JP2010088964A - Method for producing oxidized titanium particle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To increase the photocatalytic activity of titanium oxide for a photocatalyst. <P>SOLUTION: A method for producing titanium oxide for the photocatalyst comprises the steps of: partially dissolving the oxidized titanium particle dispersed in a liquid; washing the oxidized titanium particle, whose particle size becomes smaller, with water; drying the washed oxidized titanium particle; and heat-treating the dried oxidized titanium particle in an oxygen-containing atmosphere. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a titanium oxide for photocatalyst comprising titanium oxide having a high photocatalytic activity and a method for producing the same. Further, the obtained titanium oxide for photocatalyst is disposed under irradiation of ultraviolet rays, and an organic phosphorus compound, an organic chlorine compound liquid, etc. The present invention relates to a decontamination method for decontaminating chemical warfare agents.

Photocatalysts made of titanium oxide have the action of decomposing various chemical substances that are photoexcited and come into contact. They decompose and remove malodorous components such as acetaldehyde and mercaptans, disinfect and remove mold and algae, and oxidize nitrogen oxides It is used in various fields for the purpose of antifouling, deodorization, sterilization including decomposition and removal.
Various methods for enhancing the photocatalytic function of the photocatalyst have been proposed. For example, methods such as increasing the surface area by using particles having a small particle size, increasing the crystallinity of the particles, performing charge separation, and adjusting the band gap of the particles have been proposed. However, conventional photocatalysts have not been sufficient for use in high-concentration gas decomposition, water treatment, and the like.

In addition, when using photocatalyst particles, it is necessary to fix them on a substrate. However, in order to fix them on a substrate, it is applied together with a binder, or a titanium oxide photocatalyst is added with an alkali compound and hydrogen peroxide. It has been proposed to disperse the titanium oxide photocatalyst particles in a solution containing a solution, partially dissolve the titanium oxide photocatalyst particles, and apply a photocatalyst coating agent and method to the partially dissolved solution. (For example, refer to Patent Document 1).
JP 2007-146138 A

  It is an object of the present invention to provide a titanium oxide having a high photocatalytic activity, and can be applied to any titanium oxide produced by any method such as a gas phase method or a liquid phase method. It is an object of the present invention to provide a titanium oxide for photocatalysts which is easily excellent in photocatalytic function and has a large photocatalytic activity.

The present invention relates to the production of titanium oxide for photocatalysts in which titanium oxide particles having a reduced particle size after partially dissolving titanium oxide particles dispersed in a liquid are washed with water, dried and then heat-treated in an oxygen-containing atmosphere. Is the method.
Moreover, it is the manufacturing method of the said titanium oxide for photocatalysts which heat-processes at the temperature of 100 to 500 degreeC.
In the method for producing titanium oxide for photocatalyst, the titanium oxide particles are partially dissolved by adding hydrogen peroxide solution and a basic substance, or adding hydrogen peroxide solution and an acidic substance.
It is the said manufacturing method of the titanium oxide for photocatalysts which melt | dissolves 10% or more of the mass of a titanium oxide particle.

In addition, after titanium oxide particles dispersed in the liquid are partially dissolved and the titanium oxide particles having a small particle size are washed with water and dried, they are heated at a temperature of 100 ° C. to 500 ° C. in an oxygen-containing atmosphere. The chemical warfare agent decontamination method decomposes the chemical warfare agent under irradiation of ultraviolet rays with the obtained titanium oxide for photocatalyst.
In addition, after titanium oxide particles dispersed in a liquid are partially dissolved and the titanium oxide particles having a reduced particle size are washed with water and dried, the particle size is in an oxygen-containing atmosphere at a temperature of 100 ° C. to 500 ° C. Cylindrical ceramics having a three-dimensional network structure carrying titanium oxide particles obtained by heat treatment is disposed in a reaction chamber formed between double tubes formed of a light transmissive member, A light source that emits ultraviolet rays is disposed on the inner surface and the outer surface of the double tube, and one end portion of the reaction chamber has an inflow port of a contaminated gas containing a chemical warfare agent, and the other end portion of the reaction chamber has This is a chemical warfare agent decontamination device having a decontamination gas outlet.

  In the method for producing titanium oxide for photocatalysts of the present invention, the titanium oxide particles are partially dissolved to increase the specific surface area by making the particles finer, to increase the specific surface area by introducing pores into the titanium oxide particles, the particle surface, etc. It is considered that the crystallinity of the surface of the titanium oxide particles is increased and the photocatalytic activity is improved by heat treatment in an oxygen-containing atmosphere. As a result, fields that utilize various photocatalytic functions such as air purifiers and deodorizers, water purification equipment, or protective films, dielectric films, semiconductor films, UV-cut films, dye-sensitized solar cells, etc. It is also effective in fields.

The present invention has found that titanium oxide particles having high photocatalytic activity can be provided by partially dissolving titanium oxide particles used as a photocatalyst and then heat-treating them in an oxygen-containing atmosphere. Moreover, it discovered that it was possible to obtain a titanium oxide with a big photocatalytic action by processing similarly about the commercially available titanium oxide particle for photocatalysts.
Various proposals have been made to enhance the photocatalytic action of titanium oxide for photocatalysts. In particular, the method of reducing the particle size by partially dissolving titanium oxide particles suppresses recombination of the generated electrons and holes, and can increase the photocatalytic activity by a relatively simple method. Known as a method.
On the other hand, the present invention can further enhance the photocatalytic activity by further heating in an oxygen-containing atmosphere at a predetermined temperature after partially dissolving to reduce the particle size. It is what I found.

The partial dissolution of titanium oxide particles involves dissolving a predetermined amount of titanium oxide particles by allowing hydrogen peroxide water and basic substances such as ammonia water or acidic substances such as hydrochloric acid to act on the titanium oxide particles. Can be done by.
As a result, a mixed liquid of titanium oxide particles having a particle size reduced by dissolution and a peroxotitanium complex formed from the titanium oxide particles can be obtained. The produced peroxotitanium complex exists mainly as an anion when the pH is 3 or more, and exists mainly as a cation when the pH is 3 or less.
Therefore, when a hydrogen peroxide solution and a basic substance are added at the time of partial dissolution of titanium oxide particles, a mixed solution composed of an anion of peroxotitanium complex and titanium oxide particles can be obtained. On the other hand, when a hydrogen peroxide solution and an acidic substance are added, a mixed solution composed of cations of peroxotitanium complex and titanium oxide particles can be obtained.
Removal of components such as a peroxotitanium complex dissolved from the titanium oxide particles and a peroxotitanium complex from the mixed liquid containing the titanium oxide particles can be performed by a separation operation such as filtration and washing with water.

  For example, when removing a dissolved component as an anion of a peroxotitanium complex from a mixture containing a peroxotitanium complex and titanium oxide particles, the peroxotitanium contained in the mixture by centrifugation or decantation is used. A suspension of titanium oxide particles can be prepared by separating and removing ionic substances other than water derived from anions and basic substances of the titanium complex.

Moreover, the anion of the peroxotitanium complex in the mixed solution is obtained by stirring, heating, sonicating the mixed solution of the anion of the peroxotitanium complex formed by partial dissolution of the titanium oxide particles and the titanium oxide particles. Is precipitated as a polymer of peroxotitanium hydrate, and subjected to a treatment such as centrifugation or filtration to separate and recover a mixture of the polymer of peroxotitanium hydrate and titanium oxide as a precipitate.
Next, an acidic substance is added to the precipitate, and the polymer of peroxotitanium hydrate is dissolved again as a cation of peroxotitanium hydrate by adjusting the pH to 3 or less, more preferably 1 or less. Can do.
After re-dissolving the polymer of peroxotitanium hydrate contained in the precipitate as a cation of the peroxotitanium complex, a treatment such as ion exchange reaction or centrifugation is performed to remove the peroxotitanium complex contained in the liquid. A suspension of titanium oxide particles can be prepared by removing ionic substances other than water derived from basic substances or acidic substances added to dissolve cations and titanium oxide particles.

  In addition, a mixture of cation and titanium oxide of a peroxotitanium complex produced by adding hydrogen peroxide and an acidic substance to partially dissolve titanium oxide particles can be used for treatment such as ion exchange reaction or centrifugation. In this way, the cation of the peroxotitanium complex contained in the mixed solution and ionic substances other than water derived from the acidic substance can be removed to prepare a titanium oxide suspension.

As basic substances used for partial dissolution of titanium oxide particles, ammonia water, alkali metal hydroxide aqueous solution, tetraalkylammonium aqueous solution, etc. can be used, but they can be easily removed by ion exchange, evaporation, etc. Ammonia water, tetraalkylammonium and the like that do not contain a metal element affecting the activity are preferable, and ammonia water is particularly preferable.
The amount of the basic substance when the titanium oxide particles are partially dissolved using hydrogen peroxide and a basic substance is preferably 4 times or less, more preferably 2 times or less with respect to the number of moles of titanium. Is the amount.

  Further, when hydrogen peroxide water and a basic substance are added to the titanium oxide particles, the amount of titanium oxide particles dissolved changes according to the amount of basic substance added, and a peroxotitanium complex is generated from the dissolved titanium oxide particles. Therefore, the amount of titanium oxide dissolved can be adjusted by adjusting the amount of basic substance added.

Examples of the acidic substance used for partially dissolving titanium oxide particles and dissolving a polymer of peroxotitanium hydrate include dilute hydrochloric acid, dilute sulfuric acid, and dilute nitric acid. Of these acids, dilute hydrochloric acid, dilute nitric acid and the like, which are easy to remove by treatment such as ion exchange reaction or centrifugation and have a relatively small influence on the photocatalytic activity, are preferred, and dilute hydrochloric acid is particularly preferred.
Further, when hydrogen peroxide water and an acidic substance are added to the titanium oxide particles, the amount of titanium oxide particles dissolved changes in accordance with the amount of hydrogen peroxide water added as in the case of adding a basic substance.
When using either a basic substance or an acidic substance, if the dissolved amount is too small, the effect of improving the photocatalytic activity is low, and if the dissolved amount is too large, the recovery rate of the titanium oxide particles decreases. Specifically, the effect can be obtained by dissolving 10% by mass with respect to the mass of the titanium oxide particles before dissolution.

It is preferable to sufficiently remove the acidic substance added from the mixed liquid formed by partial dissolution of the titanium oxide particles, ammonium ion derived from the basic substance, chlorine ion, or other ON. Since the residual amount of these ions adversely affects the photocatalytic activity of the finally obtained titanium oxide particles, it is desirable to treat them sufficiently. In particular, chlorine ions and the like are considered to decrease the photocatalytic activity, and thus must be sufficiently removed.
These ions can be removed by washing with sufficient water when decanting, filtering, centrifuging, etc., or by removing ion substances by ion exchange reaction, reverse osmosis, or a combination of these. It is preferable to do.

  In addition, the amount of the hydrogen peroxide solution added for partial dissolution of the titanium oxide particles is such that in the partial dissolution step of titanium oxide, the added hydrogen peroxide solution decomposes without being involved in the reaction. It is preferable to add the hydrogen peroxide / titanium molar ratio in excess of 1.

Next, moisture is removed from the liquid in which the titanium oxide particles are dispersed by heat drying. In heat drying, when heated to a high temperature, titanium oxide particles having a particle size reduced by partial dissolution may cause aggregation or crystal growth during drying.
Therefore, it is preferable to dry the titanium oxide particles at a temperature of 25 ° C. to 50 ° C. for 12 hours to 96 hours. When the drying temperature is lower than 25 ° C., moisture cannot be sufficiently removed. When the drying temperature is higher than 50 ° C., aggregation of particles or the like occurs, which is not preferable.

After sufficiently removing moisture from the titanium oxide particles as described above, titanium oxide particles having excellent photocatalytic function and crystallinity are prepared by heat treatment in an oxygen-containing atmosphere at a temperature of 100 to 500 ° C. or lower. be able to.
When the temperature is lower than 100 ° C., the photocatalytic function by the heat treatment cannot be sufficiently enhanced. On the other hand, when the heat treatment is performed at a temperature higher than 500 ° C., the specific surface area decreases due to crystallization of the titanium oxide particles. This may cause a decrease in photocatalytic activity. The heating time is preferably 30 minutes to 24 hours.

In the present invention, titanium oxide particles dispersed in a liquid are partially dissolved and dried using hydrogen peroxide and a basic substance or acidic substance, and then subjected to heat treatment in an oxygen-containing atmosphere, whereby titanium oxide particles are obtained. It is considered that the photocatalytic activity is improved by increasing the specific surface area by making the particles fine, increasing the specific surface area by introducing pores into the titanium oxide particles, and changing the state of the surface of the titanium oxide particles.
In addition, after the titanium oxide particles are partially dissolved, the photocatalytic action can be further enhanced by removing the soluble component and the ionic substance.

Examples of the titanium oxide particles that can be used for partial dissolution in the production process of the titanium oxide particles of the present invention include various crystalline titanium oxide particles.
For example, various titanium oxide particles sold as titanium oxide particles for photocatalysts can be used. For example, P-25 (manufactured by Nippon Aerosil Co., Ltd.), ST-01 (manufactured by Ishihara Sangyo), AMT-100 (manufactured by Teika) and the like can be mentioned.

  Further, the titanium oxide particles used as a raw material in the method for producing a titanium oxide of the present invention are not limited to those sold as the above-described titanium oxide particles for photocatalyst, but as in the method described in Japanese Patent No. 3490013. Peroxide titanium hydrate polymer precipitation by adding hydrogen peroxide solution to titanium-containing raw material aqueous solution to form peroxotitanium complex, and then leaving or heating the solution obtained by adding basic substance After forming the product, after removing dissolved components other than water derived from the titanium-containing raw material aqueous solution, titanium oxide produced from a solution for forming titanium oxide obtained by making hydrogen peroxide solution act to make a solution. Particles may be used.

  The titanium oxide for photocatalyst obtained by the present invention is used in fields other than various fields utilizing photocatalytic functions such as air purifiers and deodorizers, water purification equipment, protective coatings, dielectric films, semiconductor films, and UV-blocking. It is also used in fields such as coatings and dye-sensitized solar cells.

In addition, since the titanium oxide for photocatalyst obtained by the method of the present invention has a large function as a photocatalyst, it is suitable for decontamination of chemical warfare agents including sarin, tabun and mustard gas.
In chemical warfare agent decontamination sites, a large amount of contaminated air must be treated in a short period of time. For this reason, contaminated air is forcibly introduced into the decontamination equipment to efficiently decompose chemical warfare agents such as sarin. It will be necessary.
The decontamination apparatus needs to be brought into contact with a gas containing a chemical warfare agent in an environment where light is irradiated onto the photocatalyst made of titanium oxide particles. For this reason, it is preferable to carry | support a photocatalyst in the area | region where the light of the surface of a support | carrier reaches enough.
For example, an ultraviolet lamp or the like that irradiates ultraviolet light having a wavelength that acts on the photocatalyst is placed near the plate when the photocatalyst made of titanium oxide particles is carried on the surface of the porous plate, and the ultraviolet ray is irradiated. can do.
In addition, a photocatalyst made of titanium oxide particles is carried on the inner and outer surfaces of a carrier having a cylindrical three-dimensional network structure, and a cylindrical tube carrying a photocatalyst as an ultraviolet irradiation means of a straight tubular ultraviolet lamp or ultraviolet radiation fluorescent lamp. Irradiation efficiency can be improved by disposing a plurality of ultraviolet irradiation means on the inner surface of the carrier and also on the outer surface.

FIG. 1 is a view for explaining a decontamination apparatus for chemical warfare agents according to the present invention, and FIG. 1 (A) is a side view for explaining a main part of a part of the decontamination apparatus. These are sectional views in the AA 'line in Drawing 1 (A).
The chemical warfare agent decontamination apparatus 1 according to the present invention is a double-layered material in which a photocatalyst carrier 2 made of a cylindrical ceramic carrier having a three-dimensional network structure carrying titanium oxide particles is formed of an ultraviolet light transmissive material member 3. It is mounted inside the reaction tube 4 consisting of a tube. Ultraviolet lamps 5 are arranged inside and outside the reaction tube.
Each reaction tube 4 is connected with a contaminated gas supply tube 6 and a decontamination gas discharge tube 7, and the contaminated gas containing chemical warfare agent is supplied from the contaminated gas supply tube 5 to the reaction tube 4. The surface of the photocatalyst carrier 2 disposed in the reaction tube 4 is irradiated with ultraviolet rays, and after the chemical warfare agent is decomposed, it is discharged from the decontamination gas discharge tube 7.

The photocatalyst carrier 2 carrying titanium oxide particles can be prepared by applying a coating agent containing titanium oxide particles to a cylindrical ceramic carrier made of silica and alumina having a three-dimensional network structure. The coating agent can be prepared by adding titanium oxide particles to various binders, but the photocatalytic activity is reduced by mixing titanium oxide particles with a peroxotitanium liquid prepared from a titanium compound to form a coating agent. This is preferable because it can be supported on a carrier without using it.
In addition, a cylindrical ceramic carrier having a three-dimensional network structure that can be used as a carrier is impregnated with a dispersion of a ceramic or a precursor thereof in a foam of a synthetic resin such as a cylindrical polyurethane, and then fired. Can be manufactured.

The present invention will be described below with reference to examples and comparative examples.
Example 1
Preparation of Titanium Oxide Particles To a solution obtained by diluting 20 ml of a 60 mass% aqueous solution of titanium tetrachloride to 2000 ml with water, a 10-fold diluted solution of 25 mass% ammonia water was added dropwise to adjust the pH to 7, and the gel-like gel Titanium hydroxide was precipitated, washed by filtration, and the filter residue was made up to 600 ml with water.
Next, 80 ml of 30% by weight hydrogen peroxide water and water were added and allowed to stand for 12 hours, and then 40 ml of 30% by weight hydrogen peroxide water was further added while maintaining the temperature of the solution at 7 ° C. A peroxotitanic acid aqueous solution was obtained.
This solution was heat-treated at 180 ° C. for 2.5 minutes using a microwave hydrothermal treatment apparatus (MARS5 manufactured by CEM) to obtain a crystalline titanium oxide particle-dispersed liquid. The produced crystalline titanium oxide fine particle dispersion liquid had a titanium oxide content of 0.98% by mass.

Partial dissolution of titanium oxide particles Next, 500 ml of aqueous titanium oxide particle dispersion (with a titanium oxide content of 4.9 g) was added with 10% by mass ammonia water so that the ammonia / titanium molar ratio was 1.25. After the addition, 49 ml of a 30% strength by weight hydrogen peroxide solution was added, and this was stirred at 25 ° C. for 2 days to partially dissolve the titanium oxide particles to obtain a yellowish white mixed liquid containing titanium oxide and titanium-containing ions. It was.
The obtained mixed liquid was centrifuged at 11,000 rpm for 20 minutes using a centrifuge (Kokusan H-2000A2), and separated into a yellowish white precipitate and a supernatant liquid to obtain a precipitate.

Furthermore, 400 ml of a 10 mass% hydrochloric acid aqueous solution was added to the obtained precipitate and stirred at 25 ° C. for 12 hours to dissolve components other than titanium oxide to obtain a brown mixed solution. Next, the mixture is centrifuged at 11,000 rpm for 20 minutes using a centrifuge (Kokusan H-2000A2), separated into a precipitate and a brown supernatant, and the dissolved components contained in the supernatant are removed and precipitated. I got a thing.
After adding 200 ml of water to the resulting precipitate and stirring to disperse, 100 ml of amphoteric ion exchange resin (Amberlite MB-1 made by Organo) was gradually added and stirred to remove ammonium ions and chlorine ions. The amphoteric ion exchange resin was separated to obtain a titanium oxide suspension having a pH of 6.5.

Measurement of partial dissolution rate Measurement of Partially Dissolved Titanium Oxide 0.5 ml of a mixed solution containing titanium oxide and titanium-containing ions obtained after partial dissolution was sampled and cooled, 20 ml of a 4-fold diluted solution of 96 mass% sulfuric acid and a concentration of 30 mass. After adding 0.5 ml of% hydrogen peroxide water, the total volume was adjusted to 50 ml with water.
Next, the amount of dissolved titanium oxide was determined by measuring the absorbance of the solution obtained by ultrafiltration with a spectrophotometer (UV3150, manufactured by Shimadzu Corporation) at a wavelength of 410 nm.
The standard solution used for the colorimetric measurement was 1 ml of a titanium standard solution (concentration 1000 ppm manufactured by Wako Pure Chemical Industries), 20 ml of a 4-fold diluted solution of 96 mass% sulfuric acid and 30 mass% hydrogen peroxide water while cooling. It was prepared by adding 0.5 ml and bringing the total volume to 50 ml with water.

2. Measurement of the total amount of titanium oxide 0.5 ml of the mixed solution containing titanium oxide and titanium-containing ions obtained after partial dissolution is collected, and 10 ml of a 2-fold diluted solution of 96 mass% sulfuric acid is added to generate white smoke of sulfuric acid. The titanium compound was completely dissolved by heating.
Next, after cooling, 2 ml of 30% hydrogen peroxide solution was added, and after making the total volume 50 ml with water, the amount of titanium oxide dissolved by measuring the absorbance at a wavelength of 410 nm with a spectrophotometer (Shimadzu Corporation UV3150) Asked.
Then the partial dissolution rate is
Partial dissolution rate (%) = partially dissolved titanium oxide mass / total titanium oxide mass × 100
Calculated by
The partial dissolution rate was 60%.

Drying treatment The obtained titanium oxide suspension was heated at 50 ° C. for 24 hours to obtain a titanium oxide powder.
Heat treatment The dried titanium oxide powder was heat-treated in air at 150 ° C for 1 hour and 30 minutes to prepare titanium oxide for photocatalyst.

Measurement of average particle diameter The obtained titanium oxide for photocatalyst was measured by X-ray diffraction measurement with an X-ray diffractometer (X'Pert PRO, manufactured by PANalytical) using a copper target under an acceleration voltage of 45 kV and a current of 40 mA. Using the obtained X-ray diffraction measurement results, the crystallite diameter of 6.79 nm calculated using the following Scherrer equation from the observed X-ray diffraction peak of the anatase (101) plane was taken as the average particle diameter.
D = Kλ / βcos θ
D: Average crystallite diameter, λ: X-ray wavelength, β: Half width of diffraction peak, θ: Bragg angle, K: Scherrer constant

Measurement of Photocatalytic Activity A 26 × 39 mm glass plate on which 2.5 mg of titanium oxide was applied and dried to form a photocatalytic film was placed in a 1 dm ³ glass reaction vessel. At 25 ° C., acetaldehyde was poured into a glass container to a concentration of 1000 ppm, adsorbed for 60 minutes, irradiated with an ultraviolet lamp (Toshiba BLB20W) at an irradiation intensity of 1 mW / dm ³ , and acetaldehyde concentration time Was measured using a gas chromatograph (Shimadzu GC-14B) and a gas chromatograph mass spectrometer (Shimadzu CMS-QP2010).
The photocatalytic oxidative decomposition reaction of acetaldehyde was evaluated as a primary reaction represented by the following reaction rate equation.
ln (C / C ₀ ) = − kt
Here, C is the acetaldehyde concentration, C ₀ is the initial concentration, k is the first-order reaction rate constant, and t is the time. Using the measured acetaldehyde concentration, the decomposition rate constant for the decomposition of acetaldehyde was determined from the above equation. 0.0021 / min ⁻¹ .

Comparative Example 1
In Example 1, the titanium oxide powder prepared by drying the titanium oxide suspension obtained by partial dissolution treatment was used as a photocatalyst without heat treatment, and the decomposition rate constant of acetaldehyde was set as in Example 1. It was 0.0017 / min ⁻¹ when measured.

Example 2
Partial dissolution process To 4g of titanium oxide for photocatalyst (ST-01, manufactured by Ishihara Sangyo), 10% by mass ammonia water was added so that the ammonia / titanium molar ratio was 1.25, and 30% by mass peroxide was oxidized. 40 ml of hydrogen water was added to 400 ml with water, and this was stirred at 25 ° C. for 2 days to partially dissolve the titanium oxide powder, thereby obtaining a yellowish white mixed liquid containing titanium oxide and a peroxotitanium complex.
The obtained mixed liquid was centrifuged at 11,000 rpm for 20 minutes using a centrifuge (Kokusan H-2000A2) to separate it into a yellowish white precipitate and a supernatant.

Further, 400 ml of a 3.5-fold diluted aqueous hydrochloric acid solution having a concentration of 35% by mass was added to the resulting precipitate and stirred at 25 ° C. for 12 hours to dissolve portions other than titanium oxide to obtain a brown mixed solution.
Next, the mixture is centrifuged at 11,000 rpm for 20 minutes using a centrifuge (Kokusan H-2000A2), separated into a precipitate and a brown supernatant, and the dissolved components contained in the supernatant are removed. A precipitate was obtained.
Next, 200 ml of purified water was added to the obtained precipitate, and the precipitate was dispersed by stirring and ultrasonic treatment, and then 100 ml of an amphoteric ion exchange resin (Amberlite MB-1 manufactured by Organo) was gradually added and stirred. Then, ammonium ions and chlorine ions were removed, and the amphoteric ion exchange resin was separated to obtain a titanium oxide suspension having a pH of 6.5.

Measurement of partial dissolution rate When the partial dissolution rate was measured in the same manner as in Example 1, it was 63%.

Drying treatment The obtained titanium oxide suspension was dried at 50 ° C. for 24 hours to obtain a titanium oxide powder.
Heat treatment The dried titanium oxide powder was heat-treated at 200 ° C in the air for 1 hour to prepare titanium oxide for a photocatalyst.

When the average particle size was measured in the same manner as in Example 1, the average particle size was 6.15 nm. Further, when the decomposition rate constant for the decomposition of acetaldehyde was determined in the same manner as in Example 1, it was 0.0055 / min ⁻¹ .

Comparative Example 2
In Example 2, the titanium oxide powder prepared by drying the titanium oxide suspension obtained by partial dissolution treatment was used as a photocatalyst without heat treatment, and the decomposition rate constant of acetaldehyde was set as in Example 1. It was 0.0035 / min ⁻¹ when measured.

Example 3
Partial dissolution process To 4g of titanium oxide for photocatalyst (ST-01, manufactured by Ishihara Sangyo), 10% by mass ammonia water was added so that the ammonia / titanium molar ratio was 1.25, and 30% by mass peroxide was oxidized. Add 40 ml of hydrogen water to 400 ml with water, stir it at 25 ° C. for 20 minutes, then leave it at 10 ° C. for 3 days to partially dissolve the titanium oxide powder, and add yellow oxide containing titanium oxide and peroxotitanium complex. A white mixture was obtained.
The obtained mixed liquid was centrifuged at 11,000 rpm for 20 minutes using a centrifuge (Kokusan H-2000A2), and separated into a yellowish white precipitate and a supernatant liquid to obtain a precipitate.
After adding 200 ml of a 10-fold diluted solution of 30% strength by weight hydrogen peroxide to the resulting precipitate and stirring at 25 ° C. for 1 hour, the mixture was centrifuged at 12,000 rpm for 20 minutes with a centrifuge (Hokusan H-2000A2). Centrifugation was performed to separate the precipitate and the supernatant, and the dissolved components and ammonium ions were removed.
The same removal process was repeated 5 times to obtain a titanium oxide suspension.

Measurement of partial dissolution rate When the partial dissolution rate was measured in the same manner as in Example 1, it was 29%.

Drying treatment The obtained titanium oxide suspension was heat-dried at 50 ° C. for 24 hours to obtain a titanium oxide powder.
Heat treatment The dried titanium oxide powder was heat-treated at 200 ° C in the air for 1 hour to prepare titanium oxide for a photocatalyst.

When the average particle size was measured in the same manner as in Example 1, the average particle size was 6.80 nm. Further, when the decomposition rate constant for the decomposition of acetaldehyde was determined in the same manner as in Example 1, it was 0.0054 / min ⁻¹ .

Example 4
Partial dissolution process Ammonia water is added so that the molar ratio of ammonia / titanium is 0.5 with respect to 8 g of titanium oxide for photocatalyst (Nippon Aerosil P25). In addition, water was added to make 800 ml, and this was stirred at room temperature for 4 days to partially dissolve the titanium oxide powder to obtain a yellowish white mixed liquid containing titanium dioxide and titanium-containing ions.

The obtained mixture was centrifuged with a centrifuge (Hoku2000 H2 manufactured by Kokusan) at 11,000 rpm for 20 minutes to separate it into a yellowish white precipitate and a supernatant.
Furthermore, 400 ml of a 10% strength by weight aqueous hydrochloric acid solution was added to the resulting precipitate, and the mixture was stirred at 25 ° C. for 12 hours to dissolve portions other than titanium oxide, thereby obtaining a brown mixed solution.
Next, the mixture is centrifuged at 11,000 rpm for 20 minutes using a centrifuge (Kokusan H-2000A2), separated into a precipitate and a brown supernatant, and the dissolved components contained in the supernatant are removed. A precipitate was obtained.

  Next, after adding 200 ml of purified water to the resulting precipitate and dispersing the precipitate by stirring and ultrasonic treatment, 100 ml of amphoteric ion exchange resin (Amberlite MB-1 manufactured by Organo) was gradually added and stirred. Then, ammonium ions and chlorine ions were removed, and the amphoteric ion exchange resin was separated to obtain a titanium oxide suspension having a pH of 6.5.

Measurement of partial dissolution rate When the partial dissolution rate was measured in the same manner as in Example 1, it was 28%.

Drying treatment The obtained titanium oxide suspension was dried at 50 ° C. for 24 hours to obtain a titanium oxide powder.
Heat treatment The dried titanium oxide powder was heat-treated at 200 ° C. in the air for 1 hour to prepare titanium oxide for photocatalyst.

When the average particle diameter was measured in the same manner as in Example 1, the average particle diameter was 31.5 nm. Further, when the decomposition rate constant for the decomposition of acetaldehyde was determined in the same manner as in Example 1, it was 0.0074 / min ⁻¹ .
The results are shown in FIG. 2 for explaining the relationship between the heat treatment temperature and the reaction rate constant.

Example 5
Partial dissolution process In the partial dissolution process of Example 4, except that ammonia water was added so that the molar ratio of ammonia / titanium was 1.5 to 8 g of titanium oxide for photocatalyst (P25 made by Nippon Aerosil). In the same manner as in Example 4, a titanium oxide suspension was obtained.

Measurement of partial dissolution rate When the partial dissolution rate was measured in the same manner as in Example 1, it was 76%.

Drying treatment The obtained titanium oxide suspension was dried at 50 ° C. for 24 hours to obtain a titanium oxide powder.
Heat treatment The dried titanium oxide powder was heat-treated at 200 ° C. in the air for 1 hour to prepare titanium oxide for photocatalyst.

When the average particle size was measured in the same manner as in Example 1, the average particle size was 30.4 nm. Further, when the decomposition rate constant for the decomposition of acetaldehyde was determined in the same manner as in Example 1, it was 0.0073 / min ⁻¹ .

Example 6
Partial dissolution process In the partial dissolution process of Example 4, except that ammonia water was added so that the molar ratio of ammonia / titanium was 1 with respect to 8 g of titanium oxide for photocatalyst (P25 made by Nippon Aerosil). In the same manner as in No. 4, a titanium oxide suspension was obtained.

Measurement of Partial Dissolution Rate When the partial dissolution rate was measured in the same manner as in Example 1, it was 55%.

Drying treatment The obtained titanium oxide suspension was dried at 50 ° C. for 24 hours to obtain a titanium oxide powder.
Heat treatment The dried titanium oxide powder was heat-treated in the atmosphere at 500 ° C for 1 hour to prepare titanium oxide for photocatalyst.

When the average particle diameter was measured in the same manner as in Example 1, the average particle diameter was 37.2 nm. Further, when the decomposition rate constant for the decomposition of acetaldehyde was determined in the same manner as in Example 1, it was 0.0068 / min ⁻¹ .
The results are shown in FIG. 2 for explaining the relationship between the heat treatment temperature and the reaction rate constant.

Example 7
Partial dissolution process In the partial dissolution process of Example 4, except that ammonia water was added so that the molar ratio of ammonia / titanium was 0.2 with respect to 8 g of titanium oxide for photocatalyst (P25 made by Nippon Aerosil). In the same manner as in Example 4, a titanium oxide suspension was obtained.

Measurement of partial dissolution rate When the partial dissolution rate was measured in the same manner as in Example 1, it was 10%.

Drying treatment The obtained titanium oxide suspension was dried at 50 ° C. for 24 hours to obtain a titanium oxide powder.
Heat treatment The dried titanium oxide powder was heat-treated at 200 ° C. in the air for 1 hour to prepare titanium oxide for photocatalyst.

When the average particle diameter was measured in the same manner as in Example 1, the average particle diameter was 32.0 nm. Further, when the decomposition rate constant for the decomposition of acetaldehyde was determined in the same manner as in Example 1, it was 0.0054 / min ⁻¹ .

Comparative Example 3
In the partial dissolution step described in Example 7, without separating the peroxotitanium produced by dissolution from a dispersion having a partial dissolution rate of 10%, in which ammonia water and hydrogen peroxide water were added to partially dissolve the titanium oxide particles for photocatalyst. The titanium oxide was applied on the glass plate for photocatalytic activity measurement used in Example 7 so that the amount of titanium oxide applied was 2.5 mg, and fixed by blowing hot air at 80 ° C.
Subsequently, when the decomposition rate constant for the decomposition of acetaldehyde was determined in the same manner as in Example 7, it was 0.0033 / min ⁻¹ .

Example 8
While the ammonia / titanium molar ratio is 1, heat treatment conditions are as follows: condition 1: 100 ° C. for 2 hours, condition 2: 150 ° C. for 1.5 hours, condition 3: 200 ° C. for 1 hour, and condition 4: 300 ° C. for 1 hour. Samples of four types of titanium oxide powder were prepared under the same conditions as in Example 4 except that the heat treatment was performed under the four types of conditions. The decomposition rate constant of acetaldehyde gas for each sample was as follows.
Condition 1: 100 ° C. for 2 hours 0.0069 / min ⁻¹
Condition 2: 150 ° C. 1.5 hours 0.0083 / min ⁻¹
Condition 3: 200 ° C. for 1 hour 0.0079 / min ⁻¹
Condition 4: 300 ° C. for 1 hour 0.0063 / min ⁻¹
The results are shown in FIG. 2 for explaining the relationship between the heat treatment temperature and the reaction rate constant.

Comparative Example 4
Except that the heat treatment was carried out at 600 ° C., titanium oxide for photocatalyst was prepared in the same manner as in Example 6, and the decomposition rate constant of acetaldehyde was measured and found to be 0.0029 / min ⁻¹ .
The results are shown in FIG. 2 for explaining the relationship between the heat treatment temperature and the reaction rate constant.

Comparative Example 5
Except for the point that the heat treatment was performed at 700 ° C., titanium oxide for photocatalyst was prepared in the same manner as in Example 6 and the decomposition rate constant of acetaldehyde was measured and found to be 0.0012 / min ⁻¹ .
The results are shown in FIG. 2 for explaining the relationship between the heat treatment temperature and the reaction rate constant.

Example 9
Titanium oxide in the same manner as in Example 4 except that in the partial dissolution step of Example 4, the molar ratio of ammonia / titanium was 1 with respect to 8 g of titanium dioxide for photocatalyst (P25 made by Nippon Aerosil). A powder was produced.
25 mg of the obtained titanium oxide powder was applied and dried on a 13 × 39 mm glass plate and placed in a glass reaction vessel having a capacity of 0.2 dm ³ . Next, 30 μl of normal hexane solution containing 1% by volume sarin was poured into a 500 ml sealed glass container for volatilization, and sarin-containing gas volatilized by heating was poured into the reaction container. Similar to the measurement of the reaction rate constant for the decomposition of acetaldehyde in Example 4, the reaction rate constant for the decomposition of sarin was measured. The reaction rate constant was 0.054 / min ⁻¹ .

Comparative Example 6
In place of the titanium dioxide powder used in Example 9, the decomposition rate constant of sarin was measured in the same manner as in Example 9 except that titanium dioxide for photocatalyst used as a raw material (P25 made by Nippon Aerosil) was used. 0.040 / min ⁻¹ .

Example 10
When the mustard gas decomposition rate constant was measured in the same manner as in Example 9 except that mustard gas was used instead of sarin used in Example 9, it was 0.073 / min ⁻¹ .

Example 11
The tabun decomposition rate constant was measured in the same manner as in Example 9 except that tabun was used instead of sarin used in Example 9. The result was 0.16 / min ⁻¹ .

  In the method for producing titanium oxide for photocatalyst of the present invention, after the titanium oxide particles are partially dissolved in a liquid to reduce the particle size, the components produced by the dissolution of titanium oxide and the partial dissolution process are performed. Since the titanium oxide is separated and dried after removing the ionic substances to be mixed and heat-treated in an oxygen-containing atmosphere, the photocatalytic activity is large, and it is suitable for decomposing pollutants present in the gas.

FIG. 1 is a diagram for explaining a chemical warfare agent decontamination apparatus of the present invention. FIG. 2 is a diagram for explaining the relationship between the heat treatment temperature and the reaction rate constant.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Decontamination apparatus, 2 ... Photocatalyst carrier, 3 ... Ultraviolet-permeable material member, 4 ... Reaction tube, 5 ... Ultraviolet lamp, 6 ... Contamination gas supply tube, 7 ... Decontamination gas discharge tube

Claims (6)

  A titanium oxide particle for photocatalyst, wherein the titanium oxide particles dispersed in the liquid are partially dissolved and then the titanium oxide particles having a reduced particle size are washed with water, dried and then heat-treated in an oxygen-containing atmosphere. Production method.   The method for producing titanium oxide for a photocatalyst according to claim 1, wherein the heat treatment is performed at a temperature of 100C to 500C.   3. The titanium oxide for photocatalyst according to claim 1 or 2, wherein the partial dissolution of the titanium oxide particles is performed by adding hydrogen peroxide solution and a basic substance, or adding hydrogen peroxide solution and an acidic substance. Manufacturing method.   The method for producing titanium oxide for a photocatalyst according to any one of claims 1 to 3, wherein 10% or more of the mass of the titanium oxide particles is dissolved.   The titanium oxide particles dispersed in the liquid are partially dissolved and the titanium oxide particles having a reduced particle size are washed with water, dried, and then heated at a temperature of 100 ° C. to 500 ° C. in an oxygen-containing atmosphere. A chemical warfare agent decontamination method comprising decomposing a chemical warfare agent under irradiation of ultraviolet rays with the obtained titanium oxide for photocatalyst.   The titanium oxide particles dispersed in the liquid are partially dissolved and the titanium oxide particles having a reduced particle size are washed with water, dried, and then heated at a temperature of 100 ° C. to 500 ° C. in an atmosphere containing oxygen in the particle size. Cylindrical ceramics having a three-dimensional network structure carrying titanium oxide particles obtained in this manner is disposed in a reaction chamber formed between double tubes formed of a light transmissive member, A light source that emits ultraviolet rays is arranged on the inner and outer surfaces of the heavy tube, and one end of the reaction chamber has an inlet for a pollutant gas containing a chemical warfare agent, and the other end of the reaction chamber is decontaminated. A chemical warfare agent decontamination apparatus characterized by having a gas outlet.

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