Method for purifying 1,2-difluoroethylene

Abstract

This disclosure aims to efficiently adsorb and remove amines from a composition containing 1,2-difluoroethylene and amines using an adsorbent, thereby purifying 1,2-difluoroethylene. [Solution] A method for producing a purified 1,2-difluoroethylene-containing composition, comprising an adsorption step of contacting a composition containing 1,2-difluoroethylene and an amine with an adsorbent to obtain a composition in which the amine is reduced from the composition.

Description

[Technical Field]

[0001] This disclosure relates to a method for purifying 1,2-difluoroethylene. [Background technology]

[0002] Trans-1,2-difluoroethylene (HFO-1132(E)) is attracting attention as a refrigerant that can replace the greenhouse gases difluoromethane (HFC-32) and 1,1,1,2,2-pentafluoroethane (HFC-125) because of its low global warming potential (GWP).

[0003] Patent Document 1 discloses a method for producing a reaction gas containing (E)-1,2-difluoroethylene (R-1132(E)), comprising the steps of (1) obtaining the reaction gas by subjecting a raw material gas containing at least one fluoromethane selected from the group consisting of chlorodifluoromethane (R-22), difluoromethane (R-32), and fluoromethane (R-41) to a reaction including thermal decomposition, and (2) the raw material gas having a water vapor content of 1 volume% or less.

[0004] Patent Document 2 discloses a method for producing a composition containing HFO-1132(E) and / or HFO-1132(Z), comprising the steps of: (x) supplying a raw material gas containing 1,1,2-trifluoroethane (HFC-143), trans-1,2-difluoroethylene (HFO-1132(E)) and / or cis-1,2-difluoroethylene (HFO-1132(Z)) and a diluent gas to a reactor packed with a catalyst, thereby obtaining a reaction product containing HFO-1132(E) and HFO-1132(Z) by carrying out a dehydrofluorination reaction of HFC-143 and an isomerization reaction between HFO-1132(E) and HFO-1132(Z), wherein the content of the diluent gas in the raw material gas is 1 to 80 mol%;

[0005] Patent Document 3 discloses a method for producing purified HFO-1132(E), which includes an extraction distillation step in which a composition containing 1,1,1-trifluoroethane (HFC-143a) and trans-1,2-difluoroethylene (HFO-1132(E)) is contacted with a solvent containing an amine to obtain a composition in which the amount of HFC-143a is reduced from the composition. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] International Publication No. 2020 / 246611 [Patent Document 2] International Publication No. 2024 / 071127 [Patent Document 3] International Publication No. 2024 / 157980 [Overview of the project] [Problems that the invention aims to solve]

[0007] This disclosure aims to efficiently adsorb and remove amines from a composition containing 1,2-difluoroethylene and amines using an adsorbent, thereby purifying 1,2-difluoroethylene. [Means for solving the problem]

[0008] This disclosure includes, for example, the inventions described in the following sections.

[0009] Section 1. A method for producing a purified 1,2-difluoroethylene-containing composition, comprising an adsorption step of contacting a composition containing 1,2-difluoroethylene and an amine with an adsorbent to obtain a composition in which the amine is reduced from the composition.

[0010] Section 2. The manufacturing method according to item 1, wherein the 1,2-difluoroethylene is trans-1,2-difluoroethylene (HFO-1132(E)) and / or cis-1,2-difluoroethylene (HFO-1132(Z)).

[0011] Item 3. The amine has the general formula: NR 1 R 2 R 3 [wherein, R 1 , R 2 and R 3 each independently represents a hydrocarbon group having 1 to 3 carbon atoms which may be the same or different and may have a hydrogen or a substituent. However, the case where R 1 , R 2 and R 3 are all hydrogen is excluded.]. The manufacturing method according to item 1, wherein the amine is represented by the formula above.

[0012] Item 4. The manufacturing method according to item 1, wherein the amine has a standard boiling point of -10°C to 160°C.

[0013] Item 5. The manufacturing method according to item 1, wherein the amine is at least one amine selected from the group consisting of monomethylamine, dimethylamine, trimethylamine, monoethylamine, diethylamine, triethylamine, mono-n-propylamine, di-n-propylamine, tri-n-propylamine, mono-isopropylamine, and di-isopropylamine.

[0014] Item 6. The manufacturing method according to item 1, wherein the adsorbent is at least one adsorbent selected from the group consisting of zeolite, silica gel, activated carbon, molecular sieve, molecular sieving carbon, and silicon aluminum phosphate. [Advantages of the Invention]

[0015] According to this disclosure, it is possible to efficiently adsorb and remove amines from a composition containing 1,2-difluoroethylene and amines using an adsorbent, thereby purifying 1,2-difluoroethylene. [Brief explanation of the drawing]

[0016] [Figure 1] This figure shows an overview of a process for adsorbing and removing amines contained in a product containing 1,2-difluoroethylene according to one aspect of the present disclosure. [Modes for carrying out the invention]

[0017] In this specification, a numerical range represented by "~" means a range that includes the numbers written before and after "~" as the lower and upper limits (i.e., "greater than or equal to" and "less than or equal to").

[0018] In this specification, an azeotropic composition means a composition in which there is no difference in composition between the liquid phase and the gas phase under a constant pressure, and which behaves as if it were a single substance.

[0019] In this specification, an azeotropic composition refers to a composition that can form an azeotropic composition, has a composition that approximates an azeotropic composition, and exhibits behavior similar to that of an azeotropic composition. Azeotropic compositions can be distilled and / or refluxed with little change in composition. Therefore, azeotropic compositions can be treated substantially the same as azeotropic compositions. One characteristic of azeotropic compositions is that, in the pressure-composition diagram, the pressure difference between the boiling point curve and the dew point curve is within 5%.

[0020] In this specification, the standard boiling point means the boiling point at a standard atmospheric pressure of 1013.25 hPa.

[0021] In this specification, gauge pressure refers to relative pressure with respect to atmospheric pressure, and means the pressure difference obtained by subtracting atmospheric pressure from absolute pressure. In this specification, gauge pressure is expressed with a "G" prefix, for example, MPaG. On the other hand, if a pressure is expressed without a "G" prefix, it refers to atmospheric pressure.

[0022] In this specification, "purity" of a refrigerant means the component ratio (mol% or mass%) determined by quantitative analysis using gas chromatography.

[0023] In this specification, the main component refers to a component that is preferably present in an amount of 85 mol% to 99.9 mol%, more preferably 90 mol% to 99.9 mol%, even more preferably 95 mol% to 99.9 mol%, and particularly preferably 99 mol% to 99.9 mol%.

[0024] In this specification, extractive distillation refers to a distillation operation that facilitates separation by adding an extraction solvent to a mixture consisting of two or three components with very close standard boiling points, which are difficult to separate by ordinary distillation, and which have a specific volatility (relative volatility) close to 1, or a combination of components with an azeotropic composition, thereby increasing the relative volatility of the original two or three components away from 1. Note that if the relative volatility is 1, separation by distillation becomes impossible.

[0025] In the production process of 1,2-difluoroethylene, 1,1,1-trifluoroethane (HFC-143a), which is difficult to separate, is produced. 1,2-difluoroethylene containing HFC-143a can be obtained, for example, by the thermal decomposition of HFC-32 as shown in Reference 1 (International Publication 2020 / 246611), or by the dehydrofluoric acid reaction and isomerization reaction of HFC-143 as shown in Reference 2 (International Publication 2024 / 71127).

[0026] To separate HFC-143a from products containing 1,2-difluoroethylene, the 1,2-difluoroethylene purification process employs extractive distillation using amines as solvents (extraction solvents).

[0027] However, in the purification of 1,2-difluoroethylene using extractive distillation, there is a possibility that trace amounts of amines used as the extractive distillation solvent may be present in the product. Even trace amounts of amines used in the extractive distillation process can be present in products containing 1,2-difluoroethylene, which can significantly affect the quality of the product, such as causing odors.

[0028] Therefore, the Disclosers have conducted diligent research and have found that amines can be efficiently adsorbed and removed from an adsorbent composition (adsorption composition) by a manufacturing method that includes an adsorption step in which a composition containing 1,2-difluoroethylene and an amine (adsorption composition) is brought into contact with an adsorbent to obtain a composition in which the amine content has been reduced, thereby purifying 1,2-difluoroethylene. The Disclosers have found that it is preferable to use an adsorption tower packed with a specific adsorbent in the adsorption step.

[0029] According to this disclosure, amines are removed from products containing 1,2-difluoroethylene, which stabilizes and improves the quality of products containing 1,2-difluoroethylene and enhances their value.

[0030] This disclosure is the result of further research based on the aforementioned findings.

[0031] This disclosure includes the following embodiments.

[0032] (1) Adsorption process This disclosure relates to a method for producing a composition containing purified 1,2-difluoroethylene, and includes an adsorption step in which a composition containing 1,2-difluoroethylene and an amine (adsorption composition) is brought into contact with an adsorbent to obtain a composition in which the amine content has been reduced from the adsorption composition.

[0033] The adsorption step in the manufacturing method of this disclosure is a step of contacting a composition containing 1,2-difluoroethylene and an amine (adsorption composition) with an adsorbent to obtain a composition in which the amine has been reduced from the adsorption composition. The adsorption step is, for example, a step of using an adsorption tower filled with a specific adsorbent to obtain a composition in which the amine has been reduced from the adsorption composition.

[0034] In this disclosure, "reduction" in the adsorption process means reducing the proportion of a specific compound (amine) in the adsorption composition.

[0035] The adsorption composition contains 1,2-difluoroethylene and amine in a total concentration of preferably 99.5% by mass or more, more preferably 99.7% by mass or more, even more preferably 99.8% by mass or more, and still more preferably 99.9% by mass or more.

[0036] For example, in the manufacturing process of 1,2-difluoroethylene (HFO-1132(E), etc.), after removing easily separable by-products through a prior separation step (such as an optional distillation step) as needed, a composition containing 1,2-difluoroethylene and an amine in the above-mentioned total concentrations can be applied.

[0037] The adsorption composition preferably consists only of 1,2-difluoroethylene and an amine, but the presence of unavoidable impurities due to the conditions of the preparation process of the adsorption composition is acceptable.

[0038] The adsorption step is preferably a step in which an adsorption composition is brought into contact with an adsorbent to adsorb amines onto the adsorbent, thereby obtaining a composition that contains 1,2-difluoroethylene but is substantially free of amines.

[0039] In this specification, "substantially amine-free" means that the amine content in the composition obtained in the adsorption step is preferably less than 1% by mass, more preferably less than 0.5% by mass, and particularly preferably less than 0.1% by mass.

[0040] (1,2-difluoroethylene) The 1,2-difluoroethylene contained in the adsorption composition is preferably trans-1,2-difluoroethylene (HFO-1132(E)) and / or cis-1,2-difluoroethylene (HFO-1132(Z)).

[0041] (amine) In the manufacturing process of 1,2-difluoroethylene (HFO-1132(E), etc.), 1,1,1-trifluoroethane (HFC-143a), which is difficult to separate, is produced. To separate HFC-143a from products containing 1,2-difluoroethylene, the purification process of 1,2-difluoroethylene employs extractive distillation using an amine (methylamine, etc.) as the extraction solvent.

[0042] The amine contained in the adsorption composition is preferably of the general formula:NR 1 R 2 R 3 It is an amine represented by the formula, where R 1 , R 2 and R 3 R represents a hydrocarbon group having 1 to 3 carbon atoms, which may have the same or different hydrogen atoms or substituents. However, R 1 , R 2 and R 3 Except when all of them are hydrogen.

[0043] The amines in this disclosure may contain unavoidable impurities to the extent that they do not affect the adsorption process.

[0044] The amine is preferably an amine having a standard boiling point of -10°C to 160°C.

[0045] The amine is preferably at least one amine selected from the group consisting of monomethylamine, dimethylamine, trimethylamine, monoethylamine, diethylamine, triethylamine, mono-n-propylamine, di-n-propylamine, tri-n-propylamine, mono-isopropylamine, and di-isopropylamine.

[0046] These amines may be present individually or in combination of two or more.

[0047] (Adsorbent material) The adsorbent used in the adsorption process of this disclosure is preferably at least one adsorbent selected from the group consisting of zeolite, silica gel, activated carbon, molecular sieve, molecular sieving carbon, and silicon aluminophosphate.

[0048] Preferably, the zeolite (molecular sieve) is MS3A (pore size of 3 Å effective diameter, Fujifilm Wako Pure Chemical Industries), MS13X (used for adsorption of molecules with a pore size of 10 Å or less, Fujifilm Wako Pure Chemical Industries), or HiSiv. TM 3000 (solvent with a relatively small molecular diameter (6 Å or less), Resonaq Universal), MS4A (pore size of about 4 Å), MS5A (pore size of about 5 Å), ZSM-5 (pore size of about 5.8 Å), L-type zeolite (pore size of about 8 Å), Y-type zeolite (pore size of about 9 Å), mordenite (pore size of about 7 Å), etc. (for example, manufactured by Tosoh Corporation) can be used.

[0049] Preferably, silica gel can be Mizukasil, Mizukasorb (Mizusawa Chemical Industry), Fuji Silica Gel Type A, Type B (Fuji Silicia), etc.

[0050] Preferably, activated carbon and molecular sieving carbon can be granular Shirasagi G series, Molcybon (Osaka Gas Chemical), Kuraraycol (Kuraray), etc.

[0051] Preferably, silica aluminophosphate such as SAPO-34 or SAPO-18 can be used.

[0052] Amines such as methylamine have a strong odor, and if they are present in trace amounts in products containing 1,2-difluoroethylene, they may degrade the quality of the 1,2-difluoroethylene-containing product. In the adsorption process of this disclosure, by using at least one adsorbent selected from the group consisting of zeolite, silica gel, and activated carbon, an adsorption tower filled with the adsorbent can be installed to adsorb and remove trace amounts of amines present in products containing 1,2-difluoroethylene.

[0053] (Adsorption process, Figure 1) A process is constructed to adsorb and remove amines (such as monomethylamine) contained in compositions containing 1,2-difluoroethylene (such as HFO-1132(E)) (products containing 1,2-difluoroethylene, adsorption compositions) by filling an adsorption tower used in the actual process with an adsorbent.

[0054] By filling the aforementioned adsorbent into a prepared adsorption tower and continuously processing a composition containing an amine (such as monomethylamine) and 1,2-difluoroethylene, substantially amine-free 1,2-difluoroethylene can be obtained. Multiple adsorption towers can be installed and used by switching between the tower that performs regeneration and the tower through which the gas to be treated flows. There is no particular limit to the number of towers, but preferably, two to five towers are used for the most efficient operation.

[0055] There are no particular restrictions on the size of the adsorption tower, but preferably an adsorption tower with an outer diameter of 0.5 m to 2 m and a height of 1 m to 4 m is used.

[0056] In the adsorption process, the operating pressure is preferably adjusted to 0.05 MPaG to 3 MPaG (gauge pressure), more preferably to 0.1 MPaG to 2 MPaG, even more preferably to 0.25 MPaG to 1.5 MPaG, and particularly preferably to 0.3 MPaG to 1 MPaG. In the adsorption process, the operating pressure is preferably set to 0.4 MPaG.

[0057] In the adsorption process, the operating temperature is preferably adjusted to -10°C to 50°C, more preferably to -10°C to 40°C, and even more preferably to -10°C to 35°C.

[0058] The adsorption process can be carried out in either batch or continuous operation. From an industrial standpoint, it is preferably carried out in continuous operation.

[0059] Furthermore, in the adsorption process, multiple adsorption towers can be used in parallel or in series. This allows for more efficient reduction of amines, making it possible to obtain a more purified 1,2-difluoroethylene-containing composition (purified composition).

[0060] The adsorption process involves distributing the adsorption composition into an adsorption tower at a space velocity (SV) of preferably 0.5 / h. -1 ~10,000 / h -1 Adjust to, more preferably, 1 / h -1 ~5,000 / h -1 Adjust the speed to 1.5 / h, more preferably 1.5 / h -1 ~3,000 / h -1 Adjust the speed and distribute it.

[0061] According to this disclosure, when a composition containing 1,2-difluoroethylene (purified composition, gas composition) flowing out from the outlet of an adsorption tower is analyzed by gas chromatography, the amines in the gas can be reduced to below the detection limit, and a process can be constructed to remove amines contained in the adsorption composition containing 1,2-difluoroethylene.

[0062] According to this disclosure, it is possible to efficiently adsorb and remove amines from a composition containing 1,2-difluoroethylene and amines using an adsorbent, thereby obtaining a composition containing 1,2-difluoroethylene (purified composition) in which 1,2-difluoroethylene is more purified.

[0063] (2) A composition containing purified 1,2-difluoroethylene This disclosure includes compositions containing purified 1,2-difluoroethylene (preferably HFO-1132(E)), as well as compositions (purified compositions) containing 1,2-difluoroethylene and an amine. The type of amine is the same as that described in the section on amines.

[0064] The purified composition is a composition containing 1,2-difluoroethylene and an amine, wherein the total concentration of the two components, 1,2-difluoroethylene and the amine, relative to the entire composition is preferably 99.5% by mass or more.

[0065] The purified composition is a composition containing 1,2-difluoroethylene that is ultimately obtained in the manufacturing method of the present disclosure, in which a trace amount of amine remains.

[0066] The total concentration of the two components, 1,2-difluoroethylene and amine, relative to the entire purified composition is more preferably 99.7% by mass or more, even more preferably 99.8% by mass or more, and particularly preferably 99.9% by mass or more.

[0067] The purified composition is a composition containing 1,2-difluoroethylene and an amine, wherein the content of 1,2-difluoroethylene relative to the whole composition is preferably more than 99.0% by mass and up to 100% by mass. More preferably, the content of 1,2-difluoroethylene is 99.5% by mass or more, 99.6% by mass or more, 99.7% by mass or more, 99.8% by mass or more, and even more preferably 99.9% by mass or more.

[0068] The purified composition is a composition containing 1,2-difluoroethylene and an amine, wherein the amine content relative to the whole composition is preferably greater than 0% by mass and less than or equal to 0.1% by mass. The notation of "greater than 0% by mass" can also be expressed as, for example, 0.01% by mass (100 mass / pm) or more, 0.001% by mass (10 mass / pm) or more, 0.0001% by mass (1 mass / pm) or more, 0.00001% by mass (0.1 mass / pm) or more, 0.000001% by mass (0.01 mass / pm) or more, etc.

[0069] The purified composition is a composition containing 1,2-difluoroethylene and an amine, wherein the amine content relative to the whole composition is preferably 0.1% by mass (1,000 mass ppm) or less, more preferably 0.01% by mass (100 mass ppm) or less, 0.001% by mass (10 mass ppm) or less, 0.0001% by mass (1 mass ppm) or less, and even more preferably 0.00001% by mass (0.1 mass ppm) or less.

[0070] The purified composition preferably consists only of 1,2-difluoroethylene and an amine, and the presence of unavoidable impurities is acceptable.

[0071] The composition can preferably be used, for example, as a leak detection agent, stabilizer, or tracer when using refrigerants. [Examples]

[0072] The present disclosure will be specifically explained below with reference to examples. However, the present disclosure is not limited to these examples.

[0073] In the examples, the concentrations of each component, such as 1,2-difluoroethylene (HFO-1132(E), etc.), were measured using a gas chromatography apparatus (with an FID detector).

[0074] (Example 1) A 1g serving of adsorbent (porous adsorbent) is placed in a 50cc stainless steel container and heated to 130°C using a constant temperature bath to perform a pretreatment to remove adsorbed water, gas, etc.

[0075] Monomethylamine was used as the amine to be adsorbed onto the adsorbent. Trans-1,2-difluoroethylene (HFO-1132(E)) (99.99% purity) was used as the 1,2-difluoroethylene.

[0076] A gas containing 4,000 ppm monomethylamine (manufactured by Mitsubishi Chemical, 99.97% purity) was prepared using HFO-1132(E). This gas was introduced into a SUS cylinder containing pre-treated adsorbent.

[0077] After introducing the gas, the mixture was allowed to stand at 25°C for 24 hours to reach adsorption equilibrium. The gas was then sampled and its composition was analyzed by gas chromatography. The amount of adsorbed monomethylamine was quantified from the results, and the proportion of the original sample gas (adsorption rate) adsorbed onto the adsorbent was calculated.

[0078] The results are summarized in Table 1 below.

[0079] [Table 1]

[0080] From these results, it was found that zeolite, silica gel, and activated carbon are effective adsorbents.

[0081] (Example 2) A process for adsorbing and removing amines contained in HFO-1132(E) was constructed by filling an adsorption tower used in the actual process with the adsorbent whose adsorption capacity was tested in Example 1.

[0082] Figure 1 illustrates this process.

[0083] Using silica gel (FUJI SORB G-A1030) as the adsorbent, the following adsorption tower was prepared, and HFO-1132(E) containing monomethylamine was continuously processed.

[0084] An adsorption tower with an outer diameter of 100 Å and a height of 1 m was filled with 5 kg of silica gel. The operating pressure was set to 0.4 MPaG and the operating temperature to 0°C.

[0085] A process was established to remove monomethylamine contained in product HFO-1132(E) by flowing HFO-1132(E) containing 100 ppm of monomethylamine through an adsorption tower at a rate of 5.8 L / min.

[0086] A process was constructed to remove monomethylamine contained in product HFO-1132(E). Analysis of HFO-1132(E) flowing out of the adsorption column outlet by gas chromatography revealed that the amount of monomethylamine in the gas was below the detection limit (less than 0.1 mass / pm).

[0087] (Example 3) Zeolite (MS3A) was used as the adsorbent, and the adsorption tower shown in Figure 1 was prepared in the same manner as in Example 2, and HFO-1132(E) containing monomethylamine was continuously processed.

[0088] 5 kg of zeolite was packed into the adsorption tower. The operating pressure was set to 0.4 MPaG and the operating temperature to 0°C.

[0089] A process was established to remove monomethylamine contained in product HFO-1132(E) by flowing HFO-1132(E) containing 100 ppm of monomethylamine through an adsorption tower at a rate of 5.8 L / min.

[0090] A process was constructed to remove monomethylamine contained in product HFO-1132(E). Analysis of HFO-1132(E) flowing out of the adsorption column outlet by gas chromatography revealed that the amount of monomethylamine in the gas was below the detection limit (less than 0.1 mass / pm).

[0091] (Example 4) Using activated carbon (granular Shirasagi G2X7 / 12-1) as the adsorbent, an adsorption tower as shown in Figure 1 was prepared in the same manner as in Example 2, and HFO-1132(E) containing monomethylamine was continuously treated.

[0092] 5 kg of activated carbon was packed into the adsorption tower. The operating pressure was set to 0.4 MPaG and the operating temperature to 0°C.

[0093] A process was established to remove monomethylamine contained in product HFO-1132(E) by flowing HFO-1132(E) containing 100 ppm of monomethylamine through an adsorption tower at a rate of 5.8 L / min.

[0094] A process was constructed to remove monomethylamine contained in product HFO-1132(E). Analysis of HFO-1132(E) flowing out of the adsorption column outlet by gas chromatography revealed that the amount of monomethylamine in the gas was below the detection limit (less than 0.1 mass / pm). [Industrial applicability]

[0095] According to this disclosure, it is possible to efficiently adsorb and remove amines from a composition containing 1,2-difluoroethylene and amines using an adsorbent, thereby purifying 1,2-difluoroethylene. The process of this disclosure, using a specific adsorbent, is highly effective in separating 1,2-difluoroethylene from amines.

Claims

1. A method for producing a purified 1,2-difluoroethylene-containing composition, comprising an adsorption step of contacting a composition containing 1,2-difluoroethylene and an amine with an adsorbent to obtain a composition in which the amine is reduced from the composition.

2. The method for producing 1,2-difluoroethylene according to claim 1, wherein the 1,2-difluoroethylene is trans-1,2-difluoroethylene (HFO-1132(E)) and / or cis-1,2-difluoroethylene (HFO-1132(Z)).

3. The aforementioned amine has the general formula: NR １ R ２ R ３ [In the formula, R １ , R ２ and R ３ each independently represent a hydrocarbon group having 1 to 3 carbon atoms which may be the same or different and may have a hydrogen atom or a substituent. However, the case where R １ , R ２ and R ３ are all hydrogen atoms is excluded. ] The manufacturing method according to claim 1, wherein the amine is represented by .

4. The method for producing according to claim 1, wherein the amine is an amine having a standard boiling point of -10°C to 160°C.

5. The manufacturing method according to claim 1, wherein the amine is at least one amine selected from the group consisting of monomethylamine, dimethylamine, trimethylamine, monoethylamine, diethylamine, triethylamine, mono-n-propylamine, di-n-propylamine, tri-n-propylamine, mono-isopropylamine, and di-isopropylamine.

6. The manufacturing method according to claim 1, wherein the adsorbent is at least one adsorbent selected from the group consisting of zeolite, silica gel, activated carbon, molecular sieve, molecular sieving carbon, and silicon aluminophosphate.

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