Filters and methods for removing aldehyde VOCs from indoor air

Abstract

Disclosed are filters and methods for removing aldehyde VOCs from indoor air. The filter includes a housing used as a container. The container includes two air-permeable opposite walls, and contains one or more natural polyphenols and a catalytic agent, and a large amount of the indoor air flows through the two walls. The filter is used as an absorption filter and reacts irreversibly with aldehyde VOCs in indoor air. Natural polyphenols are powdered polyphenols selected from resveratrol (3,4',5-trihydroxystilbene), resorcinol (1,3-benzene), pyrogallol (1,2,3-benzene), pyrogallol (1,3,5-benzene) and hydroquinone (1,4-benzene) or a combination thereof. The catalytic agent is a solid sulfonic acid. A mixture of natural polyphenols and the catalytic agent exists in a container as a compacted block unit. Also disclosed is an air purification / decontamination device including a filter.

Description

Technical Field

[0001] The present invention relates to an air filter, in particular an air filter for an air-purifying or air-decontaminating device, for removing or substantially eliminating pollutants from indoor air, which is suitable for residential areas, hospitals, leisure areas and workspace areas. The filter comprises a housing serving as a container, one or more natural polyphenols and a catalytic agent. The mixture of the natural polyphenols and the catalytic agent is present in the container as a compacted block component.

[0002] The air filter particularly relates to a filter suitable for capturing or removing aldehyde-type volatile organic compounds (VOCs), wherein the main aldehyde-type VOC captured or removed from indoor air is formaldehyde (HCHO, formic aldehyde).

[0003] In addition, the disclosed air filters can also remove or eliminate amine VOCs and ammonia, as well as imines and aminals resulting from their reactions with aldehydes, from indoor air.

[0004] Throughout this document, the abbreviation "VOC" or "VOCs" may be used instead of the term "volatile organic compounds". Background Art

[0005] In the prior art, there are a variety of air filters on the market that are capable of capturing VOCs containing aldehyde functional groups (mainly formaldehyde), such as those disclosed in document US 2016 / 228811-A1, wherein the filter comprises a solid carrier amine filter medium composed of a liquid amine and one or more granular solid carrier materials (including silica, clay, alumina, carbon, polymers, fibers or a combination thereof), wherein the solid carrier material is arranged in one or more filter sheets to provide an interaction between the amine present in the filter and the formaldehyde present in the air flowing through the filter medium.

[0006] Document WO 2017 / 114687 discloses a multilayer air filter consisting of a first layer comprising a catalyst, a second layer comprising an amine and optionally a third layer consisting of a water absorbing and releasing material (e.g. a hygroscopic material).

[0007] The reaction of polyphenols (e.g. resorcinol) with formaldehyde monomers obtained by heating an aqueous solution of formaldehyde (of polymeric nature, known as formaldehyde preservative or formalin) under alkaline conditions has been well known since the beginning of polymer chemistry. Phenol-formaldehyde (PF) polymers, also generally known as phenolic resins, and in particular resorcinol-formaldehyde resins (known as thermosetting phenolic resins), are present in many industrial products and are formed by step-growth polymerization.

[0008] Document US 2013 / 052113 discloses a method for purifying air and an air purifier for purifying air, wherein the air purifier comprises a filter having a fiber structure with a photocatalytic coating and a fan or turbine, the fiber structure having a photocatalytic coating, the fan or turbine wheel forcing air through the filter to remove VOCs. The air purifier may also include a scavenger medium, such as a phenolic compound (e.g., resorcinol).

[0009] Document CN 107321328 discloses a VOC adsorbent and a process for obtaining the VOC adsorbent, wherein the composition of the VOC adsorbent includes poly(vinyl alcohol), water, plant polyphenols, kaolin, an acidic liquid and a defoaming agent.

[0010] Document JPH11-226100 discloses filters comprising formaldehyde absorbents, namely plant polyphenols, in particular tea-derived polyphenols, such as flavan-3-ols and / or flavan-3-ol derivatives. Summary of the invention

[0011] The present invention aims to improve and solve certain problems of air filters available on the market by adding one or more polyphenolic substances and a catalytic agent or a mixture of catalysts as a compacted block reagent in the container of the air filter, which then reacts with aldehyde VOCs, mainly formaldehyde, which is an important indoor pollutant. The above-mentioned phenol-formaldehyde polymer formation reaction, conveniently and innovatively developed, has allowed the removal of formaldehyde gas in ppm (parts per million) concentrations. A component of the filter also allows one to capture also ammonia and amine VOCs (urine odor) present in any air flow, as well as imines and aminals produced by the reaction of aldehydes with said nitrogen compounds.

[0012] Formaldehyde is highly reactive as well as toxic, allergenic and carcinogenic, and when present at certain levels in indoor air, it can pose a serious safety hazard, causing a variety of health problems. Formaldehyde concentrations exceeding 0.1 ppm (parts per million) can cause eye irritation, while inhaling the air can also cause headaches, throat irritation and shortness of breath (SOB). Formaldehyde concentrations equal to or higher than 5 ppm in indoor air can cause death.

[0013] Despite all these health risks posed by formaldehyde and its derivatives, they are still widely used in various applications, such as: i) resins and adhesives, used in flooring and carpets or in the process of manufacturing furniture, where these industrially prepared resins and adhesives, once applied to buildings, may gradually release trace amounts of formaldehyde into the indoor air, and the process of releasing formaldehyde is accelerated when exposed to heat, such as due to the location near a heat source (radiator) or sunlight; ii) disinfectants, when present in aqueous solution, which is mainly used in operating rooms and other rooms or clean rooms in hospitals, because it kills most bacteria and fungi that may be present; iii) aqueous solutions used for the preservation of biological organs in hospitals, museums and biological laboratories, known as formalin or formaldehyde preservatives.

[0014] Thus, according to a first aspect, the present invention discloses an air filter for use in an air purification or air decontamination device for removing VOCs, particularly aldehyde VOCs, and in certain embodiments also amine VOCs from indoor air. The air filter comprises at least one housing serving as a container. The container comprises two air-permeable opposing walls through which a large volume of indoor air flows. The housing contains one or more natural polyphenols and a catalytic agent.

[0015] The air filter acts as an absorption filter, reacting irreversibly with the aldehyde VOCs in the indoor air. Due to this irreversible reaction, the air filter is able to very quickly absorb any traces of formaldehyde present in the indoor air, as well as (although not as quickly) other aldehyde VOCs that are less reactive, volatile and toxic than formaldehyde.

[0016] As for the one or more natural polyphenols in a powdered state (i.e., powdered polyphenols), they are particularly selected from the group consisting of resveratrol (3,4',5-trihydroxystilbene, a natural product present in large quantities in red grape skin and red wine), resorcinol (1,3-benzene), pyrogallol (1,2,3-benzene), phloroglucinol (1,3,5-benzene) and hydroquinone (1,4-benzene), or a combination thereof.

[0017] Furthermore, the catalytic agent is a solid sulfonic acid.

[0018] According to the proposed air filter, the mixture of the one or more natural polyphenols and the catalytic agent is present as a compacted block unit in a container.

[0019] According to the present invention, the compacted block units may be in the form of granules or pellets.

[0020] The diameter of the granules may be between 0.8 mm and 1.2 mm, preferably 1 mm, while the diameter of the pellets may be between 2.5 mm and 3.5 mm, preferably 3 mm.

[0021] In embodiments, the compacted block units are obtained by a pressure compaction process of one or more polyphenols and a catalytic agent.

[0022] In another embodiment, the compacted block units are prepared by a pressure compaction process at room temperature of one or more natural polyphenols and a catalytic agent and (one or more) binders or binding agents, such as cellulose, its derivatives or poly (1-vinylpyrrolidone-2-one) (povidone, PVP) and the like.

[0023] In certain embodiments, the air filter may include a plurality of shells arranged in a honeycomb configuration, wherein the two air permeable opposing walls are defined by two meshes.

[0024] In certain embodiments of the air filter, by increasing the proportion of the sulfonic acid component, the filter is also able to absorb large amounts of amine VOCs and ammonia, as well as imines and aminals produced by the reaction of amines with aldehydes.

[0025] The polyphenols included in the mixture are selected to remove aldehyde VOCs present in indoor air, including but not limited to: acetaldehyde or acetaldehyde, oxalic acid aldehyde or glyoxal, propanal or propionaldehyde, acrolein or acrolein, propargyl aldehyde or propyne aldehyde, methylglyoxal or 2-oxopropanal, glyoxylic acid and its alkyl esters, butanal or butyraldehyde, isobutyraldehyde or 2-methylpropanal, methacrolein or 2-methylacrolein, crotonaldehyde or both isomers of 2-butenal, valeraldehyde or valeraldehyde and isovaleraldehyde or 3-methylbutyraldehyde, especially formaldehyde (HCHO, formic aldehyde). Long chain aldehydes (i.e., aldehydes with molecular weights higher than the above aldehydes), such as those used in the cosmetics industry, may also be slowly absorbed, but they have a pleasant odor, so it is not necessary to capture them.

[0026] These aldehyde VOCs may contaminate indoor air as a result of the reaction of olefins (such as unsaturated hydrocarbons from the petroleum industry and several essential oils and natural fragrances used as air fresheners) with ozone (either externally or generated internally by laser printers, copiers, ion air purifiers, arc welders, or motor brushes). Aldehyde VOCs may also be generated by the atmospheric oxidation of ethanol vapor (from alcoholic beverages) and other short-chain primary alcohols (from perfumes).

[0027] The sulfonic acid used as the catalytic agent can be selected from any of the following:

[0028] - any aromatic sulfonic acid (Ar-SO3H), such as p-toluenesulfonic acid (TsOH.H2O or TsOH), or benzenesulfonic acid (BsOH),

[0029] - any alkanesulfonic acid (R-SO3H), for example 10-camphorsulfonic acid (CSA),

[0030] - any sulfonic acid resin, such as a strong acid ion exchange resin, or a sulfonic acid polymer, added in the form of a finely divided powder,

[0031] - the acid forms of thymol blue and related triphenylmethanesulfonic acid dyes,

[0032] - food dyes in acid form (e.g. Allura Red, E129 or Ponceau 4R, E124, and related azo derivatives), or

[0033] - Any long chain alkyl or aryl hydrogen sulfate, RO-SO3H or ArO-SO3H respectively, such as common detergents and surfactants in acidic form.

[0034] In an embodiment, polyphenol and sulfonic acid are used in a ratio of 1.0-2.0 to 0.1-1.0 w / w, respectively, preferably in a ratio of 1.0-0.2 w / w.

[0035] In an embodiment, the polyphenol is resveratrol.

[0036] In another embodiment, in particular when using granules as compacted block units, the term "polyphenol" refers to a mixture of resveratrol and resorcinol, wherein the proportion of resveratrol is between 10% and 75%, the proportion of resorcinol is between 75% and 10%, and the mixture also contains 15% w / w of solid sulfonic acid, TsOH.H2O (p-toluenesulfonic acid). In the case of using pellets, these percentages can be reduced due to the addition of 15-20% w / w of a binder.

[0037] In another embodiment, in particular when using granules as compacted block units, the polyphenol used is a mixture of resveratrol and resorcinol, the proportion of resveratrol being between 30% and 40% and the proportion of resorcinol being between 40% and 30%. In the last case, the solid sulfonic acid TsOH·H2O is present in a proportion of 30%. In the case of using pellets, the polyphenol used in the pellets is preferably a mixture of resveratrol and resorcinol, the proportion of resveratrol being between 20% and 35% and the proportion of resorcinol being between 35% and 20%, wherein the solid sulfonic acid is present in a proportion of 30% and the binder or binding agent may be present in a proportion of 15-20%.

[0038] On the other hand, the present invention also provides an air purification or air decontamination device, which comprises the air filter according to the first aspect of the present invention.

[0039] On the other hand, the present invention further discloses a method for removing VOCs, especially aldehyde-type VOCs, from indoor air, wherein a controlled airflow of contaminated indoor air passes through an air filter, the air filter comprising a housing serving as a container, the container comprising two air-permeable opposing walls, a large amount of the contaminated indoor air flows through the two walls, the housing containing one or more natural polyphenols and a catalytic agent, the aldehyde-type VOC reacts with the one or more natural polyphenols in the presence of the catalytic agent to produce a polymerized polyphenol-aldehyde resin, which is retained in the filter.

[0040] According to the proposed method, one or more natural polyphenols are in a powder state and are selected from the group consisting of: resveratrol (3,4',5-trihydroxystilbene), resorcinol (1,3-benzene), pyrogallol (1,2,3-benzene), pyrogallol (1,3,5-benzene) and hydroquinone (1,4-benzene) or a combination thereof. The catalytic agent is a solid sulfonic acid. The mixture of the one or more natural polyphenols and the catalytic agent is present in a container as a compacted block unit (in the form of particles or pellets) that captures the aldehyde VOC.

[0041] According to the proposed method, VOCs may also include amine VOCs and ammonia, as well as imines and aminals generated by their reactions with aldehyde VOCs.

[0042] Due to the presence of aldehyde VOCs in the indoor air, the reaction occurring in the filter will at some point reach a saturation level and therefore will become ineffective, so the method also includes an additional step where the air filter is removed and replaced once the saturation level is reached, as indicated by the visual indicator.

[0043] In certain embodiments, the indicator is the result of a sulfonic acid catalyzed reaction of formaldehyde and related VOCs with the polyphenol or polyphenol mixture contained in the filter, producing a red or reddish brown polymer when the reaction of formaldehyde and related VOCs with the polyphenol or polyphenol mixture used in the filter is complete. In other embodiments, the indicator can be the result of a color change of thymol blue and related dyes or a color change of food dyes and related azo dyes, all of which are used in their sulfonic acid form, i.e., when the acid groups have been neutralized with ammonia, amine VOCs, and / or derivatives of aldehydes and ammonia or amines.

[0044] It should be understood that any numerical range given may not be optimal at the extremes and that the present invention may need to be accommodated to these extremes, which is within the capabilities of one skilled in the art.

[0045] Other features of the present invention emerge from the following detailed description of embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] The foregoing and other advantages and features will be more fully understood from the following detailed description of embodiments, in an illustrative and non-limiting manner, with reference to the accompanying drawings, in which:

[0047] - Figures 1A-1C An example of an air filter for removing aldehyde VOCs from indoor air according to an embodiment of the present invention is illustrated;

[0048] - Figure 2 A first graph is shown comparing the amount / quantity of formaldehyde (HCHO or CH2O, formic aldehyde) absorbed or captured by a filter (Y-axis) versus the cumulative amount of HCHO that has passed through the filter (X-axis); and

[0049] - Figure 3 A second graph is shown which shows the amount of HCHO absorbed by the filter (Y-axis) versus the elapsed time (X-axis) during a first cycle in which a polluted air stream having a concentration of HCHO between 5 ppm and 4.41 ppm is introduced, corresponding to Figure 2 The chart shown. DETAILED DESCRIPTION

[0050] refer to Figure 1A , 1B , 1C, which shows an embodiment of the proposed air filter 1 for an air purification or air decontamination device. According to this embodiment, the air filter 1 includes a plurality of shells 10 arranged in a honeycomb structure. Each shell 10 of the proposed air filter 1 serves as a container for a plurality of compacted block units 11, in this particular case, in the form of pellets; however, although not shown, in other embodiments, the compacted block units 11 may be in the form of particles. In order to remove VOCs from indoor air, in particular aldehyde VOCs (i.e., aldehyde VOCs), in some embodiments, amine VOCs, ammonia, and imines and aminals produced by their reaction with aldehyde VOCs, particles or pellets of different sizes may be used; however, in a preferred embodiment of the present invention, the diameter of the particles is about 1 mm, while the diameter of the pellets is about 3 mm. As Figures 1A-1C As shown, the air filter 1 also comprises two air-permeable opposite walls defined by two webs 12 , 13 .

[0051] The compacted block unit 11 is formed from a mixture of one or more natural powdered polyphenols and a catalyst or catalytic agent.

[0052] In a preferred or specific embodiment, the compacted block units 11 are prepared into granules by a pressure compaction process of one or more natural powdered polyphenols and sulfonic acid at room temperature. In another preferred or specific embodiment, the compacted block units 11 are prepared in the form of pellets. In this case, one or more binders or adhesive agents, such as cellulose, cellulose derivatives and / or povidone or poly(1-vinylpyrrolidone-2-one), etc., are added supplementarily to prepare the corresponding pellets 11 by an extrusion process at room temperature.

[0053] It should be noted that in other embodiments, although less preferred, pellets may be prepared without the addition of said binding agent. Likewise, in other embodiments, particles may be prepared by adding one or more binders or binding agents to a mixture of one or more natural powdered polyphenols and a catalytic agent.

[0054] Discussed in this article Figure 2 and Figure 3 The graphs shown in show the results obtained in laboratory experiments carried out under certain predetermined conditions, with increasing exposure to formaldehyde concentrations up to about 5 ppm, which is well above the recommended long-term permissible exposure limit for humans, which is usually set between 0.75 ppm and 1.0 ppm (taking into account that formaldehyde concentrations of about 0.1 ppm can also be perceived and affect humans, such as odor and / or irritation), and in a much smaller range. These figures show the absorption of HCHO only during the first cycle.

[0055] The conditions used to test the effectiveness of the air filter's ability to absorb HCHO were carried out in a column of 2.5 cm in diameter, which was filled with beads prepared at room temperature from resveratrol (2.5 g), resorcinol (2.5 g), TsOH·H2O (1.0 g) as active ingredients and cellulose (1.5 g) and povidone (0.5 g) as binders or binding agents, and the column height or thickness was 4.0 cm.

[0056] The polluted air passed through the beads at an air flow rate of approximately 2.0 L / min and a velocity of 0.42 m / s. The formaldehyde concentration of the polluted air passing through the column was 4.360 ppm.

[0057] As shown in the figure, for these conditions, the amount of HCHO absorbed or captured by the filter in the column is most efficient during the first 100-150 minutes, where the filter absorbs approximately 100% of the HCHO present in the air stream flowing through the filter (already in the first cycle). Once this maximum percentage is reached, the slope trend shown in these figures with respect to the amount of HCHO absorbed or captured gradually decreases; indicating that the beads in the column of the simulated filter become saturated and therefore less efficient in absorbing HCHO. In addition, it can also be observed that when the filter seems to have reduced some of its high efficiency, after a period of interruption, the filter temporarily recovers its potential.

[0058] In a preferred embodiment, the housing of the air filter has the following dimensions, in cm: 40 length x 20 width x 4 height. However, these dimensions are non-limiting and can be varied accordingly so that the air filter can be appropriately inserted into all types of air purification or air decontamination devices.

[0059] Typically, the different components forming the mixture (i.e., polyphenols and catalytic agents) may be used in a ratio of 1.0-2.0 and 0.1-1.0 w / w, respectively. In a particular embodiment, polyphenols and catalytic agents are used in a ratio of 1.0 to 0.2 w / w.

[0060] It has been demonstrated through different tests that the proposed air filter can also efficiently eliminate malodors caused by amines and / or NH3 (urine smell). For this reason, it is also noted that it is advantageous to increase the proportion of sulfonic acid used to reduce one polyphenol. Therefore, considering the typical composition of the particles (without binding agents), such as the previously mentioned particles with the following proportions: 40% resveratrol, 50% resorcinol and 10% sulfonic acid, when resorcinol is limited to 30% and resveratrol is kept at 40%, the sulfonic acid can be increased to 30%, only as an example, not a limitation, an air filter is provided that efficiently filters aldehyde VOCs and simultaneously removes the odor.

[0061] For pellets containing a binding agent, it has also been noted that increasing the proportion of sulfonic acid used and reducing one polyphenol favors the removal of amines and related nitrogenous compounds. Thus, considering a typical composition with 35% resorcinol, 35% resveratrol, 15% p-toluenesulfonic acid and 15% binding agent, the resorcinol percentage or resveratrol percentage can be reduced to 20% and the sulfonic acid increased to 30%, which is only by way of example and not limitation, to provide an air filter that is highly efficient in removing aldehyde VOCs and simultaneously removing the odor.

[0062] Although various illustrative embodiments have been described above, numerous changes may be made to the various embodiments without departing from the scope of the invention as described in the claims. For example, in alternative embodiments, the order in which the various described method steps are performed may often be changed, and in other alternative embodiments, one or more method steps may be skipped altogether. Optional features of the filter embodiments may be included in some embodiments and not included in other embodiments. Therefore, the foregoing description is provided primarily for exemplary purposes and should not be construed as limiting the scope of the invention set forth in the claims.

Claims

1. A filter for removing aldehyde-type volatile organic compounds from indoor air, said filter (1) comprising at least one housing (10) acting as a container, said container (10) comprising two air-permeable opposite walls (12, 13) through which a large volume of said indoor air flows, said housing containing one or more natural polyphenols and a catalytic agent, wherein said filter acts as an absorption filter, reacting irreversibly with aldehyde-type volatile organic compounds of the indoor air, characterized in that: - the one or more natural polyphenols are powdered polyphenols and are selected from the group consisting of resveratrol, resorcinol, pyrogallol, phloroglucinol and hydroquinone or a combination thereof, and - the catalytic agent is a solid sulfonic acid, The mixture of the one or more natural polyphenols and the catalytic agent is present in a container as a compacted block unit (11).

2. The filter according to claim 1, wherein the compacted block unit (11) is in the form of granules or pellets.

3. The filter according to claim 2, wherein the diameter of the particles is between 0.8 mm and 1.2 mm, and wherein the diameter of the pellets is between 2.5 mm and 3.5 mm.

4. The filter according to any one of the preceding claims, wherein the compacted block units (11) are obtained by a pressure compaction process of the one or more natural polyphenols and the catalytic agent at room temperature.

5. A filter according to any one of the preceding claims 1 to 3, wherein the compacted block unit (11) is obtained by a pressure compaction process at room temperature of the one or more natural polyphenols and the catalytic agent and at least one binder selected from cellulose, its derivatives or poly(1-vinylpyrrolidone).

6. The filter according to claim 1, wherein the solid sulfonic acid used as a catalytic agent is selected from the group consisting of: - any aromatic sulfonic acid, - any alkanesulfonic acid, - any sulfonic acid resin, - Acid forms of thymol blue and triphenylmethanesulfonic acid dyes, - food dyes in acid form, or - Any long chain alkyl or aryl hydrogen sulfate in acidic form.

7. The filter according to claim 1, wherein the polyphenol and the sulfonic acid are used in a ratio of 1.0-2.0 and 0.1-1.0 w / w, respectively.

8. The filter according to claim 1, wherein the compacted block unit (11) is in the form of particles obtained by a pressure compaction process of the one or more natural polyphenols and the catalytic agent, and wherein: - the polyphenol used in the granules is a mixture of resveratrol and resorcinol, wherein the proportion of resveratrol is between 10% and 75%, the proportion of resorcinol is between 75% and 10%, and wherein the solid sulfonic acid TsOH·H2O (p-toluenesulfonic acid) is present at a percentage of 15%; or - The polyphenol used in the granules is a mixture of resveratrol and resorcinol, wherein the proportion of resveratrol is between 30% and 40%, the proportion of resorcinol is between 40% and 30%, and the solid sulfonic acid TsOH·H2O is present at a percentage of 30%.

9. A filter according to claim 1, wherein the compacted block unit (11) is in the form of pellets obtained by a pressure compaction process at room temperature of the one or more natural polyphenols and the catalytic agent and at least one binder selected from cellulose, its derivatives or poly (1-vinylpyrrolidone), and wherein the polyphenols used in the pellets are a mixture of resveratrol and resorcinol, the proportion of resveratrol is between 20% and 35%, and the proportion of resorcinol is between 35% and 20%, wherein the solid sulfonic acid TsOH·H2O is present in a proportion of 30%, and the binder or binding agent is present in a proportion of 15-20%.

10. The filter according to claim 1, further comprising a plurality of shells (10) arranged in a honeycomb structure, wherein the two air-permeable opposing walls (12, 13) are defined by two meshes.

11. Air purification or air decontamination device comprising a filter according to any one of claims 1 to 10.

12. A method for removing aldehyde-type volatile organic compounds from indoor air, wherein a controlled airflow of contaminated indoor air is passed through an air filter, said air filter comprising a housing serving as a container, said container comprising two air-permeable opposing walls through which a volume of said contaminated indoor air flows, said housing containing one or more natural polyphenols and a catalytic agent, said aldehyde-type volatile organic compounds reacting with said one or more natural polyphenols in the presence of said catalytic agent to produce a polymeric polyphenol-aldehyde resin, said polymeric polyphenol-aldehyde resin being retained in the filter, The one or more natural polyphenols are in powder form and are selected from the group consisting of: The group consisting of resveratrol, resorcinol, pyrogallol, phloroglucinol and hydroquinone or a combination thereof, wherein the catalytic agent is a solid sulfonic acid, and The mixture of the one or more natural polyphenols and the catalytic agent is present in a container as a compacted block unit.

13. The method of claim 12, wherein the aldehyde-based volatile organic compounds further include amine-based volatile organic compounds and ammonia.

14. The method according to claim 12 or 13, wherein the aldehyde volatile organic compound is selected from the group consisting of: The group consisting of formaldehyde, acetic aldehyde, oxalic aldehyde, propionaldehyde, acetic aldehyde, propargyl aldehyde, methylglyoxal, glyoxylic acid and its alkyl esters, n-butyraldehyde, isobutyraldehyde, methacrolein, two isomers of crotonaldehyde, n-valeraldehyde and isovaleraldehyde.

15. The method according to any one of the preceding claims 12 to 13, wherein the compacted block units are provided in the form of granules or pellets, wherein the diameter of the granules is between 0.8 mm and 1.2 mm and the diameter of the pellets is between 2.5 mm and 3.5 mm.

16. The method of claim 13, wherein the air filter is removed and replaced once an indicator of the filter reaches a saturation level, wherein the indicator operates due to: - the sulphonic acid catalysed reaction of formaldehyde and aldehyde volatile organic compounds with the polyphenol or polyphenol mixture contained in the filter, when the reaction of formaldehyde and aldehyde volatile organic compounds with the polyphenol or polyphenol mixture used in the filter is complete, or -The color change of thymol blue or the color change of food dyes when the acid groups are neutralized by amine volatile organic compounds, ammonia or aldehyde-amine derivatives, all of which are used in their sulfonic acid form.

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