JPH04334547A - Ozone decomposing catalyst - Google Patents

Abstract

PURPOSE:To provide an ozone decomposing catalyst excellent not only in the productivity of a low pitch honeycomb but also in ozone decomposing capacity. CONSTITUTION:An ozone decomposing catalyst is constituted by supporting an active substance having ozone decomposing capacity on an MnO2-containing carrier in the thickness of 5-100mum and shows excellent ozone decomposing effect.

Description

[Detailed description of the invention]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a catalyst for decomposing and removing ozone contained in gases.

[Prior Art] Conventionally, methods for removing ozone, a harmful component contained in gases, include adsorption methods using porous materials such as activated carbon and zeolite, and oxidative decomposition methods using catalysts such as MnO2. method has 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. In addition, although the ozone oxidation decomposition method using a catalyst does not have the above-mentioned problems, it is difficult to say that the catalyst performance is fully satisfactory at present, and even if the initial performance is good, there are problems during the reaction. There was a problem that it deteriorated over time. The present invention was made to solve these problems that conventional ozone removal methods had, and its purpose is to:
At the same time, it has superior ozone removal ability compared to conventional methods.
The purpose of the present invention is to provide an ozone decomposition catalyst that can be used for a long period of time and has excellent durability. Furthermore, the present invention is an improvement on the invention disclosed in Japanese Patent Application No. 2-24843 filed by the present inventors. In other words, in the reaction according to the present invention, the reaction rate is determined by diffusion within the solid, and the reaction proceeds only on the surface of the catalyst. has already been proposed. However, these methods also have the problem that, for example, as the number of cells/inch2 of the honeycomb structure increases, the manufacturing method thereof becomes more difficult. The present invention has made it possible to solve these problems. In other words, since it has become possible to reduce the coating thickness, it has excellent productivity of shaped catalysts, especially low pitch honeycombs, and at the same time has improved ozone decomposition ability and ,
The objective is to provide an ozone decomposition catalyst with excellent long-term durability.

[Means for Solving the Problems] The ozone decomposition catalyst according to the present invention for achieving the above object is characterized in that an active species having an ozone decomposition ability is supported on a carrier containing MnO2 as a base. There is. Ti, Cu, Mn, Ni, Fe, Ag, Au, which the present inventors have already proposed as catalytic active species having ozone decomposition ability.
, various metals such as Mo, Zr, Sn, Nb, and W, and at least one of metal oxides or sulfates, or those containing activated carbon or acidic clay. . As such a catalyst, for example, if it is expressed using a metal oxide to be supported,
Those whose main components are MnO2, NiO, CuO, Fe2O3, and MnO2-TiO2, MnO2-CuO, M
nO2-Fe2O3, MnO2-Ag2O, NiO-C
o3O4, NiO-TiO2, NiO-MnO2, Ni
O-Ag2O, NiO-MoO3, NiO-WO3, N
Those whose main component is iO-SnO2 etc., and MnO2-
Ag2O-TiO2, MnO2-CuO-Ag2O, N
iO-MnO2-Ag2O, NiO-MnO2-TiO
An example is one in which the main component is 2 or the like. The shape of the catalyst used in the method of the present invention is not particularly limited, and various shapes can be used, such as a honeycomb shape, a pellet shape, a columnar shape, a plate shape, a pipe shape, and the like. Of these, MnO
A carrier containing 2 can be mainly produced by a kneading method. In producing the carrier, a molding aid may be added to impart shapeability, and reinforcing agents such as inorganic fibers, organic binders, etc. may be appropriately added to improve mechanical strength. MnO2 contained in these carriers
is preferably 10 wt% or more, more preferably 20 wt% or more. If it is less than 10 wt%, the ozone decomposition ability of the carrier will be significantly reduced, so in order to obtain high resolution, it is necessary to increase the coating thickness. The catalytically active species supported on these carriers can be produced mainly by a wash coating method or the like. The thickness of these coats is 5 to 1
00μ is preferable, and 10-50μ is more preferable. or,
When it is less than 5μ, the decomposition activity decreases, and when it is more than 100μ, there is no improvement in the decomposition activity and only the pressure drop increases. The reaction temperature during ozonolysis is preferably 0 to 40°C, and 10 to 3°C.
0°C is more preferred. This is because if the temperature is less than 0°C, the reaction rate will be slow, and if it exceeds 40°C, additional thermal energy will be required to raise the temperature, which is uneconomical. In addition, the contact between the catalyst and the reaction gas is carried out at an areal velocity of 5 to 70 (
It is preferable to carry out at AV (area velocity). 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 area velocity is the value obtained by removing the space velocity (1/Hr) by the gas contact area per unit volume (m2/m3).

EXAMPLES The present invention will be explained in detail below based on examples. However, the present invention is not limited to the following examples. A. Catalyst Preparation Example 1 Kibushi clay was dried at 100° C. for 18 hours and then ground in a sample mill with a screen of 0.5 mmφ. 8 kg of these pulverized materials, Mn with a specific surface area of 67 m2/g
2 kg of O2, 0.8 kg of methyl cellulose binder (Yuken Kogyo YB-32) and water were added, and after mixing, the mixture was thoroughly kneaded using a kneader. These clays were put into an auger screw extruder equipped with a die for honeycomb extrusion, and the honeycomb-like material was dried with ventilation at room temperature, and then heated with N2
Raise the temperature to 500°C at a heating rate of 5°C/hour in an air flow,
After the temperature was raised and maintained for 3 hours, it was 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 1.0 mm. Next, MnO with a specific surface area of 67 m2/g
2. 500 ml of water and a small amount of binder were added to 1 kg, and 250 g of glass beads were added, and after stirring and mixing for 30 minutes, the beads were separated to obtain a slurry. After diluting this slurry by adding 300 ml of water, the above-mentioned honeycomb-shaped carrier cut into an appropriate size was immersed.
Excess slurry was removed and dried to obtain a catalyst supporting MnO2 with an average thickness of 38μ. The thickness is calculated using EPMA.
The average value was determined by line analysis with n number of 10. The thickness was determined using the same method below. Example 2 In the same manner as in Example 1, except that 200 g of 1 kg of MnO2 was changed to TiO2 and the dilution water was further changed to 500 ml, MnO2-TiO2 (weight ratio 80:20) was used. A supported catalyst was obtained by adjusting the number of coats. Coat thickness: 6μ, 10μ, 15μ, 3
Five types of catalysts were obtained with different sizes of 0μ and 42μ. Example 3 In the same manner as in Example 1 except that 100 g of 1 kg of MnO2 was changed to Ag2O, MnO
A catalyst was obtained in which 2-Ag2O (weight ratio 90:10) was supported with an average thickness of 47μ. Example 4 In the method of Example 1, 5 kg of pulverized Kibushi clay, M
A honeycomb-shaped carrier was obtained in accordance with Example 1 except that nO2 was 5 kg and methyl cellulose binder (Yuken Kogyo YB-32) was 1 kg. This carrier was treated with the same slurry as that used in Example 2, and the number of coats was adjusted to give a coating thickness of 5μ, 11μ, 20μ, 33μ, and 4μ.
Five types of catalysts of 5μ were obtained. Example 5 In the same manner as in Example 1, except that 400 g of 1 kg of MnO2 was changed to Fe2O3 with a specific surface area of 38 m2/g, and 100 g was changed to Ag2O, MnO
2-Fe2O3-Ag2O (weight ratio 50:40:10)
A catalyst having an average thickness of 51 μm was obtained. Example 6 In Example 1, MnO2-activated carbon-T was prepared in the same manner as in Example 1 except that 200g of 1kg of MnO2 and 100g of activated carbon (Shirasagi A manufactured by Takeda Pharmaceutical Co., Ltd.) was replaced with TiO2.
A catalyst was obtained in which iO2 (weight ratio 70:20:10) was supported with an average thickness of 38μ. Example 7 In Example 1, instead of MnO2, the specific surface area was 55 m
A catalyst supporting CuO with an average thickness of 45 μm was obtained in the same manner as in Example 1 except that CuO was used. Comparative Example 1 A catalyst in which MnO2 was supported with an average thickness of 50 μm was obtained in the same manner as in Example 1 except that 20 kg of Kibushi clay was used and activated carbon was not added when extruding the carrier. Example 8 A catalyst in which MnO2 was supported to an average thickness of 57 μm was obtained in the same manner as in Example 4, except that when extruding the carrier, Kibushi clay was used in an amount of 18 kg, and activated carbon was added in an amount of 2 kg. Reference example: A mixture of 30 g of MnO2 with a specific surface area of 48 m2/g, titanium tetrachloride, and syrinsol (TiO2:SiO2: 1:
1) While stirring and mixing 70 g, ammonia gas was blown in to perform a neutralization reaction, and a slurry-like precipitate was generated. After thoroughly washing the obtained precipitate with water, the temperature was 500°C.
The three-way catalyst MnO2-TiO2-SiO2 (weight ratio 35:30
:35) Powder was obtained. Hereinafter, in the same manner as in Example 1, SiO2-MnO2-TiO2 (weight ratio 35:30:3
A three-way catalyst was obtained in which 5) was supported at a loading rate of 99%. B. Catalytic activity test The catalysts obtained in Examples 1 to 8, Comparative Example 1, and Reference Example were subjected to a catalytic activity test under the following reaction conditions using a testing apparatus whose flow sheet is shown in Figure 1. The ozone decomposition rate at the initial stage, after 10 hours, and after 100 hours was determined. 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 determined by the following formula from the values at the inlet and outlet of the catalyst layer measured by the ozone analyzer in (3). (Reaction conditions) Space velocity: 20,000/Hr Inlet ozone concentration: 10 ppm Reaction temperature: 20° C. The above test results are shown in Table 1. As is clear from the above table, all the catalysts obtained in Examples 1 to 8 have a higher ozone decomposition rate (%) than the catalysts obtained in Comparative Example 1 and Reference Example, and at the same time It shows almost no deterioration in performance over time and has excellent durability.

Effects of the Invention The ozone decomposition catalyst according to the present invention efficiently removes ozone and does not show any deterioration in its performance over a long period of time.

[Brief explanation of drawings]

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

Claims (1)

[Claims] An ozone decomposition catalyst characterized in that an active substance having ozone decomposition ability is supported on a carrier containing MnO2 to a thickness of 5 to 100 μm.