Adsorbent

Abstract

To provide an adsorbent including a metal organic structure and suitable for improving durability.SOLUTION: An adsorbent 10 includes: a body part 11 including a metal organic structure; and a coating layer 12 coating a surface 11s of the body part 11 and including a resin. The body part 11 satisfies at least one selected from a group including (i) to (iii): (i) the body part 11 is a molded body; (ii) a cubic volume of the body part is 0.004 mm3 or more; and (iii) the body part has a sheet shape.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an adsorbent, and in particular to an adsorbent comprising a metal-organic framework. [Background technology]

[0002] In recent years, in view of environmental regulations and the like, attention has been focused on technologies for separating and recovering individual components from mixed gases. For example, in factories, power plants, and the like, mixed gases containing carbon dioxide, nitrogen, and the like are discharged from combustion equipment. For example, Patent Document 1 describes a gas storage container for storing recovered gases such as carbon dioxide. The inside of the gas storage container is filled with a porous material as an adsorbent for adsorbing the gas. An example of the porous material given is a metal organic framework.

[0003] Furthermore, in recent years, carbon capture and storage (CCS) and carbon capture and utilization (CCU) have been considered in order to reduce the amount of carbon dioxide in the atmosphere. In CCS and CCU, carbon dioxide is sometimes captured by separating it from the atmosphere. As a method for separating acidic gases such as carbon dioxide from the atmosphere, an adsorption method has been developed in which the acidic gas is adsorbed onto an adsorbent for separation. The adsorbent used in the adsorption method can adsorb acidic gases, for example, by contacting the atmosphere. For example, Patent Document 2 describes an adsorbent in which an amine compound is filled into the pores of a porous body. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2019 / 026872 [Patent Document 2] Japanese Patent Application Laid-Open No. 2015-9185 Summary of the Invention [Problem to be solved by the invention]

[0005] Metal-organic frameworks have a larger adsorption capacity per volume than other porous adsorbents. They also have high repetitive adsorption and desorption performance. Therefore, metal-organic frameworks are expected to be used as adsorbents for gas adsorption. However, metal-organic frameworks are known to have poor stability against water and high temperatures, posing challenges in terms of durability.

[0006] Therefore, an object of the present invention is to provide an adsorbent that includes a metal-organic framework and is suitable for improving durability. [Means for solving the problem]

[0007] The present invention provides a main body including a metal-organic framework; a coating layer that coats the surface of the main body and contains a resin; Equipped with The present invention provides an adsorbent in which the main body satisfies at least one selected from the group consisting of the following (i) to (iii): (i) The main body is a molded body. (ii) the volume of the main body is 0.004 mm 3 That's all. (iii) The main body portion has a sheet shape. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide an adsorbent that includes a metal-organic framework and is suitable for improving durability. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic diagram showing an example of the adsorbent of the present invention. [Figure 2] FIG. 2 is a schematic cross-sectional view of the adsorbent of FIG. [Figure 3] FIG. 3 is a plan view of a cylindrical pellet prepared in the example. DETAILED DESCRIPTION OF THE INVENTION

[0010] The adsorbent according to the first aspect of the present invention comprises: a main body including a metal-organic framework; a coating layer that coats the surface of the main body and contains a resin; Equipped with The main body satisfies at least one selected from the group consisting of the following (i) to (iii): (i) The main body is a molded body. (ii) the volume of the main body is 0.004 mm 3 That's all. (iii) The main body portion has a sheet shape.

[0011] In a second aspect of the present invention, for example, in the adsorbent according to the first aspect, the metal organic framework has a metal ion, a metal cluster, or a metal oxide cluster as a core, and bidentate or higher organic ligands.

[0012] In a third aspect of the present invention, for example, in the adsorbent according to the first or second aspect, the minimum thickness of the coating layer is in the range of 300 nm or more and 900 μm or less.

[0013] In a fourth aspect of the present invention, for example, in the adsorbent according to any one of the first to third aspects, the resin comprises a thermoplastic resin.

[0014] In a fifth aspect of the present invention, for example, in the adsorbent according to the fourth aspect, the thermoplastic resin is at least one selected from the group consisting of elastomers and polyvinyl resins.

[0015] In a sixth aspect of the present invention, for example, in the adsorbent according to the fifth aspect, the elastomer comprises at least one selected from the group consisting of butyl rubber, butadiene rubber, styrene butadiene rubber, isoprene rubber, and nitrile rubber.

[0016] In a seventh aspect of the present invention, for example, in the adsorbent according to the fifth aspect, the polyvinyl resin comprises at least one selected from the group consisting of polyvinyl alcohol and polyvinyl acetal.

[0017] In an eighth aspect of the present invention, for example, in an adsorbent according to any one of the first to seventh aspects, the resin comprises a monomer unit A having a substituent other than a carboxyl group, a hydroxyl group, and an aldehyde group on its side chain, and the ratio of the amount of substance of the monomer unit A to the total amount of substance of all monomer units contained in the resin is in the range of 35 mol% or more and 80 mol% or less.

[0018] In a ninth aspect of the present invention, for example, in the adsorbent according to any one of the first to eighth aspects, the mass ratio of the main body to the coating layer in the adsorbent is in the range of 99:1 to 30:70.

[0019] The present invention will be described in detail below, but the following description is not intended to limit the present invention to a specific embodiment.

[0020] <Embodiments of the adsorbent> The adsorbent of this embodiment comprises a main body containing a metal-organic framework (hereinafter sometimes referred to as "MOF") and a coating layer containing a resin that coats the surface of the main body. The main body satisfies at least one selected from the group consisting of the following (i) to (iii): (i) The main body is a molded body. (ii) The volume of the main body is 0.004 mm 3 That's all. (iii) The main body has a sheet shape.

[0021] If MOF powder particles are coated with resin in an attempt to improve the durability of the MOF, the resin may penetrate into the pores of the MOF, resulting in a decrease in adsorption performance. In contrast, in the adsorbent of this embodiment, the main body satisfies at least one selected from the group consisting of (i) to (iii) above, so that less MOF is exposed to the outside compared to the same amount of MOF powder particles, and the penetration of resin into the pores of the MOF is suppressed. Therefore, the adsorbent of this embodiment has improved durability while suppressing a decrease in adsorption performance.

[0022] In this specification, the term "molded body" refers to a body having a certain shape formed by agglomerating powder particles with physical force. A "molded body" is distinguished from secondary particles formed by simple agglomeration of powder particles. A "molded body" can also be referred to as a powder compact, pellet, tablet, etc.

[0023] An adsorbent satisfying the above condition (i) is suitable for use in, for example, a gas storage container for storing gases such as carbon dioxide recovered from exhaust gas. However, an adsorbent satisfying the above condition (i) may also be used in, for example, a gas separation device equipped with a gas adsorbent for separating acidic gases such as carbon dioxide contained in the atmosphere.

[0024] In this specification, the term "sheet shape" refers to a shape in which the thickness of the main body is smaller than the extent of the main body in a two-dimensional direction perpendicular to the thickness direction. The term "sheet shape" can also be referred to as a film shape, a flat plate shape, etc.

[0025] An adsorbent satisfying the above condition (iii) is preferably used in, for example, a gas separation device equipped with a gas adsorbent that separates acidic gases such as carbon dioxide contained in the atmosphere. However, an adsorbent satisfying the above condition (iii) may also be used in, for example, a gas storage container that stores gases such as carbon dioxide recovered from exhaust gas.

[0026] FIG. 1 is a schematic diagram showing an example of an adsorbent according to this embodiment. FIG. 2 is a schematic cross-sectional view of the adsorbent shown in FIG. 1. The adsorbent 10 shown in FIG. 1 includes a main body 11 and a coating layer 12 that coats a surface 11s of the main body 11. The main body 11 contains MOFs. Since the main body 11 contains MOFs, it has excellent adsorption performance. The coating layer 12 contains a resin. The coating layer 12 improves the durability of the adsorbent 10.

[0027] In the example shown in Fig. 1, the main body 11 satisfies the above condition (i). That is, in the example shown in Fig. 1, the main body 11 is a molded body. However, the main body 11 is not limited to the one exemplified in Fig. 1. The main body 11 may also satisfy the above condition (iii). That is, the main body 11 may have a sheet shape.

[0028] When the main body 11 is a molded body, the shape of the main body 11 is not particularly limited. Examples of the shape of the main body 11 include columnar shapes such as a disk, a cylinder, a prism, and a polygonal cylinder; and spherical shapes such as a sphere and an oblate sphere. In the example shown in Fig. 1, the main body 11 is disk-shaped.

[0029] The volume of the main body 11 can be determined, for example, based on an SEM image, as described below. First, a cross section of the adsorbent 10 is observed using a scanning electron microscope (SEM). The SEM image should pass through the center of gravity of the adsorbent 10 and include the entire adsorbent 10. For example, if the main body 11 is disk-shaped, the volume of the main body 11 can be determined by defining the length L1 of the bottom portion measured in the SEM image as the diameter and the length L2 of the side portion as the height, as shown in FIG. 2. The volume of the main body 11 can also be measured using a known 3D scanner for the adsorbent 10 after removing the coating layer 12 from the adsorbent 10 using a solvent.

[0030] The main body 11 may further satisfy the above condition (ii). That is, the volume of the main body 11 is 0.004 mm 3 It may be more than that.

[0031] The lower limit of the volume of the main body 11 is 0.03 mm 3It may be more than 0.5 mm 3 It may be more than 10 mm 3 It may be more than 100 mm 3 It may be more than 300 mm 3 It may be more than that.

[0032] The upper limit of the volume of the main body 11 is, for example, 100,000 mm 3 The upper limit of the volume of the main body 11 is 50,000 mm 3 It may be less than 10,000 mm 3 It may be less than 5,000 mm 3 It may be less than 1,000 mm 3 It may be less than 700 mm 3 It may be the following:

[0033] (Main body) In this embodiment, the main body 11 contains MOF as a main component. That the main body 11 contains MOF as a main component means that the content of MOF is the largest proportion (mass %) among the components contained in the main body 11. The same applies to the other raw materials.

[0034] The main body 11 may be made of only MOFs, that is, the main body 11 may be formed only from powder particles of MOFs.

[0035] In addition to the MOF, the main body 11 may contain an additive such as a binder. The content of the additive in the main body 11 is not particularly limited as long as it is within a range that does not impair the effects of the present invention.

[0036] The main body 11 may contain a binder, that is, the main body 11 may be formed by binding powder particles of MOFs with a binder.

[0037] As the binder, a known compound that imparts binding properties to the powder material can be used, such as polyvinylpyrrolidone.

[0038] When main body 11 is a molded body, the length of main body 11 is preferably 0.2 mm or more. When the length of main body 11 is 0.2 mm or more, it is easy to realize an adsorbent 10 that has an excellent balance between main body 11 and coating layer 12. In other words, it is easy to realize an adsorbent 10 that has an excellent balance between adsorption performance and durability.

[0039] In this embodiment, the length of main body 11 refers to the minimum value of the linear lengths passing through the center of gravity of adsorbent 10 when the cross section of adsorbent 10 is observed with an SEM. However, the SEM observation image passes through the center of gravity of adsorbent 10 and includes the entire adsorbent 10. In the example of Fig. 2, there are three linear lengths passing through the center of gravity of adsorbent 10: diameter (corresponding to length L1), height (corresponding to length L2), and diagonal length, and the minimum value of these is the height.

[0040] The lower limit of the length of the main body 11 may be 0.5 mm or more, 1.0 mm or more, or even 2.0 mm or more.

[0041] The upper limit of the length of the main body 11 is, for example, 220 mm or less. The upper limit of the length of the main body 11 may be 120 mm or less, 50 mm or less, 10 mm or less, or even 5.0 mm or less.

[0042] When the main body 11 has a sheet shape, the main body 11 may further contain other materials besides MOFs. Examples of such other materials include plasticizers, fillers, antioxidants, and pigments. Examples of fillers include fiber structures containing fibers. Examples of fibers include glass fibers; natural fibers such as wood pulp, cotton, and hemp (e.g., Manila hemp); and chemical fibers (synthetic fibers) such as polyester fibers, rayon, vinylon, acetate fibers, polyamide fibers, polyolefin fibers, and polyurethane fibers. Examples of fiber structures include woven fabrics, nonwoven fabrics, and paper.

[0043] When the main body 11 has a sheet shape, the main body 11 may further include a substrate. Examples of the substrate include a nonwoven fabric and a metal plate. The main body 11 may be a composite of the substrate and the MOF.

[0044] When the main body 11 has a sheet shape, the main body 11 may be rectangular. The longitudinal and lateral lengths of the rectangular main body 11 can be set appropriately and are not particularly limited.

[0045] When the main body 11 has a sheet shape, the thickness of the main body 11 is, for example, 1000 μm or less. The upper limit of the thickness of the main body 11 may be 500 μm or less, 400 μm or less, or even 300 μm or less. The lower limit of the thickness of the main body 11 is, for example, 100 μm or more.

[0046] Metal-organic frameworks (MOFs) are crystalline porous materials that have a core, such as a metal ion or metal cluster, and organic ligands coordinated to the core. MOFs have a larger adsorption capacity per volume than other adsorbents. By using MOFs in the adsorbent 10, it is possible to adsorb and desorb large amounts of specific gases, such as carbon dioxide. Some MOFs can adsorb and desorb large amounts of specific gases, such as carbon dioxide, with even smaller pressure differences. MOFs also have high repetitive adsorption and desorption performance and excellent durability. Furthermore, some MOFs exhibit so-called gate-type adsorption and desorption performance, which is observed in a phenomenon in which they barely adsorb gas up to a certain pressure P1, but suddenly begin adsorbing gas once the pressure P1 is exceeded, or in a phenomenon in which they barely desorb gas up to a certain pressure P2, but suddenly begin desorbing gas once the pressure drops below P2.

[0047] The MOF used in the adsorbent 10 is not particularly limited, but one with high adsorption / desorption performance for specific gases such as carbon dioxide is preferred. For example, it is known that the carbon dioxide adsorption / desorption performance of MOFs is significantly affected by the presence of metal sites (open metal sites) where oxygen atoms of carbon dioxide are relatively strongly coordinated, the specific surface area of ​​the MOF, and the flexibility of the MOF. In the low-pressure region (0.1 MPa or less), the carbon dioxide adsorption / desorption performance of MOFs is easily affected by the presence of the metal sites. In the high-pressure region (0.1 MPa or more), the carbon dioxide adsorption / desorption performance of MOFs tends to improve as the specific surface area increases.

[0048] In MOFs, the organic ligands contain functional groups for coordinating to the core. The number of functional groups in the organic ligands is, for example, 1 or more, and may be 2 or more, 3 or more, or even 4 or more. The upper limit of the number of functional groups is not particularly limited and is, for example, 10 or less. The organic ligands preferably have two or more functional groups for coordinating to the core. That is, the MOF preferably has a metal ion, metal cluster, or metal oxide cluster as the core and a bidentate or higher organic ligand. MOFs with such a structure tend to have a large specific surface area and are easily able to adsorb and desorb specific gases such as carbon dioxide.

[0049] More preferably, the MOF has a metal ion, metal cluster, or metal oxide cluster as a core and a tetradentate organic ligand. MOFs with such a structure are more likely to adsorb and desorb specific gases such as carbon dioxide.

[0050] MOFs may consist of a metal ion, metal cluster, or metal oxide cluster as a core and tetradentate organic ligands.

[0051] Examples of metals contained in the core include Cu, Zn, Pd, Mg, Al, Fe, Cr, Zr, Ni, and Co.

[0052] The metal ion as the core is Cu 2+ , Zn 2+ , Al3+ , Co 2+ Preferably, the metal ions are Cu, 2+ It is more preferable that:

[0053] The metal cluster as the core may be a Zn cluster. Examples of MOFs having a Zn cluster include MOF-5.

[0054] The metal oxide cluster as the core may be a Zr oxide cluster. Examples of MOFs having a Zr oxide cluster include UiO-66.

[0055] As described above, the organic ligand includes a functional group for coordinating with the core. The functional group may be at least one selected from the group consisting of a carboxyl group and a hydroxyl group. The functional group may be a carboxyl group. The organic ligand may be a tetracarboxylic acid containing four carboxyl groups as the functional group for coordinating with the core.

[0056] The organic ligand may contain a nitrogen atom (more specifically, a functional group containing a nitrogen atom) in addition to the above functional groups. Examples of the functional group containing a nitrogen atom include an amide group, an azo group, and an amino group. The tetracarboxylic acid as the organic ligand may contain a nitrogen atom.

[0057] The organic ligand may contain a ring structure. The number of ring structures contained in the organic ligand may be, for example, 1 or more, 2 or more, or even 3 or more. The upper limit of the number of ring structures is, for example, 5 or less. The ring structure is preferably an aromatic ring. The aromatic ring may be composed only of carbon atoms, or may be a heteroaromatic ring containing a heteroatom. The aromatic ring may be monocyclic or polycyclic. The number of carbon atoms in the aromatic ring is not particularly limited and is, for example, 4 to 14. Specific examples of the aromatic ring include a benzene ring and a naphthalene ring. In the organic ligand, a functional group for coordinating to the core may be a substituent of the ring structure.

[0058] The organic ligand may be represented by formula (a):

[0059] [ka]

[0060] In the above formula (a), R 1 is a single bond or an arbitrary linking group. The arbitrary linking group may contain at least one carbon atom. The arbitrary linking group may contain one selected from the group consisting of unsaturated hydrocarbons and heterocyclic compounds. Examples of linking groups containing unsaturated hydrocarbons include arylene groups such as phenylene groups. In addition to the above, the arbitrary linking group may further contain a functional group containing a nitrogen atom (e.g., an amide group, an azo group, or an amino group).

[0061] In the above formula (a), R 2 From R 7 are each independently a hydrogen atom or an arbitrary substituent. Examples of the arbitrary substituent include a hydrocarbon group such as an alkyl group, and a functional group containing a nitrogen atom such as a nitro group or an amino group.

[0062] An example of an MOF having an organic ligand having the structure represented by the above formula (a) is an MOF having an nbo (niobium oxide) structure. The MOF may have an nbo structure. MOFs having an nbo structure tend to have a large specific surface area and adsorb a large amount of a specific gas such as carbon dioxide. The MOF may have a structure other than the nbo structure.

[0063] It is preferable that the amount of a specific gas adsorbed by a MOF in the pressure range of 0.1 MPa or more and less than 1.1 MPa is greater than the amount of a specific gas adsorbed by a MOF in the pressure range of 0 MPa or more and less than 0.1 MPa. Such a MOF is suitable for the adsorbent 10 of this embodiment.

[0064] As the MOF, for example, those listed in the literature and shown in Table 1 below may be used. Note that the MOFs listed in Table 1 are non-limiting examples, and other MOFs may also be used. In Table 1, the effective adsorption amount is calculated as the difference between the adsorption amount per unit weight of the MOF at 1.0 MPa and the adsorption amount per unit weight of the MOF at 0.1 MPa, based on the data on the adsorption amount per unit weight of carbon dioxide at 0.1 to 1.0 MPa around room temperature (20 to 30°C) listed in each literature.

[0065] [Table 1]

[0066] The MOFs listed in Table 1 have relatively large pore sizes and excellent effective adsorption capacities per weight of 8 to 14 mmol / g. Therefore, they are considered useful for transporting specific gases such as carbon dioxide. No. 1 (NOTT-125), No. 3 (HNUST-3), No. 4 (HNUST-7), No. 9 (PCN-11), and No. 10 (PCN-16) have an nbo structure. No. 22 (HKUST-1) has the advantage of being inexpensive and mass-produced. The MOFs listed in Table 1 are suitable for use as the main body of an adsorbent that satisfies the above-mentioned (i). However, the MOFs listed in Table 1 may also be used as the main body of an adsorbent that satisfies the above-mentioned (iii).

[0067] For example, the MOFs shown in Table 2 below may be used. Note that the MOFs shown in Table 2 are non-limiting examples, and other MOFs may also be used. In Table 2, No. 23 is based on the data on the adsorption amount per weight of carbon dioxide at 0.1 to 1.0 MPa near room temperature (20 to 30 ° C) described in the literature (Nano Res. 14, 2021, 507-511). The difference between the adsorption amount per unit weight of the MOF at 1.0 MPa and the adsorption amount per unit weight of the MOF at 0.1 MPa is calculated as the effective adsorption amount. In Table 2, Nos. 24 to 35, each MOF was subjected to vacuum heating pretreatment at 150 ° C for 6 hours, and then the adsorption amount per unit weight of the MOF at 1.0 MPa and the adsorption amount per unit weight of the MOF at 0.1 MPa were determined using a high-pressure gas adsorption apparatus (Anton Paar, isorbHP1) at 25 ° C. The difference between the two was calculated as the effective adsorption amount.

[0068] [Table 2]

[0069] The MOFs shown in Table 2 are preferably used, for example, as the main body of an adsorbent that satisfies the above (i). However, the MOFs shown in Table 2 may also be used, for example, as the main body of an adsorbent that satisfies the above (iii).

[0070] As the MOF, for example, those listed in the literature (Adv. Funct. Mater. 2023, 2307478) shown in Table 3 below may be used. Note that the MOFs shown in Table 3 are non-limiting examples, and MOFs other than these may also be used. No. 36 in Table 3 and No. 26 in Table 2 are the same MOF.

[0071] [Table 3]

[0072] As described in the above literature, the MOFs shown in Table 3 have excellent adsorption capacity at 400 ppm, and are therefore considered useful for gas separation devices equipped with gas adsorbents that separate acidic gases such as carbon dioxide contained in the atmosphere. The MOFs shown in Table 3 are suitable for use as the main body of an adsorbent that satisfies the above-mentioned (iii). However, the MOFs shown in Table 3 may also be used as the main body of an adsorbent that satisfies the above-mentioned (i).

[0073] (covering layer) In this embodiment, the coating layer 12 contains a resin as a main component.

[0074] The coating layer 12 may be made of only a resin, that is, the coating layer 12 may be formed only from a resin.

[0075] In addition to the resin, the coating layer 12 may contain additives such as a solvent. The content of the additive in the coating layer 12 is not particularly limited as long as it is within a range that does not impair the effects of the present invention.

[0076] The coating layer 12 covers at least a part of the surface 11s of the main body 11. With this configuration, the durability of the adsorbent 10 can be improved.

[0077] 1 and 2, the coating layer 12 preferably covers the entire surface 11s of the main body 11. With this configuration, the durability of the adsorbent 10 can be reliably improved.

[0078] As shown in FIG. 2, it does not have to be constant across the surface 11s of the main body portion 11.

[0079] The minimum thickness of coating layer 12 is preferably in the range of 300 nm to 900 μm. This configuration makes it easy to realize an adsorbent 10 that has a good balance between main body 11 and coating layer 12. In other words, it makes it easy to realize an adsorbent 10 that has a good balance between adsorption performance and durability.

[0080] In this embodiment, the minimum thickness of the coating layer 12 means the thickness of the portion of the coating layer 12 that is the thinnest when the cross section of the adsorbent 10 is observed with an SEM.

[0081] The lower limit of the minimum thickness of the coating layer 12 may be 500 nm or more, 1 μm or more, 3 μm or more, or even 5 μm or more.

[0082] The upper limit of the minimum thickness of the coating layer 12 may be 700 μm or less, 500 μm or less, 300 μm or less, or even 100 μm or less.

[0083] The maximum thickness of coating layer 12 is preferably in the range of 500 nm to 2000 μm. This configuration makes it easy to realize an adsorbent 10 that has a good balance between main body 11 and coating layer 12. In other words, it makes it easy to realize an adsorbent 10 that has a good balance between adsorption performance and durability.

[0084] In this embodiment, the maximum thickness of the coating layer 12 means the thickness of the thickest part of the coating layer 12 when the cross section of the adsorbent 10 is observed with an SEM.

[0085] The lower limit of the maximum thickness of the coating layer 12 may be 700 nm or more, 1 μm or more, 3 μm or more, or even 5 μm or more.

[0086] The upper limit of the maximum thickness of the coating layer 12 may be 1500 μm or less, 1000 μm or less, 500 μm or less, or even 200 μm or less.

[0087] The resin contained in coating layer 12 includes a thermoplastic resin. The resin contained in coating layer 12 may be a thermoplastic resin. When the resin contained in coating layer 12 is a thermoplastic resin, the durability of adsorbent 10 is likely to be improved.

[0088] The thermoplastic resin is preferably at least one selected from the group consisting of elastomers and polyvinyl resins. With this configuration, the durability of the adsorbent 10 is more likely to be improved.

[0089] The elastomer may include at least one selected from the group consisting of butyl rubber (IIR), butadiene rubber (BR), styrene butadiene rubber (SBR), isoprene rubber (IR), and nitrile rubber (NBR). The elastomer may be a partially hydrogenated elastomer obtained by partially hydrogenating these rubber components.

[0090] The polyvinyl resin may contain at least one selected from the group consisting of polyvinyl alcohol (PVA) and polyvinyl acetal (PVB).

[0091] The polyvinyl resin may be PVB, which includes a monomer unit A having a substituent other than a carboxyl group, a hydroxyl group, or an aldehyde group on the side chain.

[0092] The resin contained in coating layer 12 preferably contains monomer unit A, and the ratio of the amount of monomer unit A to the total amount of all monomer units contained in the resin is preferably in the range of 35 mol% to 80 mol%. When this ratio is 35 mol% or more, sufficient water resistance and heat resistance can be exhibited in adsorbent 10. When this ratio is 80 mol% or less, a decrease in resin density in coating layer 12 is suppressed, thereby improving the durability of adsorbent 10.

[0093] The lower limit of the proportion of the amount of substance of the monomer unit A relative to the total amount of substance of all monomer units contained in the resin may be 38 mol % or more, or may be 42 mol % or more.

[0094] The upper limit of the proportion of the amount of substance of the monomer unit A relative to the total amount of substance of all monomer units contained in the resin may be 75 mol % or less, or may be 70 mol % or less.

[0095] The side chain of the monomer unit A preferably has at least one selected from the group consisting of an acetal group, a benzene ring, and a linear alkyl group.

[0096] The mass ratio of main body 11 to coating layer 12 in adsorbent 10 is preferably in the range of 99:1 to 30:70. Such a mass ratio makes it easy to realize an adsorbent 10 that has a good balance between main body 11 and coating layer 12. In other words, it makes it easy to realize an adsorbent 10 that has a good balance between adsorption performance and durability.

[0097] In this embodiment, the mass of the main body 11 and the mass of the coating layer 12 in the adsorbent 10 can be determined, for example, by the following method. First, the mass of the adsorbent 10 is measured. Next, the coating layer 12 is removed from the adsorbent 10 using a solvent. The mass of the adsorbent 10 after the coating layer 12 has been removed is measured, and this is taken as the mass of the main body 11. The mass of the coating layer 12 is calculated by subtracting the mass of the main body 11 from the mass of the adsorbent 10.

[0098] The mass ratio of the main body 11 to the coating layer 12 in the adsorbent 10 is more preferably in the range of 96:4 to 50:50.

[0099] The shape of the adsorbent 10 is not particularly limited. The adsorbent 10 may have the same shape as the main body 11. In the example shown in Fig. 1, the adsorbent 10 is disk-shaped. Although not shown, the adsorbent 10 may also be sheet-shaped.

[0100] The pressure range in which the adsorbent 10 of this embodiment is used is not particularly limited, but is preferably from atmospheric pressure (e.g., 0.1 MPa) to 1.0 MPa. In other words, the adsorbent 10 is preferably capable of adsorbing and desorbing a specific gas in a pressure range from atmospheric pressure to 1.1.0 MPa.

[0101] The temperature range in which the adsorbent 10 of this embodiment is used is preferably −40° C. or higher and 100° C. or lower. In other words, the adsorbent 10 is preferably capable of adsorbing and desorbing a specific gas in the temperature range of −40° C. or higher and 100° C. or lower.

[0102] The specific gas adsorbed and desorbed by the adsorbent 10 of this embodiment includes, for example, an acidic gas. Examples of acidic gases include carbon monoxide, carbon dioxide, hydrogen sulfide, carbonyl sulfide, sulfur oxides (SOx), hydrogen cyanide, and nitrogen oxides (NOx), with carbon dioxide being preferred. When the specific gas is an acidic gas, the mixed gas contacted with the adsorbent 10 may contain gases other than the acidic gas. Examples of the other gases include hydrogen, nitrogen, oxygen, methane, ethane, helium, argon, propane, and propylene, with nitrogen and methane being preferred. The adsorbent 10 of this embodiment is particularly suitable for recovering carbon dioxide from a mixed gas containing carbon dioxide and nitrogen. The specific gas may also be one of the other gases described above.

[0103] <Embodiment of the method for producing the adsorbent> Next, a method for producing the above-mentioned adsorbent 10 will be described.

[0104] The method for producing the adsorbent 10 includes a coating step of coating the surface 11s of the MOF-containing main body 11 with a resin-containing coating layer 12. The main body 11 satisfies at least one selected from the group consisting of the following (i) to (iii): (i) The main body 11 is a molded body. (ii) The volume of the main body 11 is 0.004 mm 3 That's all. (iii) The main body 11 has a sheet shape.

[0105] When the above condition (i) is satisfied, a molding step of molding the main body 11, which is a molded body, may be included before the coating step. The method for molding the main body 11 in the molding step is not particularly limited. For example, the main body 11 may be molded by agglomerating MOF powder particles with physical force. More specifically, the main body 11 may be molded by compressing the MOF powder particles using a tablet press. At this time, a binder may be added to the MOF powder particles.

[0106] If the above condition (iii) is satisfied, a fabrication step of fabricating a sheet-shaped main body 11 may be included before the coating step. The main body 11 may include a substrate in addition to the MOF. Examples of the substrate include a nonwoven fabric and a metal plate. The main body 11 may be a composite of the substrate and the MOF. In the fabrication step, the method for fabricating the main body 11 is not particularly limited. For example, the composite can be fabricated by applying a solution in which MOF powder particles are dispersed in a solvent to the surface of a nonwoven fabric. The coating method is not particularly limited, and known methods such as roll coating, spin coating, and dip coating can be used as the coating method. For example, the composite can be fabricated by growing a crystalline film of the MOF on the surface of a metal plate.

[0107] In the coating step, the method for forming the coating layer 12 on the surface 11s of the main body 11 is not particularly limited. A known method used in the fields of medicine and the like can be used. For example, a method of mixing a resin and the main body 11 in a solution, a method of spraying a solution in which a resin is dissolved or dispersed onto the surface 11s of the main body 11, a method of applying a solution in which a resin is dissolved or dispersed onto the surface of the main body 11, a method of polymerizing a resin monomer on the surface 11s of the main body 11, etc. can be used.

[0108] Among these, the method of mixing the resin and the main body 11 in a solution is preferably used because of its ease of operation. First, the resin is dissolved in a solvent to prepare a solution. By mixing the resin and the main body 11 in the solution, the resin is adhered to the surface 11s of the main body 11. The main body 11 with the resin adhered thereto is dried at room temperature or by heating in the range of room temperature to 130°C. In this way, the adsorbent 10 can be obtained.

[0109] The solvent preferably has low polarity so that the resin can be easily dissolved, and a boiling point of 150°C or less. Examples of such solvents include alcohols, ethers, hydrocarbons, ketones, etc. Examples of hydrocarbons include n-hexane, cyclohexane, toluenes, etc.

[0110] Before the coating step, the main body 11 may or may not be activated. For example, the main body 11 can be activated by drying it in a vacuum atmosphere at 100°C for 24 hours. Activation makes it possible to remove the solvent contained in the main body 11. If the solvent adsorbed on the main body 11 has a higher boiling point than the solution in which the resin is dissolved, it is better to activate the main body 11.

[0111] In this manufacturing method, since the main body 11 satisfies at least one of the above conditions (i) to (iii), less MOF is exposed to the outside than with the same amount of MOF powder particles, and the penetration of resin into the MOF pores is suppressed, thereby making it possible to obtain an adsorbent 10 with improved durability and suppressed deterioration in adsorption performance. [Example]

[0112] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0113] Example 1 Powder particles of HKUST-1 were prepared as MOFs. The powder particles of HKUST-1 were compressed using a tablet press at a tableting pressure of 4.5 kN / cm.2 The pellets were compressed into cylindrical pellets with a diameter of 13 mm, a height of 3 mm, and a volume of 398 mm. 3 FIG. 3 is a plan view of the cylindrical pellet thus produced. As shown in FIG. 3, the resulting pellet was cut into four equal parts parallel to a line L passing through the central axis X, and one end piece P1 was used as the main body of Example 1. A coating agent containing 15 wt% styrene-butadiene-styrene rubber (SBS) as the resin and methylcyclohexane (MCH) as the solvent was used as the coating agent for forming the coating layer. The coating agent was applied to the entire surface of the main body, and then dried at 130°C to form the coating layer. In this way, the adsorbent of Example 1 was obtained.

[0114] Example 2 After forming the coating layer, the coating agent was further applied and dried. Except for this, the adsorbent of Example 2 was obtained in the same manner as in Example 1.

[0115] Example 3 The coating agent used to form the coating layer was a coating agent containing polyvinyl acetal (PVB) as the resin and ethyl alcohol (EtOH) as the solvent. The coating agent was sprayed onto the entire surface of the main body, and then dried at 100°C to form the coating layer. Except for these, the adsorbent of Example 3 was obtained in the same manner as in Example 1.

[0116] (Comparative Example 1) A piece P1 of the HKUST-1 pellet used as the main body in Example 1 was used as the adsorbent of Comparative Example 1.

[0117] (Comparative Example 2) 67.24 mg of the HKUST-1 powder particles used in Example 1 and the coating agent used in Example 1 were mixed 30 times in a mortar. This allowed the coating agent to be applied to the surfaces of the powder particles. After the coating agent was applied to the surfaces of the powder particles, the particles were dried at 130°C to form a coating layer. This resulted in the production of a powdered adsorbent of Comparative Example 2.

[0118] (Comparative Example 3) 61.42 mg of the HKUST-1 powder particles used in Example 1 and the coating agent used in Example 3 were mixed 30 times in a mortar. This allowed the coating agent to be applied to the surfaces of the powder particles. After the coating agent was applied to the surfaces of the powder particles, the particles were dried at 100°C to form a coating layer. This resulted in the production of a powdered adsorbent of Comparative Example 3.

[0119] For the adsorbents of the Examples and Comparative Examples, the mass ratio of the main body to the coating layer in the adsorbent and the thickness of the coating layer were measured using the methods described above. The results are shown in Table 4.

[0120] <Durability test> Using a thermo-hygrostat (manufactured by Espec Corporation), the adsorbent was left to stand in an environment of 65°C and 25% RH for 24 hours.

[0121] <Method for measuring nitrogen gas adsorption amount> Nitrogen gas adsorption isotherms were measured under liquid nitrogen (temperature 77 K) using a gas adsorption measurement device (Microtrackbell, BELSORP MINI X). 3 The amount of nitrogen gas adsorbed at 1000 kJ / g was taken as the amount of nitrogen gas adsorbed by the adsorbent.

[0122] For the adsorbents of the Examples and Comparative Examples, the nitrogen gas adsorption amounts before and after the durability test were measured using the method described above. The results are shown in Table 4. In Table 4, the retention rate of the nitrogen gas adsorption amount is the ratio of the nitrogen gas adsorption amount after the durability test to the nitrogen gas adsorption amount before the durability test.

[0123] [Table 4]

[0124] As shown in Table 4, the adsorbents of Examples 1 to 3 had a higher nitrogen gas adsorption capacity retention rate and suppressed the deterioration of adsorption performance during the durability test compared to the adsorbents of Comparative Examples 1 to 3. These results demonstrate that the adsorbents of Examples 1 to 3 are suitable for improving durability. A comparison between Example 1 and Comparative Example 2 revealed that even when the mass ratio of the coating layer was similar, the durability of the adsorbent was difficult to improve when the main body of the adsorbent was in the form of powder particles. This is thought to be because when the main body of the adsorbent was in the form of powder particles, the powder particles were likely to be exposed or the coating layer was not thick enough. Furthermore, in Comparative Example 2, where the main body of the adsorbent was in the form of powder particles, the nitrogen gas adsorption capacity was low before the durability test. This is thought to be because the coating layer blocked the pores of the powder particles in the adsorbent of Comparative Example 2. [Industrial Applicability]

[0125] The adsorbent of this embodiment is suitable as an adsorbent for efficiently recovering carbon dioxide from exhaust gas emitted from a combustion device, for example. [Explanation of symbols]

[0126] 10. Adsorbent 11 Main body 11s surface 12 Covering layer

Claims

1. a main body including a metal-organic framework; a coating layer that coats the surface of the main body and contains a resin; Equipped with The adsorbent body satisfies at least one selected from the group consisting of the following (i) to (iii): (i) The main body is a molded body. (ii) the volume of the main body is 0.004 mm 3 That's all. (iii) The main body has a sheet shape.

2. The adsorbent according to claim 1 , wherein the metal organic framework has a metal ion, a metal cluster, or a metal oxide cluster as a core and bidentate or higher organic ligands.

3. 2. The adsorbent according to claim 1, wherein the minimum thickness of the coating layer is in the range of 300 nm to 900 μm.

4. The adsorbent of claim 1 , wherein the resin comprises a thermoplastic resin.

5. 5. The adsorbent according to claim 4, wherein the thermoplastic resin is at least one selected from the group consisting of elastomers and polyvinyl resins.

6. 6. The adsorbent of claim 5, wherein the elastomer comprises at least one selected from the group consisting of butyl rubber, butadiene rubber, styrene butadiene rubber, isoprene rubber, and nitrile rubber.

7. The adsorbent according to claim 5 , wherein the polyvinyl resin comprises at least one selected from the group consisting of polyvinyl alcohol and polyvinyl acetal.

8. the resin includes a monomer unit A having a substituent other than a carboxyl group, a hydroxyl group, and an aldehyde group on a side chain, 2. The adsorbent according to claim 1, wherein the ratio of the amount of substance of said monomer unit A to the total amount of substance of all monomer units contained in said resin is in the range of 35 mol % to 80 mol %.

9. 2. The adsorbent according to claim 1, wherein the mass ratio of the main body to the coating layer in the adsorbent is in the range of 99:1 to 30:70.

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