JP2008114178A - Method for producing black titanium dioxide anatase composite powder for visible light-responsive photocatalyst and method for producing solution composition for producing the powder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing black titanium dioxide anatase composite powder for a visible light-responsive photocatalyst, which powder is developed on the ground that the scope of application of a photocatalyst product is expanded into ultraviolet light-poor places where solar energy is utilized effectively, exhibits a photocatalytic function to visible light and ultraviolet light and has a black hue unpublished up to now and to provide a method for producing a solution composition for producing the black titanium dioxide anatase composite powder. <P>SOLUTION: The solution composition suitable for producing the visible light-responsive black titanium dioxide anatase composite powder can be synthesized from an organic solvent containing an anionic complex obtained by coordinating a carbonate ion and a peroxide ion to titanium and an amine cation. The visible light-responsive black titanium dioxide anatase composite powder can be obtained by heat-treating the powder, which is obtained by removing the organic solvent from the solution composition, in an air atmosphere. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for producing a black titanium dioxide anatase composite powder for visible light responsive photocatalyst and a method for producing a solution composition for producing the powder.

  Anatase-type titanium dioxide is known to exhibit a photocatalytic function under ultraviolet irradiation, and has attracted much attention (for example, Non-Patent Document 1). Titanium dioxide with anatase type crystal structure can use only a few percent of ultraviolet rays contained in sunlight. For this reason, the application range is limited because the photocatalytic effect cannot be exhibited in a room where there is almost no ultraviolet rays. The visible light response of anatase-type titanium dioxide photocatalyst is very important in terms of effective use of solar energy and expansion of the application range of photocatalytic products.

  Recently, extensive research has been conducted to respond to visible light in addition to ultraviolet rays by modifying titanium dioxide using physical and chemical methods. Dye sensitization method using organic dye (Non-patent Document 2), transition metal ion implantation (Non-patent Documents 3 to 4), part of oxide ions are nitrogen (Non-patent documents 5 to 6) or carbon (non-patent document 2) Research that has been replaced in Patent Document 7) has also been conducted. In addition, research into introducing sulfur (Non-Patent Documents 9 to 10) has also been conducted.

  Recently, there is a report of inserting nitrogen atoms or nitrogen ions into the crystal lattice of titanium dioxide (Patent Document 1). There is also a production report of a titanium dioxide film having a visible light responsive interface prepared by laminating titanium dioxide films formed from coating solutions having different components by a wet process called a molecular precursor method (Non-patent Document 11).

  Thus, the photocatalyst which responds to visible light can be manufactured by making dope of various elements and creating a visible light responsive interface. The physical and chemically modified visible light responsive anatase titanium dioxide has a light yellow to dark yellow color and reflects a portion of the visible light. For this reason, visible light cannot be used effectively.

Each of the manufacturing methods still has a lot of experimental research and has problems to be solved regarding manufacturing.
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  In the above prior art of titanium dioxide powder production, the dye sensitizing method of Non-Patent Document 2 uses an organic dye, so that the organic dye is decomposed from the photocatalytic action due to long-term use, and the performance deteriorates. There is a point.

  In order to replace a part of oxide ions by transition metal ion implantation by the ion implantation method of Non-Patent Documents 3 and 4 and the sputtering method of Non-Patent Document 5 with nitrogen ions, a system close to vacuum and high energy are used in the manufacturing process. In addition, there is a problem that the manufacturing cost increases because the apparatus is complicated and expensive.

  In order to replace some of the oxide ions of Non-Patent Document 6 with nitrogen ions, an atmospheric furnace capable of reduction in an ammonia atmosphere is required in the manufacturing process, and thus there is a problem that the manufacturing cost increases.

In order to replace some of the oxide ions of Non-Patent Document 7 with carbon, it is necessary to heat treat titanium carbide (TiC) powder in air for 36 hours, and then heat treatment in an oxygen atmosphere at 600 ° C. for 5 hours. . In addition to requiring a large amount of energy and time for the heat treatment, oxygen and an atmospheric furnace are required, which increases the manufacturing cost. In order to introduce sulfur in Non-Patent Documents 8 to 10, titanium sulfide (TiS ₂ ) is manufactured by heat treatment in air at a temperature of 500 to 600 ° C. for 24 to 48 hours. Since time is required, there is a problem that the manufacturing cost increases.

  The other element doping methods for producing visible light responsive titanium dioxide described in the background art are for titanium dioxide fine particles or titanium dioxide films formed by physical film formation. As described above, the physical methods of Non-Patent Documents 3 to 5 require enormous capital investment and enormous energy due to the enlargement of the apparatus, and many technical problems remain when assuming mass production. From these problems, it is inevitable to increase the cost of the product.

  In addition, the production method using the chemical reaction described in Non-Patent Documents 6 to 10 requires a lot of energy because the heat treatment atmosphere is changed or a long-time heat treatment is necessary. Inevitable.

  A titanium dioxide film having a visible light responsive interface formed by laminating titanium dioxide films formed from coating liquids having different components by a wet process called a molecular precursor method of Non-Patent Document 11 has a visible light responsive substance as an interface between the laminated films. Therefore, it is inevitable to increase the cost of the product because it is necessary to laminate the titanium dioxide particles even in the production of powder.

  In recent years, the development of materials with low environmental load is desired to develop materials that can produce the desired materials with low pollution and low energy (low heat treatment temperature, short time).

  As described above, there has never been a black anatase-type titanium dioxide powder that responds to visible light and absorbs more visible light by using low VOC (volatile organic compound) and low environmental load components. It was.

  This invention solves the said subject at once, and provides the novel manufacturing method of the precursor solution which can make the black titanium dioxide anatase composite powder which responds to visible light, and black anatase type titanium dioxide powder.

  Another object of the present invention is to provide a black titanium dioxide anatase composite powder and the member having the powder.

  The present inventor has conducted research on a method for producing a solution composition for easily producing a uniform and homogeneous black titanium dioxide anatase composite powder with a simple apparatus. Carbon dioxide, titanium alkoxide, water, and oxidation The solvent composition prepared by the method of reacting an agent in an organic solvent and then adding an amine, or the method of reacting carbon dioxide, titanium alkoxide, water, an oxidizing agent, and an amine in an organic solvent is desolvated. The obtained powder can be formed into a black titanium dioxide anatase composite powder that is believed to be capable of absorbing the entire visible light region by a heat treatment time of 30 minutes in a short time compared with the conventional method at 400 ° C. It has been discovered that the solution composition can be obtained in one pot. As a result, a new black color can be made on the visible light responsive titanium dioxide anatase powder, which until now only had a pale yellow or dark yellow color, so that it could be used for pigments such as black paint with a photocatalytic function. It was.

  The present inventor has already required a heat treatment temperature of about 500 ° C. by using, as a ligand, a polycarboxylic acid not containing nitrogen as a ligand in a titanium complex anion or a carbonate ion by carbon dioxide. Anatase-type titanium dioxide films have been successfully produced at temperatures as low as about 350 ° C. It is shown that a solution composition capable of producing a black titanium dioxide anatase composite powder that responds to visible light can be obtained in one step by treating the powder obtained by removing the solvent from the solution composition at 400 ° C. The invention features. The solution composition of the present invention can be synthesized in one step at room temperature and can be synthesized in a short time of about 1 hour.

  By heat-treating the powder obtained by removing the solvent from the solution composition by a method such as heating or decompression, a black titanium dioxide anatase composite powder that responds to visible light can be produced. Compared with the method for producing visible light responsive titanium dioxide anatase by chemical reaction described in Non-Patent Documents 7 to 10, the heat treatment atmosphere is not required to be adjusted and the heat treatment time can be extremely shortened.

  The present invention is characterized in that carbon dioxide, titanium alkoxide, water and an oxidizing agent are reacted in an organic solvent, and then an amine is added, and a titanium complex anion coordinated with carbonate ions and dioxide ions, an amine cation, A precursor solution for forming a black titanium dioxide anatase composite powder containing carbon dioxide, titanium alkoxide, water, an oxidizing agent, an amine and an oxidizing agent in an organic solvent, and carbonate ions, This is a precursor solution for forming a black titanium dioxide anatase complex powder containing a titanium complex anion coordinated with a dioxide ion and an amine cation. It was found that a black titanium dioxide anatase composite powder responding to visible light was obtained.

  As a result, the conventional technology requires a high vacuum for visible light generation, requires an expensive apparatus that requires a large amount of energy for film formation, changes the atmosphere during the heat treatment process, and requires a lot of processing time. It took 10 hours to produce black titanium dioxide anatase composite powder that responds to visible light with a few tens of minutes of heat treatment if there is an apparatus that can be heat-treated in air by using the present invention. I was able to do that.

  Since this composite powder exhibits a photocatalytic function under visible light as well as ultraviolet rays, it can be applied to indoor deodorized products and daily necessities that have almost no ultraviolet rays, and it can be used as a pigment for paints and plastics. It is possible to make high-performance plastics products such as black paint and dashboard with photocatalytic function. It can also be applied to electrode materials for visible light responsive solar cells. Although an example was given here, it is not limited to these.

  In the present invention, a visible light-responsive black titanium dioxide anatase composite powder composed mainly of titanium dioxide is prepared from a solution composition containing a titanium complex anion coordinated with carbonate ions and dioxide ions and an amine cation. Is done.

  The solution composition used first in the present invention is obtained by reacting carbon dioxide, titanium alkoxide, water and an oxidizing agent in an organic solvent, and then adding an amine. Preferably, the resulting solution composition is uniform and transparent.

  The solution composition used in the second aspect of the present invention is obtained by reacting carbon dioxide, titanium alkoxide, water, an oxidizing agent, and an amine in an organic solvent. Preferably, the resulting solution composition is uniform and transparent.

  Examples of the titanium alkoxide used for preparing the precursor and the precursor solution of the present invention include tetramethoxy titanium, tetraethoxy titanium, tetraisopropoxy titanium, tetra-n-propoxy titanium, and tetra-n-butoxy titanium. However, it is not limited to these.

  The ligand carbonate ion used to prepare the precursor solution of the present invention is introduced from dry ice or the like, but the carbon dioxide source is not limited. The addition amount of the ligand is suitably 1 to 1000 times, more preferably 10 to 100 times that of titanium. When an amount exceeding this is added, it does not react with titanium, so that carbon dioxide is simply added, which is inefficient. On the other hand, when the amount is less than this, the reaction is incomplete, and the stability of the liquid is significantly lowered.

  Examples of amine compounds used for preparing the precursor solution of the present invention include compounds represented by general formula (I), n-propylamine, di-n-propylamine, diisopropylamine, ethyl-n-propylamine, Ethyl isopropylamine, di-n-butylamine, diisobutylamine, di-sec-butylamine, di-ter-butylamine, ethyl-n-butylamine, isopropyl-n-butylamine, di-n-pentylamine, n-hexylamine, dihexyl Examples include, but are not limited to, aliphatic amines having 10 or less carbon atoms in alkyl groups such as amine, dicyclohexylamine, and n-octylamine. When the number of carbon atoms in the alkyl group exceeds 10, the organic component increases, and an impurity level is formed in titanium dioxide in the compound during the heat treatment after desolvation, so that the photocatalytic function is lowered. For this reason, it is difficult to obtain a high-performance powder.

（式中、Ｒ^１、Ｒ^２、Ｒ^３、Ｒ^４は水素または炭素数が１〜１０のアルキル基であって、Ｒ^１〜Ｒ^４中少なくとも一つがアルキル基を示し、Ｒ^１〜Ｒ^４はそれぞれ同じでも異なっていてもよい。）

^{(Wherein, R 1, R 2, R} 3, R 4 is a hydrogen or an alkyl group having 1 to 10 carbon ^atoms, at least one of R 1 to R ⁴ represents an alkyl ^group, R 1 to R ⁴ May be the same or different.)

  Examples of amines used in the present invention include compounds represented by formula (II) or (III), pyridine derivatives such as pyridine, 4-methylpyridine, 4-aminopyridine, 4-dimethylaminopyridine, benzylamine, N , Benzylamine derivatives such as N-dimethylbenzylamine, aniline derivatives such as N, N-dimethylaniline, N, N-dimethyl-p-toluidine, and the like, but are not limited thereto.

（式中、Ｒ^５はジメチルアミノ基、ジエチルアミノ基、水素または炭素数が１〜１０のアルキル基、ｎは０または１の整数、Ｒ^６、Ｒ^７は水素または炭素数が１〜１０のアルキル基を示し、Ｒ^６、Ｒ^７はそれぞれ同じでも異なっていてもよい。）

(Wherein R ⁵ is a dimethylamino group, diethylamino group, hydrogen or an alkyl group having 1 to 10 carbon atoms, n is an integer of 0 or 1, R ⁶ and R ⁷ are hydrogen or alkyl having 1 to 10 carbon atoms, And R ⁶ and R ⁷ may be the same or different.

(In the formula, R ⁸ represents a dimethylamino group, a diethylamino group, hydrogen, or an alkyl group having 1 to 10 carbon atoms.)

  The amine compound used in the present invention is based on the formation of a stable liquid such that the salt or addition compound produced by the reaction is easily dissolved in water and alcohol, and the crystals do not precipitate over time. Selected. It is also effective to suppress the precipitation of crystals by using two or more amines in combination. The amount of amine added is suitably from equimolar to 10 times the amount of titanium alkoxide. More preferably, an equimolar to 5-fold amount is appropriate. When an amount exceeding this is added, the amount of organic matter increases, and impurity levels are formed in the titanium dioxide during the heat treatment after desolvation, so that the photocatalytic function is lowered. When the amount is less than this, the reaction is incomplete, and the stability of the liquid is significantly reduced.

  Examples of the oxidizing agent used in the present invention include hydrogen peroxide, nitric acid, nitrous acid, dinitrogen trioxide, dinitrogen tetroxide, sulfuric acid, ozone, oxygen, perchloric acid, chloric acid, chlorous acid, hypochlorous acid. Examples include, but are not limited to, chloric acid, bleaching powder, peroxosulfuric acid, lead oxide, and barium peroxide. These may be used alone in combination with water, or two or more thereof may be combined. In view of simplicity, aqueous solution, and few impurities, hydrogen peroxide solution is most suitable.

  Examples of the organic solvent used in the solution of the present invention include methanol, ethanol, propanol, isopropanol, n-propanol, n-butanol, isobutanol, t-butanol and other lower alcohols, ethylene glycol, propylene glycol and other glycols, ethylene glycol Examples thereof include glycol ethers such as monobutyl ether and propylene glycol monomethyl ether, but are not limited thereto. These organic solvents may be used alone or in combination of two or more.

  The solution composition of the present invention comprises reacting an oxidizing agent such as carbon dioxide, titanium alkoxide and hydrogen peroxide solution in a lower alcohol and then adding an amine, or carbon dioxide, titanium alkoxide, amine and hydrogen peroxide solution, etc. It can be obtained by reacting the oxidant in a lower alcohol. The amount of the oxidizing agent is suitably 0.001 times to 10 times, more preferably 0.05 times to 5 times that of the titanium complex.

  The solvent is volatilized by any method such as heating or reduced pressure, and heat treatment at a temperature of 200 ° C. to 800 ° C. is performed. More preferably, baking is performed at a temperature of 250 ° C. to 650 ° C. Also, the firing temperature can be divided into several stages. Firing may be gradually raised to a high temperature in a muffle furnace, or may be put into a furnace that has already been set to a constant temperature. The atmosphere during the heat treatment may be air, but may be performed in an inert gas as necessary. Examples of the inert gas include helium, argon, cryptant, xenon, and nitrogen, but are not limited thereto. These gases may be used alone or in combination of two or more. In addition, oxygen may be mixed up to about 15%.

  The heat treatment time of the powder obtained by removing the solvent from the solution composition by any method can be appropriately selected and set by those skilled in the art. For example, it can be performed in 10 seconds to 5 hours, preferably 5 minutes to 2 hours. In addition, the solvent composition and the heat treatment step can be performed simultaneously by bringing the solution composition directly into contact with the substrate by a method such as spraying while keeping the temperature range of the heat-resistant substrate such as an evaporating dish, Can be made in one step.

  In addition, the said heat processing time and the heat processing process are illustrations, and are not limited to these.

  The titanium dioxide anatase composite powder thus obtained has a characteristic black color and has a photocatalytic function that responds to visible light as well as ultraviolet light.

  The method of producing the powder having titanium dioxide as a main component and the member having the powder obtained by the present invention is not limited. Moreover, about the said usage method, it is an illustration and it is not limited to these.

  The manufacturing method of the black titanium dioxide anatase composite powder for visible light responsive photocatalyst of the present invention and the manufacturing method of the solution composition for forming the powder will be described more specifically in the following examples. It goes without saying that the present invention is not limited to the best mode for carrying out the invention described above, and various other configurations can be adopted without departing from the spirit of the present invention.

  The present invention will be described below with reference to examples, but the present invention is not limited to these examples. Example 1 relates to a method for producing a solution composition for forming a black titanium dioxide anatase composite powder for visible light responsive photocatalyst.

[Example 1]
Ethanol 30 g, titanium tetraisopropoxide 6.6 g (23.2 mmol), and dry ice 50 g were added to the 100 ml Erlenmeyer flask little by little in the solution, and 2.6 g (22.9 mmol) of 30% aqueous hydrogen peroxide was added therein. ) And 3.4 g (46.6 mmol) of butylamine was added dropwise with stirring at room temperature. After completion of the dry ice charging, the reaction was carried out by stirring at room temperature for 1 hour to obtain a pale yellow transparent solution.

[Example 2]
Ethanol was evaporated on an evaporating dish in which the solution of Example 1 was heated to a temperature of 70 ° C. to obtain a yellow powder. This powder was ground and heat-treated in a muffle furnace in an air atmosphere at a temperature of 400 ° C. for 30 minutes. When the crystal structure of the obtained black powder was examined using an X-ray diffractometer, no peaks corresponding to titanium nitride, titanium carbide, etc. were observed, and it was titanium dioxide having only anatase crystal structure (FIG. 1). .

  Elemental analysis revealed that it contained a large amount of carbon, nitrogen, hydrogen and excess oxygen.

  In the following examples, in order to investigate the photocatalytic function of the prepared titanium dioxide powder, performance evaluation was carried out by methylene blue decomposition experiments under ultraviolet irradiation and visible light irradiation.

[Example 3]
The powder prepared in Example 1 is ground and placed in 15 mL of a 0.1 mmol / L methylene blue aqueous solution. After stirring and dispersing with a stirrer, light close to ultraviolet rays and sunlight using black light as a light source. Visible light was irradiated using true light that emits light (FIG. 2). For visible light, ultraviolet light contained in true light was cut by an ultraviolet cut filter, and light of 400 nm or more was used. The light intensity was 1.2 mW / cm ^{2 at} 365 nm for ultraviolet light and 0.8 mW / cm ² above 400 nm for visible light. The absorbance of methylene blue was measured every 20 minutes up to 180 minutes. In order to examine the amount of methylene blue adsorbed on the powder surface, a sample placed in the dark as a reference was also measured.

  As a result, the measurement results shown in FIG. 3 were obtained, and it was found that the prepared black powder was a black titanium dioxide anatase complex having a photocatalytic function responsive to visible light.

  Table 1 shows the decomposition ratio of methylene blue when irradiated with ultraviolet rays, and Table 2 shows the decomposition ratio of methylene blue when irradiated with visible light, in comparison with the decomposition ratio of the comparative example described below.

[Comparative Example 1]
Ethanol was evaporated on an evaporating dish in which the solution of Example 1 was heated to a temperature of 70 ° C. to obtain a yellow powder. When this powder was ground and heat-treated in an air atmosphere at a temperature of 500 ° C. for 30 minutes in a muffle furnace, it was yellow instead of black. When the crystal structure of the obtained yellow powder film was examined using an X-ray diffractometer, it was an anatase crystal structure titanium dioxide having a slight rutile crystal structure (FIG. 1).

  As a result of the methylene blue decomposition test conducted in the same manner as in Example 3, the visible light responsiveness of this powder was as low as about 1/3 at the end of the experiment as compared with Example 1. This is probably because the visible light response component has disappeared because the heat treatment temperature was not appropriate.

  The present invention relates to a method for producing a black titanium dioxide anatase composite powder for visible light responsive photocatalyst that generates a photocatalytic function that also responds to visible light, and a method for producing a solution composition for forming the powder. It is well known that titanium dioxide having an anatase type crystal structure is polarized by ultraviolet light and acts as a catalyst. The titanium dioxide powder acts as an oxidation catalyst when exposed to light, and decomposes organic substances on the surface, so that it exhibits excellent antifouling, sterilizing and deodorizing effects. The titanium dioxide film can also be used as a solar cell material as an n-type semiconductor. Titanium dioxide with anatase type crystal structure can use only a few percent of ultraviolet rays contained in sunlight. For this reason, the application range is limited because the photocatalytic effect cannot be exhibited in a room where there is almost no ultraviolet rays. The visible light response of anatase-type titanium dioxide photocatalyst is very important in terms of effective use of solar energy and expansion of the application range of photocatalytic products.

  The powder obtained by desolvating an organic solvent containing an anion complex in which carbonate ion and peroxide ion are coordinated to titanium of the present invention and an amine cation is visible by heat treatment at 400 ° C. in an air atmosphere. A black titanium dioxide anatase composite powder responsive to light is obtained. This powder conventionally has a black color different from visible light responsive titanium dioxide, which was only pale yellow or deep yellow. For this reason, it is thought that a highly efficient photocatalyst material can be manufactured by absorbing the whole visible light region.

  Since this composite powder exhibits a photocatalytic function even under visible light, it can be applied to indoor deodorized products and daily necessities with less ultraviolet light, and it can also be used as a pigment for paints and plastics to have a photocatalytic function. It is possible to make highly functional plastic products such as black paint and dashboard.

  The present invention provides a method for producing a black titanium dioxide anatase composite powder for visible light responsive photocatalyst and a method for producing a solution composition for forming the powder.

The figure which shows the X-ray-diffraction result of the titanium oxide by Example 1 and Comparative Example 1. Diagram showing methylene blue decomposition test The figure which shows the result of the methylene blue decomposition test

Claims (6)

  Carbon dioxide, titanium alkoxide, water and an oxidizing agent are reacted in an organic solvent, then an amine is added, and a titanium complex anion coordinated with carbonate ion and dioxide ion and an amine cation are contained. A method for producing a precursor solution for forming a black titanium dioxide anatase composite powder for visible light responsive photocatalyst.   Visible light characterized by containing a titanium complex anion and an amine cation in which carbon dioxide, titanium alkoxide, water, oxidant, and amine are reacted in an organic solvent and carbonate ions and dioxide ions are coordinated. A method for producing a precursor solution for forming a black titanium dioxide anatase composite powder for a responsive photocatalyst. The amine cation is represented by the general formulas (I) to (III).

^{(Wherein, R 1, R 2, R} 3, R 4 is a hydrogen or an alkyl group having 1 to 10 carbon ^atoms, at least one of R 1 to R ⁴ represents an alkyl ^group, R 1 to R ⁴ May be the same or different)

(Wherein R ⁵ is a dimethylamino group, diethylamino group, hydrogen or an alkyl group having 1 to 10 carbon atoms, n is an integer of 0 or 1, R ⁶ and R ⁷ are hydrogen or alkyl having 1 to 10 carbon atoms, And R ⁶ and R ⁷ may be the same or different from each other)

(Wherein R ⁸ represents a dimethylamino group, a diethylamino group, hydrogen or an alkyl group having 1 to 10 carbon atoms)
The method for producing a precursor solution for forming a black titanium dioxide anatase composite powder for visible light responsive photocatalyst according to claim 1 or 2, comprising at least one selected from the group represented by .   A precursor solution for forming a black anatase powder for visible light responsive photocatalyst produced by the method according to claim 1.   The manufacturing method of the black titanium dioxide anatase composite powder for visible light responsive photocatalysts produced by heat-processing the solute in the solution composition of Claim 4.   A method for producing a photocatalyst member having the black titanium dioxide anatase composite powder for visible light responsive photocatalyst according to claim 5.

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