Honeycomb structure and direct air capture device

Abstract

Provided is a honeycomb structure to be used for a direct air capture (DAC) application, the honeycomb structure comprising: a partition wall forming in a partitioning manner a plurality of through-holes serving as a flow passage of air including CO2; an outer peripheral wall provided on the outer periphery; and a CO2 adsorbent carried on the surface of the partition wall. The partition wall and the outer peripheral wall are made of silicon carbide, and have an opening ratio of 65-86%. The surface area of the partition wall is 20-36 cm2 per 1 cm3 of the honeycomb structure. By heating the surface of the outer peripheral wall, CO2 adsorbed to the CO2 adsorbent is desorbed and CO2 in the air is captured.

Description

Honeycomb structure and direct air recovery device

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

[0002] Carbon dioxide (CO ２ It is widely known that concentrations of chlorofluorocarbons (C1, C2, C4, C6, C8) show a strong correlation with global warming, which leads to rising atmospheric temperatures and an increased chance of natural disasters such as typhoons and floods.

[0003] Patent Document 1 describes the CO in the air ２ Direct Air Capture (DAC) is a method for removing CO2 from an adsorbent such as an amine. ２ In order to adsorb and desorb CO, the number of adsorption and desorption cycles is increased to efficiently remove CO from the air per volume. ２ It is desired to remove

[0004] In Patent Document 1, CO is removed by heating the adsorbent mainly using low-pressure steam. ２ In addition, Patent Document 2 discloses a method for desorbing CO by DAC. ２ CO generated from generators and plants, etc. ２ CO2 recovery in mind ２ The publication describes a recovery device in which a reaction layer and a heating layer are stacked, and the reaction layer is heated by injecting steam into the heating layer to recover CO ２ This causes the molecules to separate.

[0005] JP 2023-520609 A JP 2022-067481 A

[0006] CO ２ In recovering CO in exhaust gas from a power generator or plant, as in the technology of Patent Document 2, ２ When recovering CO, there is a heat medium (exhaust heat) nearby, so steam can be used to recover CO. ２ On the other hand, CO in the air can be desorbed like in DAC. ２ When removing CO from the atmosphere, there is no heat medium nearby, making it difficult to heat using steam. In addition, in the technology described in Patent Document 1, steam is directly introduced into the carbon dioxide capture structure, so steam gets mixed into the captured gas, and the CO in the captured gas is reduced.２ In this case, a separate device is required to remove the vapor from the recovered gas.

[0007] In light of this, the present inventors have investigated ways to prevent steam from being mixed into the collected gas by heating the surface of the outer wall of the structure, rather than by injecting steam into the structure. In the process, they have found that the structure needs to be designed to be suitable for heating from the surface of the outer wall.

[0008] The present invention has been made in consideration of the above-mentioned problems, and aims to provide a honeycomb structure to be used in a DAC, which has a structure suitable for heating from the surface of the outer wall.

[0009] The honeycomb structure of the present invention is ２ a partition wall defining a plurality of through holes that serve as a flow path for air containing CO; an outer peripheral wall provided on the outer periphery; and ２ an adsorbent, wherein the partition walls and the outer peripheral wall are made of silicon carbide, the opening ratio is 65 to 86%, and the surface area of ​​the partition walls is 1 cm 2 of the honeycomb structure. ３ 20-36cm per ２ and by heating from the surface of the outer peripheral wall, ２ CO adsorbed on the adsorbent ２ CO in the air is desorbed ２ The honeycomb structure is used in direct air capture (DAC) applications.

[0010] The honeycomb structure of the present invention is used for direct air recovery (DAC) applications. When the partition walls and outer peripheral wall of the honeycomb structure are made of silicon carbide, the time required for the temperature to rise from the surface of the outer peripheral wall to the center of the honeycomb structure can be shortened compared to other ceramic honeycomb structures that can also be used for DAC applications, since silicon carbide has high thermal conductivity. The shorter the temperature rise time, the shorter the CO ２ When the adsorption amount of CO is the same, ２ This means that the number of adsorption and desorption cycles of CO can be increased, and when used for DAC applications, CO２ This results in a honeycomb structure that can recover the above.

[0011] In addition, the opening ratio of the honeycomb structure and the surface area of ​​the partition walls are set within appropriate ranges. With these specifications, the heat capacity of the honeycomb structure falls within an appropriate range, and the temperature drop time is shortened. Therefore, when the adsorption amount is the same, the CO ２ The number of cycles of CO adsorption and desorption can be increased. ２ From this viewpoint, the honeycomb structure of the present invention is a honeycomb structure for DAC that is suitable for heating from the surface of the outer wall.

[0012] In the honeycomb structure of the present invention, it is preferable that the heating from the surface of the outer wall is performed by an electric heater. By using the electric heater, the honeycomb structure can be heated from the surface of the outer wall even when there is no heat medium nearby.

[0013] In the honeycomb structure of the present invention, it is preferable that the heated area of ​​the surface of the outer wall is 50% or more. When the heated area is as wide as 50% or more, the temperature of the entire honeycomb structure can be raised more quickly, and the time for one cycle can be shortened.

[0014] In the honeycomb structure of the present invention, ２ The adsorbent is preferably at least one selected from the group consisting of amines, zeolites, and MOFs (metal organic frameworks). ２ The adsorbent is CO ２ It can be suitably used for adsorption and desorption of

[0015] The cross-sectional area of ​​the honeycomb structure of the present invention perpendicular to the longitudinal direction, which is the direction in which the through holes extend, is 100 to 400 cm ２ It is preferable that the length of the honeycomb structure of the present invention in the longitudinal direction, which is the direction in which the through holes extend, is 100 to 500 mm. ２ If it is smaller, the volume of the honeycomb structure per DAC device will be smaller, so CO ２The amount of adsorption may be reduced. ２ If the length exceeds 100 mm, the central part of the honeycomb structure is difficult to heat, and the time required for the temperature rise of the entire honeycomb structure may become long. ２ If the length exceeds 500 mm, the pressure loss when air flows through the through-holes may become large. The preferred dimensions of the honeycomb structure are as described above, and a honeycomb structure having the above dimensions can be suitably used for DAC applications.

[0016] The direct air recovery (DAC) device of the present invention comprises: the honeycomb structure of the present invention; a heater provided on the surface of the outer wall of the honeycomb structure; and a CO 2 desorbed from the honeycomb structure. ２ The DAC device of the present invention heats the surface of the outer wall of the honeycomb structure by the heater, and can generate CO even when there is no heat medium nearby. ２ The honeycomb structure has a material and structure suitable for heating from the surface of the outer wall, so CO can be efficiently desorbed by the DAC. ２ can be recovered.

[0017] Fig. 1 is a perspective view schematically showing an example of a honeycomb structure. Fig. 2 is a perspective view schematically showing a state in which an electric heater is provided on the surface of the outer wall of the honeycomb structure. Fig. 3 is a front view of the honeycomb structure for explaining the range of the heated area on the surface of the outer wall of the honeycomb structure. Fig. 4 is a perspective view schematically showing a state in which a plurality of honeycomb structures are combined and arranged in a casing. Fig. 5 is a schematic view schematically showing the configuration of a DAC device.

[0018] (Detailed Description of the Invention) Hereinafter, the honeycomb structure of the present invention will be described. ２ a partition wall defining a plurality of through holes that serve as a flow path for air containing CO; an outer peripheral wall provided on the outer periphery; and ２an adsorbent, wherein the partition walls and the outer peripheral wall are made of silicon carbide, the opening ratio is 65 to 86%, and the surface area of ​​the partition walls is 1 cm 2 of the honeycomb structure. ３ 20-36cm per ２ and by heating from the surface of the outer peripheral wall, ２ CO adsorbed on the adsorbent ２ CO in the air is desorbed ２ The honeycomb structure is used in direct air capture (DAC) applications.

[0019] The honeycomb structure of the present invention is used in direct air capture (DAC) applications. DAC is a process for converting CO into CO , such as CO , from exhaust gases from factories. ２ CO from high concentration gas ２ Unlike technologies that capture CO from the atmosphere (air), ２ This technology captures CO from the atmosphere. ２ The concentration is said to be about 0.04% (400 ppm), and DAC is CO ２ CO from the atmosphere at concentrations between 0.01% and 0.1% ２ This technology can be said to recover

[0020] DAC uses CO in the air ２ CO ２ Adsorbed onto the adsorbent. ２ The adsorbent may be at least one selected from the group consisting of amines, zeolites, and MOFs (metal organic frameworks). ２ The adsorbent is ２ It has adsorption ability and adsorbed CO ２ It has the property of releasing when heated.

[0021] Examples of amines include polyethyleneimine, monoethanolamine, diethanolamine, triethanolamine, tetraethyleneaminepentamine, methyldiethanolamine, dibutylamine, ethylenediamine, diethylenetriamine, triethylenetetramine, hexaethylenediamine, benzylamine, metaxylenediamine, polyethyleneimine, ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, and pentaethylenehexamine.

[0022] Examples of zeolites include LTA type, FAU type, CHA type, DDR type, and AFI type. Examples of MOFs (metal organic frameworks) include Co-substituted MOFs and Zn-substituted MOFs.

[0023] The honeycomb structure of the present invention is ２ a partition wall defining a plurality of through holes that serve as a flow path for air containing CO; an outer peripheral wall provided on the outer periphery; and ２ Fig. 1 is a perspective view showing a typical example of a honeycomb structure. The honeycomb structure 20 shown in Fig. 1 has a shape in which a plurality of through holes 21 are arranged in parallel in the longitudinal direction (the direction indicated by the double-headed arrow f in Fig. 1) with partition walls 22 between them, and an outer peripheral wall 23 is provided on the periphery. The through holes 21 are ２ The surface of the partition wall 22 serves as a flow path for air containing CO ２ The adsorbent is supported. ２ The adsorbent may be any of the above-mentioned materials.

[0024] CO ２ During the adsorption of CO 2 in the air that has flowed into the through-hole 21 from the gas inlet end 21 a of the through-hole 21 ２ However, the CO supported on the surface of the partition wall 22 ２ The CO 2 is adsorbed by the adsorbent. ２ The air with reduced concentration flows out from the gas outflow end 21 b of the through-hole 21 .

[0025] CO ２ When recovering the CO , the honeycomb structure 20 is heated from the surface of the outer wall 23. ２ CO adsorbed on the adsorbent２ By desorbing CO ２ The desorbed CO is recovered. ２ The gas containing a high concentration of CO is discharged from the gas outlet end 21b of the through-hole 21. ２ It can be collected by storing it in a container such as a cylinder.

[0026] The partition walls and outer wall of the honeycomb structure are made of silicon carbide. Silicon carbide has a high thermal conductivity of 190 W / mK. Therefore, compared to other ceramic honeycomb structures that can be used for DAC applications, the time required for the temperature to rise from the surface of the outer wall to the center of the honeycomb structure can be shortened. The short temperature rise time means that the CO ２ When the adsorption amount of CO is the same, ２ This means that the number of adsorption and desorption cycles of CO can be increased, and when used for DAC applications, CO ２ The partition walls and the outer peripheral wall being made of silicon carbide means that the main component of the partition walls and the outer peripheral wall is silicon carbide, but does not mean that the partition walls and the outer peripheral wall are made of silicon carbide only. For example, a composite of silicon carbide and metal silicon, silicon-containing silicon carbide, or silicon carbide bonded with metal silicon is also included.

[0027] In addition, when used for DAC applications, ２ In order to obtain a honeycomb structure that can recover the above-mentioned waste, the opening ratio of the honeycomb structure and the surface area of ​​the partition walls are set to appropriate ranges. The opening ratio of the honeycomb structure is 65 to 86%. It is also preferable that it is 68 to 80%. The surface area of ​​the partition walls is set to 1 cm per 1 cm of the honeycomb structure. ３ 20-36cm per ２ Also, 23 to 30 cm ２ The opening ratio and surface area of ​​the partition walls can be calculated from the cell structure (thickness of the partition walls, cell density) of the honeycomb structure. When the opening ratio and surface area of ​​the partition walls of the honeycomb structure are set within such ranges, the heat capacity of the honeycomb structure falls within an appropriate range, and the temperature drop time is shortened. Therefore, when the adsorption amount is the same, the CO ２The number of cycles of CO adsorption and desorption can be increased. ２ A large amount of adsorbent can be supported.

[0028] The partition walls and the outer peripheral wall are preferably porous, and the porosity thereof is preferably 30 to 70%. Furthermore, the porosity is more preferably 35 to 50%. By setting the porosity of the partition walls and the outer peripheral wall within the above range, the time required for heating and cooling the honeycomb structure can be shortened while maintaining the strength of the honeycomb structure. The porosity of the partition walls and the outer peripheral wall can be measured by mercury porosimetry under conditions of a contact angle of 130° and a surface tension of 485 mN / m.

[0029] The specific heat of the partition walls and the outer peripheral wall as porous ceramic is preferably 0.5 to 0.8 J / g K, and more preferably 0.6 to 0.7 J / g K. The specific heat of the partition walls and the outer peripheral wall can be measured by cutting out the partition wall or outer peripheral wall portion and subjecting it to DSC (differential scanning calorimetry) using a PerkinElmer DSC8000 at a measurement temperature of 25°C, a temperature rise rate of 20°C / m, and a nitrogen atmosphere using sapphire as a reference sample.

[0030] The density of the partition walls and the outer peripheral wall as porous ceramic is preferably 1.7 to 2.0 g / cc, and more preferably 1.8 to 1.9 g / cc. The density of the partition walls and the outer peripheral wall can be measured by cutting out a portion of the partition walls or the outer peripheral wall and subjecting it to Archimedes' method.

[0031] The thermal conductivity of the partition walls and the outer peripheral wall as porous ceramic is preferably 10 to 50 W / mK, and more preferably 15 to 40 W / mK. The thermal conductivity of the partition walls and the outer peripheral wall can be calculated by the formula: Thermal Conductivity = Specific Heat × Density × Thermal Diffusivity. The thermal diffusivity can be measured by a flash method at room temperature in a nitrogen atmosphere using an LFA467 manufactured by NETZSCH, and determined by analysis including pulse width correction and heat loss correction.

[0032] The cross-sectional area of ​​the honeycomb structure perpendicular to the longitudinal direction, which is the direction in which the through holes extend, is 100 to 400 cm ２The cross-sectional area is the sum of the area of ​​the partition walls, the area of ​​the outer peripheral wall, and the area of ​​the through-holes in the cross section. The length of the honeycomb structure in the longitudinal direction, which is the direction in which the through-holes extend, is preferably 100 to 500 mm. ２ If it is smaller, the volume of the honeycomb structure per DAC device will be smaller, so CO ２ The amount of adsorption may be reduced. ２ If the length exceeds 100 mm, the central part of the honeycomb structure is difficult to heat, and the time required for the temperature rise of the entire honeycomb structure may become long. ２ If the length exceeds 500 mm, the pressure loss when air flows through the through holes may become large.

[0033] The partition walls of the honeycomb structure desirably have a uniform thickness. The partition wall thickness of the honeycomb structure is preferably 0.1 to 1.0 mm, and more preferably 0.15 to 0.5 mm. The thickness of the peripheral wall of the honeycomb structure may be the same as or thicker than the partition wall thickness.

[0034] The through-hole density in the cross section perpendicular to the longitudinal direction of the honeycomb structure is 31 to 155 pcs / cm ２ (200-1000 pieces / inch ２ ) is preferably 46.5 to 124 particles / cm ２ (300-800 pieces / inch ２ ) is more preferred.

[0035] The honeycomb structure of the present invention is used for DAC by heating from the surface of the outer wall. That is, the heating method of the honeycomb structure is not a method of circulating high-temperature steam through the through holes to heat the partition walls. When the honeycomb structure is heated from the surface of the outer wall, CO ２ When recovering CO, the time required for temperature rise from the surface of the outer wall to the center of the honeycomb structure is short. ２ If the cooling time of the entire honeycomb structure after the recovery of CO is short, ２ This means that the number of adsorption and desorption cycles of CO can be increased, and when used for DAC applications, CO ２This results in a honeycomb structure that can recover the above.

[0036] It is preferable that the heating from the surface of the outer peripheral wall is performed by a heater. It is also preferable that the heating from the surface of the outer peripheral wall is performed by an electric heater. The electric heater is an electric heating wire provided on the surface of the outer peripheral wall of the honeycomb structure. Figure 2 is a perspective view that schematically shows a state in which an electric heater is provided on the surface of the outer peripheral wall of a honeycomb structure. Figure 2 shows a state in which an electric heater 30 is provided on the surface of the outer peripheral wall 23 of the honeycomb structure 20 shown in Figure 1. The electric heater 30 consists of an electric heating wire 31 and electrodes 32 provided on both ends of the electric heating wire 31.

[0037] Of the surfaces of the honeycomb structure, the two surfaces where the through holes are exposed are called end surfaces, and the other four surfaces are called side surfaces. Electric heaters are provided on the side surfaces of the honeycomb structure. Figure 2 shows how electric heaters 30 are provided on all four side surfaces of the honeycomb structure 20. In Figure 2, the dotted lines indicate that electric heaters 30 are also provided on side surfaces that are located on the back side and cannot be seen directly.

[0038] Furthermore, an electric heater may be provided on some of the side surfaces of the honeycomb structure. When a plurality of honeycomb structures are used in combination as described below, if one electric heater is provided between two adjacent honeycomb structures, the two adjacent honeycomb structures can be heated by one electric heater. Therefore, when viewed as a single honeycomb structure, there may be a side surface on which an electric heater is not provided. Nichrome wire or the like can be used as the electric heating wire. Heaters other than electric heaters include far-infrared heaters and oil heaters.

[0039] It is also preferable that the heated area of ​​the surface of the peripheral wall of the honeycomb structure is 50% or more. Fig. 3 is a front view of a honeycomb structure for explaining the heated area of ​​the surface of the peripheral wall of the honeycomb structure. In Fig. 3, the area S1 where the electric heater is provided is hatched. The areas S2 (two locations) where no electric heater is provided are not hatched. The area S1 where the electric heater is provided is defined as a rectangular area including all parts heated by the electric heating wire.

[0040] The area of ​​the surface of the peripheral wall of the honeycomb structure (the side surface of the honeycomb structure) is the sum of the areas of region S1 and region S2 (two locations), and the ratio (%) of the area of ​​region S1 to the area of ​​the surface of the peripheral wall of the honeycomb structure is defined as the range of the heated area of ​​the surface of the peripheral wall of the honeycomb structure. This range is preferably 50% or more. If the range of the heated area is as wide as 50% or more, the temperature of the entire honeycomb structure can be raised more quickly, and the time for one cycle can be shortened.

[0041] The direct air recovery (DAC) device of the present invention comprises the honeycomb structure of the present invention, a heater provided on the surface of the outer wall of the honeycomb structure, and a CO 2 desorbed from the honeycomb structure. ２ and a container for storing the

[0042] A plurality of honeycomb structures can be combined and used in a DAC device. FIG. 4 is a perspective view that schematically shows a state in which a plurality of honeycomb structures are combined and arranged in a casing. FIG. 4 shows a state in which a total of nine honeycomb structures 20 are arranged in a casing 40, three vertically and three horizontally. An electric heater is provided between the side surfaces of adjacent honeycomb structures. As described above, when a plurality of honeycomb structures are combined and used, it is sufficient that one electric heater is provided between two adjacent honeycomb structures. The side surfaces of adjacent honeycomb structures may or may not be bonded with an adhesive or the like.

[0043] A metal casing, such as a casing made of SUS, can be used as the casing 40. The number of honeycomb structures disposed in one casing is not limited, and can be 9 to 400.

[0044] Fig. 5 is a schematic diagram showing the configuration of a DAC device. In the DAC device 100 shown in Fig. 5, an inlet pipe 51 for introducing atmospheric air and an outlet pipe 52 for discharging gas into the atmosphere are connected to a casing 40 in which a honeycomb structure 20 is disposed. A valve 61 is provided in the inlet pipe 51, and a valve 62 is provided in the outlet pipe 52. By opening and closing the valves 61 and 62, the inflow of atmospheric air into the honeycomb structure 20 and the outflow of gas from the honeycomb structure 20 can be controlled. In addition, a fan 72 provided in the outlet pipe 52 may be driven to facilitate the flow of gas from the inlet pipe 51 through the honeycomb structure 20 to the outlet pipe 52.

[0045] The casing 40 contains CO desorbed from the honeycomb structure 20. ２ A container containing CO ２ The storage container 70 is ２ The CO is connected via a receiving pipe 53. ２ The storage container 70 is a CO ２ A CO cylinder can be used. ２ The containing pipe 53 is provided with a valve 63, and ２ The containing pipe 53 and CO ２ A vacuum pump 64 is provided between the container 70 and the honeycomb structure 20. By opening and closing the valve 63 and turning on and off the vacuum pump 64, CO 2 is removed from the honeycomb structure 20. ２ CO ２ It is possible to control the outflow of gas containing CO ２ If you use it directly, the place where you use it is CO ２ Since it has the same function as the storage vessel 70, it is included. For example, ２ By introducing CO into greenhouses, crops can be grown at higher concentrations than usual, increasing crop yields. ２This may be applied to a technology for synthesizing methane by reacting the above with hydrogen in a synthesis vessel.

[0046] The procedure for direct air recovery in the DAC device 100 will be described. First, with the valves 61 and 62 open and the valve 63 closed, atmospheric air is introduced into the through-holes of the honeycomb structure 20 from the inlet pipe 51, and CO ２ The CO supported on the partition walls of the honeycomb structure 20 ２ The amount of CO2 is greater than that of the air flowing into the honeycomb structure 20. ２ The gas with reduced concentration flows out from the through holes of the honeycomb structure 20 to the outflow pipe 52 and is released into the atmosphere.

[0047] CO ２ Adsorbent is sufficiently CO ２ After the CO is adsorbed, the valves 61 and 62 are closed, the valve 63 is opened, the vacuum pump 64 is started, the heater provided on the surface of the outer peripheral wall of the honeycomb structure 20 is driven, and the honeycomb structure 20 is heated from the surface of the outer peripheral wall. ２ CO from the adsorbent ２ 5 shows only one electrode 32 of the electric heater and one power source 33 connected to the electrode. As described above, an electric heater may be provided on each surface of the outer wall of the honeycomb structure. ２ CO desorbed from the adsorbent ２ is CO ２ CO ２ The CO in the atmosphere is stored in the storage container 70. ２ will be collected.

[0048] Heating by the heater is ２ The temperature of the adsorbent is ２ and ２ It is preferable to control the heater output so that the temperature is such that the adsorbent is not deactivated. ２ The appropriate heating temperature varies depending on the type of adsorbent, but is preferably about 70 to 120°C, for example.

[0049] CO ２ CO from the adsorbent ２Once desorption of CO has progressed, heating by the heater is stopped. ２ CO from the adsorbent ２ When CO is sufficiently desorbed, the valves 61 and 62 are opened, and the valve 63 is closed, and the atmospheric CO ２ The CO supported on the partition walls of the honeycomb structure 20 ２ By repeating the above steps, direct air recovery in the DAC device 100 can be performed.

[0050] An example of a method for manufacturing a honeycomb structure of the present invention will be described.

[0051] The molding process involves extrusion molding a wet mixture containing silicon carbide powder and a binder to produce a honeycomb molded body. Specifically, silicon carbide powders having different average particle sizes, an organic binder, a liquid plasticizer, a lubricant, and water are mixed together to prepare a wet mixture for manufacturing the honeycomb molded body.

[0052] If necessary, the wet mixture may contain balloons, which are micro-hollow spheres containing oxide ceramic as a component, spherical acrylic particles, graphite, or other pore-forming agents. The balloons are not particularly limited, and examples thereof include alumina balloons, glass microballoons, shirasu balloons, fly ash balloons (FA balloons), and mullite balloons. Of these, alumina balloons are preferred.

[0053] Next, the wet mixture is put into an extrusion molding machine and extrusion-molded to produce a honeycomb molded body of a predetermined shape. At this time, the honeycomb molded body is produced using a mold that produces a cross-sectional shape having the through-hole structure (shape and arrangement of the through-holes) shown in Figure 1.

[0054] The honeycomb molded body is cut to a predetermined length and dried using a microwave dryer, hot air dryer, dielectric dryer, reduced pressure dryer, vacuum dryer, freeze dryer or the like.

[0055] The honeycomb formed body is heated to 300 to 650°C in a degreasing furnace to perform a degreasing process to remove organic matter from the honeycomb formed body, and then the degreasing honeycomb formed body is transported to a firing furnace and subjected to a firing process in which it is heated to 2000 to 2200°C, thereby obtaining a honeycomb structure.

[0056] Next, CO ２ The adsorbent is supported. ２ The adsorbent is loaded with CO ２ This can be done by immersing the honeycomb structure in a solution containing the adsorbent. ２ The adsorbent is attached, and CO ２ By supporting the support material with the adsorbent attached on the honeycomb structure, ２ The support may be made of silica or alumina.

[0057] When a heater is provided on the surface of the outer wall of the honeycomb structure, a method of printing a conductive paste on the surface of the outer wall of the honeycomb structure so as to form a pattern of heating wires can be used. Alternatively, a method of attaching a metal wire, which has been previously prepared to form a predetermined pattern, to the surface of the outer wall of the honeycomb structure with a heat-resistant adhesive can also be used.

[0058] The present specification discloses the following:

[0059] The present disclosure (1) is a CO ２ a partition wall defining a plurality of through holes that serve as a flow path for air containing CO; an outer peripheral wall provided on the outer periphery; and ２ an adsorbent, wherein the partition walls and the outer peripheral wall are made of silicon carbide, the opening ratio is 65 to 86%, and the surface area of ​​the partition walls is 1 cm 2 of the honeycomb structure. ３ 20-36cm per ２ and by heating from the surface of the outer peripheral wall, ２ CO adsorbed on the adsorbent ２ CO in the air is desorbed ２ A honeycomb structure for use in direct air capture (DAC) applications.

[0060] The present disclosure (2) is the honeycomb structure according to the present disclosure (1), wherein the heating from the surface of the outer peripheral wall is performed by an electric heater.

[0061] The present disclosure (3) is the honeycomb structure according to the present disclosure (1) or (2), wherein the range of the heated region on the surface of the outer peripheral wall is 50% or more.

[0062] The present disclosure (4) is ２ The honeycomb structure according to any one of (1) to (3) of the present disclosure, wherein the adsorbent is at least one selected from the group consisting of amines, zeolites, and MOFs (metal organic frameworks).

[0063] The present disclosure (5) is directed to a honeycomb structure having a cross-sectional area of ​​100 to 400 cm in a cross section perpendicular to the longitudinal direction, which is the direction in which the through holes extend. ２ The honeycomb structure according to any one of the present disclosures (1) to (4) is as follows:

[0064] The present disclosure (6) is the honeycomb structure according to any one of the present disclosures (1) to (5), wherein the length of the honeycomb structure in the longitudinal direction, which is the direction in which the through holes extend, is 100 to 500 mm.

[0065] The present disclosure (7) provides a honeycomb structure according to any one of the present disclosures (1) to (6), a heater provided on the surface of the outer wall of the honeycomb structure, and a CO 2 desorbed from the honeycomb structure. ２ and a container for containing the air.

[0066] EXAMPLES The following examples more specifically disclose embodiments of the present invention, but the present invention is not limited to these examples.

[0067] (Thermal Cycle Simulation) For a honeycomb structure having a predetermined structure and material, the time required for heating to a predetermined temperature and for cooling to the predetermined temperature was determined by simulation.

[0068] The fixed conditions for the simulation were as follows: Size of honeycomb structure: (end face □ 150 mm × 150 mm) × length in longitudinal direction 150 mm Heating temperature of outer wall surface: 100°C Cooling gas flow rate and temperature: SV = 36000 / h, 25°C

[0069] The physical properties of the material are as shown in Table 1 below.

[0070] Regarding heating, assuming that there is no heat radiation from the end faces of the honeycomb structure and no heat transfer in the longitudinal direction, the heat transfer from the outer wall to the center of the honeycomb structure was modeled two-dimensionally, and the heating temperature of the surface of the outer wall was set to 100°C (heater temperature), the heating start temperature was set to 22°C, and the heating time until the central temperature reached 100°C was defined as the temperature rise time (sec).

[0071] Regarding cooling, cooling gas was circulated through the through-holes, assuming that there was no heat radiation from the outer peripheral wall. The temperature of the cell partition walls at the start of cooling was set to 100°C, and the time required for the temperature of the cell partition walls to reach 25°C was defined as the cooling time (sec).

[0072]

[0073] The silicon carbide honeycomb structures of Examples 1 to 3 had a short heat cycle time and were suitable for DAC applications using heating from the surface of the outer wall. The cordierite honeycomb structure of Comparative Example 1 required a long temperature rise time and is therefore considered to be unsuitable for DAC applications using heating from the surface of the outer wall.

[0074] 20 Honeycomb structure 21 Through-hole 21a Gas inlet end of through-hole 21b Gas outlet end of through-hole 22 Partition wall 23 Outer wall 30 Electric heater 31 Heating wire 32 Electrode 33 Power source 40 Casing 51 Inlet pipe 52 Outlet pipe 53 CO ２ Storage pipe 61, 62, 63 Valve 64 Vacuum pump 70 CO ２ Storage container 72 Fan 100 DAC device

Claims

1. CO ２ a partition wall defining a plurality of through holes that serve as a flow path for air containing CO; an outer peripheral wall provided on the outer periphery; and ２ an adsorbent, wherein the partition walls and the outer peripheral wall are made of silicon carbide, the opening ratio is 65 to 86%, and the surface area of ​​the partition walls is 1 cm 2 of the honeycomb structure. ３ 20-36cm per ２ and by heating from the surface of the outer peripheral wall, ２ CO adsorbed on the adsorbent ２ CO in the air is desorbed ２ 1. A honeycomb structure for use in direct air capture (DAC) applications.

2. The honeycomb structure according to claim 1, wherein the heating from the surface of the outer peripheral wall is performed by an electric heater.

3. A honeycomb structure according to claim 1 or 2, wherein the heated area of ​​the surface of said outer wall is 50% or more.

4. The above CO ２ 4. The honeycomb structure according to claim 1, wherein the adsorbent is at least one selected from the group consisting of amines, zeolites, and MOFs (metal organic frameworks).

5. The cross-sectional area of ​​the honeycomb structure perpendicular to the longitudinal direction, which is the direction in which the through holes extend, is 100 to 400 cm ２ 5. The honeycomb structure according to claim 1, wherein:

6. A honeycomb structure according to any one of claims 1 to 5, wherein the length of the honeycomb structure in the longitudinal direction, which is the direction in which the through holes extend, is 100 to 500 mm.

7. A honeycomb structure according to any one of claims 1 to 6, a heater provided on the surface of the outer wall of the honeycomb structure, and CO desorbed from the honeycomb structure. ２ and a container for containing the air.

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