JP4351936B2 - Method for producing titanium oxide photocatalyst - Google Patents

Description

  The present invention relates to a titanium oxide photocatalyst and a method for producing the same, and more particularly to a titanium oxide photocatalyst that is visible light responsive and has high photocatalytic activity and is effective for harmful substance decomposition and wet solar cells.

  Titanium oxide powder has long been used as a white pigment, and in recent years it has been widely used in sintered materials used in electronic materials such as UV shielding materials for cosmetics, photocatalysts, capacitors, thermistors, and barium titanate materials. Has been. In particular, there have been many attempts to use it as a photocatalyst in recent years. Titanium oxide is excited by irradiating titanium oxide with light having energy higher than its band gap, and electrons are generated in the conduction band. Holes are generated in the electric band, and development of applications for photocatalytic reactions using the reducing power of electrons or the oxidizing power of holes has been actively conducted. This titanium oxide photocatalyst has a wide variety of uses, including generation of hydrogen by water decomposition, synthesis of organic compounds using redox reactions, exhaust gas treatment, air purification, deodorization, sterilization, antibacterial, water treatment, lighting Numerous applications have been developed, such as preventing contamination of equipment.

  However, since titanium oxide exhibits a large refractive index in the wavelength region near visible light, light absorption hardly occurs in the visible light region. This is because anatase-type titanium dioxide has a band gap of 3.2 eV and rutile-type titanium dioxide has a band gap of 3.0 eV, and the wavelength of light that can be absorbed by titanium oxide is 385 nm or less for anatase-type titanium oxide. The rutile type titanium oxide has a thickness of 415 nm or less. Most of the light of these wavelengths falls in the ultraviolet region, and only a small portion is contained in infinite sunlight on the earth. Conventionally known titanium oxide photocatalysts are photocatalysts under ultraviolet irradiation. Although it exhibits the characteristics, only a part of its energy can be used under sunlight, and sufficient activity as a photocatalyst cannot be expected. Also, considering the use under fluorescent lamps indoors, since the spectrum of fluorescent lamps is almost 400 nm or more, sufficient characteristics as a photocatalyst cannot be expressed. In view of this, photocatalysts having higher utility and higher activity have been developed by exhibiting catalytic activity in the visible light region.

For example, in Patent Document 1 (Japanese Patent Laid-Open No. 9-262482), one or more kinds of metal ions selected from the group consisting of Cr, V, Cu, Fe, Mg, Ag, Pd, Ni, Mn, and Pt are included. A photocatalyst containing titanium oxide from the surface at a rate of 1 × 10 ¹⁵ ions / g-TiO ₂ or more is disclosed, and ions of these metals are accelerated to a high energy of 30 KeV or more to form titanium oxide. Irradiation introduces the metal ions into titanium oxide. Moreover, in patent document 2 (Unexamined-Japanese-Patent No. 11-290697), the process which hold | maintains the solid containing a transition metal and the titanium oxide by which the said transition metal is doped in a vacuum chamber, and a metal inside the said vacuum chamber A photocatalytic titanium oxide doped with the transition metal by generating plasma and irradiating the generated metal plasma is disclosed. However, these inventions must use a very special apparatus such as accelerating metal ions to high energy and generating metal plasma in order to dope metal ions into titanium oxide. Not suitable for manufacturing.

  In order to solve such a problem, Patent Document 3 (Japanese Patent Laid-Open No. 12-237598) discloses that B, P, Ti, which are components different from the constituent components of the semiconductor, on the surface of the semiconductor such as titanium oxide. , V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Zr, Nb, Mo, Pd, Ag, Cd, Sn, Sb, Hf, Ta, W, Pt, Hg, Pb, Bi, Pr , Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and a medium containing at least one cation selected from the group consisting of Lu, and contacting the semiconductor A method for producing a visible light responsive photocatalyst comprising a first step of containing a cation and a second step of heating the semiconductor containing the cation in a reducing atmosphere is disclosed. . However, the photocatalyst doped with metal ions in titanium oxide by such a method does not necessarily have sufficient catalytic activity, and further improvement has been desired.

In addition to the photocatalyst in which titanium ions are doped with metal ions such as transition metals as described above to exhibit catalytic activity in the visible light region, in Patent Document 4 (WO 01/010552), oxygen sites of titanium oxide crystals are disclosed. Titanium oxide by either substituting part of it with nitrogen atoms, doping nitrogen atoms between the lattices of titanium oxide crystals, or doping nitrogen atoms into the crystal grain boundaries of titanium oxide, or a combination thereof A photocatalytic substance containing a nitrogen atom in a crystal and a photocatalytic substance exhibiting a photocatalytic action in the visible light region having a Ti—O—N structure in which a titanium oxide crystal contains nitrogen is disclosed. As a method for obtaining such a photocatalytic substance, sputtering of titanium oxide in a nitrogen gas atmosphere is mentioned. However, the production cost is high and it is difficult to produce on an industrial scale. Moreover, although there is also a disclosure of a simple method of firing titanium oxide in an ammonia atmosphere, the nitrogen oxide is not sufficiently doped in titanium oxide, and the resulting photocatalyst has insufficient catalytic activity.
JP-A-9-262482 JP-A-11-290697 JP-A-12-237598 WO 01/010552 Publication

  Accordingly, an object of the present invention is to provide a titanium oxide photocatalyst exhibiting photocatalytic activity in the visible light region and having high activity and low cost.

  Under such circumstances, the present inventors have conducted intensive studies. As a result, titanium oxide is a mixed crystal of rutile type and anatase type, and titanium oxide containing a sulfur atom has high light absorption characteristics in the visible light region. The present invention was completed.

That is, the present invention provides a rutile ratio by calcining a mixture of titanium oxide powder and thiourea obtained by hydrolysis or alkali neutralization of an aqueous titanium chloride solution at 300 to 600 ° C. in an oxidizing atmosphere. The present invention provides a method for producing a titanium oxide photocatalyst characterized by obtaining a titanium oxide photocatalyst which is a rutile-type and anatase-type mixed crystal containing 5 to 99% and containing a sulfur atom as a cation. .

  According to the titanium oxide photocatalyst of the present invention, the photocatalytic activity not only in the ultraviolet region but also in the visible light region is high, so that the photocatalytic action can be sufficiently exerted even in a room such as a fluorescent lamp that is not exposed to sunlight. The application of the photocatalyst that has remained in the ultraviolet region can be expanded.

In the titanium oxide photocatalyst of the present invention, the titanium oxide is a mixed crystal of rutile type and anatase type and contains a sulfur atom, but the rutile ratio of titanium oxide is 5 to 99%, preferably 20 to 80%, More preferably, it is 30 to 70%. The titanium oxide photocatalyst of the present invention is a mixed crystal of rutile type and anatase type, but may also contain amorphous titanium oxide. The rutile-type and anatase-type titanium oxides contain sulfur atoms, and these sulfur atoms are substituted for titanium atoms in titanium oxide and are doped into titanium oxide as cations. Specifically, it can be represented by the chemical formula Ti _1-x S _x O ₂ , and x, which is the content of sulfur atoms with respect to titanium atoms, is 0.001 or more, preferably 0.002 or more, more preferably 0.002. ~ 0.008. Moreover, an average particle diameter is 5-50 nm by the particle diameter of the primary particle by SEM photograph image observation, and a BET specific surface area is 50-250 m < ² > / g. The titanium oxide photocatalyst of the present invention is generally a pale yellow or yellow powder although it varies depending on the content of the sulfur atom.

  Hereafter, the preparation method of the titanium oxide photocatalyst of this invention is described.

  Titanium oxide which is a mixed crystal of rutile type and anatase type of the present invention can be obtained by a known method, for example, a method of hydrolyzing alkoxy titanium, a method of hydrolyzing or neutralizing an aqueous titanium chloride solution, or sulfuric acid A liquid phase method such as a method using titanyl as a raw material, or a gas phase method in which titanium tetrachloride vapor is hydrolyzed or reacted with oxygen can be employed. Among these, the method using a titanium chloride aqueous solution as a raw material can obtain the titanium oxide photocatalyst of the present invention efficiently and at low cost. In the liquid phase method using alkoxy titanium as a raw material, titanium oxide having a small particle size and a large specific surface area can be obtained. As a result, a titanium oxide photocatalyst having high photocatalytic activity can be obtained. However, it is difficult to control the rutile ratio of the resulting titanium oxide, and alkoxy titanium is very expensive. When produced on an industrial scale, the production cost is high and it is difficult to widely disseminate the photocatalyst. On the other hand, the vapor phase method can produce inexpensive titanium oxide, but has a drawback that the particle size of the obtained titanium oxide is larger than that of the liquid phase method, and the activity when the photocatalyst is formed becomes low.

  As a preferred method for forming the titanium oxide photocatalyst of the present invention, first, a mixture of titanium oxide powder and sulfur or a sulfur-containing compound obtained by hydrolyzing or neutralizing an aqueous solution of titanium chloride with an alkali is obtained. Bake. The titanium chloride aqueous solution is preferably a titanium trichloride aqueous solution or a titanium tetrachloride aqueous solution. The aqueous titanium trichloride solution can be obtained, for example, by dissolving titanium metal in hydrochloric acid. As the metal titanium, titanium powder, sponge-like titanium, or titanium scrap such as chips are used. The titanium tetrachloride aqueous solution can be obtained by dissolving titanium tetrachloride in water or hydrochloric acid. The titanium concentration in the aqueous titanium chloride solution is arbitrary, but the titanium content is 1 to 20% by weight, preferably 5 to 15% by weight in consideration of the production efficiency or the particle size of the resulting titanium oxide powder. In addition, it is desirable that the aqueous solution of titanium chloride has few impurity components and high purity. Specifically, aluminum, iron, and vanadium are each 1 ppm or less, and silicon and tin are each 10 ppm or less.

The titanium chloride aqueous solution is hydrolyzed or neutralized with an alkali to obtain a titanium oxide powder. Specific examples include the following methods.
(1) A titanium chloride aqueous solution is heated under reflux and hydrolyzed to precipitate a titanium oxide powder. Chlorine gas is generated at this time, but finer titanium oxide powder can be obtained by suppressing the generation of hydrochloric acid gas by pressurizing or refluxing and hydrolyzing in a low pH region.
(2) An aqueous titanium chloride solution is contacted with an alkali metal hydroxide such as ammonia, aqueous ammonia or NaOH, KOH to precipitate titanium oxide powder. At this time, it is desirable to neutralize with ammonia or aqueous ammonia containing no metal component among these alkalis.

  After obtaining by hydrolyzing or neutralizing the aqueous titanium chloride solution as described above, orthotitanic acid or metatitanic acid is produced, but in order to improve the photocatalytic activity, titanium chloride is produced under conditions such that metatitanic acid is produced. It is desirable to hydrolyze or neutralize the aqueous solution. Thereafter, cleaning is performed to remove impurities such as hydrochloric acid and alkali components, followed by drying to obtain titanium oxide powder. Further, heat treatment is performed as necessary to remove water such as crystal water.

  In the method of (2) above, the aqueous titanium chloride solution is neutralized with a hydroxide of an alkali metal such as NaOH, KOH, CaOH (slaked lime) or a metal such as an alkaline earth metal, and these metals are added to the resulting titanium oxide powder. The components may remain, and the properties of the finally obtained photocatalyst are not significantly affected. For example, an aqueous titanium chloride solution is neutralized by adding a slaked lime solution to precipitate titanium oxide hydrate, and a flocculant such as polyaluminum chloride is added to this suspension to precipitate and separate solids. Such a method is a process generally used for wastewater treatment such as acidic water, and it is possible to produce titanium oxide powder very efficiently on an industrial scale.

The titanium oxide powder obtained as described above can control the average particle size, specific surface area, and crystal form depending on the conditions of hydrolysis or neutralization with alkali. In order to improve the activity of the photocatalyst, A larger specific surface area is preferred. Specifically ^{50 m} 2 / g or more in BET specific surface area is preferably 100 m ² / g or more, particularly preferably 150 to 250 ² / g.

  Further, the titanium oxide powder obtained at this point is controlled to a desired rutile ratio, and finally a titanium oxide photocatalyst containing mixed crystals of rutile type and anatase type is formed. The rutile ratio of the obtained titanium oxide powder can be controlled by the time or speed of hydrolysis or neutralization with the alkali of the above titanium chloride aqueous solution. For example, when neutralizing a titanium tetrachloride aqueous solution with ammonia water, etc., neutralization in a short time yields titanium oxide with a low anatase-rich rutile ratio, and slowing the neutralization reaction results in an oxidation with a high rutile ratio. Titanium can be obtained. The neutralization rate is preferably 50 to 500 g, more preferably 100 to 300 g, per minute in terms of titanium atoms. When it is slower than the rate of neutralizing 200 g of titanium atoms per minute, the rutile ratio becomes 50% or more. In addition, the rutile ratio of titanium oxide obtained can be controlled by the pH of the reaction system when neutralizing or hydrolyzing the titanium chloride aqueous solution. For example, after titanium oxide powder is precipitated, the ripening reaction is carried out in a low pH atmosphere. The rate is improved, and a rutile type and anatase type mixed crystal can be obtained.

  The sulfur-containing compound used in the above method is preferably a liquid or solid compound at room temperature, and examples thereof include sulfur-containing inorganic compounds, sulfur-containing organic compounds, and metal sulfides. Specific examples include thioethers, thioureas, thioamides, thioalcohols, thioaldehydes, thiazyl, mercaptals, thiols, and thiocyanates. Specific compounds include thiourea and sulfoacetic acid. , Thiophenol, thiophene, benzothiophene, dibenzothiophene, thiobenzophenone, bithiophene, phenothiazine, sulfolane, thiazine, thiazole, thiadiazole, thiazoline, thiazolidine, thianthrene, thiane, thioacetanilide, thioacetamide, thiobenzamide, thioanisole, thionine, methyl Thiol, thioether, thiocyan, sulfuric acid, sulfonic acids, sulfonium salts, sulfonamides, sulfinic acids, sulfoxides, sulfines, sulfanes, etc. It is. These compounds can be used alone or in combination of two or more.

  Among these, sulfur-containing organic compounds are preferable, and organic compounds containing no oxygen atom and containing sulfur and nitrogen atoms are particularly preferable, and specifically, thiourea is preferable.

In the present invention, a mixture of the above titanium oxide powder and sulfur or a sulfur-containing compound is formed. The method of forming this mixture is:
(1) A method of obtaining a mixture of titanium oxide powder and sulfur or a sulfur-containing compound by mixing sulfur or a sulfur-containing compound with an aqueous titanium chloride solution and then neutralizing with hydrolysis or alkali.
(2) A method in which an aqueous titanium chloride solution is hydrolyzed or neutralized with an alkali to obtain a titanium oxide powder, and then the titanium oxide powder and sulfur or a sulfur-containing compound are mixed to obtain a mixture;
(3) Titanium chloride aqueous solution is hydrolyzed or neutralized with alkali to obtain titanium oxide powder, the obtained titanium oxide powder is calcined, and then the titanium oxide powder and sulfur or a sulfur-containing compound are mixed to obtain a mixture. How to get,
(4) Sulfur or a sulfur-containing compound is mixed with an aqueous titanium chloride solution, then hydrolyzed or neutralized with alkali to form a solid, and further mixed with sulfur or a sulfur-containing compound to obtain titanium oxide powder and sulfur or a sulfur-containing compound. A method for obtaining a mixture of sulfur compounds,
Etc.

  The amount of sulfur or sulfur-containing compound to be mixed with the titanium oxide powder used in the present invention is usually 1% by weight or more, preferably 5% by weight or more, more preferably, based on titanium oxide when converted to the weight of sulfur atoms. 10 to 30% by weight. If the amount of sulfur or sulfur-containing compound mixed is small, the amount of sulfur atoms contained in the photocatalytic titanium oxide will eventually decrease, and sufficient visible light absorption will not occur.

  Next, the titanium oxide powder obtained above and a mixture of sulfur or a sulfur-containing compound are calcined to form a titanium oxide photocatalyst. The calcining temperature is 200 to 800 ° C, preferably 300 to 600 ° C, more preferably 400 to 500. ° C. When a sulfur-containing organic compound is used, the reaction is performed at a temperature at which the compound is decomposed and sulfur atoms are liberated and replaced with titanium atoms in titanium oxide. The firing atmosphere is performed in an oxidizing atmosphere such as air or oxygen, a reducing atmosphere such as hydrogen gas or ammonia gas, an inert atmosphere such as nitrogen gas or argon gas, or under vacuum. Of these, the photocatalytic activity in the visible light region is preferably improved by carrying out in a reducing atmosphere such as hydrogen gas. Although only a reducing gas such as hydrogen gas may be used, firing in an atmosphere of a mixed gas of hydrogen and oxygen or a mixed gas of hydrogen, oxygen and inert gas is also effective. Furthermore, it is important to maintain the firing atmosphere so that the partial pressure of the sulfur component is maintained to some extent so that sulfur does not evaporate during the firing or the sulfur-containing compound decomposes and the sulfur component is not discharged from the firing furnace. When a by-product gas such as carbon dioxide gas is generated by decomposition during firing, such as a sulfur-containing organic compound having a carbon atom, it is better to exhaust from the firing atmosphere to some extent. Therefore, the container for firing is not completely open or sealed, and the upper part is opened so that a certain amount of pressure is applied and the by-product gas can be discharged, and a non-fixed lid is placed on the upper part. A cylindrical, dished or rectangular container provided is preferred.

  The titanium oxide photocatalyst obtained as described above is washed as necessary to remove free sulfur components and others. Moreover, in order to improve the dispersibility of particle | grains, it can also surface-treat with surfactant etc.

  Moreover, the titanium oxide photocatalyst is excellent in visible light absorption characteristics, and an ultraviolet-visible diffuse reflection spectrum is measured, and the integrated value of the absorbance at a wavelength of 300 to 350 nm is set to 1, usually, the absorbance at a wavelength of 350 to 400 nm. The integrated value of the absorbance at a wavelength of 400 to 500 nm is 0.3 to 0.9, and the integrated value of the absorbance at a wavelength of 350 to 400 nm is preferably 0.4. The integrated value of absorbance at a wavelength of 400 to 500 nm is 0.4 to 0.8, and more preferably, the integrated value of absorbance at a wavelength of 350 to 400 nm is 0.5 to 0.7. And the integrated value of the absorbance at a wavelength of 400 to 500 nm is 0.5 to 0.75.

  The titanium oxide photocatalyst of the present invention can be used as a powder as described above, but as a general photocatalyst application, a titanium oxide photocatalyst layer is applied by applying a titanium oxide photocatalyst to a substrate for exhaust gas treatment, deodorization, antifouling, etc. Therefore, it is desirable to use water or an organic solvent dispersion, coating liquid or paint. In recent years, water-based environmental coating agents or paints are also required for photocatalyst materials due to the problem of sick house such as acetaldehyde, and the titanium oxide photocatalyst of the present invention is desirably used as an aqueous dispersion or paint.

  The titanium oxide photocatalyst of the present invention obtained as described above has excellent absorption characteristics in the visible light region, and even if there is no ultraviolet light source such as black light, a light source using sunlight or a fluorescent lamp in a room is sufficient. Photocatalytic activity is exhibited. In addition, compared to conventional visible light responsive photocatalysts such as titanium oxide doped with nitrogen atoms, it is industrially very advantageous because it can be produced efficiently and at low cost, exhaust gas treatment, air purification, deodorization, It can be widely applied to photocatalyst paints and photocatalyst coating materials for the purpose of sterilization, antibacterial, water treatment, prevention of soiling of lighting equipment, etc., and photocatalytic devices utilizing the action of decomposing harmful substances due to oxidation.

  EXAMPLES Next, although an Example is given and this invention is demonstrated more concretely, this is only an illustration and does not restrict | limit this invention.

In the examples and comparative examples, the titanium oxide photocatalyst was evaluated as follows.
(1) Measurement of sulfur content in titanium oxide photocatalyst Field Emission-SEM (FE-SEM) with an energy dispersive X-ray fluorescence spectrometer (EDX) (Hitachi Electron Scanning Microscope S) -4700), a quantitative analysis of sulfur atoms in titanium oxide was performed.
(2) Measurement of visible light absorption characteristics The diffuse reflection absorption spectrum of the titanium oxide photocatalyst was measured with an ultraviolet-visible spectrophotometer with an integrating sphere (V-550-DS manufactured by JASCO Corporation).
(3) Measurement of the rutile ratio The peak area (Ir) of the strongest interference line (surface index 110) of rutile crystalline titanium oxide in the X-ray diffraction pattern according to ASTM D 3720-84, and the strongest interference line of titanium oxide powder ( The peak area (Ia) of the plane index 101) was obtained and obtained from the above formula. The X-ray diffraction measurement conditions are as follows.

(X-ray diffraction measurement conditions)
Diffraction device RAD-1C (manufactured by Rigaku Corporation)
X-ray tube Cu
Tube voltage / tube current 40kV, 30mA
Slit DS-SS: 1 degree, RS: 0.15mm
Monochromator graphite measurement interval 0.002 degrees
Counting method Constant clock method

297 g of a titanium tetrachloride aqueous solution having a titanium concentration of 4% by weight was inserted into a 1000-milliliter round bottom flask equipped with a stirrer, and then heated to 60 ° C. Next, ammonia water was added so that the pH of the reaction system was maintained at 7.4, and neutralization was performed at 60 ° C. for 1 hour. The obtained solid was filtered and washed with pure water, and 9.7 g of thiourea dissolved in 100 ml of pure water was added thereto and stirred for 30 minutes. Thereafter, the solid was dried at 60 ° C. and pulverized with a ball mill to obtain a mixture of titanium oxide powder and thiourea. This mixture was placed in a firing furnace and fired at 400 ° C. for 3 hours. Thereafter, it was pulverized by a ball mill, washed with pure water, and then dried at 60 ° C. to obtain a pale yellow titanium oxide photocatalyst. When the sulfur content in the obtained titanium oxide photocatalyst was measured, it was 0.13% by weight, the specific surface area was 109 m ² / g, and the rutile ratio was 10%. The visible light absorption characteristics are shown in FIG.

297 ml of titanium tetrachloride aqueous solution having a titanium concentration of 4% by weight was inserted into a 1000 ml round bottom flask equipped with a stirrer, and then 9.7 g of thiourea dissolved in 100 ml of pure water was added and heated to 60 ° C. did. Next, ammonia water was added so that the pH of the reaction system was maintained at 7.4, and neutralization was performed at 60 ° C. for 1 hour. The obtained solid was filtered, washed with pure water, and stirred for 30 minutes. Thereafter, the solid was dried at 60 ° C. and pulverized with a ball mill to obtain a mixture of titanium oxide powder and thiourea. This mixture was placed in a firing furnace and fired at 400 ° C. for 3 hours. Thereafter, it was pulverized by a ball mill, washed with pure water, and then dried at 60 ° C. to obtain a pale yellow titanium oxide photocatalyst. When the sulfur content in the obtained titanium oxide photocatalyst was measured, it was 0.05% by weight, the specific surface area was 120 m ² / g, and the rutile ratio was 60%. The visible light absorption characteristics are shown in FIG.

Comparative Example 1
297 ml of a titanium tetrachloride aqueous solution having a titanium concentration of 4% by weight was inserted into a 1000-ml round bottom flask equipped with a stirrer and heated to 60 ° C. Next, ammonia water was added so that the pH of the reaction system was maintained at 7.4, and neutralization was performed at 60 ° C. for 1 hour. The obtained solid was filtered, washed with pure water, and stirred for 30 minutes. Thereafter, the solid was dried at 60 ° C. and pulverized with a ball mill to obtain a titanium oxide powder. This titanium oxide powder was charged into a firing furnace, ammonia gas was introduced into the firing furnace, and firing was performed at 400 ° C. for 3 hours in an ammonia atmosphere. Thereafter, it was pulverized by a ball mill, washed with pure water, and then dried at 60 ° C. to obtain a pale yellow titanium oxide photocatalyst. The specific surface area of the obtained titanium oxide was 579 m ² / g rutile, and the rate was 15%. The visible light absorption characteristics are shown in FIG.

Comparative Example 2
Was charged ethanol 500ml round bottom flask equipped with a stirrer capacity 1000 milliliters, it was heated to 40 ° C., and here was added and dissolved thiourea 24.2 g. Next, 26.2 ml of tetraisopropoxytitanium was added and heated to 80 ° C. with stirring to hydrolyze tetraisopropoxytitanium and precipitate a solid. The obtained solid was dried at 60 ° C. and pulverized with a ball mill to obtain a mixture of titanium oxide powder and thiourea. This mixture was placed in a firing furnace and fired at 400 ° C. for 3 hours. Thereafter, it was pulverized by a ball mill, washed with pure water, and then dried at 60 ° C. to obtain a pale yellow titanium oxide photocatalyst. The obtained titanium oxide had a specific surface area of 190 m ² / g and a rutile ratio of 0%. The visible light absorption characteristics are shown in FIG.

It is a figure which shows the measurement result of the diffuse reflection absorption spectrum by the ultraviolet visible spectrophotometer of a titanium oxide photocatalyst.

Claims (8)

A mixture of titanium oxide powder and thiourea obtained by hydrolyzing or neutralizing an aqueous titanium chloride solution with an alkali is fired at 300 to 600 ° C. in an oxidizing atmosphere, so that the rutile ratio is 5 to 99%. A method for producing a titanium oxide photocatalyst comprising obtaining a titanium oxide photocatalyst which is a mixed crystal of a rutile type and an anatase type and contains a sulfur atom as a cation .   A thiourea is mixed with an aqueous titanium chloride solution, and then hydrolyzed or neutralized with an alkali to obtain a mixture of titanium oxide powder and thiourea, and then the mixture is fired at 300 to 600 ° C. Item 2. A method for producing a titanium oxide photocatalyst according to Item 1.   An aqueous titanium chloride solution is hydrolyzed or neutralized with an alkali to obtain a titanium oxide powder, and then the titanium oxide powder and thiourea are mixed to obtain a mixture, followed by firing at 300 to 600 ° C. Item 2. A method for producing a titanium oxide photocatalyst according to Item 1.   The method for producing a titanium oxide photocatalyst according to any one of claims 1 to 3, wherein the titanium chloride aqueous solution is a titanium trichloride aqueous solution or a titanium tetrachloride aqueous solution.   The method for producing a titanium oxide photocatalyst according to any one of claims 1 to 4, wherein the alkali is an alkali metal hydroxide or ammonia.   The method for producing a titanium oxide photocatalyst according to any one of claims 1 to 5, wherein the rutile ratio of the titanium oxide powder is 5 to 99%.   The method for producing a titanium oxide photocatalyst according to any one of claims 1 to 5, wherein a rutile ratio of the titanium oxide powder is 30 to 70%.   When the obtained titanium oxide photocatalyst measures an ultraviolet-visible diffuse reflection spectrum, the integrated value of the absorbance at a wavelength of 300 to 350 nm is 1, and the integrated value of the absorbance at a wavelength of 350 to 400 nm is 0.3 to 0.9. And the integrated value of the light absorbency of wavelength 400-500nm is 0.3-0.9, The manufacturing method of the titanium oxide photocatalyst in any one of Claims 1-7 characterized by the above-mentioned.

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