JP7454142B2 - Photocatalyst manufacturing method and photocatalyst - Google Patents

Description

The present invention relates to a method for producing a TiO2-based photocatalyst, and also relates to a photocatalyst. A photocatalyst is a catalytic substance that is excited by light absorption and causes oxidation and reduction reactions. There are "heterogeneous semiconductor photocatalysts" and "homogeneous dye photocatalysts," and in this specification, "photocatalyst" means "heterogeneous semiconductor photocatalysts." Semiconductor photocatalysts have a band structure in which a conduction band and a valence band are separated by a forbidden band. Light (electromagnetic waves) with energy greater than the band gap (forbidden band width) excites electrons in the valence band to the conduction band, generating holes in the valence band. Electrons excited to the conduction band have a stronger reducing power than electrons in the valence band, and can cause reduction reactions that cannot occur in the dark. Similarly, holes also undergo strong oxidation reactions. In the case of organic matter decomposition, the organic matter is oxidized by holes and finally completely oxidized to CO2. Electrons excited into the conduction band then reduce oxygen, eventually producing water.

TiO2 is known as an ultraviolet photocatalyst that absorbs in the ultraviolet region. In particular, anatase-type TiO2 is a metal oxide semiconductor with a band gap of 3.2 eV and exhibits high catalytic activity by absorbing ultraviolet light, but does not exhibit activity in the visible light region.

In previous research, attempts have been made to absorb visible light and activate the catalyst by doping with metals, sulfur, and nitrogen, but currently no photocatalysts with sufficient catalytic activity at a practical level in the visible light region have been reported. Not yet.

For example, it is known to introduce oxygen defects into the crystal structure of TiO2 bulk materials or thin films by irradiating them with ion beams so that they have light absorption in the visible light region. It is not easy to introduce oxygen defects into the crystal structure and control the amount of defects.

It is also known to reduce TiO2 using CaH2 or MgH2 to produce a suboxide of TiO2. Although the obtained TiO2 suboxide has a changed crystal structure, it has been confirmed that it absorbs visible light. However, the obtained TiO2 suboxide does not have photocatalytic properties. Due to this conventional technology, many researchers have not attempted to introduce oxygen vacancies into TiO2 powder using Mg in order to develop photocatalysts that have photocatalytic activity in the visible light region, or It may have been difficult to take on the challenge. In other words, the conventional technology of reducing TiO2 using CaH2 or MgH2 to produce suboxides of TiO2 is to reduce oxygen vacancies to TiO2 powder using Mg for the purpose of developing a photocatalyst that has photocatalytic activity in the visible light region. This was a factor that hindered the motivation for research and development to introduce the technology.

There has been no known method for producing a photocatalyst that is reproducible, mass-producible, and has reliable photocatalytic activity in the visible light region.

Under the above circumstances, currently, TiO2-based photocatalysts are generally used in the ultraviolet light region, and WO3/CuO-based photocatalysts are generally used in the visible light region of wavelengths from 380 to 800 nm.

International Publication No. 2011/102353 Japanese Patent Application Publication No. 2012-16679 International Publication No. 2012/111709

However, the WO3/CuO-based photocatalyst has insufficient activity to completely oxidize and decompose volatile organic compounds (VOC) in the visible light region, and since it uses W as a raw material, it is expensive and difficult to secure resources for. In this specification, "Volatile Organic Compounds (VOC)" is a general term for organic compounds that easily volatilize in the air at room temperature and pressure. The WHO classification indicates organic compounds with a boiling point of 50 to 260°C. Formaldehyde is known to be a cause of indoor air pollution in homes (sick building syndrome), and sources include plywood, wallpaper adhesives, and furniture. Acetaldehyde is the most typical VOC used when comparing photocatalytic activity as a substitute for formaldehyde, which is difficult to evaluate experimentally, and is also known as a malodorous substance in tobacco and other substances. Toluene is used as a solvent and diluent for adhesives and paints, and may be emitted from construction adhesives and paints for interior materials, etc.

As a photocatalyst, when TiO2 powder is reacted with Mg, its hydride, or a powder of a mixture thereof under vacuum at a high temperature of 350°C or higher, Mg gradually begins to oxidize, and oxygen defects are created while maintaining the crystal structure of TiO2. The present inventors have discovered that visible light absorption can be increased and the surface area can be increased by introducing

The Ellingham diagram is a widely known chart showing the ease of oxidation of metals, with the horizontal axis representing temperature and the vertical axis representing Gibbs free energy. The larger the negative value of the Gibbs free energy, the greater the bonding force with oxygen. In the Ellingham diagram, the relationship between Gibbs free energy and temperature when TiO2 is generated from Ti and O2 is represented by a straight line. By finding a straight line that represents the oxidation of metals that exist below this straight line, it is possible to theoretically find a metal that has a stronger bonding force with O than with Ti. From the Ellingham diagram, Al, Li, and Ca can be theoretically selected as metals that can introduce oxygen defects into TiO2 like Mg. Naturally, hydrogen also has a reducing power, and hydrides of Al, Li, Mg, and Ca also have a strong reducing power, and it can be theoretically inferred that oxygen defects can be introduced into the TiO2 powder.

In addition, the present inventor has found that by supporting metals such as Fe and Cu or metal oxides thereof on the surface of the photocatalyst, the visible light absorption rate can be further increased without hindering the visible light absorption due to the introduction of oxygen defects. In addition, we discovered that the synergistic effect can enhance photocatalytic activity and improve photocatalytic efficiency.

The inventors have found that when the heat treatment temperature exceeds 550°C, the crystal structure of TiO2 changes from anatase type to rutile type. Based on these findings, we have arrived at a method for producing a photocatalyst and a photocatalyst in which oxygen defects are introduced while maintaining the crystal structure of TiO2 powder and metal is supported according to the present invention.

The method for producing a photocatalyst according to the first aspect of the present invention, as described in claim 1, comprises TiO2 powder and 0.1 to 5 wt% of Al, Li, Mg, Ca, or their hydrides based on TiO2. A first mixed powder obtained by uniformly mixing the powder of the mixture and powder of Fe or Cu, its oxide, or a mixture thereof in an amount of 0.1 to 5 wt% based on TiO2 is stored in a crucible, and the The crucible is placed in a vacuum heating furnace, evacuated, and then heat treated in vacuum at a temperature of 350 to 550° C. to produce a photocatalyst.

The method for producing a photocatalyst according to the second aspect of the present invention, as set forth in claim 2, dissolves 0.1 to 5 wt% of Fe or Cu, its oxide, or a mixture thereof based on TiO2 in hydrochloric acid or nitric acid. The solution was mixed with an aqueous suspension of TiO2 powder, and the mixed dry powder obtained by mixing the solution with an aqueous suspension of TiO2 was mixed with 0.1 to 5 wt% of Al, Li, Mg, or Ca based on TiO2. , the hydride or a mixture thereof to obtain a second mixed powder, the second mixed powder is stored in a crucible, the crucible is placed in a vacuum heating furnace, and the second mixed powder is placed in a vacuum heating furnace. After evacuation, heat treatment is performed at a temperature of 350 to 550° C. in a vacuum to produce a photocatalyst.

In a preferred embodiment of the method for producing a photocatalyst according to the first or second aspect of the present invention, TiO2 is of anatase type, rutile type, brookite type, or a mixture thereof.

As described in claim 4, the third invention provides a TiO2 powder, a powder of Al, Li, Mg or Ca, a hydride thereof, or a mixture thereof in an amount of 0.1 to 5 wt% with respect to TiO2, and TiO2. A first mixed powder obtained by uniformly mixing 0.1 to 5 wt% of Fe or Cu, an oxide thereof, or a powder of a mixture thereof is placed in a crucible, and the crucible is placed in a vacuum heating furnace. After being evacuated, heat treatment is performed at a temperature of 350 to 550°C in a vacuum to introduce oxygen defects while maintaining the crystal structure of the TiO2 powder, and to add Fe or Cu to the surface of the TiO2 powder, as well as its oxidation. or a mixture thereof.

The fourth aspect of the present invention is to obtain a solution by dissolving 0.1 to 5 wt% of Fe or Cu, its oxide, or a mixture thereof based on TiO2 with hydrochloric acid or nitric acid. , a mixed dry powder obtained by mixing the solution and an aqueous suspension of TiO2 powder and drying the mixture, and 0.1 to 5 wt% of Al, Li, Mg or Ca, their hydrides, or their hydrides based on TiO2. A second mixed powder is obtained by uniformly mixing the powder of the mixture of The TiO2 powder is heat-treated at a temperature of 350 to 550°C to introduce oxygen defects while maintaining the crystal structure of the TiO2 powder, and to support Fe or Cu, its oxide, or a mixture thereof on the surface of the TiO2 powder.

(1) In the method for producing a photocatalyst of the present invention, a solid phase-solid phase reaction is used to prepare TiO2 powder using a powder of a reducing metal (Al, Li, Mg, or Ca), its hydride, or a mixture thereof. Oxygen defects are introduced while maintaining the crystal structure. XRD analysis of the obtained powder confirmed that the crystal structure of TiO2 was maintained.

By introducing oxygen defects while maintaining the crystal structure of this TiO2 powder, an oxygen defect level is formed in the middle of the bandgap (forbidden band width) of TiO2, as shown in Fig. 13, so that it can be irradiated with visible light. oxidation/reduction reactions occur more easily, the absorption of visible light increases and the surface area of the TiO2 crystal increases.

(2) In the method for producing a photocatalyst of the present invention, a metal such as Fe or Cu or a metal oxide thereof is supported on the surface of TiO2. As shown in FIG. 14, supporting metals such as Fe or Cu or their metal oxides on the surface of TiO2 further increases the visible light absorption rate without hindering visible light absorption due to the introduction of oxygen defects, and also increases electron conductivity. Coupled with the imparting properties and the charge accumulation effect, this increases the photocatalytic activity of TiO2 crystals in visible light and improves the photocatalytic efficiency.

It is a schematic diagram of the manufacturing equipment used. FIG. 2 is a schematic diagram of a temperature-time graph carried out in the heat treatment for producing photocatalyst particles in this example. FIG. 2 is an X-ray diffraction pattern diagram of anatase-type TiO2 raw material powder. It is an X-ray diffraction pattern diagram of the obtained sample powder. FIG. 2 is an X-ray diffraction pattern diagram of the obtained sample powder. FIG. 2 is a schematic diagram showing the arrangement of spectral reflectance (diffuse+specular reflectance) measurement. It is a graph showing the measurement results of the light absorption spectrum of the obtained sample powder. It is a graph which shows the measurement result of the optical absorption spectrum of the obtained sample powder. 1 is a schematic diagram of an apparatus used in a VOC decomposition evaluation test. It is a graph showing the VOC decomposition evaluation results of the obtained sample powder. It is a graph showing the VOC decomposition evaluation results of the obtained sample powder. It is a graph showing the VOC decomposition evaluation results of the obtained sample powder. FIG. 2 is a schematic diagram showing the energy potential (energy level) when oxygen defects are introduced into TiO2 and metal is supported. It is a graph showing the light absorption spectra of oxygen defect-introduced+CuO-supported TiO2, oxygen defect-introduced TiO2, and TiO2.

Embodiments of the present invention will be described below with reference to the accompanying drawings.

(A) Example of a photocatalyst powder in which oxygen defects are introduced into TiO2 by the reduced metal Mg An example of producing a photocatalyst TiO2 powder in which oxygen defects are introduced from TiO2 powder and Mg powder by solid phase-solid phase reaction will be explained. .

<Example 1>
Preparation of Sample Powder The TiO2 raw material powder is anatase type manufactured by Ishihara Sangyo Co., Ltd., and has a purity of 85% or more and a primary particle size of 7 nm.

The Mg raw material powder is manufactured by Kanto Metals, has a purity of 99.5% or more, and has an average particle diameter D50 of 100 μm.

80.0 g of TiO2 raw powder and 1.6 g of Mg raw powder were weighed into a container and shaken, resulting in a raw mixed powder in which TiO2 raw powder and Mg raw powder were uniformly mixed.

FIG. 1 is a schematic diagram of the manufacturing apparatus used to prepare the sample powder. The graphite crucible 1 has an inner diameter of 70 mm and a height of 125 mm, and a gas vent hole 11 is provided in the center of the upper surface. After the raw material mixed powder 2 was placed in a graphite crucible 1, it was placed horizontally in a vacuum heating furnace 3 equipped with a high-frequency heating device 4.

Then, the inside of the vacuum heating furnace 3 was evacuated to 8 Pa using the vacuum pump 6 through the pipe 5 while being careful not to scatter the raw material mixed powder 2.

Immediately after evacuation to 8 Pa, as shown in the heat treatment pattern shown in Figure 2, the temperature was raised from room temperature (Tr) to 550°C (Tmax) over 1 hour (0 to t1), and then at 550°C (Tmax) for 3 hours. The temperature was maintained for (t1 to t2), and then the heating power source was turned off to allow natural cooling. Vacuum evacuation was continued using the vacuum pump 6 during temperature raising, holding, and cooling.

After sufficiently cooling, the vacuum pump 6 was stopped and the pressure returned to atmospheric pressure, and the graphite crucible 1 was taken out to obtain a sample powder.

When the obtained sample powder was visually observed, it was found that the original white powder had turned dark brown and was a uniform fine powder.

<Example 1-2>
The other conditions except for the heat treatment pattern were exactly the same as those in Example 1, and immediately after evacuation to 8 Pa, the temperature was raised from room temperature (Tr) to 350°C (Tmax) over 1 hour (0-t1), and the sample was held at 350°C (Tmax) for 3 hours (t1-t2), as shown in the heat treatment pattern in Figure 2, after which the heating power source was turned off and the sample was allowed to cool naturally. Evacuation was continued using the vacuum pump 6 during the heating, holding, and cooling periods.

After sufficiently cooling, the vacuum pump 6 was stopped and the pressure returned to atmospheric pressure, and the graphite crucible 1 was taken out to obtain a sample powder.

When the obtained sample powder was visually observed, the original white powder was slightly yellowish, but it was found to be a uniform fine powder.

<Example 1-3>
The other conditions except for the heat treatment pattern were exactly the same as those in Example 1, and immediately after evacuation to 8 Pa, the temperature was raised from room temperature (Tr) to 600°C (Tmax) over 1 hour (0-t1), and the sample was held at 600°C (Tmax) for 3 hours (t1-t2), after which the heating power source was turned off and the sample was allowed to cool naturally, as shown in the heat treatment pattern shown in Figure 2. Evacuation was continued using the vacuum pump 6 during the heating, holding, and cooling periods.

After sufficiently cooling, the vacuum pump 6 was stopped and the pressure returned to atmospheric pressure, and the graphite crucible 1 was taken out to obtain a sample powder.

Visual observation of the obtained sample powder revealed that the original white powder had turned black and was a uniform fine powder.

From the above Examples 1, 1-2, and 1-3, the oxidation-reduction reaction by Mg starts to occur in TiO2 powder at a heat treatment temperature of about 350°C, and as the heat treatment temperature increases, TiO2 crystallizes. It was discovered that when the temperature exceeds about 550°C, the crystal structure changes from anatase type to rutile type.

(B) Example of photocatalyst powder in which oxygen defects are introduced into TiO2 by reduced metal Mg and Fe is supported using powdered Fe. Oxygen defects are generated from TiO2 powder, Mg powder, and Fe powder by solid phase-solid phase reaction. An example will be described in which a photocatalytic TiO2 powder is introduced and Fe-supported is produced.

<Example 2>
Preparation of Sample Powder The TiO2 raw material powder is anatase type manufactured by Ishihara Sangyo Co., Ltd., and has a purity of 85% or more and a primary particle size of 7 nm.

The Mg raw material powder is manufactured by Kanto Metals, has a purity of 99.5% or more, and has an average particle diameter D50 of 100 μm.

The Fe raw material powder was manufactured by Jiangsu Tianyi Ultra Metal Powder Co. , Ltd. The purity is 98% or more, and the average particle diameter D50 is 1 μm.

When 80.0 g of TiO2 raw powder, 0.8 g of Mg raw powder, and 0.8 g of Fe raw powder were weighed into a container and shaken, the TiO2 raw powder, Mg raw powder, and Fe raw powder were mixed uniformly. A raw material mixed powder was obtained.

FIG. 1 is a schematic diagram of the manufacturing apparatus used to prepare the sample powder. The graphite crucible 1 has an inner diameter of 70 mm and a height of 125 mm, and a gas vent hole 11 is provided in the center of the upper surface. After the raw material mixed powder 2 was placed in a graphite crucible 1, it was placed horizontally in a vacuum heating furnace 3 equipped with a high-frequency heating device 4.

Then, the inside of the vacuum heating furnace 3 was evacuated to 8 Pa using the vacuum pump 6 through the pipe 5 while being careful not to scatter the raw material mixed powder 2.

Immediately after evacuation to 8 Pa, as shown in the heat treatment pattern shown in Figure 2, the temperature was raised from room temperature (Tr) to 500°C (Tmax) over 1 hour (0 to t1), and then at 500°C (Tmax) for 3 hours. The temperature was maintained for (t1 to t2), and then the heating power source was turned off to allow natural cooling. Vacuum evacuation was continued using the vacuum pump 6 during temperature raising, holding, and cooling.

After sufficiently cooling, the vacuum pump 6 was stopped to return to atmospheric pressure, and the graphite crucible 1 was taken out to obtain a sample powder.

When the obtained sample powder was visually observed, it was found to be a uniform fine powder with a slightly grayish color.

<Example 2-2>
Preparation of Sample Powder The TiO2 raw material powder is anatase type manufactured by Ishihara Sangyo Co., Ltd., and has a purity of 85% or more and a primary particle size of 7 nm.

The MgH2 raw material powder is manufactured by BioCoke, has a purity of 98% or more, and has an average particle diameter D50 of 60 μm.

The Fe raw material powder was manufactured by Jiangsu Tianyi Ultra Metal Powder Co. , Ltd. The purity is 98% or more, and the average particle diameter D50 is 1 μm.

When 100.0 g of TiO2 raw material powder, 1.1 g of MgH2 raw material powder, and 1.0 g of Fe raw material powder were weighed into a container and shaken, the TiO2 raw material powder, MgH2 raw material powder, and Fe raw material powder were mixed uniformly. A raw material mixed powder was obtained.

FIG. 1 is a schematic diagram of the manufacturing apparatus used to prepare the sample powder. The graphite crucible 1 has an inner diameter of 70 mm and a height of 125 mm, and a gas vent hole 11 is provided in the center of the upper surface. After the raw material mixed powder 2 was placed in a graphite crucible 1, it was placed horizontally in a vacuum heating furnace 3 equipped with a high-frequency heating device 4.

Then, the inside of the vacuum heating furnace 3 was evacuated to 8 Pa using the vacuum pump 6 through the pipe 5 while being careful not to scatter the raw material mixed powder 2.

Immediately after evacuation to 8 Pa, as shown in the heat treatment pattern shown in Figure 2, the temperature was raised from room temperature (Tr) to 500°C (Tmax) over 1 hour (0 to t1), and then at 500°C (Tmax) for 3 hours. The temperature was maintained for (t1 to t2), and then the heating power source was turned off to allow natural cooling. Vacuum evacuation was continued using the vacuum pump 6 during temperature raising, holding, and cooling. A large pressure increase was observed when the temperature was increased, which is thought to be due to gas generation due to oxidative decomposition of MgH2.

After sufficient cooling, the vacuum pump 6 was stopped and the pressure was returned to atmospheric pressure, the graphite crucible 1 was removed, and the sample powder was obtained.

When the obtained sample powder was visually observed, it was found to be a uniform fine powder with a slightly grayish white color.

(C) Example of a photocatalyst powder in which oxygen defects are introduced into TiO2 by reduced metal Mg and Cu is supported using powdered Cu. Oxygen defects are generated from TiO2 powder, Mg powder, and Cu powder by solid phase-solid phase reaction. An example of manufacturing a photocatalytic TiO2 powder in which Cu is introduced and Cu is supported will be described.

<Example 3>
Preparation of Sample Powder The TiO2 raw material powder is anatase type manufactured by Ishihara Sangyo Co., Ltd., and has a purity of 85% or more and a primary particle size of 7 nm.

The Mg raw material powder is manufactured by Kanto Metals, has a purity of 99.5% or more, and has an average particle diameter D50 of 100 μm.

The Cu raw material powder is manufactured by Kojundo Kagaku Co., Ltd., has a purity of 99.5% or more, and has an average particle diameter D50 of 5 μm.

When 80.0 g of TiO2 raw powder, 0.8 g of Mg raw powder, and 0.8 g of Cu raw powder were weighed into a container and shaken, the TiO2 raw powder, Mg raw powder, and Cu raw powder were mixed uniformly. A raw material mixed powder was obtained.

FIG. 1 is a schematic diagram of the manufacturing apparatus used to prepare the sample powder. The graphite crucible 1 has an inner diameter of 70 mm and a height of 125 mm, and a gas vent hole 11 is provided in the center of the upper surface. After the raw material mixed powder 2 was placed in a graphite crucible 1, it was placed horizontally in a vacuum heating furnace 3 equipped with a high-frequency heating device 4.

Then, the inside of the vacuum heating furnace 3 was evacuated to 8 Pa using the vacuum pump 6 through the pipe 5 while being careful not to scatter the raw material mixed powder 2.

Immediately after evacuation to 8 Pa, as shown in the heat treatment pattern shown in Figure 2, the temperature was raised from room temperature (Tr) to 500°C (Tmax) over 1 hour (0 to t1), and then at 500°C (Tmax) for 3 hours. The temperature was maintained for (t1 to t2), and then the heating power source was turned off to allow natural cooling. Vacuum evacuation was continued using the vacuum pump 6 during temperature raising, holding, and cooling.

After sufficiently cooling, the vacuum pump 6 was stopped and the pressure returned to atmospheric pressure, and the graphite crucible 1 was taken out to obtain a sample powder.

When the obtained sample powder was visually observed, it was found to be a uniform fine powder with a slightly gray color overall.

<Example 3-4>
Weigh 80.0 g of TiO2 raw powder, 0.4 g of Mg raw powder, and 0.4 g of Cu raw powder as sample powders in a container, and shake them to make the TiO2 raw powder, Mg raw powder, and Cu raw powder uniform. The test was conducted under exactly the same conditions as in Example 3 except that the mixed raw material powder was used.

When the obtained sample powder was visually observed, it was found to be a uniform fine powder with a slightly brownish color overall.

<Example 3-6>
Weigh out 80.0 g of TiO2 raw powder, 0.4 g of Mg raw powder, and 3.2 g of Cu raw powder as sample powders in a container, and shake them to make the TiO2 raw powder, Mg raw powder, and Cu raw powder uniform. The test was conducted under exactly the same conditions as in Example 3 except that the mixed raw material powder was used.

When the obtained sample powder was visually observed, it was found to be a uniform fine powder with a slightly brownish color overall.

<Example 3-7>
As sample powders, 80.0 g of TiO2 raw powder, 3.2 g of Mg raw powder, and 0.8 g of Cu raw powder were weighed into a container and shaken, so that the TiO2 raw powder, Mg raw powder, and Cu raw powder were uniformly mixed. The test was conducted under exactly the same conditions as in Example 3, except that the same raw material mixed powder was used.

When the obtained sample powder was visually observed, it was found to be a uniform fine powder with a slightly brownish color overall.

(D) Example of photocatalyst powder in which oxygen defects are introduced into TiO2 by reduced metal Mg after iron oxide is supported on TiO2 powder with iron nitrate solution After iron oxide is supported on TiO2 powder with iron nitrate solution, An example will be described in which an iron oxide-supported photocatalytic TiO2 powder having oxygen vacancies introduced therein is produced from TiO2 powder supporting iron oxide and Mg powder by a phase-solid phase reaction.

<Example 4>
Preparation of Sample Powder The TiO2 raw material powder is anatase type manufactured by Ishihara Sangyo Co., Ltd., and has a purity of 85% or more and a primary particle size of 7 nm.

The Mg raw material powder is manufactured by Kanto Metals, has a purity of 99.5% or more, and has an average particle diameter D50 of 100 μm.

First, an iron nitrate solution was prepared by dissolving 0.8 g of Fe as a supported metal in a 25-30% nitric acid solution, and an aqueous suspension in which 80.0 g of TiO2 raw material powder was suspended in water was mixed with the iron nitrate solution. Mix and stir. Next, when the mixed dry powder obtained by drying this mixed solution at a temperature of 170°C or higher and 0.8 g of Mg raw powder were weighed into a container and shaken, the mixed dry powder and Mg raw powder were uniformly mixed. A mixed second raw material mixed powder was obtained.

FIG. 1 is a schematic diagram of the manufacturing apparatus used to prepare the sample powder. The graphite crucible 1 has an inner diameter of 70 mm and a height of 125 mm, and a gas vent hole 11 is provided in the center of the upper surface. After the second raw material mixed powder 2 was placed in a graphite crucible 1, it was placed horizontally in a vacuum heating furnace 3 equipped with a high frequency heating device 4.

Then, the inside of the vacuum heating furnace 3 was evacuated to 8 Pa using the vacuum pump 6 through the piping 5 while being careful not to scatter the second raw material mixed powder 2.

Immediately after evacuation to 8 Pa, as shown in the heat treatment pattern shown in Figure 2, the temperature was raised from room temperature (Tr) to 500°C (Tmax) over 1 hour (0 to t1), and then at 500°C (Tmax) for 3 hours. The temperature was maintained for (t1 to t2), and then the heating power source was turned off to allow natural cooling. Vacuum evacuation was continued using the vacuum pump 6 during temperature raising, holding, and cooling.

After sufficiently cooling, the vacuum pump 6 was stopped and the pressure returned to atmospheric pressure, and the graphite crucible 1 was taken out to obtain a sample powder.

When the obtained sample powder was visually observed, it was found to be a uniform fine powder with a pale yellow-green color.

(E) Example of a photocatalyst powder in which copper oxide is supported on TiO2 powder with copper nitrate solution, and then oxygen defects are introduced into TiO2 with reduced metal Mg After supporting copper oxide on TiO2 powder with copper nitrate solution, solid phase - An example will be described in which a copper oxide-supported photocatalyst TiO2 powder having oxygen vacancies introduced therein is produced from TiO2 powder supporting copper oxide and Mg powder by solid-phase reaction.

<Example 5>
Preparation of Sample Powder The TiO2 raw material powder is anatase type manufactured by Ishihara Sangyo Co., Ltd., and has a purity of 85% or more and a primary particle size of 7 nm.

The Mg raw material powder is manufactured by Kanto Metals, has a purity of 99.5% or more, and has an average particle diameter D50 of 100 μm.

First, a copper nitrate solution was prepared by dissolving 0.8 g of Cu, which is a supported metal, in a 25-30% nitric acid solution, and an aqueous suspension in which 80.0 g of TiO2 raw material powder was suspended in water was mixed with the copper nitrate solution. Mix and stir. Next, when the mixed dry powder obtained by drying this mixed solution at a temperature of 170°C or higher and 0.8 g of Mg raw powder were weighed into a container and shaken, the mixed dry powder and Mg raw powder were uniformly mixed. A mixed second raw material mixed powder was obtained.

FIG. 1 is a schematic diagram of the manufacturing apparatus used to prepare the sample powder. The graphite crucible 1 has an inner diameter of 70 mm and a height of 125 mm, and a gas vent hole 11 is provided in the center of the upper surface. After the second raw material mixed powder 2 was placed in a graphite crucible 1, it was placed horizontally in a vacuum heating furnace 3 equipped with a high frequency heating device 4.

Then, the inside of the vacuum heating furnace 3 was evacuated to 8 Pa using the vacuum pump 6 through the piping 5 while being careful not to scatter the second raw material mixed powder 2.

Immediately after evacuation to 8 Pa, as shown in the heat treatment pattern shown in Figure 2, the temperature was raised from room temperature (Tr) to 500°C (Tmax) over 1 hour (0 to t1), and then at 500°C (Tmax) for 3 hours. The temperature was maintained for (t1 to t2), and then the heating power source was turned off to allow natural cooling. Vacuum evacuation was continued using the vacuum pump 6 during temperature raising, holding, and cooling.

After sufficiently cooling, the vacuum pump 6 was stopped and the pressure returned to atmospheric pressure, and the graphite crucible 1 was taken out to obtain a sample powder.

When the obtained sample powder was visually observed, it was found to be a uniform fine powder with a slightly brownish color.

<Example 5-7>
The test was conducted under exactly the same conditions as in Example 5, except that the proportions of Cu and Mg in the second raw material mixed powder were changed.

A copper nitrate solution was prepared by dissolving 0.08 g of Cu, which is a supported metal, in a 25-30% nitric acid solution, and a water suspension in which 80.0 g of TiO2 raw material powder was suspended in water was mixed with the copper nitrate solution. and stir. Next, when the mixed dry powder obtained by drying this mixed solution at a temperature of 170°C or higher and 0.4 g of Mg raw powder were weighed into a container and shaken, the mixed dry powder and Mg raw powder were uniformly mixed. A mixed second raw material mixed powder was obtained.

After heating, holding, and cooling in a vacuum using the same heat treatment pattern as in Example 5, the sample powder was returned to atmospheric pressure and taken out. Visual observation of the obtained sample powder revealed that it was a uniform fine powder with a slight brownish color. there were.

<Example 5-11>
The test was conducted under exactly the same conditions as in Example 5, except that the proportions of Cu and Mg in the second raw material mixed powder were changed.

A copper nitrate solution was prepared by dissolving 3.2 g of Cu as a supporting metal in a 25 to 30% nitric acid solution, and a water suspension in which 80.0 g of TiO2 raw material powder was suspended in water was mixed with the copper nitrate solution. and stir. Next, when the mixed dry powder obtained by drying this mixed solution at a temperature of 170°C or higher and 0.8 g of Mg raw powder were weighed into a container and shaken, the mixed dry powder and Mg raw powder were uniformly mixed. A mixed second raw material mixed powder was obtained.

After heating, holding, and cooling in a vacuum using the same heat treatment pattern as in Example 5, the sample powder was returned to atmospheric pressure and taken out. Visual observation of the obtained sample powder revealed that it was a uniform fine powder with a slight brownish color. there were.

<Example 5-12>
The test was conducted under exactly the same conditions as in Example 5, except that the proportions of Cu and Mg in the second raw material mixed powder were changed.

A copper nitrate solution was prepared by dissolving 0.24 g of Cu, which is a supported metal, in a 25-30% nitric acid solution, and a water suspension in which 80.0 g of TiO2 raw material powder was suspended in water was mixed with the copper nitrate solution. and stir. Next, when the mixed dry powder obtained by drying this mixed solution at a temperature of 170°C or higher and 3.2 g of Mg raw powder were weighed into a container and shaken, the mixed dry powder and Mg raw powder were uniformly mixed. A mixed second raw material mixed powder was obtained.

After heating, holding, and cooling in a vacuum using the same heat treatment pattern as in Example 5, the sample powder was returned to atmospheric pressure and taken out. Visual observation of the obtained sample powder revealed that it was a uniform fine powder with a slight brownish color. there were.

(F) Example of photocatalyst powder with different crystal structure of TiO2 <Example 6>
Preparation of Sample Powder The TiO2 raw material powder is a mixed powder of 87% anatase type and 13% rutile type manufactured by Nippon Aerosil Co., Ltd., the purity is 99% or more, and the primary particle size is 20 nm.

The Mg raw material powder is manufactured by Kanto Metals, has a purity of 99.5% or more, and has an average particle diameter D50 of 100 μm.

First, a copper nitrate solution was prepared by dissolving 0.8 g of Cu, which is a supported metal, in a 25-30% nitric acid solution, and an aqueous suspension in which 80.0 g of TiO2 raw material powder was suspended in water was mixed with the copper nitrate solution. Mix and stir. Next, when the mixed dry powder obtained by drying this mixed solution at a temperature of 170°C or higher and 0.8 g of Mg raw powder were weighed into a container and shaken, the mixed dry powder and Mg raw powder were uniformly mixed. A mixed second raw material mixed powder was obtained.

FIG. 1 is a schematic diagram of the manufacturing apparatus used to prepare the sample powder. The graphite crucible 1 has an inner diameter of 70 mm and a height of 125 mm, and a gas vent hole 11 is provided in the center of the upper surface. After the raw material powder 2 was placed in a graphite crucible 1, it was placed horizontally in a vacuum heating furnace 3 equipped with a high frequency heating device 4.

Then, the inside of the vacuum heating furnace 3 was evacuated to 8 Pa using the vacuum pump 6 through the piping 5 while being careful not to scatter the raw material powder 2.

Immediately after evacuation to 8 Pa, as shown in the heat treatment pattern shown in Figure 2, the temperature was raised from room temperature (Tr) to 450°C (Tmax) over 1 hour (0 to t1), and then at 450°C (Tmax) for 3 hours. The temperature was maintained for (t1 to t2), and then the heating power source was turned off to allow natural cooling. Vacuum evacuation was continued using the vacuum pump 6 during temperature raising, holding, and cooling.

After sufficiently cooling, the vacuum pump 6 was stopped and the pressure returned to atmospheric pressure, and the graphite crucible 1 was taken out to obtain a sample powder.

When the obtained sample powder was visually observed, it was found to be a pale yellow uniform fine powder.

<Example 6-2>
Preparation of Sample Powder The TiO2 raw material powder is a rutile type manufactured by Kojundo Chemical Co., Ltd., and has a purity of 99% or more and a primary particle size of 500 nm.

First, a copper nitrate solution was prepared by dissolving 0.8 g of Cu, which is a supported metal, in a 25-30% nitric acid solution, and an aqueous suspension in which 80.0 g of TiO2 raw material powder was suspended in water was mixed with the copper nitrate solution. Mix and stir. Next, when the mixed dry powder obtained by drying this mixed solution at a temperature of 170°C or higher and 0.8 g of Mg raw powder were weighed into a container and shaken, the mixed dry powder and Mg raw powder were uniformly mixed. A mixed second raw material mixed powder was obtained.

FIG. 1 is a schematic diagram of the manufacturing apparatus used to prepare the sample powder. The graphite crucible 1 has an inner diameter of 70 mm and a height of 125 mm, and a gas vent hole 11 is provided in the center of the upper surface. After the raw material powder 2 was placed in a graphite crucible 1, it was placed horizontally in a vacuum heating furnace 3 equipped with a high frequency heating device 4.

Then, the inside of the vacuum heating furnace 3 was evacuated to 8 Pa using the vacuum pump 6 through the pipe 5 while being careful not to scatter the raw material powder 2.

Immediately after evacuation to 8 Pa, as shown in the heat treatment pattern shown in Figure 2, the temperature was raised from room temperature (Tr) to 500°C (Tmax) over 1 hour (0 to t1), and then at 500°C (Tmax) for 3 hours. The temperature was maintained for (t1 to t2), and then the heating power source was turned off to allow natural cooling. Vacuum evacuation was continued using the vacuum pump 6 during temperature raising, holding, and cooling.

After sufficiently cooling, the vacuum pump 6 was stopped and the pressure returned to atmospheric pressure, and the graphite crucible 1 was taken out to obtain a sample powder.

When the obtained sample powder was visually observed, it was found to be a uniform fine powder with a light ocher color.

<Example 6-3>
Preparation of Sample Powder The TiO2 raw material powder is a brookite type manufactured by Kojundo Kagaku Co., Ltd., and has a purity of 99% or more and a primary particle size of 30 nm.

First, a copper nitrate solution was prepared by dissolving 0.8 g of Cu, which is a supported metal, in a 25-30% nitric acid solution, and an aqueous suspension in which 80.0 g of TiO2 raw material powder was suspended in water was mixed with the copper nitrate solution. Mix and stir. Next, when the mixed dry powder obtained by drying this mixed solution at a temperature of 170°C or higher and 0.8 g of Mg raw powder were weighed into a container and shaken, the mixed dry powder and Mg raw powder were uniformly mixed. A mixed second raw material mixed powder was obtained.

FIG. 1 is a schematic diagram of the manufacturing apparatus used to prepare the sample powder. The graphite crucible 1 has an inner diameter of 70 mm and a height of 125 mm, and a gas vent hole 11 is provided in the center of the upper surface. After the raw material powder 2 was placed in a graphite crucible 1, it was placed horizontally in a vacuum heating furnace 3 equipped with a high frequency heating device 4.

Then, the inside of the vacuum heating furnace 3 was evacuated to 8 Pa using the vacuum pump 6 through the pipe 5 while being careful not to scatter the raw material powder 2.

Immediately after evacuation to 8 Pa, as shown in the heat treatment pattern shown in Figure 2, the temperature was raised from room temperature (Tr) to 500°C (Tmax) over 1 hour (0 to t1), and then at 500°C (Tmax) for 3 hours. The temperature was maintained for (t1 to t2), and then the heating power source was turned off to allow natural cooling. Vacuum evacuation was continued using the vacuum pump 6 during temperature raising, holding, and cooling.

After sufficiently cooling, the vacuum pump 6 was stopped and the pressure returned to atmospheric pressure, and the graphite crucible 1 was taken out to obtain a sample powder.

When the obtained sample powder was visually observed, it was found to be a uniform white fine powder with almost no coloration.

(G) Comparative examples of other photocatalyst powders

<Comparative example>
A commercially available anatase type photocatalyst was obtained as a comparative example.

A commercially available anatase photocatalyst is ST-01 (trade name) manufactured by Ishihara Sangyo Co., Ltd., and has a purity of 87% and a primary particle size of 7 nm.

(H) Measurement of Final Sample Powder The obtained final sample powder was subjected to X-ray diffraction analysis using an X-ray diffractometer RINT 2200VK/PC manufactured by Rigaku. The measurement results are shown in Figures 3 to 5. In FIGS. 3 to 5, the curves are the X-ray diffraction profiles of the final sample powders and are displayed along with the standard peak pattern of anatase TiO2. FIG. 3 shows the X-ray diffraction profile of the anatase-type TiO2 raw material powder. FIG. 4 shows the X-ray diffraction profile of the final sample powder obtained in Example 1. As can be seen from the X-ray diffraction profile in FIG. 4, the final sample powder of Example 1, in which the heat treatment temperature was 550°, retains the original anatase crystal structure.

On the other hand, FIG. 5 shows the X-ray diffraction profile of the final sample powder obtained when heat treated at 600° C. (Tmax) for 3 hours. It can be seen from FIG. 5 that when the heat treatment temperature reaches 600° C., the anatase crystal structure collapses and changes to a rutile crystal. In addition, in Example 1-2 where the heat treatment temperature was 350°C, when the heat treatment temperature approached 300°C, there was a change in which the temperature and pressure inside the furnace temporarily increased. A reaction occurs and oxygen defects begin to be introduced into the crystal structure of TiO2, but at temperatures below 300°C, no rapid changes are observed in the temperature and pressure inside the furnace, and the reduction reaction of TiO2 by Mg, which is a reducing metal, does not occur. In this way, the crystal structure of the final sample powder maintains the crystal structure of TiO2, which is the raw material powder, at a heat treatment temperature of 350°C to 550°C, and at the same time as crystallization progresses, the reduction action of TiO2 by the reducing metal and material diffusion occur. It is thought that this is occurring.

Characteristic Test of Photocatalyst Powder Next, a characteristic test of the photocatalyst powder of Examples 1 to 6-3 and the photocatalyst powder of Comparative Example will be explained.

(I) Measurement Results of Light Absorption Spectrum A sample for spectral reflectance measurement was prepared by molding the sample powder into a flat plate with a thickness that did not transmit light.

The spectral reflectance (diffuse+specular reflectance) was measured using SolidSpec-3700DUV (manufactured by Shimadzu Corporation, double beam type).

FIG. 6 is a schematic diagram showing the arrangement for measuring spectral reflectance (diffuse+specular reflectance). An integrating sphere is placed so as to surround the measurement part of the sample for spectral reflectance measurement. The light entrance is provided in a part of the integrating sphere that is inclined by 8 degrees from the vertical direction. Light of a specific wavelength from a spectroscope (not shown) passes through the light inlet and enters the measurement portion of the sample for spectral reflectance measurement. Then, the reflected light is measured to measure the spectral reflectance (diffuse+specular reflectance) of the sample.

The measurement results of the optical absorption spectrum in the range from 250 to 700 nm are shown in FIGS. 7 and 8 together with comparative examples.

FIG. 7 shows the measurement results of the light absorption spectra of the sample powders obtained in Example 1, Example 2, Example 2-2, Example 3, Example 4, Example 5, and Comparative Example. There is. FIG. 8 shows the measurement results of the light absorption spectra of the sample powders obtained in Example 5, Example 6, Example 6-2, Example 6-3, and Comparative Example. For wavelengths of 350 nm or less (ultraviolet light region), Example 1, Example 2, Example 2-2, Example 3, Example 4, Example 5, Example 6, Example 6-2, Example 6 The absorption rates of -3 and Comparative Example are about 90 to 95%, which are almost the same. At wavelengths of 400 to 700 nm (visible light region), the absorption rate of Example 1 is 48 to 18%, the absorption rate of Example 2 is 62 to 59%, and the absorption rate of Example 2-2 is The absorption rate of Example 3 is 30-28%, the absorption rate of Example 4 is 76-24%, the absorption rate of Example 5 is 67-42%, and the absorption rate of Example 3 is 30-28%, and the absorption rate of Example 5 is 67-42%. The absorption rate of Example 6 is 62-45%, the absorption rate of Example 6-2 is 67-35%, the absorption rate of Example 6-3 is 57-47%, and the absorption rate of Comparative Example is 62-45%. is 28-5%. It can be seen that all of the photocatalysts of Examples 1 to 6-3 have much better absorption rates in the visible light region than the comparative examples.

The photocatalysts of Example 2 and Example 2-2 have particularly excellent absorption rates in the visible light region compared to the photocatalysts of comparative examples, and in the ultraviolet to visible light region (250 to 700 nm), reducing metals are used as reducing agents. Even if (Mg) or its hydride (MgH2) is used, its light absorption spectrum is almost the same, and it is predicted that the photocatalytic properties are also almost the same. Furthermore, the photocatalysts of Example 5, Example 6, Example 6-2, and Example 6-3 have better absorption rates in the visible light region than the photocatalysts of the comparative examples, and have anatase type, rutile type, It can be seen that the present invention can increase the light absorption rate in the visible light region more than commercially available anatase type photocatalysts, regardless of the brookite type crystal type.

The photocatalysts in this example are all based on TiO2, which is a resource abundant and inexpensive, and do not use expensive and rare W, unlike tungsten oxide photocatalysts (WO3), which are used as photocatalysts in the visible light region. It can be seen that it is possible to provide excellent light absorption properties in the visible light region.

(J) VOC decomposition evaluation test using photocatalyst The photocatalyst according to the present invention is expected to decompose volatile organic compounds (VOC). In order to evaluate the superiority or inferiority of the ability to decompose VOCs, the photocatalysts of Examples and Comparative Examples were placed in a container filled with vaporized isopropyl alcohol (IPA), and light emitted from a xenon lamp was irradiated onto the photocatalysts through a UV cut filter. The residual rate of IPA and the amount of CO2 generated were measured as they changed over time. IPA utilizes a reaction in which acetone is firstly decomposed by a photocatalyst irradiated with light, and acetone is further decomposed secondarily to generate CO2.

Figure 9 shows an overview of the equipment used in the photocatalytic VOC decomposition evaluation test. A test was conducted under the following conditions using a batch type Pyrex reactor.
i) Reactor capacity: approximately 392ml
ii) Light source: xenon lamp 300W (wavelength range: 300-800nm)
iii) Cut filter: 420nm (used to cut wavelengths below 420nm)
iv) Atmosphere: Dry air (supplied from an air compressor), room temperature v) VOC (volatile organic compound) type: IPA (isopropyl alcohol)
vi) VOC concentration: approximately 258 ppm
vii) CO2 and VOC were detected using a Plot Q column and an OV-1 column of a gas chromatograph (GC) (Agilent 3000A MicroGC, manufactured by Agilent, Inc.). The CO2 concentration was simply determined from the GC integral value based on the concentration in the air measured with a CO2 sensor (RI-2150, manufactured by Riken Keiki Co., Ltd.). The initial concentration of VOC was measured with a photoionization gas detection sensor (MiniRAE 3000, manufactured by RAE Systems), and the rate of decrease in the VOC concentration in the system was calculated from the change in the GC integral value.

FIG. 10 shows Example 2, Example 2-2, Example 3, Example 3-4, Example 3-6, and Example when irradiated with light of 300 to 800 nm (from ultraviolet light to visible light). 3-7, the VOC decomposition evaluation results of sample powders obtained in Example 4, Example 5, and Comparative Example are shown. Note that (a) shows the VOC residual rate (%), and (b) shows the amount of CO2 generated (ppm).

When irradiated with light of 300 to 800 nm (from ultraviolet light to visible light), Example 3 except Example 4, Example 3-4, Example 3-6, Example 3-7, Example 2, The photocatalysts of Example 2-2, Comparative Example, and Example 5 completely decomposed most of the VOCs within 3 hours, and the photocatalysts of Example 2-2, Comparative Example, and Example 5 completely decomposed most of the VOCs within 3 hours. It can be seen that the amount of CO2 generated by decomposing VOC is larger in the order of photocatalysts 2-2, Example 3-7, Comparative Example, Example 5, and Example 4. In particular, when irradiating with light of 300 to 800 nm (from ultraviolet light to visible light), Example 3, Example 3-4, Example 3-6, Example 3-7, Example 2, Example 2 -2 photocatalyst generates more CO2 than the anatase-type photocatalyst used as a comparative example, and it is predicted that Example 5 will also generate more CO2 than the comparative example after 3 hours. It can be seen that the performance as a photocatalyst (photocatalytic performance) is higher than that of the example photocatalyst.

FIG. 11 shows Example 2, Example 3, Example 4, Example 5, Example 5-7, Example 5-11, and Example 5- in the case of irradiation with light of 420 nm or more (visible light). The VOC decomposition evaluation results of the sample powder obtained in No. 12 are shown. Note that (a) shows the VOC residual rate (%), and (b) shows the amount of CO2 generated (ppm).

When irradiated with light of 420 nm or more (visible light), the photocatalyst of the comparative example shows almost no activity. In the photocatalyst of Example 5, the residual rate of VOC became almost 0 within 14 hours, and it was almost completely decomposed in 24 hours, with approximately 3000 ppm of CO2 being generated. This value is approximately at the same level as the amount of CO2 generated by the VOC decomposition of the photocatalyst of the comparative example in the ultraviolet to visible light range. Although the photocatalyst of Example 2 was not as good as Example 5, the residual rate of VOC was almost 0 in 23 hours, and about 2500 ppm of CO2 was generated in 24 hours, and it is predicted that the amount of CO2 generated will further increase. , it can be seen that this value has sufficient characteristics as a photocatalyst. Examples 5-7, 5-11, and 5-12 have sufficient photocatalytic properties, although they are not as good as Example 5 in both IPA decomposition and CO2 generation. The photocatalysts of Examples 3 and 4 also show a decrease in VOC over time, and the generation of CO2 along with this, so they can be said to be photocatalysts that exhibit activity in the visible light region. The change in the residual rate of VOCs in Examples 2 to 5, which increases once after decreasing and then decreases, is due to the increase in gas due to the primary decomposition of IPA by the irradiated photocatalyst and the generation of acetone. Thereafter, the acetone is subjected to secondary decomposition, and the VOC in the container decreases, while at the same time the amount of completely decomposed CO2 increases.

FIG. 12 shows sample powders obtained in Example 5, Example 6, Example 6-2, and Example 6-3 with different crystal types of TiO2 when irradiated with light of 420 nm or more (visible light). The VOC decomposition evaluation results are shown. Note that (a) shows the VOC residual rate (%), and (b) shows the amount of CO2 generated (ppm).

When irradiated with light of 420 nm or more (visible light), the amount of CO2 generated by the decomposition of VOCs decreased in the order of Examples 5, 6, 6-2, and 6-3, and the amount of CO2 generated by the decomposition of VOC decreased. It can be seen that the performance as a photocatalyst differs depending on the type. The catalyst of Example 5 exhibits extremely high photocatalytic performance in the visible light region, and exhibits photocatalytic performance equivalent to the amount of CO2 generated by VOC decomposition seen in the ultraviolet to visible light region of the catalyst of the comparative example. The photocatalytic performance in the visible light region of Example 6, Example 6-2, and Example 6-3 is not as good as Example 5, but several hundred ppm or more of CO2 is generated in 24 hours, and the photocatalytic performance is high. I understand that.

The photocatalyst according to the present invention has superior VOC decomposition ability in the ultraviolet to visible light region compared to commercially available ultraviolet photocatalysts, and also has excellent VOC decomposition ability especially when irradiated with visible light. Not only can it be used outdoors to prevent stains on walls of buildings, etc., but it can also be installed in households, offices, movie theaters, cars, trains (especially subway trains), and inside tunnels to prevent substances that cause sick house syndrome. It can decompose harmful organic compounds and maintain a healthier environment. In addition, by placing the photocatalyst according to the present invention in the air, it not only helps to purify the air, but also when the photocatalyst according to the present invention is placed in water, it can sterilize E. coli etc. and purify water. They can also be placed in or around toilets, baths, swimming pools, barbershops, and hospitals to maintain a sanitary water environment. In addition, the photocatalyst according to the present invention can decompose odor-causing substances, and can be placed inside or around toilets, baths, swimming pools, barbershops, hospitals, railway trains, and automobiles to provide a sanitary and odor-free environment. It is possible to maintain a small environment.

1 Graphite crucible 2 Raw material mixed powder 3 Vacuum heating furnace 4 High frequency heating device 5 Piping 6 Vacuum pump 11 Gas vent hole

Claims (5)

TiO2 powder, 0.1 to 5 wt% of Al, Li, Mg, or Ca, hydride thereof, or a mixture thereof powder to TiO2, and 0.1 to 5 wt% of Fe or Cu, or oxide thereof to TiO2 or a first mixed powder obtained by uniformly mixing powder of a mixture thereof, is stored in a crucible, the crucible is placed in a vacuum heating furnace, and after being evacuated, heated at 350 to 550° C. in vacuum. A method of producing a photocatalyst by heat treatment at a temperature of . A solution was obtained by dissolving 0.1 to 5 wt% of Fe or Cu, its oxide, or a mixture thereof based on TiO2 in hydrochloric acid or nitric acid, and the solution was mixed with an aqueous suspension of TiO2 powder. A second mixed powder is obtained by uniformly mixing the mixed dry powder obtained by drying and a powder of 0.1 to 5 wt% of Al, Li, Mg or Ca, a hydride thereof, or a mixture thereof based on TiO2. A method of manufacturing a photocatalyst by storing the second mixed powder in a crucible, placing the crucible in a vacuum heating furnace, evacuating it, and then heat-treating it in vacuum at a temperature of 350 to 550°C. . The method for producing a photocatalyst according to claim 1 or 2, wherein the TiO2 is anatase type, rutile type, brookite type, or a mixture thereof. TiO2 powder, 0.1 to 5 wt% of Al, Li, Mg, or Ca, hydride thereof, or a mixture thereof powder to TiO2, and 0.1 to 5 wt% of Fe or Cu, or oxide thereof to TiO2 or a first mixed powder obtained by uniformly mixing powder of a mixture thereof, is stored in a crucible, the crucible is placed in a vacuum heating furnace, and after being evacuated, heated at 350 to 550° C. in vacuum. A photocatalyst that is heat-treated at a temperature of 100 to 100 ml, which introduces oxygen defects while maintaining the crystal structure of TiO2 powder, and supports Fe or Cu, an oxide thereof, or a mixture thereof on the surface of TiO2 powder. 0.1 to 5 wt% of Fe or Cu, its oxide, or a mixture thereof based on TiO2 was dissolved in hydrochloric acid or nitric acid to obtain a solution, and the solution and an aqueous suspension of TiO2 powder were mixed. A second mixed powder is obtained by uniformly mixing the mixed dry powder obtained by subsequent drying with a powder of 0.1 to 5 wt% of Al, Li, Mg or Ca, a hydride thereof, or a mixture thereof based on TiO2. obtained, the second mixed powder is stored in a crucible, the crucible is placed in a vacuum heating furnace, and after being evacuated, heat treatment is performed in vacuum at a temperature of 350 to 550°C. A photocatalyst in which oxygen defects are introduced while maintaining the crystal structure, and Fe or Cu, its oxide, or a mixture thereof is supported on the surface of TiO2 powder..

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