JP2004105958A - Method for manufacturing porous photocatalyst composite powder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a porous photocatalyst composite powder capable of being simply manufactured by few manufacturing steps without generating a harmful exhaust gas. <P>SOLUTION: The manufacturing method is characterized in that a porous photocatalyst composite powder precursor fixed with a photocatalyst precursor to a porous inorganic powder precursor is subjected to heat treatment in a range of 150-500°C. The porous inorganic powder precursor is a metal oxide-hydroxide or a metal hydroxide. <P>COPYRIGHT: (C)2004,JPO

Description

The present invention relates to a method for producing a porous photocatalyst composite powder in which a photocatalyst is supported on a porous inorganic powder. According to the production method of the present invention, a porous photocatalyst composite powder can be produced at low cost, easily and without generating harmful exhaust gas. The porous photocatalyst composite powder obtained by such a method can be used in various fields requiring a water purification effect, a deodorizing effect, a harmful gas decomposition effect, an antibacterial effect, a self-cleaning effect, and the like.

(4) Since photocatalysts generate strong oxidation-reduction power (photocatalytic reaction) when irradiated with light, they have recently been attracting attention in many industrial fields, and their applications are constantly expanding. For example, photocatalysts can decompose pollutants using clean light energy, have high redox ability, and remove harmful gas phase substances (NOx, SOx, formaldehyde, etc.), fungi, bacteria, etc. Since it can be decomposed, it is applied to many products such as antibacterial tiles, air purifiers, purification of domestic wastewater and industrial wastewater. At present, environmental issues on a global scale, such as an increase in carbon dioxide and global warming, air pollution by NOx and SOx, and water pollution of rivers by harmful substances, are seriously questioned. Is attracting attention.

When using photocatalyst powder, in order to facilitate separation operation and handling from the reaction treatment system, the photocatalyst powder is formed into a molded body, or the photocatalyst powder is fixed to a support such as a glass plate, a coating film, or a fiber. May be used. When fixing to a coating film, a photocatalyst powder is blended with the paint. In addition, when the photocatalyst powder is mixed and fixed to the fiber, a method of mixing the fiber and the photocatalyst powder, followed by spinning or papermaking is adopted.

However, when a photocatalyst powder, for example, titanium oxide fine particles is used by dispersing it in a support such as a glass plate, a coating film, or a fiber, the bonding force between the titanium oxide fine particles is large, so that the particles are aggregated to form secondary particles. There is a problem that it is difficult to uniformly disperse in a support such as a glass plate, a coating film and a fiber.
Further, when a photocatalyst is fixed to a support such as a glass plate, a coating film, and a fiber, there is a problem that the support is decomposed by a photocatalytic reaction.

In order to prevent secondary agglomeration of the photocatalyst powder and suppress the decomposition of the organic binder and the fiber serving as the support, the photocatalyst is fixed to the surface of the base particles having no photocatalytic activity. .
For example, Patent Literature 1 describes a method of producing porous apatite particles having an adsorption ability, coating the surface with titania sol, and heating the coated powder to produce a porous photocatalytic composite powder. . However, in such a method for producing a porous photocatalyst composite powder, a step of producing porous apatite particles is required separately before coating the titania sol. Further, since the porous particles have lower mechanical strength than the particles having no pores, there is a possibility that the porous particles may be broken by mechanical stirring in a stage before coating the titanium oxide.

JP-A-2001-270709

In order to solve the above-mentioned problems, the present invention has conducted intensive studies. As a result, the photocatalyst composite powder precursor in which the photocatalyst precursor is fixed to the porous inorganic powder precursor is subjected to heat treatment, thereby reducing the number of production steps. The porous particles can be easily produced without loss of the porous particles, and also have excellent dispersibility even when fixed to the support, can suppress the formation of secondary particles, suppress the deterioration of the support itself, and It has been found that a porous photocatalyst composite powder having excellent photocatalytic ability can be produced.

That is, the present invention has the following features.
1. A method for producing a porous photocatalyst composite powder, comprising subjecting a porous photocatalyst composite powder precursor obtained by fixing a photocatalyst precursor to a porous inorganic powder precursor to a heat treatment in the range of 150 ° C to 500 ° C.
2. The porous inorganic powder precursor is a metal oxide hydroxide or a metal hydroxide. 3. The method for producing a porous photocatalyst composite powder according to item 1.
3. The porous inorganic powder precursor is characterized in that it is an oxidized hydroxide or hydroxide containing one or more metal elements selected from iron, cobalt, nickel, manganese, titanium, vanadium, copper, and zinc. 1. Or 2. 3. The method for producing a porous photocatalyst composite powder according to item 1.
4.1. ~ 3. By mixing the porous photocatalyst composite powder produced by the production method according to any one of the above, a metal salt solution, and a reducing agent, and mechanically alloying at 0 ° C to 100 ° C, thereby supporting the metal together with the photocatalyst. A method for producing a porous photocatalyst composite powder, comprising producing a porous photocatalyst composite powder.
5. 3. The metal salt solution is a solution containing a metal salt of at least one metal selected from the group consisting of palladium, platinum, rhodium, ruthenium, nickel, iron, copper, silver, gold and zinc. PROCESS FOR PRODUCING POROUS PHOTOCATALYST COMPOSITE POWDER

According to the production method of the present invention, a porous photocatalyst composite powder can be produced at low cost, simply, and without generating harmful exhaust gas. Moreover, the porous photocatalyst composite powder obtained by such a method can be used in various fields that require a water purification effect, a deodorizing effect, a harmful gas decomposition effect, an antibacterial effect, a self-cleaning effect, and the like.

Hereinafter, the present invention will be described in detail based on the best mode for carrying out the invention.

(Photocatalyst precursor)
The photocatalyst precursor used in the present invention generates a photocatalyst such as titanium oxide, zinc oxide, zirconium oxide, and tungsten oxide by heating or the like. Examples of such a photocatalyst precursor include, for example, a basic compound containing titanium, zinc, zirconium, tungsten, or the like, or a compound generated by a hydrolyzate of a metal alkoxide. Examples include a basic compound or a compound generated by a hydrolyzate of a metal alkoxide. Specifically, titania sol that gives anatase type titanium oxide as a photocatalyst precursor, basic zinc compound that gives zinc oxide, and the like are preferable examples.

(Porous inorganic powder precursor)
As the porous inorganic powder precursor of the present invention, a precursor that produces a porous inorganic powder by a dehydration treatment such as heating is used. As a porous inorganic powder precursor that produces such a porous inorganic powder, for example, when the porous inorganic powder is a metal oxide, a metal oxidized water having the same metal composition as the metal oxide is used. It is preferable to use an oxide or a metal hydroxide. In such a metal oxide hydroxide or metal hydroxide, dehydration pores are formed on the surface of the powder containing the metal oxide hydroxide or metal hydroxide during the dehydration reaction. Can be obtained.

Examples of the metal oxide hydroxide or metal hydroxide include, for example, iron, cobalt, nickel, manganese, titanium, vanadium, copper, and an oxide hydroxide or hydroxide containing one or more metal elements selected from zinc. And an oxide hydroxide or hydroxide containing at least one metal element selected from iron, titanium and zinc. Further, a metal oxide or a metal hydroxide obtained by partially substituting at least one metal selected from the group consisting of alkaline earth metals, Al, Si, Zn, Bi, Y, and lanthanoids can also be used. By changing the content of the substitution element, the color, the magnetic characteristics, and the like can be controlled.

Among these metal oxide hydroxides or metal hydroxides, inexpensive, strong hiding power, does not affect the environment, and as a semiconductor having an electron supply ability to the photocatalyst, iron oxide hydroxide, Iron hydroxide or the like can be used, and in particular, iron oxide hydroxide having excellent chemical stability can be more preferably used.

As iron oxide hydroxide, α-FeOOH (goethite), β-FeOOH (akaganeite), γ-FeOOH (lepidocrotite), δ-FeOOH, and the like can be used. FeOOH, β-FeOOH, and γ-FeOOH can be more preferably used. A composite oxide hydroxide in which at least one metal element selected from Al, Si, Zn, Ca, Sr, Ba, Co, Ni, Y, and lanthanoid is partially substituted for these iron oxide hydroxides can also be used. By changing the content of the substitution element, it is possible to control the color, magnetic properties, and the like of the composite oxide generated by the thermal dehydration reaction.

As a method for producing iron oxyhydroxide, known methods can be mentioned. For example, Japanese Patent Publication No. 39-5610, Japanese Patent Publication No. 51-21639, Japanese Patent Publication No. 51-12318, Japanese Patent Publication No. 53-31480, and Japanese Patent Publication No. 4-42329. JP-B-6-42889, JP-B-6-42900, JP-B4-22233, JP-B4-22233, JP-B-54-7292, JP-B-59-17050, JP-A-9-165531, JP-A-1-182363, JP-A-3-163172, JP-B-46-39681, JP-B-53-4078, JP-A-3-50119, H.C. Christensen and and A. N. Christensen, Acta Chemica Scandinavicica, Series A 32 (1978) 87. A. L. MacKay, Mineralographic Magazine and Journal of the Mineralographic Society 32 (1960) 545. And the like. In addition, commercially available products can also be used.

Incidentally, by appropriately setting the particle diameter, particle diameter distribution, particle shape and the like of these metal oxide hydroxides and metal hydroxides, the particle diameter of the porous inorganic powder generated by the heat dehydration reaction, the particle diameter distribution, Particle shape and the like can be controlled.

(Method for producing porous photocatalyst composite powder)
The porous photocatalyst composite powder of the present invention is obtained by heat-treating a photocatalyst composite powder precursor obtained by fixing a photocatalyst precursor to a porous inorganic powder precursor at a temperature in the range of 150 ° C to 500 ° C. In such a production method, the step of producing the porous inorganic powder from the porous inorganic powder precursor and the step of producing the photocatalyst from the photocatalyst precursor can be performed simultaneously, so that the production steps can be shortened.
In addition, in the step of fixing the photocatalyst precursor to the porous inorganic powder precursor, no porous powder is used, so that the powder is less likely to be damaged by the mechanical stirring involved in the fixing step.

Furthermore, by using metal oxide hydroxide or metal hydroxide as the porous inorganic powder precursor, exhaust gas generated in the manufacturing process is substantially dehydrated by metal oxide hydroxide or metal hydroxide. Since only water is generated, the handling of exhaust gas is easy and safe, which is preferable.

方法 Examples of a method for fixing the photocatalyst precursor to the porous inorganic powder precursor include a precipitation method and a sputtering method. In the precipitation method, a metal catalyst is precipitated as a hydroxide by neutralization in a solution in which a porous inorganic powder precursor is mixed, or a photocatalyst precursor is gradually dissolved by means such as hydrolysis of a metal alkoxide. This is a method of forming on the surface of a porous inorganic powder precursor.

量 The amount of the photocatalyst precursor fixed to the porous inorganic powder precursor is preferably 0.1 to 30 wt% based on the weight of the inorganic compound contained in the porous inorganic powder precursor. When the weight of the photocatalyst precursor is smaller than this range, the effect as the photocatalytic ability is reduced, and when trying to fix the weight of the photocatalyst precursor larger than this range, a photocatalyst that is not fixed to the surface of the porous inorganic powder occurs Therefore, it is not possible to produce only the porous photocatalyst composite powder of the present invention.

(4) By heating the porous inorganic powder precursor to which the photocatalyst precursor is fixed at 150 ° C. to 500 ° C., a porous composite powder supporting the photocatalyst is obtained. When the heat treatment temperature is lower than 150 ° C., the dehydration reaction does not easily occur, and it is difficult to obtain a porous photocatalyst composite powder. When the heat treatment temperature is higher than 500 ° C., sintering proceeds, and the specific surface area of the porous inorganic powder decreases. Since a solid solution is formed by a solid phase reaction between the photocatalyst and the porous inorganic powder, it is difficult to obtain a composite powder having excellent adsorption ability and photocatalytic ability.

例 One example of a preferred method for producing the porous photocatalyst composite powder in the present invention will be specifically described below.

(Method for producing porous iron oxide powder to which anatase-type titanium oxide is fixed)
The iron oxide hydroxide powder is suspended in an alcohol solvent and stirred, and then an organic titanium compound is added and further stirred. By adding hydrogen peroxide to this suspension and heating it at 40 ° C. to 100 ° C., preferably 60 ° C. to 80 ° C. with stirring, hydrogen peroxide is gradually decomposed, and then the organic titanium compound is hydrolyzed. As a result, a titania sol is generated, and an iron oxide hydroxide powder in which the titania sol is uniformly fixed on the powder surface is obtained. At this time, if the heat treatment temperature is lower than 40 ° C., a gel is not easily formed, and if the heat treatment temperature is higher than 100 ° C., hydrogen peroxide is rapidly decomposed, and the titanium oxide fine particles in the gel are aggregated. It is difficult to obtain porous iron oxide powder fixed to the surface.

The amount of the added hydrogen peroxide solution is preferably 2 to 10 times the weight of the precipitated titanium oxide. If it is less than 2 times, the hydrolysis of the organic titanium compound does not proceed efficiently, and if it is more than 10 times, the hydrolysis proceeds rapidly, so that the titanium oxide fine particles easily aggregate and the titanium oxide is deposited on the particle surface. It is difficult to obtain a uniformly adhered porous iron oxide powder. The heating and stirring time of the suspension to which hydrogen peroxide is added is preferably about 0.1 to 24 hours, and more preferably about 0.5 to 12 hours.

As the alcohol solvent, a water-soluble organic solvent such as methanol, ethanol, 1-propanol, 2-propanol, and t-butanol is preferable.
Further, as the organic titanium compound, it is preferable to use a titanium alkoxide such as titanium ethoxide, titanium isopropoxide, and titanium butoxide. Inorganic salts such as titanium chloride and titanium sulfate can be used. In this case, if the inorganic anions and their salts coexisting in the solution remain in the sol, it is necessary to remove them. In this regard, the use of titanium alkoxide is preferable since inorganic ions serving as impurities are not generated.

The titania sol thus obtained is uniformly fixed on the powder surface, and the iron oxide hydroxide powder is subjected to a heat treatment at 150 ° C. to 500 ° C. to cause a dehydration reaction of the iron oxide hydroxide to cause anatase It is possible to obtain a porous iron oxide powder having titanium oxide fixed thereon.
At a temperature lower than 150 ° C., dehydration reaction of iron oxide hydroxide does not easily occur, and it is difficult to obtain anatase type titanium oxide having good crystallinity. At a temperature higher than 500 ° C., rutile-type titanium oxide having low photocatalytic activity comes to be produced, and it is difficult to obtain the photocatalyst composite iron oxide powder of the present invention.
The heat treatment time is not particularly limited, but is preferably 15 minutes to 3 hours (preferably 30 minutes to 2 hours). The heat treatment can be performed in the air or under a reducing atmosphere.

(Method for producing porous iron oxide powder to which zinc oxide is fixed)
The iron oxide hydroxide powder is suspended in distilled water or ion-exchanged water and stirred, and then a water-soluble zinc compound is added and further stirred. By neutralizing the suspension by dropwise addition of an alkaline solution, the basic zinc compound is gradually precipitated, and iron oxide hydroxide powder having the basic zinc compound fixed thereon is obtained.
The obtained iron oxide hydroxide powder to which the basic zinc compound is fixed is heated at 150 to 400 ° C. to cause a dehydration reaction of the iron oxide hydroxide. A fixed porous iron oxide powder can be obtained.
By subjecting the basic zinc compound to a heat treatment at 150 ° C. or higher, zinc oxide can be produced. When heated at 400 ° C. or higher, a composite oxide containing zinc and iron is generated. Therefore, heat treatment at 400 ° C. or lower is necessary to obtain porous iron oxide to which zinc oxide is fixed.
The heat treatment time is not particularly limited, but is preferably 15 minutes to 3 hours (preferably 30 minutes to 2 hours). The heat treatment can be performed in the air or under a reducing atmosphere.

The water-soluble zinc compound used in the production method of the present invention is not particularly limited, but a water-soluble zinc compound such as zinc chloride, zinc sulfate, zinc nitrate, and zinc acetate is preferably used.
As the alkaline solution, an aqueous solution of sodium hydroxide, lithium hydroxide, ammonium hydroxide, ammonium, sodium carbonate or the like is suitably used.

で は In the present invention, it is preferable that a metal is further supported on the porous photocatalyst composite powder produced as described above. By carrying a metal, it is possible to decompose harmful substances with high efficiency, and it is possible to improve environmental purification effects such as water purification, deodorization, air pollution purification, and photocatalytic effects such as antibacterial effects. It is considered that this effect is obtained because, of the electrons and holes generated from the photocatalyst irradiated with light, the electrons move to the metal, so that the recombination of electrons and holes hardly occurs.

(metal)
Examples of the metal include palladium, platinum, rhodium, ruthenium, iron, nickel, copper, silver, gold, zinc, and the like, and one or more of these can be used in combination. In the present invention, palladium, platinum, copper, silver, and gold are particularly preferable, and platinum, silver, and gold are more preferable.
The average particle diameter of the metal is preferably smaller than the average particle diameter of the porous inorganic powder. Although the average particle diameter of the metal is not particularly limited, it is usually preferably 0.005 to 0.25 μm, and more preferably 0.01 to 0.2 μm.
The weight of the metal supported on the porous inorganic powder is desirably 0.01 to 10 wt%, preferably 0.1 to 9.0 wt%. When the weight of the metal is smaller than this range, the photocatalyst is hardly improved. If the weight of the metal is larger than this range, the irradiation of light to the photocatalyst particles is inhibited by the metal, and the photocatalytic effect may be reduced.

As a method of supporting a metal on the porous photocatalyst composite powder, for example, a method of obtaining a porous photocatalyst powder, a metal salt solution, and a reducing agent at 0 ° C to 100 ° C by mechanical alloying is preferable. . In such a production method, compared with known methods such as electroless plating, physical vapor deposition, and mechanical alloying, the metal can be uniformly supported on the surface of the porous inorganic powder, and the waste liquid discharged This is preferable because a relatively small amount of equipment can be used and a relatively inexpensive apparatus can be used.

In the mechanical alloying according to the present invention, a photocatalyst composite powder in which a photocatalyst is supported on a porous inorganic powder, a metal salt solution, and a reducing agent are mixed and mechanically pulverized. At the same time as the metal particles are precipitated, the metal fine particles are uniformly dispersed on the surface of the photocatalyst composite powder by mechanical energy, and then fixed, so that a photocatalyst composite powder supporting a metal can be produced. According to such a manufacturing method, it is advantageous in terms of cost because it can be manufactured in a short time, and the metal can be more uniformly attached to the surface of the porous inorganic powder, which is preferable.
The mechanical pulverization is performed by a jet method using a jet pulverizer, a pin mill, a disk mill, a hammer mill, a hammer method using an axial flow type / vortex type mill, a classifier combined mill, etc., a ball mill, a media type pulverizer such as a media stirring mill. And a mill method using a roller mill or the like.
In the present invention, it is particularly desirable to use a media-type pulverizer such as a ball mill or a media stirring mill that can continuously mix and pulverize the solid raw material in a certain space during the reaction time when the compound is generated.
Balls used for ball mills and media stirring mills, and grinding media are not limited as long as they have appropriate hardness and specific gravity. For example, steel, glass, zirconia, agate, alumina, tungsten carbide, chrome steel, silicon nitride, plastic Those having a composition such as polyamide can be used.
In the present invention, those having a chemically stable composition such as glass, zirconia, and agate are particularly preferable.
Also, in order to prevent overheating of the reaction system due to frictional heat of mechanical mixing and pulverization, a certain cooling time may be inserted during the mechanical mixing and pulverization to allow natural air cooling. A device may be incorporated.
The mechanical mixing and pulverization may be performed continuously or in a batch system. The production time is not particularly limited, but is usually about 10 minutes to 500 minutes.

金属 The metal salt solution of the present invention is used for reacting with a reducing agent described later to precipitate a metal. The solute of such a metal salt solution is not particularly limited, and includes, for example, at least one metal element selected from palladium, platinum, rhodium, ruthenium, iron, nickel, copper, silver, gold, zinc, and the like. Are preferably used, and those containing palladium, platinum, copper, silver, and gold are particularly preferable, and those containing platinum, silver, and gold are more preferable because they are stable. In the present invention, it is desirable to use at least one or more metal salts selected from nitrates, chlorides, acetates, sulfates, acetylacetonates and ammine complexes of such metal elements.

The solvent for the metal salt solution is not limited as long as it can stably dissolve the metal salt. Water, methanol, ethanol, n-propanol, alcohols such as isopropanol, ethylene glycol, ethylene glycol monomethyl ether, propylene glycol, propylene In addition to glycol derivatives such as glycol monomethyl ether, diethylene glycol monoethyl ether, and ethylene glycol monoethyl ether acetate, esters, ketones, ethers, n-hexane, n-pentane, n-octane, n-nonane, and n-decane , N-undecane, n-dodecane, terpin oil, aliphatic hydrocarbons such as mineral spirits, aromatic hydrocarbons such as toluene, xylene and solvent naphtha, and others, ethyl acetate, butyl acetate, methyl ethyl Tons, and methyl isobutyl ketone.
Further, the pH of the metal salt solution may be appropriately adjusted in the range of 0 to 14 using a known base or acid. By adjusting the pH, a stable metal salt solution can be prepared. Examples of the base include sodium hydroxide, potassium hydroxide, calcium hydroxide, potassium hydroxide, ammonia, urea, amines and the like. Examples of the acid include hydrochloric acid, sulfuric acid, acetic acid, nitric acid, citric acid, and formic acid.

The reducing agent functions to react with the metal salt solution to precipitate a metal. Examples of the reducing agent include hydrazine, formaldehyde, and polysaccharides such as glucose. In particular, it is preferable to use a highly safe and inexpensive polysaccharide such as glucose.
The mixing amount of the reducing agent may be generally about 25 to 400 wt% with respect to the metal element.

(Porous photocatalyst composite powder)
In the porous photocatalyst composite powder obtained by the production method of the present invention, the photocatalyst is present on the surface of the porous inorganic powder. The photocatalyst in the present invention is required to be present on the surface of the porous inorganic powder, but may be present on the inner wall of the pore, or partially present on the surface of the porous inorganic powder other than the pore. It may be.

Such a porous photocatalyst composite powder preferably has a particle diameter of 0.01 to 100 µm (preferably 0.1 to 10 µm). When the particle diameter is in such a range, the coloring power and hiding power as a pigment are large, and the pigment is easily dispersed.

The porous photocatalyst composite powder of the present invention has excellent dispersibility, can suppress the formation of secondary particles, suppresses deterioration of the support itself, and has excellent photocatalytic ability even when fixed to a support. ing. When a metal oxide containing at least one metal selected from iron, cobalt, nickel, manganese, titanium, vanadium, copper, zinc and the like is used, it is non-polluting, chemically stable, and capable of shielding ultraviolet rays. It is possible to obtain a porous photocatalyst composite powder which has a large absorption capacity, a high hiding property, and is effective as a pigment having a novel hue.

The photocatalytic composite powder preferably has a specific surface area measured by the BET method of 40 m ² / g or more. When the specific surface area is in such a range, adsorption and decomposition as a photocatalyst can be efficiently advanced.

実 施 Examples and comparative examples are shown below to further clarify the features of the present invention, but the present invention is not limited to these examples.

(Measuring method)
1. The crystal structure of the composite powder was analyzed with an X-ray diffractometer (RINT-1100, manufactured by Rigaku Corporation).
2. The particle shape and particle diameter of the composite powder were observed with an electron microscope (JSM-5310, manufactured by JEOL Ltd.).
3. The specific surface area of the composite powder was measured by a BET method using a surface area measuring device P-700 manufactured by Shibata Scientific Instruments Co., Ltd. with dead volume measurement gas: helium and adsorption gas: nitrogen.
4. Evaluation test of photocatalytic activity In advance, the composite powder was dispersed in acrylic silicone resin (solid content 50%) and red-downed with the same resin to obtain 72 parts by weight of acrylic silicone resin (solid content 50%). A base paint of 10 parts by weight of the body and 18 parts by weight of the thinner was obtained. 10 parts by weight of a curing agent is mixed with 100 parts by weight of the base paint, and 0.25 mm is applied to an aluminum plate (70 mm × 150 mm × 0.8 mm) (JIS H 4000) previously coated with a white acrylic resin paint. It was applied with a thickness and cured for 24 hours to prepare a test body. This test body was hung on a glass top plate (thickness: 5 mm) and fixed in a reaction vessel. Next, a commercially available ammonia gas was passed, and when the ammonia concentration in the reaction vessel became stable at 1%, the ventilation was stopped, UV irradiation was started, and the decomposition rate of ammonia was measured after 40 minutes. Note that a 6 W UV lamp was used as a light source, and irradiation was performed from above the test specimen by 5 cm.
5. Coating film deterioration test Specimens were prepared in the same manner as in the photocatalytic activity evaluation test. The specular glossiness (measurement angle: 60 degrees) (initial glossiness) of the prepared specimen was measured with a glossiness meter (Micro Trigloss, manufactured by BYK Japan KK). Further, the test specimen was attached to a sunshine weather meter (manufactured by Suga Test Instruments Co., Ltd.), the glossiness after exposure for 500 hours was measured, and the gloss retention was calculated from the initial glossiness and the glossiness after exposure for 500 hours. The gloss retention is a value calculated by the following equation.
Gloss retention (%) = gloss after exposure for 500 hours / initial gloss × 100

(Example 1)
20 g of needle-shaped α-FeOOH (major axis length: 1 μm) was suspended in 200 ml of ethanol, and 1.8 g of titanium butoxide was added. After stirring and mixing for 60 minutes, 30 ml of 30% aqueous hydrogen peroxide was added and stirred. Thereafter, the mixture was stirred at 70 ° C. for 6 hours to cause hydrolysis. The ethanol-water solvent was removed by filtration and then dried to obtain α-FeOOH coated with titania sol. Next, the α-FeOOH coated with the titania sol was heat-treated in air at 300 ° C. for 2 hours to obtain a reddish-brown anatase-type titanium dioxide-α-Fe ₂ O ₃ composite powder.
As a result of observation with an electron microscope, it was found that the composite powder had a porous acicular shape (major axis length 1 μm).
In addition, as shown in the X-ray diffraction pattern of FIG. 1, it was confirmed that anatase type titanium dioxide was generated on α-Fe ₂ O ₃ .
The result of the measurement of the specific surface area by the BET method was 97.2 m ² / g.
The ammonia decomposition rate was 85%, indicating that the decomposition of ammonia was remarkable, indicating that the composition had excellent photocatalytic activity.
The initial glossiness was 84.3, and the dispersibility was excellent. The gloss retention was also kept at 100%, and the weather resistance was excellent.

(Example 2)
It was produced in the same manner as in Example 1 except that needle-like γ-FeOOH (major axis length 0.5 μm) was used instead of α-FeOOH. A yellow-brown composite powder having an average particle size of 0.5 μm was obtained. As shown in the X-ray diffraction pattern of FIG. 2, it was confirmed that anatase type titanium dioxide was formed on γ-Fe ₂ O ₃ of the substrate. The result of the measurement of the specific surface area by the BET method was 105.1 m ² / g.
The ammonia decomposition rate was 87%, indicating that the decomposition of ammonia was remarkable, indicating that the composition had excellent photocatalytic activity. The initial glossiness was 85.1, and the dispersibility was excellent. The gloss retention was also kept at 100%, and the weather resistance was excellent.

(Example 3)
20 g of α-FeOOH having a needle-like shape (major axis length 1 μm) was suspended in 1000 ml of ion-exchanged water, and 2 g of zinc nitrate hexahydrate was added. After stirring and mixing for 60 minutes, 500 ml of 2N sodium hydroxide was added dropwise and stirred. After removing the solvent by filtration, drying was performed to obtain α-FeOOH coated with zinc hydroxide.
Next, a zinc oxide-α-Fe ₂ O ₃ composite powder having an average particle diameter of 1 μm is obtained by heat-treating α-FeOOH coated with zinc hydroxide in air at 300 ° C. for 2 hours. Was. As shown in the X-ray diffraction pattern of FIG. 3, it was confirmed that anatase type titanium dioxide was formed on α-Fe ₂ O ₃ of the substrate. The result of the measurement of the specific surface area by the BET method was 48.2 m ² / g.
The decomposition rate of ammonia was 66%, indicating that the decomposition of ammonia had occurred to some extent, and that it had photocatalytic activity. The initial glossiness was 84.0, and the dispersibility was excellent. The gloss retention was also kept at 100%, and the weather resistance was excellent.

(Example 4)
25% ammonia water was added to 10.0 g of the titanium dioxide-α-Fe ₂ O ₃ composite powder obtained in Example 1, 0.026 g of silver nitrate, and 10.0 g of distilled water to adjust the pH to 14, followed by glucose. 2.5 g were mixed and mixed and pulverized using a zirconia bead (diameter 3 mm) and a planetary ball mill (manufactured by Fritsch) at a rotation speed of 450 rpm at 25 ° C. for 150 minutes. Thereafter, solid-liquid separation was performed, followed by washing and drying at 100 ° C. for 2 hours to obtain a slightly dark brownish mahogany silver-titanium dioxide-αFe ₂ O ₃ composite powder.
When observed with an electron microscope, a silver-titanium dioxide-αFe ₂ O ₃ composite powder having a needle-like shape with a major axis length of about 1.1 μm was observed. The specific surface area was 102.8 m ² / g. As a result of analyzing the obtained X-ray diffraction pattern, it was confirmed that silver was generated together with the α-Fe ₂ O ₃ composite powder and the anatase type titanium dioxide.
The ammonia decomposition rate was 89%, indicating that ammonia decomposition was remarkable, indicating that the composition had excellent photocatalytic activity. The initial glossiness was 83.5, and the dispersibility was excellent. The gloss retention was also kept at 100%, and the light resistance was excellent.

3 is a powder X-ray diffraction pattern of the powder produced in Example 1. 5 is a powder X-ray diffraction pattern of the powder produced in Example 2. 6 is a powder X-ray diffraction pattern of the powder produced in Example 3.

Claims (5)

(4) A method for producing a porous photocatalyst composite powder, which comprises heat-treating a porous photocatalyst composite powder precursor in which a photocatalyst precursor is fixed to a porous inorganic powder precursor at a temperature in the range of 150 ° C to 500 ° C. 方法 The method for producing a porous photocatalyst composite powder according to claim 1, wherein the porous inorganic powder precursor is a metal oxide hydroxide or a metal hydroxide. The porous inorganic powder precursor is characterized in that it is an oxidized hydroxide or hydroxide containing one or more metal elements selected from iron, cobalt, nickel, manganese, titanium, vanadium, copper, and zinc. A method for producing the porous photocatalyst composite powder according to claim 1 or 2. A porous photocatalyst composite powder produced by the production method according to any one of claims 1 to 3, mixed with a metal salt solution, and a reducing agent, and mechanically alloyed at 0 ° C to 100 ° C to form a photocatalyst. A method for producing a porous photocatalyst composite powder, which comprises producing a porous photocatalyst composite powder carrying a metal. The metal salt solution is a solution containing a metal salt of at least one metal selected from the group consisting of palladium, platinum, rhodium, ruthenium, nickel, iron, copper, silver, gold and zinc. 4. The method for producing a porous photocatalyst composite powder according to 4.

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