JPH06320004A - Catalyst for decomposition of ozone - Google Patents

Abstract

(57) [Summary] [Objective] To provide a decomposition catalyst having an excellent ozone decomposing ability under high humidity reaction conditions. [Structure] Consists of MnO ₂ and MnCO ₃ , MnC
When the X-ray diffraction angle (2θ) of O ₃ is 31.4 °, Mn
An ozone decomposition catalyst, wherein the X-ray intensity of CO ₃ is 100 to 700 cps. [Effect] Excellent ozone decomposition effect under high humidity conditions.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art Hitherto, as a method for removing ozone which is a harmful component contained in a gas, an adsorption method using a porous substance such as activated carbon or zeolite, or an oxidative decomposition method using a catalyst such as MnO ₂ has been used. And so on.

[0003]

However, it is difficult to say that any of the conventional ozone removal methods described above is a sufficiently satisfactory method. That is, the adsorption method has a problem that since the adsorbent exhibits a limited adsorption capacity for a limited period of time, the adsorbent needs to be regenerated and the like, and a great deal of labor and resources are required for maintenance of the removing device.

Although the oxidative decomposition method of ozone using a catalyst does not have the above-mentioned problems, it is difficult to say that the catalyst performance is sufficiently satisfactory under the present circumstances, and the initial performance is good. However, there is a problem that it deteriorates with time during the reaction. In addition, there is a problem that the effect of humidity is great and the ozone decomposition rate is low under high humidity.

The present invention has been made in order to solve these problems that the conventional ozone removing methods have, and its object is to have an excellent ozone removing ability as compared with the conventional methods. At the same time, another object of the present invention is to provide an ozone decomposing catalyst which has excellent durability and can be used for a long period of time, and which is hardly affected by humidity.

[0006]

The ozone decomposing catalyst according to the present invention for achieving the above-mentioned object is MnO ₂ and MnC.
X-ray diffraction angle (2θ) of MnCO ₃ composed of O ₃
Is 31.4 °, the X-ray intensity of MnCO ₃ is 100 to
It is characterized by being 700 cps. The catalyst that can be used in the method of the present invention can be prepared by the following methods. (1) An aqueous solution prepared by dissolving a carbonate such as Na ₂ CO _{3 in an} Mn aqueous solution is added with stirring to obtain manganese carbonate or basic manganese carbonate. Filtration, washing with water, and repulping are repeatedly dried and then fired at 200 to 400 ° C. (2) TiO ₂ , Al ₂ O ₃ , SiO ₂ , TiO ₂ —S
Na ₂ CO was added to an Mn aqueous solution in which a carrier such as iO ₂ was dispersed.
An aqueous solution in which a carbonate such as ₃ is dissolved is added with stirring to add manganese carbonate or basic manganese carbonate to TiO ₂ , Al ₂
What is carried on O ₃ and SiO ₂ is obtained. Filtration, washing with water, and repulping are repeatedly dried and then fired at 200 to 400 ° C. (3) Pulverize and mix commercially available MnO ₂ powder and manganese carbonate powder with a ball mill or the like.

The shape of the catalyst used in the method of the present invention is not particularly limited, and various shapes such as honeycomb shape, pellet shape, columnar shape, plate shape, pipe shape and the like can be used. These can be manufactured by a kneading method, an impregnation method, a wash coating method, or the like. In the case of extrusion molding, a molding aid may be added to impart shapeability, or a reinforcing agent such as an inorganic fiber or an organic binder may be appropriately added to improve mechanical strength and the like. The amount of MnO ₂ and MnCO ₃ contained in these compacts was 30 wt%.
The above is preferable, and 50 wt% or more is more preferable. Thirty
If it is less than wt%, the ozone decomposing ability is significantly lowered. Further, the washcoat method of supporting catalytically active species and activated carbon on the surface of the catalyst is related to the present invention as described in the invention related to Japanese Patent Application No. 24-4843 already filed by the present inventors. From the viewpoint of reaction characteristics, a coat type catalyst is preferable, and the catalytically active species and activated carbon contained in the coat layer at this time are preferably 50 wt% or more, more preferably 75 wt% or more. If it is 50 wt% or less, the ozone decomposing ability is lowered. The catalytically active species supported on these carriers can be produced mainly by a washcoat method or the like. The thickness of these coats is preferably 5 to 10 μm,
10 to 50 μ is more preferable. If it is 5 μm or less, the decomposition activity decreases, and if it is 100 μm or more, the decomposition activity does not improve and only the pressure loss increases.

Since the catalyst according to the present invention does not deteriorate the ozone decomposing ability even under high humidity conditions, the relative humidity is 6%.
Most suitable for use under 0% or higher humidity conditions. Further, the catalyst of the present invention has an ozone concentration of 10 at room temperature.
The treatment of high-concentration ozone of ppm or more lowers the ozone decomposing ability, so that it is optimal for treatment of a gas containing ozone of 10 ppm or less. However, if the treatment is not continuous, it is possible to use the catalyst according to the invention to restore its activity during the rest period.

The reaction temperature at the time of ozone decomposition is 0 to 40 ° C.
Is preferable, and 10-30 degreeC is more preferable. This is because if the temperature is lower than 0 ° C., the reaction rate becomes slow, and if the temperature exceeds 40 ° C., it is uneconomical because heat energy for newly raising the temperature is required. Moreover, the contact between the catalyst and the reaction gas is
Area velocity of 5 to 70 (AV: area velocity
It is preferable to carry out y). This is because if the area velocity is less than 5, a large amount of catalyst is required, and if the area velocity exceeds 50, the efficiency is low and a predetermined decomposition rate cannot be obtained. Here, the area velocity is the space velocity (1 / H
r) is divided by the gas contact area per unit volume (m ² / m ³ ).

[0010]

EXAMPLES The present invention will be described in detail below based on examples. However, the present invention is not limited to the following examples. A. Preparation Example 1 of manganese nitrate catalyst _{(Mn (NO 3) 2 ·} 6H 2 O and MnO ₂
As 1kg and γ-Al ₂ O ₃ (Sumitomo Chemical A-11)
While stirring a slurry prepared by dissolving or dispersing 500 g in 10 l of ion-exchanged water, a 5 wt% Na ₂ CO ₃ aqueous solution was added until PH8 was reached, and MnCO ₃ was added to γ-Al _2.
Supported on O ₃ . This slurry was filtered and repulped with ion-exchanged water. After repeating this operation 5 times, 120
Dry for 18 hours at ℃, 250 ℃, 300 ℃, 350 ℃
Was calcined in air for 3 hours to obtain a catalyst.

[0011] MnO Example 2 manganese nitrate _{(Mn (NO 3) 2 ·} 6H 2 O)
As an aqueous solution of 1 kg dissolved in 10 l of ion-exchanged water, a 5 wt% Na ₂ CO ₃ aqueous solution was added to PH8 while stirring.
Was added until MnCO ₃ was obtained. The slurry was filtered, and a catalyst was obtained in the same manner as in Example 1 below.

Comparative Example 1 The MnCO ₃ obtained in Example 2 was dried at 150 ° C. for 3 hours.

Comparative Example 2 The MnCO ₃ obtained in Example 2 was calcined at 400 ° C. for 3 hours.

B. Loading of Catalyst on Cordierite Base Material The catalysts obtained in Example 1 and Example 2 and Comparative Example 1 and Comparative Example 2 were pulverized with a sample mill. To 400 g of the obtained catalyst powder, 500 ml of water and 50 g of Al ₂ O ₃ sol (A-10 manufactured by Nissan Chemical Industry Co., Ltd.) were added and stirred and mixed for 30 minutes to obtain a slurry for washcoat. Add 3 water to this slurry
After diluting by adding 00 ml, a previously prepared cordierite honeycomb (600 cells / inch ² ) was dipped to remove excess slurry and dried to obtain an ozone decomposition layer of 0.2 g /
Wash coat was repeated until a cc-honeycomb base material was obtained to obtain a honeycomb catalyst.

Reference Example While stirring and mixing 30 g of MnO ₂ having a specific surface area of 48 m ² / g and 70 g of a mixture of titanium tetrachloride and silica sol (TiO ₂ : SiO ₂ is 1: 1), ammonia gas is blown in. A neutralization reaction was performed to produce a slurry-like precipitate. After thoroughly washing the obtained precipitate with water, the temperature is adjusted to 50
Three-way catalyst MnO ₂ —TiO ₂ —SiO ₂ with a specific surface area of 162 m ² / g after firing at 0 ° C. for 3 hours and pulverization (weight ratio 35:
30:35) powder was obtained. Thereafter, in the same manner as in Example 1, SiO ₂ —MnO ₂ —TiO ₂ (weight ratio 35: 3).
A three-way catalyst supporting 0:35) at a supporting rate of 99% was obtained.

C. Catalytic activity test For the catalysts obtained in Examples 1 and 2, Comparative Examples 1 and 2 and Reference Example, a catalytic activity test was performed under the following reaction conditions using a test apparatus whose flow sheet is shown in FIG. Initially, the ozone decomposition rate was calculated after 10 hours and 100 hours. In the figure, (1) is an ozone generator, which generates ozone of an appropriate concentration from the air introduced therein, and guides this ozone-containing air to the catalyst layer (2). The ozone decomposition rate (%) is calculated by the following equation from the values at the inlet and outlet of the catalyst layer measured by the ozone analyzer in (3). (Reaction conditions) Area velocity: 50 m ³ / m ² · hr Inlet ozone concentration: 2 ppm Reaction temperature: 28 ° C. Relative humidity: 80% The above test results are shown in Table 1.

As is clear from the above table, Examples 1-9
Any of the catalysts obtained in Example 2 had a N content higher than that of the catalyst obtained in Comparative Example 1.
It has high durability in the presence of Ox and lower fatty acids. From the above test results, the catalyst according to the method of the present invention has high ozone decomposition performance and high durability in the presence of NOx and / or lower fatty acids.

[0018]

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

[0019]

[Brief description of drawings]

FIG. 1 is a flow sheet of a catalyst activity test.

[Explanation of symbols]

 (1) …… Ozone generator (2) …… Catalyst layer (3) …… Ozone analyzer

[Table 1]

Claims (1)

[Claims] In a catalyst that catalytically decomposes ozone in gas having a relative humidity of 60% or more, the catalyst is composed of MnO ₂ and MnCO _3, and the X-ray diffraction angle (2θ) of MnCO ₃ is 3
The X-ray intensity of MnCO ₃ at 1.4 ° is 100 to 70.
An ozone decomposition catalyst characterized by being 0 cps.