JP2003225573A - Photocatalyst comprising zinc oxide and production method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a photocatalyst containing zinc oxide as a main component which is sensitive to visible light besides ultraviolet light. <P>SOLUTION: An ammonia zinc complex aqueous solution is prepared by adding an ammonia aqueous solution to a zinc oxide aqueous dispersion or by dissolving an ammonium zinc complex compound in water. The aqueous solution is added with an ammonium salt of a specified metal, an ammonia complex, or a starting raw material for MOx such as an easily decomposable nitrate. The obtained mixed aqueous solution is nebulized by a nebulizer to form minute liquid droplets 0.1-50 μm in diameter. The droplets are supplied into a high temperature reactor in a gas-liquid mixed phase by using carrier gas, and the ammonia zinc complex and the starting raw material of a metal oxide are pyrolyzed in the reactor. In this way, as compared with conventional zinc oxide powder including that by the pyrolysis of zinc nitrate, or as compared with zinc oxide powder containing nitrogen by pyrolysis, the photocatalyst comprising the metal oxide containing nitrogen and fine zinc oxide particles which is sensitive to visible light and excellent in photocatalytic function can be produced by a nebulization pyrolysis method by a relatively simple process. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a zinc oxide photocatalyst,
In particular, the present invention relates to a zinc oxide photocatalyst having a photocatalytic function by visible light, a method for producing the same, and a method for decomposing environmentally harmful substances using the catalyst as a catalyst for decomposing environmentally harmful substances.

[0002]

2. Description of the Related Art Zinc oxide powder is used in UV cosmetics as various industrial products, pharmaceuticals, vulcanization accelerators for rubber, catalysts, varistors (variable resistors), paints, and ultraviolet shielding agents. In recent years, attention has been paid to the performance as a photocatalyst,
In particular, it is drawing attention for the purpose of decomposing environmentally harmful substances. Further, as the inorganic pigment, there is a demand for a technique for coloring without containing harmful metals and the like.

As a method for producing such zinc oxide powder, there is known a method of spray pyrolyzing an aqueous solution of a zinc salt (JP-A-5-310425 and JP-A-6-1995).
No. 02 gazette, Japanese Patent Publication No. 9-501139 gazette, and Patent No.
167756). However, as a starting material for zinc oxide in these methods, zinc nitrate (Japanese Patent Laid-Open No. 6-1
99502 bulletin bulletin, Japanese Patent No. 3167756 specification) or zinc acetate (Japanese Patent Publication No. 9-501139)
Therefore, it is inevitable that organic substances containing nitrate ions and carbon remain, and the catalytic activity is low for use as a photocatalyst, and the applicability is difficult. Further, zinc oxide produced by these methods had extremely low responsiveness to visible light.

On the other hand, Japanese Patent Laid-Open No. 2001-20509
Japanese Patent Publication No. 4 discloses that zinc oxide film having nitrogen and having a visible light absorbing function is formed on a substrate by spattering using zinc oxide as a target in a nitrogen atmosphere. However, in this method, nitrogen is doped only on the surface of the zinc oxide film, so that the light absorption property of zinc oxide does not change significantly. Moreover, the production of the membrane required expensive equipment.

[0005]

Since zinc oxide has an energy band structure similar to that of titanium oxide, high photocatalytic activity similar to that of titanium oxide is expected. However, what has been reported so far absorbs only ultraviolet rays having a short wavelength, and catalytic reaction hardly occurs by visible light. Whether take any means for absorbing visible light, a current research topic. Doping with a transition metal element is one method of improving photocatalytic performance. But,
Also in this method, zinc oxide as the photocatalyst is concentrated in a single crystal or a thin film.

[0006]

Under the circumstances, the inventors of the present invention have earnestly studied to obtain a zinc oxide powder having a photocatalytic ability without depending on the sputtering method or the transition metal element doping method. We succeeded in changing the light absorption property of zinc oxide by adding nitrogen to the zinc oxide powder, and based on this, we applied for a patent. (Japanese Patent Application No. 2001-369546) The present invention is based on the above-mentioned prior art or prior invention, and as a result of further diligent research, as a result of adding MO _X to zinc oxide containing nitrogen according to the prior invention. It has been found that the visible light absorption characteristics of zinc oxide are further improved. As a result, it is possible to obtain a photocatalyst having a more excellent photocatalytic performance than that of the invention of the prior application, and also succeeded in developing a process for obtaining a photocatalyst having this excellent property by the spray pyrolysis method. It is a thing. The present invention is
It is based on this series of findings and successes.

That is, the photocatalyst of the present invention is characterized in that it is obtained by the spray pyrolysis method, contains nitrogen, and is composed of metal oxide MO _x and zinc oxide ZnO. Its light absorption characteristic is that the wavelength in the visible light region is 400 nm to 600 n.
The absorbance shows a value of 20 to 60% with respect to the spectrum of m, and the photocatalytic function can be used not only in the high energy ultraviolet light region but also in the visible light region.

The production method is as follows. One or more kinds selected from the group consisting of tungsten, vanadium, cobalt, niobium, iron, copper, tantalum, zirconium, and nickel in an aqueous solution of ammonium zinc complex as a starting material. A metal ammonium salt, ammonium complex, or nitrate that easily decomposes, such as MO _X , is added as a starting material, and this mixed solution is used as a spray solution to atomize small droplets with a droplet diameter of 0.1 μm to 50 μm with a nebulizer. generated, which was transported to the high-temperature reaction furnace by a carrier gas, that the starting material of zinc ammonium complexes and MO _X in the liquid in the reactor is thermally decomposed to generate an MO _X -ZnO powder containing nitrogen It is a feature. The produced powder can be collected by a glass filter.

Since the catalytic activity of the obtained MO _X -ZnO powder depends on the nitrogen content, the kind of metal oxide and its content, it is natural that these matters should be adjusted appropriately. Yes, it is important. That is, these items are adjusted by adjusting the thermal decomposition temperature, the concentration of ammonium salt in the spray solution, the type and concentration of the starting material of the metal oxide to be added, the type of carrier gas sent to the high temperature reactor, etc. . The standard of adjustment in that case is 10 ppm to 200 ppm for the nitrogen content as described later.
The content of 00 ppm should be adjusted as a guide. M
The O _X, should be adjusted to be content of 0.01 wt% 20 wt%.

According to the method of the present invention, ammonium zinc complex
The body is used as a starting material and nitrogen is applied using the spray pyrolysis method.
High performance MO including_X-Powder required for obtaining ZnO-based photocatalyst
To manufacture. In the present invention, an aqueous solution of ammonia zinc complex is
Manufactured as a starting material for zinc oxide, and the resulting oxidation
Zinc is a conventional method starting from nitrate or acetate
In comparison with nitrate ion, organic substances such as photocatalyst poison
The effect of impurities acting on
It And not only contains nitrogen but also MO _XIs
As described below, zinc oxide absorbs visible light.
The collection performance has changed and improved.

As a starting material of MO _{X in} the present invention, an ammonium salt or an ammonia complex salt containing M ions as much as possible is used in order to avoid impurities from remaining. For example, when vanadium is selected as M and a catalyst design in which vanadium oxide is blended is used, NH ₄ V
The O ₃ with the addition of tungsten oxide, in the case of formulation to become a catalyst design (NH ₄₎ using a _{10 W 12 O 41 · 5H 2} O. However, as long as the amount of MO _X added and the amount added are small and the catalytic activity is not adversely affected, nitrates that are easily decomposed may be used or used in combination. However, even a thermally decomposable compound, it is not preferable to use a carbon-containing compound as a starting material and should be avoided.

As mentioned above, the present invention is
It has a problem specific to the prior art, and means for solving the problem are as follows (1) to (9). (1) It consists of an oxide of a metal other than zinc represented by the general formula: MO _X —ZnO and zinc oxide ZnO, which is obtained by a spray pyrolysis method and has a visible light response. A characteristic MO _X -ZnO-based photocatalyst. M in the formula
Represents an element or metal other than zinc. x is the atomic mole ratio of metal and oxygen. (2) The oxide of a metal other than zinc is tungsten,
Item (1) above, which is an oxide of one or more elements or metals selected from the group consisting of vanadium, cobalt, niobium, iron, copper, tantalum, zirconium, and nickel. MO _X -ZnO-based photocatalyst.

(3) If the oxide of a metal other than zinc is 0.
Wherein, characterized in that is contained 01~20wt% (2) claim MO _X -ZnO-based photocatalyst according. (4) Absorbance at wavelength 400 nm to 600 nm is 2
Wherein (1), characterized in that 0 to 60% by (3) MO _X -ZnO-based photocatalyst according to any one of items. (5) 1 selected from the group consisting of tungsten, vanadium, cobalt, niobium, iron, copper, tantalum, zirconium, and nickel in an aqueous solution of ammonium zinc complex.
One or two or more metal ammonium salts, ammonium complexes or nitrates are added, and the mixed solution is sprayed with a nebulizer to form fine droplets of 0.1 μm to 50 μm, which are atomized by a carrier gas. The mixture is conveyed to a high-temperature reaction furnace, and the ammonia-zinc complex in the liquid and the ammonium salt, ammonium complex or nitrate of the above-mentioned one or more metals are pyrolyzed, and nitrogen is contained.
MO _X -Z characterized by producing and recovering a photocatalyst consisting of a metal oxide represented by _X and zinc oxide ZnO
Method for producing nO-based photocatalyst. In the formula, M represents a metal other than zinc.

(6) Ammonia concentration in the spray solution, MO
_The nitrogen content is controlled by adjusting the type and concentration of the starting compound of _X, the thermal decomposition reaction temperature in the high temperature reactor, or the type of carrier gas. Method for producing MO _X -ZnO-based photocatalyst. (7) Nitrogen content of 10ppm to 20000ppm
Is adjusted to a range of M.
Method for producing O _X -ZnO-based photocatalyst. (8) An MO _X -ZnO-based photocatalyst for decomposing harmful chemicals, which comprises using the photocatalyst according to any one of (1) to (4) for decomposing harmful chemicals. (9) In the presence of the photocatalyst described in any one of (1) to (4) above, harmful chemical substances such as aldehyde, chlorobenzene, chlorophenol, and dioxins are irradiated with ultraviolet rays or visible light, and these harmful A method for decomposing a harmful substance, characterized by decomposing the substance.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, a starting material for MO _X containing M ions is added to an aqueous solution of an ammonia zinc complex, and the mixed solution is nebulized to have a droplet diameter of 0.1 μm to 50 μm.
A small droplet of μm is atomized, and the droplet is sent to a high temperature reaction furnace in a gas-liquid mixed phase state using a carrier gas of argon, helium, nitrogen, oxygen or air, and ammonia zinc inside the reaction furnace. A method for producing an MO _X -ZnO-based photocatalyst, characterized in that a starting material of a complex and MO _X is thermally decomposed to produce an MO _X -ZnO powder containing nitrogen. The obtained MO _X -ZnO powder has a hollow spherical shape or a hemispherical shape,
The spherical wall is composed of small particles. Further, the obtained MO _X -ZnO powder has an orange color because it contains nitrogen. The color density depends on the nitrogen and MO _x contents. The zinc oxide powder obtained by the conventional technique starting from zinc nitrate and spray-pyrolyzing its aqueous solution is white, including the one in which nitrate radicals remain, and is mainly composed of the zinc oxide containing nitrogen of the present invention. The powders to be distinguished can be distinguished in this respect.

As described above, the nitrogen content can be controlled by the thermal decomposition temperature, the concentration of ammonia in the spray solution, the type and concentration of MO _X , and the type of carrier gas fed into the high temperature reactor. The content is 10p
It is preferable to control in the range of pm to 20000 ppm. When the nitrogen content is less than 10 ppm, the effect of nitrogen addition is small, and no practical improvement of the photocatalytic function is observed. Also, the nitrogen content is 20000 pp
When it is more than m, it precipitates as a nitride and becomes unstable in the atmosphere, which is not suitable as a photocatalytic material.

The amount of MO _X added is from 0.01 wt% to 20%.
Up to wt% is optimal. When the added amount is less than 0.01 wt%, the visible light absorption effect is not improved so much that the actual photocatalytic activity is not recognized. Also, if the added amount is 20 wt% or more, the essential photocatalytic properties of zinc oxide may not be exhibited, and rather the opposite effect may be brought about. Therefore, when actually designing the catalyst, pay sufficient attention to this point. It is important to do so.

The present invention will be described in detail below with reference to the accompanying drawings. FIG. 1 is a schematic view showing a specific example of the apparatus of the present invention. In the method of the present invention, the spray aqueous solution is continuously supplied from the solution storage container 1 to the nebulizer 3 for atomizing fine droplets by using the peristaltic pump 2 for liquid feeding, and the generated droplets are sucked by the aspirator 4 to be a carrier. MO _X -ZnO fine particles containing nitrogen by being entrained in the carrier gas sent from the gas supply device 5 and sent to the reaction tube 7 having the high-temperature heating body 6 to cause thermal decomposition reaction of droplets in the reaction tube 7. Are generated and the fine particles are collected by the glass filter 8.

In order not to store water, the glass filter 8 is heated by the flexible heater 9 to control the temperature. Water vapor emitted after the glass filter 8 is removed from the trap 10. The temperature of the reaction tube 7 is adjusted by the temperature controller 11. The gas flow rate is monitored by a gas flow meter.

The concentration of the ammonia-zinc complex aqueous solution used in the present invention is 0.0001 mol / liter to 1.5 mol / liter.
A range of liter is suitable, preferably 0.005
The range of mol / liter to 0.5 mol / liter is preferable. When the solution concentration is less than 0.0001 mol / liter, the amount of fine particles of zinc oxide produced is extremely small. On the contrary, when the solution concentration is higher than 1.5 mol / liter,
Solution saturation increases too much and precipitates out.

Argon, helium, nitrogen, oxygen or air is used as the carrier gas, and the flow rate of the carrier gas is suitably in the range of 0.02 liter / min to 25 liter / min, preferably 0.1. A range of liter / minute to 5 liter / minute is preferable. When the flow rate of the carrier gas is low, the residence time of the liquid droplets in the reaction tube becomes long, and the zinc oxide fine particles produced are deposited on the reaction tube wall,
Cannot be recovered. When the flow rate of the carrier gas is high, the retention time of the droplets in the reaction tube is too short and the ammonia-zinc complex passes through without being completely decomposed, so that a powder containing only zinc oxide cannot be obtained.

As a method for making the spray aqueous solution into small droplets, there are a method using a nebulizer, a method using a spray nozzle and the like. In order to obtain a fine droplet having a narrow droplet diameter distribution, it is preferable to use a nebulizer. The method is good.

MO _X- containing nitrogen obtained according to the invention
The ZnO fine particles have good monodispersity and can be obtained in the range of 0.001 μm to several tens of μm by adjusting the concentration of the spray solution. However, in consideration of the yield of the produced fine particles and the function improvement due to atomization, it is preferable. 0.1 μm to 10 μm
The range is good. The diameter of the MO _X -ZnO fine particles can be measured by various methods, for example, the scanning electron microscope.

The temperature of the reaction furnace required for the thermal decomposition is preferably in the range of 200 ° C to 1500 ° C. If the temperature is lower than 200 ° C, the thermal decomposition of the ammonia zinc complex is difficult to proceed, and 1
If the temperature is higher than 500 ° C., a solid phase reaction occurs between zinc oxide and MO _X to form a composite oxide having poor photocatalytic performance, which is not preferable. Further, the ammonia-zinc complex thermal decomposition reaction in the present invention is represented by the following formula. Zn (NH ₃ ) ₄ (OH) ₂ → ZnO _1-y N _y + NH ₃
+ H ₂ O Of course, at that time, the thermal decomposition reaction of the starting material of MO _X is also performed. For example, NH ₄ V as a starting material for vanadium oxide
When O ₃ is used, the thermal decomposition reaction is represented by the following formula. NH ₄ VO ₃ → VO _x + NH ₃

The MO _X -ZnO-based photocatalytic performance by spray pyrolysis is evaluated using an acetaldehyde photolysis reaction. The reaction is carried out in a closed circulation system device (500 ml). As the reaction conditions, the amount of the photocatalyst was 0.1 g, and the reaction gas was 660 TorrCH ₃ CHO / He (670 ppm) and 1
It is a mixed gas of 00 TorrO ₂ . Xe for visible light source
Lamp (LA-254Xe.λma, manufactured by Hayashi Clock Industry Co., Ltd.
x = 470 nm) was used. The visible light was cut at a short wavelength (λ <390 nm) by inserting a filter (L39 manufactured by Kenko Co., Ltd.) in the optical path. The time-dependent change in the concentration of CO ₂ gas produced by oxidizing acetaldehyde gas by light irradiation is measured by a gas chromatograph.

[0026]

EXAMPLES Next, the present invention will be described in more detail by way of examples, which should not be construed as limiting. Example 1 A 0.1 mol / liter Zn (NH ₃ ) ₄ (OH) ₂ aqueous solution was used, an air gas was used as a carrier gas, a spray pyrolysis temperature was 800 ° C., and nitrogen was contained according to the above method. Vanadium oxide-zinc oxide photocatalyst (NV-ZnO)
It was created. The vanadium oxide content is 1.0 wt%. Also, the reaction tube is made of ceramic with an inner diameter of 30 mm and a length of 1 meter, and a horizontal electric heating furnace (heating length 0.8
It is installed in (m). The carrier gas flow rate was constant at 5.0 liters / minute.

The nitrogen content of the NV-ZnO photocatalyst produced under the above conditions was 3000 ppm in elemental analysis. The geometry and surface morphology of the NV-ZnO particles produced under the above conditions are shown in the transmission electron microscopic photograph of FIG.

The particle shape is hollow and spherical, and the average particle diameter is about 0.90 μm. The BET specific surface area measured by adsorption of nitrogen at 77 K was 53.3 m ² / g. Further, FIG. 3 is a transmission electron microscope photograph at a higher magnification than FIG. 2, but as seen in the photograph, the wall of each particle is composed of small particles (40 nm to 60 nm). Further, the crystal form of the produced NV-ZnO powder was measured by an X-ray diffractometer. As a result, it was confirmed that the obtained metal oxide-zinc oxide mixed oxide powder had a hexagonal wurtzite type crystal structure. The average primary particle size is 10.2
It was about nm. No diffraction peak for vanadium oxide could be confirmed. From this, it was found that vanadium oxide was highly dispersed inside the zinc oxide particles. This is also one of the features of the mixed oxide according to the present invention based on the spray pyrolysis method. That is, an aqueous solution of a homogeneous mixture of a plurality of starting materials is prepared and atomized to form fine mist droplets, water vaporization and precipitation of dissolved components occur in each fine droplet, and then each precipitate Since a series of processes such as thermal decomposition of (1) occur simultaneously and uniformly without being particularly unevenly distributed, a very uniform mixed oxide can be obtained.

For the evaluation of the light absorption characteristics of NV-ZnO produced under the above conditions, the absorbance at a wavelength of 300 to 800 nm was measured using an ultraviolet-visible spectrophotometer. The result is shown in FIG. The absorbance of NV-ZnO has a wavelength of 40.
The absorbance at 0 to 600 nm was 20 to 60%. It can be seen that the NV-ZnO powder produced by the method of the present invention also absorbs a part of visible light while maintaining a high absorptivity for ultraviolet rays.

The activity of the NV-ZnO photocatalyst for the acetaldehyde photolysis reaction was measured using the above-mentioned method for evaluating the catalytic performance. The result is shown in FIG. The visible light irradiation advances the acetaldehyde decomposition reaction. The production concentration of carbon dioxide reached 395 ppm in 6 hours. As a result, 34.0% of 581 ppm acetaldehyde introduced into the reaction system was completely decomposed to produce harmless carbon dioxide and water.

Example 2 0.10 mol / liter Zn (NH ₃ ) ₄ (OH) ₂ aqueous solution was used, air gas was used as the carrier gas, and the spray pyrolysis temperature was 800 ° C. Nitrogen-containing tungsten oxide-zinc oxide photocatalyst (NW-Zn
O) was created. Content of tungsten oxide is 1.8w
It was t%.

The nitrogen content of NW-ZnO produced under the above conditions is 2000 ppm by elemental analysis, and the geometrical shape and surface morphology of the particles have the same structure as NV-ZnO described above. The BET specific surface area was 46.9 m ² / g.

For the evaluation of the light absorption characteristics of NW-ZnO produced under the above conditions, the absorbance at a wavelength of 300 nm to 800 nm was measured using an ultraviolet-visible spectrophotometer. The result is shown in FIG. Regarding the absorbance of NW-ZnO, the absorbance at a wavelength of 400 to 600 nm is 20 to 50%. It has been shown that the NW-ZnO powder produced by the method of the present invention also absorbs a part of visible light while maintaining a high absorptivity for ultraviolet rays.

The activity of the NW-ZnO photocatalyst for the acetaldehyde photolysis reaction was measured using the above-mentioned method for evaluating the catalytic performance. The result is shown in FIG. The visible light irradiation advances the acetaldehyde decomposition reaction. The production concentration of carbon dioxide reaches 329 ppm in 6 hours. That is, 28.3% of 582 ppm acetaldehyde introduced into the reaction system was completely decomposed to produce harmless carbon dioxide and water.

Example 3 NV-ZnO and NW-Z produced in Example 1 and Example 2
Using the nO photocatalyst, the decomposition reaction was also performed under the same conditions with chlorobenzene (ClC ₆ H ₅ ) instead of acetaldehyde as an environmental pollutant. When using NV-ZnO,
The production concentration of carbon dioxide reached 785 ppm in 6 hours. That is, 20.8% of 600 ppm chlorobenzene introduced into the reaction system was completely decomposed to produce harmless carbon dioxide and water. Alternatively, when NW-ZnO was used, the carbon dioxide production concentration reached 653 ppm in 6 hours. That is, 18.1% of 600 ppm chlorobenzene introduced into the reaction system was completely decomposed to produce harmless carbon dioxide and water.

Comparative Example 1 For comparison, a zinc oxide powder (ZnO) was produced under the same conditions as NV-ZnO using zinc nitrate as a starting material instead of the ammonia zinc complex. The light absorption characteristics and photocatalytic performance of the obtained ZnO are shown in FIGS. 4 and 5. Comparative Example ZnO
Did not give the same results as NV-ZnO or NW-ZnO. The production concentration of carbon dioxide is 47 pp in 6 hours
It was m. Only 4.0% of the 582 ppm acetaldehyde introduced into the reaction system decomposed.

Comparative Example 2 Zinc oxide powder (N-ZnO powder) (N-ZnO powder) (N-ZnO)
-ZnO) was also produced. The light absorption characteristics and photocatalytic performance of N-ZnO are shown in FIGS. 4 and 5. Compared to ZnO of Comparative Example 1, N-ZnO also absorbs a part of visible light and has a visible light catalytic function. The production concentration of carbon dioxide reached 216 ppm in 6 hours. As a result, 18.6% of the 582 ppm concentration of acetaldehyde introduced into the reaction system was decomposed.

[0038]

As described above, according to the present invention, a starting material of MO _x such as ammonium salt containing M ions, ammonia complex salt or easily decomposable nitrate such as ammonium salt containing M ion as a starting material is added. Then, this mixed solution is atomized by a neprise as a spray solution, the droplets are pyrolyzed in a high-temperature reaction furnace by suction of an aspirator, and the generated powder is recovered by a glass filter by a simple manufacturing process. a spherical, having a high surface area, it can be produced MO _X -ZnO based photocatalyst containing nitrogen.

The MO _X -ZnO powder containing nitrogen absorbs a part of visible light without affecting the ultraviolet absorption effect of zinc oxide. Therefore, the zinc oxide of the present invention can be used as a photocatalyst, in which case the photocatalyst responds to visible light as compared with the conventional photocatalyst that was utilized only in the high energy ultraviolet light region. , For sunlight whose spectrum in the visible light region occupies a large part,
It is expected that the utilization efficiency can be improved considerably, and its significance is extremely large. And, in particular, it is possible to exert an effect for purifying air in the room by utilizing natural light, and further for antifouling of walls and upholstery. Of course, since the photocatalyst according to the present invention is an oxide catalyst, it is stable against heat, and is subjected to a reaction process of thermally decomposing environmentally harmful substances in a furnace and used directly in the decomposition reaction process, or This catalyst can be used for the flue gas after the end of the process and irradiated with light, thereby further promoting and supplementing the decomposition.

[Brief description of drawings]

FIG. 1 is a schematic view showing a specific example of an apparatus used in the method of the present invention.

2 is a drawing based on SEM showing a state of vanadium oxide-zinc oxide powder containing nitrogen of Example 1. FIG.

FIG. 3 is an SEM-based drawing showing a state of vanadium oxide-zinc oxide powder obtained by further enlarging FIG. 2.

FIG. 4 is a graph showing light absorption characteristics of each example and each comparative example.

FIG. 5 is a graph showing photocatalytic properties of each example and each comparative example.

[Explanation of symbols]

1: Solution storage container 2: Helista pump 3: Nebulizer 4: Aspirator 5: Carrier gas supply device 6: High temperature heating element 7: Reaction tube 8: Glass filter 9: Flexible heater 10: Trap 11: Temperature controller

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) B01J 27/24 C01B 21/06 A 35/08 C01G 31/00 C01B 21/06 41/00 A C01G 31 / 00 B01D 53/36 J 41/00 ZABG F term (reference) 4D048 AA11 AA19 AB03 BA08Y BA16X BA23X BA24Y BA27X BA35Y BA36Y BA37Y BA38Y BA41X BA46X BB01 BC01 BC05BC35BC54BC54ABB4A35AB35A35AB48B35A35AB08B35A35A4 BC55A BC56A BC60A BC60B BC66A BC67A BC68A BD06A BD06B BE17C CA01 CA10 CA11 CA19 DA05 EA04Y EC27 FA01 FB34 FB80 FC02 FC07 FC08

Claims (9)

[Claims] 1. A nitrogen-containing compound having a general formula: MO _X —ZnO obtained by a spray pyrolysis method and having a visible light response.
An MO _X -ZnO-based photocatalyst comprising an oxide of a metal other than zinc and zinc oxide ZnO. In the formula, M represents an element or metal other than zinc. x is the atomic mole ratio of metal and oxygen. 2. An oxide of a metal other than zinc is one or more elements or metals selected from the group consisting of tungsten, vanadium, cobalt, niobium, iron, copper, tantalum, zirconium, and nickel. The MO _X -ZnO-based photocatalyst according to claim 1, which is an oxide. 3. The oxide of a metal other than zinc is 0.01
3. 20 wt% is contained.
The MO _X -ZnO-based photocatalyst described. 4. The MO _X -ZnO-based photocatalyst according to claim 1, wherein the absorbance at a wavelength of 400 nm to 600 nm is 20 to 60%. 5. An aqueous solution of an ammonium zinc complex, wherein an ammonium salt or ammonium complex of one or more metals selected from the group consisting of tungsten, vanadium, cobalt, niobium, iron, copper, tantalum, zirconium and nickel. Alternatively, nitrate is added, and the mixed solution is sprayed with a nebulizer to form fine droplets of 0.1 μm to 50 μm in a mist form, which is transported to a high temperature reactor by a carrier gas, and the ammonia zinc complex in the liquid is generated. And an ammonium salt, an ammonium complex, or a nitrate of the above-mentioned one or more kinds of metals, which contains nitrogen and has a general formula:
To generate more becomes photocatalytic oxide of a metal represented by MO _X and zinc oxide ZnO, and recovering MO _X
-A method for producing a ZnO-based photocatalyst. In the formula, M represents a metal other than zinc. 6. The nitrogen content is controlled by adjusting the ammonia concentration in the spray solution, the type and concentration of the MO _X starting compound, the thermal decomposition reaction temperature in the high temperature reactor, or the type of carrier gas. The method for producing a MO _X —ZnO-based photocatalyst according to claim 5, characterized in that 7. Nitrogen content from 10 ppm to 2000
Manufacturing method of MO _X -ZnO-based photocatalyst according to claim 6, wherein is adjusted to a range of 0 ppm. 8. A MO _X -ZnO-based photocatalyst for decomposing harmful chemical substances, which comprises using the photocatalyst according to any one of claims 1 to 4 for decomposing harmful chemical substances. 9. A harmful chemical substance such as aldehyde, chlorobenzene, chlorophenol, and dioxins is irradiated with ultraviolet rays or visible light in the presence of the photocatalyst according to any one of claims 1 to 4, and these harmful substances are irradiated. A method for decomposing toxic substances, characterized by decomposing.