Porous body and gas recovery device

Abstract

This porous body contains an adsorbent capable of adsorbing and desorbing greenhouse gas, and is provided with pores. When the moisture content of the porous body is 40 mass%, the pore volume for pores having a pore diameter greater than 1 μm is not greater than 20%, the pore volume for pores having a pore diameter less than 0.1 μm is not greater than 20%, and the pore volume for pores having a pore diameter of 0.1-1 μm is at least 60%.

Description

Porous material and gas recovery device

[0001] This invention relates to a porous body and a gas recovery device.

[0002] To realize a decarbonized society, there is a growing need for technologies to capture and utilize greenhouse gases (e.g., carbon dioxide) from the atmosphere and exhaust gases. A representative 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 porous materials containing CO2 adsorbents is being considered for solid adsorption.

[0003] For example, Patent Document 1 describes a porous body (CO2 capture absorption structure) having a plurality of partition walls extending axially from an inlet end to an outlet end, thereby forming a plurality of flow channels, and comprising a honeycomb substrate containing a mixture of inorganic powder components and a binder, in which an amine polymer having a functional structural unit group that absorbs CO2 is dispersed in the inorganic powder component of the partition walls.

[0004] Special table 2015-508018 publication

[0005] The porous material described in Patent Document 1 can adsorb CO2 by passing a CO2-containing treatment gas through it. However, the pore structure of this porous material has not been studied in detail, and its CO2 adsorption performance was not considered sufficient. Furthermore, since CO2 adsorption often occurs under high humidity conditions, the adsorption performance of CO2 may decrease if the adsorbent expands due to moisture. Although the above explanation used CO2 as the target gas for adsorption, similar problems exist when adsorbing and desorbing other greenhouse gases.

[0006] This invention was made to solve the above-mentioned problems, and aims to provide a porous body and a gas recovery device that have excellent greenhouse gas adsorption performance even when wet.

[0007] The inventors of the present invention have diligently researched porous bodies containing an adsorbent capable of adsorbing and desorbing greenhouse gases and having pores. As a result, they have discovered that when the moisture content of the porous body is 40% by mass, the adsorption performance of greenhouse gases can be improved even when wet by controlling the pore volume ratio of a predetermined size within a predetermined range, thus completing the present invention. That is, the present invention is illustrated as follows.

[0008] <1> A porous body having pores and containing an adsorbent capable of adsorbing and desorbing greenhouse gases, wherein when the moisture content of the porous body is 40% by mass, the pores have a volume ratio of 20% or less for pores with a diameter of 1 μm or more, a volume ratio of 20% or less for pores with a diameter of less than 0.1 μm, and a volume ratio of 60% or more for pores with a diameter of 0.1 to 1 μm.

[0009] <2> The porous body according to <1>, wherein the pores have a pore volume ratio of 10% or less for pores with a diameter of 1 μm, a pore volume ratio of 10% or less for pores with a diameter of less than 0.1 μm, and a pore volume ratio of 85% or more for pores with a diameter of 0.1 to 1 μm.

[0010] <3> The porous body according to <1> or <2>, wherein the adsorbent is a solid organic compound having one or more selected from amino groups and ammonium groups.

[0011] <4> The porous body according to <3>, 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.

[0012] <5> The porous body according to <3>, wherein the solid organic compound is a styrene copolymer having one or more selected from amino groups and ammonium groups, and / or an acrylic copolymer having one or more selected from amino groups and ammonium groups.

[0013] <6> The porous body according to any one of <1> to <5>, wherein the porous body further contains one or more selected from organic binders and inorganic binders.

[0014] <7> The porous body according to any one of <1> to <6>, wherein the porous body is a honeycomb structure having an outer peripheral wall and partition walls disposed inside the outer peripheral wall that divide a plurality of cells extending from an inlet end face to an outlet end face.

[0015] <8> The porous body according to any one of <1> to <7>, wherein the greenhouse gas is carbon dioxide.

[0016] <9> A gas recovery device comprising a porous body described in any one of <1> to <8>.

[0017] According to the present invention, it is possible to provide a porous body and a gas recovery device that have excellent greenhouse gas adsorption performance even when wet.

[0018] This is a schematic diagram of an end face perpendicular to the direction in which the cells of a porous body according to an embodiment of the present invention extend. This is a schematic diagram of the cross-section along the line b-b' in Figure 1A.

[0019] The porous material of the present invention contains an adsorbent capable of adsorbing and desorbing greenhouse gases and is provided with pores. When the moisture content of the porous material is 40% by mass, the pore volume ratio of pores with a diameter greater than 1 μm is 20% or less, the pore volume ratio of pores with a diameter less than 0.1 μm is 20% or less, and the pore volume ratio of pores with a diameter of 0.1 to 1 μm is 60% or more. By having the above configuration, the porous material of the present invention can improve the adsorption performance of greenhouse gases even when wet. Here, "greenhouse gas adsorption performance" in this specification means both the amount of greenhouse gases adsorbed and the adsorption rate. Therefore, excellent greenhouse gas adsorption performance means that the amount of greenhouse gases adsorbed is large and the adsorption rate of greenhouse gases is fast.

[0020] The embodiments of the present invention will be described below in detail with reference to the drawings as necessary. The present invention is not limited to the following embodiments, and it should be understood that modifications, improvements, etc., to the following embodiments, based on the ordinary knowledge of those skilled in the art, without departing from the spirit of the invention, also fall within the scope of the present invention.

[0021] (1. Porous Body) The porous body according to the embodiment of the present invention can be suitably used to recover greenhouse gases contained in a treatment gas. The treatment gas is not particularly limited, but examples include exhaust gases emitted from factories and power plants, and the atmosphere. The exhaust gas is not particularly limited, but examples include combustion exhaust gases generated when burning fossil fuels, coal gas obtained by gasifying coal, and natural gas at thermal power plants and steel mills. The greenhouse gas is not particularly limited, but examples include carbon dioxide (CO2), methane (CH4), nitrogen oxides such as nitrous oxide (N2O), hydrofluorocarbons, perfluorocarbons, and sulfur hexafluoride (SF6). Among these, the porous body according to the embodiment of the present invention is particularly useful for recovering carbon dioxide (CO2) contained in combustion exhaust gases and the atmosphere.

[0022] The porous body according to an embodiment of the present invention contains an adsorbent (hereinafter abbreviated as "adsorbent") capable of adsorbing and desorbing greenhouse gases, and is provided with pores. The pores are formed between the skeletal parts containing the adsorbent. With this configuration, greenhouse gases can easily come into contact with the adsorbent through the pores, thereby improving the amount of greenhouse gases adsorbed.

[0023] The pore size and pore volume ratio of a porous material are related to its greenhouse gas adsorption performance. Studies have shown that increasing the number of pores with a diameter of 0.1 to 1 μm is effective in improving greenhouse gas adsorption performance. Furthermore, since greenhouse gas adsorption often occurs under high humidity conditions, it is desirable to maintain a large number of pores with a diameter of 0.1 to 1 μm even when wet, taking into account the expansion of the adsorbent due to moisture. Therefore, in the porous material according to the embodiment of the present invention, when the moisture content of the porous material is 40% by mass, the pore volume ratio of pores with a diameter of 0.1 to 1 μm is set to 60% or more, preferably 65% ​​or more, more preferably 70% or more, and even more preferably 85% or more. By controlling the pore volume ratio of pores with a diameter of 0.1 to 1 μm within this range, the greenhouse gas adsorption performance can be improved even when wet. Furthermore, when the moisture content of the porous material is 40% by mass, the pore volume fraction of pores with a diameter of 0.1 to 1 μm tends to improve the greenhouse gas adsorption performance as the higher the pore volume fraction, so there is no particular upper limit, but it is typically 99% or less, preferably 98% or less. Here, in this specification, "pore diameter" means the pore diameter in the pore distribution determined by the mercury intrusion method in accordance with JIS R1655:2003. In addition, the pore volume when the moisture content of the porous material is 40% by mass can be measured by freeze-drying the porous material with a moisture content of 40% by mass (specifically, freezing for 4 days followed by vacuum drying for 3 days) and using a mercury porosimeter by the mercury intrusion method in accordance with JIS R1655:2003.

[0024] Furthermore, when the number of pores with a diameter exceeding 1 μm increases, the treated gas containing greenhouse gases flows more easily through the pores, but the contact area between the treated gas and the adsorbent decreases, which tends to reduce the greenhouse gas adsorption performance (specifically, the amount adsorbed per unit volume decreases). In addition, the strength of the porous body also tends to decrease. Moreover, since the adsorption of greenhouse gases often occurs under high humidity conditions, it is necessary to maintain the pore volume ratio of pores with a diameter exceeding 1 μm within an appropriate range even when wet, taking into account the expansion of the adsorbent due to moisture.Therefore, in the porous body according to the embodiment of the present invention, when the moisture content of the porous body is 40% by mass, the pore volume ratio of pores with a diameter exceeding 1 μm is set to 20% or less, preferably 15% or less, and more preferably 10% or less.By controlling the pore volume ratio of pores with a diameter exceeding 1 μm within this range, the decrease in greenhouse gas adsorption performance can be suppressed even when wet. Furthermore, the lower limit of the pore volume fraction for pores with a diameter exceeding 1 μm is not particularly limited, as a smaller pore volume fraction suppresses the decrease in greenhouse gas adsorption performance. However, it is typically 1% or more, preferably 3% or more.

[0025] Furthermore, when the number of pores with a diameter of less than 0.1 μm increases, it becomes difficult for the treated gas containing greenhouse gases to flow through the pores, which tends to reduce the greenhouse gas adsorption performance (specifically, the amount of adsorption per unit mass and the adsorption rate decrease). Also, since greenhouse gas adsorption often occurs under high humidity conditions, it is necessary to maintain the pore volume ratio of pores with a diameter of less than 0.1 μm within an appropriate range even when wet, taking into account the expansion of the adsorbent due to moisture.Therefore, in the porous body according to the embodiment of the present invention, when the moisture content of the porous body is 40% by mass, the pore volume ratio of pores with a diameter of less than 0.1 μm is set to 20% or less, preferably 15% or less, and more preferably 10% or less.By controlling the pore volume ratio of pores with a diameter of less than 0.1 μm within this range, the decrease in greenhouse gas adsorption performance can be suppressed even when wet. Furthermore, the lower limit of the pore volume fraction for pores with a diameter of less than 0.1 μm is not particularly limited, as a smaller pore volume fraction suppresses the decrease in greenhouse gas adsorption performance, but it is typically 1% or more, preferably 3% or more.

[0026] The adsorbent contained in the porous body according to the embodiment of the present invention forms the skeletal structure of the porous body. Since the porous body having such a structure is manufactured by molding a material containing the adsorbent, it can be manufactured without going through a firing process with a high heating temperature, compared to conventional methods in which the adsorbent is coated onto a substrate. For this reason, the porous body according to the embodiment of the present invention can reduce greenhouse gas emissions generated during manufacturing compared to conventional methods. In addition, the amount of adsorbent that can be supported can be increased, so the amount of greenhouse gas adsorbed can also be increased.

[0027] The adsorbent is not particularly limited as long as it is capable of adsorbing and desorbing greenhouse gases, and known adsorbents can be used. Among these, adsorbents include amino groups (one or more selected from -NH2, -NHR, -NRR' (R and R' represent organic groups)) and ammonium groups (-N + It is preferable that the solid organic compound has one or more selected from RR'R'' (where R and R', R'' represent organic groups). Although the present invention is not intended to be limited by theory, solid organic compounds having an amino group can adsorb greenhouse gases (especially carbon dioxide) by reacting with them to produce carbamates or bicarbonates. Similarly, solid organic compounds having an ammonium group can adsorb carbon dioxide by reacting with greenhouse gases (especially carbon dioxide) to produce bicarbonates.

[0028] Solid organic compounds having one or more groups selected from amino groups and ammonium groups are preferably water-insoluble from the viewpoint of water resistance. Furthermore, solid organic compounds having one or more groups selected from amino groups and ammonium groups are -NH2, -NHR, -NRR', -N + The solid organic compound may have any of RR'R" (where R, R', and R" represent organic groups), or it may have a combination of two or more of these. Among amino groups, it is particularly preferable to contain a primary amine (-NH2) as a functional group. The solid organic compound having one or more selected from amino groups and ammonium groups may also preferably contain an aromatic ring.

[0029] 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, styrene 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 can be used as solid organic compounds having one or more groups selected from amino groups and ammonium groups. These can be used individually or in combination of two or more. Examples of styrene copolymers having one or more groups selected from amino groups and ammonium groups include styrene-divinylbenzene copolymers. Examples of acrylic copolymers having one or more groups selected from amino groups and ammonium groups include (meth)acrylic acid-divinylbenzene copolymers. Strongly basic anion exchange resins having ammonium groups can be of the OH type, Cl type, HCO3 type, etc., but from the viewpoint of carbon dioxide adsorption performance, the OH type or HCO3 type is preferred. That is, the counteranion of the ammonium group is OH ― or HCO3 ― It is preferable.

[0030] The exchange capacity of a weakly basic anion exchange resin is preferably 0.6 meq / mL or more, more preferably 1.0 meq / mL or more, and even more preferably 1.4 meq / mL or more, from the viewpoint of greenhouse gas adsorption performance. The exchange capacity of a strongly basic anion exchange resin is preferably 0.6 meq / mL or more, and more preferably 1.0 meq / mL or more, from the viewpoint of carbon dioxide adsorption performance. Here, the exchange capacity of a weakly basic anion exchange resin is measured by the tap method, after treating 10 mL of ion exchange resin with hydrochloric acid, washing off excess hydrochloric acid with ethanol, and measuring the amount of chloride ions that leach out when ammonia water is flushed through. The exchange capacity of a strongly basic anion exchange resin is measured by the tap method, after treating 10 mL of ion exchange resin with hydrochloric acid, washing off excess hydrochloric acid with ethanol, and measuring the amount of chloride ions that leach out when sodium hydroxide aqueous solution is flushed through.

[0031] The adsorbent content in the porous body (skeleton) according to the embodiment of the present invention when dry (when the moisture content is 0% by mass) is not particularly limited, but is preferably 40 to 94% by mass, more preferably 50 to 92% by mass, and even more preferably 60 to 90% by mass. By setting the content within this range, the proportion of adsorbent can be increased, thereby improving the adsorption performance of greenhouse gases.

[0032] The porous body (skeleton) according to the embodiment of the present invention may further contain one or more binders selected from organic binders and inorganic binders. Furthermore, the strength of the porous body can be increased by including organic binders or inorganic binders.

[0033] Examples of organic binders include methylcellulose, hydroxypropyl methylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, carboxymethylcellulose, polyvinyl alcohol, hydroxyethyl methylcellulose, polyvinyl acetal, polyethylene oxide, polyvinyl butyral, polybutadiene, methacrylic acid esters, acrylics, ethylcellulose, silicones, and polyolefins. In particular, using water-soluble organic binders such as methylcellulose, hydroxypropyl methylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, carboxymethylcellulose, polyvinyl alcohol, hydroxyethyl methylcellulose, polyvinyl acetal, and polyethylene oxide can reduce environmental impact, the danger of organic solvent vapors during drying, and manufacturing costs.

[0034] Examples of inorganic binders include clay, diatomaceous earth, layered clay minerals, montmorillonite, hydrotalcite, activated clay, acid clay, hectorite, halloysite, attapulgite, silica, alumina, talc, chlorite, vermiculite, mica, illite, pyrophyllite, sericite, kaolin, sepiolite, boehmite, palygorskite, and bentonite.

[0035] The content of the organic binder in the porous body (skeleton) according to the embodiment of the present invention when dry (when the moisture content is 0% by mass) is not particularly limited, but is preferably 3 to 20% by mass, more preferably 5 to 15% by mass, and even more preferably 5 to 10% by mass. The content of the inorganic binder in the porous body (skeleton) according to the embodiment of the present invention when dry (when the moisture content is 0% by mass) is not particularly limited, but is preferably 0 to 55% by mass, more preferably 0 to 50% by mass, and even more preferably 0 to 40% by mass.

[0036] The porous body (skeleton) according to the embodiment of the present invention may further contain known additives such as surfactants and pore-forming materials, in addition to the above-mentioned components, to the extent that they do not impede the effects of the present invention. Specific examples of surfactants include ethylene glycol, dextrin, fatty acid soap, and polyalcohol. These can be used individually or in combination of two or more. Specific examples of pore-forming materials include wood powder, activated carbon, hollow resin, porous resin, hollow inorganic material, and porous inorganic material. These can be used individually or in combination of two or more.

[0037] The shape of the porous body according to the embodiment of the present invention is not particularly limited, but a honeycomb shape is preferred. Here, Figure 1A shows a schematic diagram of the end face perpendicular to the direction in which the cells of the porous body having a honeycomb shape extend, and Figure 1B shows a schematic diagram of the cross section of line b-b' in Figure 1A (a cross section parallel to the direction in which the cells extend). The porous body shown in Figures 1A and 1B is a honeycomb structure 10 having an outer peripheral wall 11 and partition walls 15 disposed inside the outer peripheral wall 11 and forming partitions for a plurality of cells 14 extending from the inlet end face 12 to the outlet end face 13. The adsorbent is contained in the outer peripheral wall 11 and the partition walls 15. The honeycomb structure 10 is a flow-through type with both end faces (inlet end face 12 and outlet end face 13) of each cell 14 open. When a processed gas containing greenhouse gases (for example, air) flows in from the inlet end face 12, which has inlets for multiple cells 14, the greenhouse gases are adsorbed as the gas passes through the multiple cells 14, and the gas with a reduced concentration of greenhouse gases flows out from the outlet end face 13, which has outlets for multiple cells 14.

[0038] The end face shape of the honeycomb structure 10 is not particularly limited. For example, it can be a round shape such as a circular shape, an elliptical shape, a racetrack shape, and an oval shape, a polygonal shape such as a triangular shape and a square shape, and other irregular shapes. However, considering the ease of installation in the reactor, a square shape is preferred. The outer shape of the honeycomb structure 10 can typically be columnar. Note that the honeycomb structure 10 shown in FIGS. 1A and 1B has a square end face shape and is an example of a square prism as a whole.

[0039] The length of the honeycomb structure 10 in the direction in which the cells 14 extend (the length from the inflow end face 12 to the outflow end face 13) is not particularly limited and may be appropriately set according to the application and required performance. However, while a larger length in the direction in which the cells 14 of the honeycomb structure 10 extend can increase the adsorption amount of greenhouse gases, if it is too large, the pressure loss will increase. 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.

[0040] The diameter of each end face of the honeycomb structure 10 is not particularly limited and may be appropriately set according to the application and required performance. However, while a larger diameter of each end face of the honeycomb structure 10 can increase the adsorption amount of greenhouse gases, if it is too large, the manufacturing difficulty will increase. 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 10 in this specification means the diameter if it is circular, and the equivalent diameter of a circle if it is other than circular.

[0041] The thickness of the outer peripheral wall 11 is not particularly limited, but from the viewpoint of ensuring strength, it 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. Note that the thickness of the outer peripheral wall 11 in this specification refers to the length in the normal direction of the outer peripheral surface from the boundary between the outer peripheral wall 11 and the outermost peripheral cell 14 or partition wall 15 to the outer peripheral surface of the honeycomb structure 10 in a cross section orthogonal to the direction in which the cells 14 extend.

[0042] The thickness of the partition wall 15 is not particularly limited, but from the viewpoint of ensuring strength, it is preferably 50 μm or more, more preferably 80 μm or more, and still more preferably 100 μm or more. Also, from the viewpoint of suppressing pressure loss, the thickness of the partition wall 15 is preferably 50 to 600 μm, more preferably 80 to 550 μm, and still more preferably 100 to 500 μm. In the present specification, the thickness of the partition wall 15 is defined as the length of the portion passing through the partition wall 15 among the line segments connecting the centers of gravity of adjacent cells 14 in a cross section orthogonal to the direction in which the cell 14 extends. Also, the thickness of the partition wall 15 refers to the average value of the thicknesses of all the partition walls 15 of the honeycomb structure 10.

[0043] It is preferable that the thickness of the outer peripheral wall 11 and the partition wall 15 is the same. By adopting such a configuration, it is possible to suppress an increase in pressure loss and increase the adsorption amount of greenhouse gases while ensuring the strength of the honeycomb structure 10.

[0044] The cell density (the number of cells 14 per unit cross-sectional area) of the honeycomb structure 10 is not particularly limited, but is preferably 8 to 124 cells / cm 2 and more preferably 16 to 62 cells / cm 2 . By controlling the cell density within such a range, it becomes easier to obtain an effect of suppressing an increase in pressure loss, an effect of improving mechanical strength, and an effect of increasing the adsorption amount of greenhouse gases. If the cell density is less than 8 cells / cm 2 , the mechanical strength and the adsorption amount of greenhouse gases are likely to decrease. Also, if the cell density exceeds 124 cells / cm 2 , the pressure loss is likely to increase. Here, in the present specification, the cell density is calculated by dividing the number of cells 14 possessed by the honeycomb structure 10 by the area of one end face excluding the outer peripheral wall 11 of the honeycomb structure 10.

[0045] The shape of the cells 14 in a cross-section perpendicular to the direction in which the cells 14 of the honeycomb structure 10 extend is not particularly limited, but is preferably a square, hexagon, octagon, circle, or a combination thereof. Among these, the shapes of the cells 14 are preferably square and hexagonal. By shaping the cells 14 in this way, the increase in pressure loss when a processing gas is passed through the honeycomb structure 10 can be suppressed.

[0046] (2. Method for recovering and desorbing greenhouse gases) The method for recovering and desorbing greenhouse gases according to the embodiment of the present invention is carried out using the porous body described above. Specifically, the method for recovering greenhouse gases according to the embodiment of the present invention includes bringing a treatment gas containing greenhouse gases into contact with a porous body (for example, flowing it into the cells 14 of the honeycomb structure 10) and adsorbing the greenhouse gases in the treatment gas with an adsorbent between them.

[0047] Furthermore, the greenhouse gas desorption method according to the embodiment of the present invention includes contacting a desorption gas or heated desorption gas with a porous body on which greenhouse gases have been adsorbed (for example, by flowing it through the cells 14 of the honeycomb structure 10), and during this time, the greenhouse gases are desorbed from the adsorbent into the desorption gas. Here, the desorption gas is not particularly limited as long as it is a gas capable of desorbing carbon dioxide, but for example, water vapor can be used. The water vapor is preferably at a high temperature of 80°C or higher. The desorption gas may be heated by a heater or by mixing it with a high-temperature gas.

[0048] (3. Method for Manufacturing a Porous Body) The method for manufacturing a porous body according to the embodiment of the present invention is not particularly limited as long as it is a method capable of manufacturing the above-described porous body. Below, as an example, a method suitable for manufacturing a honeycomb-shaped porous body will be described.

[0049] The honeycomb structure 10 is manufactured by a method that includes a clay preparation step (first step), a molding step into a honeycomb molded body (second step), and a drying step for the honeycomb molded body (third step).

[0050] The clay preparation process (first step) is a process of preparing clay by kneading a molding raw material containing an adsorbent, an organic binder, and an inorganic binder. The molding raw material may further contain a solvent. The solvent (dispersion medium) is not particularly limited and can be water, or a mixed solvent of water and an organic solvent such as alcohol, but water can be used particularly suitably.

[0051] The content of adsorbents excluding the solvent in the molding raw material is preferably 40 to 94% by mass, more preferably 50 to 92% by mass, and even more preferably 60 to 90% by mass, from the viewpoint of achieving a good balance of greenhouse gas adsorption performance, crack suppression during drying, and water resistance. Similarly, the content of organic binders excluding the solvent in the molding raw material is preferably 3 to 20% by mass, more preferably 5 to 15% by mass, and even more preferably 5 to 10% by mass. Furthermore, the content of inorganic binders excluding the solvent in the molding raw material is preferably 0 to 55% by mass, more preferably 0 to 50% by mass, and even more preferably 0 to 40% by mass. The solvent content in the molding raw material is adjusted to produce a clay with a hardness suitable for molding (especially extrusion molding).

[0052] The pore diameter and pore volume ratio of a porous material can be controlled by adjusting the components used in the molding raw material and their content. For example, by selecting and using a porous inorganic binder such as diatomaceous earth and adjusting its content, the pore diameter and pore volume ratio of the porous material can be controlled. Specifically, by increasing the pore diameter of the porous inorganic binder, the pore diameter of the porous material can be increased, and by increasing the content of the inorganic binder, the pore volume ratio of large pores in the porous material can be increased. Conversely, by decreasing the pore diameter of the porous inorganic binder, the pore diameter of the porous material can be decreased, and by increasing the content of the inorganic binder, the pore volume ratio of small pores in the porous material can be increased. Furthermore, the pore diameter and pore volume ratio can also be controlled by controlling the average particle size and content of the adsorbent. Specifically, increasing the average particle size of the adsorbent can increase the pore diameter of the porous material, and increasing the adsorbent content can increase the pore volume ratio of large pores in the porous material. Conversely, decreasing the average particle size of the adsorbent can decrease the pore diameter of the porous material, and increasing the adsorbent content can increase the pore volume ratio of small pores in the porous material.

[0053] While known kneaders can be used to knead molding materials containing the above-mentioned components, it is desirable to knead them for the time necessary for each component to be uniformly distributed in the clay.

[0054] The second step involves forming a honeycomb molded body from the clay obtained in the first step. Specifically, in the second step, a honeycomb molded body is extruded, having an outer periphery wall 11 and partition walls 15 disposed inside the outer periphery wall 11, which divide and form a plurality of cells 14 extending from the inlet end face 12 to the outlet end face 13. For extrusion molding, a die having the desired overall shape, cell shape, partition wall thickness, cell density, etc., can be used.

[0055] The drying step (third step) of the honeycomb molded body is a step of drying the honeycomb molded body obtained in the second step. Since the honeycomb molded body immediately after molding contains a solvent, the solvent is removed by drying. For drying, conventional known drying methods such as hot air drying, microwave drying, dielectric drying, reduced pressure drying, vacuum drying, and freeze drying can be used. Among these, hot air drying, microwave drying, dielectric drying, or a drying method combining these is preferred because it can dry the entire honeycomb molded body quickly and uniformly. From the viewpoint of suppressing the decomposition of the adsorbent and organic binder, it is preferable to dry the honeycomb molded body in an atmospheric atmosphere of 20 to 150°C, more preferably in an atmospheric atmosphere of 30 to 140°C, and even more preferably in an atmospheric atmosphere of 40 to 130°C.

[0056] In the drying process of the honeycomb molded body, the pore diameter and pore volume ratio of the pores in the honeycomb structure 10 (porous body) can be controlled by controlling the drying method for the honeycomb molded body. Specifically, by slowing down the drying rate of the honeycomb molded body, the amount of shrinkage of the honeycomb molded body is reduced, and thus the pore volume ratio of large pores in the honeycomb structure 10 (porous body) can be increased. Conversely, by increasing the drying rate of the honeycomb molded body, the pore volume ratio of small pores in the honeycomb structure 10 (porous body) can be increased. Furthermore, the pore diameter and pore volume ratio of the pores in the honeycomb structure 10 (porous body) can also be controlled by controlling the drying time for the porous body. Specifically, by shortening the drying time of the honeycomb molded body, the amount of shrinkage of the honeycomb molded body is reduced, and thus the pore volume ratio of large pores in the honeycomb structure 10 (porous body) can be increased. Conversely, by increasing the drying time of the honeycomb molded body, the pore volume ratio of small pores in the honeycomb structure 10 (porous body) can be increased.

[0057] (4. Gas Recovery Apparatus) The gas recovery apparatus according to the embodiment of the present invention includes the porous body described above. Because this gas recovery apparatus is equipped with the porous body described above, it has excellent greenhouse gas adsorption performance even when wet.

[0058] A gas recovery device according to an embodiment of the present invention may further include a housing that contains a porous body. Preferably, the housing is connected to pipes that can supply and discharge a processed gas containing greenhouse gases and a desorbed gas. With a gas recovery device having such a structure, the recovery and desorption of greenhouse gases can be easily achieved.

[0059] The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples.

[0060] <Materials Used> As an adsorbent, a commercially available water-insoluble, weakly basic anion exchange resin (styrene-based divinylbenzene polymer having a primary amine as a functional group with an exchange capacity of 2.0 meq / mL) was prepared. The adsorbent was pulverized in a ball mill to prepare several types with different average particle sizes. Methylcellulose was prepared as an organic binder. Sepiolite and diatomaceous earth were prepared as inorganic binders. Several types of diatomaceous earth with different pore sizes were prepared. Industrial water was prepared as a solvent.

[0061] When the water content of the honeycomb structure is 40% by mass, the pore volume ratio of each pore diameter is as shown in Table 1. The raw materials used (adsorbent, organic binder, inorganic binder, and solvent) were selected and blended to obtain a molding raw material. The content of the adsorbent excluding the solvent in the molding raw material was 70% by mass, the content of the organic binder excluding the solvent in the molding raw material was in the range of 3 to 20% by mass, and the content of the inorganic binder excluding the solvent in the molding raw material was adjusted in the range of 0 to 55% by mass, respectively. Also, the blending amount of the solvent was adjusted so that the clay had a hardness suitable for molding. By using diatomaceous earth with a large pore diameter, the pore diameter of the honeycomb structure can be increased, and by increasing the content of the diatomaceous earth, the pore volume ratio of the large pore diameter in the honeycomb structure can be increased. Conversely, by using diatomaceous earth with a small pore diameter, the pore diameter of the honeycomb structure can be decreased, and by increasing the content of the diatomaceous earth, the pore volume ratio of the small pore diameter in the porous body can be increased. Also, by using an adsorbent with a large average particle size, the pore diameter of the honeycomb structure can be increased, and by increasing the content of the adsorbent, the pore volume ratio of the large pore diameter in the honeycomb structure can be increased. Conversely, by using an adsorbent with a small average particle size, the pore diameter of the honeycomb structure can be decreased, and by increasing the content of the adsorbent, the pore volume ratio of the small pore diameter in the honeycomb structure can be increased.

[0062] 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 dried honeycomb molded body (honeycomb structure) would satisfy the following conditions. Outer shape: Square columnar Cross-sectional shape of cells: Square Length in the direction in which the cells extend: 150 mm Diameter of each end face: 40 mm Thickness of partition walls: 315 μm Cell density: 46.5 cells / cm 2

[0063] Next, the obtained honeycomb molded body was subjected to high-frequency dielectric drying, then dried in a microwave dryer at 100°C in an atmospheric environment for 2 minutes, and a predetermined amount was cut from both end faces to produce a honeycomb structure. By slowing down the drying rate of the honeycomb molded body, the amount of shrinkage of the honeycomb molded body is reduced, thereby increasing the pore volume ratio of large pores in the honeycomb structure. Conversely, by increasing the drying rate of the honeycomb molded body, the pore volume ratio of small pores in the honeycomb structure can be increased. Also, by shortening the drying time of the honeycomb molded body, the amount of shrinkage of the honeycomb molded body is reduced, thereby increasing the pore volume ratio of large pores in the honeycomb structure. Conversely, by lengthening the drying time of the honeycomb molded body, the pore volume ratio of small pores in the honeycomb structure can be increased.

[0064] Next, the honeycomb structure obtained above was evaluated as follows.

[0065] <Pore Diameter and Pore Volume Percentage at a Moisture Content of 40% by Mass> After adjusting the moisture content of the honeycomb structure to 40% by mass by leaving it in a humid atmosphere, freeze-drying was performed by freezing for 4 days followed by vacuum drying for 3 days. For the freeze-dried honeycomb structure, the pore volume of each pore size was measured using a mercury porosimeter (Autopore IV9500, Micromeritix). For example, the pore volume (mL / g) for pores with a diameter of 0.1 μm was obtained by subtracting the cumulative pore volume for a pore diameter of 0.1 μm from the cumulative pore volume for a pore diameter of 1 μm. The pore volume percentage for pores with a diameter of 0.1 to 1 μm was calculated as the percentage of the pore volume for pores with a diameter of 0.1 to 1 μm relative to the total pore volume. Total pore volume (mL / g) refers to the total volume of pores per gram of the honeycomb structure. Furthermore, the pore volume and pore volume ratio for other pore sizes were determined in the same manner as described above.

[0066] <CO2 Adsorption Amount> Since it is difficult to directly evaluate the amount of CO2 adsorbed by the honeycomb structure when it is wet, a sample with the structure of the honeycomb structure when wet was prepared and the amount of CO2 adsorbed was evaluated. Specifically, the procedure was carried out as follows: A rectangular parallelepiped sample measuring 20 mm × 20 mm × 40 mm (length in the direction in which the cells extend) was cut from near the center of the honeycomb structure. This sample (honeycomb structure) was left to stand in a humid atmosphere to adjust the moisture content to 40% by mass, and freeze-drying was performed by freezing for 4 days followed by vacuum drying for 3 days. After this freeze-dried sample was placed in a holder and placed in a sealed container, CO2 sensors were installed on the inlet and outlet sides of the honeycomb structure, respectively. Next, as a pretreatment, nitrogen gas heated to 90°C to 100°C was flowed through the honeycomb structure at a flow rate of 1.5 L / min until the CO2 concentration on the outlet side became 0 ppm. After that, heating was stopped while the nitrogen gas flow continued until the temperature dropped to 25°C (room temperature). After reaching 25°C, CO2 adsorption was started by flowing 25°C air at a flow rate of 15 L / min, and the amount of CO2 adsorbed until saturation was reached was measured. By dividing the measured amount of CO2 adsorbed by the mass of the honeycomb structure, the amount of CO2 adsorbed per unit mass of the honeycomb structure [mol / kg] was calculated. Furthermore, by dividing the measured amount of CO2 adsorbed by the mass of the honeycomb structure, the amount of CO2 adsorbed per unit volume of the honeycomb structure [mol / m³] was calculated. 3 They sought ].

[0067] The amount of CO2 adsorbed per unit mass of the honeycomb structure was evaluated by comparing it to the CO2 adsorption amount of Comparative Example 1, using the result of the CO2 adsorption amount of Comparative Example 1 as the baseline. The evaluation results are expressed by the following indicators: ×: The CO2 adsorption amount is at or above the baseline, or the increase in CO2 adsorption amount is 0% or more but less than 2% compared to the baseline. △: The increase in CO2 adsorption amount is 2% or more but less than 4% compared to the baseline. ○: The increase in CO2 adsorption amount is 4% or more compared to the baseline. Note that for each CO2 adsorption amount, an evaluation result of ○ or △ indicates a passing grade (high CO2 adsorption amount).

[0068] <CO2 Adsorption Rate> Since it is difficult to directly evaluate the CO2 adsorption rate of the honeycomb structure when it is wet, a sample with the structure of the honeycomb structure when wet was prepared and the CO2 adsorption rate was evaluated. Specifically, the procedure was carried out as follows: A rectangular parallelepiped sample measuring 20 mm × 20 mm × 40 mm (length in the direction in which the cells extend) was cut from near the center of the honeycomb structure. This sample (honeycomb structure) was left to stand in a humid atmosphere to adjust the moisture content to 40% by mass, and freeze-drying was performed by freezing for 4 days followed by vacuum drying for 3 days. After this freeze-dried sample was placed in a holder and placed in a sealed container, CO2 sensors were installed on the inlet and outlet sides of the honeycomb structure, respectively. Next, as a pretreatment, nitrogen gas heated to 90°C to 100°C was flowed through the honeycomb structure at a flow rate of 1.5 L / min until the CO2 concentration on the outlet side became 0 ppm. After that, heating was stopped while the nitrogen gas flow continued until the temperature dropped to 25°C (room temperature). After reaching 25°C, CO2 adsorption was started by flowing 25°C air at a flow rate of 15 L / min, and the amount of CO2 adsorbed was measured after 10 minutes. The amount of CO2 adsorbed per unit mass of the honeycomb structure [mol / kg] was calculated by dividing the measured amount of CO2 adsorbed by the mass of the honeycomb structure, and the CO2 adsorption rate (mol / (kg·min)) was calculated by further dividing the amount of CO2 adsorbed per unit mass by the CO2 adsorption time (10 minutes).

[0069] The CO2 adsorption rate was evaluated by using the result of Comparative Example 3 as the baseline and measuring the increase rate relative to this baseline. The evaluation results are expressed by the following indicators: ×: The result is at or above the baseline, or the increase rate of the CO2 adsorption rate relative to the baseline is 0% or more but less than 2%. △: The increase rate of the CO2 adsorption rate relative to the baseline is 2% or more but less than 4%. ○: The increase rate of the CO2 adsorption rate relative to the baseline is 4% or more. Note that for each CO2 adsorption rate evaluation result, ○ or △ indicates a passing grade (fast CO2 adsorption rate).

[0070] <Strength> The honeycomb structure was left in a humid atmosphere to adjust the moisture content to 40% by mass. A weight of 1 kg (equivalent to the mass of approximately 4 honeycomb structures (when dry)) was placed on it (the width of the weight was the same as the width of the honeycomb structure) and left for about 30 seconds. The same weight was placed on the other three sides, and the presence or absence of cracks or other damage was visually checked. The evaluation results are expressed by the following index: ×: Five or more cracks or other damage were confirmed. △: Cracks or other damage were confirmed, but there were fewer than five (usable level). ○: No cracks or other damage were confirmed.

[0071] The results of each of the above evaluations are shown in Table 1.

[0072]

[0073] As shown in Table 1, the honeycomb structures (porous materials) of Examples 1 to 9, which had a moisture content of 40% by mass, with a pore volume ratio of 20% or less for pores larger than 1 μm, 20% or less for pores smaller than 0.1 μm, and 60% or more for pores between 0.1 and 1 μm, showed good CO2 adsorption amount and CO2 adsorption rate evaluation results, demonstrating excellent CO2 adsorption performance in wet conditions. Furthermore, the honeycomb structures (porous materials) of Examples 1 to 9 also exhibited good strength. In contrast, the honeycomb structure (porous material) of Comparative Example 1 had a pore volume ratio of over 20% for pores smaller than 0.1 μm, resulting in low CO2 adsorption. The honeycomb structure (porous material) of Comparative Example 2 had a pore volume ratio of over 20% for pores larger than 1 μm, resulting in low CO2 adsorption and insufficient strength. The honeycomb structure (porous material) of Comparative Example 3 had a pore volume ratio of over 20% for pores with a diameter of less than 0.1 μm and a pore volume ratio of less than 60% for pores with a diameter of 0.1 to 1 μm, resulting in low CO2 adsorption and a slow CO2 adsorption rate. The honeycomb structure (porous material) of Comparative Example 4 had a pore volume ratio of over 20% for pores with a diameter of less than 0.1 μm and over 20% for pores with a diameter of more than 1 μm, and a pore volume ratio of less than 60% for pores with a diameter of 0.1 to 1 μm, resulting in low CO2 adsorption and insufficient strength. The honeycomb structure (porous material) of Comparative Example 5 had a pore volume ratio of over 20% for pores with a diameter of more than 1 μm, resulting in low CO2 adsorption and a slow CO2 adsorption rate. Furthermore, its strength was also insufficient.

[0074] As can be seen from the above results, the present invention provides a porous body and a gas recovery device that have excellent greenhouse gas adsorption performance even when wet.

[0075] 10 Honeycomb structure 11 Outer wall 12 Inlet end face 13 Outlet end face 14 Cell 15 Partition wall

Claims

1. A porous body having pores and containing an adsorbent capable of adsorbing and desorbing greenhouse gases, wherein when the moisture content of the porous body is 40% by mass, the pore volume ratio of pores with a diameter greater than 1 μm is 20% or less, the pore volume ratio of pores with a diameter less than 0.1 μm is 20% or less, and the pore volume ratio of pores with a diameter of 0.1 to 1 μm is 60% or more.

2. The porous body according to claim 1, wherein the pores have a pore volume ratio of 10% or less for pores with a diameter of 1 μm, a pore volume ratio of 10% or less for pores with a diameter of less than 0.1 μm, and a pore volume ratio of 85% or more for pores with a diameter of 0.1 to 1 μm.

3. The porous body according to claim 1 or 2, wherein the adsorbent is a solid organic compound having one or more selected from amino groups and ammonium groups.

4. The porous body according to claim 3, 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.

5. The porous body according to claim 3, wherein the solid organic compound is a styrene copolymer having one or more selected from amino groups and ammonium groups, and / or an acrylic copolymer having one or more selected from amino groups and ammonium groups.

6. The porous body according to claim 1 or 2, wherein the porous body further contains one or more selected from organic binders and inorganic binders.

7. The porous body according to claim 1 or 2, wherein the porous body is a honeycomb structure having an outer peripheral wall and partition walls disposed inside the outer peripheral wall and forming a plurality of cells extending from an inlet end face to an outlet end face.

8. The porous body according to claim 1 or 2, wherein the greenhouse gas is carbon dioxide.

9. A gas recovery apparatus comprising the porous body described in claim 1 or 2.

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