JP2003305341A - Photocatalytic filter medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a photocatalytic filter medium having excellent mechanical strengths with which optical energy is effectively used while causing an improvement in gas treatment capacity. <P>SOLUTION: This photocatalytic filter medium fixes a photocatalytic structure of a photocatalyst carried by a carrier having UV transmissivity to at least one face of a metal network body. The photocatalytic filter medium uses the photocatalytic structure having as the carrier silica sand or the like which is excellent in optical transmissivity in the wavelength range of 240-420 nm of various optical sources to be used for photocatalytic excitation, thus effective use of optical energy is made possible and gas treatment capacity is improved. Since the photocatalytic structure is fixed to the metal network body, UV light is directly irradiated to the photocatalytic structure, thus the loss of the optical energy is reduced and the gas treatment capacity is increased, further, the mechanical strengths of the filter are improved. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a photocatalytic material. More specifically, it relates to a photocatalytic filter material that is preferably used for air cleaning, exhaust gas treatment, and the like.

[0002]

2. Description of the Related Art Environmental problems such as water quality, air, and soil pollution have been emphasized year after year, and adversely affect human-made chemical substances, especially pollutants such as organic solvents, pesticides, and surfactants. Removal of viruses and bacteria is strongly desired.
The method of decomposing these chemical substances with a photocatalyst typified by titanium oxide is a clean method because no chemicals are used, and light energy such as sunlight can be used. It is a purification method.

As for the gas phase treatment filter, a honeycomb substrate having a photocatalyst carried thereon (Japanese Patent Laid-Open Nos. 2000-325724 and 2000-343936) and a photocatalytic material filled between two non-woven fabrics are also used. (2000-233113 publication), fibrous filter made of metal oxide (2000-225349 publication, 2000 publication)
-126551 gazette, 2000-157876 gazette) has been proposed, but the ultraviolet rays necessary for activation of the photocatalyst are blocked by the base material such as the nonwoven fabric and the photocatalyst carrier, or the strength of the filter is insufficient. There are problems such as being present.

In order to solve such a problem, it has been proposed to attach an adsorbent carrying a photocatalyst to a non-woven fabric or a net-like base material (Japanese Patent Laid-Open No. 2001-29441). However, in this case, an adsorbent having a low light-transmitting property such as activated carbon, zeolite, ceviolite, or silica gel is used as the adsorbent carrying the photocatalyst, and the light-transmitting property of the photocatalyst becomes low, so that the utilization of light energy There is a problem of reduced efficiency. Further, as a carrier for the photocatalyst,
Fluorine resin or quartz (2000-51334 publication),
Those using ceramics and the like (2000-24514, JP-A-11-156377, JP-11-128631) are also known, but there is a decrease in processing capacity due to insufficient optical transparency of the carrier itself. There is a problem that the carrier itself is expensive.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a photocatalyst material which enables effective utilization of light energy, improves gas treatment performance, and is excellent in mechanical strength.

[0006]

The object of the present invention is as follows.
This is achieved by a photocatalyst material in which a photocatalyst structure composed of a photocatalyst supported on a carrier having ultraviolet transparency is immobilized on at least one surface side of a metal net.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION As a carrier having ultraviolet transparency, it has light transparency in a wavelength region longer than 210 nm and is excellent in light transparency at a main emission wavelength of 240 to 420 nm of a photocatalytic excitation light source. Used, preferably silica sand. Quartz sand is a low-cost industrial raw material that is almost exclusively composed of fine quartz particles and has a very high SiO ₂ content. In the present invention, those having an average particle size of about 0.05 to 5 mm, preferably about 0.1 to 2 mm are used from the viewpoints of easy availability and immobilization on a metal mesh.

As the photocatalyst supported on the silica sand, any photocatalyst having photocatalytic activity can be used, but titanium oxide is generally used.
The crystal structure of titanium oxide includes anatase type, rutile type, and brookite type. When the crystallization temperature is low, anatase type titanium oxide is formed, and when it is high, rutile type titanium oxide is formed. Among these, anatase-type titanium oxide having a crystal structure enhanced to the extent that the crystal structure does not transfer to the rutile type has particularly high catalytic activity. On the other hand, regarding rutile type titanium oxide, even in the photocatalyst formed as a coating layer, it is disclosed that the activity is reduced (Japanese Patent Laid-Open No. 11-157966), but when used with anatase type titanium oxide. Has even higher catalytic activity than when used alone with anatase type titanium oxide.

Therefore, as the titanium oxide, anatase-type titanium oxide, rutile-type titanium oxide, or those obtained by adding a metal element such as zirconium or aluminum are used, preferably anatase-type titanium oxide, and more preferably rutile. Type titanium oxide and titanium oxide containing anatase type titanium oxide are used. Examples of titanium oxide containing rutile type titanium oxide and anatase type titanium oxide include rutile type titanium oxide.
Titanium oxide containing 20 to 99% by weight, preferably 30 to 88% by weight, and 80 to 1% by weight, preferably 70 to 12% by weight of anatase type titanium oxide is used. The contents of the rutile type and the anatase type are calculated from the X-ray diffraction intensity obtained by gelling and annealing the titania sol solution used for coating to obtain a powder. Further, it is also possible to use a metal such as silver, nickel, platinum, palladium or copper, which is suitable for the treatment of the substance to be treated, deposited on the photocatalyst surface to enhance the reaction efficiency.

The support of the photocatalyst on these carriers is preferably formed as a coating layer on the surface of the carrier. The coating layer is formed using a metal oxide film forming method such as a sol-gel method, a CVD method, a vacuum deposition method, or a sputtering method. When the thickness of the formed photocatalytic film is thinner than 0.03 μm,
The desired processing capacity of the substance to be treated cannot be obtained, while 1 μm
It is the same even if it is made thicker. Incidentally, the photocatalyst film to be formed, when only anatase type titanium oxide is obtained,
In order to increase the crystallinity thereof, it is annealed at 400 to 600 ° C., and in order to obtain a rutile type and anatase type titanium oxide, it is annealed at 650 to 800 ° C. for about 0.5 to 5 hours to obtain a desired crystalline state.

The thus formed photocatalyst structure comprising a photocatalyst supported on a carrier having ultraviolet transparency is fixed to one side or both sides of the metal net. As the metal forming the mesh body, any metal can be used as long as it has moisture resistance and ultraviolet resistance, and for example, stainless steel, aluminum alloy, copper alloy, etc. are used. As the shape of this metal net,
In addition to a planar shape, a corrugated shape or a pleated shape is also used in order to reduce the pressure loss and improve the gas treatment capacity by increasing the apparent surface area of the photocatalyst. The mesh size of the mesh is preferably not more than the average particle size of the ultraviolet-transparent carrier, and is generally about 0.05 to 5 mm, preferably about 0.1 to 2 mm.

For fixing the photocatalyst structure to the metal net, a general adhesive such as an epoxy resin adhesive is used, and water glass is preferably used. When water glass is used as the adhesive layer, a germicidal lamp can be used as a light source for photocatalyst excitation due to the light resistance of the adhesive layer, so that the germicidal effect can be improved. Further, generation of carbon dioxide due to photooxidation of the adhesive layer can be effectively prevented, and a decrease in adhesive strength of the adhesive layer can be suppressed. As a method for adhering, for example, a method in which a photocatalyst structure is sprinkled and adhered to a mesh-like body coated with an adhesive is used.

FIG. 1 schematically shows the adhesion state, in which a photocatalyst structure 3 composed of a photocatalyst 2 supported on silica sand 1 is adhered to a metal net-like body 5 having an adhesion layer 4,
It is integrated. The method of supporting the photocatalyst on silica sand is generally roughly classified into a liquid phase method and a gas phase method, and it is considered that the liquid phase method such as the sol-gel method makes it easier for the photocatalyst to adhere to the depressions on the surface of the silica sand. As shown in the figure, the photocatalyst partially adhered to the silica sand was confirmed by observation with an electron microscope, while it is unlikely that the gas phase method would cause a partial adherence. To be

In order to effectively utilize the irradiated light energy, it is important to immobilize the photocatalyst structure on the surface of the metal net-like body on the light irradiation side. Further, in order to effectively use the energy of the transmitted light of the photocatalyst structure and the light passing through the metal net-like body, it is also effective to immobilize the photocatalyst structure on the light irradiation back side of the metal net-like body. Since the photocatalyst material produced in this manner has a high light-transmitting property of the photocatalyst structure, it is possible to effectively utilize the light energy even on the light irradiation back surface of the photocatalyst structure and the light irradiation back surface of the photocatalyst material. it can.

The photocatalytic filter material can be used as a filter material in air cleaning and exhaust gas treatment in automobile air conditioning, and is effectively used not only in such gas phase treatment but also in liquid phase treatment such as water treatment. be able to.

[0016]

The photocatalyst material according to the present invention has the following effects. (1) The wavelength range of various light sources used for photocatalytic excitation is 24
It is 0 to 420 nm, and since it uses a photocatalyst structure that uses silica sand or the like having excellent light transmittance in such a wavelength region as a carrier, it is possible to effectively use light energy and to improve gas treatment performance. improves. (2) Since the photocatalyst structure is immobilized on the metal net, it is possible to directly irradiate the photocatalyst structure with ultraviolet rays,
Therefore, the loss of light energy is small and the gas treatment performance is improved. In addition, the mechanical strength of the second material is also improved. (3) When the photocatalyst structure is fixed to a metal net with water glass as an adhesive, a germicidal lamp can be used as a light source for photocatalyst excitation due to the light resistance of the adhesive layer made of a cured product of water glass. As a result, it is possible to improve the sterilization effect as well as the gas treatment performance. Further, generation of carbon dioxide due to photooxidation of the adhesive layer can be effectively prevented, and a decrease in adhesive strength of the adhesive layer can be suppressed.

[0017]

EXAMPLES The present invention will now be described with reference to examples.

Example 1 A solution of 16 g of titanium isopropoxide dissolved in 78 g of 2-methoxyethanol (ethylene glycol monomethyl ether) was mixed with a solution of 2 g of 1N hydrochloric acid dissolved in 48 g of 2-methoxyethanol for 4 hours. Stir-mixed to form a sol solution. This sol solution has a particle size of 0.69 mm (30 to 20 mesh)
No silica sand (Kanto chemical product) coated on the surface, dried, 500 ° C
After annealing for 1 hour in the air, a photocatalyst structure was obtained in which a coating layer of anatase type titanium oxide was formed on the surface of the silica sand carrier. The coating layer thickness was 0.04 μm.

This photocatalyst structure and one metal net (SU
Made of S316, single wire plain weave, warp open 0.36 mm, open weft 0.63 mm, porosity 39.7%) with epoxy resin adhesive (Sumitomo 3M DP-110 clear) The photocatalytic structure was immobilized on the surface side.

FIG. 2 shows an example of use of the photocatalyst material 10 thus obtained, in which the black light source 20 is installed so that the photocatalyst structure 3 is directly irradiated with light. There is. In this case, since there is only an air layer between the photocatalyst structure 3 and the black light source 20, the loss of light energy is small.

An acetaldehyde removal test was conducted on the photocatalyst material thus produced. While turning on the black light source and irradiating the photocatalyst material with ultraviolet rays (main emission wavelength 365 nm), acetaldehyde gas with a concentration of 1 ppm by air dilution is supplied to the upstream side (light source side) of the photocatalytic material and the downstream side. When the gas after the treatment (on the side of the photocatalytic filter material) was collected and the acetaldehyde concentration was measured by gas chromatography, the acetaldehyde reduction rate was 45.3%.

Example 2 In Example 1, water glass (sodium silicate aqueous solution; Kishida chemical product sodium silicate aqueous solution) was used as an adhesive.
A photocatalytic filter material 10 was produced by using No. 3) cured at 400 ° C. With respect to the obtained photocatalytic filter material, a germicidal lamp light source was turned on, and ultraviolet rays (main emission wavelength 254 nm) were irradiated in the same manner as in Example 1 to measure a reduction rate of acetaldehyde, which was 44.2%.

Further, while turning on the germicidal lamp light source and irradiating the photocatalyst material with ultraviolet rays (main emission wavelength 254 nm), acetaldehyde-free standard air (carbon dioxide concentration concentration
(Less than 0.1 ppm) is supplied to the upstream side (light source side) of the photocatalytic material,
The gas after treatment was collected on the downstream side (photocatalyst filter material side), and the carbon dioxide concentration was measured by gas chromatography to be 0.05 ppm or less, and generation of carbon dioxide due to photooxidation of the adhesive layer was not observed. .

Reference Example In Example 2, the acetaldehyde reduction rate and the carbon dioxide concentration were measured using an epoxy resin adhesive (DP-110 clear) instead of water glass as an adhesive. The results were 40.4% and 0.32, respectively. It was ppm, and it was confirmed that carbon dioxide was generated by photooxidation of the adhesive layer.

Comparative Example 1 The same photocatalyst structure 3 as in Example 1, two metal nets 5,
As shown in FIG. 3, the photocatalyst structure 3 was sandwiched between the metal mesh bodies 5 and 5 ′ by using the 5 ′ and the black light source 20. In this case, the photocatalyst structure 3 and the black light 20
Since the metal net-like body 5 is disposed between the metal net-like body 5 and, the light energy passing through the metal net-like body 5 is reduced.

When the acetaldehyde removal performance using the photocatalytic filter material thus produced was measured in the same manner as in Example 1, the acetaldehyde reduction rate was 27.2%.

Comparative Example 2 The same photocatalyst structure 3 as in Example 2, two metal mesh bodies 5,
As shown in FIG. 3, the photocatalyst structure 3 was sandwiched between the metal mesh bodies 5 and 5 ′ by using 5 ′ and the germicidal lamp light source 20.
In this case, since the metal net 5 is arranged between the photocatalyst structure 3 and the germicidal lamp light source 20, the light energy passing through the metal net 5 is reduced.

When the acetaldehyde removal performance using the photocatalytic filter material thus produced was measured in the same manner as in Example 2, the acetaldehyde reduction rate was 20.8%.

[Brief description of drawings]

FIG. 1 is a view schematically showing a photocatalytic filter material according to the present invention.

FIG. 2 is a view schematically showing a phototreatment method using the photocatalytic filter material of the example.

FIG. 3 is a diagram schematically showing a phototreatment method using a photocatalytic filter material of a comparative example.

[Explanation of symbols]

1 silica sand 2 Photocatalyst 3 Photocatalyst structure 4 Adhesive layer 5,5 'metal net 10 Photocatalyst material 20 light sources

Front page continuation (51) Int.Cl. ⁷ Identification code FI theme code (reference) B01J 32/00 B01J 35/02 J 35/02 35/06 C 35/06 37/02 301R 37/02 301 B01D 53 / 36 ZABJ (72) Inventor Masaaki Kanamori 25, Wadai, Tsukuba, Ibaraki Pref.NOK Co., Ltd. (72) Ryuji Kojima 25, Wadai, Tsukuba, Ibaraki F.O.F Co., Ltd. 4C080 AA07 BB02 CC01 HH09 JJ03 KK08 LL01 MM02 NN01 QQ03 4D019 AA01 BA02 BA18 BB02 BC07 CB04 CB06 4D048 AA19 BA06X BA07X BA39X BA41X BB01 BB08 BB17 CC40 EA01 4G069 AA03 AA08 BA02A BA02B BA04B BA15C BA48A BC14C CA01 CA02 CA03 CA11 DA06 EA02X EA02Y EA13 EB12X EB12Y EB15Y EB18X EB18Y EC22Y ED10 FA01 FA04 FB08 FB71 FC05

Claims (7)

[Claims] 1. A photocatalytic filter material comprising a photocatalyst structure comprising a photocatalyst supported on a carrier having ultraviolet transparency, which is immobilized on at least one surface side of a metal net-like body. 2. The photocatalytic filter material according to claim 1, which is fixed with an adhesive. 3. The photocatalytic filter material according to claim 2, wherein the adhesive is water glass. 4. The photocatalytic filter material according to claim 1, wherein a metal reticulate body having a mesh having an average particle size of the ultraviolet transparent carrier or less is used. 5. The photocatalytic filter material according to claim 1, wherein the carrier having ultraviolet transparency is silica sand. 6. The photocatalytic filter material according to claim 5, wherein silica sand having a particle size of 0.05 to 5 mm is used. 7. A light irradiation treatment method, which comprises irradiating light with the photocatalyst structure side of the photocatalytic material of claim 1 facing a light source.