Patent Application
20160166970
The present invention relates to the technical field of sorptive, especially adsorptive materials and particularly to the technical field of sorptive, especially adsorptive filtering materials and filters, which may especially be used for the purpose of the purification of fluids, such as streams of gases and air or for the purpose of the detoxification (i.e. the removal) of noxiants and toxic substances, in particular for use in or as respiratory filtering materials (e.g. NBC protective mask filters or gas-mask filters).
In particular, the present invention refers to an adsorptive filter unit, especially for the purification of gases and/or gas mixtures, wherein the filter unit of the invention comprises a plurality of (i.e. at least two) filter elements being different from each other.
Furthermore, the present invention refers to a process for the purification of gases and/or gas mixtures, preferably air, and for the removal of chemical and/or biological substances or noxiants from gases and/or gas mixtures, respectively.
Moreover, the present invention relates to the use of the inventive adsorptive filter units for producing filters and filter materials of all types, in particular for the removal of pollutants, odorous substances and poisons.
Finally, the present invention relates to filters or filter materials as such, in particular for the removal of pollutants, odorous substances and poisons, the filters or filter materials being produced by using the adsorptive filter unit of the present invention and/or comprising the adsorptive filter unit of the present invention.
The adsorptive filter unit of the invention is useful not only for the military sector but also for the civil sector, more particularly for NBC (i.e. nuclear, biological and chemical) deployment, and/or for industrial applications, especially with respect to the purification of gases and/or gas mixtures, preferably air.
There exists a multitude of materials and substances, which are taken up or adsorbed by the skin and lead to serious physical harm. Examples include the vesicatory mustard gas (synonymously also referred to as yellow cross and Hd, respectively) and the nerve agent sarin.
A further class of substances being harmful to health is represented by the so-called TICs (Toxic Industrial Chemicals). Toxic industrial chemicals are industrial chemicals which cause chemical hazards, e.g. carcinogens, reproductive hazards, corrosives or agents that have a negative impact on lungs or blood, or physical hazards, e.g. flammable, combustible, explosive or reactive agents. In general, TICs are industrial chemicals that are manufactured, stored, transported and used throughout the world. Examples for TICs with high hazard index are ammonia, arsine, chlorine, ethylene oxide, formaldehyde, hydrogen sulfide, hydrocyanic acid and the like.
Therefore, people who are likely to come into contact with such poisons have to be protected against the hazardous effects of these poisons by suitable protective materials, especially regarding the purification of breathing air, e.g. by respiratory filtering materials, especially NBC protective mask filters.
Respiratory filtering materials and also industrial filters known for this purpose often include sorbents, especially in the form of activated carbon, for the purpose of adsorption and/or detoxification of the respective harmful substances as delineated above.
Owing to its quite unspecific adsorptive properties, activated carbon is the most widely used adsorbent. Activated carbon is generally obtained by carbonization (also known synonymously known as pyrolysis, burning etc.) and subsequent activation of carbon-containing starting compounds (e.g. organic resins etc.), with reference being given to starting compounds which lead to economically sensible yields, such as organic resins etc. (cf., for example, H. v. Kienle and E. Bäder, “Aktivkohle and ihre industrielle Anwendung” [“Activated Carbon and Its Industrial Applications”], Enke Verlag, Stuttgart, 1980).
In this context, activated carbon is often used in respective filter or filter materials, such as respiratory or NBC protective mask filters, especially in the form of a loose fill and/or a bulk, respectively. In this context, the sorbent is filled into a cartridge, which cartridge is e.g. adapted to a respiratory mask and allows for the passage of breathing air through the sorbent material.
Such respiratory or NBC protective mask filters are well known in the prior art. In this context, reference is made to EP 0 159 698 A2 and to the corresponding patent family members thereof, especially GB 2 157 970 A and JP 61011061 A, each referring to a filter canister for removing undesirable substances from a breathable gas, wherein the filter canister comprises a filter assembly including a sorbent on the basis of a bed of compressively loaded loose sorbent particles, wherein also carbon particles are used as the respective filter material.
However, the use of the aforenamed sorbents, such as e.g. activated carbon, especially in the form of a loose fill and/or a bulk, respectively, is generally linked to the decisive disadvantage that the respective filters exhibit a limited adsorption capacity and a limited adsorption capability, on the one hand, and a non-optimal behavior with respect to the flow of air through the filter as such, on the other hand.
Furthermore, usual sorbents such as activated carbon do not effectively adsorb all kinds of harmful substances or poisons (e.g. phosgen) in an efficient way.
As a consequence, as a serious drawback of prior art filters comprising a sorbent material, especially activated carbon, particularly in the form of a loose fill and/or a bulk, respectively, one has to conclude that the respective filters do not always exhibit the desired performance with respect to the adsorption capacities and breakthrough properties vis-à-vis the various substances to be adsorbed, especially resulting in decreased breakthrough times.
In order to reduce the respective disadvantages linked to prior art filters, an enlargement of the filter, especially on the basis of its volume or filtering distance, on the one hand, and an increase of the loading bulk density, especially by using smaller particles or more dense packagings, on the other hand, has been realized. These measurements lead to a certain improvement with respect to the adsorbing capacity as well as with respect to the breakthrough properties; however, the respective measurements for improving these breakthrough properties also lead to an increase in breathing resistance, which, however, represents a decisive drawback for the wearer of NBC protective masks comprising such filter elements. In particular, a significant increase in breathing resistance is not acceptable, especially not in situations of enlarged physical stress, which particularly occurs in combat situations or the like.
Moreover, in order to diminish the aforenamed disadvantages linked to the use of the adsorbent in the form of a loose fill or a bulk, respectively, the sorbent material, especially activated carbon, is often additized and/or provided with a catalytically active component, especially by impregnating the activated carbon for example with substances based on metals or metal compounds.
In general, such modified activated carbon exhibits a certain improvement with respect to the adsorption of specific harmful substances and agents, respectively, especially since the activated carbon modified with a catalytically active substance exhibits—in addition to its adsorption properties on the basis of physisorption—also chemisorptive properties due to the presence of the catalytically active substance and the impregnation, respectively.
Filtering materials comprising activated carbon impregnated with catalytically active metallic compounds are known in the art. In this context,
EP 0 405 404 A1 and the corresponding patent family members U.S. Pat. No. 5,063,196 A and JP 03114534 A, respectively, refer to an impregnated activated carbon for the adsorption of toxic gases and/or vapors, which activated carbon comprises an impregnation on the basis of copper and zinc and optionally also silver and/or triethylenediamine (TEDA). Furthermore, reference is made to EP 0 614 400 B1 and the corresponding patent family members WO 03/10896 A1 and U.S. Pat. No. 5,492,882 A, referring to an activated carbon impregnated with several compounds wherein the several compounds comprise sulfuric acid or sulfuric acid salts, molybdenum compounds, copper compounds and zinc compounds.
However, in general, the impregnation of the activated carbon may have an adverse impact on the performance of the activated carbon since the catalyst may diminish the adsorption properties. Moreover, the problem of poisonous or warfare agents breaking through, especially at low and/or residual concentrations in the air to be purified, cannot always be solved by this principle.
Thus, the adsorption properties even of impregnated activated carbon are not always sufficient, especially since a certain breakthrough of low concentrations of chemical noxiants may occur, which, however, may have a detrimental effect to a person affected by the respective noxiants, especially since already very low concentrations of harmful substances generally exhibit a high impact on health.
In particular, the adsorption kinetics as well as the adsorption spontaneity even of impregnated activated carbon are not always sufficient, which especially applies for the removal of low and/or residual concentrations of noxiants in an air and/or gas stream to be purified, thus resulting in decreased breakthrough properties and reduced lifetimes of the respective filters as such.
Consequently, as delineated above, the respective prior art filtering materials comprising activated carbon having a specific impregnation do not always fulfill the high requirements linked to the purification of air or gas streams which are contaminated with low and/or residual concentrations of harmful substances and noxiants, respectively.
To sum up, there is a great need for an effective removal also of very small concentrations of a very wide variety of pollutants and/or noxiants from the air, especially harmful or noxious substances, toxic substances and the like.
The present invention therefore has, for its first object, to provide a filter unit, wherein the above-described disadvantages of the prior art are to be at least substantially obviated or to be ameliorated, respectively. More particularly, such an adsorptive filter unit should be suitable for the use in or as respiratory filters, NBC protective mask filters or gas-mask filters and the like.
In particular, another object of the present invention is to provide an adsorptive filter unit which exhibits improved adsorption properties, especially with regard to improved adsorption kinetics and/or adsorption spontaneity, especially
accomplishing the task of adsorbing also low and/or residual concentrations of harmful substances and/or noxiants from air, thus improving the breakthrough behavior of the resulting filter.
Finally, another object of the present invention is to provide an adsorptive filter unit, which is in particular suitable for the use in or as respiratory filters or gas-mask filters for the removal of pollutants and poisons of all types, in particular from streams of air and/or gas and/or gas mixtures. In this context, the adsorptive filter unit shall ensure a good filtering efficiency when used in this way.
To achieve the abovementioned objects, the present invention proposes, according to a first aspect of the present invention, an adsorptive filter unit (i.e. a filter structure or filter media, respectively) as described herein. Further advantages and embodiments of the adsorptive filter unit of the invention are the subject-matter of the respective dependent claims.
The present invention further provides, according to a further aspect of the present invention, a process for the purification of gases and/or gas mixtures, preferably air, and/or for the removal of chemical and/or biological substances or noxiants, according to the methods described herein.
The present invention, according to another aspect of the present invention, refers also to the use of the inventive adsorptive filter unit for producing filters and filter materials of all types, as similarly described.
Finally, the present invention further provides, according to still another aspect of the present invention, filter or filter materials produced using an adsorptive filter unit of the invention and/or comprising the adsorptive filter unit of the invention.
It will be understood that features, embodiments, advantages and the like which are recited herein in relation to one aspect of the invention, of course, also apply correspondingly in relation to all other aspects of the invention.
Moreover, it is pointed out that the respective values and/or parameter indications can be determined in general on the basis of determination methods which are well-known to the skilled practitioner and/or which are explicitly indicated in the following.
Furthermore, it will be understood that a person skilled in the art may, for a particular application or on an one-off basis, depart from any hereinbelow recited numbers, values and ranges, without thereby leaving the scope of the present invention.
The present invention—in accordance with a first aspect of the present invention—accordingly provides an adsorptive filter unit (i.e. filter structure or filter media, respectively) (FU), especially for the purification of gases and/or gas mixtures, preferably air, and/or for the removal of chemical and/or biological substances or noxiants from gases and/or gas mixtures, preferably air, in particular for use in or as a respiratory filter or gas-mask filter,
wherein the filter unit (FU) comprises a plurality of, preferably at least two, filter elements (1, 2) which are different from each other,
The fundamental idea of the present invention thus has to be seen in providing an adsorptive filter unit on the basis of at least two different filter elements which are specifically arranged and/or positioned within the inventive filter unit with respect to the flow direction in the use-state of the filter unit as such. In this context, the respective filter elements differ from each other in so far as the first filter element especially comprises a very specific activated carbon impregnated with at least one reactive and/or catalytically active compound whereas the second filter element arranged downstream of the first filter element comprises a second adsorbent material selected from the group consisting of ion-exchange resins, activated carbon provided with an alkaline or an acidic component, zeolites and metal-organic framework materials (MOFs).
For, applicant has succeeded, in a completely surprising manner, in providing a very specific adsorptive filter unit which is provided with significantly improved adsorption properties, especially on the basis of an improved adsorption capacity, on the one hand, as well as on the basis of improved adsorption kinetics, especially adsorption spontaneity, with regard to poisonous and/or noxiant agents, on the other hand, allowing for the removal and/or detoxification even of very low concentrations of toxic substances over a prolonged period of time.
As a consequence, the inventive adsorptive filter unit exhibits improved overall breakthrough properties, thus making it highly appropriate for the use in or as filters, especially in gas-mask or respiratory filters for improved and long-time use. In this context, applicant has also succeeded in providing a filter unit which combines the diametrically opposed features of improved adsorption properties, on the one hand, and improved breathing resistance, on the other hand, within one and the same filter unit, especially since an undue enlargement of the filter volume as well as of the packaging density of the adsorbents to be used are not necessary with regard to the inventive concept.
Especially, the present invention provides for the first time a specific adsorptive filter unit on the basis of the purposeful combination and arrangement of specific filter elements, each having specific adsorption properties, wherein the inventive adsorptive filter unit as such is provided with a significantly increased adsorption efficiency.
In this context, without wishing to be bound to this specific theory, the presence of the first filter element especially on the basis of a specifically impregnated activated carbon and arranged upstream of the second filter element provides for outstanding adsorption and/or filtration properties with regard to a large spectrum of poisonous or noxiant agents and this also with regard to a large spectrum of TICs, whereas the second filter element which is purposefully arranged downstream of the first filter element and comprises a further specific adsorbent material, especially on the basis of metal-organic framework materials (MOFs) or other materials as mentioned before, exhibits purposefully optimized adsorption kinetics and adsorption spontaneity, respectively, especially with regard to more specific poisonous and/or noxiant agents being present in low and/or residual concentrations after the passage through the first filter element.
Consequently, according to the general concept of the present invention, the first filter element in general exhibits an improved adsorption capacity with respect to a wide spectrum of poisonous and/or noxiant agents, especially also TICs, whereas the second filter element is specifically optimized with respect to the adsorption of residual poisonous and/or noxiant agents, especially in very low and/or residual concentrations in the fluid, especially air, to be purified, wherein it is also possible to purposefully optimize the second filter element with respect to the adsorption of specific poisonous and/or noxiant agents and/or specific TICs.
In general, the second filter element exhibits a high capacity (especially also as a result of the small remaining amounts of toxic agents to be adsorbed) as well as a rapid filtration and/or adsorption kinetic also with respect to low and/or residual concentration of noxiants, especially TICs. Consequently, also low and/or residual concentrations of the substances to be adsorbed are effectively removed on behalf of the second filter element being purposefully arranged and/or positioned downstream of the first filter element, wherein the first and second filter elements complement each other to provide for the improved properties of the inventive filter element.
According to the inventive concept, in general, the first filter element of the inventive adsorptive filter unit exhibits an adsorption characteristic providing for a high adsorption capacity with a very slow increase of the breakthrough of the respective noxiants. Consequently, the second filter element of the inventive adsorptive filter unit is exposed only to relative low and/or residual concentrations of the respective noxiants to be adsorbed—which, however, may have an harmful impact on health—, the latter being effectively adsorbed by the second filter element due to the purposeful optimization of its adsorption properties with regard to the elimination of residual noxiants being present only in low concentrations in the fluid to be purified.
Thus, on the whole, a very effective adsorptive filter unit as such is provided on the basis of the inventive concept, having improved overall adsorption properties with a prolonged lifetime in the use state as a result of improved breakthrough characteristics due to excellent adsorption capacities and adsorption kinetics.
On the whole, due its specific properties, the use of the inventive adsorptive filter unit is not limited to the military sector, especially with regard to NBC protective mask filters or the like. Rather, the inventive adsorptive filter unit is also appropriate for industrial applications like industrial filters, especially filters for purification of the air in a room or the like as well as in the medical sector, especially due to its outstanding properties also with respect to the adsorption of TICs.
Furthermore, the purposefully optimized filter elements of the inventive filter unit as such surprisingly complement each other synergistically, especially also due to their specific arrangement within the inventive filter unit, with regard to the protective performance against poisonous and/or noxiant agents to be adsorbed from a stream of air or the like and thus beyond the sum total of the individual effects. As delineated hereinafter, the synergistic effect surprisingly found by the applicant is well proved by the operative examples given below.
The present invention thus succeeds altogether in significantly increasing the adsorption performance of the inventive adsorptive filter unit on the basis of two active filter elements and/or filter layers, respectively, with regard to poisonous and/or noxiant agents, such as warfare agents, resulting in an adsorptive filter unit which exhibits improved breakthrough properties and lifetimes, especially with regard to its use in or as gas-mask filters and the like.
Altogether, the conception of the inventive adsorptive filter unit is associated with a multiplicity of advantages, of which the aforementioned advantages are only mentioned by way of example.
The term “downstream” as used according to the claimed invention, especially refers to a relative arrangement and/or positioning of the second filter element with respect to the first filter element, wherein the arrangement of the second filter element is performed in so far as the second filter element is positioned in the use-state of the inventive filter unit after the first filter element with respect to the flow direction of the gas, gas mixture and/or air to be purified. Accordingly, the term “upstream” refers to an arrangement according to which a filter element, especially the first filter element of the inventive adsorptive filter unit, is positioned in the use-state of the filter unit previous to and/or in front of the second filter element with respect to the flow direction of the gas, gas mixture and/or air to be purified.
As delineated above, due to the specific arrangement of the respective filter elements within the inventive adsorptive filter unit, according to which the second filter element is arranged downstream of the first filter element, a surprising improvement of adsorption properties has been achieved with respect to the inventive adsorptive filter unit, thereby also providing low breathing resistances.
With respect to the first filter element of the inventive adsorptive filter unit, especially the first adsorbent material, it is also pointed out that the purposeful provision, especially impregnation, of the activated carbon with at least one reactive and/or catalytically active component results in a catalytic activity of the activated carbon. Consequently, the first adsorbent material on the basis of activated carbon preferably exhibits chemisorptive properties in addition to the physisorptive properties of the adsorbent material as such. In general, the reactive and/or catalytically active component comprises a substance, which leads to the respective poisons and/or noxiants being rendered harmless. Thus, the catalytically active component may comprise a catalyst which induces the degradation of poisonous and/or noxiant agents impinging on the adsorptive filtering unit, wherein the catalyst as such may emerge at least essentially unchanged from the degradation reaction and wherein non-toxic degradation products result. On the basis of this principle, the adsorption capacity of the first filter element is increased, especially with respect to a wide spectrum of poisonous and/or noxiant agents and especially with respect to a wide spectrum of TICs. Especially due to the catalytic activity, the first filter element maintains its adsorption function with regard to poisonous and/or noxiant agents even when exposed to large concentrations of the agents to be adsorbent over a long period of time, wherein remaining low and/or residual concentrations of the poisonous and/or noxiant agents which are not adsorbed by the first filter element are then rendered harmless and/or removed due to adsorption by the second filter element arranged downstream of the first filter element.
As delineated above, the first adsorbent material comprised by the first filter element may principally be selected from (i) granular, especially spherical, activated carbon particles, which activated carbon particles are provided, especially impregnated, with at least one reactive and/or catalytically active component based on a metal or a metal compound selected from the group consisting of copper, silver, cadmium, platinum, palladium, rhodium, zinc, mercury, titanium, zirconium, vanadium and/or aluminum and their ions, compounds and/or salts and combinations thereof and, optionally, also with an alkaline or acidic component, and/or (ii) zeolites, especially acidic zeolites (such as e.g. ZSM-5 and ZSM-11, preferably ZSM-5).
According to a preferred embodiment of the present invention, the first adsorbent material (3) is selected from (i) granular, especially spherical, activated carbon particles, which activated carbon particles are provided, especially impregnated, with at least one reactive and/or catalytically active component based on a metal or a metal compound selected from the group consisting of copper, silver, cadmium, platinum, palladium, rhodium, zinc, mercury, titanium, zirconium, vanadium and/or aluminum and their ions, compounds and/or salts and combinations thereof and, optionally, also with an alkaline or acidic component.
Particularly good results can be achieved when the reactive and/or catalytically active component of the first adsorbent material comprises at least one, preferably at least two, of the metals selected from the group consisting of copper, silver, zinc, vanadium and/or molybdenum and their ions, compounds and/or salts and combinations thereof.
According to an embodiment of the present invention, the first adsorbent material may comprise the reactive and/or catalytically active component in an amount in the range of from 0.0001% by weight to 20% by weight, especially in the range of from 0.001% by weight to 15% by weight, preferably in the range of from 0.01% by weight to 10% by weight, more preferably in the range of from 0.05% by weight to 8% by weight, yet more preferably in the range of from 0.1% by weight to 6% by weight, based on the first adsorbent material.
Moreover, the first adsorbent material may comprise copper in an amount in the range of from 0.0001% by weight to 10% by weight, especially in the range of from 0.001% by weight to 8% by weight, preferably in the range of from 0.01% by weight to 6% by weight, based on the first adsorbent material. Furthermore, the first adsorbent material may comprise silver in an amount in the range of from 0.001% by weight to 1% by weight, especially in the range of from 0.01% by weight to 0.5% by weight, preferably in the range of from 0.03% by weight to 0.25% by weight, based on the first adsorbent material. Moreover, the first adsorbent material may comprise zinc in an amount in the range of from 0.0001% by weight to 10% by weight, especially in the range of from 0.001% by weight to 8% by weight, preferably in the range of from 0.01% by weight to 6% by weight, based on the first adsorbent material.
Even more, the first adsorbent material may comprise vanadium in an amount in the range of from 0.0001% by weight to 6% by weight, especially in the range of from 0.001% by weight to 5% by weight, preferably in the range of from 0.01% by weight to 3% by weight, based on the first adsorbent material. In particular, the first adsorbent material may comprise molybdenum in an amount in the range of from 0.0001% by weight to 6% by weight, especially in the range of from 0.001% by weight to 5% by weight, preferably in the range of from 0.01% by weight to 3% by weight, based on the first adsorbent material. On the basis of the abovementioned weights of the respective components, particularly good results can be achieved with respect to the first filter element, especially with regard to its adsorption capacity, and thus also with respect to the adsorption properties of the inventive filter unit as such.
In general, with respect to the reactive and/or catalytically active component, it is also advantageous if the reactive and/or catalytically active component of the first adsorbent material is at least essentially chromium free.
Furthermore, according to another embodiment of the present invention, the reactive and/or catalytically active component of the first adsorbent material may further comprise at least on acidic component, especially selected from the group consisting of inorganic acids, organic acids and their salts and combinations, especially sulfuric acid, preferably sulfuric acid salts, in particular selected from the group consisting of copper sulfates, zinc sulfate and ammonium sulfates. In this context, the first adsorbent material may comprise the acidic component in an amount in the range of from 0.0001% by weight to 5% by weight, especially in the range of from 0.001% by weight to 4% by weight, preferably in the range of from 0.01% by weight to 3.5% by weight, based on the first adsorbent material.
The additional use of acidic components is especially effective with respect to alkaline agents to be adsorbed and/or removed, especially ammonia (NH3).
Furthermore, according to the present invention, it is also possible that the reactive and/or catalytically active component of the first adsorbent material further comprises at least one alkaline and/or basic component, especially an organic amine, in particular triethylenediamine (TEDA). In this context, it is preferable when the first adsorbent material comprises the alkaline and/or basic component in an amount in the range of from 0.0001% by weight to 5% by weight, especially in the range of from 0.001% by weight to 4% by weight, preferably in the range of from 0.01% by weight to 3.5% by weight, based on the first adsorbent material.
The additional use of alkaline and/or basic components is preferred, especially with regard to the adsorption and/or removal of acidic agents, for example H2S.
The first adsorbent material may represent an ASZM-TEDA activated carbon (copper, silver, zinc, molybdenum and triethylenediamine impregnated activated carbon). Furthermore, it is also possible according to the present invention that the first adsorbent material represents an ASZM-TEDA activated carbon (activated carbon impregnated with copper, silver, zinc and triethylenediamine).
On the whole, the protective properties of the adsorptive filter unit can be further improved when the reactive and/or catalytic equipment of the adsorbent material on the basis of the above metal compounds is present together with triethylenediamine (TEDA) and/or an organic acid and/or sulfuric acid and/or sulfuric acid salts.
Particularly good results in respect of the adsorption properties with regard to poisonous and/or warfare agents are also obtainable according to the present invention when the reactive and/or catalytically active component of the first adsorbent material is based on a combination of (i) copper, more particularly copper(II) carbonate (CuCO3); (ii) silver, more particularly elemental silver; (iii) zinc, more particularly zinc(II) carbonate (ZnCO3); (iv) molybdenum, more particularly ammonium dimolybdate; (v) optionally triethylenediamine (TEDA).
In the aforementioned reactive and/or catalytically modification, the weight ratio of (i) copper/(ii) silver/(iii) zinc/(iv) molybdenum should be in the range of from 1 to 10/0.01 to 2/1 to 10/0.2 to 8, especially in the range of from 3 to 6/0.02 to 0.5/3 to 6/0.5 to 3, and preferably about 5/0.05/5/2.
Furthermore, according to a further embodiment preferred according to the present invention, the reactive and/or catalytically active component should contain (v) triethylenediamine (TEDA), wherein the amount ratio of (i) copper/(ii) silver/(iii) zinc/(iv) molybdenum/(v) triethylenediamine (TEDA) should be in the range of from 1 to 10/0.01 to 2/1 to 10/0.2 to 8/0.3 to 9, especially in the range of from 3 to 6/0.02 to 0.5/3 to 6/0.5 to 3/1 to 4, and preferably about 5/0.05/5/2/3.
According to a further embodiment preferred according to the present invention, the reactive and/or catalytically active component may be based on a combination of (i) molybdenum, more particularly selected from the group consisting of molybdenum oxides, molybdates and hexavalent molybdenum oxyanions; (ii) copper, more particularly selected from the group consisting of copper oxides, copper carbonates and copper-ammonium complexes, and/or zinc, more particularly selected from the group consisting of zinc oxides, zinc carbonates and zinc-ammonium complexes; (iii) sulfuric acid and/or sulfuric acid salt, more particularly selected from the group consisting of copper sulfates, zinc sulfate and ammonium sulfates.
In this context, the weight ratio of (i) molybdenum/(ii) copper and/or zinc/(iii) sulfuric acid should be in the range of from 1 to 15/1 to 25/1 to 15, and more particularly in the range of from 2 to 10/2 to 20/2 to 10.
With respect to a further embodiment preferred according to the present invention, the reactive and/or catalytically active component should be based on a combination of (i) copper, more particularly selected from the group consisting of copper oxides, copper carbonates, copper sulfates and copper-ammonium complexes; (ii) zinc, more particularly selected from the group consisting of zinc oxides, zinc carbonates, zinc sulfate and zinc-ammonium complexes; (iii) optionally silver, more particularly elemental silver; (iv) triethylenediamine (TEDA).
In this context, the weight ratio of (i) copper/(ii) zinc/(iii) optionally silver/(iv) triethylenediamine should be in the range of from 1 to 20/0.5 to 18/0 to 15/0.1 to 10, especially in the range of from 3 to 15/1 to 15/0 to 12/1 to 8, and preferably about 5/0.05/5/2.
The first adsorbent material of the first filter element which is provided with at least one reactive and/or catalytically active component may also comprise so-called ABEK impregnations which have a catalytic and/or degrading effect with regard to specific toxic substances. In this connection, type A relates for example to certain organic gases and vapors having a boiling point ≧65° C., for example cyclohexane. Type B relates to certain inorganic gases and vapors, for example hydrogencyanide. Type E relates to a degrading/protecting effect with regard to sulfur dioxide and other acidic gases and vapors. Type K finally relates to a protective function with regard to ammonia and organic ammonia derivatives. For further information, reference is made to the respective European standard EN 14387:2004.
As previously mentioned, it can be contemplated according to the present invention for ABEK type impregnations to be combined with a TEDA impregnation (ABEK-TEDA), in which case the adsorptive filter unit of the present invention also has an optimized protective function with regard to cyanogen chloride.
The addition of a TEDA impregnation also leads to a very good aging stability for the impregnation or the reactive and/or catalytically active component as such.
The provision and/or impregnation of the first adsorbent material can be performed by methods known to the skilled practitioner. In this context, the impregnation may be performed on the basis of solutions and/or dispersions of the respective catalytically active component which may be brought into contact with the activated carbon. The impregnation may be performed under heating and/or drying in order to obtain the respective impregnated activated carbon.
To obtain a high adsorption efficiency and capacity and a good breakthrough behavior of the filter unit of the invention at the same time, it is advantageous that the first adsorbent material, especially in the form of activated carbon and/or zeolites, has a mean particle diameter in the range of from 0.01 to 2.0 mm, in particular in the range of from 0.05 to 1.0 mm, preferably in the range of from 0.1 to 1.0 mm.
In general, the first adsorbent material, especially in the form of activated carbon and/or zeolites, is particularly mechanically stable and/or has a bursting pressure of at least 0.5 Newtons, especially at least 1 Newtons, preferably at least 2 Newtons, especially a bursting pressure in the range of from 0.5 Newtons to 20 Newtons, especially in the range of from 0.5 Newtons to 10 Newtons, per active carbon particle or active carbon bead.
Furthermore, the first adsorbent material, especially in the form of activated carbon and/or zeolites, should have an apparent (bulk) density in the range of from 500 g/l to 1,000 g/l, especially in the range of from 550 g/l to 900 g/l, preferably in the range of from 600 g/l to 800 g/l.
In general, the first adsorbent material, especially in the form of activated carbon and/or zeolites, should have a total porosity in the range of from 40% to 70%, especially in the range of from 45% to 65%, preferably in the range of from 50% to 60%, based on the first adsorbent material.
Furthermore, the first adsorbent material, especially in the form of activated carbon and/or zeolites, should have a moisture content in the range of from 0.01% by weight to 10% by weight, especially in the range of from 0.1% by weight to 5% by weight, preferably in the range of from 0.5% by weight to 3% by weight, based on the first adsorbent material. In this context, the moisture content has in general an influence on the adsorption properties of the activated carbon especially with regard to its reactive and/or catalytic properties. In this context, the applicant has surprisingly found out that the aforedescribed ranges specifically result in a further improvement of the adsorption properties of the first adsorbent material.
Additionally, the first adsorbent material, especially in the form of activated carbon and/or zeolites, may have a specific total pore volume in the range of 0.1 cm3/g to 2.5 cm3/g, especially in the range of from 0.2 cm3/g to 2.0 cm3/g, preferably in the range of from 0.3 cm3/g to 1.5 cm3/g, more preferably in the range of from 0.4 cm3/g to 1.0 cm3/g.
Moreover, the first adsorbent material, especially in the form of activated carbon and/or zeolites, should have a specific surface area (BET surface area) of at least 500 m2/g, especially at least 750 m2/g, preferably at least 1,000 m2/g, more preferably at least 1,200 m2/g. In this context, the first adsorbent material, especially in the form of activated carbon and/or zeolites, should have a specific surface area (BET surface area) in the range of from 500 m2/g to 2,500 m2/g, especially in the range of from 750 m2/g to 2,250 m2/g, preferably in the range of from 900 m2/g to 2,000 m2/g, more preferably in the range of from 1,000 m2/g to 1,750 m2/g.
The aforementioned BET values relate to pores having pore diameters up to 400 Å inclusive. For the BET method, reference can be made, for example, to Rompp Chemielexikon [Rompp's Chemical Encyclopaedia], 10th Edition, Georg Thieme Verlag, Stuttgart/New York, keyword: “BET method”, and the literature reviewed there, Winnacker-Küchler (3rd Edition), Volume 7, pages 93 ff. and Z. Anal. Chem. 238, pages 187 to 193 (1968).
Furthermore, the first adsorbent material, especially in the form of activated carbon and/or zeolites, should have an adsorption volume Vads of at least 250 cm3/g, especially at least 300 cm3/g, preferably at least 350 cm3/g, more preferably at least 400 cm3/g. In this context, the first adsorbent material, especially in the form of activated carbon and/or zeolites, should have an adsorption volume Vads in the range of from 250 cm3/g to 1,000 cm3/g, especially in the range of from 300 cm3/g to 900 cm3/g, preferably in the range of from 350 cm3/g to 750 cm3/g.
The aforementioned values relate to a measurement of the adsorption volume at a partial pressure p/p0 of 0.995 on pores having pore diameters in the range up to 400 Å inclusive.
In general, the total pore volume according to Gurvich of the first adsorbent material used according to the invention is also sufficiently high: In this context, the first adsorbent material, especially in the form of activated carbon and/or zeolites, should have a total pore volume according to Gurvich of at least 0.50 cm3/g, especially at least 0.55 cm3/g, preferably at least 0.60 cm3/g, more preferably at least 0.65 cm3/g, yet more preferably at least 0.70 cm3/g. In this context, the first adsorbent material, especially in the form of activated carbon and/or zeolites, has a total pore volume according to Gurvich in the range of from 0.50 cm3/g to 0.90 cm3/g, especially in the range of from 0.55 cm3/g to 0.85 cm3/g, preferably in the range of from 0.60 cm3/g to 0.80 cm3/g, more preferably in the range of from 0.65 cm3/g to 0.80 cm3/g, yet more preferably in the range of from 0.70 cm3/g to 0.75 cm3/g.
The aforementioned values relate to the determination at a partial pressure p/p0 of 0.995 on pores having a pore diameter up to 400 Å inclusive. For further details with respect to the determination of the total pore volume according to Gurvich, reference can be made to L. Gurvich (1915), J. Phys. Chem. Soc. Russ. 47, 805, and to S. Lowell et al., Characterization of Porous Solids and Powders: Surface Area Pore Size and Density, Kluwer Academic Publishers, Article Technology Series, pages 111 ff.
In general, all physicochemical data of the active carbon indicated equally relate to measurements on pores having pore diameters in the range of from >0 Å up to 400 Å.
According to the claimed invention, a large variety of activated carbon may be used. Especially, the first adsorbent material in the form of activated carbon may be obtainable by carbonization and subsequent activation of styrene/divinylbenzene copolymers, in particular divinylbenzene-crosslinked polystyrenes, preferably in granular form, particularly preferably in spherical form. In this context, the divinylbenzene content of the styrene/divinylbenzene copolymers should be in the range of from 1% by weight to 15% by weight, preferably in the range of from 2% by weight to 10% by weight, based on the styrene/divinylbenzene copolymers.
For example, an active carbon of this type of an active carbon prepared starting from phenolic resin beads (cf. for example, EP 1 440 692 B1) is superior in its action.
Active carbon employable according to the invention, which fulfills the aforementioned requirements and/or specifications containing the aforementioned physicochemical requirements is marketed, for example, by Blucher GmbH, Erkrath, Germany, and also Adsor-Tech GmbH, Premnitz, Germany.
On the whole, the first filter element of the inventive adsorptive filter unit in general exhibits a high capacity with respect to a broad variety and/or spectrum of poisonous or noxiant substances due to the use of a very specific adsorbent material as defined above.
Furthermore, also the second adsorbent material of the second filter element plays a fundamental role with respect to the purposeful optimization of the overall adsorption properties of the inventive adsorptive filter unit.
In this context, it is advantageous according to the claimed invention if the second adsorbent material is present in particulate form, especially in granular form, preferably in spherical form. In this context, the average particle diameter of the second adsorbent material shall be in the range of from 0.01 μm to 5 mm, especially in the range of from 0.1 μm to 3 mm, preferably in the range of from 0.2 μm to 2.5 mm, more preferably in the range of from 0.5 μm to 2 mm, yet more preferably in the range of from 1 μm to 1.5 mm.
Furthermore, particularly good results are achieved with respect to the surprisingly found improvement of the adsorption properties especially with regard to the adsorption of low and/or residual concentration of toxic substances, if the second adsorbent material comprises and preferably consists of at least one metal-organic framework material. In this context, the second adsorbent material shall comprise the at least one metal-organic framework (MOF) in bulk and/or as such.
For the purpose of the present invention, the second adsorbent material may thus be used in the form of “metal-organic frameworks (MOFs)”, also referred to synonymously as “MOF substances”, “MOF materials”, “porous coordination polymers” or the like, which are generally porous and have a crystalline structure. These metal-organic frameworks have relatively simple modular structures and form a specific class of porous materials. MOFs generally comprise a mononuclear complex as crosslinking point (“node”) to which a plurality of polyfunctional or polydentate ligands are bound. The term “metal-organic framework (MOF)” was coined by Omar Yaghi, one of the pioneers in the field of metal-organic frameworks. Various compounds have been named by Yaghi simply on the basis of the order in time in which they were discovered (e.g. MOF-2 originates from the year 1998 and MOF-177 originates from the year 2004).
For the purpose of the present invention, the term “metal-organic framework” refers, in particular to the inorganic-organic hybrid polymer obtained after its preparation, in particular after being freed of impurities, which is made firstly of repeating structural units based on metal ions, and secondly, bridging, in particular at least bidentate ligands. The metal-organic frameworks are thus made of metal ions which are joined to another via at least bidentate organic ligands so as to form a three-dimensional structure which has internal voids (pores), with the pores being defined or determined by, in particular, the metal atoms and the organic ligands joining them. An MOF material can have exclusively the same metal ions (e.g. copper or zinc, etc.) or else two or more different metal ions (i.e. metal ions of a different type, e.g. copper and zinc, etc.).
Further details regarding metal-organic frameworks (MOFs) may be found, for example, in the review article by S. Kaskel, “Forum per Baukasten” in: Nachrichten aus der Chemie, 53, April 2005, pages 394 to 399, and also the references cited therein.
The preparation of metal-organic frameworks as used is likewise adequately known to the skilled practitioner so that no further details are necessary in this respect. In this context, reference may be made to the reference cited above and in addition to the relevant patent literature, by way of example: WO 2007/023295 A2, US 2004/0097724 A1, WO 2005/04948 A1, WO 2005/068474 A1 and to WO 2005/049892.
Metal-organic frameworks are thus porous, generally crystalline materials, in particular materials having a well-ordered crystalline structure comprising metal-organic complexes having transition metals (e.g. copper, zinc, nickel, cobalt, etc.) as nodes and organic molecules (ligands) as connections or linkers between the nodes.
Furthermore, according to the claimed invention, it is also possible that the second adsorbent material comprises a mixture of metal-organic framework material (MOF) and a preferably organic binder. Especially, the second adsorbent material may comprise the at least one metal-organic framework material (MOF) in a form incorporated in an organic binder.
With respect to the optional use of an organic binder, another preferred embodiment according to the claimed invention can be seen in the measurement according to which the second adsorbent material comprises the metal-organic framework material (MOF) and the preferably organic binder in a MOF/binder ratio of >1 and in particular in the range of from 1:1 to 10:1, especially in the range of from 1.1:1 to 5:1, preferably in the range of from 1.2:1 to 3:1, more preferably in the range of from 1.4:1 to 2.5:1. Furthermore, the organic binder shall be an organic binder and may be more especially selected from the group consisting of polyesters, polystyrenes, poly(meth)acrylates, polyacrylates, celluloses, polyamides, polyolefins, polyalkylene oxides and mixtures thereof.
In general, the mixture of metal-organic framework (MOF) and organic binder shall be present in a form which can be processed to give shaped bodies, in particular in the form of spheres, grains, pellets, granules, rods or the like. In this context, the shaping may be carried out by shaping processes customary for these purposes, in particular compounding, extrusion, melt pressing or the like. The respective methods as such are well known to the skilled practitioner.
According to the claimed invention, it is also possible to provide the second adsorbent material and/or the second filter element as such via spunbonding methods, especially electrospunbonding methods, which especially applies to the provision of the second adsorbent material in the form of MOFs. The adsorbent material as such can then be present in filamentary form. The respective methods are known to the skilled practitioner. In particular, due to the applied methods on the basis of spunbonding, it is also possible to provide the second filter element in the form of very thin layers comprising a high density of the adsorbent material as such.
According to the present invention, the applicant has for the first time and surprisingly discovered that metal-organic frameworks (MOFs) are highly suitable with respect to the use in a very specific adsorptive filter unit within a filter element thereof arranged downstream to another filter element of the inventive adsorptive filter material, thereby effectively adsorbing low and/or residual concentrations of respective toxic substances to be adsorbed.
In this context, it is also possible to provide a high specificy of the second adsorbent material with regard to specific toxic substances and/or TICs. In this context, it is possible that the metal-organic frameworks are set within a wide range via the type and/or number of the at least bidentate organic ligands and/or the type and/or oxidation state of the metal ions. Accordingly, it is possible for the metal-organic framework to have very specific adsorption properties which may be tailored with regard to the specific application of the inventive filter unit. Especially, both the pore sizes and the pore sizes distribution of these porous materials in the form of MOFs can be set in a targeted manner during the synthesis, especially via the type and/or the number of ligands and/or via the type and/or oxidation state of the metals used. As indicated above, the metal-organic framework material (MOF) used according to the claimed invention for the second adsorbent material shall comprise repeating structural units based in each case on at least one metal, in particular metal atom or metal ion, and at least one at least bidentate and/or bridging organic ligand.
As metal, it is in principle possible to use all metals of the Periodic Table of the Elements, which are able to form a porous metal-organic framework with at least one at least bidentate and/or bridging organic ligand.
In particular, preference is given for the purpose of the present invention to the metal-organic frameworks material (MOF) of the second adsorbent material to comprise at least one metal, in particular metal atom or metal ion, selected from among elements of groups Ia, IIa, IIIa, IVa to VIIIa and also Ib and VIb of the Periodic Table of the Elements, especially selected from the group consisting of Mg, Ca, Sr, Ba, Sc, Y, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Mn, Re, Fe, Ru, Os, Co, Rh, Ir, Ni, Pd, Pt, Cu, Ag, Au, Zn, Cd, Hg, Al, Ga, In, Tl, Si, Ge, Sn, Pb, As, Sb and Bi, preferably selected from the group consisting of Zn, Cu, Ni, Pd, Pt, Ru, Th, Fe, Mn, Ag, Al and Co, more preferably selected from the group consisting of Cu, Fe, Co, Zn, Mn, Al and Ag, yet more preferably selected from the group consisting of Cu, Fe, Al and Zn.
Furthermore, the metal-organic framework of the second adsorbent material may comprise at least one at least bidentate and/or bridging organic ligand which has at least one functional group which is capable of forming at least two coordinate bonds to a metal, in particular metal atom or metal ion, and/or forming a coordinate bond to each of two more metals, especially metal atoms or metal ions, identical or different, where, in particular, the functional group of the ligand has at least one heteroatom, preferably from the group consisting of N, O, S, B, P, Si and Al, more preferably N, O and S.
In this context, the ligand should be selected from among at least divalent organic acids, in particular dicarboxylic acids, tricarboxylic acids, tetracarboxylic acids and mixtures thereof, particularly preferably unsubstituted or at last monosubstituted aromatic dicarboxylic, tricarboxylic or tetracarboxylic acids having, in particular, one, two, three, four or more rings, where, in particular, each of the rings can contain at least one heteroatom, identical or different, in particular N, O, S, B, P, Si and/or Al, preferably N, S and/or O.
Moreover, the metal-organic framework may be selected from the group consisting of Cu3(BTC)2, Zn2(BTC)2(DABCO), Al(NDC) and combinations thereof, especially Cu3(BTC)2.
The metal-organic framework (MOF) is usually present in crystalline form. In particular, the degree of crystallinity is at least 60%, in particular at least 70%, preferably at least 80%, particularly preferably at least 90%, particularly preferably at least 95%, very particularly preferably at least 99% or more, based on the MOF as such. As a result of the crystallinity, particularly good hardnesses, abrasion resistances and/or rupture strength of the sorbent can be obtained.
Particularly advantageous properties of the adsorptive filter unit can be achieved when the metal-organic framework material (MOF) of the second adsorbent material is present in activated form, preferably by means of heat treatment. Such activation generally leads to a not inconsiderable increase in the internal surface area (BET) and the total pore volume of the sorbent of the metal-organic framework (MOF). Activation can advantageously achieved by subjecting the second adsorbent material to a heat treatment, in particular after it has been prepared or before it is used in the adsorptive filter unit according to the invention. The thermal treatment to effect activation is carried out below the decomposition temperature, in particular at temperatures in the range of from 90° C. to 300° C., preferably in the range of from 100° C. to 250° C., more preferably in the range of from 110° C. to 220° C., preferably over a period from 0.1 to 48 hours, in particular from 1 to 30 hours, preferably from 5 to 24 hours. The heat treatment can be carried out either under an at least substantially unreactive, preferably at least substantially inert, atmosphere or else in an oxidizing atmosphere, for example in the presence of oxygen (e.g. under the ambient atmosphere). Without wishing to be tied to a particular theory, the positive effect of the activating treatment can be explained by existing pores being freed or purified of any impurities and/or additional pores, cracks, crevices or the like being generated on the surface of the MOFs during the activation, so that the porosity of the MOFs and thus the total pore volume and the internal surface area increase. The metal-organic framework material (MOF) of the second adsorbent material has internal voids, in particular pores, and/or wherein the metal-organic framework (MOF) is porous. This results in relatively high internal surface areas and total pore volume.
In this context, the metal-organic framework material (MOF) of the second adsorber material may have a total pore volume determined by the Gurvich method of at least 0.1 cm3/g, in particular at least 0.2 cm3/g, preferably at least 0.3 cm3/g. In this context, the metal-organic framework (MOF) should have a total pore volume determined by the Gurvich method of up to 2.0 cm3/g, in particular up to 3.0 cm3/g, preferably up to 4.0 cm3/g, particularly preferably up to 5.0 cm3/g.
Furthermore, the metal-organic framework material (MOF) of the second adsorbent material should further have a total pore volume determined by the Gurvich method in the range of from 0.1 cm3/g to 5.0 cm3/g, in particular in the range of from 0.2 cm3/g to 4.5 cm3/g, preferably in the range of from 0.3 cm3/g to 4.0 cm3/g.
Moreover, it is also advantageous according to the inventive concept, if the metal-organic framework material (MOF) of the second adsorbent material has a BET surface area of at least 100 m2/g, in particular at least 150 m2/g, preferably at least 200 m2/g, particularly preferably at least 250 m2/g, very particularly preferably at least 500 m2/g, even more preferably at least 1,000 m2/g. In this context, the metal-organic framework material (MOF) of the second adsorbent material should have a BET surface area of up to 4,000 m2/g, in particular up to 4,250 m2/g, preferably up to 4,500 m2/g, particularly preferably up to 4,750 m2/g, very particularly preferably up to 5,000 m2/g and more.
In particular, the metal-organic framework material (MOF) of the second adsorbent material has a BET surface area in the range of from 100 m2/g to 5,000 m2/g, in particular in the range of from 150 m2/g to 4,750 m2/g, preferably in the range of from 200 m2/g to 4,500 m2/g, particularly preferably in the range of from 250 m2/g to 4,250 m2/g, very particularly preferably in the range of from 500 m2/g to 4,000 m2/g.
Furthermore, the metal-organic framework material (MOF) of the second adsorbent material should have a bulk density in the range of from 50 g/l to 1,000 g/l, in particular in the range of from 100 g/l to 900 g/l, preferably in the range of from 150 g/l to 800 g/l.
Furthermore, with regard to the second adsorbent material, the aforenamed ion-exchange resins may be selected from the group consisting of anionic and cationic ion-exchange resins, e.g. cationic ion-exchange resins comprising sulfonic acid groups. Further, the alkaline component may be selected from the group consisting of inorganic and organic alkaline components, especially organic amines, in particular TEDA. In this context, also inorganic hydroxides, oxyhydroxides, carbonates and/or hydrogencarbonates may be used. Moreover, the acidic component of the second adsorbent material may be selected from the group consisting of inorganic and organic acids and their salts, especially sulfuric acid and their salts, phosphoric acids and their salts, halogen acids, in particular HCl, and their salts.
As already delineated above, the use of very specific adsorption materials also with respect to the second adsorbent material of the second filter element results in the provision of very specific adsorption properties of the filter unit as such, especially with regard to specific noxiants, wherein due to the excellent adsorption kinetics also low and/or residual concentrations of the respective substances are effectively adsorbed by the inventive filter medium due to the purposeful interaction of the first and second filter element.
With respect to the adsorptive filter unit as such, it is preferred according to an advantageous embodiment of the claimed invention that the first filter element comprises the first adsorbent material in an amount in the range of from 20% by weight to 100% by weight, especially in the range of from 30% by weight to 95% by weight, preferably in the range of from 40% by weight to 90% by weight, more preferably in the range of from 50% by weight to 85% by weight, yet more preferably in the range of from 60% by weight to 80% by weight, based on the first filter element.
Furthermore, the second filter element shall comprise the second adsorbent material in an amount in the range of from 15% by weight to 100% by weight, especially in the range of from 25% by weight to 95% by weight, preferably in the range of from 30% by weight to 80% by weight, more preferably in the range of from 35% by weight to 75% by weight, yet more preferably in the range of from 40% by weight to 70% by weight, based on the second filter element.
Furthermore, in particular, the first filter element comprises the first adsorbent material in the form of a loose fill and/or in bulk form and/or in loose form. In this context, also the second filter element may comprise the second adsorbent material in the form of a loose fill and/or in bulk form and/or in loose form.
Especially, the first filter element my comprise the first adsorbent material in the form of a loose fill and/or in bulk form and/or in loose form and/or the second adsorbent material of the second filter element may be fixed in and/or on at least one carrier structure.
According to a further alternative embodiment of the claimed invention, it is also possible that the first adsorbent material of the first filter element is fixed in and/or on at least one carrier structure. This also applies for the second adsorbent material, i.e. it is also possible according to the inventive concept that the second adsorbent material of the second filter element is fixed in and/or on at least one carrier structure.
In this context, the carrier structure of the first filter element and/or the carrier structure of the second filter element, independently from each other, are gas-permeable, in particular air-permeable, and in particular should have a gas permeability, in particular air permeability, of at least 10 l·m−2·s−1, in particular at least 30 l·m−2·s−1, preferably at least 50 l·m−2·s−1, more preferably at least
100 l·m−2·s−1, yet particularly preferably at least 500 l·m−2·s−1, and/or up to 10,000 l·m−2·s−1, in particular up to 20,000 l·m−2·s−1, at a flow resistance of 127 Pa.
Furthermore, according to a preferred embodiment of the present invention, the carrier structure of the first filter element and/or the carrier structure of the second filter element, independently from each other, have a three-dimensional structure and are especially configured as a preferably open-pored foam, especially a polyurethane foam, especially wherein the mean cell diameter of each carrier structure should be, independently from each other, at least twice as great as the mean particle diameter of the respective adsorbent material.
In particular, the carrier structure of the first filter element and/or the carrier structure of the second filter element, independently from each other, have a two-dimensional and/or sheet-like structure and are especially configured as a sheet-like, preferably textile, structure.
Furthermore, according to an embodiment of the claimed invention, the carrier structure of the first filter element and/or the carrier structure of the second filter element, independently from each other, should be configured as a sheet-like textile structure, preferably an air-permeable textile material, preferably a woven fabric, drawn-loop knit, formed-loop knit, lay-up or textile composite, in particular nonwoven. In this context, the carrier structure of the first filter element and/or the carrier structure of the second filter element, independently from each other, should have a weight per unit area in the range of from 5 g/m2 to 1,000 g/m2, especially 10 g/m2 to 500 g/m2, preferably 15 g/m2 to 450 g/m2.
In this context, the carrier structure of the first filter element and/or the carrier structure of the second filter element, independently from each other, should be sheet-like textile structures containing natural fibers and/or synthetic fibers (chemical fibers) or consisting thereof, in particular wherein the natural fibers are selected from the group consisting of wool fibers and cotton fibers (CO) and/or in particular wherein the synthetic fibers are selected from the group consisting of polyesters (PES); polyolefins, in particular polyethylene (PE) and/or polypropylene (PP); polyvinyl chlorides (CLF); polyvinylidene chlorides (CLF); acetates (CA); triacetates (CTA); polyacrylonitrile (PAN); polyamides (PA), in particular aromatic, preferably flame-resistant polyamides; polyvinyl alcohols (PVAL); polyurethanes; polyvinyl esters; (meth)acrylates; polylactic acids (PLA); activated carbon; and mixtures thereof.
Moreover, the first adsorbent material and/or the second adsorbent material, independently from each other, may be fixed to the respective support material of the first filter element and/or the second filter element, preferably by means of adhesive bonding, in particular by means of an adhesive or as a result of intrinsic stickiness or self-adhesion.
Also the respective dimensions and/or volumes of the filter elements play an important role with respect to the overall adsorptive and/or filtering properties of the inventive adsorptive filter unit as such. In this context, in particular, the first filter element has a height (h1), based on the size in parallel to the direction of flow (R) in particular of the fluid to be purified, in the range of from 1 mm to 100 mm, especially in the range of from 2 mm to 75 mm, preferably in the range of from 3 mm to 50 mm, more preferably in the range of from 4 mm to 40 mm, yet more preferably in the range of from 5 mm to 30 mm. In this context, the first filter element should have a weight per unit area in the range of from 10 g/m2 to 1,500 g/m2, especially in the range of from 20 g/m2 to 500 g/m2, preferably in the range of from 30 g/m2 to 400 g/m2, more preferably in the range of from 40 g/m2 to 300 g/m2.
Furthermore, the second filter element of the adsorptive filter unit according to the claimed invention should have a height (h2), based on the size in parallel to the direction of flow (R) in particular of the fluid to be purified, in the use state of the adsorptive filter unit, in the range of from 0.05 mm to 50 mm, especially in the range of from 0.1 mm to 30 mm, preferably in the range of from 0.15 mm to 10 mm, more preferably in the range of from 0.2 mm to 5 mm, yet more preferably in the range of from 0.4 mm to 4 mm, even more preferably in the range of from 0.5 mm to 3 mm. Especially, the second filter element should have weight per unit area in the range of from 5 g/m2 to 1,000 g/m2, especially in the range of from 5 g/m2 to 400 g/m2, preferably in the range of from 10 g/m2 to 300 g/m2, more preferably in the range of from 15 g/m2 to 200 g/m2.
Moreover, the ratio of the height (h1) of the first filter element to the height (h2) of the second filter element [ratio h1:h2], each based on the size in parallel to the direction of flow (R), should be in the range of from 1:1 to 25:1, especially in the range of from 1.5 to 1 to 15:1, preferably in the range of from 2:1 to 12:1, more preferably in the range of from 3:1 to 10:1.
Preferably, the filter elements may be stapled on each other and/or within the inventive filter unit. In this context, the respective filter elements may be affixed to each other preferably using a discontinuously applied adhesive. It is furthermore also within the scope of the present invention that the filter unit may consist of the first filter element and the second filter element.
As delineated above, the second filter element is to comprise a second adsorbent material which is different from the first adsorbent material comprised by the first filter element. This means that the first adsorbent material comprised by the first filter element, on the one hand, and the second adsorbent material comprised by the second filter element, on the other hand, have to be selected with the proviso that they differ from each other, especially that they differ by at least one property and/or parameter. If e.g. the first adsorbent material comprised by the first filter element is selected among zeolites, the second adsorbent material comprised by the second filter element should be selected by another material than zeolites or by different zeolites (i.e. zeolites differing e.g. in physicochemical properties, such as e.g. particle size, acidity, pore size, impregnation, chemical type etc.). However, according to a preferred embodiment, the first adsorbent material and the second adsorbent material should be selected by different species (i.e. if e.g. the first adsorbent material comprised by the first filter element is selected among zeolites, the second adsorbent material comprised by the second filter element should be selected by another material than zeolites and vice versa).
Further advantages, properties, aspects and features of the present invention will become apparent from the following description of an operative example depicted in the respective figures:
Furthermore,
The present invention further provides—in accordance with a second aspect of the present invention—a process for the purification of gases and/or gas mixtures, preferably air, and/or for the removal of chemical and/or biological substances or noxiants from gases and/or gas mixtures, preferably air, wherein the process comprises a process step of contacting a gas and/or gas mixture, preferably air, to be purified and/or to be cleaned from chemical and/or biological substances or noxiants with an adsorptive filter unit as defined above.
The inventive process can thus be performed by bringing the inventive adsorptive filter unit in contact with the gas, gas mixture and/or air to be purified, wherein the respective fluid is passed through the inventive adsorptive filter unit, e.g. due to the application of a pressure difference over the inventive filter unit.
In this context, the inventive process may be performed under specific relative humidities especially of the fluid, in particular gas, gas mixture and/or air, to be purified. In this context, the respective fluid to be purified should exhibit a relative humidity at room temperature (T=20° C.) in the range of from 5% RH to 100% RH, especially in the range of from 10% RH to 90% RH, preferably in the range of from 30 RH to 85% RH, more preferably in the range of from 40% RH to 80% RH, yet more preferably in the range of from 50% RH to 80% RH. Especially, very good results regarding the overall adsorption properties are achieved when the relative humidity of the fluid to be purified is relatively high, e.g. in the range of from 60% RH to 80% RH.
The present invention further provides—in accordance with a third aspect of the present invention—the use of an adsorptive filter unit as described according to the first aspect of the present invention for producing filters and filter materials of all types, in particular for the removal of pollutants, odorous substances and poisons of all types, in particular from streams of air and/or gas, for example NBC protective mask filters, odor filters, sheet-like filters, air filters, in particular filters for purification of air in a room, adsorptive support structures and filters for the medical sector.
Finally, the present invention also provides—in accordance with a fourth aspect of the present invention—a filter or filter material, in particular for the removal of pollutants, odorous substances and poisons of all types, in particular from streams of air and/or gas, for example NBC protective mask filters, odor filters, sheet-like filters, air filters, in particular filters for purification of air in a room, adsorptive support structures and filters for the medical sector, produced using an adsorptive filter unit as described and/or comprising an adsorptive filter unit as described with the first aspect of the present invention.
Further embodiments, modifications and variations of the present invention can readily be recognized and implemented by the skilled practitioner on reading the description, without exceeding the scope of the present invention.
The present invention is illustrated in the following with reference to operative examples, which, however, shall not restrict the present invention in any way.
Different adsorptive filter units which each consists of a single filter element are produced (comparative filter units 1a and 1b as well as 2a to 2d):
In a first series, with respect to comparative filters units 1a and 1b, the filter units as such exhibit only one filter element each, wherein the filter element of the respective filter units 1a and 1b comprises a specific adsorbent material on the basis of activated carbon provided with an ASZM-TEDA impregnation. With respect to filter unit 1a, the adsorbent is present in the form of a loose fill and/or bulk, respectively. In this context, the activated carbon is filled into the lumen of an appropriate cartridge having an inlet and an outlet opening allowing for the flow of air through the bulk material.
Furthermore, with respect to filter unit 1b, the adsorbent material is fixed onto a three-dimensional air-permeable carrier structure in the form of an open-pored polyurethane foam via an adhesive. Filter units 1a and 1b exhibit essentially the same height referring to the direction of flow through the filter unit in its use state. In this context, the height of filter units 1a and 1b is about 10 mm each and about ten times the height of each filter units 2a to 2b as described hereinafter.
In a second series, comparative filter units 2a, 2b, 2c and 2d are provided. The respective filter units each comprise one filter element only. The adsorbent material is affixed onto a three-dimensional air-permeable carrier structure in the form of a textile sheet material by using an adhesive, wherein the side of the adsorbent material opposite to the carrier structure is also covered with a respective sheetlike textile material (cf.
Table 1 specifies the abovementioned filter units 1a, 1b as well as 2a to 2d:
Moreover, an adsorptive filter unit 3a is made which consists of two filter elements as described with respect to filter unit 1b, i.e. comparative filter unit 3a consists of two identical filter elements on the basis of an ASZM-TEDA impregnated active carbon affixed onto a three-dimensional carrier. The respective filter elements are stapled onto each other and affixed to each other via a discontinuously applied adhesive.
Table 2 specifies the abovementioned filter unit 3a:
Moreover, adsorptive filter units 4a, 4b, 4c and 4d are provided. In particular, an inventive filter unit is produced, which consists of two filter elements, wherein the first filter element is for all adsorptive filter elements 4a, 4b, 4c and 4d as described with respect to filter unit 1b, i.e. all adsorptive filter units 4a, 4b, 4c and 4d each comprise a first filter element on the basis of an ASZM-TEDA impregnated activated carbon with an open-pored polyurethane foam as the carrier structure of the activated carbon. The second filter element of inventive filter unit 4a corresponds to filter unit 2a, i.e. the second filter element of 4a comprises an activated carbon having an acidic impregnation on the basis of sulfuric acid salts affixed on a respective carrier structure. Furthermore, inventive filter units 4b to 4d correspond to filter unit 4a with the proviso that according to filter unit 4b a second filter element on the basis of a specific MOF as defined in filter unit 2b is used, and that according to filter unit 4c a second filter element on the basis of a cationic ion-exchange resin as defined in filter unit 2c is used, and, finally, that according to filter unit 4d a second filter element on the basis of zeolite as defined in filter unit 2d is used.
Table 3 specifies the aforementioned filter units 4a to 4d:
The above named comparative and inventive filter units are investigated with respect of their protective performance with regard to noxiant substances, especially ammonia (NH3).
In general, high values of BTt correspond to a high performance of the tested filter units since it refers to the time period from the beginning of the test to the breakthrough of a defined concentration of the substance to be adsorbed (i.e. the higher the BTt-values the higher the filtering performance).
In this context, with increasing BTt-values, however, the CT-values may increase since over the whole time period until breakthrough (i.e. until passing the breakthrough threshold concentration at the filter output) very small residual amounts of the substance to be adsorbed (i.e. less than the threshold value for the determination of the breakthrough time) may pass through the filter unit and cumulate over the time period until BTt. Especially, filter units with high performance exhibit a balanced behavior of high BTt-values and moderate or acceptable CT-values.
Table 4 shows the results obtained in this regard for comparative Examples 1a and 1b, 2a to 2d, 3a and for inventive Examples 4a to 4d:
The test results show that the adsorption performance of the inventive filter units is significantly improved, resulting in increased breakthrough times as well as improved cumulative breakthrough values. Thus, the above test series demonstrates that the protective performance of the inventive filter units on the basis of two filter elements differing from each other and being specifically arranged to each other with regard to the flow direction of air surprisingly complement each other synergistically, i.e. beyond the sum of the individual effects.
Table 5 depicts the respective results:
The test results point to the importance of the specific arrangement of the filter elements with respect to the flow direction of air through the filter unit (cf. results of filter unit 4b in Table 1). Furthermore, the addition of a further second filter element as performed in filter unit 5a does only lead to minor changes in adsorption properties (cf. results of filter unit 4b in Table 1).
Table 6 depicts the respective results:
The test results point to the influence of the humidity of the air to be purified, wherein a higher humidity results in a further improvement of the adsorption performance of the inventive filter unit.
Finally, comparative adsorptive filter units 6a and 6b as well as 7a, on the one hand, and inventive adsorptive filter units 6a′, 6b′ as well as 7a′ are provided. The comparative filter units 6a, 6b as well as 7a exhibit only a single filter element on the basis of a filter element having a height of about 10 mm as defined in the following Table 7. Filter units 6a′, 6b′ as well as 7a′ correspond to filter units 6a, 6b as well as 7a′ with the proviso that an additional (i.e. second) filter element on the basis of a high density MOF-medium (Cu3(BTC)2) with a height of about 1.8 mm as defined in the below Table 7 is arranged downstream to the first filter element. Thus, two different filter arrangements are tested, i.e. a first series on the basis of one filter element only and a second series, the filter units of which comprise an additional Cu3(BTC)2-filter element arranged downstream of the first filter element. Furthermore, also the influence of the humidity of the air to be purified is tested.
For this purpose, the respective filter units are exposed to a stream of air enriched with a defined amount of NH3, wherein the NH3-concentration is adjusted to 1,000 mg/m3 at an air flow speed of 5.4 cm/s and a temperature of T=25° C. and wherein the relative humidity of the air to be purified is set at 15% RH and 70% RH, respectively. The breakthrough time (BTt) of NH3 is determined for a breakthrough value of 35 mg/m3 NH3.
Table 7 depicts the results for a relative humidity of 70% RH:
Table 8 depicts the results for a relative humidity of 15% RH:
Also this test series shows that the protective performance of the inventive filter units on the basis of two filter elements differing from each other and being specifically arranged to each other surprisingly complement each other synergistically, i.e. beyond the sum of the individual effects. The test results also show the influence of the humidity of the air to be purified, wherein a higher humidity results in a further improvement of the adsorption performance of the inventive filter unit.
The results thus altogether document the excellent protective performance on the basis of outstanding adsorption characteristics of the inventive filter unit, which performance is significantly improved over the prior art.
This application is a National Stage filing of International Application PCT/EP 2012/002454, filed Jun. 11, 2012, entitled “FILTERING MATERIAL AND USE THEREOF”. The subject application claims priority to PCT/EP 2012/002454, and incorporates all by reference herein, in its entirety.
