Hybrid adsorbent particles and filters made with particles

Abstract

A composition comprising adsorbent mixing particles wherein the particles comprise a first adsorbent material, a second adsorbent material, and a binder mixed with the first adsorbent material or the second adsorbent material or both, and wherein the first adsorbent material and the second adsorbent material are each located outside a surface of the other adsorbent material. The sorbent composition is suitable for purifying a gas stream, in particular for a filter of a respirator.

Description

[0001] Statement Regarding Federally Sponsored Research or Development

[0002] This invention was made with government support under Agreement No. CWMD1820 - 004 awarded by the Combat Capabilities Development Command Chemical Biological Center, under Base Agreement No. 2018 - 875A and Other Transaction Agreement (OTA) No. W15QKN - 18 - 9 - 1004. The government has certain rights in this invention. Technical Field

[0003] The present disclosure relates to hybrid adsorbent particles comprising two or more adsorbent materials, methods of making the hybrid adsorbent particles, and compositions, devices, and filters made using the hybrid adsorbent particles. The present disclosure also relates to such adsorbents, methods, compositions, devices, and filters, wherein the hybrid adsorbent particles can be in the form of core - shell structures or doped hybrid particles. Background Art

[0004] Adsorbents are used in many different environments and applications to capture various desired substances, or to capture fouling agents, contaminants, or other unwanted substances in a fluid stream. When the fluid stream comprises a mixture of substances to be captured by adsorption, multiple types of adsorbents may be required to ensure capture of different substances. However, different adsorbents may have different physical and chemical properties, and thus providing a uniform mixture of adsorbents is a challenge.

[0005] One application of adsorbents is to remove contaminants and other fouling agents from an air stream. To this end, it is known to use adsorbents in filters placed in devices such as air purifiers and air respirators. Air - purifying respirators can be used in a variety of situations, particularly where a user needs to be protected in a hazardous area. Such hazardous areas may include regions or situations where exposure to a range of threats is possible, including toxic industrial chemicals (TIC); and chemical, biological, radiological, or nuclear (CBRN) hazards, which may include chemical warfare agents (CWA). In such hazardous areas, personal protective equipment (PPE) must be provided to individuals to protect against multiple threats. In particular, air respirators should provide protection against various airborne harmful contaminants. In this application, a single type of adsorbent may not be sufficient to capture multiple air pollutants.

[0006] As is well known, activated carbon is used as a filter material in air respirators for PPE. Activated carbon is a porous broad-spectrum adsorbent, but it has poor effectiveness against most TIC, CBRN, or CWA pollutants (such as ammonia). It is further known that activated carbon can be impregnated with metals or other chemicals to enhance its adsorption capacity for selected harmful pollutants. However, even impregnated activated carbon does not adsorb certain harmful pollutants. The deficiencies of activated carbon as an adsorbent can be addressed by using a combination of activated carbon and one or more additional adsorbent materials. These additional adsorbent materials can be selected based on their ability to adsorb certain pollutants that activated carbon does not adsorb.

[0007] Using multiple adsorbent materials in a single filter structure can pose challenges in the manufacture of such filter structures, respirators, and other devices that include such filter structures. For example, if a respirator filter is constructed using different adsorbent layers, it may be challenging to create a multi-layer with a consistent thickness, which is necessary for consistent filtration performance of multiple pollutants. For example, using multiple layers of different adsorbent materials in a single filter structure may result in different breakthrough times for different pollutants. Using such multiple layers of different adsorbents also creates additional manufacturing steps, which increases the cost of the filter. In addition, using such multiple layers of different adsorbents may pose challenges in terms of design complexity, require process changes for high-throughput devices, and result in other variations in performance, such as those caused by pinholes or channels in the layers. Furthermore, using multiple adsorbent layers may increase the thickness of the filter structure; this is disadvantageous because filters with a thinner profile are preferred in modern respirator designs.

[0008] US 9095839 discloses a hybrid composite material of a metal-organic framework (MOF) encapsulated in a nanocarbon material, where the MOF grows inside, outside, or both inside and outside the nanocarbon morphology to provide an adsorbent that can be used to adsorb H2, N2, or CO2.

[0009] US 9566575 discloses a composite material of a metal-organic framework and activated carbon, where starting from a metal precursor compound containing at least one metal and at least one ligand precursor, metal-organic framework material is generated in situ in the pores and / or pore system of the activated carbon.

[0010] KR101638049B1 discloses a core-shell structure having a core portion made of carbon nanotubes, a first shell of polyvinylpyrrolidone on the surface of the carbon nanoparticles, and a second shell coated with a metal-organic framework on the surface of the first shell to provide an adsorbent that is selective for gases such as CO2, Ar, Ne, He, CF4, H2, N2, O2, and C n H 2n+2 and so on.

[0011] Each of the above references discloses a MOF hybrid composition in which the MOF material is directly synthesized on the surface or in the pores of other materials in the composition. This complicates the manufacturing process and inherently limits the types of MOFs that can be used in adsorbent compositions.

[0012] An object of the present invention is to provide an adsorbent composition comprising a plurality of adsorbent materials that provide adsorption for various substances in a fluid stream.

[0013] Another object of the present invention is to provide an adsorbent composition comprising a plurality of adsorbent materials that provide adsorption for various harmful substances in the air.

[0014] Another object of the present invention is to provide an adsorbent composition suitable for an air respirator for PPE.

[0015] Another object of the present invention is to provide a method for preparing such an adsorbent composition.

[0016] Another object of the present disclosure is to provide a device comprising such an adsorbent composition.

[0017] Another object of the present disclosure is to provide a method for purifying a gas stream, the method comprising passing the gas stream through a device comprising the adsorbent composition. Summary of the Invention

[0018] The above objects of the present disclosure are achieved by a composition comprising adsorbent hybrid particles, wherein the particles comprise a first adsorbent material, a second adsorbent material, and a binder mixed with the first adsorbent material or the second adsorbent material or both, and wherein the first adsorbent material and the second adsorbent material are each located external to the surface of the other adsorbent material. In one embodiment, the adsorbent hybrid particles comprise a substantially random mixture of a first adsorbent material, a second adsorbent material, and a binder. In one embodiment, the adsorbent hybrid particles are in the form of a core-shell structure comprising a core and a shell, the core comprising the first adsorbent material and the shell comprising a substantially random mixture of the binder and the second adsorbent material.

[0019] The first and second adsorbent materials can be selected based on their ability to adsorb different substances in a fluid stream. The adsorbent can be independently selected from carbonaceous adsorbents, metal-organic framework materials, zeolites, porous organic polymers, covalent organic frameworks, activated alumina, silica gel, and other known adsorbents. In some embodiments, the mixed adsorbent particles can include three or more different adsorbent materials. In one aspect of the present invention, the first and second adsorbents are selected from carbon particles and at least one metal-organic framework (MOF) material outside the surface of the carbon particles, and the binder is mixed with the carbon particles, the MOF material, or both. In one embodiment, the adsorbent composition includes adsorbent mixed particles that include a substantially random mixture of carbon particles, MOF particles, and a binder. In another embodiment, the adsorbent composition includes adsorbent mixed particles in the form of a core-shell structure that includes a core and a shell, the core including at least one carbon particle and the shell including a substantially random mixture of a binder and particles of the MOF. In yet another embodiment, the adsorbent composition includes adsorbent mixed particles in the form of a core-shell structure that includes a core and a shell, the core including the MOF material and the shell including a substantially random mixture of a binder and carbon particles. In each embodiment, the MOF can be selected based on its ability to adsorb contaminants that are less adsorbed by the carbon particles. In each embodiment, the MOF material is located outside the surface of the carbon particles, particularly outside the pores of the carbon particles.

[0020] A method of preparing mixed adsorbent particles includes the steps of: providing a mixture including first adsorbent particles, second adsorbent particles, and a binder; granulating the mixture with a liquid carrier to obtain mixed adsorbent particles, wherein at least some of the particles include a substantially random mixture of the first adsorbent particles, the second adsorbent particles, and the binder; and drying the mixed adsorbent particles to remove the liquid carrier. In one embodiment of the method, the first adsorbent can include carbon particles and the second adsorbent can include MOF particles.

[0021] Another method for preparing mixed adsorbent particles includes the following steps: providing a quantity of particles comprising a first adsorbent, providing a suspension comprising a binder and second adsorbent particles in a liquid carrier, coating the particles comprising the first adsorbent with the suspension, and drying the coated particles to provide mixed adsorbent particles having a core-shell structure, the core-shell structure comprising a core and a shell, the core comprising the first adsorbent and the shell comprising a substantially random mixture of the binder and the second adsorbent particles. In one embodiment of the method, the first adsorbent comprises carbon particles, the second adsorbent comprises MOF particles, the suspension comprising MOF particles and a binder is coated on the carbon particles, and the coated particles are dried to provide mixed adsorbent particles comprising a core and a shell, the core comprising carbon and the shell comprising a substantially random mixture of the binder and MOF particles. In another embodiment of the method, the first adsorbent comprises particles comprising MOF, the second adsorbent comprises particles comprising carbon, the suspension comprising carbon particles and a binder is coated on the particles comprising MOF, and the coated particles are dried to provide mixed adsorbent particles comprising a core and a shell, the core comprising MOF material and the shell comprising a substantially random mixture of the binder and particles comprising carbon. Other adsorbents disclosed herein can be used as the first and second adsorbents in this method.

[0022] When one of the adsorbents comprises carbon, the carbon can be selected from one or more of activated carbon, impregnated carbon, and impregnated activated carbon.

[0023] In each method for preparing mixed adsorbent particles, the liquid carrier can be any liquid that does not react with the first adsorbent, the second adsorbent, and the binder. In some embodiments, water or methanol can be used as the liquid carrier.

[0024] In each method for preparing mixed adsorbent particles, the dried mixed particles can be sieved to obtain the desired particle size range. The adsorbent mixed particles can also be activated by heating at a desired temperature for a desired time to optimize the adsorbent performance.

[0025] The present disclosure also relates to an apparatus comprising the adsorbent composition disclosed herein. In one embodiment, the apparatus can comprise a filter for filtering contaminants from an air stream, the filter comprising the composition comprising the adsorbent mixed particles disclosed herein. Advantageously, the mixed adsorbent particles disclosed herein can be easily incorporated into a filter structure for devices such as air respirators in a single step to be used as a component of PPE, thereby avoiding a separate step of assembling individual adsorbent materials in the filter structure.

[0026] The mixed adsorbent particles can also be used in apparatuses providing collective protection, such as air purification systems for buildings and vehicles.

[0027] The present invention also relates to a method for purifying an air stream, the method comprising passing the air stream through a device comprising adsorbent mixed particles, the adsorbent mixed particles comprising a first adsorbent, a second adsorbent, and a binder mixed with the first adsorbent or the second adsorbent or both. In one embodiment, the first and second adsorbents are selected from carbon particles and at least one metal-organic framework (MOF) material external to the surface of the carbon. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 is a schematic view of a mixed adsorbent particle that is a substantially random mixture of carbon particles, MOF particles, and a binder.

[0029] Figure 2 is a schematic view of a mixed adsorbent particle that includes a core of carbon and a shell that is a substantially random mixture of MOF particles and a binder.

[0030] Figure 3 is a schematic view of a mixed adsorbent particle that includes a core of MOF material and a shell that is a substantially random mixture of carbon particles and a binder. DETAILED DESCRIPTION

[0031] Disclosed herein is a composition comprising adsorbent mixed particles, the adsorbent mixed particles comprising a first adsorbent material, a second adsorbent material, and a binder mixed with the first adsorbent material or the second adsorbent material or both, and wherein the first adsorbent material and the second adsorbent material are each external to the surface of the other adsorbent material.

[0032] As used herein, the term "external to the surface" with respect to a porous adsorbent means that the other adsorbent is not disposed within the pores of the porous adsorbent.

[0033] In one embodiment of the composition, the adsorbent mixed particles comprise a substantially random mixture of a first adsorbent material, a second adsorbent material, and a binder. In one embodiment, the adsorbent composition comprises adsorbent mixed particles in the form of a core-shell structure, the core-shell structure comprising a core and a shell, the core comprising a first adsorbent material and the shell comprising a substantially random mixture of a binder and a second adsorbent material.

[0034] The first and second adsorbent materials can be selected based on their ability to adsorb different substances in the fluid stream. The adsorbent can be selected from carbonaceous adsorbents, metal-organic framework materials, zeolites, porous organic polymers, covalent organic frameworks, activated alumina, silica gel, and other known adsorbents. In one aspect of the present invention, the first and second adsorbents are selected from carbon particles and at least one MOF material outside the pores of the carbon particles. In one embodiment, at least some of the adsorbent particles comprise a substantially random mixture of carbon particles, MOF particles, and a binder. In another embodiment, the particles are in the form of a core-shell structure comprising a core and a shell, the core comprising at least one carbon particle, and the shell comprising a substantially random mixture of a binder and MOF material particles. In yet another embodiment, the particles are in the form of a core-shell structure comprising a core and a shell, the core comprising MOF material, and the shell comprising a substantially random mixture of a binder and carbon particles.

[0035] The carbon can be any commercially available type known to be used as an adsorbent. In some embodiments, charcoal can be used as the adsorbent. In some embodiments, activated carbon can be particularly suitable as the adsorbent in the hybrid adsorbent particles disclosed herein. Activated carbon is a highly porous, high-surface-area adsorptive material with a largely amorphous structure. It consists mainly of aromatic configurations in which carbon atoms are linked by random cross-linking. The degree of order varies based on the starting raw material and the thermal history. The graphite sheets in steam-activated coal are somewhat ordered, while more amorphous aromatic structures are found in chemically activated wood. The random bonding results in a highly porous structure with many cracks, fissures, and voids between the carbon layers. Activated carbon adsorbents are tailored mainly based on pore size and pore volume requirements for specific applications. The porosity and other parameters are controlled by: 1) raw material selection; 2) activation process conditions; and 3) post-treatment steps. Depending on the application, activated carbon can be in the form of powder (PAC), granules (GAC), or extrudates (EAC). The basic principles of activated carbon can be found in an article titled "Activated Carbon: Basic Principles and New Applications", Ken Koehlert, Chemical Engineering, July 2017, pages 32 - 40, which is incorporated herein by reference. One brand of activated carbon that may be suitable for the disclosed hybrid particles is high-surface-area activated carbon.

[0036] All three forms of activated carbon have a particle size range, from powders less than 1 micron in diameter to granules 6 mesh (3360 microns) in diameter or larger. For ease of handling, activated carbon particles of at least 1 micron are preferred. The activated carbon particles used in the adsorbent particles disclosed herein can be at least 1 micron, or at least 50 microns, or at least 100 microns, or at least 150 microns, or at least 250 microns, or at least 500 microns, or at least 1000 microns, or at least 1500 microns, or at least 2000 microns, or at least 2500 microns, or at least 3000 microns. Activated carbon particles of any size can be used in the first embodiment, wherein the adsorbent mixed particles comprise a mixture of activated carbon particles and MOF particles. Particles of at least 1 micron can be used in the second embodiment, wherein the activated carbon is the core of a core-shell adsorbent structure. Smaller sized particles, such as powders, can be used in the third embodiment, wherein the activated carbon particles are included in the shell of a core-shell structure. In one embodiment, the activated carbon can be in the form of particles in the range of 12 x 30 mesh or about 590 microns to about 1700 microns.

[0037] In some embodiments, the activated carbon used herein can be impregnated with other materials, such as metals, metal oxides, or other chemicals, to provide additional functionality to the adsorbent particles. Impregnated activated carbon materials are known in the art as useful adsorbents for purifying flue gases, industrial gases, etc. As used in the mixed adsorbent particles disclosed herein, the material impregnated in the activated carbon will be selected based on the expected contaminants to be adsorbed and optionally deactivated, as well as compatibility with the carriers, solvents, and binders used in the methods of preparing the adsorbent particles disclosed herein. Suitable activated carbons include those available from Calgon Carbon Corporation, Moon Township, Pennsylvania, particularly granular activated carbon products, such as those sold by Calgon Carbon Corporation and known to be useful for personal protective equipment.

[0038] Metal-organic frameworks are well-known porous adsorbents with high surface areas. MOFs comprise metal ion corner atoms and at least bidentate linker molecules or ligands that are attached to the corner atoms, thus forming a framework structure. The metals and ligands of the clusters can be chosen to control the porosity of the MOF and its ability to chemically interact with other molecules. Accordingly, the design and selection of MOFs can optimize the adsorption and degradation activities towards specific pollutants. The particle size range of MOFs can range from nanoscale particles to diameters up to 500 microns. In a first embodiment, MOF particles of any size can be used, wherein substantially each adsorbent particle comprises a substantially random mixture of carbon particles, MOF particles, and a binder. Smaller MOF particles can be included in the shell of the core-shell structure of a second embodiment. Larger MOF particles can be used as the core of the core-shell structure of a third embodiment; such larger particles can be single crystals or can be formed by conventional aggregation techniques to form a core of the desired size.

[0039] There are several methods for preparing MOF compositions, but the most commonly used method is solvothermal synthesis. See, for example, Yujia Sun, Hong-Cai Zhou, Recent Progress in the Synthesis of Metal Organic Frameworks, Sci. Technol. Adv. Mater. 16(2015), 054202, which is incorporated herein by reference. In this process, a metal salt and the desired ligand / linker are dissolved in a suitable solvent and reacted for the required time at high temperature. Once the MOF is formed, the powder is separated from the reaction mixture, washed, and dried.

[0040] MOFs can be activated by heating (usually under reduced pressure) to remove solvents from the MOF composition. "Activation" as used herein with respect to MOF use means that the MOF adsorbs more pollutants than the as-synthesized MOF. For example, the activated MOF can adsorb at least 10% more, or at least 20% more, or at least 30% more, or at least 40% more, or at least 50% more, or at least 60% more, or at least 70% more, or at least 80% more, or at least 90% more. The activated MOF can adsorb 2, 3, 5, 10, 15, 20, 30, 50, or 100 times the amount of pollutants compared to the as-synthesized MOF.

[0041] Metal ions that can be used include, but are not limited to, Li+, Na+, K+, Rb+, Be2+, Mg2+, Ca2+, Sr2+, Ba2+, Sc3+, Y3+, Ti4+, Zr4+, Hf4+, V5+, V4+, V3+, Nb3+, Ta3+, Cr3+, Cr2+, Mo3+, W3+, Mn3+, Fe3+, Fe2+, Ru3+, Ru2+, Os3+, Os2+, Co3+, Co2+, Ni2+, Ni+, Pd2+, Pd+, Pd+, Pt2+, Pt+, Cu2+, Cu+, Ag+, Au+, Zn2+, Al3+, Ga3+, In3+, Si4+, Si2+, Ge4+, Ge2+, Sn4+, Sn2+, Bi5+, Bi3+, Cd2+, Mn2+, Tb3+, Gd3+, Ce3+, La3+ and Cr4+ and mixtures thereof. A subgroup of the metal ions is selected from Ti4+, Zr4+, Hf4+, Fe3+, Fe2+, Co3+, Co2+, Ni2+, Ni+, Cu2+, Cu+, Zn2+, Ga3+, Al3+ and mixtures thereof. From this subgroup, a subgroup of the metal ions includes those selected from Ti4+, Zr4+, Fe3+, Co3+, Ni2+, Cu2+, Zn2+, Ga3+, Al3+ and mixtures thereof. Another subgroup of the metal ions includes Fe3+, Cu2+, Zr4+ and Zn2+. In one embodiment, the metal ion is Zr4+.

[0042] The metal ion corner atoms are connected by at least bidentate organic linker molecules, which include two or more sites capable of binding to the metal ion corner molecules to form a metal-organic framework structure. Optionally, at least bidentate inorganic linker molecules can also be used. The at least bidentate organic linker molecules include, but are not limited to, those having a saturated or unsaturated alkyl or aryl framework, optionally including one or more heteroatoms S, N, O or P, and optionally including one or more functional groups bonded to the backbone. In certain embodiments, the linker backbone can include one or more groups selected from: 1) saturated or unsaturated, straight-chain, branched-chain or cyclic alkyl groups having 1 to 10 carbon atoms and optionally including heteroatoms; and 2) groups including 1 to 5 aryl or heteroaryl rings that can be fused or covalently linked; wherein the heteroatoms are selected from S, N, O, P and mixtures thereof. The backbone of the linker molecule can be bonded to one or more functional groups, including but not limited to saturated and unsaturated alkyl, aryl, heteroaryl, halides, -OH, -NH2, -COOH, NO2, COH, CO(NH2), CN and thiols. In one embodiment, the functional groups are selected from COOH and NH2.

[0043] Silicon halides, such as SiF6, can also be used as linkers in the framework structure.

[0044] Subgroups of these ligands include substituted or unsubstituted mononuclear or polynuclear aromatic dicarboxylic acids, tricarboxylic acids, and tetracarboxylic acids, as well as aromatic dicarboxylic acids, tricarboxylic acids, and tetracarboxylic acids that are unsubstituted or substituted by at least one heteroatom. In one embodiment, the ligands include, but are not limited to, 1,3,5-benzenetricarboxylic acid (BTC), triazine tribenzoic acid (TATB), 2-aminoterephthalic acid, naphthalene dicarboxylate (NDC), diacetylene dicarboxylate (ADC), benzene-1,4-dicarboxylic acid (BDC), benzenetricarboxylate (BTB), pentaerythritol tetrakis(benzoate) (MTB), adamantane tetracarboxylate (ATC), adamantane tris(benzoate) (ATB), 4,4',4'',4'''-(pyrene-1,3,6,8-tetrayl)tetrakis(benzoic acid) (TBAPy), meso-tetraphenylporphine-4,4',4'',4'''-tetracarboxylic acid (TCPPH2), 3,3',5,5'-azobenzenetetracarboxylic acid, 2,5-dihydroxyterephthalic acid, pyrazine, 1,4-diazabicyclo[2.2.2]octane, and mixtures thereof. In one embodiment, the ligands include, but are not limited to, terephthalic acid, azobenzenetetracarboxylic acid, trimesic acid, 1,4-diazabicyclo[2.2.2]octane, and mixtures thereof.

[0045] Specific MOFs suitable for the hybrid adsorbent particles disclosed herein include, but are not limited to, MOF-808, which includes Zr4+ building blocks and trimesic acid ligands; UiO-66, which includes Zr4+ building blocks and terephthalic acid ligands; UiO-66-NH2, which includes Zr4+ building blocks and aminoterephthalic acid ligands; PCN-250, which includes Fe3+ and azobenzenetetracarboxylic acid ligands; and mixtures of any of the foregoing.

[0046] In some embodiments, the MOF can be impregnated with a metal salt before incorporation into the adsorbent particles. In one embodiment, the MOF can be impregnated with a metal salt based on any one of Li+, Na+, K+, Rb+, Be2+, Mg2+, Ca2+, Sr2+, Ba2+, Sc3+, Y3+, Ti4+, Zr4+, Hf4+, V5+, V4+, V3+, Nb3+, Ta3+, Cr3+, Cr2+, Mo3+, W3+, Mn3+, Fe3+, Ru3+, Ru2+, Os3+, Os2+, Co3+, Co2+, Ni2+, Ni+, Pd2+, Pd+, Pt2+, Pt+, Cu2+, Cu+, Ag+, Au+, Zn2+, Al3+, Ga3+, In3+, Si4+, Si2+, Ge4+, Ge2+, Sn4+, Sn2+, Bi5+, Bi3+, Cd2+, Mn2+, Tb3+, Gd3+, Ce3+, La3+ and Cr4+ and mixtures thereof. In one embodiment, the MOF can be impregnated with a metal salt based on any one of Sc3+, Ti4+, V5+, V4+, V3+, Cr3+, Cr2+, Mn3+, Fe3+, Fe2+, Co3+, Co2+, Ni2+, Ni+, Cu2+, Cu+, Zn2+ and Ag+ and mixtures thereof.

[0047] Another adsorbent that can be used for the hybrid adsorbent particles of the present disclosure is zeolite. Zeolites are microporous crystalline aluminosilicate compositions formed from corner-sharing AlO2 and SiO2 tetrahedra. Many naturally occurring and synthetically prepared zeolites can be used in the practice of the present invention. Synthetic zeolites are prepared via hydrothermal synthesis using suitable sources of Si, Al, and structure-directing agents such as alkali metals, alkaline earth metals, amines, and / or organic ammonium cations. The structure-directing agents are present in the pores of the zeolite and are largely responsible for the specific structure ultimately formed. These substances balance the framework charge associated with aluminum and can also act as space fillers. Naturally occurring zeolites include, but are not limited to, faujasite, analcime, chabazite, clinoptilolite, heulandite, natrolite, phillipsite, stilbite, mordenite, erionite, offretite, and mixtures thereof. Among them, faujasite, chabazite, clinoptilolite, phillipsite, mordenite, erionite, offretite, and mixtures thereof are of particular interest. Synthetic zeolites include, but are not limited to, zeolite A, B, X, Y, L, α, β, ω, ZSM-5, silicalite, ZSM-11, MCM-22, ZK-4, EU-1, FU-1, NU-1, LZ-210, and mixtures thereof. Some or all of the silica in the zeolite can be replaced. For example, SAPO, ALPO, MeAPO, where Me is a metal selected from Li, Be, B, Mg, Mn, Si, Ti, Fe, Zn, Ga, Ge, As, and Cr. A review of the history of zeolites and their structures and characteristics can be found in Studies in Surface Science and Catalysis, vol. 137, H. van Bekkum, E.M. Flanigen, P.A. Jacobs, and J.C. Jansen (editors), 2001, Elsevier Science B.V., which is incorporated herein by reference.

[0048] Porous organic polymers (POPs) are polymerization products of at least multiple organic monomers. POPs are typically composed of multi-topic (three or more connection points) monomer units. While the degree of crosslinking in microporous polymer materials depends on the concentration of the added crosslinking molecules, the crosslinking in POPs is determined by the valence / topicity of the monomer or comonomer units. The crosslinking in POPs forms between rigid building blocks and is also different from the crosslinking in polymer gels, which typically forms between flexible chains and side chains. POPs are amorphous materials, and their synthesis is well known in the art. For example, POPs can be synthesized by the following reactions: 1) catechol and aryl halides; 2) anhydride monomers and diamine monomers; and 3) carboxylic acid monomers and diamine monomers.

[0049] Covalent organic frameworks (COFs) are a subset of POPs and are crystalline materials. Similarly, these materials and their synthesis are well known in the art.

[0050] Other suitable adsorbents include, but are not limited to, activated alumina and silica gel.

[0051] Binders suitable for adsorbent mixed particles include, but are not limited to, polymers such as polyvinylpyrrolidone, which are available within a certain molecular weight range; colloidal silica, such as those sold under a trademark; colloidal zirconia; colloidal alumina; carboxymethyl cellulose; and chitosan within a molecular weight range. Among them, polymers such as polyvinylpyrrolidone and colloidal silica are particularly suitable.

[0052] The adsorbent mixed particles of the present disclosure will have a selected average size to facilitate handling by filter manufacturers and optimize performance in the intended application. Smaller particles can be more effective adsorbents because the diffusion path of adsorbed contaminants through the adsorbent particles is shorter. However, when gas passes through a filter containing the adsorbent, smaller particles will result in a greater pressure drop. In one embodiment, the average diameter of the adsorbent mixed particles is at least 50 microns, or at least 100 microns, or at least 150 microns, or at least 200 microns, or at least 250 microns, or at least 500 microns, or at least 1000 microns, or at least 1500 microns, or at least 2000 microns, or at least 2500 microns, or at least 3000 microns. Further preferably, the adsorbent particles have a sufficiently narrow particle size distribution to prevent the formation of channels in the bed or filter structure. In various embodiments, the average size of the adsorbent particles is in the range of 600 - 1700 microns, or 400 - 800 microns, or 250 - 400 microns.

[0053] In each embodiment, the relative mass ratio of the first and second adsorbents will depend on the adsorption and deactivation required for the contaminants desired to be adsorbed. In various embodiments, the mass ratio of the first and second adsorbents can be in the range of 5:95 - 95:5, or in the range of 10:90 - 90:10, or in the range of 20:80 - 80:20, or in the range of 30:70 - 70:30, or in the range of 40:60 - 60:40.

[0054] The mixed adsorbent particles can include other materials, including but not limited to additional adsorbents and binders. For those adsorbent mixed particles in the form of a substantially random mixture of binder and adsorbent particles, the additional adsorbent material can be randomly dispersed in the particles. For adsorbent mixed particles in the form of a core - shell structure, the additional adsorbent can be present in the core, or in the adsorbent - binder shell, or both.

[0055] In each embodiment where one of the adsorbents comprises a MOF material, the MOF is synthesized prior to preparing the mixed adsorbent particles. Since the MOF is not grown in situ on a substrate, in pores, or on the surface of another adsorbent (such as porous carbon), or on a pre-existing binder or other shell structure, there are more choices in selecting the MOF to be used, better controlling the parameters in MOF synthesis, and better controlling the MOF particle size. The fact that the MOF is added to the mixed adsorbent particles in the form of prefabricated particles also allows for the use of multiple MOFs in any of the embodiments disclosed herein. Additionally, if impregnated carbon or other impregnated materials are used as one of the adsorbents, any impregnating substance will not interfere with the MOF synthesis nor will it be degraded by the MOF synthesis process.

[0056] In the embodiments shown herein, the adsorbent is activated carbon and a MOF material. It should be understood that these embodiments are chosen for illustrative purposes only and other adsorbents may be selected as described above.

[0057] Figure 1 A first embodiment of the adsorbent mixed particles 10 is shown, which comprises a substantially random mixture of carbon particles 12, MOF particles 14, and a binder 16. The method for preparing the first embodiment comprises the steps of: providing a mixture of carbon particles, MOF particles, and a binder; granulating the mixture with a liquid carrier to obtain carbon-MOF mixed particles, wherein at least some of the particles comprise a substantially random mixture of carbon particles, MOF particles, and a binder; and drying the mixed particles to remove the liquid carrier. The dried particles can be screened into a desired particle size range. The liquid carrier used to facilitate granulation during the granulation process can be any liquid that does not react with the MOF, the binder, the carbon, or any material impregnated in the MOF or the carbon. The dried particles can be activated at a desired temperature for a desired time and optionally under reduced pressure to remove any liquid carrier that may be present and optimize the adsorption performance. Optionally, multiple MOFs can be used, and multiple carbons can also be used, thereby optimizing the adsorption performance of the particles for a specific contaminant to be adsorbed.

[0058] Figure 2Shows a second embodiment of the adsorbent hybrid particles 20 in the form of a core-shell structure, which includes a core 22 and a shell 24. The core 22 includes carbon, and the shell 24 includes a mixture of a binder 26 and MOF 28 particles. The method for preparing the second embodiment includes the following steps: providing a certain amount of particles including carbon, providing a suspension including a binder and MOF material particles, coating the particles including carbon with the suspension, and drying the coated particles to provide hybrid particles with a core-shell structure, which includes a core and a shell, the core includes carbon, and the shell includes a mixture of a binder and particles including MOF. Optionally, the suspension can be ultrasonically treated before the coating step to break any aggregates, improve the uniformity of the suspension, and then filtered to remove any remaining large MOF particles. Suitable coating methods include pan coating, spraying, fluidized bed coating, and other methods known to those skilled in the art. The coating method can be carried out at room temperature or at a temperature up to 100°C. The drying step can be carried out under vacuum, at a high temperature, or both. The drying conditions will be selected based on the liquid carrier that must be removed. In one embodiment, the particles are air-dried overnight. Optionally, the particles can be activated under high temperature and / or dynamic vacuum, as described below.

[0059] The liquid carrier of the suspension can be any liquid that does not react with or dissolve the MOF particles, nor any material impregnated in the carbon. Suitable liquid carriers include water, methanol, chloroform, dichloromethane, and other common solvents. The liquid can be selected based on the stability of the suspension, the ease of drying, and the stability of any impregnated material in the carbon core or MOF material. Water and methanol are particularly suitable liquid carriers for the suspension.

[0060] The binder can be selected based on its compatibility with the liquid carrier. Suitable binders include polyvinylpyrrolidone with various molecular weights, other known polymer binders such as polyvinyl acetate, and colloidal silica, such as those sold under the trade name Those. Polyvinylpyrrolidone with a molecular weight of 360,000 is particularly suitable. Other suitable binders can include colloidal zirconia; colloidal alumina; carboxymethyl cellulose; and chitosan within a certain molecular weight range. Other materials can be included in the suspension, such as tackifiers, foam inhibitors, pH controllers, and flow enhancers.

[0061] The size of the MOF particles in the coating suspension will be larger than the pores of the carbon, but may also vary depending on the coating technique used. If spraying is used, the size of the MOF particles is usually small enough not to clog the nozzle. The size of the coated MOF particles can be less than 100 microns, or less than 75 microns, or less than 50 microns, or less than 25 microns, or less than 10 microns, or less than 5 microns, or less than 1 micron, down to about 0.5 microns.

[0062] The suspension for coating MOF particles onto carbon particles may include 10 - 50 wt% MOF particles; up to 3 wt%, or up to 10 wt%, or up to 15 wt%, or up to 20 wt% binder based on the dry MOF; up to a total of 5 wt% of other optional materials such as tackifiers, foam inhibitors, pH control agents, and flow enhancers based on the dry weight of the MOF; and a balance of liquid carrier.

[0063] Figure 3 A third embodiment of the adsorbent hybrid particle 30 in the form of a core - shell structure is shown, which core - shell structure includes a core 32 and a shell 34. The core 32 includes MOF material, and the shell 34 includes a mixture of a binder 36 and carbon particles 38. The method for preparing the third embodiment includes the steps of: providing an amount of particles including MOF material, providing a suspension including a binder and particles including carbon, coating the particles including MOF material with the suspension, and drying the coated particles to provide hybrid particles having a core - shell structure, which core - shell structure includes a core and a shell, the core includes MOF material, and the shell includes a mixture of a binder and particles including carbon. Optionally, the suspension can be sonicated prior to the coating step to break up any aggregates, improve the uniformity of the suspension, and then filtered to remove any remaining large carbon particles. Suitable coating processes include pan coating, spraying, fluidized bed coating, and other methods known to those skilled in the art. The coating process can be carried out at room temperature or at a temperature up to 100 °C. The drying step can be carried out under vacuum, or at high temperature, or both. The drying conditions will be selected based on the liquid carrier that must be removed. In one embodiment, the particles are air - dried overnight. Optionally, the particles can be activated under high temperature and / or dynamic vacuum as described below.

[0064] The size of the carbon particles in the coating suspension can vary depending on the coating technique used. If spraying is used, the size of the carbon particles is typically small enough so as not to clog the nozzle. The size of the coated carbon particles can be less than 100 microns, or less than 75 microns, or less than 50 microns, or less than 25 microns, or less than 10 microns, or less than 5 microns, or less than 1 micron, down to about 0.5 microns.

[0065] The suspension for coating carbon particles onto a core including MOF material may include 10 - 50 wt% carbon particles; up to 3 wt%, or up to 10 wt%, or up to 15 wt%, or up to 20 wt% binder based on the dry weight of the activated carbon; up to a total of 5 wt% of other optional materials such as tackifiers, foam inhibitors, pH control agents, and flow enhancers based on the dry weight of the carbon; and a balance of liquid carrier.

[0066] Regardless of the manufacturing method, the adsorbent mixed particles disclosed herein can be activated by heating (usually under reduced pressure) to remove the solvent from the dried particles. "Activation" as used herein with respect to the adsorbent mixed particles means that the adsorbent mixed particles adsorb more contaminants than the synthesized adsorbent mixed particles. For example, the activated adsorbent mixed particles can adsorb at least 10% or more, or at least 20% or more, or at least 30% or more, or at least 40% or more, or at least 50% or more, or at least 60% or more, or at least 70% or more, or at least 80% or more, or at least 90% or more. Compared with the synthesized adsorbent particles, the activated adsorbent mixed particles can adsorb 2, 3, 5, 10, 15, 20, 30, 50, or 100 times the amount of contaminants.

[0067] The adsorbent mixed particles disclosed herein are characterized in that they can adsorb various molecules. Thus, they can be used to purify a gas stream by at least partially adsorbing at least one contaminant in the gas stream. The gas streams that may need to be purified include, but are not limited to, air streams, industrial gas streams, waste gas streams, or contaminant gas streams. The contaminants to be adsorbed include, but are not limited to, toxic industrial chemicals and CBRN contaminants. In some embodiments, the adsorbent can be selected such that the adsorbent mixed particles can adsorb contaminants selected from the group consisting of ammonia, chlorine, cyanogen chloride, hydrogen cyanide, hydrogen sulfide, phosgene, sulfur dioxide, boron tribromide, boron trichloride, bromine, bromine chloride, bromine trifluoride, carbonyl fluoride, chlorine, chlorine pentafluoride, chlorine trifluoride, chlorosulfonic acid, dichlorosilane, ethyl phosphorodichloridite, fluorine, hydrogen bromide, hydrogen chloride, hydrogen fluoride, hydrogen iodide, phosphorus trichloride, silicon tetrafluoride, sulfur trioxide, sulfuric acid, thionyl chloride, titanium tetrachloride, tungsten hexafluoride, bromine pentafluoride, hydrogen selenide, nitric acid, nitrogen dioxide, dinitrogen tetroxide, nitrogen trioxide, and mixtures of any two or more of the foregoing. The amount of contaminants that the adsorbent particles can remove is at least 50%, or at least 60%, or at least 70%, or at least 80%, or at least 90%, or at least 95%, or at least 99% of the contaminants.

[0068] The present invention also provides an apparatus comprising adsorbent mixed particles. In one embodiment of such an apparatus, a container having an inlet and an outlet is filled with the mixed adsorbent particles, and a gas stream flows through the mixed adsorbent particles, thereby substantially removing one or more contaminants from the gas stream. To achieve the desired removal amount, the gas stream flows through the adsorbent particles at a rate of about 10 L / min to about 500 L / min, or about 30 L / min to about 200 L / min, or about 50 L / min to about 120 L / min.

[0069] In one embodiment, a device comprising a mixed particle adsorbent can be, for example, a respirator for personal protective equipment and having a filter including adsorbent mixed particles. In one filter embodiment, the particles can be adhered to a substrate to form a filter structure layer. In another filter embodiment, the adsorbent can be loaded into a filter element that is removably mounted in the respirator structure. In either case, as disclosed herein, the fact that multiple adsorbent functions are provided in a single particle adsorbent product will simplify the manufacturing process of the filter structure of the device or the respirator filter element.

[0070] Examples

[0071] Example 1 - Zr-BDC-NH2 (UiO-66-NH2) MOF particles coated on impregnated activated carbon

[0072] A mixture of 20 g of Zr-BDC-NH2 MOF (30 wt% H2O solvate) in 100 ml of water was sonicated to disperse the MOF into a uniform suspension. 0.42 g of PVP binder was added to the suspension and dissolved. The suspension was filtered through a 53 μm sieve to remove large particles and then loaded into an aerosol-based spray system. 80 g of impregnated 12x30 mesh activated carbon particles (Calgon carbon Corporation) were loaded into a pan coater, which had been pre-activated at 200 °C for 16 hours. While the pan coater tumbled the carbon particles, the MOF suspension was sprayed onto the carbon particles until the fluidity of the carbon bed was significantly reduced. Heated air was applied to the coated particles to evaporate the solvent and restore fluidity. During drying, the particle bed was stirred with a stainless steel spatula. When the fluidity of the particle bed was restored, the spraying and drying processes were repeated until the desired amount of MOF was coated onto the carbon core. Nitrogen isotherms showed that MOF coating did not reduce the nitrogen uptake of carbon in the mixed adsorbent particles. Ammonia isotherms showed that MOF coating provided ammonia adsorption capacity to the mixed adsorbent particles. The molecular weight of the binder can be selected to reduce the dust content of the dried mixed adsorbent particles.

[0073] Example 2 - Activation of mixed adsorbent particles

[0074] Mixed adsorbent particles of impregnated activated carbon and Zr-BDC-NH2 MOF were prepared according to the general procedure of Example 1, but with different weight ratios of MOF to carbon, then sieved to 12 to 30 mesh and activated at 100 °C for about 18 hours, or until the pressure in the activation chamber was less than 0.1 torr. Nitrogen and ammonia isotherms showed that as the MOF loading increased, the uptake of N2 and NH3 increased. The theoretically calculated isotherms fit well with the weighted average of the pure MOF and carbon components at different loadings.

[0075] Example 3 - Carbon particles coated with impregnated MOF

[0076] A sample of coated particles was prepared using the procedure of Example 1, except that ZnCl2 was included in the MOF suspension mixture at a Zn:Zr mass ratio of 0.1:1 to provide an impregnated Zn Zr OF coating on the carbon particles. The MOF loading on the particles was 25 wt%. It was found that the MOF with the zinc-impregnated coating did not significantly reduce the N2 absorption, while the NH3 absorption was improved.

[0077] Example 4 - Mixture of MOF Particles and Carbon Particles

[0078] Adsorbent mixed particles composed of a mixture of activated carbon particles and MOF particles were prepared. The powders of MOF, activated carbon, and binder were mixed in a granulator. When the solid mixture was ground in the granulator, water as a liquid carrier was slowly added to facilitate the formation of MOF and activated carbon particles. The mixture was prepared from charcoal powder with a particle size in the range of 150 microns, Zr-BTC-NH2 MOF powder with a particle size in the range of 3 - 5 microns as prepared in Example 1, and 5% PVP binder. The ammonia isotherm showed that the mixed adsorbent particles had good ammonia adsorption.

[0079] Although the mixed adsorbent particles, their manufacturing methods, and filters and methods of use have been described in detail in conjunction with the above description and examples, it should be understood that these details are for that purpose only, and those skilled in the art can make variations without departing from the spirit of the present disclosure, unless restricted by the following claims.

Claims

1. A composition comprising adsorbent mixed particles, characterized in that, Wherein the particles comprise a first adsorbent material, a second adsorbent material, and a binder, the binder being mixed with the first adsorbent material or the second adsorbent material or both, and wherein the first adsorbent material and the second adsorbent material are each located externally of the surface of the other adsorbent material.

2. The composition according to claim 1, characterized in that, Wherein the particles comprise a substantially random mixture of particles of the first adsorbent material, particles of the second adsorbent material, and the binder.

3. The composition according to claim 1, wherein Wherein the particles are in the form of a core-shell structure, the core-shell structure comprising a core and a shell, the core comprising at least one particle of the first adsorbent material, and the shell comprising a substantially random mixture of the binder and particles of the second adsorbent material.

4. The composition according to claim 1, wherein Wherein the first adsorbent and the second adsorbent are independently selected from carbonaceous adsorbents, metal-organic framework (MOF) materials, zeolites, porous organic polymers, covalent organic frameworks, activated alumina, and silica gel.

5. The composition according to claim 4, wherein Wherein the first adsorbent and the second adsorbent are selected from carbonaceous adsorbents and MOF materials.

6. The composition according to claim 5, characterized in that, Wherein the carbonaceous adsorbent comprises activated carbon.

7. The composition according to claim 6, characterized in that, Wherein the activated carbon is impregnated activated carbon.

8. The composition according to claim 5, wherein Wherein the mixed adsorbent particles further comprise a second type of MOF.

9. The composition according to claim 5, characterized in that, Among them, the MOF material includes metal ions, and the metal ions are selected from the group consisting of: Li + , Na + , K + , Rb + , Be 2+ , Mg 2+ , Ca 2+ , Sr 2+ , Ba 2+ , Sc 3+ , Y 3+ , Ti 4+ , Zr 4+ , Hf 4+ , V 5+ , V 4+ , V 3+ , Nb 3+ , Ta 3+ , Cr 3+ , Cr 2+ , Mo 3+ , W 3+ , Mn 3+ , Fe 3+ , Fe 2+ , Ru 3+ , Ru 2+ , Os 3+ , Os 2+ , Co 3+ , Co 2 + , Ni 2+ , Ni + , Pd 2+ , Pd + , Pt 2+ , Pt + , Cu 2+ , Cu + , Ag + , Au + , Zn 2+ , Al 3+ , Ga 3+ , In 3+ , Si 4+ , Si 2+ , Ge 4+ , Ge 2+ , Sn 4+ , Sn 2+ , Bi 5+ , Bi 3+ , Cd 2+ , Mn 2+ , Tb 3+ , Gd 3+ , Ce 3+ , La 3+ and Cr 4+ and mixtures thereof.

10. The composition according to claim 5, characterized in that, Wherein the MOF material comprises at least one organic ligand selected from: 1,3,5-benzenetricarboxylic acid (BTC), triazine tribenzoic acid (TATB), 2-aminoterephthalic acid, dimethyl naphthalenedicarboxylate (NDC), diacetylene dicarboxylate (ADC), benzene-1,4-dicarboxylic acid (BDC), benzenetricarboxylate (BTB), pentaerythritol tetrakis(benzoate) (MTB), adamantane tetracarboxylate (ATC), adamantane tris(benzoate) (ATB), 4,4',4”,4”'-(pyrene-1,3,6,8-tetrayl)tetrabenzoic acid (TBAPy), meso-tetraphenylporphine-4,4',4”,4”'-tetracarboxylic acid (TCPPH2), 3,3',5,5'-azobenzenetetracarboxylic acid, 2,5-dihydroxyterephthalic acid, pyrazine, 1,4-diazabicyclo[2.2.2]octane, and mixtures thereof.

11. The composition according to claim 5, wherein Wherein the MOF material comprises one or more MOFs selected from MOF-808, UiO-66, UiO66-NH2, and PCN-250.

12. The composition according to claim 5, wherein Wherein the MOF material is impregnated with a metal compound.

13. A device, characterized in that, Comprising the composition according to claim 1.

14. A filter, characterized in that, Comprising the composition according to claim 1.

15. The device according to claim 13, characterized in that, Wherein the device is a respirator.

16. A method for preparing adsorbent mixed particles, characterized in that, Comprising the following steps: Providing a mixture of particles of a first adsorbent material, particles of a second adsorbent material, and a binder; granulating the mixture with a liquid carrier to obtain mixed particles, wherein at least some of the particles comprise a substantially random mixture of particles of the first adsorbent material, particles of the second adsorbent material, and the binder; and drying the mixed particles.

17. A method for preparing adsorbent mixed particles, characterized in that, The method comprises the following steps: providing a quantity of particles comprising a first adsorbent material, providing a suspension in a liquid carrier of particles comprising a binder and a second adsorbent material, coating the particles comprising the first adsorbent material with the suspension, and drying the coated particles.

18. The method according to claim 17, wherein Wherein the first adsorbent material comprises a carbonaceous adsorbent and the second adsorbent material comprises a MOF material.

19. The method according to claim 17, wherein Wherein the first adsorbent material comprises a MOF material and the second adsorbent material comprises a carbonaceous adsorbent.

20. A method for purifying an air stream, characterized in that, The method comprises passing the gas stream through the composition according to claim 1.

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