JPH0442057B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to a method and a deodorizing device for deodorizing odors generated in homes, offices, etc., such as toilet odors, pet odors, cigarette odors, cooking odors, and body odors. Conventional technology The components of bad odors such as cigarette odor, toilet odor, pet odor, cooking odor, and body odor that occur in homes and offices include ammonia, amines, indole,
Contains nitrogen compounds such as skatole, hydrogen sulfide, sulfur compounds such as methyl mercaptan, methyl sulfide, and methyl disulfide, aldehydes, ketones, alcohols, fatty acids, and aromatic compounds.
There are a wide variety of components ranging from low boiling point components to high boiling point components. Methods for deodorizing these bad odors include pouring a chemical into the source and causing a chemical reaction, masking with an aromatic agent, adsorbing with activated carbon or zeolite, and concentrating the bad odor on an adsorbent impregnated with the chemical and causing a reaction. There is a way to do it. The former two methods can be used only in places such as toilets and places where pets are present, but the latter two methods can be used in any place. A typical example of a deodorizing device applying the latter two methods is shown in FIG. In the figure, 21 is a casing, in which a pre-filter 23 for collecting dust, an activated carbon layer 24, and a blower 27 are disposed in order from the windward side. The casing 21 is provided with a suction grill 22 on the windward side of the prefilter 23 and an outlet grill 20 on the leeward side of the blower 27. Since the deodorizing device with the above configuration uses activated carbon as a deodorizing agent, high boiling point compounds can be deodorized by physical adsorption, but low boiling point nitrogen compounds such as ammonia and methylamine, formalin, acetaldehyde, etc.
The deodorizing performance for low-boiling compounds such as low-boiling aldehydes such as acrolein was poor.
To solve this problem, deodorizers have come into use in which chemicals are impregnated with activated carbon and adsorbed through reaction with the chemicals. Problems to be Solved by the Invention However, in the chemically impregnated carbon described above, the high boiling point compounds are physically adsorbed on the activated carbon itself, so although it is possible to regenerate the activated carbon by heating, it is possible to regenerate the activated carbon by heating. Since nitrogen compounds and low-boiling aldehydes are adsorbed by reaction with impregnated chemicals, it has been difficult to regenerate the chemicals as adsorbents. Therefore, the lifespan of this chemically impregnated coal is short, from several months to half a year, and it is inconvenient that it must be replaced frequently. Additionally, activated carbon has the problem that once its physical adsorption capacity is saturated, it will emit bad odors when clean air comes in. It is an object of the present invention to solve the above-mentioned conventional problems and provide a deodorizing method and a deodorizing device that reduce maintenance and do not re-emit odors. Means for Solving the Problems In order to solve the above problems, light having a wavelength of 300 nm or more and a maximum wavelength of 370 nm or less is applied to the tungsten oxide in the coexistence of tungsten oxide, an oxidizable compound, and a gas containing oxygen. A deodorizing method using photocatalyst irradiation is provided. Further, by supporting a conductive inorganic substance on tungsten oxide, a deodorizing method with even better deodorizing performance is provided. Effect The present inventors have been researching the decomposition and deodorization of bad odors through photocatalytic action, and found that tungsten oxide has a maximum wavelength of 370 nm or less (energy
When irradiated with ultraviolet light (3.35eV or higher), in the coexistence of oxygen, the odor of ammonia, nitrogen compounds of amines, hydrogen sulfide, sulfur compounds of mercaptans, aldehydes, ketones, alcohols, fatty acids, aromatic compounds, etc. It was discovered that the causative substance can be effectively decomposed into oxides and odorless. especially
Even extremely low concentrations of oxidizable compounds, below 1 ppm, can be efficiently oxidized and decomposed to make them odorless. The working principle of tungsten oxide is currently under detailed research, but electrons in the valence band in the n-type semiconductor of tungsten oxide absorb ultraviolet light and are excited to the conduction band, and holes in the valence band are generated there. reacts with the hydroxyl group (OH group) on the surface of the catalyst, and the electrons excited in the conduction band react with oxygen (O) to generate highly active OH radicals, O radicals, and O ₂ ^- .
It is presumed that this oxidatively decomposes the oxidizable compound. Furthermore, when a conductive inorganic substance such as platinum, palladium, rhodium, ruthenium oxide, or silver is supported on this tungsten oxide, the oxidative decomposition effect becomes even stronger. Among them, the effect of platinum is remarkable. Examples Next, the deodorizing method of the present invention will be explained with reference to the drawings. FIG. 1 shows an embodiment of a deodorizing apparatus to which the photocatalytic deodorizing method of the present invention is applied. 1 is Keishin,
Inside, in order from the windward side, there is a prefilter 3, a reaction member 5 with a photocatalyst layer 4 formed on its surface, and a photocatalyst layer 4.
It has an electric lamp 7 that emits ultraviolet rays, which is placed so as to face the lamp, a reflector plate 8 which is installed on the rear surface of the electric lamp 7 so as to use the ultraviolet rays efficiently, and a blower 6.
The casing 1 is provided with a suction grill 2 on the windward side of the prefilter 3 and an outlet grill 9 on the leeward side of the blower 6. In order to widen the area of the photocatalyst layer 4 and improve contact with odor, the reaction member 5 has perforated fins 5d erected obliquely or at right angles to the flow of wind. The photocatalyst layer 4 is made of tungsten oxide. The photocatalyst layer 4 is made of a 0.5 mm thick alumina-silica ceramic paper impregnated with ammonium metatungstate and heated at 400°C to 700°C.
It is made by supporting tungsten oxide using methods such as heat treatment at ℃. This ceramic paper is then attached to a base material such as aluminum using an adhesive such as water glass to form a reaction member 5. Tungsten oxide is preferably tungsten trioxide (WO ₃ ), but
W ₄ O ₁₁ obtained by reducing this substance may also be used. In addition, when platinum is supported on tungsten oxide as a conductive inorganic substance, ceramic paper coated with tungsten oxide is impregnated with an ethanol solution of chloroplatinic acid, heat-treated at 400°C to 650°C, and supported as fine platinum particles. As an electric light 7, the wavelength is 300 nm or more and the maximum wavelength is
It is best to use one that can emit light of 370 nm or less. The energy for exciting electrons in tungsten oxide is 2.8 eV (440 nm), but if the maximum wavelength of the electric lamp 7 exceeds 370 nm, the electrons in tungsten oxide are not excited efficiently and the deodorizing effect is weak. on the other hand
Ultraviolet light with a wavelength of less than 300 nm does not pass through anything except quartz, which is expensive and difficult to process, and some hard glasses.
Electric lamps that emit light below 300 nm are expensive. Also
Ultraviolet light of less than 300 nm also excites electrons in tungsten oxide, but about 30% of the energy of the ultraviolet light is lost. Therefore, it occurs in electric light.
It is cheaper to use electric lamps that emit ultraviolet rays of 300 nm or more, which convert ultraviolet rays of less than 300 nm into longer wavelengths using phosphors coated on soft glass. Furthermore, while light with a wavelength of less than 300 nm has a strong bactericidal effect, it is harmful to the eyes.
It is dangerous because it causes great damage to the skin. Electric lights that can be used here include low-pressure mercury lamps, high-pressure mercury lamps, ultra-high-pressure mercury lamps, and xenon lamps. For example, low-pressure mercury lamps include black light blue fluorescent lamps (300 to 420 nm, maximum wavelength
352nm), blacklight fluorescent lamp (320-440nm,
Maximum wavelength 360nm), fluorescent lamp for insect trapping (300-480nm,
Maximum wavelength 370nm), fluorescent light for copying (300-490nm,
The maximum wavelength is 370 nm), and black light high-pressure mercury lamps (365 to 366.3 nm) are examples of high-pressure mercury lamps.
These electric lights may be used alone or in combination. In the above configuration, when the electric light 7 is turned on and the blower 6 is operated, air containing oxidizable compounds, that is, bad odor, is sucked in through the suction grille 2. Then, the prefilter 3 first collects dust. Subsequently, the photocatalytic layer 4 excited by ultraviolet rays removes oxidizable compounds such as ammonia, nitrogen compounds of amines, hydrogen sulfide, sulfur compounds of mercaptans, aldehydes, ketones, etc. Alcohols, fatty acids, and aromatic compounds are oxidatively decomposed into carbon dioxide, water, nitrogen oxides, sulfur oxides, etc. The deodorized air is then blown out from the blow-off grille 9. The decomposition products obtained by the above actions are usually ppb
The concentration is on the order of a minute, so there is no need to remove it. Next, specific examples will be shown. The metal oxides shown in Table 1 were prepared by the method described above, and the photocatalyst layer 4 was
And so. The area of the photocatalyst layer 4 is approximately 0.45 m ² , and the electric light 7 has two parallel lights with a power consumption of 15 watts (ultraviolet output
A fluorescent light for copying (2.1 watts, wavelength 300 to 490 nm, dominant wavelength 370 nm) was used, and the air volume of the blower 6 was 2 m ³ /min. Further, the distance between the two fluorescent lamps was 12 cm, and the distance between the fluorescent lamp and the photocatalyst layer 4 was 6 cm. Next, the deodorizing device was placed in an aluminum box with an internal volume of 1 m ³ . Then, put approximately 1% of each of trimethylamine, methyl mercaptan, and acetaldehyde into the box, and operate only the blower 6 of the deodorizing device to adsorb the gases on the catalyst layer 4. When the adsorption is saturated, Adjust to the specified initial concentration. Then, the electric light 7 of the deodorizing device is turned on, and the change over time in the gas concentration inside the 1 m ³ box is measured. Gas concentration was measured using gas chromatography. The results are shown in Table 1 and Figures 2 to 4. When two germicidal lamps with a power consumption of 15 cut (ultraviolet output 3.2 W, wavelength 253.7 nm) are used as electric lights 7 in parallel, metal oxidation occurs on the photocatalyst layer 4. A comparison is shown when only a fluorescent lamp for copying is used without any objects attached.

【table】

[Table] Effects of the invention As shown in Table 1 and Figures 2 to 4, when tungsten oxide or a catalyst in which platinum is supported on tungsten oxide is irradiated with light having a wavelength of 300 nm or more and a maximum wavelength of 370 nm, the wavelength of light of 253.7 nm or more is irradiated. It can decompose malodorous substances such as trimethylamine, methyl mercaptan, and acetaldehyde at a rate that is not much different from irradiation with germicidal radiation. Furthermore, even when irradiated with a black light blue fluorescent lamp with a maximum wavelength of 352 nm or a black light fluorescent lamp with a maximum wavelength of 360 nm, the same effect as in the case of the copying fluorescent lamp was confirmed. Furthermore, according to the present invention, not only the above substances but also other malodorous substances such as ammonia, hydrogen sulfide, ketones, alcohols, fatty acids, and aromatic compounds can be oxidized and made odorless. As described above, according to the deodorizing method using a photocatalyst of the present invention, the oxidative decomposition effect works until the concentration is so low that it no longer smells, so there is no re-release of odor, and it has a long life and can significantly reduce maintenance. Furthermore, since it uses electric light with a wavelength of 300 nm or more, it is an inexpensive method of deodorizing and does not have any negative effects on the human body.

[Brief explanation of drawings]

Figure 1 is a cross-sectional view of a deodorizing device showing an example of the present invention, Figure 2 is a graph showing the decomposition rate of trimethylamine in an example of the present invention, and Figure 3 is a graph showing the decomposition rate of methyl mercaptan in an example of the present invention. FIG. 4 is a graph showing the decomposition rate of acetaldehyde in an example of the present invention, and FIG. 5 is a cross-sectional view showing a conventional deodorizing device. 4... Photocatalyst layer, 5... Reaction member, 6... Air blower, 7... Electric light.

Claims (1)

[Scope of Claims] 1. A deodorizing method using a photocatalyst, in which tungsten oxide is irradiated with light having a wavelength of 300 nm or more and a maximum wavelength of 370 nm or less in the coexistence of tungsten oxide, an oxidizable compound, and a gas containing oxygen. 2. The photocatalytic deodorizing method according to claim 1, which uses tungsten oxide supporting a conductive inorganic substance.