Photocatalyst body

Description: TECHNICAL FIELD [Detailed description of the invention]

【0001】

[Technical field to which the invention belongs]

The present invention relates to a photocatalyst that oxidatively decomposes an organic compound suspended in a gas or liquid (hereinafter referred to as a fluid).

【0002】

[Conventional technology]

The number of petrochemical products is increasing, and complex contamination of harmful organic compounds is becoming a problem both inside and outside the living environment. As a means for solving this, there is a purification method using oxidative decomposition by a photocatalytic semiconductor.

【0003】

For example, there is a method in which a photocatalytic semiconductor is supported on the surface of a gas constituting the device or equipment, and the device or device is placed in a fluid in which the harmful organic substance is suspended so that the harmful organic substance is brought into contact with the photocatalytic semiconductor. In this case, in order to exert the photocatalytic function at a high level, it is necessary that the surface area of the photocatalytic functional layer is large and that the photocatalytic semiconductor is sufficiently activated by electromagnetic waves having an excitation wavelength.

【0004】

Therefore, various proposals have been made conventionally regarding a technique for increasing the surface area of a substrate and a film forming technique for forming a photocatalytic functional layer (see, for example, JP-A-5-309267 and JP-A-8-196903).

【0005】

[Problems to be Solved by the Invention]

However, these have drawbacks such as a low rate of activation by electromagnetic waves of excitation wavelength even if the area of the photocatalyst functional layer is increased by simply increasing the surface area, or poor contact efficiency between the fluid and the photocatalyst semiconductor. .. Further, in order to form an apparatus or an instrument, it is preferable that the substrate supporting the photocatalytic semiconductor has a flexibility that allows molding such as press working, and that can be rolled or bent. However, in particular, a substrate whose material is an inorganic material does not have such a condition, and the range in which a photocatalyst can be used is narrow. It has been proposed to use a Ti plate as a substrate (Japanese Patent Laid-Open No. 8-246192) or a wire mesh (SUS304) (Japanese Patent Laid-Open No. 8-215577). There is a problem that the adhesive force of the photocatalyst functional layer is weak.

【0006】

Therefore, an object of the present invention is to provide a photocatalyst body capable of expanding the surface area of the substrate, activating the photocatalytic functional layer formed on the surface thereof almost uniformly, and increasing the contact efficiency between the fluid and the photocatalytic semiconductor. It is to be.

【0007】

[Means for solving problems]

In order to achieve the above object, in the present invention, a mesh member and a wire rod made of a wire rod made of any one metal material selected from stainless steel or Al, Cu or Ti and an alloy thereof. The technical means of having a flat plate-like substrate having a porous layer on which particles made of the metal material are supported and sintered on the surface of the metal material and a photocatalyst functional layer formed on the surface thereof was adopted. In the present invention, the substrate is not limited to a flat plate, but is a three-dimensional (cube, ball, honeycomb, lattice, etc.) network formed by combining the mesh members and a wire rod. It is also possible to use a substrate having a porous layer on which particles made of the metal material are supported and sintered on the surface of the metal material. In the present invention, the plain weave wire mesh can be used as it is as the mesh-like member, but the plain weave wire mesh may be reduced. In the present invention, regular particles (spherical or granular powder particles) or amorphous particles (particles having sharp angles such as angular powder particles) can be used as the metal particles. In particular, by using amorphous particles, the depth of the recesses formed on the surface of the substrate is increased, which is effective in increasing the surface area. In the present invention, since a porous layer made of metal particles is formed on the surface of the wire rod constituting the network member or the three-dimensional network, the surface area of the substrate can be increased. Further, in the present invention, since the porous layer is formed of metal powder, a substrate having high mechanical strength can be obtained. In the present invention, punching metal can be used instead of the mesh-like member. This punching metal is not limited to a flat plate shape, and may be a structure in which flat plate shapes are three-dimensionally combined.

【0008】

BEST MODE FOR CARRYING OUT THE INVENTION

The details of the present invention will be described below with reference to the drawings. FIG. 1 is a front view of a photocatalyst according to an embodiment of the present invention. In the figure, 1 is a photocatalyst, 2 is a substrate, 3 is a wire mesh, 4 is a porous layer, and 5 is a photocatalytic functional layer. The appearance of the substrate is schematically shown in FIG.

【0009】

The photocatalyst 1 is a plain woven wire mesh 3 made of austenitic stainless steel or a wire made of one or more metal materials such as Al, Cu, Ti and their alloys, and a porous wire mesh 3 formed on the surface of each wire. It has a substrate 2 having a quality layer 4 and a photocatalytic functional layer 5 formed on the surface thereof. The plain weave wire mesh 3 is manufactured by interlacing vertical lines and horizontal lines one by one at regular intervals, and various openings and openings are made by combining the number of meshes (mesh) and the wire diameter. Those with a rate can be obtained (see JIS G 3555). In the present invention, it is preferable to use a wire mesh having a mesh of 2 to 100 mesh and a wire diameter (d) of 0.10 to 2.00 mm. Among these wire meshes, those having an opening (a) of 0.50 to 3.0 mm and an aperture ratio (R) of 30.0 to 60.0% are more preferable. R is (a / a + d)²Calculated as x100. As the metal material for forming the wire mesh, austenitic stainless steel such as SUS304, SUS310, and SUS316 can be used. Not limited to this, Al or its alloy (Al-Si-Mg system), Cu or its alloy or Ti or its alloy (Ti-Mn, Ti-Cr, etc.) can also be used.

【0010】

In the present invention, since the mesh of this seed wire mesh needs to be fine to some extent in order to be able to hold the fine metal powder on its surface, the plain weave wire mesh described above is used, or a uniform thickness is applied to the surface of the wire mesh. It is preferable to roll it so that the porosity of the above can be formed. The rolling ratio is preferably in the range of 5 to 50%. If the rolling ratio is less than 5%, the effect is ineffective, while if the rolling ratio exceeds 50%, the mesh becomes finer than necessary and it becomes difficult for the fluid to permeate. The thickness of the wire mesh after reduction is preferably in the range of 0.5 to 3.0 mm. This is because if the thickness is less than 0.5 mm, the strength is insufficient, and if it exceeds 3.0 mm, the transmission resistance becomes too large.

【0011】

In the present invention, a porous layer 4 made of fine metal powder is formed on the surface of the wire mesh 3 described above. This porous layer is obtained by applying a slurry (solid content 60 to 80% by weight) obtained by mixing a metal powder having an average particle size of 10 to 400 μm with a solvent such as water to the surface of a wire mesh, drying it, and then sintering it. .. Examples of this metal material include austenitic stainless steels such as SUS304, SUS310, and SUS316, Ti or its alloys (Ti-Mn-based, Ti-Cr-based, etc.), Cu or its alloys, or Al or its alloys (Al-Si-). Mg type) is used. If the particle size of the metal powder is too small, the price will be high (the pulverization time will be long), and if it is too large, fine pores cannot be obtained. Therefore, it is preferable to use a metal powder having an average particle size of 10 to 400 μm. The sintering temperature may be determined according to the material of the metal powder, but if it is too low, a sufficient sintering density cannot be obtained and the strength decreases, while when the temperature approaches the melting point of the metal, the particles are fused. On the contrary, coarse pores are formed, so the range of 800 to 1000 ° C for SUS, Ti, and Cu and 300 to 400 ° C for Al is preferable.

【0012】

The porous layer 4 thus obtained preferably has a pore size of 5 to 1000 μm. If the pore diameter is too large, even if it is used for purifying air, it will not be possible to block fine foreign substances and clean air will not be obtained, so it must be 1000 μm or less. Further, if the thickness of the porous layer is thin, the strength is insufficient, while if it is thick, the permeation resistance increases. Therefore, a thickness of 10 to 100 μm is preferable.

【0013】

The metal powder that forms the porous layer is a particle for increasing the surface area, and can be a standard particle (spherical or granular powder particle) or an amorphous particle (particle with sharp corners such as a square powder particle). Many, but may be scaly or flaky. When a melting means such as baking is used for fixing to the substrate, it is preferable that the material is the same as that of the substrate because of its good compatibility. However, even if the materials are different, it can be fixed without using an appropriate amount of an appropriate binder. If the substrate and the particles for increasing the surface area are made of different materials, it is necessary to match the coefficient of linear expansion or to maintain the elasticity commensurate with the linear expansion of either material. Is. As the binder, inorganic glass, frit (glaze), metal powder, ordinary thermoplastic resin, or the like can be used. In order to stack metal particles for increasing the surface area, there are means such as repeating transfer (printing) using a screen in addition to repeating spraying and dipping several times. Then, in order to laminate the particles coarsely as the substrate side is densely separated from the substrate during lamination, the degree of dispersion (density) of the particles in the spray liquid or dipping liquid is adjusted, or the coarseness of the screen used for printing is adjusted. select. It is also possible to select the particle size of the particles to be laminated. Further, it is also possible to select the laminated structure in the cross section. That is, several screens that can be accurately positioned are used, and the structure is such that the substrate side is the base side and the apex is provided at a position away from the substrate in the cross-sectional form of the stack. Even with this structure, the particles for increasing the surface area are as a result of being coarsely laminated as the substrate side is densely separated from the substrate.

【0014】

The photocatalyst functional layer 5 is, for example, TiO.₂A sol liquid containing a photo-contact semiconductor such as the above can be adhered to the surface of a substrate by spraying or dipping, dried, and then baked at a temperature of 50 ° C to less than 500 ° C to form. If amorphous titanium peroxide or titanium oxide is mixed in the sol in a titanium weight ratio (dry amount) in the range of 1: 1 or 1: 5, the photocatalytic semiconductor can be mixed at a relatively low temperature. The particles can be firmly supported.

【0015】

In addition, Pt, Ag, Rh, RuO for functional complementation such as antifungal sterilization₂, Nb, Cu, Sn, NiO particles are mixed in a small amount, or zeolite, silica (silicon dioxide), alumina, zinc oxide, magnesium oxide, rutile type is added to improve the decomposition performance by redox. Inorganic materials such as titanium oxide and zirconium phosphate, various activated carbons, and porous phenol resins and melamine resins can be mixed in one or more.

【0016】

It is also possible to spray a protective material such as an aqueous solution of titanium peroxide on the surface of the substrate to perform a base treatment for forming a protective film, and then form the photocatalyst functional layer. In either case, if a film is formed in advance with PTA (oxysantinic titanium acid ...... titanium peroxide aqueous solution), TiO₂Adhesion and ductility of the sol liquid are improved, and it is easy to get wet, and a light-touch functional layer can be uniformly and widely formed on the surface of the substrate. PTA has excellent ductility even when the substrate is a metal such as stainless steel, and TiO₂It is effective for applying the sol solution widely and evenly. PTA also functions as a binder, but it does not contain ceramics in composition and is compatible with metals, so the photocatalytic functional layer formed on the surface of the substrate peels off even if the substrate bends or vibrates. There are few things.

【0017】

Other photocatalytic semiconductors include ZnO and SrTiO₃, CdS, CdO, CaP, InP, In₂O₃, CaAs, BaTiO₃, K₂NbO₃, Fe₂O₃, Ta₂O₅, WO₃, SaO₂, Bi₂O₃, NiO, Cu₂O, SiC, SiO₂, MoS₂, MoS₃, InPb, RuO₂, CeO₂and so on. Among them, titanium oxide TiO₂(Anatase type) is inexpensive, has stable properties, is harmless to the human body, and is the best photocatalyst.

【0018】

The catalytic function of photocatalytic semiconductors is the excitation wavelength above the bandgap of semiconductors such as metal oxide (electromagnetic waves with excitation wavelength, TiO).₂In the case of (ultraviolet region), electron cleavage occurs in the semiconductor by irradiating it, and OH- and O are generated on the surface.₂-Active radicals Hydroxyl groups and active oxygen are generated, and organic compounds in contact with them are decomposed by oxidation or reduction. As a result, foul odors and oil stains can be cleaned. In addition, the same function can kill bacteria and viruses (sterilization).

【0019】

With the structure of the present invention, the surface area of the photocatalytic functional layer is large, and the electromagnetic wave of the excitation wavelength irradiated from the outside easily reaches the particles deep in the photocatalytic functional layer, and the photocatalytic functional layer is activated in a wide range. Will be done. Further, since the fluid passing through such a laminated structure portion hits the wall of the laminated structure and is reflected, or enters a recess and temporarily stays there, there are many opportunities for organic substances suspended in the fluid to come into contact with the photocatalytic semiconductor. .. Therefore, the photocatalyst has high performance.

【0020】

The photocatalyst body constructed as described above can be used in various forms, but it may be used by forming photocatalyst functional layers on both sides of a single flat substrate. In this case, an electromagnetic wave source of excitation wavelength is arranged along both side edges of the flat plate, one surface (front) of the flat plate is irradiated with the electromagnetic wave supply source of one excitation wavelength, and the other is an electromagnetic wave source of electromagnetic waves of the other excitation wavelength. It is possible to irradiate the front surface (back surface).

【0021】

In the present invention, since the substrate has a large number of fine through holes, this photocatalyst can be used as various filters. Not only a filter as an element, but also, for example, when it is used as a filter for a gas that circulates in the refrigerator by forming an inner wall of the refrigerator that is sealed like a refrigerator, vegetables and fruits such as ethylene gas can be removed from the air in the refrigerator. It can remove harmful gases that are wasted, and can also remove unpleasant odors such as hydrogen sulfide and mercaptan. In this case, since the inner wall functions as a filter, the volume inside the refrigerator is not reduced and the filter does not get in the way as compared with the case where the filter is separately provided in the refrigerator.

【0022】

Further, such a photocatalyst can have a sound deadening function, a visual shielding function, or a wave eliminating function or a defoaming function when the fluid is in a liquid phase, as well as a cleaning function depending on the mode of use. Muffling is, for example, when a photocatalyst is used as a boundary wall plate that separates a roadway from a human road on a road. Is to lead to the complicated internal space of the plain weave wire net and absorb the transmitted energy. The visual shielding function is a function of blocking the passage of light, which makes it possible to use the photocatalyst as a partition or the like. In addition, wave-dissipating is similar to absorbing sound waves. The wave motion of the liquid makes the contact opportunity between the organic compound suspended in the liquid and the photocatalytic semiconductor non-uniform, but the wire mesh temporarily stops the fluid in the internal space of the wire mesh, and the contact opportunity with the photocatalytic semiconductor is almost uniform. become.

【0023】

In addition, the photocatalyst of the present invention can be used for air conditioners and exhaust gas treatment devices, filters, indoor wall boards for toilets and buildings, algae-proof ornamental water tank walls, swimming pool walls, and the like. The photocatalyst of the present invention is not limited to a flat plate, and may have various shapes depending on the application, installation location, and the like. That is, in the present invention, the sheet-shaped photocatalyst shown in FIG. 1 can be processed into a predetermined shape or can have a three-dimensional shape such as a ball shape, a honeycomb shape, or a lattice shape formed by combining them. Of these, for example, honeycomb-shaped ones are particularly useful for exhaust gas purification. FIG. 3A shows an example in which the sheet-shaped photocatalyst 1 is formed into a ball shape. FIG. 3B shows an example in which a sheet-shaped photocatalyst 1 and a wavy photocatalyst 1'are combined in a honeycomb shape. FIG. 3C shows an example in which the sheet-shaped photocatalyst 1 is fixed to the support frame 20 in multiple stages. Further, in the case of a flat plate (flat membrane), one end is fixed at a predetermined position, and a vibration applying means is connected to the other end (free end) to continuously or intermittently vibrate the fluid to be processed. Opportunities for contact with photocatalytic semiconductors increase. This structure is particularly useful as a wave-dissipating means for swimming pools.

【0024】

[Example]

Example of photocatalyst production Four types of plain weave wire mesh using austenitic stainless steel SUS316 as a wire rod were rolled at a rolling reduction of 15% or 30% to prepare a wire mesh with a thickness of 2.0 to 1.0 mm. In addition, a plain weave wire mesh formed of pure Al wire was rolled at a rolling reduction of 20% to prepare a wire mesh with a thickness of 1.5 mm. In addition, a plain weave wire mesh formed of Ti alloy (PC130A) wire was rolled at a rolling reduction of 10% to prepare a wire mesh with a thickness of 1.5 mm. Next, SUS316 powder, Cu powder, Ti powder or Al powder was applied to both sides of the wire mesh and then sintered to prepare a substrate of the type shown in Table 1. Water was used as a binder for sintering each metal powder.

【0025】

[table 1]

<img file="JP2000051712A_D0001.tif" />【0026】

Next, as a photocatalytic functional material, an armofus-type titanium peroxide aqueous solution (0.84 w%): anatase-type titanium oxide aqueous solution (0.84 w%): colloidal silica aqueous solution (0.84 w%) was mixed at a ratio of 3: 7: 0.1. 0.7g / 25cm on the surface of each substrate²Spray (wet state). Then, after drying at room temperature, it was dried by heating (300 ° C × 1 hr) to obtain a photocatalyst.

【0027】

(Example 2) As an adsorption / photocatalyst functional material, amorphous titanium peroxide aqueous solution (0.84%): anatase type titanium oxide aqueous solution (0.84%): colloidal silica aqueous solution (0.84%): coconut shell activated carbon (converted to weight of other aqueous solution) Is mixed at a ratio of 3: 3: 0.1: 0.3 to 0.6 g / 25 cm on the surface of each substrate of Example 1.²Spray (wet state). Then, the whole was heated and dried (300 ° C × 1 hr) to obtain a photocatalyst.

【0028】

(Evaluation) When each of the above 14 types of photocatalysts is installed in a glass tube and irradiated with 300 nm ultraviolet light with a 300 W xenon lamp while the air containing 50 ppm of ethylene gas is in the environment, which photocatalyst is used? It was also confirmed that the ethylene gas concentration could be reduced to 5 ppm or less within 1 hour after light irradiation.

【0029】

FIG. 4 shows a photocatalyst device 9 in which a photocatalyst body 1 formed on a flat plate is fitted in a frame 7 and a fluorescent lamp 8 as an electromagnetic wave supply source of an excitation wavelength is integrally incorporated. The photocatalyst 1 is shown in Example 1, and the frame 7 is made of stainless steel and is formed in a rectangular shape. The frame material constituting the vertical frames on both sides provides a space for accommodating the fluorescent lamp 8. Therefore, when the frame 7 is viewed from above, it becomes a long rectangle corresponding to the cross-sectional shape, and the flat plate photocatalyst 1 is arranged along the diagonal line thereof. With this structure, one surface (front side) of the photocatalyst body 1 is irradiated by one fluorescent lamp 8 and the other surface (back surface) is irradiated by the other fluorescent lamp 8, and the photocatalyst functional layer on each surface is activated. .. The ultraviolet rays from the fluorescent lamp 8 irradiate the surface of the photocatalyst 1 from one side, but the surface of the photocatalyst 1 is reflected by the uneven surface of the metal non-woven fabric, and the ultraviolet rays also appear in the shadows when viewed from the fluorescent lamp side. Upon reaching it, the front surface of the photocatalyst functional layer on the surface of the photocatalyst is almost activated, and an efficient photocatalyst function is exhibited. Since this photocatalyst device 9 is breathable, it can be used not only as a filter but also as a partition that also serves as a room air purification device.

【0030】

FIG. 5 shows a cross section of the low temperature storage chamber 10 for storing vegetables and the like. The low temperature storage chamber 10 is sealed by a door (not shown), but the flat photocatalyst 1 shown in Example 1 is attached to the inside of the box-shaped outer wall 11 in the form of a lining with an interval of 12. ing. A flat reflector 13 and fluorescent lamps 8 as an ultraviolet source are arranged on both sides of the flat reflector 13 in a diagonal arrangement at a space 12 of the ceiling portion. As shown in FIG. 6A, the flat plate type reflector 13 has reflection pieces 14 formed on both sides and reflects ultraviolet rays from the fluorescent lamps 8 on both sides in the same direction, that is, in the direction of the photocatalyst 1 on the ceiling. When the photocatalyst functional layers are present on both sides of the panel like the central partition wall, the reflector 13 having the reflection layers 18 on both sides is used as shown in FIG. 6 (b). The reflective layer 18 is composed of, for example, a laminate of SUS particles baked on both sides of a stainless steel plate 19. The particles are densely arranged with a small diameter on the 19th side of the steel sheet and coarsely arranged with a large diameter on the side away from the substrate. An elliptical curved reflector 16 having a mirror surface on the inside and a fluorescent lamp 8 as an ultraviolet source are arranged inside the center of the reflector 16 at intervals 15 of the wall portions. The spaces 13 and 15 are connected to ducts 17 on both sides of the ceiling, and the internal air of the storage chamber 10 is circulated through the photocatalyst 1 which is an inner wall by a circulation pump. Then, organic compounds that are inconvenient for storing vegetables such as ether and odor floating in the air when passing through the photocatalyst 1 are decomposed by oxidation / reduction action. When the substrate 2 has moldability as in the embodiment, the photocatalyst 1 as the inner wall is not formed by combining flat plates, but can be formed into a container shape at once by press working. If peeling of the photocatalyst functional layer becomes a problem, the photocatalyst functional layer may be formed after the substrate 2 is pressed.

【0031】

FIG. 7 shows an example in which the photocatalyst 1 is used as a measure against deodorization of the toilet, and the photocatalyst 1 is attached to the ceiling as a flat plate at intervals. Reference numeral 8 is a fluorescent lamp, which is a source of ultraviolet rays. In the indoor space of a toilet, indoor air is normally flowing by a ventilation device at all times, and the suspended organic compound, which is the source of odor, collides with the photocatalyst 1 on the air flow and is decomposed by the photocatalyst functional layer. Since the surface of the photocatalyst 1 has an uneven laminated structure with voids, it is easily decomposed during contact with suspended organic compounds and passing through pores to easily receive a photocatalytic function, and the deodorizing effect is improved.

【0032】

[Effect of the invention]

According to the present invention, the photocatalyst body has many voids and irregularities on the surface layer portion, the area of the photocatalyst functional layer is large, the oxidizing / reducing power is large, and the contact opportunity between the organic compound floating in the fluid and the photocatalyst functional layer It is possible to obtain a photocatalyst with high performance.

[Simple explanation of drawings]

[Figure 1]

It is a top view of the photocatalyst body which concerns on one Example of this invention.

[Figure 2]

It is a schematic diagram which shows the appearance of a substrate.

[Fig. 3]

(a), (b), and (c) are all perspective views showing an example of a three-dimensional photocatalyst.

[Fig. 4]

It is a perspective view which showed the flat photocatalyst device.

[Fig. 5]

It is a front view which shows by cutting a low temperature storage.

[Fig. 6]

Both (a) and (b) are plan views showing an example of a reflector.

[Fig. 7]

It is a front view which shows typically the form of use in a toilet.

[Explanation of symbols]

1 photocatalyst, 2 substrate, 3 wire mesh, 4 porous layer, 5 photocatalyst functional layer