MULTI PURPOSE COMPOSITE GAS FILTER

Abstract

A filter for removing multiple target molecules from a gas stream, including a three-dimensional porous support permeable to the gas stream and a first plurality of active particles for removing a first undesired molecule and a second plurality of active particles for removing a second undesired molecule, wherein the first plurality of active particles are different from the second plurality of active particle, and wherein the first and second plurality of active particles are immobilized in or by the solid support. Also, a composite filter for removing components from an airstream by trapping or conversion using a composite filter containing multiple distinct active regions with varying chemical properties with different chemical composition within the same filter.

Claims

1-25. (canceled)

26. A composite filter for removing multiple target molecules from a gas stream, comprising a three-dimensional porous support permeable to the gas stream and a first plurality of active particles for removing a first target molecule and a second plurality of active particles for removing a second target molecule, wherein the first plurality of active particles are different from the second plurality of active particle, wherein the first and second plurality of active particles are immobilized in or by the support and wherein the first and second plurality of active particles are each independently selected from the group consisting of activated carbon particles, activated carbon particles pre-treated/impregnated with a metal, activated carbon particles pre-treated/impregnated with an enzyme, activated carbon particles pre-treated/impregnated with a basic compound, activated carbon particles pre-treated/impregnated with an acidic compound, metal organic framework (MOF) particle, catalyst particle, doped metal oxide particle, 1 wt % Pt/TiO.sub.2 particle, 0.1 wt % Pt/Fe.sub.2O.sub.3 particle, 3 wt % Pt/MnOx-CeO.sub.2 particle, and photocatalytic particles.

27. The composite filter of claim 26, wherein the first plurality of active particles is selected from a doped metal oxide particle and the second plurality of active particles is selected from an impregnated activated charcoal particle.

28. The composite filter of claim 27, wherein the doped metal oxide particle is doped to provide chemical properties targeting a certain segment of pollution on modified graphene.

29. The composite filter of claim 26, wherein the first plurality of active particles is selected from a metal organic framework particle.

30. The composite filter of claim 27, wherein the second plurality of active particles is selected from a metal organic framework particle.

31. The composite filter of claim 26, wherein the first and/or second plurality of active particles are doped to provide chemical properties targeting a certain segment of pollution.

32. The composite filter of claim 26, wherein the porous support comprises a third plurality of active particles for removing a third target molecule, wherein the third plurality of active particles are different from the first and second plurality of active particle, and wherein the third plurality of active particles are immobilized in or by the solid support.

33. The composite filter of claim 26, wherein the porous support body comprises a further plurality of active particles for removing a further target molecule, wherein the further plurality of active particles is different from the first, second and third plurality of active particles, and wherein the further plurality of active particles is immobilized in or by the solid support.

34. The composite filter of claim 32, wherein the first, second, third and optionally further plurality of active particles are each independently selected from the group consisting of activated carbon particles, activated carbon particles pre-treated/impregnated with a metal, activated carbon particles pre-treated/impregnated with an enzyme, activated carbon particles pre-treated/impregnated with a basic compound, activated carbon particles pre-treated/impregnated with an acidic compound, metal organic framework (MOF) particle, catalyst particle, doped metal oxide particle, 1 wt % Pt/TiO.sub.2 particle, 0.1 wt % Pt/Fe.sub.2O.sub.3 particle, 3 wt % Pt/MnOx-CeO.sub.2 particle, and photocatalytic particles; provided that the first, second, optionally third and optionally further plurality of active particles are selected from different active particles.

35. The composite filter of claim 26, wherein the three-dimensional porous support is selected from the group consisting of (i) a foam support body having a reticulated pore structure (ii) a felt of chemical- or bio-polymer fibers, (iii) twisted fiber thread, (iv) a flexible knitted fabric, (v) a bundle of mesh, (vi) a pile of strings, (vii) a pleated paper substrate, (viii) an air permeable three-dimensional rigid framework (e.g. metal wires or monofilaments), (viii) a brush like filter, and (ix) a material designed to give minimum flow resistance and maximum accessibility of the reaction surface to the gas stream.

36. The composite filter of claim 26, wherein the pore size 25 or more precise from 5 to 20 PPI.

37. The composite filter of claim 26, wherein the first, second, optionally third and optionally further plurality of active particles have a total surface area of from 100 to 7000 m.sup.2/g.

38. The composite filter of claim 37, wherein the first, second, optionally third and optionally further plurality of active particles have a total surface area from 800 to 2000 m.sup.2/g.

39. The composite filter of claim 26, wherein the first, second, optionally third and optionally further plurality of active particles are fixed to the pore structure of the support by an adhesive forming an adhesive layer.

40. The composite filter of claim 26, wherein the first or second plurality of active particles is selected from activated carbon particles.

41. The composite filter of claim 26, wherein the first, second, optionally third and optionally further plurality of active particles having an average particle diameter in the range from 0.005 to 3.0 mm.

42. The composite filter of claim 26, wherein the first, second, optionally third and optionally further plurality of active particles are independently selected from activated carbon particles pretreated with lithium permanganate, calcium acetate, copper dioxide, potassium hydroxide, potassium permanganate, manganese dioxide, copper nitrate, manganese acetate, potassium carbonate, or sodium permanganate.

43. The composite filter of claim 26, wherein the foam is a polyurethane based foam.

44. The composite filter of claim 26, wherein the adhesive layer has a thickness obtainable by coating the foam at least two times with the adhesive.

45. The composite filter of claim 26, wherein the adhesive is selected from a hot-melt adhesive, or an adhesive based on polystyrene, urethane, liquid resin, polyurethane, and/or styrene.

Description

[0082] These drawings are by no means limiting the scope of the present invention and are only intended to guide the skilled person for better understanding of the present invention.

[0083] FIG. 1 illustrates a foam support body (10) having a reticulated pore structure composite filter with different pluralities of active particles. A small section of the filter body (10) is magnified (19) and the different active particles are illustrated (11, 12, 13, 14, 15, 16). For instance, the first active particle (11) may be a catalytic bead or more specifically a gold nanoclusters on cerium(IV)oxide catalyst particle. The second active particle (12) maybe an activated carbon bead, more specifically an activated carbon particle impregnated with potassium permanganate. The third active particle (13) maybe a basic/alkaline activated carbon bead, more specifically an activated carbon particle impregnated with potassium hydroxide. The fourth active particle (14) maybe an acid activated carbon particle, more specifically an activated carbon particle impregnated with nitric acid. The fifth active particle (15) maybe an active MOF particle, more specific a HKUST-1 particle. The sixth active particle (16) maybe an activated carbon particle, more specifically an activated carbon particle without impregnation to keep the surface area as high as possible. The foam wall (18) constitutes the porous structure with empty space (17) between the foam walls. The active particles may be glued on the surface of the pores.

[0084] FIG. 2 illustrates a felt of polymer fibers filter (20) with different active particles (24-29). A small section of the filter (20) is magnified (30) and the different active particles are illustrated (24-29). The different active particles may be selected from the same as in FIG. 1, so that active particle (11-16) corresponds to (24-29), respectively. The felt consists of fibers (21) and empty spaces (22). The active particles may be glued on the surface of the fibers.

[0085] FIG. 3 illustrates a spun yarn or twisted fiber thread filter (40) with different active particles (43-48). A small section of the filter (40) is magnified (42) and the different active particles are illustrated (43-48). The different active particles may be selected from the same as in FIG. 1, so that active particle (11-16) corresponds to (43-48), respectively. The thread (40) is composed of fibers (49) which are spun as shown. The active particles may be glued on the surface of the threads.

[0086] FIG. 4 illustrates a flexible knitted fabric filter (50) with different active particles (53-58). A small section of the filter (50) is magnified (51) and the different active particles are illustrated (53-58). The different active particles may be selected from the same as in FIG. 1, so that active particle (11-16) corresponds to (53-58), respectively. The knitted fabric (50) consists of fibers (51) and empty spaces (52). The active particles may be glued on the surface of the fabric.

[0087] FIG. 5 illustrates a Sponge or bundle of mesh filter (79) with different active particles (73-78). A small section of the filter (79) is magnified (70) and the different active particles are illustrated (73-78). The different active particles may be selected from the same as in FIG. 1, so that active particle (11-16) corresponds to (73-78), respectively. The mesh filter (79) consists of fibers (71) and empty spaces (72) in the mesh. The active particles may be glued on the surface of the fibers.

[0088] FIG. 6 illustrates a pile of strings or a bundle made of one string filter (120) with different active particles (123-128). A small section of the filter (120) is a magnified view of the strings (122) and the different active particles are illustrated (123-128). The different active particles may be selected from the same as in FIG. 1, so that active particle (11-16) corresponds to (123-128), respectively. The string filter (120) consists of multiple strings (129) that are made into a bundle. The active particles may be glued on the surface of the strings.

[0089] FIG. 7 illustrates a pleated paper or non-woven substrate filter (90) with different active particles (93-98). A small section of the filter (90) is a magnified view of the strings (92) and the different active particles are illustrated (93-98). The different active particles may be selected from the same as in FIG. 1, so that active particle (11-16) corresponds to (93-98), respectively. The substrate filter (90) consists of a filter substrate (99) which have been pleated. The active particles may be glued on the surface of the pleated paper.

[0090] FIG. 8 illustrates a three-dimensional rigid framework filter (100) with different active particles (103-108). A small section of the filter (100) is a magnified view of the three-dimensional rigid framework (102) and the different active particles are illustrated (103-108). The different active particles may be selected from the same as in FIG. 1, so that active particle (11-16) corresponds to (103-108), respectively. The framework filter (100) consists of a rigid frame (109). The active particles may be glued on the framework.

[0091] FIG. 9 illustrates a feather or brush like filter (130) with active particles on the brush threads (132). A small section of the filter (130) is a magnified view of the brush threads (139) and the different active particles are illustrated (133-138). The different active particles may be selected from the same as in FIG. 1, so that active particle (11-16) corresponds to (133-138), respectively. The brush like filter (130) consists of multiple brush threads (132) to which the active particles may be glued.

[0092] All references, including publications, patent applications and patents, cited herein are hereby incorporated by reference to the same extent as if each reference was individually and specifically indicated to be incorporated by reference and was set forth in its entirety herein.

[0093] All headings and sub-headings are used herein for convenience only and should not be construed as limiting the invention in any way.

[0094] Any combination of the above-described elements in all possible variations thereof is encompassed by the invention unless otherwise indicated herein or otherwise clearly contradicted by context.

[0095] Recitation of ranges of values herein are merely intended to serve as a short method of referring individually to each separate value falling within the range, unless other-wise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. Unless otherwise stated, all exact values provided herein are representative of corresponding approximate values (e.g., all exact exemplary values provided with respect to a particular factor or measurement can be considered to also provide a corresponding approximate measurement, modified by “about”, where appropriate).

[0096] All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context.

[0097] The terms “a” and “an” and “the” and similar referents as used in the context of describing the invention are to be construed to insert both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. Thus, “a” and “an” and “the” may mean at least one, or one or more.

[0098] The term “and/or” as used herein means each individual alternative as well as the combined alternatives, for instance, “a first and/or second barrier” is intended to mean one barrier alone, the other barrier alone, or both the first and the second barrier at the same time.

[0099] The use of any and all examples, or exemplary language (e.g., “such as”) provided herein, is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention unless otherwise indicated. No language in the specification should be construed as indicating any element is essential to the practice of the invention unless as much is explicitly stated.

[0100] Throughout the description when “selected from” or “selected from the group consisting of” is used it also means all possible combinations of the stated terms, as well as each individual term.

[0101] The citation and incorporation of patent documents herein is done for convenience only and does not reflect any view of the validity, patentability and/or enforceability of such patent documents.

[0102] The description herein of any aspect or embodiment of the invention using terms such as “comprising”, “having”, “including” or “containing” with reference to an element or elements is intended to provide support for a similar aspect or embodiment of the invention that “consists of”, “consists essentially of”, or “substantially comprises” that particular element or elements, unless otherwise stated or clearly contradicted by context (e.g., a composition described herein as comprising a particular element should be understood as also describing a composition consisting of that element, unless otherwise stated or clearly contradicted by context).

[0103] This invention includes all modifications and equivalents of the subject matter recited in the aspects or claims presented herein to the maximum extent permitted by applicable law.

[0104] The features disclosed in the foregoing description may, both separately and in any combination thereof, be material for realizing the invention in diverse forms thereof.

EXPERIMENTS

Example: A Composite Filter that Targets Specific Pollution Compositions

[0105] Broadly defined the active particles can be attached to the substrate either physically or chemically. A physical attachment could be to trap the active particles in between two thin layers of felt or papers or within a compact pile of strings or when a fiber thread is twisted or heat sealed in small pockets in between two nylon meshes or heat sealed in small pockets in between a nylon mesh and a particle composite filter. One chemical attachment could be affected by adding an adhesive layer that attach the active particles to the surface of the substrate.

[0106] More specifically, a foam based composite filter as shown in FIG. 1 could be prepared in a similar way as described by Oehler et al., in U.S. Pat. No. 5,820,927 or through the following description. The foam substrate is coated with a glue layer that ensures a firm attachment of the active particles. The adhesive glue layer could preferable be made from a hot-melt adhesive, but polystyrene, ABS, styrene or other adhesives would also work.

[0107] The synthesis of the composite filter includes steps of expanding the foam using a suitable solvent such as dichloromethane (DCM) and coating the substrate with glue, for example by dissolving hot-melt adhesive sticks in the DCM. The solvent could be prepared with 50 grams of ethylene vinyl acetate based adhesive, such as a 3M #3792 holt-melt glue stick, dissolved in 1 L of DCM. The solvent should be kept in a closed glass bottle with a lid, while stirred and heated until the glue sticks are dissolved. The solvent temperature should not exceed 35° C. The solvent causes the foam to expand by for example a factor of two.

[0108] The foam is then placed in the solvent and allowed to expand. The foam expansion increases the pore size in the foam which increases the foam surface area and hereby increasing the activated carbon particle coverage. After about 10 seconds, the foam is removed and shaken to prevent any pores from being blocked with glue. The foam shrinks after soaking in solvent. This acts to give the optimum binding between the substrate and activated carbon particles. The foam is then placed on a metal rack and dried. The optimal glue layer thickness is obtained when the foam is coated multiple times 2-10 times, optimally 5 times. When the substrate is placed in the solvent it is important that the foam only stays in the solvent long enough for the whole foam to come in contact with the solvent but not so long that the solvent dissolves the already established glue layer. After the final coating the foam is placed on a metal rack and carbon particles are poured over the “wet” foam. The foam is then flipped, and the carbon particles are poured on the other side.

[0109] The working time to introduce the carbon is around ½−1 min. The activated carbon particles can either be activated carbon spheres, activated carbon beads, activated granular carbon particles or a mixture hereof. The activated carbon particles have a high surface area of around 1000-1700 m.sup.2/g dominated by pores smaller than 1 nm. The foam is now denoted composite filter.

[0110] The composite filter is dried for 20-30 min while sitting on a vibrating table that ensures maximum packing and removes any excess carbon particle stuck in the composite filter. The vibrating table vibrates at a frequency of 400 Hz with a power of 60 W. Once the carbon particles are stuck to the surface the composite filter is put into an oven for 10 to 25 min, optimally 15 min at temperatures of 115-135° C., optimally at 123° C. The viscosity of the glue layer is lowered at this temperature allowing the carbon particles to penetrate into the glue layer. The right temperature is very important as too high temperatures make the glue layer too viscous and decomposes the substrate, while too low temperatures keeps the glue layer too hard for the activated carbon particles to penetrate correctly. Right after heating, the composite filter is placed on the vibrating table for 10 min or until the composite filter is cold. The reduced viscosity of the glue combined with the vibrations from the table makes the carbon particles bond more tightly with the glue layer allowing the glue to infiltrate the surface pores of the activated carbon particles and thereby trapping the activated carbon particles firmly to the substrate.

[0111] The flexible knitted fabric, the bundle of meshes, the air permeable three-dimensional rigid framework (e.g. metal wires or monofilaments) and the brush like composite filter can all be used as a support structure for the composite filter media in a similar way as described for the foam support.

[0112] To target formaldehyde the active particle could be a catalyst (like doped gold nanoclusters 1 wt % on a Cerium (IV) oxide (CeO.sub.2) particle, 1 wt % Pt/TiO.sub.2 particle, 0.1 wt % Pt/Fe.sub.2O.sub.3 particle, 3 wt % Pt/MnOx-CeO.sub.2 particle) or an acid activated carbon particle with impregnation such as potassium permanganate, 4-aminobenzoic acid (PABA), or hexamethylene diamine (HMDA), a photocatalyst particle like titanium dioxide (TiO.sub.2) or a metal organic framework particle like Aluminium Fumarate, HKUST-1 (copper benzene-1,3,5-tricarboxylate), FeBTC (iron 1,3,5-benzenetricarboxylate), ZIF-8 (2-methylimidazole zinc salt) or Ni-MOF-74 is needed. To target NOx the active particle could be a potassium containing alkaline activated carbon particle with an impregnation such as potassium nitrate (KNO.sub.3), potassium hydroxide (KOH), potassium carbonate (K.sub.2CO.sub.3) or potassium sulfate (K.sub.2SO.sub.4). To target VOCs the active particle could be an activated carbon particle that has a high available surface area/capacity to adsorb a high number of molecules, this could be an activated carbon particle without impregnation. To target acidic gases like hydrogen sulfide, sulfur dioxide, nitric acid, sulfuric acid, nitrous acid, hydrochloric acid, formic acid, acetic acid a basic treated active particle is need. Whereas basic gases like ammonia, amines, proton acceptors/electron donors will be more effective removed by an acidic particle. The active particle that targets sulfur dioxide and hydrogen sulfide could be an activated carbon particle with a basic impregnation such as potassium hydroxide (KOH) or sodium hydroxide (NaOH) or another similar base. To target ammonia the active particle could be an activated carbon particle modified to have a large amount of oxygen surface groups like Brønsted acid (like carboxylic acid groups) or Lewis acid sites on the surface layer. This active particle could be an acid impregnated activated carbon particle like a nitric acid (HNO.sub.3) treated, sulfuric acid (H.sub.2SO.sub.4) treated or similar acid treated activated carbon particle.

[0113] To remove a high concentration of formaldehyde, NOx and VOCs a composite filter needs at least three different active particles. [0114] 1) One composite filter example that targets the removal of formaldehyde, NOx and VOCs could have a ratio between the three different active particles as follows: 1-35 wt % gold nanoclusters on cerium(IV)oxide, 40-95 wt % potassium hydroxide (alkaline/basic) impregnated activated carbon and 1-30 wt % activated carbon particles. [0115] 2) Another composite filter example that targets the same air pollution could have a ratio between the three active particles as follows: 1-30 wt % potassium permanganate impregnated activated carbon, 40-95 wt % potassium hydroxide (alkaline/basic) impregnated activated carbon and 1-30 wt % activated carbon particles.

[0116] All wt % are weight % of the active particle. Sulfur species like hydrogen sulfide and sulfur dioxide are very reactive towards metal centers and is therefore known to poison catalysts. One way to overcome this is to make a composite filter with a differentiated active particle ratio or one particle ratio on the first half and another on the other half or composite filter in which the fraction of a given particle type varies with depth from the front to the back faces of the composite filter. The upstream particle ratio could then have a large amount of an active particle that targets sulfur compounds. These would remove sulfur compounds and thereby protect the catalyst from being poisoned. The downstream side of the composite filter could then have an active particle concentration with an increased fraction of catalyst particles. [0117] 3) A composite filter example that would overcome the problem of catalyst poisoning could have the following ratios on the upstream side of the composite filter: 45-95 wt % potassium hydroxide (alkaline/basic) impregnated activated carbon, 5-40% acidic active particle and 5-30 wt % activated carbon particles. The downstream side of the composite filter could then have the following ratios: 5-60 wt % gold nanoclusters on cerium(IV)oxide, 20-60 wt % potassium hydroxide (alkaline/basic) impregnated activated carbon, 1-20 wt % acidic active particle and 1-20 wt % activated carbon particles.

[0118] Another composite filter example is a composite filter designed to remove ammonia. [0119] 4) A composite filter example which targets NOx, formaldehyde, VOCs and ammonia could have the following active particle ratios: 1-30 wt % gold nanoclusters on cerium(IV)oxide, 40-95 wt % potassium hydroxide (alkaline/basic) impregnated activated carbon, 1-30 wt % activated carbon and 1-15 wt % nitric acid or sulfuric acid impregnated activated carbon.