Chabazite-type zeolite

Abstract

To provide a chabazite-type zeolite which not only exhibits a VOC adsorption property sufficient under a dry environment but also does not cause the large deterioration of the VOC adsorption property even under a highly humid environment, and is excellent in the VOC adsorption property, and a VOC adsorbent containing the chabazite-type zeolite.SOLUTION: A ratio (A) / (B) of a BET specific surface area (A) measured by a water vapor adsorption method to a BET specific surface area (B) measured by a nitrogen adsorption method is in a range of 0.40 or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a chabazite-type zeolite and an adsorbent for volatile organic compounds comprising the chabazite-type zeolite. [Background technology]

[0002] Zeolites are crystalline aluminosilicates with a framework of silicon dioxide, aluminum oxide, etc., and regular channels (pores). Chabazite-type zeolites in particular are silica-rich and are widely known for containing pores (3.8 x 3.8 Å) with eight-membered ring structures.

[0003] It is known that Al2O3 in the crystalline framework of zeolite affects hydrophilicity, with the greater the Al content, the higher the hydrophilicity, and the lower the Al content, the lower the hydrophilicity. Silica-rich chabazite-type zeolite has low hydrophilicity due to its low Al content, and therefore has high adsorption properties for hydrophobic substances, and its use as an adsorbent for nitrogen oxides has been proposed (see, for example, Patent Document 1).

[0004] In addition, like chabazite-type zeolite, MFI-type zeolite is a crystalline aluminosilicate having regular channels (pores), but has a different skeletal structure. MFI-type zeolite contains pores with a 10-membered ring structure (5.1 × 5.5 Å and / or 5.3 × 5.6 Å). It has also been proposed to use this zeolite as an adsorbent for volatile organic compounds (hereinafter sometimes abbreviated as "VOCs") such as toluene, xylene, and acetaldehyde contained in exhaust gases emitted from automobiles and factories, and in building materials (see Patent Documents 2 to 4).

[0005] Here, chabazite-type zeolite, which contains pores with an 8-membered ring structure, has a smaller pore diameter than MFI-type zeolite, which contains pores with a 10-membered ring structure, and therefore has a stronger physical adsorption power.In addition, since it has a specific surface area that is approximately twice as large as MFI-type zeolite, it also has a larger adsorption capacity.Therefore, chabazite-type zeolite has the potential to be a VOC adsorbent that is equivalent to or even superior to MFI-type zeolite.

[0006] However, some chabazite-type zeolites exhibit sufficient adsorption properties as VOC adsorbents in dry, low-humidity environments, but have the problem that their VOC adsorption properties can be significantly reduced in high-humidity environments. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Patent No. 6817022 [Patent Document 2] Japanese Patent Application Publication No. 9-253483 [Patent Document 3] WO2017 / 142033 publication [Patent Document 4] Patent No. 3829600 Summary of the Invention [Problem to be solved by the invention]

[0008] In view of the above circumstances, an object of the present invention is to provide a chabazite-type zeolite having excellent VOC adsorption properties, which not only exhibits sufficient VOC adsorption properties in a dry environment but also does not significantly decrease in VOC adsorption properties in a high-humidity environment. Another object of the present invention is to provide a VOC adsorbent containing the chabazite-type zeolite. [Means for solving the problem]

[0009] According to the present invention, there is provided a chabazite-type zeolite characterized in that the ratio (A) / (B) of the BET specific surface area (A) measured by a water vapor adsorption method to the BET specific surface area (B) measured by a nitrogen adsorption method is in the range of 0.40 or less.

[0010] The chabazite-type zeolite of the present invention is (1) The molar ratio of silicon dioxide to aluminum oxide is 50 to 200, and the average particle size is 1.0 μm or more. (2) the ratio (A) / (B) is 0.15 to 0.35; (3) the molar ratio is 55 to 120; (4) The average particle size is 1.5 to 6.0 μm. (5) The difference (D) - (W) between the acetaldehyde adsorption rate (D) in a dry environment and the acetaldehyde adsorption rate (W) in a 75% humidity environment is 18% or less. is preferred.

[0011] The present invention also provides an adsorbent for volatile organic compounds containing the chabazite-type zeolite. [Effects of the Invention]

[0012] As shown in the examples below, the chabazite-type zeolite of the present invention has excellent adsorption properties for acetaldehyde, a type of VOC. Furthermore, chabazite-type zeolite is a porous inorganic material with numerous pores. The VOC adsorption properties of general porous inorganic materials are exhibited due to the large specific surface area of ​​the inorganic material itself. Therefore, it is presumed that the adsorption properties of chabazite-type zeolite are not limited to the adsorption of acetaldehyde alone, but can also exhibit adsorption effects for VOCs. Furthermore, while VOC adsorbents using general chabazite-type zeolites can exhibit sufficient adsorption properties in dry environments, they preferentially adsorb moisture over VOCs in high-humidity environments, such as those with a humidity of 75%, resulting in a significant decrease in VOC adsorption properties. In contrast, the VOC adsorbent containing the chabazite-type zeolite of the present invention not only exhibits sufficient adsorption properties in dry environments, but also has the advantage of not significantly decreasing its adsorption properties even in the above-mentioned high-humidity environments. DETAILED DESCRIPTION OF THE INVENTION

[0013] The adsorbent made of chabazite-type zeolite of the present invention is used to adsorb and remove VOCs. VOCs refer to organic compounds with a boiling point in the range of 50 to 260°C under atmospheric pressure, and examples thereof include acetaldehyde, formaldehyde, ethyl acetate, ethanol, methyl ethyl ketone, dichloroethane, and trichloroethane. Inhaling VOCs is known to cause adverse effects, such as health damage, on the human body.

[0014] <Chabazite-type zeolite> The chabazite-type zeolite of the present invention preferably has a ratio (A / B) of the BET specific surface area (A) measured by a water vapor adsorption method to the BET specific surface area (B) measured by a nitrogen adsorption method in the range of 0.40 or less, and more preferably in the range of 0.35 or less. If the ratio (A / B) is greater than 0.40, the zeolite is highly hydrophilic and preferentially adsorbs water, making it difficult to achieve VOC adsorption performance in a high-humidity environment.

[0015] The chabazite-type zeolite of the present invention preferably has a molar ratio of silicon dioxide to aluminum oxide (SiO2 / Al2O3 molar ratio) of 50 to 200, and more preferably 55 to 120. If the SiO2 / Al2O3 molar ratio is less than 50, the hydrophilicity is high, making it difficult to obtain VOC adsorption performance, and the alkali content increases, reducing heat resistance. If the SiO2 / Al2O3 molar ratio is greater than 200, the reaction time becomes long and it becomes difficult to obtain pure-phase chabazite-type zeolite.

[0016] The chabazite-type zeolite of the present invention preferably has an average particle size of 1.0 μm or more, more preferably 1.5 to 6.0 μm, as evaluated by observing images obtained with a scanning electron microscope (SEM). If the average particle size is less than 1.0 μm, the particles tend to aggregate strongly and fluidity deteriorates, which is likely to reduce workability when processed into an adsorption member. If the average particle size is greater than 6.0 μm, the zeolite may not be uniformly dispersed when blended into a resin composition or when supported on an exhaust rotor.

[0017] The chabazite-type zeolite of the present invention has a crystalline particle morphology in which rhombic faces can be clearly observed. Therefore, the particle size can be evaluated, for example, by measuring the particle sizes of 50 arbitrarily selected crystalline particles in one or more SEM images taken at a magnification of 5000 times.

[0018] In the chabazite-type zeolite of the present invention, the difference (D) - (W) between the acetaldehyde adsorption rate (D) in a dry environment and the acetaldehyde adsorption rate (W) in a 75% humidity environment is preferably 18% or less, and more preferably 15% or less. If the difference (D) - (W) is greater than 18%, the VOC adsorption performance under high humidity is considered to be insufficient. Here, "in a dry environment" means a state in which the sample is dried at 150°C for 2 hours or more, and "in a 75% humidity environment" means a state in which the sample is conditioned in a desiccator adjusted to 75% humidity for 40 hours or more.

[0019] <Production of chabazite-type zeolite> The raw materials for the chabazite-type zeolite described above are basically composed of a silica source, an aluminum source, an alkali source, an organic template, and water. A component that promotes crystallization, such as seed crystals, may also be added. The organic template, also known as an organic structure-directing agent (OSDA), is a component involved in the formation of the zeolite framework, but is used as an optional component that does not necessarily need to be added.

[0020] As the silica source, colloidal silica, amorphous silica, sodium silicate, tetraethyl orthosilicate, aluminosilicate gel, etc. can be used, and as the alumina source, aluminum sulfate, sodium aluminate, aluminum hydroxide, aluminum chloride, aluminosilicate gel, metallic aluminum, etc. can be used, and these are preferably in a form that can be mixed sufficiently uniformly with other components.

[0021] As the alkali source, sodium hydroxide, potassium hydroxide, alkali components in aluminates and silicates, alkali components in aluminosilicate gels, and alkali components in organic templates described below can be used.

[0022] Examples of organic templates that can be used include alkylammonium hydroxides such as trimethyladamantylammonium hydroxide (TMAdaOH), tetramethylammonium hydroxide (TMAOH), tetraethylammonium hydroxide (TEAOH), benzyltrimethylammonium hydroxide (BTMAOH), choline hydroxide (CholineOH), and dimethylpiperidinium hydroxide (DMPOH), and alkylphosphonium hydroxides such as tetramethylphosphonium hydroxide (TMPOH), tetraethylphosphonium hydroxide (TEPOH), and tetrabutylphosphonium hydroxide (TBPOH). These contain an alkaline component and have the dual functions of being both an alkali source and an organic template, and are therefore preferably used as organic templates.

[0023] Chabazite-type zeolite can be produced by reacting and crystallizing a raw material composition consisting of a silica source, an aluminum source, an alkali source, an organic template, and water in a sealed pressure vessel at a temperature of 100 to 200°C for a sufficient period of time. During crystallization, the raw material composition may be left to stand, but it is preferable that the raw material composition be stirred and mixed. After crystallization is complete, the mixture is allowed to cool sufficiently, solid-liquid separated, washed with a sufficient amount of pure water, dried at a temperature of 100 to 150°C, appropriately pulverized, and calcined at a temperature of 400 to 800°C to remove the organic template, thereby obtaining the chabazite-type zeolite according to the present invention.

[0024] If a large amount of alkali source is used as a raw material in the production of the chabazite-type zeolite, the alkali content in the resulting chabazite-type zeolite will be high, and because these alkali components act hydrophilically, the VOC adsorption properties of the resulting chabazite-type zeolite will be significantly impaired. In this case, it is desirable to re-disperse the chabazite-type zeolite that has been subjected to the calcination step in an aqueous solution and remove the alkali components by a dealkalization method using an acid such as hydrochloric acid or sulfuric acid, or by a series of dealkalization methods that involve ion exchange of alkali and ammonium using various ammonium salts, followed by calcination to remove the ammonium.

[0025] The chabazite-type zeolite thus obtained is preferably pulverized into powder for use, and is adjusted to an average particle size of 1.0 μm or more for ease of handling. For example, it can be kneaded into a resin composition or mixed with a liquid containing a hydrophobic solvent, such as a paint or coating agent. It can also be appropriately mixed with a commonly used binder and then molded into granular form for use.

[0026] The VOC adsorbent containing the chabazite-type zeolite of the present invention exhibits high adsorption properties for VOCs such as acetaldehyde and can effectively adsorb and remove these compounds even from atmospheres where VOCs exist at low concentrations. For this reason, such an adsorbent can be filled into a suitable container and installed in front of or behind the fan of an air conditioning unit in a building or vehicle, or can be used in environmental purification equipment used in chemical plants and the like that emit VOC-containing gases, for example, by being supported on an exhaust rotor having a honeycomb structure.

[0027] Furthermore, the VOC adsorbent of the present invention, which has the above characteristics, is blended with a resin to prepare a resin composition. The resulting resin composition is preferably used to prepare a masterbatch, which is then molded into various articles, such as films and various components. In this case, the VOC adsorbent of the present invention can be added to the resin alone or in combination with other adsorbents or additives. There is no limitation on the amount of the VOC adsorbent of the present invention blended; for example, the adsorbent can be blended in an amount of 0.001 to 1,000 parts by mass, preferably 0.005 to 100 parts by mass, per 100 parts by mass of resin. In particular, when the adsorbent of the present invention is applied to a resin for the purpose of reducing the characteristic resin odor that arises due to unreacted monomers or deterioration during resin processing, the amount of the adsorbent is preferably 0.005 to 10 parts by mass per 100 parts by mass of resin.

[0028] Furthermore, by adding the VOC adsorbent of the present invention to resins used in automobile components and housing construction materials, it is expected to have the effect of improving the living environment by adsorbing odors specific to new cars and newly built buildings, particularly substances (aldehydes) that cause sick house syndrome, and by incorporating it into fibers during the fiber processing process, it can also be made into high-performance fibers with deodorizing properties. In such cases, it is preferable that the amount of the adsorbent is 1 to 100 parts by mass per 100 parts by mass of resin.

[0029] Although both thermoplastic resins and thermosetting resins can be used as the base resin, thermoplastic resins are preferred from the viewpoint of moldability. Examples of such thermoplastic resins include the following: Olefin resins such as low-density polyethylene, high-density polyethylene, polypropylene, poly-1-butene, poly-4-methyl-1-pentene, or random or block copolymers of α-olefins such as ethylene, propylene, 1-butene, and 4-methyl-1-pentene, and cyclic olefin copolymers; Ethylene-vinyl copolymers such as ethylene-vinyl acetate copolymer, ethylene-vinyl alcohol copolymer, ethylene-vinyl chloride copolymer; Styrenic resins such as polystyrene, acrylonitrile-styrene copolymer, ABS, α-methylstyrene-styrene copolymer; Vinyl resins such as polyvinyl chloride, polyvinylidene chloride, vinyl chloride-vinylidene chloride copolymer, polymethyl acrylate, polymethyl methacrylate; Polyamide resins such as nylon 6, nylon 6-6, nylon 6-10, nylon 11, and nylon 12; Polyester resins such as polyethylene terephthalate (PET), polybutylene terephthalate, polyethylene naphthalate, and copolymer polyesters thereof; Polycarbonate resin; Polyphenylene oxide resin; biodegradable resins such as polylactic acid; The thermoplastic resins exemplified above can be used alone or in combination of two or more kinds. It can also be used as a blend. In the present invention, olefin resins and polyester resins are particularly suitable. A vinyl resin is most suitable as the base resin.

[0030] Furthermore, because the VOC adsorbent of the present invention has micro-sized pores distributed densely and uniformly, it is expected that the active sites (e.g., solid acid sites) of the chabazite-type zeolite are also distributed densely and uniformly. In other words, the VOC adsorbent of the present invention is not limited in any way to use as a catalyst for which chabazite-type zeolite is generally applied, such as an acid catalyst, a disproportionation catalyst, an isomerization catalyst, a hydrocarbon synthesis catalyst, an FCC catalyst, an olefin polymerization catalyst, and a denitration catalyst, or as a catalyst support. [Example]

[0031] The invention is illustrated by the following examples. In the experiments, various measurements were carried out by the following methods.

[0032] (1) Confirmation of crystal structure by X-ray diffraction (XRD) Measurements were carried out using a Rigaku SmartLab SE with Cu-Kα under the following conditions: When an X-ray diffraction pattern similar to that of U.S. Patent 4,544,538 was obtained, the sample was confirmed to be chabazite-type zeolite and was marked with "O"; when the X-ray diffraction pattern was not obtained, the sample was marked with "X." Measurement range: 3~40° Target: Cu Detector: D / teX Ultra 250 Voltage: 40kV Current: 50mA Step size: 0.01° Counting time: 0.03 sec / step Slit: ISB1 / 2° RS1 open RS2 open

[0033] (2) BET specific surface area (B) measured by nitrogen adsorption Measurements were performed by nitrogen adsorption using a TriStar 3000 manufactured by Micromeritics, and calculations were performed by the BET method. Pretreatment was performed under reduced pressure and evacuation at 150°C for 2 hours.

[0034] (3) BET specific surface area (A) measured by water vapor adsorption Measurements were performed by the water vapor adsorption method using a BELSORP MAX manufactured by Japan BEL Co., Ltd., and calculations were performed using the BET method. Pretreatment was performed under reduced pressure and evacuation at 150°C for 2 hours.

[0035] (4) Composition analysis (SiO2 / Al2O3 molar ratio) For the elemental analysis required to calculate the molar ratio of silicon dioxide to aluminum oxide (SiO2 / Al2O3 molar ratio), measurements were performed using a Rigaku ZSX primus II manufactured by Rigaku Corporation, with a target of Rh, an analytical line of Kα, a tube voltage of 30 kV, a tube current of 100 kV, a detector of PC, and a PET analyzing crystal. The standard sample was dried at 110°C for 2 hours.

[0036] (5) Average particle size (μm) Fifty particles were randomly selected from an image obtained using a scanning electron microscope JSM-6510LA manufactured by JEOL Ltd., and measured by the horizontal Feret method, and the average value of these was taken as the average particle size.

[0037] (6) Acetaldehyde adsorption rate under dry conditions (D) 0.3 g of a sample dried at 150°C for at least 2 hours was placed in a 1.8 L glass bottle, and acetaldehyde was added to the bottle to give an initial concentration of 80 ppm. After 1 hour, the residual gas concentration was measured. The residual gas concentration was measured using a detector tube manufactured by GASTEC. The rate of acetaldehyde reduction at this time was taken as the acetaldehyde adsorption rate (D) in a dry environment.

[0038] (7) Acetaldehyde adsorption rate (W) in a 75% humidity environment A 0.3 g sample that had been conditioned for over 40 hours in a desiccator adjusted to 75% humidity was placed in a 1.8 L glass bottle, and acetaldehyde was added to the bottle to an initial concentration of 80 ppm. After one hour, the residual gas concentration was measured. The residual gas concentration was measured using a detector tube manufactured by GASTEC. The rate of acetaldehyde reduction at this time was taken as the acetaldehyde adsorption rate (W) in a 75% humidity environment.

[0039] Example 1 1.8 kg of 20% trimethyladamantylammonium hydroxide (TMAdaOH) aqueous solution, 0.5 kg of 49% sodium hydroxide aqueous solution, and 0.9 kg of 50% potassium hydroxide aqueous solution were diluted with 1.2 kg of water, and then 1.2 kg of hydrous silicic acid (SiO2: 42%) and 2.5 g of chabazite-type zeolite seeds were added in that order and stirred for 1 hour. 0.4 kg of sodium aluminate aqueous solution was then added and stirred for 30 minutes. The raw material composition was Al2O3:100SiO2:5Na2O:5K2O:20TMAdaOH:2250HO, with the seed content being 0.05% relative to SiO2.

[0040] The reaction solution was placed in a 50 L stainless steel autoclave and subjected to a crystallization reaction at 140°C for 20 hours under stirring. After the crystallization reaction was completed, the reaction solution was filtered under suction and washed three times with warm water in half the volume of the reaction solution. The obtained wet cake was dried at 110°C. The dried product was calcined in a muffle electric furnace at 700°C for 2 hours. X-ray diffraction revealed that the product was pure chabazite-type zeolite with an SiO2 / Al2O3 molar ratio of 58. Fifty crystal particles were randomly selected from an SEM image of this chabazite-type zeolite, and the average particle size calculated based on the particle sizes was 1.5 μm. This chabazite-type zeolite was designated Example 1.

[0041] Example 2 Chabazite-type zeolite was produced in the same manner as in Example 1, except that the raw material composition was Al2O3:180SiO2:9Na2O:9K2O:36TMAdaOH:4050H2O, no seed crystals were added, the reaction vessel was a 100 mL Teflon-lined stainless steel autoclave, and the crystallization reaction was carried out at 140°C for 120 hours. The results are designated as Example 2.

[0042] Example 3 Example 3 was prepared in the same manner as in Example 1, except that the raw material composition was Al2O3:200SiO2:10Na2O:10K2O:40TMAdaOH:4500H2O, the seed crystals were 0.01% relative to SiO2, the reaction vessel was a 100 mL stainless steel autoclave with a Teflon inner tube, and the crystallization reaction was carried out at 140°C for 22 hours.

[0043] (Comparative Example 1) Comparative Example 1 was prepared by producing chabazite-type zeolite in the same manner as in Example 1, except that the raw material composition was Al2O3:40SiO2:2Na2O:2K2O:10TMAdaOH:900H2O, no seed crystals were added, the reaction vessel was a 1.5 L stainless steel autoclave, and the reaction was carried out at 140°C for 48 hours.

[0044] Table 1 shows the results of X-ray diffraction (XRD) measurements for Examples 1 to 3 and Comparative Example 1, the measurement results for the ratio (A) / (B) of the BET specific surface area (A) measured by the water vapor adsorption method to the BET specific surface area (B) measured by the nitrogen adsorption method, the measurement results for the molar ratio of silicon dioxide to aluminum oxide (SiO2 / Al2O3 molar ratio), the measurement results for the average particle size, and the measurement results for the acetaldehyde adsorption rate (W) in a dry environment and an environment with a humidity of 75%, as well as the difference (D)-(W) between the latter and the former.

[0045] [Table 1]

[0046] Table 1 shows that the results of X-ray diffraction measurements indicate that Examples 1 to 3 and Comparative Example 1 are all chabazite-type zeolites.

[0047] Furthermore, in Table 1, the ratio (A) / (B) of the BET specific surface area (A) measured by the water vapor adsorption method to the BET specific surface area (B) measured by the nitrogen adsorption method was 0.22 to 0.28 in Examples 1 to 3, but 0.47 in Comparative Example 1. The molar ratio of silicon dioxide to aluminum oxide (SiO2 / Al2O3 molar ratio) was 58 to 119 in Examples 1 to 3, but 28 in Comparative Example 1. Furthermore, the average particle size was 1.5 to 5.1 in Examples 1 to 3, but 0.9 in Comparative Example 1.

[0048] In Table 1, the acetaldehyde adsorption rates (D) in a dry environment were 93 to 95 for Examples 1 to 3 and 93 for Comparative Example 1, which were almost the same. However, the acetaldehyde adsorption rates (W) in a 75% humidity environment were 79 to 85 for Examples 1 to 3 and 73 for Comparative Example 1, which revealed that the adsorption characteristics of Comparative Example 1 were significantly reduced in a high humidity environment compared to Examples 1 to 3. Here, the difference (D)-(W) between the latter and the former was 9-15% in Examples 1 to 3, but 20% in Comparative Example 1.

Claims

1. A chabazite-type zeolite characterized in that the ratio (A) / (B) of a BET specific surface area (A) measured by a water vapor adsorption method to a BET specific surface area (B) measured by a nitrogen adsorption method is in the range of 0.40 or less.

2. 2. The chabazite-type zeolite according to claim 1, wherein the molar ratio of silicon dioxide to aluminum oxide is 50 to 200, and the average particle size is 1.0 μm or more.

3. 3. The chabazite-type zeolite according to claim 1, wherein the ratio (A) / (B) is 0.15 to 0.

35.

4. The chabazite-type zeolite according to claim 2, wherein the molar ratio is 55 to 120.

5. 3. The chabazite-type zeolite according to claim 2, wherein the average particle size is 1.5 to 6.0 μm.

6. 3. The chabazite-type zeolite according to claim 1, wherein the difference (D) - (W) between the acetaldehyde adsorption rate (D) in a dry environment and the acetaldehyde adsorption rate (W) in a 75% humidity environment is 18% or less.

7. 3. An adsorbent for volatile organic compounds, comprising the chabazite-type zeolite according to claim 1 or 2.

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