JPH0478326B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to a method for deodorizing toilet odors, pet odors, cigarette odors, cooking odors, body odors, etc. using a photocatalyst. Conventional technology Bad odor components such as cigarette odor, toilet odor, pet odor, cooking odor, and body odor that occur in homes and offices are nitrogen compounds such as ammonia, amines, indole, skatole, hydrogen sulfide, methyl mercaptan, methyl sulfide, Sulfur compounds such as methyl disulfide, aldehydes, ketones, alcohols,
There are a wide variety of components, from low to high boiling points, such as fatty acids and aromatic compounds. Conventional deodorizing methods used in homes and offices include pouring chemicals into the source and causing a chemical reaction, masking with aromatic substances, adsorption with activated carbon or zeolite, and adsorption methods impregnated with chemicals. There is a way to concentrate and react with bad odors. The first two methods are local deodorization methods and are used in areas such as toilets and areas where pets are present. On the other hand, the latter two methods are deodorizing methods that can be used in combination with a blower as a deodorizing device and can be used for general purposes from narrow spaces to wide spaces. Among these, activated carbon is the most effective means, but even activated carbon has a weak adsorption power for malodorous components such as low-boiling nitrogen compounds such as ammonia and methylamine, and lower aliphatic aldehydes such as formalin, acetaldehyde, and acrolein. Therefore, deodorizers are used in which chemicals are attached to activated carbon. Problems to be Solved by the Invention Low-boiling nitrogen compounds such as ammonia and methylamine can be effectively adsorbed with a deodorizer made of activated carbon impregnated with an organic acid or an inorganic acid, and the adsorption capacity thereof is also large. On the other hand, formalin, acetaldehyde,
A deodorizer made of activated carbon impregnated with aniline is effective for adsorbing lower aliphatic aldehydes such as acrolein, but since the amount of aniline that can be impregnated is small,
The adsorption capacity for aldehydes is small and the lifespan is short. Cigarette odors and odors emitted from new construction materials and furniture, which have recently become a problem, contain many formalin, acetaldehyde, etc., but there has been no effective deodorizing method. The present invention solves the above-mentioned conventional problems, and aims to provide a deodorizing method that effectively decomposes bad odors through photocatalytic action. Means for Solving the Problems In order to achieve the above object, the photocatalytic deodorizing method of the present invention uses one oxide selected from the group consisting of iron titanate, iron oxide, bismuth oxide and molybdenum oxide and titanium oxide. The mixed metal oxide is irradiated with ultraviolet rays in the coexistence of the mixed metal oxide, an oxidizable compound, and a gas containing oxygen. Effect The present inventors have been researching the decomposition and deodorization of bad odors through photocatalytic action for some time.
In the presence of a mixed metal oxide of titanium oxide and an oxide selected from the group consisting of iron titanate, iron oxide, bismuth oxide, and molybdenum oxide, the oxidation of aldehydes is much more effective than the generally known titanium oxide alone. It was discovered that the decomposition ability was high. The mixed metal oxide of the present invention is efficiently decomposed by irradiation with ultraviolet rays. The principle of action of the mixed metal oxides mentioned above is currently being studied in detail, but electrons in the valence band of each of the above oxides and titanium oxide semiconductors absorb ultraviolet light and are excited to the conduction band, and the electrons generated there. Holes in the valence band react with hydroxyl groups (OH groups) on the surface of the catalyst, and electrons excited in the conduction band react with oxygen (O) to form highly active OH radicals, O radicals,
It is assumed that O2 ^- is generated and this oxidatively decomposes the oxidizable compound. Further, it is presumed that the electrons and holes generated in titanium oxide interact with the electrons and holes generated in each of the above oxides, resulting in a synergistic effect. Furthermore, when a conductive inorganic substance such as platinum, palladium, rhodium, ruthenium oxide, or silver is supported on this mixed metal oxide, the oxidative decomposition effect becomes even stronger. Among them, the effect of platinum is remarkable. The deodorizing method of the present invention is not only excellent in decomposing aldehydes, but also other malodorous substances such as ammonia, nitrogen compounds of amines, hydrogen sulfide, sulfur compounds of mercaptans, ketones, alcohols, fatty acids, and aromatic compounds. It can be decomposed by oxidation and made odorless. Examples Next, examples of the present invention will be described. The titanium oxide used in the present invention includes:
The anatase type has high activity, but the rutile type may also be used. Also, among the oxides, iron titanate
Although FeTiO ₃ has high activity, Fe ₂ TiO ₅ may also be used. Platinum is effective as the conductive inorganic substance, but noble metals such as palladium, rhodium, and silver, ruthenium oxide, and the like may also be used. Further, the ultraviolet rays only need to have a wavelength of 400 nm or less, and may be either far ultraviolet rays or near ultraviolet rays. These ultraviolet rays can be generated by using a high-pressure mercury lamp, an ultra-high-pressure mercury lamp, a low-pressure mercury lamp, a xenon lamp, etc. alone or in combination. Further, the deodorizing method may be performed by introducing the gas to be treated into a specific reactor and performing batch treatment, or by continuous treatment. The mixed metal oxide used in the present invention is used by coating it on the surface of the light source, or by coating or impregnating a support provided around the light source. Next, specific examples will be described. Suspend the metal oxide powder of the weight shown in Table 1 in methanol, and spread this suspension to a thickness of 0.5 mm * width 120 mm * length.
It was applied to a 240 mm alumina-silica ceramic paper and dried to form a photocatalyst. Platinum was supported by impregnating a ceramic paper coated with the metal oxide with an ethanol solution of chloroplatinic acid and heat-treating the paper to support the platinum as fine particles. Then, as shown in FIG. 1, the catalyst 1 having the above structure was placed on a stainless steel stand 2 and placed in a reaction vessel 3 made of aluminum with an internal volume of 36 mm, at a distance of 100 mm from a light source 4. As light source 4, a 10 watt germicidal lamp (ultraviolet ray output approximately 1.8 watts, dominant wavelength 254 nm) was used. A saturated gas of acetaldehyde was injected into the reaction vessel 3, stirred with a fan 5 to make the concentration uniform, and the initial concentration was measured. Next, a germicidal lamp was turned on, and changes in the astaldehyde concentration over time were examined using gas chromatography. The results were shown when the mixed metal oxide catalyst was not irradiated with ultraviolet rays, when only ultraviolet rays were irradiated without using a catalyst, and when only anatase titanium oxide or only iron titanate FeTiO ₃ was applied to ceramic paper using the above method. Figure 2 shows a comparison of the case where the catalyst was irradiated with ultraviolet rays. Further, the respective conditions are shown in Table 1.

[Table] As shown in Figure 2, when a gas containing acetaldehyde and oxygen is irradiated with ultraviolet rays in the presence of a mixed metal oxide of titanium oxide and iron titanate, acetaldehyde is extremely effectively decomposed and rendered odorless.
Furthermore, if a mixed metal oxide supporting platinum is used, the decomposition proceeds even more effectively. Further, a mixed metal oxide of titanium oxide and iron titanate has a greater photocatalytic effect than titanium oxide alone. As described above, according to the present invention, aldehydes, which have conventionally been difficult to adsorb with activated carbon, can be decomposed to extremely low concentrations and rendered odorless. Furthermore, according to this embodiment, the decomposition is not limited to aldehydes, but also other malodorous substances such as ammonia, nitrogen compounds such as amines, hydrogen sulfide, sulfur compounds such as mercaptans, ketones, alcohols, fatty acids, and aromatic compounds. Can be oxidized and made odorless. Furthermore, carbon monoxide can also be oxidized to carbon dioxide and rendered harmless. In addition, excellent deodorizing ability can be obtained by using the method of the example in combination with other adsorbents or chemical methods. Next, the results of an experiment conducted in the same manner as in the above example, in which iron oxide, bismuth oxide, and molybdenum oxide were sequentially selected in place of iron titanate in the above example, will be shown. The conditions for iron oxide are as shown in Table 2.
The results are shown in Figure 3. α-Fe ₂ O ₃ with high activity was used as iron oxide, but γ-Fe ₂ O ₃ , Fe ₃ O ₄ ,
FeO may also be used.

[Table] The upper surface of bismuth oxide is shown in Table 3, and the results are shown in FIG. α-Bi ₂ O ₃ with high activity was used as bismuth oxide, but β-type and γ-type
type, δ type may also be used.

【table】

[Table] Table 4 shows the results for molybdenum oxide, and the results are shown in Figure 5. Although MoO ₃ was used as the molybdenum oxide, it may be MoO ₂ or an oxide in an intermediate state between the two.

[Table] Effects of the Invention As is clear from the examples described above, the deodorizing method using a photocatalyst of the present invention can decompose aldehydes, which were difficult to adsorb with activated carbon, to an extremely low concentration and make them odorless. Malodorous substances such as ammonia, nitrogen compounds such as amines, hydrogen sulfide, sulfur compounds such as mercaptans, ketones,
Alcohols, fatty acids and aromatic compounds can also be oxidized to make them odorless. Furthermore, it has the excellent effect of oxidizing carbon monoxide to carbon dioxide and rendering it harmless.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of an apparatus for measuring the decomposition performance of the photocatalyst of the present invention, and FIGS. 2 to 5 are decomposition curve diagrams of acetaldehyde in each example of the present invention. 1...Catalyst, 4...Light source.

Claims (1)

[Claims] 1. In the coexistence of a mixed oxide of titanium oxide and one oxide selected from the group consisting of iron titanate, iron oxide, bismuth oxide, and molybdenum oxide, and an oxidizable compound and a gas containing oxygen, A deodorizing method using a photocatalyst that irradiates mixed metal oxides with ultraviolet light.