JPH10230168A - Photocatalytic cell and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a photocatalytic cell which can easily be produced and is easy to be handled by forming an ultraviolet photocatalyst layer on the outer face of a light transmissive cylindrical body and forming a visible light photocatalyst layer in the inner face. SOLUTION: To produce a photocatalytic cell to be used for liquid phase reaction of decomposing harmful substances in water and gas phase reaction for decomposing maldorous substances in air, an ultraviolet photocatalyst layer is formed on the outer face of a light transmissive cylindrical body and on the other hand a visible light photocatalyst layer is formed in the inner face through an ion exchangeable substance. In this case, as the ultraviolet photocatalyst, titanium oxide, tungsten oxide, or strontium titanate are used and titanium oxide is preferable. On the other hand, as the visible photocatalyst, ruthenium(III)-bipyridine complex, phthalocyanine, polyphenylene, etc., are used and ruthenium(III)-bipyridine complex is preferable due to high durability. Such photocatalyst cells 1 are preferable to be used as a photocatalyst unit A by bonding a large number of cells.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photocatalyst cell which can be used for a liquid phase reaction such as decomposition of harmful substances in water and a gas phase reaction such as decomposition of malodorous substances in air.

[0002]

2. Description of the Related Art Photocatalysts have been widely used, including deodorizing general household goods such as air purifiers. Here, a photocatalytic device that absorbs both ultraviolet light and visible light to promote the reaction has been developed. As an example, FIG. 2 shows a perspective view (model diagram) of a photocatalytic device used for decomposing harmful substances. Light (visible light and ultraviolet light) is irradiated from above in the figure,
Raw materials toward the right (here, liquid containing harmful substances)
Is supplied, comes into contact with the photocatalytic element, and becomes a detoxified reactant.

When the structure of the photocatalyst element is partially enlarged, an ultraviolet photocatalyst layer is provided on the upper surface, and an ion exchange resin layer and a visible light catalyst layer are disposed with a transparent substrate such as glass interposed therebetween. Here, one surface of the ion exchange resin layer physically adheres to the substrate and forms an ionic bond with the visible light catalyst on the other surface,
In general, a visible light catalyst having poor adhesion to glass is fixed. In order to apply the dipping method typified by the sol-gel method, which is easy to process, to form different catalyst layers on the two surfaces of the substrate as described above, the respective surfaces are protected one by one with a seal or the like. However, this method requires time and effort to perform a protective seal, and if the protective seal is incomplete, it becomes a defective product, or a catalyst layer that is originally unnecessary is formed on the seal. There is a problem that the raw material is wasted and the cost is significantly increased. Therefore, an improvement has been required for a method for manufacturing such a photocatalytic device. Further, if a large number of the planar photocatalyst elements are to be used at the same time, a holder or the like is required, and the usability is poor.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to solve the drawbacks of the prior art, that is, to provide a photocatalyst cell which is easy to manufacture and excellent in handling, and a method for manufacturing the same.

[0005]

The photocatalyst cell of the present invention is a light-transmissive cylindrical article having an ultraviolet photocatalyst layer on the outer surface and a visible light catalyst layer on the inner surface. FIG. In addition, the photocatalyst cell manufacturing method of the present invention, as described in claim 4, plugs both ends of a light-transmissive tubular article and coats the ultraviolet photocatalyst layer on the outer surface of the tubular article by dip coating. And a step of forming a visible light catalyst layer inside the tubular article.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, it is necessary to select a material having a light absorption property as low as possible for a light having a wavelength at which the catalytic activity of a visible light catalyst is maximized, as a material of a light-transmitting cylindrical material. . When an organic substance such as an organometallic complex is used as the visible light catalyst, there is a risk of being decomposed by ultraviolet rays.
In addition, it is desirable that ultraviolet rays be completely cut off.

In the present invention, the shape of the cylindrical object can be appropriately selected. The shape can be freely selected from a circle, an ellipse, a square, a polygon, a cloud, and the like, but the thickness is desirably as thin as possible within the range of strength in view of the light transmittance, and the surface area is sufficient to obtain sufficient catalytic activity. Is desirably a large shape.

[0008] As an ultraviolet light catalyst, titanium oxide (T
iO ₂ ), zinc oxide (ZnO), tungsten oxide (W
O ₃ ) or strontium titanate (SrTiO ₃ )
Etc. are known. Among them, titanium oxide is preferably used as the ultraviolet light catalyst. Titanium oxide, particularly anatase-type titanium oxide, has an extremely high photocatalytic activity, and works effectively even with a small amount of ultraviolet light emitted from a normal fluorescent lamp. Furthermore, titanium oxide has a remarkably large absorption for ultraviolet light having a wavelength of less than 380 nm, and does not absorb light having a wavelength of 400 nm or more at all. For this reason, it is possible to prevent the ultraviolet light from reaching the visible light catalyst layer and prevent deterioration of the visible light catalyst while the visible light transmission is good. When soda-lime glass is selected as the light transmitting material, the formation of Na _x Ti _y O _z acting as a recombination center of electron-hole pairs when forming a thin film of titanium oxide on the surface at a high temperature is considered. To prevent this, form a silicon dioxide layer on the surface of soda-lime glass,
It is desirable to arrange a thin film of titanium oxide via this silicon dioxide layer. On the other hand, a ruthenium bipyridine tricomplex, phthalocyanine, polyphenylene, or the like is used as a visible light catalyst. Of these, the ruthenium bipyridine tricomplex is desirable because of its high durability.

The fixing of the ultraviolet photocatalyst can be easily performed by the dip coating method. That is, both ends of the cylindrical member are sealed with rubber stoppers or the like, immersed in a liquid in which a catalyst component and a catalyst precursor component are dissolved or dispersed, pulled up, and dried. When a liquid containing a catalyst precursor component is used, a necessary treatment such as a heat treatment or a chemical reaction is performed to obtain a catalyst. It is preferable to apply the dip coating method, since this method is low in equipment cost, has good productivity, and can obtain a uniform catalyst layer.
This method applies a method known in Japanese Patent Application Laid-Open No. 5-94765, etc., in which the above-mentioned tubular material is immersed in a liquid sol containing a catalyst or a catalyst precursor, and then lifted up to obtain the material to be treated. This is a method in which a gel layer having a catalyst or a catalyst precursor is formed on the surface and then dried or heat-treated to form a catalyst layer.

The visible light catalyst is usually fixed via an ion exchange resin. This is to improve the adhesion of the visible light catalyst layer to the substrate. However, if ordinary adhesion is sufficient, the ion exchange resin layer may be omitted. In the case of fixing via an ion-exchange resin, first, a solution in which the ion-exchange resin is dissolved is flowed into the inside of the cylindrical body, and then dried to form an ion-exchange resin layer. Thereafter, a solution in which the visible light catalyst is dissolved is flowed, and the catalyst is fixed using the binding force between the functional group of the ion exchange resin and the catalyst to form a catalyst layer.

Although one photocatalyst cell manufactured as described above may be used alone, for example, an effective photocatalyst unit can be obtained by bundling a plurality of thin cylindrical photocatalyst cells. FIG. 1 shows an example of such a photocatalyst unit.
Reference numeral 1 in the figure denotes a photocatalytic cell of the present invention,
The photocatalyst unit A is formed by bundling them. Raw materials (here, liquid containing harmful substances) are introduced into the unit from the left side of the figure by a pump (not shown). Visible light and ultraviolet light are irradiated from above this unit, and harmful substances are decomposed or oxidized by the action of the catalyst of the photocatalyst unit and discharged as a reactant. Such a photocatalytic unit has a very small pressure loss due to its structure,
Since the effective area per volume can be easily increased, fabrication is easy and the whole can be made compact.

In the above description, a transparent tubular member having a visible light catalyst on the inner surface and an ultraviolet light catalyst on the outer surface has been described. For example, a transparent tubular member having an ultraviolet light catalyst on the inner surface and a visible light catalyst on the outer surface is described. By preparing a photocatalyst cell and disposing a rod-shaped ultraviolet lamp or a visible light lamp inside the photocatalyst cell, the catalytic activity can be effectively used.

[0013]

[Example] Pyrex glass tube (outer diameter 6 mm, inner diameter 4
mm) to produce a photocatalytic cell. First, an ultraviolet photocatalyst was supported. That is, a glass tube whose both ends are closed using a masking tape is immersed in titanium tetraisopropoxide, pulled up at a speed of 10 mm / min, air-dried, and further subjected to a heat treatment at 500 ° C. for 1 hour. An anatase type titanium oxide film (thickness: 2 to 4 μm) was formed on the outer surface. Next, a visible light catalyst was supported. An ion-exchange resin alcohol solution (Napion NR-50 manufactured by DuPont) was poured into the glass tube on which the titanium oxide film was formed, and thereafter, the alcohol was volatilized to fix the ion-exchange resin in the tube. Next, this ion exchange resin was immersed in a 0.1 g / l-ruthenium bipyridine tricomplex aqueous solution for 4 hours and adsorbed by ion exchange to obtain a photocatalyst cell according to the present invention. Irradiation was performed with a mercury positive lamp D125 (125 W) manufactured by Toshiba Lighting & Technology Corp. from a distance of 120 mm from the photocatalytic cell (length: 120 mm), and the state of attenuation of trichlorethylene when the cell was contacted with water containing 120 ppm of trichloroethylene was examined. The results are shown in Table 1 together with the results in the conventional photocatalytic cell.

[0014]

[Table 1]

The photocatalyst cell of the present invention does not require masking or the like and is very easy to manufacture. From Table 1, it can be seen that the photocatalyst cell of the embodiment according to the present invention can be used in the same manner as a conventional photocatalyst cell. .

[0016]

The photocatalyst cell according to the present invention is extremely easy to manufacture, and there is no defective product in the manufacturing process.
Moreover, a compact and excellent photocatalyst unit can be formed simply by bundling.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram showing a photocatalyst unit using a photocatalyst cell according to the present invention.

FIG. 2 is a conceptual diagram showing a conventional photocatalytic device.

[Explanation of symbols]

 1. Photocatalyst cell according to the present invention A Photocatalytic unit using photocatalyst cell of the present invention

Claims (4)

[Claims] 1. A photocatalytic cell which is a light-transmissive cylindrical body, having an ultraviolet photocatalyst layer on an outer surface and a visible light catalyst layer on an inner surface. 2. The photocatalyst cell according to claim 1, wherein the visible light catalyst layer is disposed on an inner surface of the cylindrical body via an ion exchange material. 3. A photocatalytic cell, which is a light-transmissive cylindrical body, having a visible light catalyst layer on an outer surface and an ultraviolet light catalyst layer on an inner surface. 4. A step of plugging both ends of a light-transmissive tubular article to form an ultraviolet photocatalyst layer on an outer surface of the tubular article by dip coating, and a visible light catalyst layer inside the tubular article. Forming a photocatalyst cell.