Hydrophobic zeolite and method for producing same

Abstract

To provide a hydrophobic zeolite having both of a high hydrophobicity and a high organic compound adsorption ability, which are impossible in conventional zeolite.SOLUTION: A hydrophobic zeolite has a moisture adsorption at 25°C, RH60% of (6 g / zeolite 100 g) or less, and a toluene adsorption at 25°C, 0.01 kPa of (9 g / zeolite 100 g) or more.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a hydrophobic zeolite and a method for producing the same. BACKGROUND OF THE INVENTION The hydrophobic zeolite of the present invention is useful, for example, for selectively adsorbing and removing organic compounds from a mixed gas containing water vapor, or for adsorbing and recovering organic compounds. [Background technology]

[0002] Organic compounds emitted from painting equipment, printing equipment, industrial product cleaning equipment, etc. are considered to be a cause of air pollution such as suspended particulate matter and photochemical oxidants, and there is a demand for a reduction in their emissions. In order to reduce these organic compounds, various organic compound adsorbents have been developed.

[0003] In recent years, adsorbents for organic compounds using zeolites have been proposed, but because zeolites generally have a high water adsorption capacity, the adsorption capacity of volatile organic compounds is relatively low, and a large amount of energy is required to heat and remove the adsorbed organic compounds and water to regenerate the adsorbent. For this reason, there is a demand for zeolites with a low water adsorption capacity, i.e., with high hydrophobicity.

[0004] As a zeolite with relatively high hydrophobicity, Patent Document 1 proposes BEA-type zeolite with an improved SiO2 / Al2O3 molar ratio through acid treatment. However, the zeolite described in Patent Document 1 has a water adsorption capacity of about 1.0 to 5.0% at P / P0 = 0.1, which corresponds to a relative humidity of 10%, and acid treatment alone is not enough to achieve sufficient hydrophobicity for use as an adsorbent for organic compounds.

[0005] Furthermore, Patent Document 2 proposes a hydrocarbon adsorbent made of BEA-type zeolite having an SiO2 / Al2O3 molar ratio of 300 or more. The hydrocarbon adsorbent described in Patent Document 2 has a high desorption temperature for hydrocarbons adsorbed on the zeolite, and is therefore insufficient as an adsorbent for organic compounds that are required to desorb adsorbates at low temperatures. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent No. 3429011 [Patent Document 2] Patent Publication No. 2008-080195 Summary of the Invention [Problem to be solved by the invention]

[0007] An object of the present invention is to provide a hydrophobic zeolite that combines high hydrophobicity with high organic compound adsorption capacity, which has not been achieved with conventional zeolites. [Means for solving the problem]

[0008] As a result of extensive research into solving the above problems, the present inventors have found that a specific hydrophobic zeolite can solve the above problems, and have thus completed the present invention.

[0009] That is, the present invention relates to a hydrophobic zeolite having a water adsorption amount of 6 g / 100 g of zeolite or less at 25° C. and a relative humidity (hereinafter also referred to as “RH”) of 60% and a toluene adsorption amount of 9 g / 100 g of zeolite or more at 25° C. and 0.01 kPa. Note that the hydrophobic zeolite is preferably produced without using a fluorine compound, as it has both high hydrophobicity and high organic compound adsorption capacity.

[0010] The present invention will be described in detail below.

[0011] The present invention relates to a hydrophobic zeolite having a water adsorption amount of 6 g / 100 g of zeolite or less at 25° C. and 60% RH, and a toluene adsorption amount of 9 g / 100 g of zeolite or more at 25° C. and 0.01 kPa.

[0012] In the present invention, the water adsorption amount is the equilibrium water adsorption amount at a temperature of 25°C and an equilibrium pressure of P / P0 = 0.6 and P = 1.90 kPa (RH 60%), converted into a mass per 100 g of zeolite, and the toluene adsorption amount is the equilibrium water adsorption amount at a temperature of 25°C and an equilibrium pressure of P = 0.01 kPa, converted into a mass per 100 g of zeolite. A zeolite with a lower water adsorption amount can be evaluated as having "higher hydrophobicity," while a zeolite with a higher toluene adsorption amount can be evaluated as having "higher organic compound adsorption capacity." The present invention is characterized by having a water adsorption amount of 6 g / 100 g of zeolite or less at 25°C and RH 60% and a toluene adsorption amount of 9 g / 100 g of zeolite or more at 25°C and 0.01 kPa, thereby combining high hydrophobicity with high organic compound adsorption capacity. Furthermore, the water adsorption amount at 25°C and 60% RH is preferably 5g / 100g zeolite or less, more preferably 4g / 100g zeolite or less. There is no lower limit to the water adsorption amount, but the lower the limit, the better. The toluene adsorption amount at 25°C and 0.01 kPa is preferably 10g / 100g zeolite or more, more preferably 10.5g / 100g zeolite or more. There is no upper limit to the toluene adsorption amount, but the higher the limit, the better.

[0013] The hydrophobic zeolite of the present invention preferably has a water adsorption amount of 1 g / 100 g of zeolite or less, more preferably 0.5 g / 100 g of zeolite or less, at 25° C. and 10% RH. There is no lower limit to the water adsorption amount, but the lower the amount, the better.

[0014] The hydrophobic zeolite of the present invention may have, for example, a BEA structure, an MEI structure, or an MSE structure, and preferably has a BEA structure because it has a high organic compound adsorption capacity. Here, the BEA structure, the MEI structure, and the MSE structure are defined by the International Zeolite Association as " * It refers to the zeolite framework structure classified into "BEA," "MEI," and "MSE."

[0015] The hydrophobic zeolite of the present invention is1 The amount of hydroxyl groups calculated from the sum of the integrals of the peaks at chemical shifts of 1.8 ppm and 2.2 ppm in H MAS NMR is 3 × 10 20 It is preferable that the number is not more than 1 / g and that there is no peak around 0.7 ppm.

[0016] 1 H MAS NMR measurements were performed using a Varian solid-state NMR VNMRS-400 nuclear magnetic resonance spectrometer, rotating the sample tube at a rotation speed of 15 kHz. Chemical shifts were measured using tetramethylsilane as the chemical shift reference (0 ppm). Hydroxy groups were quantified using a calibration curve of hydrogen content prepared using benzene in deuterated dimethyl sulfoxide. Measurements were performed using samples that had been dehydrated by evacuating to a vacuum at 400°C for 5 hours.

[0017] The hydrophobic zeolite of the present invention 1 Due to its high hydrophobicity, the H MAS NMR spectrum is characterized by a main peak at a chemical shift of approximately 1.8 ppm and a shoulder peak at approximately 2.2 ppm. 1 The amount of hydroxyl groups calculated from the sum of the integrals of the peaks at chemical shifts of 1.8 ppm and 2.2 ppm in the quantitative H MAS NMR data is 3 × 10 20 It is preferable that the number of particles is less than 2.5 × 10 20 It is more preferable that the number of particles is not more than 1 / g. It is also preferable that the number of particles is not more than 1 / g. It is also preferable that the number of particles is not more than 1 / g.

[0018] The hydrophobic zeolite of the present invention preferably has an SiO2 / Al2O3 molar ratio in the range of 100-500, more preferably 300-480, from the viewpoint of achieving both high hydrophobicity and high crystallinity.

[0019] The hydrophobic zeolite of the present invention preferably has a crystal size of 0.02 μm to 2.0 μm, more preferably 0.03 μm to 1.0 μm. If the crystal size is 0.02 μm or more, the zeolite can have properties that make it easier to handle during molding or honeycomb coating, and if the crystal size is 2.0 μm or less, it is possible to suppress a decrease in adsorption performance due to poor intracrystalline diffusion of the adsorbate.

[0020] The hydrophobic zeolite of the present invention may contain one or more metals selected from the group consisting of sodium, potassium, cesium, iron, copper, silver, platinum, ruthenium, rhodium, palladium, and iridium, from the viewpoints of achieving higher adsorption selectivity and heat resistance when used as an adsorbent for organic compounds, and of imparting functions such as oxidative decomposition of adsorbed organic compounds.

[0021] The method for incorporating the metal component is not particularly limited, and ion exchange, impregnation, evaporation to dryness, etc. can be used. Examples of ion exchange methods include contacting zeolite with a solution containing desired ions until the amount of ions in the zeolite reaches the desired concentration. Common ion exchange methods, such as batch methods and flow methods, can be applied. When manufacturing an organic compound adsorbent in the form of a molded body or honeycomb structure, it is possible to either metal-modify zeolite powder and then form it into a molded body or honeycomb structure, or to metal-modify zeolite powder and then form it into a molded body or honeycomb structure.

[0022] Next, the method for producing the hydrophobic zeolite of the present invention will be described.

[0023] The production method is not particularly limited as long as it can produce the hydrophobic zeolite of the present invention, but an example of such a production method is to contact the zeolite with an acidic solution and then with water vapor at a temperature of 600°C to 900°C.

[0024] In the present invention, the term "acidic solution" refers to a solution having a pH of 3 or less, and more preferably a solution having a pH of 2 or less.

[0025] As the zeolite used as the base material, a synthetic zeolite having a BEA structure, which can be obtained without using fluorine during production, can be suitably used.

[0026] A method for producing a synthetic zeolite having the BEA structure includes, for example, hydrothermal crystallization of a mixture of a silica source, an alumina source, an alkali source, and, if necessary, a structure-directing agent (hereinafter also referred to as a "raw material mixture").

[0027] Examples of silica sources that can be used include colloidal silica, amorphous silica, sodium silicate, tetraethyl orthosilicate, and aluminosilicate gel.

[0028] Examples of the alumina source that can be used include aluminum sulfate, sodium aluminate, aluminum hydroxide, aluminum chloride, aluminosilicate gel, metallic aluminum, etc. The silica source and alumina source are preferably in a form that can be mixed sufficiently uniformly with other raw materials.

[0029] Examples of alkali sources that can be used include various salts such as hydroxides, halides, sulfates, nitrates, and carbonates of sodium, potassium, and ammonium, and alkali components in aluminates, silicates, and aluminosilicate gels.

[0030] A structure-directing agent such as tetraethylammonium hydroxide or tetraethylammonium bromide may also be used as needed.

[0031] Zeolite can be crystallized using an autoclave, and the crystallization temperature can be 100°C or higher and 250°C or lower, preferably 110°C or higher and 200°C or lower, and more preferably 120°C or higher and 190°C or lower. The crystallization time can be 12 hours or higher and 96 hours or lower, preferably 14 hours or higher and 84 hours or lower, and more preferably 16 hours or higher and 72 hours or lower. Crystallization can be carried out either by leaving the mixture to stand or with stirring.

[0032] After the crystallization is complete, solid-liquid separation is performed, and the excess alkaline solution can be washed with pure water, warm water, or the like. After washing, the product can be dried. The drying temperature is 80°C or higher and 200°C or lower, preferably 90°C or higher and 190°C or lower. If a structure-directing agent is included, it can be removed by thermal decomposition treatment after drying.

[0033] After removing the structure-directing agent used in the production of the zeolite, the BEA structure zeolite can be suitably dealuminated by contacting the zeolite with an acidic solution.

[0034] The acid used in the acidic solution may be any of inorganic acids, organic acids, and mixtures thereof, but inorganic acids such as hydrochloric acid, sulfuric acid, and nitric acid are preferred.

[0035] The amount of acid in the acidic solution is preferably 10 to 100 times equivalent to the amount of aluminum in the zeolite, and more preferably 20 to 80 times equivalent.

[0036] When contacting with the acidic solution, the solution is preferably heated to 40°C to 95°C, more preferably 50°C to 95°C, in order to promote dealumination.

[0037] The dealumination using an acidic solution may be carried out once or may be repeated two or more times until the desired SiO2 / Al2O3 molar ratio is achieved, which can be, for example, 100 to 500, preferably 300 to 480.

[0038] The hydrophobic zeolite of the present invention can be produced by contacting a dealuminated zeolite obtained by dealumination with steam of preferably 20 to 100% by volume, more preferably 40 to 100% by volume, at a temperature of 600 to 900°C, more preferably 700 to 850°C. When the steam concentration is 20 to 100% by volume, better hydrophobicity can be exhibited. Furthermore, when the contact temperature is 600 to 900°C, better hydrophobicity and a higher crystallinity can be exhibited.

[0039] The organic compound adsorbent containing the hydrophobic zeolite of the present invention is particularly effective as an adsorbent for volatile organic compounds. The adsorbent can adsorb and remove or recover organic compounds in a humid atmosphere or in water while reducing the influence of moisture. Therefore, the adsorbent is useful as a method for removing organic compounds by contacting a fluid containing at least one organic compound with the fluid to remove the organic compound. For example, the adsorbent can be used to adsorb and remove / recover organic compounds in exhaust gases or wastewater discharged from painting equipment, printing equipment, industrial product cleaning equipment, etc., or as an adsorbent for adsorbing and removing organic hydrocarbon components in automobile exhaust gases.

[0040] The hydrophobic zeolite of the present invention can be used as an organic compound adsorbent in the powder state as produced, but it can also be used as a molded body formed into a desired shape such as beads, pellets, or a trefoil shape, or it can be used as a honeycomb structure in which the hydrophobic zeolite powder of the present invention is made into a slurry and applied to a honeycomb-shaped substrate.

[0041] When used as an adsorbent for organic compounds, the hydrophobic zeolite of the present invention can be mixed with other zeolites, for example, zeolites with an FAU structure such as USY, or zeolites with an MFI structure such as ZSM-5. [Effects of the Invention]

[0042] It is possible to provide a hydrophobic zeolite that combines high hydrophobicity and high organic compound adsorption capacity, which has not been achieved with conventional zeolites. [Brief explanation of the drawings]

[0043] [Figure 1] Water adsorption isotherms at 25°C for Examples, Comparative Examples, and Reference Examples [Figure 2] Adsorption isotherms of toluene at 25°C for Examples, Comparative Examples, and Reference Examples [Figure 3] H MAS NMR spectra of Examples and Comparative Examples [Figure 4] 1H MAS NMR spectra of Examples and Comparative Examples (Y axis of FIG. 3 is enlarged 5 times) [Example]

[0044] The present invention will be explained in more detail below with reference to examples, but the present invention is not limited to these examples.

[0045] <Measurement of water adsorption amount and toluene adsorption amount> The adsorption amount was measured using a constant-volume adsorption measuring device (BELSORP MAXII, manufactured by Microtrack Bel). The sample was pretreated at 350°C for 2 hours under a vacuum of 10 Pa or less. The adsorption temperature was 25°C.

[0046] < 1 H MAS NMR Measurement 1 H MAS NMR measurements were performed using a Varian solid-state NMR VNMRS-400 nuclear magnetic resonance spectrometer, rotating the sample tube at a rotation speed of 15 kHz. Chemical shifts were measured using tetramethylsilane as the chemical shift reference (0 ppm). Hydroxy groups were quantified using a calibration curve of hydrogen content prepared using benzene in deuterated dimethyl sulfoxide. Measurements were performed using samples that had been dehydrated by evacuating to a vacuum at 400°C for 5 hours.

[0047] Example 1 10 g of commercially available proton-type BEA-type zeolite (HSZ-940HOA: manufactured by Tosoh Corporation, SiO2 / Al2O3 molar ratio 40) was added to 100 g of 2N hydrochloric acid and stirred at 70°C for 2 hours. After that, the solid-liquid separation was performed, followed by washing with 2 L of warm pure water and drying overnight at 110°C. ICP emission spectrometry showed that the resulting dealuminated zeolite had a SiO2 / Al2O3 molar ratio of 480.

[0048] This dealuminated zeolite was heat-treated (contacted with water vapor) for 2 hours at 840°C in an 80% by volume water vapor atmosphere to obtain the hydrophobic zeolite of the present invention. The SiO2 / Al2O3 molar ratio was 480. The water adsorption amount and toluene adsorption amount at 25°C are shown in Figures 1 and 2 and Table 1, respectively.

[0049] Regarding the hydrophobic zeolite of the present invention obtained in Example 1, 1 The H MAS NMR spectrum was measured. The results are shown in Figure 3. The spectral intensity (Y axis) of this figure is magnified five times and shown in Figure 4. The amount of hydroxyl groups calculated from the sum of the integrated values ​​of the peaks at chemical shifts around 0.7 ppm, 1.8 ppm, and 2.2 ppm is shown in Table 2.

[0050] As is clear from Fig. 3, the hydrophobic zeolite of the present invention obtained in Example 1 had a main peak at a chemical shift of approximately 1.8 ppm and a shoulder peak at a chemical shift of approximately 2.2 ppm. Also, as is clear from Fig. 4, the hydrophobic zeolite of the present invention obtained in Example 1 did not have a peak at any of the chemical shifts of approximately 0.7 ppm, 4 ppm, or 5 ppm.

[0051] Example 2 The dealuminated zeolite obtained in Example 1 before steam treatment was heat-treated (contacted with steam) for 2 hours at 740°C in a 60% by volume steam atmosphere to obtain a hydrophobic zeolite of the present invention. The SiO2 / Al2O3 molar ratio was 480. The water adsorption amount and toluene adsorption amount at 25°C are shown in Figures 1 and 2 and Table 1, respectively.

[0052] Regarding the hydrophobic zeolite of the present invention obtained in Example 2, 1 The H MAS NMR spectrum was measured. The results are shown in Figure 3. The spectral intensity (Y axis) of this figure is magnified five times and shown in Figure 4. The amount of hydroxyl groups calculated from the sum of the integrated values ​​of the peaks at chemical shifts around 0.7 ppm, 1.8 ppm, and 2.2 ppm is shown in Table 2.

[0053] As is clear from Fig. 3, the hydrophobic zeolite of the present invention obtained in Example 2 had a main peak at a chemical shift of approximately 1.8 ppm and a shoulder peak at a chemical shift of approximately 2.2 ppm. Also, as is clear from Fig. 4, the hydrophobic zeolite of the present invention obtained in Example 2 had no peaks at any of the chemical shifts of approximately 0.7 ppm, 4 ppm, or 5 ppm.

[0054] Comparative Example 1 The dealuminated zeolite with a SiO2 / Al2O3 molar ratio of 480 obtained in Example 1 before steam treatment was measured for water adsorption and toluene adsorption at 25°C without steam treatment, and the results are shown in Figures 1 and 2 and Table 1, respectively.

[0055] Regarding the dealuminated zeolite with an SiO / AlO molar ratio of 480 obtained in Example 1 above before steam treatment, 1 The H MAS NMR spectrum was measured. The results are shown in Figure 3. The spectral intensity (Y axis) of this figure is magnified five times and shown in Figure 4. The amount of hydroxyl groups calculated from the sum of the integrated values ​​of the peaks at chemical shifts around 0.7 ppm, 1.8 ppm, and 2.2 ppm is shown in Table 2.

[0056] As is clear from Fig. 3, the dealuminated zeolite before steam treatment, having an SiO2 / Al2O3 molar ratio of 480 obtained in Example 1, had a main peak at a chemical shift of approximately 2.2 ppm and a shoulder peak at a chemical shift of approximately 1.8 ppm. Also, as is clear from Fig. 4, the dealuminated zeolite before steam treatment did not have a peak at a chemical shift of approximately 0.7 ppm, but had a peak at approximately 4 ppm to 5 ppm.

[0057] Comparative Example 2 The water adsorption amount and toluene adsorption amount of a commercially available USY-type hydrophobic zeolite (manufactured by Tosoh Corporation, SiO2 / Al2O3 molar ratio 115) at 25°C were measured, and the results are shown in Figures 1 and 2 and Table 1, respectively.

[0058] Comparative Example 3 The water adsorption amount and toluene adsorption amount of a commercially available MFI-type hydrophobic zeolite (manufactured by Tosoh Corporation, SiO2 / Al2O3 molar ratio 1880) at 25°C were measured, and the results are shown in Figures 1 and 2 and Table 1, respectively.

[0059] Comparative Example 4 Regarding the commercially available proton type BEA zeolite used as a raw material in Example 1, 1 The H MAS NMR spectrum was measured. The results are shown in Figure 3. The spectral intensity of this figure is magnified five times and shown in Figure 4. The amount of hydroxyl groups calculated from the sum of the integrated values ​​of the peaks at chemical shifts around 0.7 ppm, 1.8 ppm, and 2.2 ppm is shown in Table 2.

[0060] As is clear from Figure 3, the commercially available proton-type BEA zeolite had a main peak at a chemical shift of approximately 2.2 ppm and a shoulder peak at a chemical shift of approximately 1.8 ppm. Also, as is clear from Figure 4, the commercially available proton-type BEA zeolite had peaks at chemical shifts of approximately 0.7 ppm, 4 ppm, and 5 ppm.

[0061] Reference example 1 According to Example 2 of JP 2008-080195 A, zeolite with an increased SiO2 / Al2O3 molar ratio was heat-treated (contacted with water vapor) at 850°C in a 10% by volume water vapor atmosphere for 1 hour to obtain BEA-type zeolite of Reference Example 1. The SiO2 / Al2O3 molar ratio was 530. The water adsorption amount and toluene adsorption amount at 25°C are shown in Figures 1 and 2 and Table 1, respectively.

[0062] [Table 1]

[0063] As is clear from FIGS. 1 and 2 and Table 1, the hydrophobic zeolite of the present invention has both high hydrophobicity and high organic compound adsorption performance.

[0064] As described above, for organic compound adsorbents, zeolites with low water adsorption capacity, i.e., high hydrophobicity, are required in order to increase the adsorption capacity of volatile organic compounds and to improve the regeneration efficiency of the adsorbent. The zeolite of the present invention has high hydrophobicity not found in conventional products, making it possible to provide an extremely effective adsorbent.

[0065] [Table 2]

Claims

1. It has a BEA structure and SiO ２ / Al ２ O ３ The molar ratio is 300 to 480, １ The amount of hydroxy groups calculated from the sum of the integral values ​​of the peaks at chemical shifts of about 1.8 ppm and 2.2 ppm in H MAS NMR was 3 × 10 ２０ 1. A hydrophobic zeolite characterized in that it has a particle size of 1000 or less per 1000 particles / g and does not have a peak near 0.7 ppm.

2. 2. The hydrophobic zeolite according to claim 1, characterized in that the crystal size is 0.02 to 2.0 μm.

3. 3. The hydrophobic zeolite according to claim 1, wherein the amount of water adsorbed at 25° C. and RH 60% is 5 g / 100 g of zeolite or less.

4. The hydrophobic zeolite according to any one of claims 1 to 3, which has a toluene adsorption amount of 10 g / 100 g of zeolite or more at 25°C and 0.01 kPa.

5. １ The hydrophobic zeolite according to any one of claims 1 to 4, characterized in that it does not have a peak at a chemical shift of about 0.7 ppm in H MAS NMR, and further does not have peaks at about 4 ppm and about 5 ppm.

6. The method for producing a hydrophobic zeolite according to any one of claims 1 to 5, characterized in that the zeolite is brought into contact with the acidic solution and then brought into contact with steam at a temperature of 700 to 850°C.

7. An adsorbent for organic compounds, comprising the hydrophobic zeolite according to any one of claims 1 to 6.

8. A method for removing organic compounds, comprising contacting the adsorbent for organic compounds according to claim 7 with a fluid containing at least one organic compound to remove said organic compound from the fluid.

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