JP2006021991A - Method for producing metal doped titanium oxide particulate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a metal doped titanium oxide particulate having photocatalyst activity even in the visible light range with a higher production efficiency and more easily compared with conventional methods such as the sol-gel method, the solid-state reaction method, the ion-implantation method or the like. <P>SOLUTION: The method for producing the metal doped titanium oxide particulate comprises a step of producing a titanium-containing water solution (A) by mixing at least one kind of titanium compound selected from the group consisting of metallic titanium, a hydrolyzable titanuim compound, a low condensate of a hydrolyzable titanium compound, titanium hydroxide, metatitanic acid, and a low condensate of titanium hydroxide with oxygenated water and a step of separating the metal doped titanium oxide particulate from a solution which is produced by heat-treating the water solution (A) in the presence of a salt (B) of a metal other than titanium and a stabilizer (C) and drying it. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for producing metal-doped titanium oxide fine particles that are simple and excellent in productivity.

  In recent years, use of a titanium oxide photocatalyst has been made in various fields. In particular, the application to the purification of living environment such as air purification and water purification, and the application of a self-cleaning function utilizing a high level of hydrophilizing action are remarkable.

  Photocatalytic action of titanium oxide has an effective wavelength range in the ultraviolet range, but only about 4% of the sun's rays are ultraviolet, and photocatalytic action from the ultraviolet range to the visible light range for effective utilization under sunlight. Research is being actively conducted to expand the effective wavelength range.

  As one effective method, there is a method of doping titanium oxide having photocatalytic activity with nitrogen or a specific metal. It is known that an impurity level is generated in a semiconductor by doping a specific metal in the semiconductor, and a new absorption band is generated in the absorption band of the semiconductor, and this is applied (for example, Patent Document 1). , See Patent Document 2).

  As a method for doping a metal, a sol-gel method, a solid-phase reaction method, an ion implantation method, etc. are generally known. However, in the sol-gel method, the concentration of titanium in the reaction system is uniform in order to cause hydrolysis and polymerization reaction uniformly. Is generally limited to a low concentration of 1% or less, and there are problems such as low production efficiency and troublesome removal of decomposition products. On the other hand, in the solid phase reaction method, since the reaction is caused to occur uniformly, a long time reaction is required at a high temperature, and there is a problem that productivity is lacking. Further, in the ion implantation method, metal ions are implanted into titanium oxide with a large energy, so that a large facility is required.

JP 2000-140636 A JP-A-11-255514

  An object of the present invention is to provide a method for producing metal-doped titanium oxide fine particles, which has higher production efficiency and is easier than conventional methods such as a sol-gel method, a solid phase reaction method, and an ion implantation method. Furthermore, the objective of this invention is providing the metal dope titanium oxide microparticles | fine-particles manufactured by the said method, and a photocatalyst body using the same.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors have found that a titanium salt-containing aqueous liquid obtained by mixing a specific titanium compound with a hydrogen peroxide solution is doped with a metal salt and stabilizer. It has been found that metal-doped titanium oxide fine particles can be easily obtained simply by adding and heat-treating this, and the present invention has been completed.

  Thus, the present invention provides at least one titanium selected from the group consisting of metal titanium, hydrolyzable titanium compounds, hydrolyzable titanium compound low condensates, titanium hydroxide, metatitanic acid, and titanium hydroxide low condensates. From a solution obtained by heat-treating a titanium-containing aqueous liquid (A) obtained by mixing a compound with aqueous hydrogen peroxide in the presence of a metal salt (B) other than titanium and a stabilizer (C). The present invention relates to a method for producing metal-doped titanium oxide fine particles, wherein metal-doped titanium oxide fine particles are obtained by separation and drying.

  Moreover, this invention relates to the metal dope titanium oxide microparticles | fine-particles obtained using said manufacturing method.

  Furthermore, the present invention relates to a photocatalyst having photocatalytic activity even in the visible light region, which is obtained using the above metal-doped titanium oxide fine particles.

  In the method for producing metal-doped titanium oxide fine particles of the present invention, a salt of a metal (dopant metal) to be doped and a stabilizer are added to a titanium-containing aqueous liquid obtained by mixing a specific titanium compound with a hydrogen peroxide solution. By adding and heating this, it is possible to easily produce fine particles of metal-doped titanium oxide having photocatalytic activity even in the visible light region at a relatively low temperature in a short time, producing harmful by-products. Therefore, the load on the environment is small, the dopant metal can be uniformly introduced into the titanium oxide fine particles, and the introduction amount of the dopant metal can be easily controlled.

  The method for producing metal-doped titanium oxide fine particles of the present invention comprises metal titanium, a hydrolysable titanium compound, a low condensate of a hydrolysable titanium compound, titanium hydroxide, metatitanic acid, and a low condensate of titanium hydroxide. A titanium-containing aqueous liquid (A) obtained by mixing at least one titanium compound selected from the group consisting of hydrogen peroxide and water in the presence of a metal salt (B) other than titanium and a stabilizer (C). By performing the treatment, metal-doped titanium oxide fine particles are produced.

Titanium-containing aqueous liquid (A)
The titanium-containing aqueous liquid as the component (A) of the present invention is at least one selected from metal titanium, hydrolyzable titanium, hydrolyzable titanium low condensate, titanium hydroxide, metatitanic acid, and titanium hydroxide low condensate. It is an aqueous liquid containing titanium obtained by reacting a seed titanium compound with hydrogen peroxide. As the aqueous liquid, any conventionally known liquid can be appropriately selected and used without particular limitation as long as it is described above.

  The hydrolyzable titanium described above is a titanium compound having a hydrolyzable group that is directly bonded to titanium, and generates titanium hydroxide by reacting with water such as water or water vapor. In hydrolyzable titanium, all of the groups bonded to titanium may be hydrolyzable groups, or one part thereof may be a hydrolyzed hydroxyl group. The hydrolyzable group is not particularly limited as long as it produces titanium hydroxide by reacting with moisture as described above. For example, a lower alkoxyl group or a group that forms a salt with titanium (for example, halogen) Atoms (chlorine, etc.), hydrogen atoms, sulfate ions, etc.).

The hydrolysable titanium containing a lower alkoxyl group as a hydrolyzable group is particularly a tetraalkoxy of the general formula Ti (OR) ₄ (wherein R is the same or different and represents an alkyl group having 1 to 5 carbon atoms). Titanium is preferred. Examples of the alkyl group having 1 to 5 carbon atoms include methyl group, ethyl group, n-propyl group, iso-propyl group, n-butyl group, iso-butyl group, sec-butyl group, and tert-butyl group. Can be mentioned.

  Typical examples of the hydrolyzable titanium having a group capable of forming a salt with titanium as a hydrolyzable group include titanium chloride and titanium sulfate.

  The hydrolyzable titanium low condensate is a low condensate of the above hydrolyzable titanium.

  The condensation degree in the hydrolyzable titanium low condensate or titanium hydroxide low condensate is preferably about 2 to 30, and it is particularly preferable to use a condensation degree within the range of 2 to 10.

  As the titanium-containing aqueous liquid (A), any conventionally known liquid can be used without particular limitation as long as it is an aqueous liquid containing titanium obtained by reacting the above-described titanium compound with hydrogen peroxide. it can. Specifically, the following can be mentioned.

  (1) A titanyl ion hydrogen peroxide complex or an aqueous solution of titanic acid (peroxotitanium hydrate) obtained by adding hydrogen peroxide to a hydrous titanium gel or sol (JP 63-35419 and JP (See 1-224220).

  (2) A liquid for forming a titania film obtained by synthesizing a titanium hydroxide gel produced from an aqueous solution of titanium chloride or titanium sulfate and a basic solution with the action of hydrogen peroxide (JP 9-71418 and JP 10-67516).

  In the titania film forming liquid described above, titanium hydroxide gel called orthotitanic acid is precipitated by reacting titanium chloride or titanium sulfate aqueous solution having a salt forming group with alkali solution such as ammonia or caustic soda. Let Subsequently, the titanium hydroxide gel is separated by decantation using water, washed well with water, further added with hydrogen peroxide, and excess hydrogen peroxide is decomposed and removed, whereby a yellow transparent viscous liquid can be obtained.

  The orthotitanic acid thus precipitated is in a gel state polymerized by polymerization of OH groups or hydrogen bonds, and cannot be used as an aqueous liquid containing titanium as it is. When hydrogen peroxide solution is added to this gel, part of the OH groups are in a peroxidized state and dissolved as peroxotitanate ions, or in a sol state in which the polymer chain is divided into low molecules, resulting in excess excess Hydrogen oxide decomposes into water and oxygen and can be used as an aqueous liquid containing titanium for forming an inorganic film.

  Since this sol contains only oxygen atoms and hydrogen atoms in addition to titanium atoms, when it is changed to titanium oxide by drying or firing, it is substantially unnecessary to remove organic components because only water and oxygen are generated. However, a crystalline titanium oxide film having a relatively high density can be formed.

  (3) Peroxotitanium hydrate is formed by adding hydrogen peroxide to an aqueous solution of inorganic titanium compound such as titanium chloride or titanium sulfate, and then the solution obtained by adding a basic substance is allowed to stand or be heated. Titanium oxide forming solution obtained by forming a precipitate of titanium hydrate polymer, removing at least dissolved components other than water derived from the titanium-containing raw material solution, and then allowing hydrogen peroxide to act on the precipitate (Japanese Patent Laid-Open No. 2000) -247638 and JP 2000-247639).

In the titanium-containing aqueous liquid (A) used in the present invention, it is preferable to use one prepared by adding a titanium compound to hydrogen peroxide water. As the titanium compound, a hydrolyzate containing a group represented by the general formula Ti (OR) ₄ (wherein R is the same or different and represents an alkyl group having 1 to 5 carbon atoms) and becomes a hydroxyl group by hydrolysis. It is preferable to use degradable titanium or a hydrolyzable titanium low condensate from the viewpoint of ease of production, storage stability of the resulting titanium-containing aqueous liquid, and the like.

  The mixing ratio of hydrolyzable titanium and / or its low condensate (hereinafter simply referred to as “hydrolyzable titanium a”) and hydrogen peroxide is 10 parts by weight hydrolyzable titanium a. The hydrogen peroxide solution is preferably in the range of 0.1 to 100 parts by weight, particularly 1 to 20 parts by weight in terms of hydrogen peroxide. If the amount is less than 0.1 parts by weight in terms of hydrogen peroxide, chelate formation is not sufficient and white turbid precipitation occurs. On the other hand, if it exceeds 100 parts by weight, unreacted hydrogen peroxide tends to remain, and dangerous active oxygen is released during storage.

  The concentration of hydrogen peroxide in the hydrogen peroxide solution is not particularly limited, but it is preferably in the range of 3 to 30% by weight from the viewpoint of ease of handling, the solid content of the product liquid related to the coating workability, and the like.

  In addition, the titanium-containing aqueous liquid (A) using hydrolyzable titanium a is obtained by reacting hydrolyzable titanium a with hydrogen peroxide within a reaction temperature range of 1 to 70 ° C. for about 10 minutes to 20 hours. Can be manufactured.

  The titanium-containing aqueous liquid (A) using hydrolyzable titanium a is obtained by reacting hydrolyzable titanium a with hydrogen peroxide water to hydrolyze the hydrolyzable titanium with water to form a hydroxyl group-containing titanium compound. It is presumed that hydrogen peroxide is then coordinated to the generated hydroxyl group-containing titanium compound, and this hydrolysis reaction and coordination by hydrogen peroxide occur at the same time. A chelate solution that is extremely stable and can withstand long-term storage is produced.

  The titanium hydroxide gel used in the conventional manufacturing method is partially three-dimensionalized by Ti—O—Ti bonds, and the titanium-containing aqueous liquid used in the present invention is obtained by reacting this gel with hydrogen peroxide. (A) is essentially different in composition and stability.

Metal salts other than titanium (B)
Examples of the metal salt (B) other than titanium include iron, copper, vanadium, ruthenium, molybdenum, niobium, tantalum, chromium, aluminum, bismuth, erbium, gallium, gatolinium, boromium, indium, lanthanum, manganese, platinum, Examples of the metal salt include rhodium, scandium, samarium, tin, terbium, thulium, tungsten, yttrium, ytterbium, and gymnium. Among them, iron, copper, vanadium, ruthenium, molybdenum, niobium, and tantalum are selected. It is preferable that the metal salt is at least one metal salt, and it is particularly preferable that the metal salt is a metal complex salt. Particularly preferable metal salts (B) include, for example, iron nitrate, niobium chloride, tantalum chloride, ruthenium chloride, erbium chloride, ammonium tungstate, vanadyl sulfate, pentaethoxytantalum, and pentaethoxyniobium.

  The amount of the metal salt (B) added is in the range of 0.0005 to 0.03, particularly 0.001 to 0.02, in terms of metal atoms with respect to one titanium atom in the titanium-containing aqueous liquid (A). The inside is preferable.

Stabilizer (C)
The stabilizer (C) is used for allowing the titanium compound in the titanium-containing aqueous liquid (A) to stably exist in water. Further, by stabilizing the titanium-containing aqueous liquid (A) with this stabilizer (C), the titanium concentration can be made higher than that of the conventional method such as the sol-gel method, and therefore the productivity of titanium oxide can be increased. it can. Preferred examples of the stabilizer (C) include phosphoric acid compounds, organic acids, basic compounds, β-diketones and β-ketoesters.

  Examples of the phosphoric acid compound include phosphoric acid, strong phosphoric acid, triphosphoric acid, hypophosphoric acid, hypophosphoric acid, trimetaphosphoric acid, diphosphoric acid, diphosphoric acid, pyrophosphoric acid, pyrophosphoric acid , Monophosphoric acids such as metaphosphoric acid, metaphosphoric acid, phosphoric acid (orthophosphoric acid), and phosphoric acid derivatives, and salts thereof; condensed polyphosphoric acids such as tripolyphosphoric acid, tetraphosphoric acid, hexaphosphoric acid, and condensed phosphoric acid derivatives, and these And the like. These compounds can be used alone or in combination of two or more. Moreover, as an alkali compound which forms above-mentioned salt, organic or inorganic alkali compounds, such as lithium, sodium, potassium, ammonium, are mentioned, for example. Furthermore, it is preferable to use a phosphate compound that is soluble in water.

  As phosphoric acid compounds, phosphoric acid, sodium pyrophosphate, sodium tripolyphosphate, sodium tetraphosphate, metaphosphoric acid, ammonium metaphosphate, sodium hexametaphosphate, etc. are particularly effective in the storage stability of titanium dispersions. Therefore, it is preferable to use this.

  Examples of the organic acid include organic carboxylic acids such as acetic acid, oxalic acid, glycolic acid, lactic acid, malic acid, citric acid, tartaric acid, and gluconic acid, organic sulfonic acids, organic sulfinic acids, phenol, and thiophenol. , Organic nitro compounds, organic phosphoric acid, 1-hydroxyethane-1, 1-diphosphonic acid, aminotrimethylenephosphonic acid, N, N-bis (2-phosphoethyl) hydroxyamine, N, N-bis (2-phosphomethyl) ) Hydroxyamine, hydrolyzate of 2-hydroxyethylphosphonic acid dimethyl ether, and organic phosphoric acid such as 2-phosphonobutane-1,2,4-tricarboxylic acid. Moreover, as an organic acid salt, an alkali compound is blended with an organic acid. As an alkali compound which forms this salt, organic or inorganic alkali compounds, such as lithium, sodium, potassium, ammonium, are mentioned, for example. These compounds can be used alone or in combination of two or more. Furthermore, it is preferable to use an organic acid that is soluble in water.

  Examples of organic acids include hydroxycarboxylic acids such as glycolic acid, lactic acid, malic acid, citric acid, tartaric acid and gluconic acid; hydroxyl group-containing organic phosphoric acids such as 1-hydroxyethane-1 and 1-diphosphonic acid A carboxyl group-containing organic phosphoric acid such as 2-phosphonobutane-1,2,4-tricarboxylic acid exerts an excellent effect on the storage stability of the titanium dispersion, so that it is preferable to use this.

  Examples of the basic compound include ammonia, an organic basic compound, an alkali metal hydroxide, and an alkaline earth metal hydroxide. As basic compounds, ammonia, dimethylethanolamine, 2-amino-2-methyl-1-propanol, triethylamine, morpholine, lithium hydroxide, sodium hydroxide, potassium hydroxide and the like are particularly storage stability of titanium dispersions. It is preferable to use this because it exhibits an excellent effect.

  Examples of the β-diketone and β-ketoester include acetylacetone, methyl acetoacetate, ethyl acetoacetate, acetoacetate-n-propyl, acetoacetate-i-propyl, acetoacetate-n-butyl, acetoacetate-sec-butyl. Acetoacetate-t-butyl, 2,4-hexane-dione, 2,4-heptane-dione, 3,5-heptane-dione, 2,4-octane-dione, 2,4-nonane-dione, 5- Examples include methyl-hexane-dione, and these can be used alone or in combination of two or more. Of these, acetylacetone and ethyl acetoacetate are preferably used from the viewpoint of storage stability of the titanium dispersion.

  The blending ratio of the stabilizer (C) is 1 to 400 parts by weight, particularly 10 to 200 parts by weight with respect to 100 parts by weight of the solid content of the titanium-containing aqueous liquid (A). From the viewpoint of the storage stability of the aqueous dispersion containing the liquid (A), a metal salt other than titanium (B), and a stabilizer (C).

Production of Metal Doped Titanium Oxide Fine Particles Metal doped titanium oxide fine particles are composed of a titanium-containing aqueous liquid (A), a salt of a metal other than titanium (B) and a stabilizer (C), and a temperature of 70 to 300 ° C. It can be obtained by performing a heat treatment for about 5 hours, and separating and drying the fine particles from the obtained aqueous dispersion of metal-doped titanium oxide fine particles. As the heat treatment, hydrothermal treatment is preferably used. For example, a titanium-containing aqueous liquid (A), a salt of a metal other than titanium (B), and a stabilizer (C) are blended in an autoclave, and the pressure is set to 0. An aqueous dispersion of metal-doped titanium oxide fine particles can be obtained by hydrothermal treatment at 1 to 20 MPa, particularly at a pressure of 2 to 5 MPa, and at a temperature of 70 to 300 ° C., particularly 100 to 200 ° C. for about 1 to 5 hours. . In many cases, the obtained aqueous dispersion of metal-doped titanium oxide fine particles becomes a translucent suspension or a dispersion that causes precipitation. The aqueous dispersion of the metal-doped titanium oxide fine particles thus obtained is separated from the fine particles by standing or centrifuging, washed with alcohol and / or water as necessary, and then dried at a temperature of 80 to 100 ° C. for several hours. Thus, metal-doped titanium oxide fine particles can be obtained.

  The metal-doped titanium oxide fine particles obtained as described above have photocatalytic activity even in the visible light region, and can be used as they are, but are usually mixed with a binder component and have a molded product having photocatalytic activity. Alternatively, it can be used by mixing with a binder component, diluting with a diluent as necessary to form a coating agent, and applying to a substrate to form a film having photocatalytic activity.

  The binder component may be either an inorganic binder or an organic binder, but is preferably one that is not easily deteriorated by light, and preferred examples include silica, alumina, a fluororesin, and a silicone resin.

  Molded articles and coatings using the metal-doped titanium oxide fine particles of the present invention have photocatalytic activity, and are suitable for the purpose of decomposing organic substances, eliminating bacteria and bacteria, and preventing dirt sticking and odor generation. In addition, it can be suitably used for applications that require antifouling properties and antifogging properties due to the hydrophilizing action of the surface of the molded product or coating due to photocatalytic activity.

  Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples. Hereinafter, “parts” and “%” mean “parts by weight” and “% by weight”, respectively. The present invention is not limited to the following examples.

Production and production example 1 of titanium-containing aqueous liquid
10 parts of tetraiso-propoxytitanium was added dropwise to a mixture of 10 parts of 30% hydrogen peroxide and 100 parts of deionized water with stirring at 20 ° C. over 1 hour. Thereafter, it was aged at 25 ° C. for 2 hours to obtain a yellow transparent slightly viscous titanium-containing aqueous liquid. The concentration of titanium contained in the titanium-containing aqueous liquid is 2.3% in terms of TiO _2.
Production Example 1 of Metal Doped Titanium Oxide Fine Particles
Iron nitrate and citric acid were added to the titanium-containing aqueous liquid obtained in Production Example 1 so that 0.01 mol of iron nitrate and 0.6 mol of citric acid were added to 1 mol of titanium atoms in the titanium-containing aqueous liquid. Stir for 2 hours to obtain a clear solution. 50 ml of this solution was introduced into an autoclave for 100 ml, and hydrothermal treatment was performed for 1 hour under conditions of a pressure of 3 MPa and a temperature of 200 ° C. The fine particle dispersion obtained by hydrothermal treatment was filtered, washed thoroughly with deionized water, and then vacuum-dried at 80 ° C. for 5 hours to obtain iron-doped titanium oxide powder (T1).

Example 2
In Example 1, it manufactured like Example 1 except using ethylenediaminetetraacetic acid diammonium instead of a citric acid, and obtained iron dope titanium oxide powder (T2).

Example 3
Niobium pentachloride and citric acid are added to the titanium-containing aqueous liquid obtained in Production Example 1 such that 0.01 mol of niobium pentachloride and 0.6 mol of citric acid are added to 1 mol of titanium atom in the titanium-containing aqueous liquid. And stirred for 2 hours to obtain a clear solution. 50 ml of this solution was introduced into an autoclave for 100 ml, and hydrothermal treatment was performed for 1 hour under conditions of a pressure of 3 MPa and a temperature of 200 ° C. The fine particle dispersion obtained by hydrothermal treatment was filtered, washed thoroughly with deionized water, and then vacuum-dried at 80 ° C. for 5 hours to obtain niobium-doped titanium oxide powder (T3).

Example 4
In Example 3, it manufactured like Example 3 except using ethylenediaminetetraacetic acid diammonium instead of a citric acid, and obtained the niobium dope titanium oxide powder (T4).

Example 5
To the titanium-containing aqueous liquid obtained in Production Example 1, vanadyl sulfate and citric acid were added so that the amount of vanadyl sulfate was 0.01 mol and citric acid was 0.6 mol with respect to 1 mol of titanium atom in the titanium-containing aqueous liquid. Stir for 2 hours to obtain a clear solution. 50 ml of this solution was introduced into an autoclave for 100 ml, and hydrothermal treatment was performed for 1 hour under conditions of a pressure of 3 MPa and a temperature of 200 ° C. The fine particle dispersion obtained by hydrothermal treatment was filtered, washed thoroughly with deionized water, and then vacuum dried at 80 ° C. for 5 hours to obtain vanadium-doped titanium oxide powder (T5).

Example 6
In Example 5, it manufactured like Example 5 except using ethylenediaminetetraacetic acid diammonium instead of citric acid, and vanadium dope titanium oxide powder (T6) was obtained.

Example 7
Niobium pentachloride and malic acid are added to the titanium-containing aqueous liquid obtained in Production Example 1 so as to be 0.01 mol niobium pentachloride and 0.6 mol malic acid with respect to 1 mol of titanium atom in the titanium-containing aqueous liquid. And stirred for 2 hours to obtain a clear solution. 50 ml of this solution was introduced into an autoclave for 100 ml, and hydrothermal treatment was performed for 1 hour under conditions of a pressure of 3 MPa and a temperature of 200 ° C. The fine particle dispersion obtained by hydrothermal treatment was filtered, washed thoroughly with deionized water, and then vacuum-dried at 80 ° C. for 5 hours to obtain niobium-doped titanium oxide powder (T7).

Example 8
In Example 7, it manufactured like Example 7 except using acetylacetone instead of malic acid, and obtained niobium dope titanium oxide powder (T8).

Comparative Example 1 for Production of Titanium Oxide Fine Particles without Metal Doping
50 ml of the titanium-containing aqueous liquid obtained in Production Example 1 was introduced into a 100 ml autoclave and hydrothermally treated for 1 hour under the conditions of a pressure of 3 MPa and a temperature of 200 ° C. The fine particle dispersion obtained by hydrothermal treatment was filtered, washed thoroughly with deionized water, and then vacuum dried at 80 ° C. for 5 hours to obtain titanium oxide powder (T9).

Evaluation of photocatalytic activity The photocatalytic activity of the metal-doped titanium oxide powder obtained in the above example and the titanium oxide powder obtained in the comparative example was evaluated according to the following test method. The obtained results are shown in Table 1 below.

  Photocatalytic activity: 100 parts of an acetic acid aqueous solution having a concentration of 20 ppm was mixed in a reaction vessel made of quartz glass, and 0.05 parts of metal-doped titanium oxide powder or titanium oxide powder was added to the solution. Using a 100W high-pressure mercury lamp as the light source, light with a wavelength of 450 nm or less is cut by an ultraviolet cut filter, and this solution is irradiated. The concentration of acetic acid in the solution 2 hours after the start of light irradiation is determined by liquid chromatography. did. It can be said that the lower the acetic acid concentration after light irradiation, the higher the photocatalytic activity.

Claims (9)

Hydrogen peroxide containing at least one titanium compound selected from the group consisting of titanium metal, hydrolyzable titanium compounds, low-condensates of hydrolyzable titanium compounds, titanium hydroxide, metatitanic acid, and low-condensates of titanium hydroxide Separating and drying a titanium-containing aqueous liquid (A) obtained by mixing with water from a solution obtained by heat treatment in the presence of a metal salt (B) other than titanium and a stabilizer (C). A method for producing metal-doped titanium oxide fine particles, wherein metal-doped titanium oxide fine particles are obtained by: _{2. The} method for producing metal-doped titanium oxide fine particles according to claim 1, wherein the concentration of titanium contained in the titanium-containing aqueous liquid (A) is 0.1 to 10% by weight in terms of TiO ₂ . The metal-doped oxidation according to claim 1 or 2, wherein the metal salt (B) other than titanium is a salt of at least one metal selected from the group consisting of iron, copper, vanadium, ruthenium, molybdenum, niobium and tantalum. A method for producing titanium fine particles. The stabilizer (C) is at least one compound selected from the group consisting of phosphoric acid compounds, organic acids, basic compounds, β-diketones and β-ketoesters. The manufacturing method of metal dope titanium oxide microparticles | fine-particles as described in any one of. The method for producing metal-doped titanium oxide fine particles according to any one of claims 1 to 4, wherein the heat treatment includes a step of hydrothermal treatment under conditions of a pressure of 0.1 to 20 MPa and a heating temperature of 70 to 300 ° C. Metal-doped titanium oxide fine particles obtained using the production method according to any one of claims 1 to 5. A photocatalyst having photocatalytic activity even in the visible light region, obtained by using the metal-doped titanium oxide fine particles according to claim 6. The molded object containing the metal dope titanium oxide microparticles | fine-particles obtained using the manufacturing method as described in any one of Claims 1-5. The coating agent containing the metal dope titanium oxide microparticles | fine-particles obtained using the manufacturing method as described in any one of Claims 1-5.