JPH03229645A - Ozone decomposing catalyst - Google Patents

Abstract

PURPOSE:To obtain an ozone decomposing catalyst excellent in the removal capacity of ozone by supporting a catalytically active component on a carrier in definite thickness. CONSTITUTION:As a catalyst for decomposing and removing ozone contained in gas, a catalytically active component such as MnO2-Ag2O or MnO2-Ag2O-TiO2 is supported on a carrier such as a corrugated honeycomb made of a ceramic fiber or a honeycomb made of cordierite. At this time, the catalytically active component is supported in a thickness of 10-200mum. By this method, though the content of the catalytically active substance per unit volume of the catalyst is low, high ozone decomposing capacity is shown.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a catalyst for decomposing and removing ozone contained in a gas or the like.

<Prior art> Conventionally, methods for removing ozone, which is a harmful component contained in gases, include adsorption methods using porous materials such as activated carbon and zeolite, or oxidative decomposition methods using catalysts such as MnO2. Such methods have been used.

<Problems to be Solved by the Invention> However, none of the above conventional ozone removal methods can be said to be fully satisfactory.

That is, the adsorption method has a problem in that since the period during which the adsorbent exhibits its adsorption ability is limited, it requires regeneration, etc., and a great deal of labor and cost is required for maintenance of the removal device.

Further, although the oxidative decomposition method of ozone using a catalyst does not have the above-mentioned problems, it cannot be said that the catalyst performance is fully satisfactory at present.

The present invention was made to solve these problems that conventional ozone removal methods had, and its purpose is to provide an ozone decomposition method that has superior ozone removal ability compared to conventional methods. The purpose of this invention is to provide a catalyst for

Means for Solving the Problems> The ozone decomposition catalyst according to the present invention for achieving the above object is a catalyst in which a catalytically active component is supported on a carrier, and the active component has a thickness of 10 to 200 mm. It is characterized by being supported by

As the catalytic active components used in the present invention, as already proposed by the present inventors, Mn02-TiO2,
Mn09-5in2. Mn02-WO3, MnO
2V 2061 Cu OT I O21Co304-
Ti02. Fe203-TiO2゜Fe2O5-Au,
Those whose main component is a binary catalyst such as MnO2-Ag2O, and Mn02-C.

304-TiO2, Mn02-Co30. -Ag20,
Ni0-Mn02-TiO2, Mn02-WO2-Ti
02. Mn02-Mo03-TiO2, Mn02-V2
Those mainly composed of three-way catalysts such as O, -TiO2, or MnO2-alkali metal and/or alkaline earth metal oxides, with an oxide formation enthalpy of 100 Kc
Examples include those whose main component is a zeolite catalyst supporting a metal of less than al/g oxygen atoms. However, the method of the present invention is not limited thereto.

Among these, the most effective catalyst system is MnO2-Ag2O
, Mn02-Ag20-TiO2, MnO2-Ag20
-TiO2-Sin2. MnO,,-Ag20T1
02Al2O3+Ag2OTiO2,Ag2OA120
It is a silver-based catalyst such as No. 3.

Further, as carriers for supporting these active ingredients, those formed into various shapes using corrugated honeycombs made of ceramic fibers, honeycombs made of cordierite, clay, etc. are used. The shape of this molded body is not particularly limited, and various shapes such as a honeycomb shape, a pellet shape, a cylindrical shape, a plate shape, a pipe shape, etc. can be used.

Further, at this time, a molding aid may be added to impart shapeability to the carrier, and reinforcing agents such as inorganic fibers, organic binders, etc. may be added as appropriate to improve mechanical strength. The catalyst used in the present invention can be obtained by supporting 10μ to 200μ of the above-mentioned active ingredient on the carrier formed in this way. be. That is,
Since the decomposition reaction rate of ozone that has reached the active site is extremely high, the rate-determining step in the ozone decomposition reaction is the diffusion of ozone to the catalytic active site. Therefore, the catalytically active substances that can be effectively utilized are limited to those located at a certain depth from the surface of the catalyst supported on the carrier, that is, within the effective zone. As a result, even if the thickness of the catalytically active material coating the carrier (hereinafter referred to as "coating thickness") is made larger than the thickness of the effective zone, the ozone decomposition reaction rate cannot be increased. In other words, even if the amount of catalytically active material used is increased and the coating thickness is made larger than the thickness of the effective zone,
As mentioned above, the catalyst is wasted. Incidentally, the thickness of the effective zone varies depending on the porosity of the catalytically active material, and the greater the porosity, the thicker the effective zone. From the above, the method of the present invention makes it possible to concentrate the catalytically active substance in the effective zone without excess or deficiency, so that the ozone decomposition reaction rate can be increased even though the amount of the catalytic active ingredient per unit volume is low. It became possible to make it bigger. If the coating thickness of the catalytically active material is below the above range,
It is not possible to obtain a suitable ozone decomposition rate, and even if the coating thickness exceeds the above range, there is no commensurate improvement in the decomposition rate. It is undesirable that the catalytically active material supported either up or down is peeled off.

The reaction temperature during ozonolysis is preferably 0 to 40°C,
10-30 degreeC is more preferable. This is because if it is less than 0°C, the reaction rate becomes slow, and if it exceeds 40°C, additional thermal energy is required to raise the temperature, which is uneconomical.

Further, the contact between the catalyst and the reaction gas is preferably carried out at an area velocity (AV) of 5 to 50. This is because if the areal velocity is less than 5, a large amount of catalyst is required, and if the areal velocity is more than 50, the efficiency is low and a predetermined decomposition rate cannot be obtained. Here, the areal rate is the reaction amount (Nt%/u, u:Hr)
is the gas contact area per unit volume of catalyst <d/r? It is the value divided by >.

<Examples> Hereinafter, the present invention will be described in detail based on Examples. However, the present invention is not limited to the following examples.

8-Catalyst Preparation Example 1 After drying Kibushi clay at 100°C for 18 hours, it was pulverized in a sample mill with a screen of 0.5 mmφ. 20 kg of these pulverized materials were mixed with methyl cellulose binder (
1 kg of Yuken Kogyo YB-32) and water were added, mixed, and thoroughly kneaded in a kneader.

These clays were put into an auger screw type extruder equipped with a die for honeycomb extrusion, and a honeycomb-like material was extruded. Moisture was adjusted so that the pressure at this time was 30 to 35 kg/d. After drying the obtained honeycomb-like material at room temperature with ventilation, the temperature was raised to 500 °C at a temperature increase rate of 5 °C / hour,
After raising the temperature, it was maintained for 3 hours and then cooled at a cooling rate of 10° C./hour to obtain a honeycomb-shaped carrier with an aperture ratio of 64% and a pitch of 4.0 mm.

Next, 09.704 g of Mn with a specific surface area of 48 i/g was added to 1034 m of titania sol (TiO□ content: 150 g/u).
In addition to R, 250 g of glass beads were further added thereto, and after stirring and mixing for 30 minutes, the beads were separated to obtain a slurry. After diluting this slurry by adding 300 g of water, the above-mentioned honeycomb-shaped carrier cut into an appropriate size was immersed in the slurry, excess slurry was removed, dried, and then baked at 500°C for 3 hours. A two-way catalyst was obtained in which a Mn02-Ti02 layer (weight ratio 82:18) was supported with an average thickness of 10 μm. The thickness of this support layer was measured by XPS. The aperture ratio of this catalyst is 63%, and the gas contact area per unit volume (hereinafter referred to as "rAp") is 795d/r? Met. The catalytically active substance per unit volume of this catalyst is 0.0
It was 11 g/cc.

Example 2 In Example 1, the opening ratio was 6 in the same manner as in Example 1 except that the Mn02-TiO2 supporting layer was 50μ on average.
A binary catalyst of 0% Ap775ze/i was obtained. The catalyst active component material per unit volume of this catalyst is 0.056 g/c
It was c.

Example 3 In the same manner as in Example 1, except that the Mn02-TiO2 sol slurry was not diluted with water and the Mn02-TiO□ support layer was made to have an average of 100μ, the opening ratio was 56%, Ap750 d/rr? A two-way catalyst was obtained. A two-way catalyst supported at 100% was obtained. The catalyst substance per unit volume of this catalyst was 0.108 g/cc.

Example 4 In the same manner as in Example 1, except that the MnO2-TiO2 sol slurry was not diluted with water and the MnO2-TiO2 support layer was made to have an average of 200 μm, the frontage ratio was 49% and Ap700 A two-way catalyst was obtained which was supported at tn"/rt?. The catalyst material per unit volume of this catalyst was 0.201 g/cc.

Example 5 In Example 1, the supported catalyst active component material had a specific surface area of 4Eh+? /g of Mn02704g, titania sol (TiO2 content: 150g/min) 1034 frost y1 and also AgNO3 aqueous solution (Ag20 content: 100g/min)
Same as Example 1 except adding 1000 cranes,
MnO2-Ag20-Ti02 (74:16:10)
A three-way catalyst was obtained in which the average thickness of the catalyst was 10 μm. The catalytically active substance per unit volume of this catalyst was 0.012 g/cc.

Comparative Example 1 In Example 1, the width ratio was 64 in the same manner as in Example 1, except that the Mn02-TiO□ supporting layer was 5μ on average.
%, a binary catalyst of Ap798ze/ze was obtained. The catalyst active component substance per unit volume of this catalyst is 0.006 g/cc
Met.

Comparative Example 2 In the same manner as in Example 1, except that the MnO2-TiO2 sol slurry was not diluted with water and the MnO2-TiO2 support layer was made to have an average of 250 μm, the aperture ratio was 46% and Ap675d /I binary catalyst was obtained.

The catalyst material per unit volume of this catalyst is 0.242g/c
There was c.

Comparative Example 3 220 kg of Mn with a specific surface area of 48 t//g was added to 29.27 kg of titanium vine (150 g/g), thoroughly kneaded, dried up, fired at 500°C for 3 hours, and after cooling, the screen became 0. It was pulverized in a Sanflu mill with a diameter of .5 mm to obtain a fired powder with a Mn02-TiO2 weight ratio of 82:1B. 20 kg of these pulverized materials, 1 kg of methylcellulose binder (Yuken Kogyo YB-32) and water were added, and after mixing, the mixture was sufficiently kneaded in a kneader. These clays were put into an auger screw type extruder equipped with a die for honeycomb extrusion, and a honeycomb-shaped catalyst was extruded.

Moisture was adjusted so that the pressure at the time of separation was 30 to 35 kg/c1i. After drying the obtained honeycomb-shaped catalyst at room temperature with ventilation, the temperature was raised to 500°C at a rate of 5°C/hour, maintained for 3 hours, cooled at a rate of 10°C/hour, and opened. A two-way catalyst with a ratio of 63% and an Ap of 795 m'/- was obtained. The catalytically active substance per unit volume of this catalyst is 0
．． It was 63g/cc.

Comparative Example 4 Comparative Example 3 was carried out in the same manner as in Example 3, except that 6 kg of Kibushi clay was added to the clay for extruding the catalyst molded body. A three-way catalyst was obtained.The catalytically active substance per unit volume of this catalyst was 0.58 g/cc.

- Catalytic activity test Each of the catalysts obtained in Examples 1 to 5 and Comparative Examples 1 to 4 above was subjected to a catalytic activity test under the following reaction conditions using the test method whose flow sheet is shown in Figure 1. Ta. In the figure, (1) is an ozone generator, which generates ozone at an appropriate concentration from the air introduced into it, and guides this ozone-containing air to the catalyst layer (2). The ozone decomposition rate is (3
) It is determined by the following formula based on the values at the inlet and outlet of the catalyst layer measured with an ozone analyzer.

Ozone decomposition rate (%) = Inlet ozone concentration (Reaction conditions) Space velocity: 20000/Hr Reaction temperature: 20℃ The above test results are shown in Table 1.

(Hereinafter, blank space) Table 1 As is clear from the above table, all the catalysts obtained in Examples 1 to 5 had a higher ozone decomposition rate (%) than the catalyst obtained in Comparative Example 1.2.4. have.

From the above, it can be seen that the catalyst according to the present invention exhibits high ozone decomposition performance despite having a low catalytic active substance per unit volume force.

<Effects of the Invention> The ozone decomposition catalyst according to the present invention has an excellent effect of efficiently removing ozone.

[Brief explanation of drawings]

FIG. 1 is a flow sheet of the catalyst activity test. (1) Ozone generator (2) Catalyst layer (3) Ozone analyzer Figure 1

Claims (1)

[Claims] An ozone decomposition catalyst comprising a catalytically active component supported on a carrier, characterized in that the active substance is supported to a thickness of 10 to 200 μm.