JP2000237538A - Photocatalytic air purifier - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a photocatalytic air purifier which reliably adsorbs an intermediate product on an adsorbent layer and prevents discharge to the outside even if the intermediate product having low adsorbability to a photocatalyst layer is produced by making a light source opposite to the photocatalyst layer in a ventilation pass and disposing the adsorbent layer on the downstream side of the photocatalyst layer and the light source. SOLUTION: In the photocatalytic air purifier 1, external air sucked from a suction opening 4 by a blower fan 3 in a ventilation pass 2 is spouted from a nozzle 5. A fiber filter 6, the blower fan 3, a light source 7 which excites a photocatalyst, a photocatalyst layer 8 and an adsorbent layer 9 are successively disposed in the ventilation pass 2 from the upper stream side. The light source 7 is made opposite to the photocatalyst layer 8 and the adsorbent layer 9 is disposed in close contact with the photocatalyst layer 8 on the downstream side. Organic substances such as malodorous components adsorbed on the photocatalyst layer 8 are subjected to oxidation decomposition by irradiation with excitation light from the light source 7. Even if an intermediate product having low adsorbability to the photocatalyst layer 8 is produced, it can reliably be adsorbed on the adsorbent layer 9.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an air purifying apparatus using a photocatalyst for purifying odors and harmful substances generated in homes and offices.

[0002]

2. Description of the Related Art Conventionally, as an air purifying apparatus using a photocatalyst, there is known an air purifying apparatus having a structure in which an activated carbon layer is provided on the windward side of a photocatalyst layer as disclosed in Japanese Patent Application Laid-Open No. 1-159032. ing. This air purifying device is provided with a photocatalyst layer at the most leeward side in a ventilation path, and releases odorless air by decomposing odor components and the like.

[0003]

However, since the photocatalytic action generally has a slower reaction than the adsorbing action of an adsorbent such as activated carbon, the air purifying apparatus of the above construction completely decomposes odorous components and harmful components. In some cases, the light may pass through the photocatalyst layer before being emitted and be emitted to the outside as it is. In particular, when an intermediate product having poor adsorption ability to the photocatalyst layer is generated in the decomposition process due to photocatalytic activity, most of the intermediate product then passes through the photocatalyst layer without being decomposed, and as a new odor component or harmful substance There was a problem that the intermediate product was released to the outside.

[0004] Explaining with specific examples, when ammonia is decomposed by photocatalytic activity, nitric oxide and nitrogen dioxide are generated as intermediate products in the decomposition process. Nitrogen monoxide has a high adsorption ability to the photocatalyst layer and is further decomposed by the photocatalyst, but nitrogen dioxide has a low adsorption ability to the photocatalyst layer and passes through the photocatalyst layer as it is and is released to the outside There is a risk.

As a solution to such a problem, there is known a deodorizing apparatus disclosed in Japanese Patent No. 2574840 in which a photocatalyst is added to an adsorbent. This is because the photocatalyst is added to the surface of the adsorbent, or the photocatalyst is kneaded into the adsorbent, so that the odor component with a slow decomposition rate is once adsorbed on the adsorbent with excellent adsorption capacity,
It is intended to gradually decompose odor components in the adsorbent by the action of a photocatalyst.

However, the following problems occur in the deodorizing device having the above-mentioned structure. That is, in a conventional air purification device, a substance having a relatively small polarity and a high boiling point is adsorbed by an adsorbent, and a substance having a large polarity and a low boiling point is decomposed by a photocatalyst. Therefore, the air can be completely purified only when both functions sufficiently.

However, as in the deodorizing apparatus having the above structure,
In the state where the photocatalyst is added, the original adsorption capacity of the adsorbent is reduced, and as a result, the time required for air purification becomes longer. Furthermore, photocatalysts can be used semi-permanently by nature, but as for adsorbents, all of the adsorbed odor components etc. are not decomposed by the photocatalyst, so that the adsorption capacity is not reduced with use. I can't.

At this time, it is necessary to replace the adsorbent, but in that case, it is necessary to replace the photocatalyst which is still in a sufficiently usable state, which causes a problem that the cost increases.

Therefore, an object of the present invention is to provide an air purifying device that can solve the above-mentioned problems.

[0010]

To achieve the above object, a photocatalyst air purification apparatus according to the present invention includes an adsorbent layer and a light source for exciting the photocatalyst layer and the photocatalyst in a ventilation path. The light source is provided to face the photocatalyst layer, and the adsorbent layer is provided on the downwind side of the photocatalyst layer and the light source.

By employing such a configuration, by irradiating the photocatalyst layer with excitation light from a light source, the organic odor components adsorbed on the photocatalyst layer and harmful substances such as nitrogen oxides and sulfur oxides are reduced by the photocatalytic activity. Decomposed.

Further, even if an intermediate product having poor adsorption ability to the photocatalyst layer is generated in the decomposition process, the intermediate product is adsorbed by the adsorbent layer disposed on the leeward side of the photocatalyst layer. The release of intermediate products to the outside can be prevented. In the case of nitrogen dioxide generated during the above-mentioned decomposition of ammonia, for example, by selecting an adsorbent having a high ability to adsorb nitrogen dioxide, such as activated carbon, it is possible to suppress release to the outside.

The adsorbent layer may be installed at any position on the leeward side of the photocatalyst layer and the light source.
If the adsorbent layer is brought into close contact with the photocatalyst layer, the intermediate product adsorbed on the adsorbent layer at the interface between the two layers can be gradually decomposed by the photocatalyst.

Further, if the adsorbent can be removed alone, when the adsorption capacity of the adsorbent layer is reduced, the purifying ability of the air purifying device can be restored only by replacing the adsorbent layer alone.

In addition, if the adsorbent is present in the photocatalyst layer separately from the adsorbent layer and only the adsorbent can be taken out when the adsorption capacity is reduced, the intermediate product can be adsorbed on the adsorbent once. After that, it can be efficiently decomposed by the photocatalyst. Moreover, since only the adsorbent can be replaced, it is advantageous in terms of cost.

Specifically, when the photocatalyst layer is formed in a honeycomb shape, the honeycomb is filled with an appropriate amount of an adsorbent such as granular or fiber-like activated carbon, or the photocatalyst layer is formed in a mesh or sheet shape. At this time, it is possible to adopt a configuration in which an adsorbent formed in a nonwoven fabric shape or a sheet shape is overlapped.

In the air purifying apparatus having the above structure, if external air is directly introduced into the photocatalyst layer, dust or fume may adhere to the surface of the photocatalyst and adversely affect the decomposition performance of the photocatalyst.

Therefore, in the present invention, it is possible to adopt a configuration in which a dust collecting portion for collecting dusts and fumes on the order of submicron is provided on the windward side of the photocatalyst layer and the light source. With such a configuration, it is possible to prevent the decomposition ability of the photocatalyst from decreasing. In addition, as the dust collecting portion, a fiber filter made of ultrafine fibers of several microns or an electric dust collecting device can be used.

The photocatalyst refers to a substance that functions as a catalyst for a chemical reaction by absorbing light. When the photocatalyst surface is irradiated with light, electrons are excited from the conduction band and charge separation into holes and electrons occurs. By causing an oxidation-reduction reaction by electron transfer on this surface, odor components and toxic components can be decomposed and deodorized and made harmless.

As the photocatalyst, it is generally preferable to use titanium oxide having high activity, but other metal oxides such as tungsten oxide, zinc oxide and copper oxide can also be used. In addition, these metal oxides may be used alone or a composite thereof.

However, even if the photocatalyst composed of a metal oxide is irradiated with light to generate holes and electrons, most of the holes and electrons recombine, so that a high photocatalytic activity cannot be obtained, and the decomposition rate is low. Slow substances, reaction by-products or intermediate products generated by the photocatalytic action may adhere to the surface of the photocatalyst, which may cause a decrease in photocatalytic activity.

Therefore, in the present invention, a photocatalyst having a structure in which metal fine particles are supported on the surface of a metal oxide simple substance or a composite thereof can be adopted. Examples of the metal fine particles used here include platinum and palladium particles having a particle size of 1 to 10 nm.

When such a configuration is adopted, electrons generated by light irradiation are attracted to the metal fine particles and recombination with holes is prevented, so that high photocatalytic activity can be obtained, and the decomposition rate can be increased. Slow substances, reaction by-products or intermediate products are quickly decomposed and removed, and a decrease in photocatalytic activity can be prevented.

As the adsorbent in the present invention, zeolite, mizcanite, mordenite, porous silica, porous alumina, sepiolite, molecular sieve, cordierite, activated carbon, metal ion-exchanged zeolite or a complex thereof can be used. Can be.

The shapes of the photocatalyst layer and the adsorbent layer are not particularly limited, but among them, a honeycomb shape, a nonwoven fabric shape or a bellows shape is preferable.
This is because the surface areas of the photocatalyst layer and the adsorbent layer increase, and the adsorption performance and the photocatalytic activity increase.

[0026]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view showing an embodiment of a photocatalyst air purification device according to the present invention. In this photocatalytic air purification device 1, a ventilation passage 2 is formed in the device, and the ventilation passage 2
The external air taken in from the suction port 4 by the blower fan 3 installed in the inside is discharged from the outlet 5. In the ventilation path 2, a fiber filter 6, a blower fan 3, a light source 7 for exciting the photocatalyst, a honeycomb-shaped photocatalyst layer 8, and an adsorbent layer 9 are arranged in this order from the windward side.

The light source 7 faces the photocatalyst layer 8 and the adsorbent layer 9
Is installed on the leeward side in a state of being in close contact with the photocatalyst layer 8. External air containing odorous components and harmful components enters through the inlet 4 and passes through the fiber filter 6 to collect dust and fumes in the air. Odorous components such as tobacco odor, toilet odor, pet odor and cooking odor, and harmful substances such as building material odor and exhaust gas are removed.

Further, by passing through the adsorbent layer 9, odor components, harmful substances and the like that could not be completely removed by the photocatalyst layer 8 are removed, and purified air is discharged from the outlet 5 to the outside. The organic substances such as odor components adsorbed on the photocatalyst layer 8 are oxidized and decomposed by a photocatalyst activated by irradiation with excitation light from the light source 7 and released to the outside as water molecules and carbon dioxide.

At this time, even if an intermediate product having a low adsorption ability to the photocatalyst layer 8 is generated in the decomposition process due to the photocatalytic activity, the intermediate product is adsorbed by the adsorbent layer 9 and thus is not released to the outside. Can be prevented.

The photocatalyst layer 8 and the adsorbent layer 9 in the present embodiment were produced by the following method.

(Preparation of Photocatalyst Layer) A coating solution was prepared using titanium oxide powder (ST-01, manufactured by Ishihara Techno Co., Ltd.) as a photocatalyst, and colloidal silica (Betak 970, manufactured by Telnic Industries, Ltd.) as a binder. Prepared. The coating solution was prepared such that the weight ratio of titanium oxide to colloidal silica in the solid content was 1: 1.

The coating solution thus prepared was added with 200
Cell / inch ² aluminum honeycomb substrate (30
0 × 90 × t 18 mm) and immersed in 1 l
00 g of solid content (in the present embodiment, the solid content is 49
g) was carried on the substrate surface. Thereafter, a heat treatment was performed at 150 ° C. for 1 hour to produce a photocatalyst layer 8.

(Preparation of Adsorbent Layer) Coating solution using activated carbon powder (woody activated carbon powder, manufactured by Cataler Co., Ltd.) as an adsorbent and colloidal silica (Betac 970, manufactured by Telnic Industries, Ltd.) as a binder Was prepared. The coating solution was prepared such that the weight ratio of activated carbon to colloidal silica in the solid content was 1: 1.

[0034] The coating solution thus prepared was added with 200
Cell / inch ² aluminum honeycomb substrate (30
0 × 90 × t 18 mm) and immersed in 1 l
00 g of solid content (in the present embodiment, the solid content is 49
g) was carried on the substrate surface. Thereafter, heat treatment was performed at 150 ° C. for 1 hour to produce the adsorbent layer 9.

FIG. 2 is a sectional view showing a second embodiment of the photocatalytic air purifying apparatus according to the present invention. This photocatalyst air purification device 1 has the same basic configuration as the photocatalyst air purification device 1 in the first embodiment, except that the photocatalyst layer 8 is provided at two locations on the windward and downstream sides of the light source 7. And that the blower fan 3 is installed at the most leeward side.

That is, the photocatalyst air purifying apparatus 1 according to the present embodiment includes the fiber filter 6, the photocatalyst layer 8, the light source 7, the photocatalyst layer 8, the adsorbent layer 9, The blower fans 3 are arranged in this order.

With such a configuration, a higher catalytic action can be obtained than when the thickness of the photocatalyst layer 8 is simply doubled. That is, when the thickness of the photocatalyst layer 8 is doubled, the amount of light to be irradiated is reduced at the end of the photocatalyst layer 8 so that the catalytic action is weakened. Since the amount of light does not decrease, the photocatalytic ability can be doubled. Therefore, the photocatalyst air purification device 1 having a simple structure and high processing ability can be obtained with one light source 7 alone.

FIG. 3 is a sectional view showing another embodiment of the adsorbent layer. The adsorbent layer 9 is formed by sandwiching granular activated carbon between two air-permeable sheets to form a thick sheet and then bending it into bellows. When this is used in combination with the honeycomb-shaped photocatalyst layer 8, a simple sheet-shaped photocatalyst layer 8 and an adsorbent layer 9 are formed.
Since the surface area is larger than that of, the photocatalytic activity of the photocatalyst and the adsorption performance of the adsorbent can be improved.

[0039]

As is apparent from the above description, according to the present invention, since the adsorbent layer is provided on the downwind side of the photocatalyst layer and the light source, the adsorption ability to the photocatalyst layer in the decomposition process by photocatalytic activity is poor. Even when an intermediate product is generated, the intermediate product is adsorbed by the adsorbent layer, so that the release of the intermediate product to the outside can be prevented.

Further, by adhering the adsorbent layer to the photocatalyst layer, the intermediate product adsorbed on the adsorbent layer at the interface between the two layers can be gradually decomposed by the photocatalyst.

If the adsorbent layer can be removed alone, when the adsorption capacity of the adsorbent layer is reduced, the purifying ability of the apparatus can be restored only by replacing the adsorbent layer alone.

If the adsorbent is present in the photocatalyst layer separately from the adsorbent layer and only the adsorbent can be taken out when the adsorbing capacity is reduced, the intermediate product is adsorbed on the adsorbent, It can be efficiently decomposed by the photocatalyst.

Further, if a dust collecting portion for collecting submicron-order dust and fumes is provided on the windward side of the photocatalyst layer and the light source, it is possible to prevent the decomposition ability of the photocatalyst from being lowered.

When a metal fine particle carrier having metal fine particles supported on the surface of a single metal oxide or a composite thereof is used, the photocatalytic activity can be enhanced, and a substance which has a low decomposition rate or is produced by a photocatalytic action. Even if the reaction by-products or intermediate products adhere to the surface of the photocatalyst, they are quickly decomposed and removed, thereby preventing a decrease in photocatalytic ability.

Further, when the photocatalyst layer and the adsorbent layer are formed in a honeycomb shape, a nonwoven fabric shape, a sheet shape or a bellows shape, the surface area of the photocatalyst layer and the adsorbent layer increases, and the adsorption performance and the photocatalytic activity increase.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of a photocatalytic air purification device according to the present invention.

FIG. 2 is a cross-sectional view showing a second embodiment of the photocatalytic air purification device according to the present invention.

FIG. 3 is a sectional view showing another embodiment of the adsorbent.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Photocatalyst air purification apparatus 2 Ventilation path 3 Ventilation fan 4 Inlet 5 Outlet 6 Fiber filter 7 Light source 8 Photocatalyst layer 9 Adsorbent layer

Continued on front page F-term (reference) 4D002 AA12 AB02 BA04 BA14 CA07 DA41 DA45 DA46 DA47 EA02 EA13 HA01 4D012 CA09 CA15 CB02 CD10 CG01 CH05 CJ10 CK07 4D048 AA22 AB01 AB03 BA03Y BA05X BA06X BA07X BA11Y BA16Y BA27XBB35 CC02 CD05 EA01 EA04 4D058 JA12 JB25 TA02 TA06 TA07 UA25

Claims (9)

[Claims] 1. An adsorbent layer, a photocatalyst layer, and
A photocatalyst air purification device comprising: a light source for exciting a photocatalyst in the photocatalyst layer; the light source provided to face the photocatalyst layer; and the adsorbent layer provided downstream of the photocatalyst layer and the light source. 2. The photocatalyst air purification device according to claim 1, wherein the adsorbent layer is brought into close contact with the photocatalyst layer. 3. The method according to claim 1, wherein the adsorbent layer is removable.
Or the photocatalytic air purification device according to 2. 4. The photocatalytic air purification device according to claim 1, wherein a dust collecting portion for collecting submicron-order dust and fumes is provided on the windward side of the photocatalyst layer and the light source. . 5. The photocatalyst air purification device according to claim 1, wherein the photocatalyst layer and the adsorbent layer have a honeycomb shape, a nonwoven fabric shape, or a bellows shape. 6. The photocatalyst air purification device according to claim 1, wherein an adsorbent is present in the photocatalyst layer, and the adsorbent can be separated and taken out from the photocatalyst layer. 7. The photocatalyst air purification device according to claim 1, wherein the photocatalyst is a simple substance of a metal oxide such as titanium oxide, tungsten oxide, zinc oxide, copper oxide or a composite thereof. . 8. The photocatalyst comprises a metal fine particle carrier in which metal fine particles are supported on the surface of a single metal oxide such as titanium oxide, tungsten oxide, zinc oxide, copper oxide or a composite thereof. 7. The photocatalyst air purification device according to 3, 4, 5, or 6. 9. The method according to claim 1, wherein the adsorbent comprises a simple substance of zeolite, mizcanite, mordenite, porous silica, porous alumina, sepiolite, molecular sieve, cordierite, activated carbon and metal ion exchanged zeolite, or a composite thereof. The photocatalytic air purification device according to 3, 4, 5, 6, 7, or 8.