Honeycomb structure and method for producing same

Abstract

This honeycomb structure includes a plurality of cell channels passing through the interior of the honeycomb structure and partitioned by a partition wall 20. The partition wall 20 includes a carbon dioxide adsorbent 60 the surface of which is at least partially coated with a water repellent agent 70.

Description

Honeycomb structure and manufacturing method thereof

[0001] The present invention relates to a honeycomb structure and a method for manufacturing the same.

[0002] To realize a decarbonized society, there is a growing need for technologies that capture and utilize greenhouse gases (e.g., carbon dioxide) from the atmosphere and exhaust gases. A typical conventional carbon dioxide (CO2) capture technology is Direct Air Capture (DAC), which adsorbs CO2 from the atmosphere. There are several types of DAC, including liquid absorption, membrane separation, and solid adsorption. Among these, the use of a honeycomb structure containing a CO2 adsorbent (absorbent) has been considered for the solid adsorption method.

[0003] For example, Patent Document 1 (Patent Document 1) describes a honeycomb structure having a plurality of partition walls extending axially from the inlet end to the outlet end, thereby forming a plurality of flow channels. The honeycomb structure comprises a mixture of an inorganic powder component and an organic binder, and an amine polymer having a functional structural unit group capable of absorbing CO2 is dispersed in the inorganic powder component of the partition walls. The honeycomb structure can adsorb CO2 by passing a CO2-containing process gas through the cells. Furthermore, the CO2 adsorbed in the honeycomb structure can be desorbed by passing a purge gas (desorption gas) such as water vapor through the cells.

[0004] Special table 2015-508018 publication

[0005] As described above, the CO2 adsorbed in the honeycomb structure is desorbed by passing a purge gas such as water vapor through the cells, but at this time the carbon dioxide adsorbent (amine polymer) absorbs water and expands, so the size of the honeycomb structure becomes larger when CO2 is desorbed than when CO2 is adsorbed. If the size of the honeycomb structure changes between when CO2 is adsorbed and when CO2 is desorbed in this way, the honeycomb structure becomes more susceptible to damage inside the carbon dioxide recovery device.

[0006] The present invention has been made to solve the above-mentioned problems, and aims to provide a honeycomb structure and a manufacturing method thereof that can suppress expansion of a carbon dioxide adsorbent and reduce size fluctuations during the carbon dioxide adsorption and desorption cycle.

[0007] As a result of extensive research into honeycomb structures having partition walls containing a carbon dioxide adsorbent, the present inventors have found that the expansion of the carbon dioxide adsorbent can be suppressed by coating at least a portion of the surface of the carbon dioxide adsorbent with a water repellent, and have thus completed the present invention. That is, the present invention is exemplified as follows.

[0008] <1> A honeycomb structure having a plurality of cell channels that pass through the interior of the honeycomb structure and are separated by partition walls, wherein the partition walls contain a carbon dioxide adsorbent having at least a portion of its surface coated with a water repellent agent.

[0009] <2> The honeycomb structure according to <1>, wherein at least a part of the surface of all the carbon dioxide adsorbents contained in the partition walls is coated with the water repellent agent.

[0010] <3> The honeycomb structure according to <1>, wherein at least a part of the surface of the carbon dioxide adsorbent exposed on the surface of the partition wall is coated with the water repellent agent.

[0011] <4> The honeycomb structure according to any one of <1> to <3>, wherein the water repellent agent is at least one selected from the group consisting of stearic acid, a fluororesin, and a silicone resin.

[0012] <5> The honeycomb structure according to any one of <1> to <4>, wherein the amount of the water repellent agent is 2 parts by mass or more relative to 100 parts by mass of the carbon dioxide adsorbent.

[0013] <6> The honeycomb structure according to any one of <1> to <5>, wherein the carbon dioxide adsorbent is a solid organic compound having at least one selected from an amino group and an ammonium group.

[0014] <7> The honeycomb structure according to <6>, wherein the solid organic compound is a weakly basic anion exchange resin having an amino group and / or a strongly basic anion exchange resin having an ammonium group.

[0015] <8> The honeycomb structure according to <6>, wherein the solid organic compound is a styrene-divinylbenzene copolymer having one or more selected from an amino group and an ammonium group, and / or an acrylic copolymer having one or more selected from an amino group and an ammonium group.

[0016] <9> The honeycomb structure according to any one of <1> to <8>, wherein the partition walls further contain a binder, and the binder is made of an organic binder.

[0017] <10> A method for manufacturing a honeycomb structure, comprising: a first step of coating at least a part of the surface of a carbon dioxide adsorbent with a water repellent; a second step of kneading a forming raw material containing the carbon dioxide adsorbent to prepare a clay; a third step of forming the clay into a honeycomb formed body, the honeycomb formed body having a plurality of cell channels that pass through the interior and are separated by partition walls; and a fourth step of drying the honeycomb formed body.

[0018] <11> A method for manufacturing a honeycomb structure, comprising: a first step of kneading a forming raw material containing a carbon dioxide adsorbent to prepare a puddle; a second step of forming the puddle into a honeycomb formed body, the honeycomb formed body having a plurality of cell channels that pass through the interior and are separated by partition walls; and a third step of drying the honeycomb formed body, and further comprising a fourth step of coating at least a part of the surface of the partition wall with a water repellent agent between the second step and the third step or after the third step.

[0019] <12> The method for manufacturing a honeycomb structure according to <10> or <11>, wherein the water repellent agent is at least one selected from the group consisting of stearic acid, a fluororesin, and a silicone resin.

[0020] <13> The method for manufacturing a honeycomb structure according to any one of <10> to <12>, wherein the forming raw material further contains a binder, and the binder is made of an organic binder.

[0021] According to the present invention, it is possible to provide a honeycomb structure and a manufacturing method thereof that can suppress expansion of a carbon dioxide adsorbent and reduce fluctuations in size during the carbon dioxide adsorption and desorption cycle.

[0022] 1A is a schematic diagram of an end face 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 aa' in FIG. 1A. FIG. 1B is a schematic diagram of an enlarged cross section near the surface of a partition wall of a honeycomb structure according to an embodiment of the present invention. FIG. 1C is a schematic diagram of an enlarged cross section near the surface of a partition wall of another honeycomb structure according to an embodiment of the present invention. FIG. 1D is a schematic diagram of an enlarged cross section near the surface of a partition wall of another honeycomb structure according to an embodiment of the present invention.

[0023] The honeycomb structure of the present invention has a plurality of cell channels that pass through the interior and are separated by partition walls, and the partition walls contain a carbon dioxide adsorbent having at least a portion of its surface coated with a water-repellent agent. Here, in this specification, "water-repellent agent" refers to an agent that imparts water repellency to the portion to which the water-repellent agent is attached. In the honeycomb structure of the present invention, at least a portion of the surface of the carbon dioxide adsorbent contained in the partition walls is coated with a water-repellent agent, making it difficult for the carbon dioxide adsorbent to absorb water and suppressing its expansion. Therefore, it is possible to reduce fluctuations in the size of the honeycomb structure during the carbon dioxide adsorption and desorption cycle, making it possible to suppress breakage within the carbon dioxide recovery device.

[0024] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The present invention is not limited to the following embodiments, and it should be understood that modifications and improvements made to the following embodiments based on the 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.

[0025] (1. Honeycomb structure) Fig. 1A is a schematic diagram of an end face 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 aa' in Fig. 1A (a cross section parallel to the cell extension direction).

[0026] As shown in FIGS. 1A and 1B , the honeycomb structure has a plurality of cells 30 (cell channels) that pass through the interior and are separated by partition walls 20. Specifically, the honeycomb structure includes an outer peripheral wall 10 and partition walls 20 disposed on the inner periphery of the outer peripheral wall 10, extending from a first end face 40 to a second end face 50, and separating the plurality of cells 30 that form fluid flow paths. The plurality of cells 30 are arranged parallel to one another. The honeycomb structure is a flow-through type in which both end faces (first end face 40 and second end face 50) of each cell 30 are open. When a gas containing carbon dioxide (e.g., air) flows in through the first end face 40 where the inlets of the plurality of cells 30 are located, the carbon dioxide is adsorbed as it passes through the plurality of cells 30, and the gas with a reduced carbon dioxide concentration flows out from the second end face 50 where the outlets of the plurality of cells 30 are located.

[0027] The end face shape of the honeycomb structure is not particularly limited, and may be, for example, a round shape such as a circle, an ellipse, a racetrack shape, or an oval shape, a polygonal shape such as a triangle or a rectangle, or other irregular shapes. The outer shape of the honeycomb structure may typically be a columnar shape. The honeycomb structure shown in Figures 1A and 1B has a square end face shape and is an example of a square columnar shape as a whole.

[0028] The length of the honeycomb structure in the direction in which the cells 30 extend (the length from the first end face 40 to the second end face 50) 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 30 extend can increase the amount of carbon dioxide adsorption, 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.

[0029] The diameter of each end face 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 each end face of the honeycomb structure can increase the amount of carbon dioxide adsorption, if the diameter is too large, manufacturing becomes more difficult. Therefore, 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 each end face of the honeycomb structure in this specification means the diameter if the shape is circular, and means the circle-equivalent diameter if the shape is other than circular.

[0030] The partition walls 20 constituting the honeycomb structure contain a carbon dioxide adsorbent. Furthermore, the outer peripheral wall 10 constituting the honeycomb structure can also contain a carbon dioxide adsorbent, similar to the partition walls 20. By incorporating a carbon dioxide adsorbent into the partition walls 20 and the outer peripheral wall 10, carbon dioxide adsorption becomes possible. Furthermore, compared to conventional honeycomb structures in which the surfaces of the partition walls 20 and the outer peripheral wall 10 are coated with a carbon dioxide adsorbent, the honeycomb structure is manufactured without undergoing a firing process at a high heating temperature, thereby reducing the amount of carbon dioxide generated during manufacturing. Furthermore, the amount of carbon dioxide adsorbent supported can be increased, thereby increasing the amount of carbon dioxide adsorption.

[0031] At least a portion of the surface of the carbon dioxide adsorbent is coated with a water repellent. Coating the carbon dioxide adsorbent with a water repellent in this manner can suppress expansion of the carbon dioxide adsorbent due to water absorption, thereby making it possible to reduce size fluctuations during the carbon dioxide adsorption and desorption cycles.

[0032] 2A to 2C are schematic enlarged cross-sectional views of the vicinity of the surface of partition wall 20 to illustrate a state in which at least a portion of the surface of the carbon dioxide adsorbent is coated with a water repellent agent. As shown in FIGS. 2A and 2B, at least a portion of the surface of all of the carbon dioxide adsorbents 60 contained in partition wall 20 can be coated with a water repellent agent 70. Furthermore, as shown in FIG. 2C, at least a portion of the surface of the carbon dioxide adsorbent 60 exposed on the surface of partition wall 20 can be coated with a water repellent agent 70. By coating the carbon dioxide adsorbent 60 with the water repellent agent 70 in this manner, expansion of the carbon dioxide adsorbent 60 due to water absorption can be suppressed.

[0033] Furthermore, it is preferable that the coating of the water repellent agent 70 is permeable to carbon dioxide. If the coating has such a property, it is possible to suppress a decrease in the adsorption capacity of the carbon dioxide adsorbent 60, especially when the coating of the water repellent agent 70 shown in Figures 2B and 2C is present.

[0034] There are no particular limitations on the water repellent agent 70, and any known agent can be used. Among them, the water repellent agent 70 is preferably one or more selected from stearic acid, fluororesin, and silicone resin. By using such a water repellent agent 70, expansion of the carbon dioxide adsorbent 60 due to water absorption can be stably suppressed.

[0035] The amount of water repellent agent 70 is not particularly limited and may be adjusted appropriately depending on the types of carbon dioxide adsorbent 60 and water repellent agent 70 used. From the viewpoint of stably suppressing expansion of the carbon dioxide adsorbent 60 due to water absorption, the amount of water repellent agent 70 relative to 100 parts by mass of carbon dioxide adsorbent 60 is preferably 2 parts by mass or more, more preferably 5 parts by mass or more, even more preferably 8 parts by mass or more, and particularly preferably 10 parts by mass or more. On the other hand, from the viewpoint of increasing the amount of carbon dioxide adsorption, the amount of water repellent agent 70 relative to 100 parts by mass of carbon dioxide adsorbent 60 is preferably 30 parts by mass or less, more preferably 25 parts by mass or less, and even more preferably 20 parts by mass or less.

[0036] The carbon dioxide adsorbent 60 is preferably dispersed in the partition walls 20. Similarly, the carbon dioxide adsorbent 60 is preferably dispersed in the outer peripheral wall 10. By dispersing the carbon dioxide adsorbent 60 in the partition walls 20 and the outer peripheral wall 10 in this manner, the amount of carbon dioxide adsorption can be increased.

[0037] The carbon dioxide adsorbent 60 is not particularly limited, and known adsorbents can be used. Among them, the carbon dioxide adsorbent 60 is preferably an adsorbent having an amino group (one or more selected from -NH, -NHR, and -NRR' (R and R' represent organic groups)) and an ammonium group (-N + Preferably, the adsorbent is a solid organic compound having one or more selected from the group consisting of aryl, ...

[0038] The solid organic compound having one or more selected from the amino group and the ammonium group is preferably water-insoluble from the viewpoint of water resistance. The solid organic compound having one or more selected from the amino group and the ammonium group is preferably —NH2, —NHR, —NRR′, —N + The solid organic compound may have any of RR'R" (R, R', and R" represent organic groups), or may have two or more of these in combination. Among amino groups, it is particularly preferable to have a primary amine (-NH2) as a functional group. It is also preferable that the solid organic compound having one or more selected from amino groups and ammonium groups contains an aromatic ring.

[0039] Specific examples of solid organic compounds having one or more groups 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. Furthermore, solid organic compounds having one or more groups selected from amino groups and ammonium groups include styrene-divinylbenzene copolymers having one or more groups selected from amino groups and ammonium groups, and acrylic copolymers having one or more groups selected from amino groups and ammonium groups. These can be used alone or in combination of two or more. Examples of styrene-divinylbenzene copolymers having one or more groups selected from amino groups and ammonium groups include copolymers of styrene and divinylbenzene. Examples of acrylic copolymers having one or more groups selected from amino groups and ammonium groups include (meth)acrylic acid-divinylbenzene copolymers. While OH-type, Cl-type, HCO3-type, etc. can be used as strongly basic anion exchange resins having ammonium groups, OH-type or HCO3-type are preferred from the viewpoint of carbon dioxide adsorption performance. That is, the counter anion of the ammonium group is OH. ― or HCO3 ― is preferred.

[0040] From the viewpoint of carbon dioxide 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 carbon dioxide adsorption performance, the exchange capacity of the strongly basic anion exchange resin is preferably 0.6 meq / mL or more, 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 solution is passed through.

[0041] The content of the carbon dioxide adsorbent 60 in the partition walls 20 (and the outer peripheral wall 10 as necessary) 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 carbon dioxide adsorbent 60 can be increased, and therefore the carbon dioxide adsorption performance is improved.

[0042] The partition walls 20 (and the outer peripheral wall 10, if necessary) may further contain a binder 80 in addition to the carbon dioxide adsorbent 60 and the water repellent 70. By including the binder 80, the strength of the honeycomb structure can be increased. The binder 80 is not particularly limited, but is preferably made of an organic binder.

[0043] 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, polyurethane, methacrylic acid ester, acrylic, ethyl cellulose, silicone, and polyolefin. These can be used alone or in combination of two or more. 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, and polyethylene oxide can reduce environmental impact, the risk of organic solvent vapor during drying, and production costs.

[0044] The amount of the organic binder is not particularly limited, but the amount of the organic binder relative to 100 parts by mass of the carbon dioxide adsorbent 60 is preferably 5 to 30 parts by mass, more preferably 8 to 25 parts by mass, and even more preferably 10 to 20 parts by mass.

[0045] In addition to the above components, the partition wall 20 (and the outer peripheral wall 10, if necessary) 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.

[0046] The thickness of the peripheral wall 10 is not particularly limited, but is preferably 0.1 to 4.0 mm, more preferably 0.2 to 3.0 mm, and even more preferably 0.3 to 2.5 mm, from the viewpoint of ensuring strength. In this specification, the thickness of the peripheral wall 10 refers to the length in the normal direction to the peripheral surface of the honeycomb structure from the boundary between the peripheral wall 10 and the outermost cell 30 or partition wall 20 to the peripheral surface of the honeycomb structure, in a cross section perpendicular to the extension direction of the cells 30 of the honeycomb structure.

[0047] The thickness of the partition walls 20 is not particularly limited, but is preferably 50 μm or more, more preferably 80 μm or more, and even more preferably 100 μm or more, from the viewpoint of ensuring strength. Furthermore, the thickness of the partition walls 20 is preferably 50 to 600 μm, more preferably 80 to 550 μm, and even more preferably 100 to 500 μm, from the viewpoint of suppressing pressure loss. In this specification, the thickness of the partition walls 20 is defined as the length of the portion of a line segment connecting the centers of gravity of adjacent cells 30 that passes through the partition wall 20 in a cross section of the honeycomb structure perpendicular to the extension direction of the cells 30. Furthermore, the thickness of the partition walls 20 refers to the average thickness of all the partition walls 20 in the honeycomb structure.

[0048] It is preferable that the thickness of the outer peripheral wall 10 is the same as that of the partition walls 20. With such a configuration, it is possible to suppress an increase in pressure loss and increase the amount of carbon dioxide adsorption while ensuring the strength of the honeycomb structure.

[0049] The cell density of the honeycomb structure (the number of cells 30 per unit cross-sectional area) is not particularly limited, but is preferably 8 to 124 cells / cm. 2 , more preferably 16 to 62 cells / cm 2 By controlling the cell density within this range, it becomes easier to obtain the effect of suppressing an increase in pressure loss and the effect of improving the mechanical strength and the amount of carbon dioxide adsorption. 2 If the cell density is less than 124 cells / cm, the mechanical strength and the amount of carbon dioxide adsorption tend to decrease. 2When the cell density exceeds this value, the pressure loss is likely to increase. Here, in this specification, the cell density is calculated by dividing the number of cells 30 in the honeycomb structure by the area of ​​one end face excluding the outer wall 10 of the honeycomb structure.

[0050] The shape of the cells 30 in the cross section perpendicular to the extension direction of the cells 30 of the honeycomb structure 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 30 is preferably a square or a hexagon. By configuring the cells 30 in this way, it is possible to suppress an increase in pressure loss when gas is flowed through the honeycomb structure.

[0051] (2. Carbon Dioxide Capture Method and Desorption Method) The carbon dioxide capture method and desorption method according to an embodiment of the present invention are carried out using the above-described honeycomb structure. Specifically, the carbon dioxide capture method according to an embodiment of the present invention includes flowing a gas containing carbon dioxide through a plurality of cell channels of the honeycomb structure, adsorbing the carbon dioxide in the gas by a carbon dioxide adsorbent 60 while the gas passes through the plurality of cells 30 (cell channels), and discharging the gas with a reduced carbon dioxide concentration from the honeycomb structure. The gas is not particularly limited as long as it contains carbon dioxide, and examples thereof include environmental air (outdoor air, as well as indoor or indoor air), factory exhaust gas, ship exhaust gas, and power plant exhaust gas.

[0052] Furthermore, a carbon dioxide desorption method according to an embodiment of the present invention includes flowing a desorbed gas or a heated desorbed gas through a plurality of cells 30 (cell channels) of a honeycomb structure in which carbon dioxide has been adsorbed, and desorbing carbon dioxide from the carbon dioxide adsorbent 60 into the desorbed gas as the desorbed gas passes through the plurality of cells 30. The desorbed gas is not particularly limited as long as it is a gas capable of desorbing carbon dioxide, and examples thereof include water vapor. 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.

[0053] (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.

[0054] In one aspect, the manufacturing method of the honeycomb structure according to the embodiment of the present invention includes a coating step (first step) of the carbon dioxide adsorbent 60, a clay preparation step (second step), a molding step (third step) of forming the honeycomb formed body, and a drying step (fourth step) of the honeycomb formed body. By using this manufacturing method, it is possible to obtain a honeycomb structure in which at least a part of the surface of all the carbon dioxide adsorbents 60 contained in the partition walls 20 is coated with the water repellent agent 70, as shown in Figures 2A and 2B.

[0055] The coating step (first step) of the carbon dioxide adsorbent 60 is a step of coating at least a portion of the surface of the carbon dioxide adsorbent 60 with the water repellent 70. The coating method is not particularly limited, and known methods can be used. For example, the water repellent 70 may be added to and mixed with the carbon dioxide adsorbent 60, the water repellent 70 may be spray coated onto the carbon dioxide adsorbent 60, or the carbon dioxide adsorbent 60 may be immersed in a large amount of water repellent 70 for coating. From the viewpoint of stably suppressing expansion of the carbon dioxide adsorbent 60 due to water absorption, the blend amount of the water repellent 70 is preferably 2 parts by mass or more, more preferably 5 parts by mass or more, even more preferably 8 parts by mass or more, and particularly preferably 10 parts by mass or more, per 100 parts by mass of the carbon dioxide adsorbent 60. Furthermore, from the viewpoint of increasing the amount of carbon dioxide adsorption, the blend amount of the water repellent 70 is preferably 30 parts by mass or less, more preferably 25 parts by mass or less, and even more preferably 20 parts by mass or less, per 100 parts by mass of the carbon dioxide adsorbent 60. The greater the blend amount of the water repellent agent 70, the higher the proportion of the coating of the water repellent agent 70 that covers the surface of the carbon dioxide adsorbent 60 can be.

[0056] To prevent clogging during molding, the carbon dioxide adsorbent 60 preferably has a median diameter (D50) based on a volume-based cumulative particle size distribution obtained by a laser diffraction / scattering method of 200 μm or less, more preferably 100 μm or less, even more preferably 50 μm or less, even more preferably 30 μm or less, and particularly preferably 15 μm or less. For reasons of availability and suppression of secondary aggregation, the median diameter (D50) of the carbon dioxide adsorbent 60 is preferably 0.1 μm or more, more preferably 0.5 μm or more, and even more preferably 1 μm or more. Therefore, the median diameter (D50) of the carbon dioxide adsorbent 60 is, for example, preferably 0.1 to 100 μm, more preferably 0.5 to 50 μm, even more preferably 1 to 50 μm, even more preferably 1 to 30 μm, and particularly preferably 1 to 15 μm.

[0057] The clay preparation step (second step) is a step of kneading a molding raw material containing the carbon dioxide adsorbent 60 coated with the water repellent 70 in the first step to prepare a clay. The molding raw material may further contain an organic binder and a solvent. The solvent (dispersion medium) is not particularly limited as long as it does not dissolve the water repellent 70, and examples thereof include water or a mixed solvent of water and an organic solvent such as alcohol, with water being particularly preferred. The amount of organic binder excluding the solvent in the molding raw material is preferably 5 to 30 parts by mass, more preferably 8 to 25 parts by mass, and even more preferably 10 to 20 parts by mass per 100 parts by mass of the carbon dioxide adsorbent 60, from the viewpoint of achieving a good balance between carbon dioxide adsorption performance, crack suppression during drying, and water resistance. The solvent content in the molding raw material is adjusted to obtain a clay with a hardness suitable for molding (particularly extrusion molding).

[0058] When a water-soluble organic binder is used as the organic binder, the organic binder dissolves during kneading. Therefore, there are no particular limitations on the shape and size, and it is sufficient to use an organic binder in a generally available form. When a water-insoluble organic binder is used, it dissolves during kneading if an organic solvent is used. Therefore, there are no particular limitations on the shape and size.

[0059] 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.

[0060] The forming step (third step) into a honeycomb formed body is a step of forming the clay obtained in the second step into a honeycomb formed body. The honeycomb formed body has a plurality of cells 30 (cell channels) that pass through the interior and are partitioned by partition walls 20. Specifically, in the third step, the honeycomb formed body is extrusion-molded into a honeycomb formed body that includes an outer peripheral wall 10 and partition walls 20 that are disposed on the inner peripheral side of the outer peripheral wall 10, extend from a first end face 40 to a second end face 50, and partition the plurality of cells 30 that form fluid flow paths. During extrusion molding, a die having a desired overall shape, cell shape, partition wall thickness, cell density, etc. can be used.

[0061] The honeycomb formed body drying step (step 4) is a step of drying the honeycomb formed body obtained in step 3. 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 carbon dioxide adsorbent 60, the water repellent agent 70, and the organic binder during drying, it is preferable to dry the honeycomb formed body in an air atmosphere at 20 to 150°C, more preferably in an air atmosphere at 30 to 140°C, and even more preferably in an air atmosphere at 40 to 130°C.

[0062] In another aspect, the manufacturing method of the honeycomb structure according to the embodiment of the present invention includes a clay preparation step (first step), a molding step into a honeycomb formed body (second step), a drying step of the honeycomb formed body (third step), and a coating step (fourth step) of the partition walls 20. By using this manufacturing method, it is possible to obtain a honeycomb structure in which at least a portion of the surface of the carbon dioxide adsorbent 60 exposed on the surface of the partition walls 20 is coated with a water repellent agent 70, as shown in Fig. 2C .

[0063] The clay preparation step (first step) is a step of kneading a molding raw material containing a carbon dioxide adsorbent 60 to prepare a clay. The molding raw material may further contain an organic binder and a solvent. The solvent (dispersion medium) is not particularly limited, and examples include water or a mixed solvent of water and an organic solvent such as alcohol, with water being particularly preferred. From the viewpoint of achieving a good balance between carbon dioxide adsorption performance, crack suppression during drying, and water resistance, the content of the carbon dioxide adsorbent 60 excluding the solvent in the molding raw material is preferably 40 to 94% by mass, more preferably 50 to 90% by mass, and even more preferably 60 to 80% by mass. From the same viewpoint, the content of the organic binder excluding the solvent in the molding raw material is preferably 5 to 30% by mass, more preferably 8 to 25% by mass, and even more preferably 10 to 20% by mass. The solvent content in the molding raw material is adjusted to obtain a clay with a hardness suitable for molding (particularly extrusion molding).

[0064] When a water-soluble organic binder is used as the organic binder, the organic binder dissolves during kneading. Therefore, there are no particular limitations on the shape and size, and it is sufficient to use an organic binder in a generally available form. When a water-insoluble organic binder is used, it dissolves during kneading if an organic solvent is used. Therefore, there are no particular limitations on the shape and size.

[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. The honeycomb formed body has a plurality of cells 30 (cell channels) that pass through the interior and are partitioned by partition walls 20. Specifically, in the second step, extrusion is performed to form a honeycomb formed body that includes an outer peripheral wall 10 and partition walls 20 that are disposed on the inner peripheral side of the outer peripheral wall 10, extend from a first end face 40 to a second end face 50, and partition the plurality of cells 30 that form fluid flow paths. During extrusion, 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 carbon dioxide adsorbent 60, the water repellent agent 70, and the organic binder during drying, it is preferable to dry the honeycomb formed body in an air atmosphere at 20 to 150°C, more preferably in an air atmosphere at 30 to 140°C, and even more preferably in an air atmosphere at 40 to 130°C.

[0068] The coating step (fourth step) of the partition walls 20 is a step of coating at least a part of the surface of the partition walls 20 with the water repellent agent 70 between the second step and the third step or after the third step. The coating method is not particularly limited, and a known method can be used. For example, a slurry containing the water repellent agent 70 and a solvent (for example, water) may be applied to the partition walls 20 and dried. The drying conditions are not particularly limited, and may be the same as those of the third step described above.

[0069] (4. Carbon Dioxide Capture Apparatus) A carbon dioxide capture apparatus according to an embodiment of the present invention includes one or more of the above-described honeycomb structures. Because this carbon dioxide capture apparatus includes the above-described honeycomb structure, size fluctuations during the carbon dioxide adsorption and desorption cycles are small, and damage to the honeycomb structure can be suppressed.

[0070] The carbon dioxide capture 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 that can supply and discharge a gas containing carbon dioxide and a desorbed gas. A carbon dioxide capture device having such a structure can easily achieve the capture and desorption of carbon dioxide.

[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-based divinylbenzene polymer having a primary amine functional group with an exchange capacity of 2.0 meq / mL) was prepared as a carbon dioxide adsorbent. The carbon dioxide adsorbent had a median diameter (D50) of 10 μm when the volume-based cumulative particle size distribution was measured using a laser diffraction / scattering method. Stearic acid and silicone were prepared as water repellents. Polyurethane, PVA (polyvinyl alcohol), and methyl cellulose were prepared as organic binders. Industrial water was prepared as a solvent.

[0073] <Preparation of honeycomb structure (Type A)> The surface of the water repellent was pre-coated by blending 100 parts by mass of a carbon dioxide adsorbent with the water repellent in the amounts shown in Table 1. Next, the carbon dioxide adsorbent whose surface was coated with the water repellent was blended with the organic binder and solvent in the amounts shown in Table 1 to obtain a molding material. Next, the molding material was kneaded for 30 minutes in a vacuum kneader to prepare a clay. The amount of solvent blended was adjusted so that the clay had a hardness suitable for molding.

[0074] Next, the clay was molded using an extrusion molding machine having 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 have the following conditions: Outer shape: rectangular pillar-shaped Cross-sectional shape of cells of the honeycomb molded body (honeycomb structure): rectangular Length in the cell extension direction of the honeycomb molded body (honeycomb structure): 120 mm Diameter of each end face: 60 mm Thickness of outer peripheral wall: 1 mm Thickness of partition wall: 200 μm Cell density: 46.5 cells / cm 2

[0075] 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 length to prepare a honeycomb structure.

[0076] <Preparation of Honeycomb Structure (Type B)> The carbon dioxide adsorbent was blended with the organic binder and solvent in the amounts shown in Table 1 to obtain a molding material. The molding material was then kneaded for 30 minutes using a vacuum kneader to prepare a clay. The amount of solvent was adjusted so that the clay had a hardness suitable for molding. The clay was then 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 dried honeycomb molded body (honeycomb structure) would have the same conditions as described above. The resulting honeycomb molded body was then subjected to high-frequency dielectric drying, dried in a microwave dryer in an air atmosphere at 100°C for 2 minutes, and both end faces were cut off to a predetermined length to produce a honeycomb structure. Next, the water repellent agent in the amount shown in Table 1 was sprayed onto the partition walls of the honeycomb structure and dried under the same conditions as described above.

[0077] Next, the expansion coefficient of the honeycomb structure obtained above was evaluated. The cell pitch of the honeycomb structure was measured using a microscope before and after immersion in water for 10 minutes, and the expansion coefficient was calculated using the following formula: Expansion coefficient [%] = Cell pitch size after immersion / Cell pitch size before immersion × 100. In this evaluation, if the expansion coefficient is 9.0% or less, it can be determined that the expansion due to water absorption of the adsorbent is small and the size fluctuation of the honeycomb structure is small. The "cell pitch" was calculated using the following calculation: First, the area of ​​one end face (first end face or second end face) of the honeycomb structure (the total area of ​​the partition walls and cells excluding the outer peripheral wall) was divided by the number of cells to calculate the area per cell. Next, the square root of the area per cell was calculated, and this was defined as the cell pitch. The results of the expansion coefficient evaluation are shown in Table 1.

[0078]

[0079] As shown in Table 1, the honeycomb structures (Examples 1 to 3) having partition walls containing a carbon dioxide adsorbent whose surface was at least partially coated with a water repellent had a smaller expansion rate than the honeycomb structures (Comparative Examples 1 and 2) having partition walls containing a carbon dioxide adsorbent that was not coated with a water repellent.

[0080] As can be seen from the above results, the present invention can provide a honeycomb structure and a manufacturing method thereof that can suppress the expansion of the carbon dioxide adsorbent and reduce size fluctuations during the carbon dioxide adsorption and desorption cycle.

[0081] 10 outer peripheral wall 20 partition wall 30 cell 40 first end face 50 second end face 60 carbon dioxide adsorbent 70 water repellent agent 80 binder

Claims

1. A honeycomb structure having a plurality of cell channels passing through the interior of the honeycomb structure and separated by partition walls, the partition walls containing a carbon dioxide adsorbent having at least a portion of its surface coated with a water repellent agent.

2. The honeycomb structure according to claim 1, wherein at least a portion of the surface of all of the carbon dioxide adsorbents contained in the partition walls is coated with the water repellent agent.

3. The honeycomb structure according to claim 1, wherein at least a portion of the surface of the carbon dioxide adsorbent exposed on the surface of the partition wall is coated with the water repellent agent.

4. The honeycomb structure according to any one of claims 1 to 3, wherein the water repellent agent is at least one selected from the group consisting of stearic acid, fluororesin, and silicone resin.

5. A honeycomb structure according to any one of claims 1 to 3, wherein the amount of the water repellent agent is 2 parts by mass or more per 100 parts by mass of the carbon dioxide adsorbent.

6. A honeycomb structure according to any one of claims 1 to 3, wherein the carbon dioxide adsorbent is a solid organic compound having at least one group selected from the group consisting of an amino group and an ammonium group.

7. The honeycomb structure according to claim 6, wherein the solid organic compound is a weakly basic anion exchange resin having an amino group and / or a strongly basic anion exchange resin having an ammonium group.

8. The honeycomb structure according to claim 6, wherein the solid organic compound is a styrene-divinylbenzene copolymer having one or more groups selected from an amino group and an ammonium group, and / or an acrylic copolymer having one or more groups selected from an amino group and an ammonium group.

9. The honeycomb structure according to any one of claims 1 to 3, wherein the partition walls further contain a binder, and the binder is an organic binder.

10. A method for manufacturing a honeycomb structure, comprising: a first step of coating at least a portion of the surface of a carbon dioxide adsorbent with a water repellent; a second step of kneading a forming raw material containing the carbon dioxide adsorbent to prepare a clay; a third step of forming the clay into a honeycomb formed body, the honeycomb formed body having a plurality of cell channels passing through the interior and separated by partition walls; and a fourth step of drying the honeycomb formed body.

11. A method for manufacturing a honeycomb structure, comprising: a first step of kneading forming raw materials containing a carbon dioxide adsorbent to prepare a clay; a second step of forming the clay into a honeycomb formed body, the honeycomb formed body having a plurality of cell channels passing through the interior and separated by partition walls; and a third step of drying the honeycomb formed body, and further comprising a fourth step of coating at least a portion of the surface of the partition walls with a water repellent agent between the second step and the third step or after the third step.

12. The method for manufacturing a honeycomb structure according to claim 10 or 11, wherein the water repellent agent is at least one selected from the group consisting of stearic acid, fluororesin and silicone resin.

13. The method for manufacturing a honeycomb structure according to claim 10 or 11, wherein the forming raw material further contains a binder, and the binder is an organic binder.

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