a carbon dioxide adsorbent supported on the carrier. Note that the carrier and carbon dioxide adsorbent are not shown in the figure.

[0015] The cells S partitioned by the partition wall 12 are open at both ends. (Peripheral wall 11) The components constituting the peripheral wall 11 are not particularly limited and known components can be used, for example, it may be composed of the same components as the partition wall 12.

[0016] The thickness of the peripheral wall 11 is not particularly limited and can be set as appropriate, but for example it may be the same as or thicker than the thickness of the partition wall 12. The thickness of the peripheral wall 11 is preferably, for example, 0.05 mm or more and 0.6 mm or less.

[0017] (Partition Wall 12) As shown in Figures 2(a) and (b), the partition wall 12 has a skeletal portion mainly composed of ceramic and metallic silicon that fills the gaps in the skeletal portion and covers the surface of the skeletal portion.

[0018] The ceramic that constitutes the skeletal portion of the partition wall 12 is not particularly limited and known materials can be used, such as silicon carbide, alumina, cordierite, zirconia, aluminum nitride, silicon nitride, forsterite, steatite, sialon, machinable ceramics, barium titanate, lead zirconate titanate, ferrite, and mullite. Among these, it is preferable that the ceramic be at least one selected from silicon carbide, alumina, and cordierite.

[0019] The average particle diameter of the ceramic particles is not particularly limited and can be set as appropriate, for example, it can be between 0.8 μm and 10 μm. The average particle diameter of the ceramic particles can be measured by observing the cross-section of the honeycomb structure 10 with an electron microscope (acceleration voltage: 10 kV, magnification: 3000x). Specifically, the particle diameter of all ceramic particles in the field of view is measured from three randomly selected electron microscope images, and the average value is taken as the average particle diameter of the ceramic particles.

[0020] Preferably, the skeletal portion is composed of multiple ceramic particles in contact with each other. This suppresses the propagation of cracks when stress is applied to the honeycomb structure 10 and cracks occur in the skeletal portion. The state in which multiple ceramic particles are in contact with each other means a state in which multiple ceramic particles are in contact with each other without being sintered. Furthermore, the cracks in the skeletal portion mean gaps formed by the separation of ceramic particles. In the case of a sintered body in which ceramic particles are sintered, the cracks in the skeletal portion mean gaps formed by the fracture of the sintered parts of the ceramic particles, as well as gaps formed by the fracture of the ceramic particles themselves.

[0021] The metallic silicon constituting the partition wall 12 is not particularly limited, and known materials can be used. Metallic silicon is also called metallic grade silicon. The metallic silicon content in the partition wall 12 is 20% by mass or more and 40% by mass or less. More preferably, the metallic silicon content in the partition wall 12 is 30% by mass or more and 40% by mass or less.

[0022] The metallic silicon content in the partition wall 12 refers to the ratio of the mass of the filled metallic silicon to the mass of the partition wall 12 in the filled state. If the peripheral wall 11 is composed of the same components as the partition wall 12, it is preferable that the metallic silicon content in the peripheral wall 11 is also the same as that of the partition wall 12.

[0023] The metallic silicon content in the partition wall 12 can be calculated, for example, by the following method. First, the partition wall 12 is cut out from the honeycomb structure that has undergone the impregnation process described later. The cut-out partition wall 12 is crushed, and the mass A of the crushed partition wall 12 is measured. Next, the crushed partition wall 12 is treated with hydrofluoric acid to remove the filled metallic silicon. Then, the mass B of the crushed partition wall 12 is measured again. Finally, it can be calculated using the following formula.

[0024] The metallic silicon content (mass%) = ((mass A - mass B) / (mass A)) × 100 By having a metallic silicon content within the above numerical range, the gaps in the skeletal structure can be suitably filled with metallic silicon. Since metallic silicon is a material with high thermal conductivity, the thermal conductivity of the partition wall 12 can be improved. That is, the thermal conductivity of the honeycomb structure 10 can be improved. Furthermore, by having a metallic silicon content of 40 mass% or less, the surface of the partition wall 12 is not excessively covered with metallic silicon, thereby improving the support of the carrier and the carbon dioxide adsorbent supported on the carrier. In addition, it is possible to suppress the excessive covering of the surface of the skeletal structure with metallic silicon, which would make it difficult for fluid to flow inside the cell S.

[0025] The porosity of the honeycomb structure 10 is 15% or less. More preferably, the porosity of the honeycomb structure 10 is 0% or more and 10% or less, even more preferably 5% or less, even more preferably 1% or less, and most preferably 0%. The porosity of the honeycomb structure 10 can be determined by the mercury intrusion method. The measurement conditions in the mercury intrusion method are a contact angle of 130° and a surface tension of 485 mN / m. The test specimen for the mercury intrusion method was cut out from the honeycomb structure 10 so as to include the peripheral wall 11 and the partition wall 12. By having a porosity of 15% or less of the honeycomb structure 10, the waterproofing of the honeycomb structure 10 can be improved. Note that the porosity of the honeycomb structure 10 refers to the percentage of gaps in the skeletal portion of the peripheral wall 11 and partition wall 12 that are not filled with metallic silicon.

[0026] (Carrier) The carrier is not particularly limited and any known material can be used, for example, alumina (Al ２ O ３ ), TiO ２ SiO ２ , ZrO ２ Examples include zeolite and carbon. The method for supporting the support on the surface of the partition wall 12 is not particularly limited, but for example, a suspension in which these materials are dispersed in a dispersion medium is prepared and attached to the surface of the partition wall 12. Furthermore, it can be supported by drying and firing. The support may be a porous material such as polymethyl methacrylate. In addition, the support may be supported not only on the surface of the partition wall 12 but also on the surface of the peripheral wall 11. The firing of the support should be carried out at a temperature lower than the melting point of the metallic silicon.

[0027] (Carbon Dioxide Adsorbent) The carbon dioxide adsorbent is not particularly limited and any known material can be used, such as zeolites, alkali and alkaline earth metal compounds, activated carbon, metal-organic structures, monoethanolamine, diethanolamine, tetraethylenepentamine, pentaethylenehexamine, hexaethyleneheptamine, etc. The carbon dioxide adsorbent is preferably an amine compound. Metal-organic structures (MOFs) refer to materials that have a porous coordination network structure with a much larger surface area than activated carbon or zeolites due to the interaction of metals and organic ligands.

[0028] Specific examples of amine compounds include polyethyleneimine, monoethanolamine, diethanolamine, triethanolamine, tetraethyleneaminepentamine, methyldiethanolamine, dibutylamine, ethylenediamine, diethylenetriamine, triethylenetetramine, hexaethylenediamine, benzylamine, metaxylenediamine, polyethyleneimine, ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, and pentaethylenehexamine.

[0029] The method for supporting the carbon dioxide adsorbent on the support is not particularly limited, but for example, an aqueous solution of these materials, an alcohol solution, or a suspension in which these materials are dispersed in a dispersion medium is prepared. Furthermore, the prepared aqueous solution is applied to the compartment wall 12 on which the support is supported. After that, the carbon dioxide adsorbent can be supported on the support by drying as appropriate. When the carbon dioxide adsorbent is supported on the support, the carbon dioxide adsorbent is positioned on the surface of the compartment wall 12 via the support. In addition, the carbon dioxide adsorbent may be supported not only on the surface of the compartment wall 12 but also on the surface of the peripheral wall 11.

[0030] (Method for manufacturing a honeycomb structure) The honeycomb structure 10 can be manufactured by sequentially following the molding process, impregnation process, carrier support process, and carbon dioxide adsorbent support process described below.

[0031] (Molding Process) As raw materials for molding the honeycomb structure 10, a clay-like mixture containing ceramic particles used in known honeycomb structures, an organic binder, and a dispersion medium is prepared. Using this mixture, a molded body is formed having a peripheral wall 11 and a partition wall 12 having a honeycomb cross-section that divides the interior of the peripheral wall 11 into a plurality of cells S extending in the axial direction of the peripheral wall 11. The molding method of the molded body is not particularly limited, but for example, it can be molded by extrusion molding. The obtained molded body may be subjected to a drying treatment to dry the molded body.

[0032] (Impregnation Process) The impregnation process is a process of impregnating the interior of the partition walls 12 of the molded body with metallic silicon. In the impregnation process, a lump of metallic silicon is placed near the molded body and heated to a temperature above the melting point of metallic silicon (for example, 1450°C or higher). The lump of metallic silicon may be in direct contact with the molded body or in contact with it via a medium. As a result, the molten metallic silicon enters the gaps between the ceramic particles constituting the partition walls 12 of the molded body by capillary action, and the metallic silicon is impregnated into these gaps.

[0033] (Supporting process for the support body) The supporting process for the support body is the process of supporting the support body on the honeycomb structure that has undergone the impregnation process. In the supporting process for the support body, first, a suspension is prepared in which the material to be used for the support body is dispersed in a dispersion medium. Next, the prepared suspension is attached to the surface of the partition wall 12. Furthermore, the support body can be supported by drying and firing.

[0034] (Carbon Dioxide Adsorbent Supporting Process) The carbon dioxide adsorbent supporting process involves supporting the carbon dioxide adsorbent on a honeycomb structure on which the support is attached. In the carbon dioxide adsorbent supporting process, first, an aqueous solution, an alcohol solution, or a suspension in which these materials are dispersed in a dispersion medium is prepared using the material used for the carbon dioxide adsorbent. Next, the prepared aqueous solution, etc., is applied to the surface of the compartment wall 12 on which the support is attached. Furthermore, the carbon dioxide adsorbent can be supported by drying as appropriate.

[0035] Through the above steps, a honeycomb structure 10 is obtained, which comprises a peripheral wall 11, partition walls 12 that partition the interior of the peripheral wall 11 into a plurality of cells S extending in the axial direction of the peripheral wall 11, a support carried on the surface of the partition walls 12, and a carbon dioxide adsorbent carried on the support. The partition walls 12 have a skeleton portion mainly composed of ceramic, and metallic silicon filled in gaps of the skeleton portion and covering the surface of the skeleton portion. The skeleton portion is configured with a plurality of ceramic particles in a state of being in contact with each other.

[0036] In the method for manufacturing the honeycomb structure 10, the following degreasing step, firing step, and surface oxidation step may be performed between the above-mentioned forming step and impregnation step. (Degreasing step) The degreasing step is a step of heating the formed body to burn and burn off the organic binder contained in the formed body, thereby obtaining a degreased body from which the organic binder has been removed from the formed body. Through the degreasing step, the organic binder and the dispersion medium are removed from the formed body, so that the ceramic particles are in contact with each other, and a degreased body having gaps between the ceramic particles is obtained.

[0037] (Firing step) The firing step is a step of sintering ceramic particles together by firing the degreased body obtained in the degreasing step at 1800 to 2200°C for 0.5 to 4 hours under an inert gas atmosphere such as a nitrogen atmosphere or an argon atmosphere. By performing the firing step, the skeleton portion of the honeycomb structure becomes a sintered body obtained by sintering ceramic particles. Further, by performing the above-mentioned impregnation step, gaps in the skeleton portion are filled with metallic silicon, and the surface of the skeleton portion is covered with metallic silicon. (Surface oxidation step) The surface oxidation step is to form a thin SiO ２ oxide film on the surface layer of the honeycomb structure impregnated with metallic silicon in an oxidizing atmosphere. In the surface oxidation step, for example, holding at 300 to 1500°C in the atmosphere for 30 minutes to 10 hours can form a thin SiO ２ oxide film. By forming a thin SiO ２ oxide film, the adhesive force of the support and the carbon dioxide adsorbent can be strengthened. The formed SiO ２The film thickness is not particularly limited, but is preferably, for example, 0.1 to 1000 nm.

[0038] (Use of Honeycomb Structure) The honeycomb structure 10 of the present embodiment can be used for applications of recovering carbon dioxide. That is, it can be used as a carbon dioxide adsorption structure in a carbon dioxide recovery apparatus. Specifically, inside the peripheral wall 11 of the honeycomb structure 10, the partition walls 12 carrying the carbon dioxide adsorbent can be used as a reaction layer for performing adsorption and desorption of carbon dioxide. Furthermore, the outside of the peripheral wall 11 of the honeycomb structure 10 can be used as a heating layer through which water as a heat exchanger for heating the reaction layer circulates.

[0039] <Actions and Effects of the Embodiment> Actions and effects of the present embodiment will be described. (1) The honeycomb structure 10 includes a peripheral wall 11, partition walls 12 that partition the inside of the peripheral wall 11 into a plurality of cells S extending in the axial direction of the peripheral wall 11, a carrier carried on the surfaces of the partition walls 12, and a carbon dioxide adsorbent carried on the carrier. The partition walls 12 have a skeleton portion containing ceramic as a main component, and metallic silicon that fills gaps in the skeleton portion and covers the surface of the skeleton portion. The content of metallic silicon in the partition walls 12 is 20% by mass or more and 40% by mass or less. The porosity of the honeycomb structure is 15% or less.

[0040] According to this configuration, the honeycomb structure 10 can exhibit excellent water resistance and thermal conductivity. Therefore, when recovering carbon dioxide using the honeycomb structure 10, for example, water can be used as the heat exchange medium. Since water is inexpensive as a heat exchange medium, carbon dioxide can be recovered efficiently at low cost.

[0041] (2) The ceramic is at least one selected from silicon carbide, alumina, and cordierite. According to this configuration, the heat resistance of the partition walls 12 can be further improved. (3) The thickness of the partition walls 12 is 0.05 mm or more and 0.6 mm or less. According to this configuration, both sufficient water resistance and thermal conductivity can be exhibited.

[0042] (4) The carbon dioxide adsorbent is an amine compound. According to this configuration, carbon dioxide can be recovered by a chemical reaction between the amine compound and carbon dioxide. In this case, since the amine compound is disposed on the surface of the partition walls 12, the contact area with carbon dioxide can be increased, and carbon dioxide can be recovered efficiently.

[0043] (5) The skeleton portion is formed in a state where a plurality of ceramic particles are in contact with each other. According to this configuration, when stress is applied to the honeycomb structure and a crack occurs in the skeleton portion, propagation of the crack can be suppressed.

[0044] <Modified Example> The present embodiment can be implemented with the following modifications. The present embodiment and the following modified examples can be implemented in combination with each other within a technically consistent range.

[0045] - The cross-sectional shape of the cells S partitioned by the partition walls 12 of the honeycomb structure 10 is not limited to a quadrilateral, and may be a polygonal shape. For example, the cross-sectional shape of the cells S may be triangular, quadrilateral, hexagonal, octagonal, or a combination thereof.

[0046] - The outer shape of the honeycomb structure 10 is not limited to a prismatic shape, and may be a cylindrical shape, an elliptical cylindrical shape, or a fan-shaped prismatic outer shape. Further, the honeycomb structure 10 may be formed by joining a plurality of honeycomb structures 10 such that the overall shape thereof is a prismatic shape, a cylindrical shape, or the like. The method for joining the plurality of honeycomb structures 10 is not particularly limited, and for example, joining can be performed by using a known adhesive or the above-mentioned metallic silicon. Further, for the honeycomb structure 10, any shape can be cut out from a prismatic honeycomb structure, for example. Specifically, for example, by grinding the outer periphery of a prismatic honeycomb structure, any outer shape such as the above-mentioned cylindrical shape can be obtained.

[0047] In this embodiment, the peripheral wall 11 of the honeycomb structure 10, like the partition wall 12, had a skeletal portion mainly composed of ceramic and metallic silicon that filled the gaps in the skeletal portion and covered the surface of the skeletal portion, but is not limited to this embodiment. The peripheral wall 11 may be composed of other materials. Examples of other materials include known cements. Even with known cements, it is preferable that the porosity is 15% or less.

[0048] In this embodiment, the skeletal portion of the honeycomb structure was composed of multiple ceramic particles in contact with each other, but the embodiment is not limited to this. The skeletal portion of the honeycomb structure may be composed of a sintered body made of sintered ceramic particles. If it is composed of a sintered body made of sintered ceramic particles, the strength of the honeycomb structure 10 can be improved.

[0049] The following describes examples that further elaborate on the above embodiments. (Example 1) First, a mixture with the following composition was prepared.

[0050] The mixture consisted of: 58.3 parts by mass of silicon carbide particles with an average particle size of 10 μm (large particles), 21.6 parts by mass of silicon carbide particles with an average particle size of 0.5 μm (small particles), 4.5 parts by mass of methylcellulose (organic binder), 2.1 parts by mass of polyoxyalkylene compound (plasticizer), and 13.5 parts by mass of water (dispersion medium). Using this mixture, a prismatic molded body having a honeycomb structure with dimensions of 35 mm × 35 mm × 300 mm, a peripheral wall thickness of 0.3 mm, a partition wall thickness of 0.1 mm, and a cell width of 0.92 mm was formed. Next, a 35.2 g lump of metallic silicon was placed in contact with the molded body, and under vacuum, it was heated at 450°C for 1.0 hour, then at 1350°C for 2.0 hours, and then at 1550°C for 1.0 hour to obtain the honeycomb structure of Example 1, in which metallic silicon was melted and impregnated. The metallic silicon content of the honeycomb structure in Example 1 was 34.0% by mass, and the porosity of the honeycomb structure was 0%.

[0051] Subsequently, SiO is used as a carrier in the honeycomb structure. ２Monoethanolamine was supported as a carbon dioxide adsorbent. (Example 2) A molded body was obtained in the same manner as in Example 1. Next, a degreased body was obtained by heating the molded body at 370°C for 2.5 hours to remove the organic binder. Then, a calcined body was obtained by heating the degreased body in an argon atmosphere at 2150°C for 2.5 hours. Then, a maximum of 27 g of metallic silicon was placed in contact with the calcined body, and the honeycomb structure of Example 2 was obtained by heating under vacuum at 1550°C for 1.0 hour to melt and impregnate the metallic silicon. The metallic silicon content of the honeycomb structure of Example 2 was 22.8% by mass, and the porosity of the honeycomb structure was 11.2%.

[0052] Subsequently, the same support and carbon dioxide adsorbent as in Example 1 were supported on the honeycomb structure. (Comparative Example 1) A honeycomb structure of Comparative Example 1 was obtained by melting and impregnating metallic silicon in the same manner as in Example 1, except that 22.7 g of metallic silicon was used near the molded body. The metallic silicon content of the honeycomb structure of Comparative Example 1 was 19.4% by mass, and the porosity of the honeycomb structure was 15.6%.

[0053] Subsequently, the same carrier and carbon dioxide adsorbent as in Example 1 were supported on the honeycomb structure. (Waterproof Test) The following waterproof tests were performed on the honeycomb structures of Examples 1 and 2 and Comparative Example 1. The honeycomb structures used in the waterproof tests were those before the carrier and carbon dioxide adsorbent were supported.

[0054] As shown in Figure 3(a), the ends of the honeycomb structures in Examples 1 and 2 and Comparative Example 1 were sealed by joining the end faces of the honeycomb structures to the rubber caps 20. A hose 30 was later joined to one of the rubber caps 20 to introduce air. The inside of the hose 30 and one end of the honeycomb structure are in communication within the rubber cap 20. Therefore, air from inside the hose 30 can be introduced into the honeycomb structure from one end of the honeycomb structure.

[0055] Next, as shown in Figure 3(b), both ends of the rubber cap 20 were fixed to the support 50 using bolts 40. Then, as shown in Figure 3(c), the rubber cap 20 and the end face of the honeycomb structure were placed in the water tank 60, ensuring that one end of the rubber cap 20 and the end face of the honeycomb structure were not submerged in water. In this state, a pipe was connected to the hose 30 and air was introduced. When the internal pressure reached 100 kPa or higher, the presence or absence of bubbles from the surface of the honeycomb structure was visually checked and the results are shown as present / absent in the "Bubbles" column of Table 1.

[0056] (Evaluation) As shown in Table 1, the honeycomb structures of Examples 1 and 2 were found to have excellent waterproofing properties.

[0057] 10...Honeycomb structure, 11...Surrounding wall, 12...Partition wall.

Claims

1. A honeycomb structure comprising a peripheral wall, a partition wall that divides the interior of the peripheral wall into a plurality of cells extending in the axial direction of the peripheral wall, a carrier supported on the surface of the partition wall, and a carbon dioxide adsorbent supported on the carrier, wherein the partition wall has a skeletal portion mainly composed of ceramic and metallic silicon that fills the gaps in the skeletal portion and covers the surface of the skeletal portion, the content of the metallic silicon in the partition wall is 20% by mass or more and 40% by mass or less, and the porosity of the honeycomb structure is 15% or less.

2. The honeycomb structure according to claim 1, wherein the ceramic is at least one selected from silicon carbide, alumina, and cordierite.

3. The honeycomb structure according to claim 1, wherein the thickness of the partition wall is 0.05 mm or more and 0.6 mm or less.

4. The honeycomb structure according to claim 1, wherein the carbon dioxide adsorbent is an amine compound.

5. The honeycomb structure according to claim 1, wherein the skeletal portion is composed of a plurality of ceramic particles in contact with each other.

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