Hydrophobic zeolite and method for producing the same

Abstract

To provide a hydrophobic zeolite having both high hydrophobicity and high organic compound adsorption capacity and capable of selectively adsorbing an organic compound, which is not obtained by conventional zeolite.SOLUTION: A hydrophobic zeolite has a water adsorption amount of (4.5 g / zeolite 100 g) or less at 25°C and RH70%, and a toluene adsorption amount of (15 g / zeolite 100 g) or more at 25°C and 0.1 kPa.SELECTED DRAWING: Figure 1

Description

Technical Field

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

Background Art

[0002] Organic compounds discharged from painting equipment, printing equipment, industrial product cleaning equipment, etc. are considered to cause air pollution such as suspended particulate matter and photochemical oxidants, and reduction of the discharge amount is demanded. And, various organic compound adsorbents have been developed for reducing the organic compounds.

[0003] In recent years, organic compound adsorbents using zeolite have been proposed. However, since zeolite generally has a large amount of water adsorption, the adsorption amount of volatile organic compounds is relatively reduced, or a large amount of energy is required when the adsorbed organic compounds and water are removed by heating to regenerate the adsorbent. For this reason, a zeolite having a small amount of water adsorption, that is, a highly hydrophobic zeolite, is demanded.

[0004] As a zeolite having a relatively high hydrophobicity, in Patent Document 1, an FAU-type zeolite having a water adsorption amount of 18% by mass or less at a water vapor pressure of 2 kPa corresponding to a relative humidity of 63% has been proposed. However, the zeolite described in Patent Document 1 has a water adsorption amount of about 5.5% by mass at a relative humidity of 63%, and sufficient hydrophobicity as an organic compound adsorbent could not be obtained.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] The present invention aims to provide a hydrophobic zeolite that possesses both high hydrophobicity and high organic compound adsorption capacity, which could not be obtained with conventional zeolites, and that is capable of selectively adsorbing organic compounds. [Means for solving the problem]

[0007] As a result of diligent research to solve the above problems, the inventors of this invention discovered that a specific hydrophobic zeolite can solve the above problems, and thus completed the present invention.

[0008] In other words, the present invention is a hydrophobic zeolite having a water adsorption capacity of (4.5 g / 100 g of zeolite) or less at 25°C and 70% relative humidity (hereinafter also referred to as "RH"), and a toluene adsorption capacity of (15 g / 100 g of zeolite) or more at 25°C and 0.1 kPa.

[0009] The present invention will be described in detail below.

[0010] The present invention relates to a hydrophobic zeolite having a water adsorption capacity of (4.5 g / 100 g of zeolite) or less at 25°C and RH 70%, and a toluene adsorption capacity of (15 g / 100 g of zeolite) or more at 25°C and 0.1 kPa.

[0011] In this invention, the amount of water adsorbed is calculated by converting the equilibrium adsorbed amount of water at a temperature of 25°C, an equilibrium pressure of P / P0 = 0.7, and P = 2.22 kPa (RH 70%) to the mass per 100 g of zeolite, and the amount of toluene adsorbed is calculated by converting the equilibrium adsorbed amount at a temperature of 25°C and an equilibrium pressure of P = 0.1 kPa to the mass per 100 g of zeolite. Materials with a lower amount of water adsorbed can be evaluated as having "high hydrophobicity," and materials with a higher amount of toluene adsorbed can be evaluated as having "high organic compound adsorption capacity." Furthermore, this invention is characterized by having a water adsorbed amount of (4.5 g / 100 g of zeolite) or less at 25°C and RH 70%, and a toluene adsorbed amount of (15 g / 100 g of zeolite) or more at 25°C and 0.1 kPa, thereby possessing both high hydrophobicity and high organic compound adsorption capacity, and selectively adsorbing organic compounds. The amount of water adsorbed at 25°C and RH 70% is preferably (4g / 100g of zeolite) or less, and more preferably (3.5g / 100g of zeolite) or less. The lower limit of this water adsorbed amount is not limited, but a lower amount is preferred. The amount of toluene adsorbed at 25°C and 0.1kPa is preferably (15.5g / 100g of zeolite) or more, and more preferably (16g / 100g of zeolite) or more. The upper limit of this toluene adsorbed amount is not limited, but a higher amount is preferred.

[0012] The hydrophobic zeolite of the present invention preferably has a water adsorption capacity of (1 g / 100 g of zeolite) or less at 25°C and RH20%, and more preferably (0.8 g / 100 g of zeolite) or less. The lower limit of this water adsorption capacity is not limited, but a lower value is preferable.

[0013] The hydrophobic zeolite of the present invention preferably has an FAU structure because it has a high organic compound adsorption capacity. Here, the FAU structure refers to the zeolite skeleton structure classified by the International Zeolite Association.

[0014] The hydrophobic zeolite of the present invention preferably has an SiO2 / Al2O3 molar ratio in the range of 50 to 150, and more preferably 80 to 130, from the viewpoint of achieving both high hydrophobicity and high crystallinity.

[0015] The hydrophobic zeolite of the present invention preferably has an aggregated particle diameter of 1 to 5 μm, and more preferably 1 to 3 μm, in order to obtain physical properties that make it easier to handle when molding or honeycomb coating. Here, the "aggregated particle diameter" in the present invention refers to the particle diameter corresponding to a cumulative volume distribution of 50% in particle size distribution measurement (volume distribution) by laser diffraction scattering method (hereinafter, the aggregated particle diameter is also referred to as "D50").

[0016] 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 viewpoint of higher adsorption selectivity and heat resistance when used as an adsorbent for organic compounds, as well as from the viewpoint of imparting functions such as oxidative decomposition of adsorbed organic compounds.

[0017] The method for incorporating metal components is not particularly limited, and methods such as ion exchange, impregnation, and evaporation to dryness can be used. An example of an ion exchange method is to bring zeolite into contact with a solution containing the desired ions until the amount of ions in the zeolite reaches the desired concentration. General ion exchange methods such as batch and flow methods are applicable. When manufacturing organic compound adsorbents in molded or honeycomb structures, it is possible to either metal-modify the zeolite powder before forming the molded or honeycomb structure, or to metal-modify the zeolite powder after forming the molded or honeycomb structure.

[0018] Next, the method for producing the hydrophobic zeolite of the present invention will be described.

[0019] The manufacturing method is not particularly limited as long as it can produce the hydrophobic zeolite of the present invention, but one example is a manufacturing method in which the zeolite is brought into contact with an acidic solution and then brought into contact with water vapor at a temperature of 600°C to 900°C.

[0020] Here, in the present invention, the "acidic solution" refers to a solution having a pH of 5 or less, more preferably a solution having a pH of 2 or less, and even more preferably a solution having a pH of 1 or less.

[0021] As the zeolite serving as the base material, synthetic zeolite having a FAU structure can be preferably used, and Y-type zeolite is preferred.

[0022] Examples of the method for producing the synthetic zeolite having the FAU structure include crystallizing a mixture of a silica source, an alumina source, and an alkali source (hereinafter also referred to as "raw material mixture") under hydrothermal conditions.

[0023] As the silica source, for example, colloidal silica, amorphous silica, sodium silicate, tetraethyl orthosilicate, aluminosilicate gel, or the like can be used.

[0024] As the alumina source, for example, aluminum sulfate, sodium aluminate, aluminum hydroxide, aluminum chloride, aluminosilicate gel, metallic aluminum, or the like can be used. The silica source and the alumina source are preferably in a form that can be sufficiently uniformly mixed with other raw materials.

[0025] As the alkali source, for example, hydroxides, halides, sulfates, nitrates, carbonates, and other various salts of sodium, potassium, and ammonium, alkali components in aluminate, silicate, and aluminosilicate gel, or the like can be used.

[0026] For the crystallization of zeolite, an autoclave can be used, and the crystallization temperature can be 70°C or higher and 250°C or lower, preferably 80°C or higher and 200°C or lower, and more preferably 90°C or higher and 190°C or lower. The crystallization time can be 12 hours or longer and 96 hours or shorter, preferably 14 hours or longer and 84 hours or shorter, and more preferably 16 hours or longer and 72 hours or shorter. The crystallization can be carried out either statically or with stirring.

[0027] After the crystallization is completed, solid-liquid separation can be performed, and the excess alkaline solution can be washed with an acidic solution, pure water, warm water, or the like. After washing, it can be dried. The drying temperature may be 80°C or higher and 200°C or lower, preferably 90°C or higher and 190°C or lower.

[0028] By contacting the zeolite with an acidic solution, the FAU structure zeolite can be suitably dealuminated.

[0029] In addition, as a method for producing the hydrophobic zeolite of the present invention, there is also a production method in which dealuminated zeolite obtained by contacting zeolite with an acidic solution is contacted with water vapor at a temperature of 600°C to 900°C. At this time, as the dealuminated zeolite, commercially available dealuminated zeolite can also be used.

[0030] As the acid used in the acidic solution, an inorganic acid, an organic acid, or a mixture thereof may be used, but hydrochloric acid, sulfuric acid, or nitric acid, which is an inorganic acid, is preferable.

[0031] The amount of the acid in the acidic solution is preferably 1 to 100 times the equivalent amount of aluminum in the zeolite, and more preferably 1 to 80 times the equivalent amount.

[0032] In addition, when contacting with the acidic solution, it is preferably heated to 40°C to 95°C, and more preferably heated to 50°C to 95°C, in order to promote dealumination.

[0033] The dealumination with the acidic solution may be performed once, or may be repeated two or more times until the desired SiO2 / Al2O3 molar ratio is obtained. By this dealumination, the SiO2 / Al2O3 molar ratio can be, for example, 50 to 150, preferably 80 to 130.

[0034] The hydrophobic zeolite of the present invention can be produced by contacting a dealumininated zeolite, obtained by dealuminulation, with water vapor preferably at a concentration of 20% to 100% by volume, more preferably 40% to 100% by volume, at a temperature of 600°C to 900°C, more preferably 700 to 850°C. When the water vapor concentration is 20% to 100% by volume, superior hydrophobicity can be achieved. Furthermore, when the contact temperature is 600°C to 900°C, superior hydrophobicity and higher crystallinity can be achieved. Contact with water vapor at this temperature may be performed only once, or it may be repeated two or more times until the hydrophobic zeolite of the present invention achieves the desired hydrophobicity.

[0035] The hydrophobic zeolite-containing organic compound adsorbent of the present invention exhibits particularly excellent effects as a volatile organic compound adsorbent. This organic compound adsorbent makes it possible to adsorb and remove or recover organic compounds in a humid atmosphere or water while reducing the influence of moisture. Therefore, this organic compound adsorbent is useful as a method for removing organic compounds by contacting a fluid containing at least one organic compound and removing the organic compound from the fluid. For example, it can be useful as an adsorbent used for adsorbing and removing / recovering organic compounds in exhaust gas 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 gas.

[0036] The hydrophobic zeolite of the present invention can be used as an organic compound adsorbent in its as-manufactured powder form, but it can also be used as a molded body formed into desired shapes such as beads, pellets, or trefoils, or as a honeycomb structure by slurrying the hydrophobic zeolite powder of the present invention and coating it onto a honeycomb substrate.

[0037] The hydrophobic zeolite of the present invention can be used in combination with other zeolites, such as MFI structure zeolites like ZSM-5, when used as an organic compound adsorbent. [Effects of the Invention]

[0038] This invention provides a hydrophobic zeolite that possesses both high hydrophobicity and high organic compound adsorption capacity, which were not achievable with conventional zeolites, and that can selectively adsorb organic compounds. [Brief explanation of the drawing]

[0039] [Figure 1] Water adsorption isotherms at 25°C for the examples and comparative examples. [Figure 2] Adsorption isotherms of toluene at 25°C for the examples and comparative examples. [Examples]

[0040] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0041] <Measurement of water adsorption and toluene adsorption> Adsorption amounts were measured using a constant-volume adsorption analyzer (BELSORP MAXII: Microtrac-BEL). Samples were pre-treated at 350°C for 2 hours under a vacuum of 10 Pa or less. The adsorption temperature was measured at 25°C.

[0042] <Measurement of aggregated particle size distribution> Particle size distribution was measured using a laser diffraction / scattering particle size distribution analyzer (Microtrac MT3000II: Microtrac Bell). The sample slurry was dispersed for 2 minutes using an ultrasonic homogenizer (Nippon Seiki Seisakusho Co., Ltd.) before measurement.

[0043] reference Example 1 The hydrophobic zeolite of the present invention was obtained by contacting commercially available Y-type zeolite (manufactured by Tosoh, SiO2 / Al2O3 molar ratio 6.1, Na2O content 0.24 mass%) with concentrated hydrochloric acid (pH 1 or less) to obtain dealumininated USY-type zeolite (SiO2 / Al2O3 molar ratio 104), and then heat-treating it at 780°C in a 70% by volume water vapor atmosphere for 2 hours (contact with water vapor). The SiO2 / Al2O3 molar ratio was 104. The amount of water adsorbed and toluene adsorbed at 25°C was measured, and the results are shown in Figures 1 and 2, and Table 1, respectively.

[0044] reference Example 2 The hydrophobic zeolite of the present invention was obtained by heat-treating a commercially available dealumininated USY-type hydrophobic zeolite (manufactured by Tosoh, SiO2 / Al2O3 molar ratio 115, zeolite obtained by contacting Y-type zeolite with concentrated hydrochloric acid (pH 1 or less)) at 710°C for 2 hours in a 70% by volume water vapor atmosphere (contact with water vapor). The SiO2 / Al2O3 molar ratio was 115, and the D50 was 2.2 μm. In addition, the amount of water adsorbed and toluene adsorbed at 25°C was measured, and the results are shown in Figures 1 and 2, and Table 1, respectively.

[0045] reference Example 3 The hydrophobic zeolite of the present invention was obtained by heat-treating a commercially available dealumininated USY-type hydrophobic zeolite (manufactured by Tosoh, SiO2 / Al2O3 molar ratio 115, zeolite obtained by contacting Y-type zeolite with concentrated hydrochloric acid (pH 1 or less)) at 750°C for 2 hours in a 70% by volume water vapor atmosphere (contact with water vapor). The SiO2 / Al2O3 molar ratio was 115, and the D50 was 2.3 μm. In addition, the amount of water adsorbed and toluene adsorbed at 25°C was measured, and the results are shown in Figures 1 and 2, and Table 1, respectively.

[0046] Example 4 The hydrophobic zeolite of the present invention was obtained by heat-treating a commercially available dealumininated USY-type hydrophobic zeolite (manufactured by Tosoh, SiO2 / Al2O3 molar ratio 115, zeolite obtained by contacting Y-type zeolite with concentrated hydrochloric acid (pH 1 or less)) at 790°C for 2 hours in a 70% by volume water vapor atmosphere (contact with water vapor). The SiO2 / Al2O3 molar ratio was 115, and the D50 was 2.3 μm. In addition, the amount of water adsorbed and toluene adsorbed at 25°C was measured, and the results are shown in Figures 1 and 2, and Table 1, respectively.

[0047] Example 5 The hydrophobic zeolite of the present invention was obtained by heat-treating a commercially available dealumininated USY-type hydrophobic zeolite (manufactured by Tosoh, SiO2 / Al2O3 molar ratio 115, zeolite obtained by contacting Y-type zeolite with concentrated hydrochloric acid (pH 1 or less)) at 830°C for 2 hours in a 70% by volume water vapor atmosphere (contact with water vapor). The SiO2 / Al2O3 molar ratio was 115, and the D50 was 2.5 μm. In addition, the amount of water adsorbed and toluene adsorbed at 25°C was measured, and the results are shown in Figures 1 and 2, and Table 1, respectively.

[0048] Example 6 The hydrophobic zeolite of the present invention was obtained by heat-treating a commercially available dealumininated USY-type hydrophobic zeolite (manufactured by Tosoh, SiO2 / Al2O3 molar ratio 115, zeolite obtained by contacting Y-type zeolite with concentrated hydrochloric acid (pH 1 or less)) at 790°C for 2 hours in a 60% by volume water vapor atmosphere (contact with water vapor). The SiO2 / Al2O3 molar ratio was 115, and the D50 was 2.3 μm. In addition, the amount of water adsorbed and toluene adsorbed at 25°C was measured, and the results are shown in Figures 1 and 2, and Table 1, respectively.

[0049] Example 7 The hydrophobic zeolite of the present invention was obtained by heat-treating a commercially available dealumininated USY-type hydrophobic zeolite (manufactured by Tosoh, SiO2 / Al2O3 molar ratio 115, zeolite obtained by contacting Y-type zeolite with concentrated hydrochloric acid (pH 1 or less)) at 790°C for 2 hours in an 80% by volume water vapor atmosphere (contact with water vapor). The SiO2 / Al2O3 molar ratio was 115, and the D50 was 2.3 μm. In addition, the amount of water adsorbed and toluene adsorbed at 25°C was measured, and the results are shown in Figures 1 and 2, and Table 1, respectively.

[0050] Comparative Example 1 The amount of water adsorbed and toluene adsorbed by commercially available Y-type zeolite (manufactured by Tosoh, SiO2 / Al2O3 molar ratio 6.1, Na2O content 0.24% by mass) at 25°C was measured, and the results are shown in Figures 1 and 2, and Table 1, respectively.

[0051] Comparative Example 2 The zeolite of Comparative Example 1 was dealuminized with concentrated hydrochloric acid (pH 1 or less) to obtain a USY-type zeolite with an SiO2 / Al2O3 molar ratio of 104. The amount of water adsorbed at 25°C was measured, and the results are shown in Figures 1 and 2, and Table 1, respectively.

[0052] Comparative Example 3 The water adsorption and toluene adsorption amounts of commercially available dealumininated USY-type hydrophobic zeolite (manufactured by Tosoh, SiO2 / Al2O3 molar ratio 115, zeolite obtained by contacting Y-type zeolite with concentrated hydrochloric acid (pH 1 or less)) were measured at 25°C, and the results are shown in Figures 1 and 2, and Table 1, respectively.

[0053] [Table 1]

[0054] As is clear from Figures 1 and 2 and Table 1, the hydrophobic zeolite of the present invention possessed high hydrophobicity, high organic compound adsorption performance, and high adsorption selectivity of organic compounds to water.

Claims

1. The amount of water adsorbed at 25°C and 70% RH is (2.6 g / 100 g of zeolite) or less, and the amount of toluene adsorbed at 25°C and 0.1 kPa is (17.2 g / 100 g of zeolite) or more, and the ratio of toluene adsorbed to water is 4.9 or more, and SiO ２ / Al ２ O ３ A hydrophobic zeolite having a FAU structure with a molar ratio in the range of 115 to 150.

2. The hydrophobic zeolite according to claim 1, characterized in that the ratio of toluene adsorbed to water is 6.9 or more.

3. A hydrophobic zeolite according to claim 1 or claim 2, characterized in that it contains one or more metals selected from the group consisting of sodium, potassium, cesium, iron, copper, silver, platinum, ruthenium, rhodium, palladium, and iridium.

4. A method for producing hydrophobic zeolite according to any one of claims 1 to 3, characterized in that the zeolite is brought into contact with an acidic solution, and then brought into contact with water vapor at a temperature of 790°C to 900°C in an atmosphere with a water vapor concentration of 60% to 80% by volume.

5. The method for producing hydrophobic zeolite according to Claim 4, characterized in that the zeolite is brought into contact with an acidic solution, and then brought into contact with water vapor at a temperature of 790°C to 830°C in an atmosphere with a water vapor concentration of 60% to 80% by volume.

6. A molded article containing the hydrophobic zeolite described in any one of claims 1 to 3.

7. An organic compound adsorbent containing the hydrophobic zeolite described in any one of claims 1 to 3.

8. A method for removing organic compounds, comprising contacting the organic compound adsorbent described in claim 7 with a fluid containing at least one organic compound, and removing the organic compound from the fluid.

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