JP2995608B2 - Ozone filter and its manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ozone filter using an active manganese dioxide (hereinafter referred to as a manganese dioxide catalyst) having an ozone decomposability and a method for producing the same.

[0002]

2. Description of the Related Art Ozone has two effects on humankind. In other words, ozone is widely used in the fields of medicine, food, etc. for its bactericidal action based on its strong oxidizing ability. On the other hand, based on the toxicity of ozone itself, when the concentration in air exceeds 0.1 ppm, respiration occurs. Make the system feel stimulus 5
Above 0 ppm it is dangerous to life. Accordingly, in recent years, with the spread of office equipment that generates ozone such as electrostatic copiers and laser printers and the causes of ozone generation have increased, it has been desired to develop a simple method for decomposing ozone in the air. .

Conventionally, techniques for detoxifying low-concentration ozone in the air include an activated carbon adsorption method, a thermal decomposition method, a wet method, and a catalytic cracking method. However, catalytic cracking is highly safe and is carried out at room temperature. It is advantageous in many respects, such as being possible and easy to implement on a small scale. An example of an ozone filter which enables simple and small-scale catalytic decomposition of ozone is described in JP-A-5-23591.
There is proposed an ozone filter in which a manganese dioxide catalyst is supported on a honeycomb-structured carrier made of high porosity paper.

[0004] An ozone filter using a manganese dioxide catalyst is characterized by exhibiting excellent ozone resolution over a long period of time. However, in rare cases, when used for a long period of time, an odor may be generated even if there is no abnormality in the ozone resolution, and this is pointed out as a problem.

[0005]

DISCLOSURE OF THE INVENTION The present inventors have examined the above-mentioned ozone filter which emits a bad smell as a result of long-term use, and as a result, have confirmed that a large number of organic compounds are adsorbed on the filter. . The main organic compounds identified are acetone, 2-propanol, tert-butanol, methyl ethyl ketone, lower fatty acids, chloroform, toluene, butyl acetate, ethyl benzene, xylene, butyl ethyl ketone, styrene, α-methyl styrene, o -Xylene, acetophenone, tert-butylphenyl ether, dimethylbiphenyl and the like. These compounds are not adsorbed on the ozone filter before use, or they are adsorbed to a very small extent. It is estimated to be.

The reason why these compounds, which hardly exist in the atmosphere of the normal environment, are adsorbed on the ozone filter is considered as follows. The air contains a trace amount of organic components emitted by humans and animals and plants, for example, organic substances derived from sweat, cigarettes, perfumes, etc., which pass through the ozone filter. Further, organic substances released during operation of the device equipped with the ozone filter, for example, trace amounts of organic substances derived from toner, machine oil, etc., also pass through the ozone filter. Some of the organic substances that have come into contact with the ozone filter are oxidized and decomposed as they are or by the action of the manganese dioxide catalyst and ozone, and then adsorbed by the manganese dioxide catalyst and accumulate on the filter.

[0007] These organic substances have no problem as long as they are strongly odorous substances if they are adsorbed by the manganese dioxide catalyst. It is believed that some of these odors combine to give an unpleasant odor because they are released into the atmosphere in the treated air. Accordingly, an object of the present invention is to provide an improved ozone filter which does not give off a bad smell even after long-term use while using a manganese dioxide catalyst excellent in ozone resolution.

[0008]

SUMMARY OF THE INVENTION The present invention has succeeded in achieving the above _object, SiO 2 / _Al 2 O ₃ ratio of 15 or more of zeolite powder and manganese dioxide catalyst latter 1
The former is carried on a carrier made of inorganic fiber paper having a high porosity at a ratio of 15 to 40 parts by weight per 100 parts by weight , and the zeolite powder is supported on a core portion of the carrier at a higher density than a surface layer portion of the carrier. An object of the present invention is to provide an ozone filter characterized in that a manganese catalyst is supported at a higher density on a surface layer than on a core of a carrier.

The present invention also relates to a method for producing the above-mentioned ozone filter, that is, a method comprising impregnating a support made of inorganic fiber paper having a high porosity with a suspension of zeolite powder having a SiO ₂ / Al ₂ O ₃ ratio of 15 or more, followed by drying. The present invention also provides a method for producing an ozone filter, which comprises impregnating a carrier after treatment with a suspension of finely divided active manganese dioxide having the ability to degrade ozone, followed by drying.

The zeolite supported on the carrier together with the manganese dioxide catalyst in the ozone filter according to the present invention has a SiO ₂ / Al ₂ O ₃ ratio of 15 or more. SiO
This zeolite having a high ₂ ratio has a SiO ₂ / Al ₂ O ₃ ratio of 2
In contrast to ordinary zeolites of up to about 15 which show strong hydrophilicity and are used as desiccants, they are known to adsorb hydrocarbon compounds better than water vapor (hereinafter referred to as hydrophobicity). Strong zeolites are called hydrophobic zeolites). The composition of a typical example is HalSi ₃₅ O
₇₂ , HAlSi ₂₅ O _52, etc.
No. 5, JP-A-1-31457). A commercially available product that is easily available includes a SiO ₂ / Al ₂ O ₃ ratio of 50 to 500.
There is a degree.

An ozone filter in which a hydrophobic zeolite powder is supported on a carrier together with a manganese dioxide catalyst,
It does not give off a bad smell even after long-term use. Although the reason is not clear, the adsorption of either organic matter in the air after or before the oxidation by ozone in the vicinity of the manganese dioxide catalyst by the hydrophobic zeolite helps to prevent emission of odor-causing substances. It is assumed that However, if a hydrophobic zeolite is supported together with a manganese dioxide catalyst, the ozone resolution tends to be slightly inferior.However, the hydrophobic zeolite powder is supported at a higher density on the core than on the surface layer of the carrier, and the manganese dioxide catalyst is supported on the core. By supporting the manganese dioxide catalyst at a higher density on the surface layer than on the core of the carrier, the manganese dioxide catalyst can exhibit its original ozone resolution.

[0012] responsible Jiryou of hydrophobic zeolite in the ozone filter of the present invention shall be the 15 to 40 parts by weight per 100 parts by weight of manganese dioxide catalyst. If the amount of the hydrophobic zeolite is not sufficient, the generation of offensive odor cannot be completely prevented. On the other hand, when the hydrophobic zeolite is supported more than necessary, not only the amount of the supported manganese dioxide catalyst is limited, but also the ozonolysis activity of the manganese dioxide catalyst is inhibited.

Hereinafter, a method of manufacturing the ozone filter of the present invention will be described. The manganese dioxide catalyst used as the ozonolysis catalyst is not particularly limited, and a commercially available product or any one produced by any production method can be used. Particularly preferred is a particle size of 0.3 to 50 μm and specific surface area. Is 150
It is manganese dioxide in the form of fine powder of m ² / g or more. Such fine manganese dioxide having a large specific surface area can be prepared by, for example, reacting an aqueous suspension of manganese carbonate with an aqueous solution of an oxidizing agent such as hypochlorite or permanganate to precipitate the resulting manganese dioxide. Can be easily produced, for example, by a method of treating an acid with an acid and further neutralizing with an alkali (JP-B-55-8456).

As the hydrophobic zeolite, those having the above-mentioned composition, preferably having a particle size of about 0.5 to 30 μm, are used. Since the zeolite coarser than that in the above particle size range hardly enters into the fine interfiber space of the carrier made of inorganic fiber paper, it may not be able to be unevenly distributed in the carrier core.

A carrier made of a high-porosity inorganic fiber paper supporting a manganese dioxide catalyst and a hydrophobic zeolite is described in, for example, JP-A-59-10345. That is, it is made of inorganic fiber such as alumina fiber, silica-alumina fiber, glass fiber, rock wool and the like.
A paper having a high porosity of about 95% and a honeycomb structure obtained by processing the paper. "Hanicle" (a product of Nichias Co., Ltd.)
There is. The porosity is a value obtained from the following equation. Porosity (%) = (1−apparent density / true density) × 10
0

The thickness of the paper is not particularly limited, but is most preferably about 0.1 to 0.4 mm.

The honeycomb-structured carrier made of inorganic fiber paper is most suitable for efficiently treating a large air volume of the air to be treated with a low pressure loss, and is a carrier of a manganese dioxide catalyst for treating low-concentration ozone-containing air. As excellent. In addition, since it can be cut, any shape and size can be easily manufactured, and there is a feature that it does not crack even if dropped. Preferred honeycomb structures have an effective surface area of 8 to 40 cm ² / cm ³ (particularly preferably 20 to 40 cm ² / c
m ³ ), an aperture ratio of 50 to 90% (particularly preferably 50 to 70%)
%)belongs to.

First, a hydrophobic zeolite is supported on the above-mentioned carrier. The hydrophobic zeolite to be supported is an inorganic binder such as silica sol, alumina sol, titania sol,
Alternatively, they are suspended in water together with a mixture thereof. At this time, it is desirable to use the minimum amount of the binder necessary for fixing the hydrophobic zeolite to the fiber surface of the carrier, and if used excessively, the cured product covers the zeolite particles and prevents the odor generation. Interfere with. The suspension of the hydrophobic zeolite is sufficiently absorbed by the carrier by immersion or coating, and after removing the excess zeolite suspension and drying, the zeolite particles penetrate to the core of the carrier having fine voids and adhere to the fiber surface. Fixed.

The manganese dioxide catalyst is then loaded on the support having the hydrophobic zeolite immobilized thereon as described above. The loading treatment can be carried out in the same manner as the loading of the hydrophobic zeolite. Since the hydrophobic zeolite is fixed first and the pores of the carrier are small and small, the manganese dioxide catalyst hardly reaches the core of the carrier, and most of the manganese dioxide catalyst is fixed to the surface layer of the carrier. If it is difficult to support the required amount of catalyst at one time, the catalyst impregnation and drying are repeated until an appropriate amount of catalyst is fixed.

Thus, an ozone filter is obtained in which the zeolite powder is supported at a higher density on the core than on the surface of the carrier, and the manganese dioxide catalyst is supported on the surface of the carrier at a higher density than the core.

When the hydrophobic zeolite and the manganese dioxide catalyst are supported on the carrier, a part of the interfiber space of the paper is left as a void, and the residual porosity, that is, the porosity after the zeolite and the catalyst are supported. When the porosity calculated according to the calculation formula is about 50 to 85%, the air to be treated is easily diffused to the surface of the zeolite or the catalyst fixed in the inter-fiber voids of the paper constituting the carrier, and the use of the zeolite and the catalyst The rate improves.

[0022]

【Example】

Example 1 A paper having a thickness of 0.1 mm and a porosity of 90% made of silica-alumina fiber having a fiber diameter of 2 to 3 μm and a small amount of an organic binder was processed into corrugated paper and corrugated with an unprocessed flat paper. The honeycomb structure carrier having 560 / in ² cells was obtained by alternately stacking the contacts and bonding the contacts with a silica-based adhesive.

The manganese dioxide catalyst supported on the carrier was prepared by the following method. First, a precipitate formed by reacting an aqueous solution of manganese sulfate and an aqueous solution of sodium carbonate is washed with water and dried, and 1 kg of manganese carbonate obtained is 2,000 ml of water.
The solution was heated to 60 ° C., and an aqueous sodium hypochlorite solution was added little by little while stirring. As a result, manganese carbonate reacted while generating carbon dioxide gas and changed to black manganese dioxide. After the completion of the reaction, the formed precipitate of manganese dioxide was filtered, washed with water and dried. The resulting manganese dioxide catalyst has a specific surface area of 220 m ² / g and an average particle size of 5
μm.

As the hydrophobic zeolite supported on the carrier together with the manganese dioxide catalyst, SiO ₂ / Al ₂ O ₃ =
Those having an average particle diameter of 150 and an average particle diameter of 5 μm were used. 20 parts by weight of this hydrophobic zeolite is mixed with 100 parts by weight of silica sol (solid content: 30% by weight) and 80 parts by weight of water to form a slurry, and the obtained slurry is added to the above honeycomb structured carrier (dimensions: cell opening surface 100 mm × 100mm, length in ventilation direction 15
mm) was immersed, excess slurry was removed and dried.

Next, the zeolite-supported carrier was immersed in a slurry comprising 100 parts by weight of the manganese dioxide catalyst, 80 parts by weight of silica sol (solid content: 30% by weight), and 280 parts by weight of water, and dried. Thereafter, the above-mentioned immersion and drying in the manganese dioxide catalyst slurry were repeated once, whereby an ozone filter having a manganese dioxide catalyst loading of 46 g / m ² , a hydrophobic zeolite loading of 14 g / m ² , and a residual porosity of 70% was used. I got When the surface of the ozone filter was observed with an electron microscope, the surface was densely covered with a manganese dioxide catalyst, and almost no hydrophobic zeolite particles were recognized.

Comparative Example 1 An ozone filter having a manganese dioxide catalyst carrying amount of 46 g / m ² was produced by performing the same carrier treatment as in Example 1 using only the manganese dioxide catalyst slurry prepared in the same manner as in Example 1. .

Comparative Example 2 100 parts by weight of manganese dioxide catalyst, hydrophobic zeolite 3
0 parts by weight and 100 parts by weight of silica sol (all the same as those used in Example 1) were mixed with 200 parts by weight of water, and the same slurry having the same honeycomb structure as that used in Example 1 was added to the obtained slurry. Dipped and dried. Then immersion,
By repeating the drying once more, the manganese dioxide loading was 46 g / m ² and the hydrophobic zeolite loading was 14 g / m ² .
An ozone filter having m ² and a residual porosity of 70% was obtained.

When the surface of the ozone filter was observed with an electron microscope, it was found that the manganese dioxide catalyst and the hydrophobic zeolite were mixed on the surface at a ratio almost similar to the above-mentioned loading ratio.

Next, the ozone resolution of the ozone filters of the above examples was examined by the following method. Test method: Ozone-containing air obtained by treating dehumidified air with a silent discharge type ozone generator was diluted with clean air to obtain a gas to be treated having an ozone concentration of 0.5 ppm, a temperature of 27 ° C. and a relative humidity of 80%. Prepare. The gas to be treated is converted to a space velocity of 280,000 / H
At r, the honeycomb structure carrier is kept flowing through the ozone filter arranged so that the cell opening surface is perpendicular to the ventilation direction. After a lapse of a predetermined time, the outlet side air is sampled, and the ozone decomposition rate (by the following formula) is measured.

Ozone decomposition rate (%) = (inlet ozone concentration−
Outlet ozone concentration) × 100 / inlet ozone concentration The measurement results were as follows.

[0031]

[Table 1] Ozone decomposition rate (%)

Next, an ozone filter was mounted on an electrostatic recording type copier in each case and used continuously, and a test was conducted to compare the number of copies to produce a bad odor. At the time of copying 10,000 copies, a bad smell was felt. However, the machine equipped with the product of Example 1 and the product equipped with the product of Comparative Example 2 did not feel the bad smell even after copying 180,000 copies.

[0033]

As described above, the ozone filter of the present invention does not generate a bad smell even if it is used for a long period of time despite the use of the manganese dioxide catalyst, and has a good working environment around the equipment generating ozone. Can be kept.

Claims (3)

(57) [Claims] 1. A zeolite powder having an SiO ₂ / Al ₂ O ₃ ratio of 15 or more and a finely powdered active manganese dioxide having an ozone decomposability are used in the amount of 15 to 4 parts per 100 parts by weight of the latter.
It is supported on a carrier made of inorganic fiber paper having a high porosity in a ratio of 0 parts by weight , and the zeolite powder is supported on the core at a higher density than the surface layer of the carrier, and the manganese dioxide is contained on the carrier from the core. An ozone filter characterized in that the ozone filter is also supported on the surface layer at a high density. 2. A carrier made of inorganic fiber paper having a high porosity is impregnated with a suspension of zeolite powder having a SiO ₂ / Al ₂ O ₃ ratio of 15 or more, dried, and then subjected to ozone decomposing. 2. The method according to claim 1, wherein the suspension is impregnated with a suspension of active manganese dioxide having a fine powder form and then dried.
Of ozone filter described above. 3. A suspension made of inorganic fiber paper having a porosity of 70 to 90% is impregnated with a suspension of zeolite powder having a SiO ₂ / Al ₂ O ₃ ratio of 15 or more and a particle size of 0.5 to 30 μm. 2. The method for producing an ozone filter according to claim 1, wherein the ozone filter is dried and then impregnated with a suspension of activated manganese dioxide having the ability to degrade ozone, followed by drying.