Hybrid adsorbent granules and filters made with the granules

Abstract

A composition comprising adsorbent hybrid granules, wherein said granules comprise a first adsorbent material, a second adsorbent material, and a binder mixed with either 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. The adsorbent composition is suitable for use in purifying an air stream, and in particular is suitable for use in filters for respirators.

Description

[0001] NUM024 HYBRID ADSORBENT GRANULES AND FILTERS MADE WITH THE GRANULES STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

[0001] This invention was made with U.S. Government support under Agreement No. CWMD1820-004 awarded by the Combat Capabilities Development Command Chemical Biological Center, pursuant to Base Agreement No.2018-875A, Other Transaction Agreement (OTA) No. W15QKN-18-9-1004. The Government has certain rights in the invention. FIELD OF THE DISCLOSURE

[0002] This disclosure relates to hybrid adsorbent granules comprising two or more adsorbent materials, to methods of making the hybrid adsorbent granules, and to compositions, apparatuses, and filters made using the hybrid adsorbent granules. This disclosure further relates to such adsorbents, methods, compositions, apparatuses and filters wherein the hybrid adsorbent granules can be in the form of core-shell structures or blended hybrid granules. BACKGROUND OF THE DISCLOSURE

[0003] Adsorbents are used in many different environments and applications, to capture a wide variety of desired species, or to capture contaminants, pollutants, or other undesired species in a fluid stream. When a fluid stream contains a mixture of species to be captured by adsorption, more than one type of adsorbent may be required to ensure that the different species are captured. Yet different adsorbents can have different physical as well as chemical properties, such that providing a uniform mixture of adsorbents is a challenge.

[0004] One application of adsorbents is to remove pollutants and other contaminants from an air stream. For this purpose, it is known to use adsorbents in filters placed in apparatuses 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 within a hazard zone. Such hazard zones can include areas or situations in which there is potential exposure to a range of threats including toxic industrial chemicals (TICs); and chemical, biological, radiological, or nuclear-based NUM024 (CBRN) hazards, which can include chemical warfare agents (CWAs). In such hazard zones an individual must be provided with personal protective equipment (PPE) that offers protection against multiple threats. In particular, air respirators should provide protection against a broad range of air-borne hazardous contaminants. In such applications, a single type of adsorbent may not be adequate to capture multiple airborne contaminants.

[0005] It is known to use activated carbon as a filter material in air respirators for PPE use. Activated carbon is a porous broad spectrum adsorbent, but is less effective for most TICs, CBRN, or CWA contaminants, such as ammonia. It is further known that activated carbon can be impregnated with metals or other chemical species to enhance the adsorption capacity of selected hazardous contaminants. But even impregnated activated carbon will not adsorb certain hazardous contaminants. 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 contaminants that activated carbon does not.

[0006] The use of multiple adsorbent materials in a single filter construction can create challenges in the manufacture of such filter constructions and respirators and other apparatuses incorporating such filter constructions. For example, if a respirator filter is constructed using layers of different adsorbents, it can be challenging to create multiple layers of consistent thickness, which is necessary for consistent filtration performance across multiple contaminants. For example, the use of multiple layers of different adsorbent materials in a single filter construction can result in different breakthrough times for different contaminants. The use of such multiple layers of different adsorbents also creates additional manufacturing steps which can add to the cost of the filter. Further, the use of such multiple layers of different adsorbents can create challenges in design complexity, require process changes for high-throughput equipment, and create other variations in performance such as may be caused by pin holes or channels in the various layers. In addition, the use of multiple adsorbent layers can add to the thickness of the filter construction; this is disadvantageous as filters having thinner profiles are preferred in modern respirator design.

[0007] US 9,095,839 discloses a hybrid composite of metal organic frameworks (MOFs) encapsulated in nanocarbon material, wherein the MOFs are grown inside, outside or both inside NUM024 and outside of nano carbon morphologies, to provide an adsorbent that can be used to adsorb H2, N2, or CO2.

[0008] US 9,566,575 discloses a composite material of a metal-organic framework and activated carbon wherein a metal-organic framework substance is produced in situ in the pores and / or the pore system of the activated carbon, starting from a metal precursor compound containing at least one metal and at least one ligand precursor.

[0009] KR101638049B1 discloses core-shell structures 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 selective for gases such as CO2, Ar, Ne, He, CF4, H2, N2, O2, and CnH2n+2.

[0010] Each of the foregoing references discloses a MOF-hybrid composition in which the MOF material is synthesized directly on the surface of or in the pores of the other material in the composition. This complicates the manufacturing process, and inherently limits the types of MOFs that can be used in the adsorbent compositions.

[0011] It is one object of the disclosure to provide an adsorbent composition that comprises a plurality of adsorbent materials to provide adsorbency for a variety of species in a fluid stream.

[0012] It is another object of the disclosure to provide an adsorbent composition that comprises a plurality of adsorbent materials to provide adsorbency for a variety of airborne hazardous substances.

[0013] It is another object of the disclosure to provide such an adsorbent composition that is suitable for use in air respirators for PPE use.

[0014] It is another object of the disclosure to provide a method of making such an adsorbent composition.

[0015] It is another object of the disclosure to provide an apparatus comprising such an adsorbent composition.

[0016] It is another object of the disclosure to provide a method of purifying a gaseous stream, the method comprising passing the gaseous stream through an apparatus comprising the adsorbent composition. NUM024 SUMMARY OF THE DISCLOSURE

[0017] The foregoing objects of the disclosure are met by a composition comprising adsorbent hybrid granules, wherein said granules comprise a first adsorbent material, a second adsorbent material, and a binder mixed with either 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 surfaces of the other adsorbent material. In one embodiment the adsorbent hybrid granules comprise a substantially random mixture of the first adsorbent material, the second adsorbent material, and a binder. In one embodiment the adsorbent hybrid granules are in the form of core-shell structures comprising a core comprising a first adsorbent material and a shell comprising a substantially random mixture of a binder and a second adsorbent material.

[0018] The first and second adsorbent materials can be selected based on their ability to adsorb different species in a fluid stream. Adsorbents 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 hybrid adsorbent granules can comprise three or more different adsorbent materials. In one aspect of the invention 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 particles, and a binder is mixed with either the carbon particles, the MOF material, or both. In one embodiment, the adsorbent composition comprises adsorbent hybrid granules comprising a substantially random mixture of carbon particles, MOF particles, and a binder. In another embodiment, the adsorbent composition comprises adsorbent hybrid granules in the form of core-shell structures comprising a core comprising at least one carbon particle and a shell comprising a substantially random mixture of a binder and particles of MOF. In yet another embodiment, the adsorbent composition comprises adsorbent hybrid granules in the form of core-shell structures comprising a core comprising a MOF material and a shell comprising a substantially random mixture of a binder and particles of carbon. In each embodiment, the MOF can be selected based on its capacity to adsorb contaminants for which the carbon particles provide less adsorbency. In each embodiment the MOF material is external to the surface of the carbon particles, and in particular external to the pores of the carbon particles. NUM024

[0019] One process for preparing hybrid adsorbent granules comprises the steps of providing a mixture comprising particles of a first adsorbent, particles of a second adsorbent and a binder; granulating the mixture with a liquid vehicle to achieve hybrid adsorbent granules wherein at least some of the granules comprise a substantially random mixture of first adsorbent particles, second adsorbent particles, and binder; and drying the hybrid adsorbent granules to remove the liquid vehicle. In one embodiment of this process the first adsorbent can comprise carbon particles and the second adsorbent can comprise MOF particles.

[0020] Another process for preparing hybrid adsorbent granules comprises the steps of providing a quantity of particles comprising a first adsorbent, providing a suspension comprising a binder and particles of a second adsorbent in a liquid vehicle, coating the particles comprising the first adsorbent with the suspension, and drying the coated particles to provide hybrid adsorbent granules having a core-shell structure comprising a core comprising a first adsorbent and a shell comprising a substantially random mixture of binder and particles of the second adsorbent. In one embodiment of this process the first adsorbent comprises particles of carbon, the second adsorbent comprises particles of MOF, a suspension comprising particles of MOF and a binder is coated onto the particles of carbon, and the coated particles are dried, to provide hybrid adsorbent granules comprising a core comprising carbon and a shell comprising a substantially random mixture of binder and particles of MOF. In another embodiment of this process the first adsorbent comprises particles comprising MOF, the second adsorbent comprises particles comprising carbon, a suspension comprising particles of carbon and a binder is coated onto the particles comprising MOF, and the coated particles are dried, to provide hybrid adsorbent granules comprising a core comprising a MOF material and a shell comprising a substantially random mixture of binder and particles comprising carbon. Other adsorbents as disclosed herein can be used for the first and second adsorbents of the process.

[0021] 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.

[0022] In each of the processes for making the hybrid adsorbent granules, the liquid vehicle can be any liquid that is non-reactive with the first adsorbent, the second adsorbent, and binder. In some embodiments water or methanol can be used as liquid vehicles. NUM024

[0023] In each of the processes for making the hybrid adsorbent granules, the dried hybrid granules can be sieved to achieve a desired particle size range. The adsorbent hybrid granules also can be activated by heating at a desired temperature and for a desired duration to optimize adsorbent performance.

[0024] This disclosure further relates to an apparatus comprising an adsorbent composition as disclosed herein. In one embodiment the apparatus can comprise a filter for filtering contaminants from a gaseous stream, the filter comprising a composition comprising adsorbent hybrid granules as disclosed herein. Advantageously, the hybrid adsorbent granules as disclosed herein can be readily incorporated in a single step into a filter construction for use in an apparatus such as an air respirator as a component of PPE, thereby obviating separate steps for assembling separate adsorbent materials in a filter construction.

[0025] The hybrid adsorbent granules also can be used in apparatuses used to provide collective protection, such as air purification systems for buildings and vehicles.

[0026] This disclosure further relates to a process for purifying a gaseous stream, the process comprising passing the gaseous stream through an apparatus comprising adsorbent hybrid granules comprising a first adsorbent, a second adsorbent, and a binder mixed with either the first adsorbent, 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 surfaces of the carbon. DESCRIPTION OF THE FIGURES

[0027] Fig.1 is a schematic diagram of a hybrid adsorbent granule comprising a substantially random mixture of carbon particles, MOF particles and a binder.

[0028] Fig.2 is a schematic diagram of a hybrid adsorbent granule comprising a core of carbon and a shell comprising a substantially random mixture of MOF particles and a binder.

[0029] Fig.3 is a schematic diagram of a hybrid adsorbent granule comprising a core of MOF material and a shell comprising a substantially random mixture of particles of carbon and a binder. NUM024 DETAILED DESCRIPTION OF THE DISCLOSURE

[0030] Disclosed herein is a composition comprising adsorbent hybrid granules comprising a first adsorbent material, a second adsorbent material, and a binder mixed with either 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.

[0031] The term “external to the surface” as used herein with respect to a porous adsorbent means that another adsorbent is not disposed within the pores of the porous adsorbent.

[0032] In one embodiment of the composition the adsorbent hybrid granules comprise a substantially random mixture of the first adsorbent material, the second adsorbent material, and a binder. In one embodiment the adsorbent composition comprises adsorbent hybrid granules in the form of core-shell structures comprising a core comprising a first adsorbent material and a shell comprising a substantially random mixture of a binder and a second adsorbent material.

[0033] The first and second adsorbent materials can be selected based on their ability to adsorb different species in a fluid stream. Adsorbents 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 invention the first and second adsorbents are selected from carbon particles and at least one MOF material external to the pores of the carbon particles. In one embodiment, at least some of the adsorbent granules comprise a substantially random mixture of carbon particles, MOF particles, and a binder. In another embodiment, the granules are in the form of core-shell structures comprising a core comprising at least one carbon particle and a shell comprising a substantially random mixture of a binder and particles of MOF material. In yet another embodiment, the granules are in the form of core-shell structures comprising a core comprising a MOF material and a shell comprising a substantially random mixture of a binder and particles of carbon.

[0034] The carbon can be of any type commercially available and known for use as an adsorbent. In some embodiments charcoal can be used as an adsorbent. In some embodiments activated carbon can be particularly suitable as an adsorbent in the hybrid adsorbent granules disclosed herein. Activated carbon is a highly porous, high surface area adsorptive material with a largely amorphous structure. It is composed primarily of aromatic configurations of carbon NUM024 atoms joined by random cross-linkages. The degree of order varies based on the starting raw material and thermal history. Graphitic platelets in steam-activated coal are somewhat ordered, while more amorphous aromatic structures are found in chemically activated wood. Randomized bonding creates a highly porous structure with numerous cracks, crevices and voids between the carbon layers. Activated carbon sorbents are tailored for specific applications mainly based on pore size and pore volume requirements. Porosity and other parameters are controlled by the following: 1) raw material selection; 2) activation process conditions; and 3) post-processing steps. Depending on the application, activated carbon may be in the form of powder (PAC), granule (GAC) or extrudate (EAC). A review of the fundamentals of activated carbon can be found in an article entitled: Activated Carbon: Fundamentals and New Applications, Ken Koehlert, Chemical Engineering, July 2017, pp.32-40, which is incorporated by reference. One brand of activated carbon that may be suitable in the disclosed hybrid granules is Maxsorb® high surface area activated carbon.

[0035] All three forms of activated carbon are available in a range of particle sizes ranging from a powder of diameter less than one micron, up to granules of diameter 6 mesh (3360 microns) or greater. Particles of activated carbon of at least one micron are preferred for ease of handling. The particles of activated carbon as used in the adsorbent granules disclosed herein can be at least one 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 hybrid granule comprises a mixture of activated carbon particles and MOF particles. Granules of at least one micron can be used in the second embodiment wherein the activated carbon is to be the core of a core-shell adsorbent structure. Smaller size particles such as powders can be used in the third embodiment wherein the activated carbon particles are to be included in a shell of a core-shell structure. In one embodiment the activated carbon can be in the form of granules in the range of 12 x 30 mesh, or from about 590 microns to about 1700 microns.

[0036] In some embodiments the activated carbon as used herein can be impregnated with other materials such as metals, metal oxides, or other chemical species to provide additional functionality to the adsorbent granules. Impregnated activated carbon materials are known in the art to be useful adsorbents for purifying flue gases, industrial gases, and the like. As used in the NUM024 hybrid adsorbent granules as disclosed herein, the material to be impregnated in the activated carbon will be selected based upon the anticipated contaminants to be adsorbed and optionally deactivated, as well as compatibility with the vehicles, solvents, and binders used in the methods of preparing the adsorbent granules as disclosed herein. Suitable activated carbons include those available from Calgon Carbon Corporation, Moon Township, PA, and particularly granular activated carbon products such as those sold by Calgon Carbon Corporation that are known to be useful for personal protective equipment.

[0037] Metal organic frameworks are well known porous adsorbents with high surface areas. MOFs comprise metal ion corner atoms and an at least bidentate linker molecule or a ligand, which is connected to the corner atom(s) thereby forming a framework structure. The metals of the clusters and the ligands each can be selected to control both the porosity of the MOF and its ability to chemically interact with other molecules. Thus, MOFs can be designed and selected to optimize both adsorbency and degradation activity toward particular contaminants. MOFs can be provided in particle sizes ranging from nano-sized particles to up to 500 microns in diameter. MOF particles of any size can be used in the first embodiment wherein substantially each adsorbent granule comprises a substantially random mixture of carbon particles, MOF particles, and a binder. Smaller MOF particles can be included in a shell of a core-shell structure of the second embodiment. Larger MOF particles can be used as the core of a core-shell structure of the third embodiment; such larger particles can be single crystals or can be formed by conventional aggregation techniques to form a core of a desired size.

[0038] There are several ways to prepare MOF compositions but the most commonly used one is the solvothermal synthesis. For example, see Yujia Sun and Hong-Cai Zhou, Recent Progress in the Synthesis of Metal Organic Frameworks, Sci. Technol. Adv. Mater.16 (2015), 054202 which is incorporated by reference. In this procedure a metal salt and the desired ligand / linker are dissolved in an appropriate solvent and reacted at an elevated temperature for a required time. Once the MOF is formed, the powder is isolated from the reaction mixture, washed and dried.

[0039] MOFs can be activated by heating, typically under reduced pressure, to remove solvent from the MOF composition. “Activated” as used herein with respect to MOFs means that the MOF adsorbs more of a contaminant than an 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% NUM024 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 contaminant versus an as synthesized MOF.

[0040] The metal ions which 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+, 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 one subgroup of metal ions includes those selected from Ti4+, Zr4+, Fe3+, Co3+, Ni2+, Cu2+, Zn2+, Ga3+, Al3+ and mixtures thereof. Another subgroup of metal ions includes Fe3+, Cu2+, Zr4+, and Zn2+. In one embodiment the metal ion is Zr4+.

[0041] The metal ion corner atoms are joined by at least bidentate organic linker molecules comprising two or more sites capable of binding to a metal ion corner atom to form a metal organic framework structure. Optionally, at least bidentate inorganic linker molecules also can be used. The at least bidentate organic linker molecules include but are not limited to those having a saturated or unsaturated alkyl or aryl backbone, optionally comprising one or more heteroatoms S, N, O, or P, and optionally comprising one or more functional groups bonded to the backbone. In certain embodiments the linker backbone can comprise one or more groups selected from 1) saturated or unsaturated, linear, branched or cyclic alkyl groups having from 1 to 10 carbon atoms and optionally comprising heteroatoms; and 2) groups comprising 1 to 5 aryl or heteroaryl rings which can be fused or joined covalently; wherein the hetero atoms are selected from S, N, O, P and mixtures thereof. The backbones of the linker molecules may have bonded thereto one or more functional groups, including but not limited to saturated and unsaturated alkyl, aryl, heteroaryl, halide, -OH, -NH2, -COOH, NO2, COH, CO(NH2), CN and thiols. In one embodiment the functional groups are selected from COOH and NH2.

[0042] Silicon halides such as SiF6 also may be used as linkers in the framework structure.

[0043] A subgroup of these ligands includes substituted or unsubstituted, mono- or polynuclear aromatic di-, tri- and tetracarboxylic acids and unsubstituted or substituted, with at least one NUM024 hetero atom, aromatic di-, tri- and tetracarboxylic acids. In one embodiment the ligands include without limitation 1,3,5-benzene tricarboxylic acid (BTC), triazine tris-benzoic acid (TATB), 2- amino-terephthalic acid, naphthalene dicarboxylate (NDC), acetylene dicarboxylate (ADC), benzene-1,4- dicarboxylic acid (BDC), benzene tribenzoate (BTB), methane tetrabenzoate (MTB), adamantane tetracarboxylate (ATC), adamantane tribenzoate (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. In one embodiment the ligands include without limitation terephthalic acid, azobenzene tetracarboxylic acid, trimesic acid, 1,4-diazabicyclo[2.2.2]octane, and mixtures thereof.

[0044] Specific MOFs suitable for use in the hybrid adsorbent granules as disclosed herein include without limitation MOF-808 which comprises Zr4+ cornerstones and trimesic acid ligands; UiO-66 which comprises Zr4+ cornerstones and terephthalic acid ligands; UiO-66-NH2 which comprises Zr4+ cornerstones and amino-terephthalic acid ligands; PCN-250 which comprises Fe3+ and azobenzene tetracarboxylic acid ligands; and mixtures of any of the foregoing.

[0045] In some embodiments the MOFs can be impregnated such as with metal salts prior to incorporation in the adsorbent granules. In one embodiment the MOFs can be impregnated with metal salts based on any 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+, Fe2+, 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 MOFs can be impregnated with metal salts based on any of Sc3+, Ti4+, V5+, V4+, V3+, Cr3+, Cr2+, Mn3+, Fe3+, Fe2+, Co3+, Co2+, Ni2+, Ni+, Cu2+, Cu+, Zn2+, and Ag+, and mixtures thereof.

[0046] Another adsorbent which can be used in the hybrid adsorbent granules of the disclosure is a zeolite. Zeolites are crystalline aluminosilicate compositions that are microporous and that are formed from corner sharing AlO2 and SiO2 tetrahedra. Numerous zeolites, both naturally occurring and synthetically prepared, can be used in the practice of the invention. Synthetic zeolites are prepared via hydrothermal synthesis employing suitable sources of Si, Al, and NUM024 structure directing agents such as alkali metals, alkaline earth metals, amines, and / or organoammonium cations. The structure-directing agents reside in the pores of the zeolite and are largely responsible for the particular structure that is ultimately formed. These species balance the framework charge associated with aluminum and can also serve as space fillers. The naturally occurring zeolites include but are not limited to faujasite, analcime, chabazite, clinoptilolite, heulandite, natrolite, phillipsite, stilbite, mordenite, erionite, offretite, ferrierite and mixtures thereof. Of these, faujasite, chabazite, clinoptilolite, phillipsite, mordenite, erionite, offretite, ferrierite and mixtures thereof are of particular interest. Synthetic zeolites include without limitation zeolites A, B, X, Y, L, alpha, beta, omega, ZSM-5, silicalite, ZSM-11, MCM- 22, ZK-4, EU-1, FU-1, NU-1, LZ-210 and mixtures thereof. Part or all of the silica in a zeolite can be substituted. 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 along with 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 by reference.

[0047] Porous organic polymers (POP) are the polymerization product from at least a plurality of organic monomers. POPs are generally constructed from monomer units that are multitopic (three or more connection points). While the degree of cross-linking in a microporous polymeric material depends on the concentration of cross-linking molecules added, cross-linking in POPs is dictated by the valency / topicity of the monomer or co-monomer unit(s). Cross-links in POPs, formed between rigid building blocks, are also different from those in polymer gels, which are usually formed 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 from the reaction of: 1) catechol and aryl halides; 2) anhydride monomer and diamine monomer; and 3) carboxylic monomer and diamine monomer.

[0048] Covalent organic frameworks (COF) are a subset of POPs in that they are crystalline materials. Again, these materials and their synthesis are well known in the art.

[0049] Other suitable adsorbents include without limitation activated alumina and silica gel.

[0050] Binders suitable for use in the adsorbent hybrid granules include without limitation polymers such as polyvinyl pyrrolidone, available in a range of molecular weights; colloidal NUM024 silica such as those sold under the mark LUDOX®; colloidal zirconia; colloidal alumina; carboxymethylcellulose; and chitosan available in a range of molecular weights. Of these, polymers such as polyvinyl pyrrolidone and colloidal silicas are particularly suitable.

[0051] The adsorbent hybrid granules of the disclosure will be of an average size selected to facilitate ease of handling by a filter manufacturer, and to optimize performance in an intended application. Smaller granules can be more effective adsorbents, as the adsorbed contaminant has a shorter diffusion path through the adsorbent granule. But smaller granules can lead to a greater pressure drop as a gas passes through the adsorbent-containing filter. In one embodiment the adsorbent hybrid granules have an average diameter of 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. It is further preferred that the adsorbent particles have a particle size distribution sufficiently narrow to prevent the formation of channels in a bed or filter construction. In various embodiments, the adsorbent granules have an average size in the range of 600-1700 microns, or 400-800 microns, or 250-400 microns.

[0052] In each embodiment, the relative mass proportion of the first and second adsorbents will depend on the adsorbency and deactivation properties desired for the contaminants expected to be adsorbed. In various embodiments the mass proportion 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.

[0053] The hybrid adsorbent granules can contain other materials, including without limitation additional adsorbents, and binders. For those adsorbent hybrid granules that are in the form of a substantially random mixture of binder and adsorbent particles, the additional adsorbent materials can be randomly dispersed in the granules. For adsorbent hybrid granules that are 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.

[0054] In each embodiment of the adsorbent hybrid granules in which one of the adsorbents comprises a MOF material, the MOF is synthesized prior to preparation of the hybrid adsorbent granules. Since the MOF is not grown in situ on a substrate, or in the pores or on the surface of another adsorbent such as porous carbon or on a preexisting binder or other shell structure, there NUM024 can be greater choice in the selection of MOFs used, greater control of parameters in the MOF synthesis, and greater control of the MOF particle size. The fact that the MOFs are added to the hybrid adsorbent granules in the form of pre-made particles also allows for the use of more than one type of MOF in any of the embodiments disclosed herein. Further, if impregnated carbon or other impregnated material is used as one of the adsorbents, then any impregnated species will not interfere with MOF synthesis, nor will such species be degraded by the MOF synthesis process.

[0055] In the embodiments illustrated herein the adsorbents are activated carbon and a MOF material. It will be understood that these embodiments are selected for illustrative purposes only, and that other adsorbents can be selected as described above.

[0056] FIG.1 illustrates a first embodiment of an adsorbent hybrid granule 10 comprising a substantially random mixture of carbon particles 12, MOF particles14, and a binder 16. A process 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 vehicle to achieve carbon-MOF hybrid granules wherein at least some of the granules comprise a substantially random mixture of carbon particles, MOF particles, and binder; and drying the hybrid granules to remove the liquid vehicle. The dried granules can be sieved to a desired particle size range. The liquid vehicle used in the granulating process to facilitate granulation 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 granules can be activated at a desired temperature, for a desired duration, and optionally under reduced pressure to remove liquid vehicle that might be present and optimize adsorption properties. Optionally, more than one type of MOF can be used, and more than one type of carbon can be used, so that it is possible to optimize the adsorbency properties of the granules for particular contaminants to be adsorbed.

[0057] FIG.2 illustrates a second embodiment of an adsorbent hybrid granule 20 in the form of a core-shell structure comprising a core 22 comprising carbon and a shell 24 comprising a mixture of a binder 26 and particles of MOF 28. A process for preparing the second embodiment comprises the steps of providing a quantity of particles comprising carbon, providing a suspension comprising a binder and particles of MOF material, coating the particles comprising carbon with the suspension, and drying the coated particles to provide hybrid granules having a NUM024 core-shell structure comprising a core comprising carbon and a shell comprising a mixture of binder and particles comprising a MOF. Optionally the suspension can be sonicated prior to the coating step to break up any aggregates to improve uniformity of the suspension, then filtered to remove any remaining large MOF particles. Suitable coating processes include pan coating, spray coating, fluidized bed coating, and other methods that will be known to those skilled in the art. The coating process can be conducted at room temperature, or at temperatures up to 100ºC. The drying step can be conducted under vacuum, or at elevated temperature, or both. The drying conditions will be selected based on the liquid vehicle that must be removed. In one embodiment the granules are airdried overnight. Optionally the granules then can be activated at elevated temperature and / or under dynamic vacuum, as discussed below.

[0058] The liquid vehicle for the suspension can be any liquid that does not react with or dissolve the MOF particles, or any material impregnated in the carbon. Suitable liquid vehicles include water, methanol, chloroform, dichloromethane, and other common solvents. The liquids can be selected based on stability of the suspension, ease of drying, and stability of any impregnated material in the carbon core or MOF material. Water and methanol are particularly suitable liquid vehicles for the suspension.

[0059] The binder can be selected based on its compatibility with the liquid vehicle. Suitable binders include polyvinyl pyrrolidone available in various molecular weights, other known polymer adhesives such as polyvinyl acetate, and colloidal silicas such as those sold under the trade name Ludox®. Polyvinylpyrrolidone of molecular weight 360,000 is particularly suitable. Other suitable binders can include colloidal zirconia; colloidal alumina; carboxymethylcellulose; and chitosan available in a range of molecular weights. Other materials can be included in the suspension such as viscosity enhancers, foam inhibitors, pH control agents, and flow enhancement agents.

[0060] The size of the MOF particles in the coating suspension will be larger than the pores of the carbon but otherwise can vary depending on the coating technique used. If spray coating is used then the MOF particles generally will be of a size small enough so as not to clog the spraying nozzle. The size of the MOF particles of the coating 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 one micron, to about 0.5 micron. NUM024

[0061] A suspension for coating MOF particles onto carbon granules can comprise 10 -50 wt% MOF particles; up to 3 wt% binder based on the dry MOF, or up to 10 wt%, or up to 15 wt%, or up to 20 wt%; a total of up to 5 wt% based on the dry weight of the MOF of other optional materials such as viscosity enhancers, foam inhibitors, pH control agents, and flow enhancement agents; and the balance liquid vehicle.

[0062] FIG.3 illustrates a third embodiment of an adsorbent hybrid granule 30 in the form of a core-shell structure comprising a core 32 comprising a MOF material and a shell 34 comprising a mixture of a binder 36 and particles of carbon 38. A process for preparing the third embodiment comprises the steps of providing a quantity of particles comprising a MOF material, providing a suspension comprising a binder and particles comprising carbon, coating the particles comprising a MOF material with the suspension, and drying the coated particles to provide hybrid granules having a core-shell structure comprising a core comprising a MOF material and a shell comprising a mixture of binder and particles comprising carbon. Optionally the suspension can be sonicated prior to the coating step to break up any aggregates to improve uniformity of the suspension, then filtered to remove any remaining large carbon particles. Suitable coating processes include pan coating, spray coating, fluidized bed coating, and other methods that will be known to those skilled in the art. The coating process can be conducted at room temperature, or at temperatures up to 100ºC. The drying step can be conducted under vacuum, or at elevated temperature, or both. The drying conditions will be selected based on the liquid vehicle that must be removed. In one embodiment the granules are airdried overnight. Optionally the granules then can be activated at elevated temperature and / or under dynamic vacuum, as discussed below.

[0063] The size of the carbon particles in the coating suspension can vary depending on the coating technique used. If spray coating is used then the carbon particles generally will be of a size small enough so as not to clog the spraying nozzle. The size of the carbon particles of the coating 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, to about 0.5 micron.

[0064] A suspension for coating carbon particles onto cores comprising MOF materials can comprise 10 - 50 wt% carbon particles; up to 3wt% binder based on the dry weight of activated NUM024 carbon, or up to 10 wt%, or up to 15 wt%, or up to 20 wt% carbon; a total of up to 5 wt% based on the dry weight of the carbon of other optional materials such as viscosity enhancers, foam inhibitors, pH control agents, and flow enhancement agents; and the balance liquid vehicle.

[0065] Regardless of the method of manufacture, the adsorbent hybrid granules as disclosed herein can be activated by heating, typically under reduced pressure, to remove solvent from the dried granules. “Activated” as used herein with respect to adsorbent hybrid granules means that the adsorbent hybrid granules adsorb more of a contaminant than the as synthesized adsorbent hybrid granules. For example, the activated adsorbent hybrid granules 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 adsorbent hybrid granules can adsorb 2, 3, 5, 10, 15, 20, 30, 50, or 100 times the amount of contaminant versus the as synthesized adsorbent granules.

[0066] The adsorbent hybrid granules as disclosed herein are characterized in that they can adsorb various molecules. They, therefore, can be used to purify gas streams by at least partially adsorbing at least one contaminant in the gas stream. Gas streams which may need to be purified include but are not limited to air streams, industrial gas streams, off-gassing streams, or pollutant gas streams. Contaminants to be adsorbed include without limitation toxic industrial chemicals and CBRN contaminants. In some embodiments adsorbents can be selected so that the adsorbent hybrid granules 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 phosphonous dichloride, fluorine, hydrogen bromide, hydrogen chloride, hydrogen fluoride, hydrogen iodide, phosphorus trichloride, silicon tetrafluoride, sulfur trioxide, sulfuric acid, sulfuryl chloride, titanium tetrachloride, tungsten hexafluoride, bromine pentafluoride, hydrogen selenide, nitric acid, nitrogen dioxide, nitrogen tetraoxide, nitrogen trioxide and mixtures of any two or more of the foregoing. The amount of contaminant which the adsorbent granules can remove is at least 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. NUM024

[0067] Also provided herein is an apparatus comprising the adsorbent hybrid granules. In one embodiment of such an apparatus a vessel having an inlet and an outlet is filled with the hybrid adsorbent granules through which the gas stream is flowed thereby substantially removing one or more contaminants from the stream. In order to achieve the desired removal amount, the gas stream is flowed through the adsorbent granules at a rate of about 10 L / min to about 500 L / min or a rate from about 30 L / min to about 200 L / min or a rate of about 50 L / min to about 120 L / min.

[0068] In one embodiment an apparatus comprising the hybrid granular adsorbent can be a respirator such as for use in personal protective equipment and having a filter comprising the adsorbent hybrid granules. In one filter embodiment, the granules can be adhered to a substrate to form a layer of a filter structure. In another filter embodiment the adsorbent can be loaded into a cartridge that is removably fitted in a respirator construction. In either case, the fact that multiple adsorbent functionalities are provided in a single granular adsorbent product as disclosed herein will simplify the manufacturing process of the filter structure or respirator cartridge of the apparatus. EXAMPLES Example 1 - Zr-BDC-NH2 (UiO-66-NH2) MOF particles coated on impregnated activated carbon

[0069] A mixture of 20 g of Zr-BDC-NH2MOF (30 wt% H2O solvation) in 100 ml water is sonicated to disperse the MOFs into a homogeneous suspension.0.42 g of PVP binder is added to the suspension and dissolved. The suspension is filtered through a 53 µm sieve to remove large particles, then loaded into an aerosol-based spray system. A pan-coater is loaded with 80g impregnated activated carbon granules (Calgon Carbon Corporation) of size 12x30 mesh that had been pre-activated at 200°C for 16 hours. While the pan coater tumbles the carbon granules, the MOF suspension is sprayed onto the carbon granules until the flowability of the carbon bed is significantly reduced. Heated air is applied onto the coated granules to evaporate the solvent and restore the flowability. During the drying process the granule bed is stirred with a stainless-steel spatula. When the flowability of the granule bed is restored, the spray coating and drying process is repeated until the desired amount of MOF is coated onto the carbon cores. Nitrogen isotherms demonstrate that the MOF coating does not diminish the nitrogen uptake of the carbon in the hybrid adsorbent granules. Ammonia isotherms demonstrate that the MOF coating provides NUM024 ammonia adsorptive capacity to the hybrid adsorbent granules. The molecular weight of the binder can be selected to reduce dustiness of the dried hybrid adsorbent granules. Example 2 – Activation of hybrid adsorbent granules

[0070] Hybrid adsorbent granules of impregnated activated carbon and Zr-BDC-NH2 MOF are prepared following the general procedure of Example 1 but with different weight proportions of MOF to carbon, then sieved to between 12 and 30 mesh, and activated at 100ºC for about 18 hours, or until the pressure in the activation chamber was less than 0.1 torr. Nitrogen and ammonia isotherms demonstrate that N2and NH3uptake increase as the MOF loading increases. Theoretical calculated isotherms agree well with the weighted average of pure MOF and carbon components at different loadings. Example 3 - Carbon granules coated with impregnated MOFs

[0071] Samples of coated granules are prepared using the procedure of Example 1, except that ZnCl2 is included in the MOF suspension mixture, at a mass ratio of Zn:Zr of 0.1:1 to provide a coating of a Zn-impregnated Zr OF on the carbon granules. The MOF loading on the granules is 25 wt%. It is found that impregnation of the MOF of the coating with zinc does not significantly reduce N2 uptake, while NH3 uptake is improved. Example 4 – Blend of MOF particles and carbon particles

[0072] Adsorbent hybrid granules are prepared comprising a mixture of activated charcoal particles and MOF particles. The powders of MOF, activated charcoal and binder are mixed in a granulator. As the solid mixture is milled in the granulator, water as a liquid vehicle is added slowly to facilitate the formation of granular particles of MOF and activated charcoal. Blends are prepared of charcoal powder having a particle size in the range of 150 micrometers, Zr-BTC- NH2MOF powder prepared as in Example 1 and having particle size in the range of 3-5 micrometers, and 5% PVP binder. Ammonia isotherms demonstrate that the hybrid adsorbent granules provide good ammonia adsorbency. NUM024

[0073] Although the hybrid adsorbent granules, their method of manufacture, and filter and method of use have been described in detail in connection with the above description and examples, it is to be understood that such detail is solely for that purpose and that variations can be made by those skilled in the art without departing from the spirit of the disclosure except as it may be limited by the following claims.

Claims

NUM024 What is claimed is:

1. A composition comprising adsorbent hybrid granules, wherein said granules comprise a first adsorbent material, a second adsorbent material, and a binder mixed with either 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.

2. The composition of claim 1 wherein said granules comprise a substantially random mixture of particles of said first adsorbent material, particles of said second adsorbent material, and a binder.

3. The composition of claim 1 wherein said granules are in the form of core-shell structures comprising a core comprising at least one particle of the first adsorbent material and a shell comprising a substantially random mixture of a binder and particles of the second adsorbent material.

4. The composition of claim 1 wherein said first and second adsorbents 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 of claim 4 wherein said first and second adsorbents are selected from a carbonaceous adsorbent and a MOF material.

6. The composition of claim 5 wherein said carbonaceous adsorbent comprises activated carbon.

7. The composition of claim 6 wherein the activated carbon is impregnated activated carbon.

8. The composition of claim 5 wherein the hybrid adsorbent granules further comprise a second type of MOF.NUM024 9. he composition of claim 5 wherein the MOF material comprises a metal ion selected from the group consisting 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+, Fe2+, 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.

10. The composition of claim 5 wherein the MOF material comprises at least one organic ligand selected from the group consisting of 1,3,5-benzene tricarboxylic acid (BTC), triazine tris-benzoic acid (TATB), 2-amino-terephthalic acid, naphthalene dicarboxylate (NDC), acetylene dicarboxylate (ADC), benzene-1,4- dicarboxylic acid (BDC), benzene tribenzoate (BTB), methane tetrabenzoate (MTB), adamantane tetracarboxylate (ATC), adamantane tribenzoate (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 of claim 5 wherein the MOF material compromises one or more MOFs selected from the group consisting of MOF-808, UiO-66, UiO-66-NH2, and PCN-250.

12. The composition of claim 5 wherein the MOF material is impregnated with a metal compound.

13. An apparatus comprising the composition of claim 1.

14. A filter comprising the composition of claim 1.

15. The apparatus of claim 13 wherein the apparatus is a respirator.

16. A process for preparing adsorbent hybrid granules comprising the steps of 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 vehicle to achieve hybrid granules wherein at least some of the granules comprise a substantially random mixture of particles of said first adsorbent material, particles of said second adsorbent material, and binder; and drying the hybrid granules.NUM024 17. A process for preparing adsorbent hybrid granules comprising the steps of providing a quantity of particles comprising a first adsorbent material, providing a suspension comprising a binder and particles of a second adsorbent material in a liquid vehicle, coating the particles comprising the first adsorbent material with the suspension, and drying the coated particles.

18. The process of claim 17 wherein said first adsorbent material comprises a carbonaceous adsorbent and said second adsorbent material comprises a MOF material.

19. The process of claim 17 wherein said first adsorbent material comprises a MOF material and said second adsorbent material comprises a carbonaceous adsorbent.

20. A process for purifying a gaseous stream, the process comprising passing the gaseous stream through a composition of claim 1.

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