WO2005002727A1

WO2005002727A1 - Photocatalytically active nanoporous material and method for producing same

Info

Publication number: WO2005002727A1
Application number: PCT/JP2004/009784
Authority: WO
Inventors: Takeshi Yao; Yasuo Iizuka; Atsushi Nakahira; Naoshi Ozawa
Original assignee: Kansai Technology Licensing Organization Co., Ltd.
Priority date: 2003-07-04
Filing date: 2004-07-02
Publication date: 2005-01-13

Abstract

Disclosed is a method for forming uniform titanium oxide on the surface and nanopore surfaces of a nanoporous substrate. Also disclosed are a photocatalytically active nanoporous material produced by such a method and uses of the photocatalytically active nanoporous material. Specifically, disclosed is a method for producing a photocatalytically active nanoporous material which is characterized in that titanium oxide is formed on the surface and nanopore surfaces of a nanoporous substrate by bringing the nanoporous substrate into contact with an aqueous solution containing precursors of titanium oxide.

Description

Photocatalytically active nanoporous material and its production method

The present invention provides a method of forming titanium oxide on the surface of a porous substrate having nano-order pores and an inner surface of the pores from an aqueous solution containing a precursor of titanium oxide, and is produced by the method. The present invention relates to a nanoporous material having photocatalytic activity.

Light

Background field technology

Since titanium oxide can easily decompose organic substances by light irradiation, titanium oxide is used as a catalyst for photodecomposition reactions to decompose various organic substances, such as toxic substances dissolved in water or suspended in air. It can be used to decompose and sterilize odorous substances, and has been put into practical use for environmental purification, epidemic prevention, and the like.

Titanium oxide is effectively used as a catalyst by forming a titanium oxide thin film on the surface of a substrate such as glass or tile. Methods for forming a titanium oxide thin film on a substrate surface include methods such as CVD, ion plating, and sputtering. As another method, there is a method in which an admixture obtained by kneading a fine powder of titanium oxide with a binder and a dispersant is applied to the surface of a base material and dried. Further, a method of immersing a substrate in an aqueous solution containing fluorotitanic acid in the presence of a fluoride ion scavenger such as boric acid to form a titanium oxide coating layer on the surface of the substrate is disclosed in Japanese Patent Application Laid-Open No. 9-249. No. 418, and WO98 / 11020 pamphlet.

However, Japanese Patent Application Laid-Open No. Hei 9-249418 and International Patent Publication No. WO 98/110210 both disclose a method of forming a titanium oxide coating layer on the surface of a substrate. There is no disclosure of a method for forming a uniform titanium oxide thin film on the surface of a porous material and the surface inside pores. Further, it is disclosed that the titanium oxide thin film formed by the method of Japanese Patent Application Laid-Open No. Hei 9-244918 and WO 98/110210 has a photocatalytic activity. But only in the visible light range It does not exhibit a high photocatalytic function for such light sources. Disclosure of the invention

An object of the present invention is to overcome the problems of the prior art and form a fine titanium oxide on the surface of a nano-porous substrate and on the inner surface of pores. An object of the present invention is to provide a photocatalytically active nanoporous material formed by the method, particularly a photocatalytically active nanoporous material having photocatalytic activity in a visible light region. Another object of the present invention is to provide a use of the photocatalytically active nanoporous material.

The present inventors have conducted intensive studies in order to achieve the above-mentioned object.As a result, the nanoporous substrate was placed in an aqueous solution containing a specific concentration of a fluorotitanium complex conjugate and a fluoride ion scavenger. It has been found that fine titanium oxide can be formed not only on the surface of the substrate but also on the inner surface of the pores by immersion and degassing. Further studies based on such knowledge led to the completion of the present invention.

That is, the present invention relates to the following method for producing a photocatalytically active nanoporous material, a nanoporous material having photocatalytic activity produced by the method, and uses of the photocatalytically active nanoporous material.

Item 1. A photocatalytically active nanoporous material characterized in that a nanoporous substrate is brought into contact with an aqueous solution containing a precursor of titanium oxide to form titanium oxide on the surface of the substrate and the inner surface of pores. Recipe.

Item 2. A nanoporous substrate is immersed in an aqueous solution containing a titanium oxide precursor, and is evacuated under reduced pressure to form titanium oxide on the surface of the substrate and the inner surface of pores. The production method according to item 1.

Item 3. The aqueous solution containing the precursor of titanium oxide is (1) an aqueous solution containing a fluorotitanium complex compound and a fluoride ion scavenger, (2) an aqueous solution containing titanium fluoride (TiF ₄ ) and ammonia, (3) titanyl sulfate aqueous solution containing (TiOS0 ₄₎ and HC 1 or NH ₄ 〇_H, or (4) photocatalytic activity nanoporous according to claim 1 or 2 Ru titanium dichloride (TiOCl ₂₎ Taukappa solution der obtained from titanium tetrachloride and water Quality material manufacturing method.

Item 4. An aqueous solution containing a precursor of Titan is prepared by mixing a fluorotitanium complex compound and a fluorine compound. Item 3. The method for producing a photocatalytically active nanoporous material according to Item 1 or 2, which is an aqueous solution containing a halide ion scavenger.

Item 5. The fluorotitanium complex compound is H ₂ T i F ₆ , (NH ₄ ) ₂ T i F ₆ , Na ₂ T i F ₆ , K ₂ T i F ₆ , R b ₂ T i F _6, and C s Item 5. The production method according to Item 4, which is at least one member selected from the group consisting of ₂ T i F ₆ .

Concentration of claim 6. Furuorochitan complex compound in the aqueous ^{solution, 1 X 1 0- 9 ~:} LX 1 0 one ² process according to claim 5, about mo 1 ZL.

Item 7. The method according to Item 4, wherein the fluoride ion scavenger is at least one member selected from the group consisting of orthoboric acid, metaboric acid, and boron oxide.

Claim 8. The concentration of fluoride ion-capturing agent in the aqueous solution, 1 X 1 0- ² ~: process according to L 0 mo 1 to claim 7 is ZL about.

Item 9. The method according to any one of Items 1 to 4, wherein the nanoporous substrate is a substrate containing 99.9% by weight or more of silicon dioxide.

Item 10: The BET specific surface area of the nanoporous base material is about 50 to 100 O n ^ Z g, and the total pore volume by the MP method is about 0.3 to 1.0 O ml Zg. Item 5. The method according to any one of Items 1 to 4, wherein the pore diameter is about 1 to 100 nm.

Item 11. The method according to any one of Items 1 to 4, wherein the precipitation height of titanium oxide formed on the surface of the nanoporous substrate and the inner surface of the pores is about 0.2 to 10 nm.

Item 1 2. The method according to Item 4, wherein the nanoporous substrate is used in an amount of about 10 to 500 g per liter of an aqueous solution containing a fluorotitanium complex compound and a fluoride ion scavenger.

Item 1 3. The pore size distribution of the raw material nanoporous substrate and the pore size distribution of the photocatalytically active nanoporous material after the formation of titanium oxide are substantially different. Item 5. The method according to any one of Items 1 to 4.

Item 1 4. Item 1 to: A photocatalytically active nanoporous material produced by the production method according to any one of L3.

Item 15 5. The photocatalytically active nanoporous material according to Item 14, which has photocatalytic activity in visible light (wavelength: about 500 to 700 nm).

Item 1 6. A photocatalytically active nanoporous material in which titanium oxide having a deposition height of about 0.2 to 10 nm is formed on the surface of a nanoporous substrate and the inner surface of pores. Item 17. The photocatalytically active nanoporous material according to Item 16, having photocatalytic activity in visible light (wavelength: about 500 to 700 nm).

Item 16. The photocatalytically active nanoporous material according to Item 16, wherein the content of titanium oxide is about 0.01 to 20% by weight based on the total weight of the photocatalytically active nanoporous material.

Claim 1 9. a BET specific surface area of 5 0~1 0 0 0 m ² Zg about a total pore volume of 0. 3 to 1 Om l Zg about by the MP method, a pore diameter. 1 to:. L Item 16. The photocatalytically active nanoporous material according to Item 16, having a value of about 0 O nm.

Item 20. Further, the obtained photocatalytically active nanoporous material is chemically or physically treated to remove titanium oxide formed on the surface of the photocatalytically active nanoporous material. Item 13. The method according to any one of Items 1 to 13.

Item 21. The method according to Item 20, wherein the chemical treatment is a treatment in which the obtained photocatalytically active nanoporous material is brought into contact with an acidic liquid without degassing.

Item 22. A photocatalytically active nanoporous material produced by the production method according to Item 20 or 21.

Item 23. A film containing the photocatalytically active nanoporous material according to any one of Items 14 to 19.

Item 24. A wall material containing the photocatalytically active nanoporous material according to any one of Items 14 to 19 and 22.

Item 2 5. A fiber containing the photocatalytically active nanoporous material according to Item 22. Brief Description of Drawings

FIG. 1 is a schematic diagram of a reaction vessel used in Test Example 1.

FIG. 2 is a diagram showing the pore size distribution of the nanoporous substrate (catalyst support) in Test Example 3.

FIG. 3 is a diagram showing the pore size distribution of the photocatalytically active nanoporous material of the present invention (Example 1) in Test Example 3. Detailed description of the invention

Hereinafter, the present invention will be described in detail. I-Photocatalytically active nanoporous material

The photocatalytically active nanoporous material of the present invention is produced by contacting a nanoporous substrate with an aqueous solution containing a precursor of titanium oxide to form titanium oxide on the surface of the substrate and the inner surface of pores. You.

1 -1. Aqueous solution containing precursor of titanium oxide

Examples of the aqueous solution containing the titanium oxide precursor include (1) an aqueous solution containing a fluorotitanium complex compound and a fluoride ion scavenger, (2) an aqueous solution containing titanium fluoride (TiF ₄ ) and ammonia, and (3) a titanyl sulfate (TiOS0 _An aqueous solution containing ₄ ) and HC 1 or NH ₄ 〇H, or (4) an aqueous solution of dichloride titanate (TiOCl ₂ ) obtained from titanium chloride and water can be given. Hereinafter, (1) to (4) will be specifically described.

(1) An aqueous solution containing a fluorotitanium complex compound and a fluoride ion scavenger In the present invention, the fluorothiane complex compound used for forming a titanium oxide thin film has a general formula (I):

A ₂ T i F ₆ (I)

(In the formula, A is the same or different and represents a hydrogen atom, an alkali metal atom, or an ammonium group.)

It is represented by Examples of the alkali metal atom include Li, Na, K, Rb, and Cs. Compound (I) may be a polynuclear complex compound having a plurality of Ti atoms. Examples of such a fluorotitanium complex compound represented by the general formula (I) include H ₂ T i F ₆ , (NH ₄ ) ₂ T i F ₆ , Na ₂ T i F ₆ , K ₂ T i F ₆ , and Rb ₂ T i F ₆ and Cs ₂ T i F ₆ are exemplified. Among them, (NH ₄ ) ₂ T i F ₆ is particularly preferable. The fluorotitanium complex compound used in the present invention is not particularly limited as long as it is produced by a known method. For example, titanium oxide powder may be treated with hydrofluoric acid to obtain fluorotitanic acid. As the titanium oxide, any of rutile type, anatase type, brookite type, and amorphous may be used.

Also, a hydroxide or oxyhydroxide of titanium is dissolved in an aqueous solution of a metal hydrogen hydrogen fluoride such as ammonium hydrogen difluoride or sodium hydrogen difluoride to synthesize a fluorotitanium complex compound. It may be used in the production method of the present invention. . Furuorochitan complex ^{compound, 1 0- 9 ~9 X 1 0-} 2 mo 1 / L , preferably about 1 0 one ⁶ ~ 9 X 1 0 one ³ mo 1 / L or so, more preferably 1 0 one ^5-9 used in preparing the aqueous solution of X 1 0 one ³ m 0 1 ZL amounts of concentrations. For example, about 0.001 to 20 g of titanium oxide is mixed with 40 Oml of a 0.0001 to 0.6 mo / L hydrofluoric acid aqueous solution to give a concentration of 10 to ⁹ to 10 g. an aqueous solution containing ^{9 X 1 0- 2 mo 1 /} L of about Furuorochita down complex Ion is obtained.

In one 0- ⁹ mo less than about 1 / L, can not be formed of titanium oxide capable of emitting volatilization effects of the present invention to a substrate surface or surfaces inside the pores, an aqueous solution exceeding 9 X 1 0 ~ about ² mo 1 ZL When used, it becomes cloudy together with the fluoride ion scavenger or a solution added thereto, and a titanium oxide thin film capable of exhibiting the effect of the present invention cannot be formed on the surface of the substrate or the inner surface of the pores. The term may be an aqueous solution containing excess hydrogen fluoride used for synthesizing the complex compound from titanium oxide as described above. Further, water-soluble substances such as hydrogen fluoride, hydrogen chloride, and ammonia may be contained as long as the effects of the present invention are not adversely affected. Further, an excess amount of titanium oxide is further added to the prepared aqueous solution of the fluorotitanium complex compound (hereinafter, as defined above) to form a saturated solution of the above complex compound, and then the insoluble titanium oxide is filtered off. The removed aqueous solution may be used.

Further, a seed crystal for forming titanium oxide may be added to an aqueous solution of such a fluorotitanium complex compound. The seed crystal to be used is preferably a target titanium oxide crystal. The seed crystal may have a small average particle diameter of 0.2 to about 0 nm, and the addition amount thereof is optional but may be small. By adding seed crystals, the deposition rate of titanium oxide can be increased.

In the present invention, the aqueous solution may contain a water-soluble organic solvent as long as the effect of the present invention is not adversely affected. As long as water is the main component, for example, alcohols such as methanol and ethanol; ethers such as dimethyl ether and getyl ether; ketones such as acetone; and the prevention of the presence of other water-soluble organic solvents Absent. However, the content of the organic solvent is preferably about 50% by volume or less based on the whole τΚ solution.

The fluoride ion scavenger used in the present invention has a uniformity dissolved in a liquid phase. There are one type and a heterogeneous type which is a solid. Depending on the purpose, one of these two types may be used, or both may be used.

The homogeneous fluoride ion scavenger reacts with the fluoride ion to form a stable fluoro complex compound and / or a stable fluoride, thereby oxidizing the surface of the nanoporous substrate and the inner surface of the pore. It shifts the equilibrium in a direction that promotes the hydrolysis reaction so that a titanium thin film is deposited. In addition to boron compounds such as orthoboric acid, metaboric acid, and boron oxide; aluminum chloride, sodium hydroxide, and aqueous ammonia are examples.

Specifically, as shown in the following formula, when precipitating with orthoboric acid _{_{(NH 4) 2 T i F}} 6 forces et T I_〇 _2, the reaction represented by the formula (III), F_ since moves rightward to consume, the equilibrium represented by the formula (II) is moved to the right to generate the F-, the result, a thin film made of T I_〇 ₂ is precipitated. Such a capturing agent is usually used in the form of an aqueous solution, but may be added in the form of a powder and dissolved in the system. The addition of the trapping agent may be performed once or several times intermittently, or may be performed continuously at a controlled supply rate, for example, at a constant rate.

T i F ₆ ² ~ + 2H ₂ 0 71 T i 0 ₂ + 6 F 1 + 4H + (||)

_{^{B0 3 3 - + 4 F- +}} 6H + → BF 4 - + 3H 2 0 (III) as the heterogeneous type fluoride ion-capturing agent, aluminum, titanium, iron, Ecke Le, magnesium, copper, metals such as zinc Semiconductors such as silicon and germanium; boron compounds such as orthoboric acid, metaboric acid and boron oxide; and compounds such as calcium oxide, aluminum oxide, silicon dioxide and magnesium oxide films. You. When such a solid is added or inserted into an aqueous solution, F— near the solid is consumed and its concentration decreases, so that the chemical equilibrium of that part shifts and titanium oxide is deposited. When such a solid is used, titanium oxide can be deposited on the surface of the nanoporous substrate and the inner surface of the pores immersed in an aqueous solution, depending on the insertion method and reaction conditions.

Homogeneous fluoride ion scavengers vary depending on the type and shape of the precipitates. The amount corresponding to the equivalent amount of fluoride ions in the solution, usually about 10 one ^4-5000 0%, preferably in a range of about 10 one ^{from 1 to} 30,000%. The heterogeneous fluoride ion scavenger is not particularly limited, and is preferably used in an amount that achieves the object and effects of the present invention.

(2) Aqueous solution containing titanium fluoride (TiF ₄ ) and ammonia

This aqueous solution is produced by adding a small amount of aqueous ammonia to an aqueous solution of TiF ₄ . The concentration of the aqueous solution of TiF ₄ may be about 0.005 to 0.5 mol / L, preferably about 0.01 to 0.1 mol / L, and the concentration of aqueous ammonia is about 0.05 to 5 mol / L, preferably 0.1 to 3 mol / L. It may be L or so. The aqueous solution obtained by adding aqueous ammonia preferably has a pH of between 1 and 3, preferably between 1.5 and 2.5, particularly about 1.0. For example, 0.74 g of TiF ₄ is dissolved in 150 ml of water to prepare a 0.04 mol / L aqueous solution, and a small amount of 0.1 mol / L aqueous ammonia is added to adjust the pH to about 2.0. In this solution, the hydration and dehydration of TiF ₄ gradually progress, and titanium oxide is formed. For example, at 60t: titanium oxide is formed in 1 to 48 hours.

(3) an aqueous solution containing HC 1 or NH ₄ 〇_H and titanyl sulfate (TiOS0 ₄₎

The aqueous solution, so that the concentration of Ti is _{0.001~0.1 mol / L, TiOS0 4.} X¾0 was added to an aqueous solution containing HC1 or NH ₄ 0H, is prepared by stirring about 1 hour at room temperature. At this time, the pH of the aqueous solution should be between 1.00 and 1.70. In this solution, 60: Holding, in 10 days from a few hours, Ti0 ₂ is formed on the substrate.

(4) Titanium dichloride aqueous solution obtained from titanium chloride and water

This aqueous solution is prepared, for example, by adding (distilled water to TiCl ₄ at TC to hydrolyze to prepare a TiOCl ₂ solution, and when the temperature is 17 to 230 ° C., O ₂ is precipitated. Use autoclave.

1 -2. Nanoporous substrate

As the nanoporous substrate used in the present invention, a porous substrate having nano-scale (about 1 nm to 100 nm), more specifically, a mesopore (2 to 50 nm) is particularly preferable. There is no limitation. Further, the nano BET specific surface area of the porous substrate is 50 to 100 0 m ² Zg about, in particular 200 to 500 meters ² Zg about all Hosoanayo product by the MP method is 0. 3~1. Oml / g approximately, Especially if it is about 0.3-0.7ml / g Yes.

The substrate can use a wide range of materials to carry the titanium oxide formed or to be coated for a particular purpose by the formed titanium oxide. For example, ceramics such as silicon dioxide, aluminum oxide, zirconium oxide, glass, magnesium oxide, zeolite, silicon nitride, silicon carbide, carbon materials, metals such as aluminum and titanium, silicon, germanium, etc. And the like. Above all, when used as a substrate for a photocatalytically active nanoporous material, silicon dioxide contains at least about 99.9% by weight, preferably about 99.9% by weight, excluding loss on ignition. Nanoporous substrates are preferred. For example, Siri force reference catalyst (JRC-S 1〇-8, a reference catalyst committee of the Catalysis Society of Japan), which is a nanoporous material produced from an aerosol of silicon dioxide, silica gel Q15 (average pore diameter of 15 plates, Pore volume: 1.0 ml / g, specific surface area: 200 m ² / g, manufactured by Fuji Silicon Chemical Co., Ltd.). This is thought to be because the band gap of titanium oxide is reduced due to the action of the interface between the formed titanium oxide and the silicon dioxide contained in the nanoporous substrate, thereby facilitating absorption of visible light. It is. In this case, the conventional titanium oxide catalyst can be used with natural light (ultraviolet light and visible light) or even with visible light (wavelength: about 400 to 800 nm, especially about 500 to 700 nm). It has an extremely high activity compared to.

The shape of the substrate is not particularly limited. Various shapes such as a sphere, a plate, a prism, or a donut with a hole in the center are used depending on the application. The base material can be held through a fiber or the like in a donut-shaped bamboo or center hole.

I I. Preparation of photocatalytically active nanoporous materials

The photocatalytically active nanoporous material of the present invention is produced by forming titanium oxide on the surface of the nanoporous material and the inner surface of the pores as follows.

First, a nanoporous substrate is brought into contact with an aqueous solution containing a precursor of titanium oxide to form titanium oxide on the surface of the substrate and the inner surface of pores. Examples of the aqueous solution containing the precursor of titanium oxide include the aqueous solutions of the above (1) to (4), and any aqueous solution may be used.

Here, (1) aqueous solution containing fluoro titanium complex compound and fluoride ion scavenger The liquid will be specifically described below by way of example, but is not limited thereto. First, a mixed solution is obtained by adding a fluoride ion scavenger to an aqueous solution containing a fluorotitanium complex compound. The concentration of the fluorothiane complex compound and the fluoride ion scavenger in the aqueous solution can be appropriately selected from the above-mentioned ranges and employed.

A nanoporous substrate is brought into contact with the mixed solution to form titanium oxide on the surface of the substrate and the inner surface of the pores. The method of contacting the nanoporous base material with the mixed solution is as follows. Specifically, while immersing the nanoporous base material in the mixed solution, the gas contained in the pores of the base material is reduced under reduced pressure. Do it out of the air. Alternatively, the pressure may be reduced in a container containing only the nanoporous substrate, the gas contained in the pores of the substrate is evacuated, and the mixed solution may be injected into the container. As a result, the mixture infiltrates into the pores of the nanoporous base material, and fine titanium oxide precipitates in the pores. Vacuum conditions are not particularly limited as long as the pressure that may evacuated gas from the pores, ^{^{e.g., 1 0- 2 ~1 0 4 P}} a , preferably about 1 0 one ² to 1 0 ² P a The pressure may be about 0.1 to 10 minutes. The temperature at which the nanoporous substrate is immersed in the mixed solution is about 10 to 80 ° C, preferably about 20 to 50 ° C, and more preferably about 35 to Set in the range of about 40 ° C. The time may be about 4 to 48 hours.

In addition, the nanoporous substrate is usually used in an amount of about 10 to 500 g, preferably about 50 to about L 0 g per 1 L of an aqueous solution containing a fluorotitanium complex compound and a fluoride ion scavenger. Good. Within this range, the intended photocatalytically active nanoporous material of the present invention can be easily obtained.

The time at which the nanoporous substrate is immersed in the aqueous solution of the fluorotitanium complex compound may be before, at the same time as, or after the addition or introduction of the fluoride scavenger. However, when using a nanoporous substrate that may be attacked by the system, care must be taken in the composition of the solution, the reaction conditions, and the timing of immersion. When the substance constituting the nanoporous substrate acts as a heterogeneous fluoride ion trapping material, it may not be necessary to add the uniform fluoride ion trapping material. The shape of the nanoporous substrate is arbitrary, and particles, plates, or specific shapes depending on the purpose can be used. Further, for the purpose of uniformly depositing fine titanium oxide, the substrate can be slowly rotated at a rotation speed of, for example, 10 rpm or less, preferably 5 rpm or less. The oxidized titanium thus formed on the substrate has photocatalytic activity by appropriately setting the precipitation conditions, particularly without going through a heating step such as firing. Further, a heating step may be provided according to the purpose. The heating step can be performed, for example, at 80 to 600 ° C. for about 0.5 to 50 hours.

In the photocatalytically active nanoporous material of the present invention thus obtained, fine titanium oxide is uniformly formed on the surface of the nanoporous substrate and the inner surface of the pores. The titanium oxide may be precipitated as fine particles on the surface of the substrate and the inner surface of the pores, or as a thin film (or layer).

Furthermore, after titanium oxide is formed on the surface of the substrate and the inner surface of the pores, the titanium oxide on the surface of the substrate can be removed by a physical treatment or a chemical treatment.

For chemical removal, for example, after forming titanium oxide on the surface of the base material and the inner surface of the pores, do not deaerate the acid liquid (for example, sulfuric acid, hot concentrated sulfuric acid, hot concentrated sulfuric acid and ammonium sulfate) By contacting (immersion, stirring, etc.) with a mixed solution, an acid such as hydrofluoric acid) or a basic liquid (eg, τΚ sodium oxide, etc.), the titanium oxide on the surface of the base material is dissolved to substantially reduce It is possible to obtain a nanoporous substrate having titanium oxide formed only on the inner surface of the pore.

In addition, for physical removal, for example, after forming titanium oxide on the surface of the base material and the inner surface of the pores, the surface of the porous material is cut using a roll mill, a sand mill, or the like, thereby substantially reducing the thickness. A nanoporous substrate having titanium oxide formed only on the inner surface of the pore can be obtained.

In the case of this photocatalytically active nanoporous material, since the material surface has no photocatalytic activity, it has the characteristic that even if it comes into direct contact with an organic substance or the like, it does not attack it. By taking advantage of this feature, the photocatalytically active nanoporous material can be used, for example, woven into a fiber, or stored and stored in a plastic container.

The photocatalytically active nanoporous material of the present invention has high photocatalytic activity in visible light (wavelength: about 400 to 800 nm, particularly about 500 to 70 O nm). The deposition height (thickness) of titanium oxide is about 0.2 to 10 nm, preferably about 0.2 to 5 nm, and the deposition height (thickness) of titanium oxide is very small. It has the characteristic of. Thus, the titanium oxide and the silicon dioxide contained in the nanoporous base material are It is thought that the bandgap of titanium atoms becomes smaller due to the action of the interface, and this makes it possible to absorb visible light. Here, the deposition height (thickness) means the height (thickness) of the titanium oxide particles or thin film deposited on the substrate from the substrate surface.

The content of titanium oxide contained in the photocatalytically active nanoporous material of the present invention is about 0.01 to 20% by weight, preferably about 0.05 to 10% by weight, based on the total weight of the material. It is.

It is also considered that the fine pores of the photocatalytically active nanoporous material of the present invention are not densely filled with titanium oxide particles, but fine titanium oxide particles are formed on the inner surface of the fine pores. It is characterized in that sufficient pore voids for entering organic molecules remain. This is supported, for example, by the results of Test Example 3. That is, Test Example 3 shows that the pore size distribution (or pore size distribution) of the photocatalytically active nanoporous material of the present invention is almost equal to the pore size distribution of the raw material nanoporous substrate. Is performed. Here, the pore size distribution refers to the relationship between the pore diameter and the pore volume obtained from the adsorption isotherm at the liquid nitrogen temperature of nitrogen gas by the BJH method, as described in Test Example 3. Measured by the method. Therefore, according to the production method of the present invention, a photocatalytically active nanoporous material in which the pore size distribution of the nanoporous substrate of the catalyst carrier is not substantially changed is produced. The BET specific surface area of the photocatalytic activity nanoporous material of the present invention is 5 0~1 0 0 0 m about ² Z g, a total pore volume by the MP method is 0.3 to 1. In O ml / g of about Yes, the pore diameter of the nanoporous substrate is about 1 to 100 nm, which is substantially the same as the nanoporous substrate of the catalyst support. Therefore, the light transmission efficiency is increased, and the opportunity of sufficient contact between the titanium oxide photocatalyst and the organic molecule is maintained. Further, since the titanium oxide of the photocatalytically active nanoporous material of the present invention is very fine or thin as described above, the amount of titanium oxide as a raw material (and, as a result, a titanium oxide precursor such as a fluorotitanium complex compound as a raw material) is reduced. Is economical. Moreover, for example, as shown in Test Example 1, it can be seen that the photocatalytic activity per 1 g of titanium oxide in natural light (ultraviolet light and visible light) is much larger than that of the conventional product. Furthermore, for example, as shown in Test Example 2, it can be seen that the photocatalytic activity is extremely large only with visible light. In other words, according to the production method of the present invention, titanium oxide is effectively used, There is an advantage that the medium capacity can be maximized.

Furthermore, the titanium oxide of the photocatalytically active nanoporous material of the present invention has a feature that it is strong and stable.

I I I. Applications of photocatalytically active nanoporous materials

The photocatalytically active nanoporous material of the present invention can be used as a material for various filters that maintain a photocatalytic function. As a method for fixing the photocatalytically active nanoporous material to the substrate, a known method may be used. For example, a photocatalytically active nanoporous material is fixed to a substrate such as a honeycomb filter using a binder (for example, a silica-based binder such as silicon alkoxide, colloidal silica, an alumina-based binder, and a cement-based binder). And the like.

The filter thus obtained is used as a photocatalyst filter together with a light source such as a natural light or an ultraviolet lamp. In particular, since the photocatalytically active nanoporous material of the present invention has high photocatalytic activity even in natural light, its use is wide. Specifically, filters for household appliances (air purifiers, ventilation fans, etc.), filters for automobile-related parts (dust-proof filters, air-conditioner filters, etc.), and filters for civil engineering and building materials (room wallpaper, dust-proof filters, etc.) It can be used in a wide range of fields, such as filters for industrial parts (such as filtration filters).

The filter of the present invention can treat airborne odor-causing substances, dust, microorganisms, viruses, causative substances of the Sick House Syndrome (formaldehyde and the like), odor components (tobacco odor and the like), chemical substances and the like. According to the photocatalytic filter of the present invention, these can be efficiently adsorbed, decomposed and removed.

In addition, the photocatalytically active nanoporous material of the present invention has high durability, and is suitable for natural light, particularly in the visible light region (wavelength: about 400 to 800, particularly about 500 to 700). However, since it has high photocatalytic activity, it can be used as indoor and outdoor wall materials, waste liquid treatment materials, adsorbents, building materials, preservatives, etc.

In particular, a photocatalytically active nanoporous material having titanium oxide only on the inner surface of the pores can be used coexisting with an organic substance, and thus can be used by weaving into fibers, woven fabric, cloth, or the like. Alternatively, since it can be fixed with an organic binder, it can be used for paints, indoor and outdoor wall materials, and the like. BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

Example 1

(1) Drying of the catalyst support substrate

Reference catalyst JRC-SI0-8 (Catalyst Society of Japan Reference Catalyst Committee) 2. 3 g was immersed in 50 ml of acetone at room temperature and subjected to ultrasonic cleaning for 20 minutes to replace acetone and water inside the pores. After that, iRC_SIO-8 was taken out, stored in an incubator at 105 ° C for 1 day or more, and dried.

(2) Preparation of solution

Boron oxide (B ₂ 0 ₃₎ 4. The 1772 g was dissolved in ultrapure water 25 OML, was B ₂ 〇 ₃ aqueous solution at a concentration 0. 24mo 1ZL. Also, 0.1484 g of (NH ₄ ) ₂ Ti F ₆ was dissolved in 30 Oml of ultrapure water to obtain an aqueous solution of (NH ₄ ) ₂ Ti F ₆ having a concentration of 0.0025mo 1 / L.

(3) Film formation

: 6 ₂ 〇 ₃ solution 22. 5 ml and _{_{(NH 4) 2 T i F}} 6 7. 5ml was placed and mixed in a polystyrene Ne Jibin. At this time, the concentration of B ₂ 〇 ₃ 0. 18 mol / L, the concentration of _{_{(NH 4) 2 T i F}} 6 becomes 0. 000625 mo 1 / L. After the mixture was shaken well, quickly dried JRC-SI0-82.3 g was placed therein. Polystyrene screw bottle vacuumed for 3 minutes in a vacuum desiccator Ichita (pressure: 10 ² Pa). After that, it was allowed to elapse for 1 day in an incubator set at 40 ° C, and [Titanium oxide was deposited on RC-SI0-8. Thereafter, the sample was rinsed with distilled water a few times, and dried in an incubator set at 105 for about 1 day to obtain 2.3 g of the solvent-active nanoporous material of the present invention. When film was formed on the JRC-SI0- 8 titanium component of the mixed solution becomes all titanium oxide, Ti0 ₂ is calculated to 0.065 wt% on.

Comparative Example 1

As a control of Example 1, a commercially available photocatalyst, powdered titanium dioxide P25 (powder average particle diameter: 2 nm, manufactured by Nippon Aerosil Co., Ltd.) was used. Test example 1 (natural light)

Formaldehyde and Sankare (Example 1 or Comparative Example 1) are placed in a 4L soda-lime glass transparent container shown in Fig. 1 and exposed to natural light (sunlight + fluorescent light during the day, fluorescent light only at night). Was decomposed. A container was filled with formaldehyde (initial concentration: 20 ppm) and a sample (1.4 g), and the amount of formaldehyde reduced was measured by irradiation with natural light. The results are shown in Table 1. The sample of Example 1 was in the form of a pellet, and the sample of Comparative Example 1 was in the form of the powder described above. In addition, since the initial adsorption of formaldehyde to the sample is mainly performed for 1 hour from the start of the measurement, the time (h) in the table is set to 1 hour after the start of the measurement (hereinafter, Tables 2 to 4). Same for 4).

table 1

Table 2 shows the results obtained by converting the amount of formaldehyde reduction per g of titanium oxide in the sample. Specifically, the content of Sani匕titanium in each Sankare used in the experiment, the content of Comparative Example 1 (P 2 5) are all Ti0 ₂ so Ti0 ₂ is 1. 4 g, real Example 1 the 1.4 0.065 wt% maximum of g is 1 ^ 0 ₂ so, the content of Ti0 ₂ is 0. 0 0 0 9 1 g at maximum. Reduction of formaldehyde in each time (pm), divided by the amount of Ti0 ₂ in each sample (g) is a number in Table 2. For real Example 1, since the content was calculated in Ti0 ₂ in a sample as a maximum value, the real time is considered to be larger than the values in Table 2. Table 2

Table 1 shows that the photocatalytically active nanoporous material of the present invention (Example 1) has a high formaldehyde resolution under natural light. Furthermore, according to Table 2, it was observed that the photocatalytically active nanoporous material of the present invention had extremely high formaldehyde resolving power per 1 g of titanium oxide.

Test example 2 (visible light)

Formaldehyde and a sample (Example 1 or Comparative Example 1) were put in a 4L soda lime glass transparent container shown in Fig. 1, and a visible light (fluorescent lamp (Toshiba Corporation; FHF32YPNU) was used to conduct a formaldehyde experiment, in which a container was filled with formaldehyde (initial concentration: 20 ppm) and a sample (1.4 g), and the amount of formaldehyde reduction was measured by irradiating with visible light. The results are shown in Table 3. Note that the sample of Example 1 was in the form of pellets, and the sample of Comparative Example 1 was in the form of powder as described above.

Table 3

Table 4 shows the results obtained by converting the amount of reduced formaldehyde to 1 g of titanium oxide in the sample. To be specific, the titanium dioxide in each Sankare used in the experiment Content, Comparative Example 1 (P 2 5) the content of all Ti0 ₂ so Ti0 ₂ is 1.4 g, the actual Example 1 is 1.4 0.065 wt% maximum of g is Ti0 ₂ since , the content of Ti0 ₂ is 0. 0 0 0 9 1 g at maximum. Reduction of formaldehyde in each time (pm), divided by the amount of Ti0 ₂ in each sample (g) is a number in Table 4. For real Example 1, since the sample was calculated Ti0 ₂ of the content of the maximum value, the real time is considered to be larger than the values in Table 4.

Table 4

Table 3 shows that the photocatalytically active nanoporous material of the present invention (Example 1) has a high formaldehyde resolution under visible light. Furthermore, according to Table 4, it can be seen that the photocatalytically active nanoporous material of the present invention has extremely high formaldehyde resolving power per 1 g of titanium oxide.

Test example 3 (pore size distribution)

About 0.2 g of the sample of Example 1 was placed in a sample tube, pretreated at 150 ° C, and sufficiently degassed under vacuum. Then, N ₂ gas was introduced, and the adsorption isotherm was measured by the BJH method. Assuming that the pores of the sample of Example 1 were cylindrical pores, the pore diameter distribution was determined by a method of calculating the pore diameter distribution using a desorption isotherm. Figure 2 shows the results.

In addition, the pore size distribution of JRC-SI0-8, which is the catalyst carrier of Example 1, was determined in the same manner. Figure 3 shows the results.

In FIGS. 2 and 3, Rp represents a pore radius, and V represents a pore volume. The pore distribution curves in FIGS. 2 and 3 show the rate of change of the pore volume V (d VZd R) with respect to a small change in the pore radius Rp. FIGS. 2 and 3 show that the catalyst carriers JRC-SI0-8 and the sample of Example 1 have almost the same pore size distribution. From this, it is inferred that the titanium oxide precipitated in the material of the present invention is extremely fine of nano size.

Example 2

(1) Drying of the catalyst support substrate

2.3 g of silica gel Q15 (average pore size: 15 nm, pore volume: 1. Oml / g, specific surface area: 200 m ² / g, manufactured by Fuji Silicon Chemical Co., Ltd.) was dried in a 105 ° C incubator for 1 day.

(2) Preparation of solution

Boron oxide _{_{(B 2 0 3) 4. 1772}} g were dissolved in ultra-pure water 125 ml, and a B ₂ 0 ₃ solution of concentration 0. 48mo 1. In addition, the (NH ₄₎ ₂ T i to F ₆ 0. 1484 g was dissolved in ultrapure water 15 OML, concentration 0. 005 Omo 1 / L (NH 4) 2 T i F 6 7 solution.

(3) Film formation

8 ₂ 0 ₃ solution 22. 5 ml and _{_{(NH 4) 2 T i F}} 6 7. 5ml was placed and mixed in a polystyrene Ne Jibin. At this time, the concentration of B ₂ 〇 ₃ is 0.36 mol / L, and the concentration of (NH ₄ ) ₂ T i? ₆ is 0.000125 mo 1 / L. After the mixture was shaken well, quickly dried D152.3 g was put therein. Polystyrene screw bottle evacuated to 3 minutes in a vacuum desiccator one evening in (pressure: 10 ² Pa). After that, one day was allowed to pass for 40 days incubating overnight, and titanium oxide was deposited on Q15. Thereafter, the sample was rinsed with distilled water a few times, and dried in an incubator set at 50 ° C. for about 1 day to obtain 2.3 g of the photocatalytically active nanoporous material of the present invention. If you and was deposited on the silica force gel Q15 becomes titanium component of titanium oxide of the mixed solution, Ti0 ₂ is calculated to 0.13 wt% on.

Example 3

Boron oxide (B ₂ 0 ₃₎ 4. The 1772 g was dissolved in ultrapure water 25 OML, and a B ₂ 0 ₃ solution of concentration 0. 24mo 1ZL. Also, 0.1484 g of (NH ₄ ) ₂ Ti F ₆ was dissolved in 30 Oml of ultrapure water to obtain an aqueous solution of (NH ₄ ) ₂ Ti F ₆ having a concentration of 0.0025mo 1 / L.

8 ₂ 0 ₃ solution 22. 5 ml and polystyrene _{_{(NH 4) 2 T i F}} 6 7. 5ml Ne Mix in a vial. At this time, the concentration of B ₂ 0 ₃ is 0. 1 8mol / L, the concentration of _{_{(NH 4) 2 T i F}} 6 becomes 0. 0 0 0 6 2 5 mol / L.

Except for the above, the same treatment as in Example 2 gave 2.3 g of a photocatalytically active nanoporous material of the present invention. When titanium component of the liquid mixture Te summer and of titanium oxide and were deposited on the silica gel Q15, Ti0 ₂ is Ru was calculated to 0.065% by weight carrier.

Test example 4 (natural light or visible light)

Place formaldehyde and a sample (Example 2 or Example 3) in a 4L soda-lime glass transparent container shown in Fig. 1 and use natural light (sunlight + fluorescent light during the day, fluorescent light only at night). Was used to conduct a formaldehyde decomposition experiment.

Also, formaldehyde and sampler (Example 2) were placed in a 4L soda lime glass transparent container shown in Fig. 1, and visible light (a fluorescent lamp with a spectral distribution of 500 to 700 nm wavelength (Toshiba Corporation, FHF32YPNU) Formaldehyde decomposition experiment was conducted in a container filled with formaldehyde (initial concentration: 20 ppm) and 1.4 g of each sample, and the amount of formaldehyde reduction was measured by irradiating natural light or visible light. The results are shown in Table 5. Note that the samples in Examples 2 and 3 were pellets, and the initial physical adsorption of formaldehyde to the sample was mainly performed until 1 hour from the start of measurement. Therefore, the time (h) in the table was set as the start time one hour after the start of measurement (the same applies to Table 6 below).

Table 5

Table 6 shows the results obtained by converting the amount of reduced formaldehyde to 1 g of titanium oxide in the sample. To be specific, the titanium dioxide in each Sankare used in the experiment Content, Example 2 1.4 up to 0.13% by weight of g 0 ₂ so the content of Ti0 ₂ is 0. 0 0 1 8 2 g at maximum, also Example 3 the 1.4 0.065 wt% maximum of g is Ti0 ₂ so the content of Ti0 ₂ is at most 0. 0 0 0 9 1 g . Reduction of formaldehyde in each time (p pm), divided by the amount of Ti0 ₂ in each sample (g) is a number in Table 6. Example 2 and Example 3, since the content was calculated in Ti0 ₂ in each sample as a maximum value, in fact, considered to be larger than the values in Table 6.

Table 6

According to Table 5, the photocatalytically active nanoporous materials of the present invention (Examples 2 and 3) have high formaldehyde resolution under natural light. Further, the medium-active nanoporous material of the present invention (Example 2) has a high formaldehyde resolution even under visible light. Furthermore, according to Table 6) ¹ medium activity nanoporous material of the present invention (Examples 2 and 3), it is seen formaldehyde resolution per Sani匕titanium 1 g is extremely high.

In addition, the well-known documents described in this specification are incorporated by reference.

Example 4

In a flask containing the photocatalytically active nanoporous material obtained in Example 2, concentrated sulfuric acid and ammonium sulfate were added at a weight ratio of 1.8: 1 under normal pressure, and the mixture was slowly heated with a gas burner. Thus, the titanium oxide on the surface of the nanoporous material was dissolved and removed to obtain a nanoporous material in which titanium oxide was formed substantially only on the inner surface of the pores.

Example 5

The photocatalytically active nanoporous material obtained in Example 2 was subjected to normal temperature (25 ° C) and normal pressure, 0. Immersion in lmol / L hydrofluoric acid for 5 minutes to dissolve and remove titanium oxide on the surface of the nanoporous material, and nanoporous with silicon oxide formed only on the inner surface of pores The material was obtained.

Example 6

The photocatalytically active nanoporous material obtained in Example 2 was treated with a pole mill to physically cut and remove titanium oxide on the surface of the nanoporous material, and substantially to the inner surface of the pores. Only a nanoporous material on which titanium oxide was formed was obtained.

The nanoporous materials obtained in Examples 4, 5, and 6 maintain high catalytic activity and are stable without decomposition even when irradiated with light using a substrate such as a fiber or an organic binder. Was found to be retained. The invention's effect

According to the method for producing a photocatalytically active nanoporous material of the present invention, titanium oxide can be formed almost uniformly on the surface of the nanoporous substrate and the surface of the pores thereof. Moreover, in this production method, a heating step for crystallizing the titanium oxide is not necessarily required, so that it is not particularly necessary to consider the heat durability of the substrate. There is no distortion due to heating and cooling. Furthermore, it is a simple and inexpensive manufacturing method.

In the production method of the present invention, the pore size distribution between the nanoporous substrate and the photocatalytically active nanoporous material after the deposition of titanium oxide is substantially equal, and therefore the pore size of the substrate is reduced. Size can be reflected in the target photocatalytically active nanoporous material. That is, since titanium oxide is formed very thinly (nano-orderly) on the surface of the nanoporous base material and the surface of the pores, a sufficient contact field (pore size) with organic molecules is maintained. It is.

Furthermore, after forming titanium oxide on the surface of the substrate and the inner surface of the pores, the titanium oxide on only the surface of the substrate is substantially removed by physical treatment or chemical treatment, and Only a nanoporous substrate on which titanium oxide is formed can be obtained. In this case, since the surface has no photocatalytic activity, even if it comes into direct contact with an organic substance or the like, it does not attack it, and can be used, for example, woven into fibers.

The photocatalytically active nanoporous material of the present invention has high photocatalytic activity in visible light. Therefore, natural light can be used effectively without using expensive short-wavelength light sources. Further, the photocatalytically active nanoporous material of the present invention is characterized in that the photocatalytic activity per unit amount of titanium oxide is high.

Claims

The scope of the claims

1. A nanoporous substrate is brought into contact with an aqueous solution containing a precursor of titanium oxide to form titanium oxide on the surface of the substrate and the inner surface of pores. Material manufacturing method.

2. The nanoporous substrate is immersed in an aqueous solution containing a titanium oxide precursor, and is evacuated under reduced pressure to form titanium oxide on the surface of the substrate and the inner surface of the pores. The method according to claim 1.

3. The aqueous solution containing the titanium oxide precursor is (1) an aqueous solution containing a fluorotitanium complex compound and a fluoride ion scavenger, (2) an aqueous solution containing titanium fluoride (TiF ₄ ) and ammonia, (3) titanyl sulfate (TiOS0 ₄₎ and an aqueous solution containing HC 1 or NH ₄ OH, or (4) titanium dichloride obtained from titanium tetrachloride and water (TiOCl ₂₎ photocatalytic activity nanoporous described aqueous der Ru claim 1 or 2 Material manufacturing method.

4. The method for producing a photocatalytically active nanoporous material according to claim 1, wherein the aqueous solution containing the titanium oxide precursor is an aqueous solution containing a fluorotitanium complex compound and a fluoride ion scavenger.

5. The fluorotitanium complex compound is H ₂ T i F ₆ , (NH ₄ ) ₂ T i F ₆ , Na ₂ T i F ₆ , 2T i F ₆ , Rb ₂ T i F ₆ and Cs ₂ T i F ₆ 5. The method according to claim 4, which is at least one member selected from the group consisting of:

6. Concentration of Furuorochitan complex compound in the aqueous ^{solution, 1 X 1 0 - 9 ~} 1 X 10 one ² mo process according to claim 5, about 1ZL.

7. The method according to claim 4, wherein the fluoride ion scavenger is at least one selected from the group consisting of orthoboric acid, metaboric acid and boron dioxide.

8. The concentration of fluoride ion-capturing agent in the aqueous solution, the process described in 1 X 10_ ² ~1 Omo 1 about a is claim 7.

9. The method according to any one of claims 1 to 4, wherein the nanoporous substrate is a substrate containing 99.9% by weight or more of silicon dioxide.

10. a ² Zg about BET specific surface area 50~1000m nanoporous substrate, 0.1 is the total pore volume by the MP method 3-1. Is about OmlZg, pore diameter 1 to 1 The method according to any one of claims 1 to 4, wherein the thickness is about 100 nm.

11. The method according to claim 1, wherein the precipitation height of titanium oxide formed on the surface of the nanoporous substrate and the inner surface of the pores is about 0.2 to 10 nm.

12. The production method according to claim 4, wherein about 10 to 500 g of the nanoporous substrate is used per 1 L of an aqueous solution containing a fluorotitanium complex compound and a fluoride ion scavenger.

1 3. Claim that the pore size distribution of the raw material nanoporous substrate and the pore size distribution of the photocatalytically active nanoporous material after the formation of titanium oxide are substantially unchanged. Item 5. The production method according to any one of Items 1 to 4.

1 4. A photocatalytically active nanoporous material produced by the production method according to any one of claims 1 to 13.

15. The photocatalytically active nanoporous material according to claim 14, which has photocatalytic activity in visible light (wavelength: about 500 to 700 nm).

1 6. A photocatalytically active nanoporous material in which a titanium oxide having a deposition height of 0.2 to about L O nm is formed on the surface of the nanoporous substrate and the inner surface of the pores.

17. The photocatalytically active nanoporous material according to claim 16, which has photocatalytic activity in visible light (wavelength: about 500 to 700 nm).

18. The photocatalytically active nanoporous material according to claim 16, wherein the content of titanium oxide is about 0.01 to 20% by weight based on the total weight of the photocatalytically active nanoporous material.

. 1 9 BET specific surface area of 5 0 to:. L is 0 0 0 m ² Zg about a 1 0 ml Z g about 3 to total pore volume of 0.5 by the MP method, pore size 1: 17. The photocatalytically active nanoporous material according to claim 16, which has a L of about 100 nm.

20. Further, the obtained photocatalytically active nanoporous material is chemically or physically treated to remove titanium oxide formed on the surface of the photocatalytically active nanoporous material. The method according to any one of claims 1 to 13.

21. The method according to claim 20, wherein the chemical treatment is a treatment of bringing the obtained photocatalytically active nanoporous material into contact with an acidic liquid without degassing.

22. A photocatalytically active nanoporous material produced by the production method according to claim 20 or 21.

23. Contains the photocatalytically active nanoporous material according to any one of claims 14 to 19. Filter to do.

24. A wall material containing the ¾M medium-active nanoporous material according to any one of claims 14 to 19 and 22.

25. A fiber containing the photocatalytically active nanoporous material according to claim 22.