JPH03217234A - Production of catalyst for decomposition of ozone - Google Patents

Abstract

PURPOSE:To obtain a catalyst for catalytic decomposition of ozone contained in gas with high activity by impregnating an org. mercury compd. into a carrier and calcining the compd. at a temp. within a specified range after drying. CONSTITUTION:A molded body contg. an element such as Ti or Si is formed and manganese dioxide or other manganese oxide is supported on the molded body to obtain a carrier. An org. mercury compd. such as mercury lactate or mercury citrate is impregnated into the carrier, dried and calcined at 150-300 deg.C. When the resulting catalyst is used in catalytic decomposition of ozone contained in gas, the ozone is decomposed with high activity and the occurrence of environmental problem is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for producing an ozone decomposition catalyst, and more particularly to a method for producing a catalyst for catalytically decomposing ozone contained in a gas.

[Prior Art] Ozone has a strong oxidizing ability, and it is also used for deodorization and sterilization because it turns into harmless oxygen through a decomposition reaction. It is widely used in various fields for purposes such as bleaching.

However, if unreacted ozone is released into the atmosphere, not only will the odor cause discomfort, but if the concentration exceeds a certain level, it will begin to attack the respiratory system, so even if it is in a small amount, it should not be inhaled for a long time. is extremely harmful to the human body.

Particularly in recent years, indoor pollution due to ozone generated from various high-voltage generators such as dry-type copying machines has been pointed out, and from the viewpoint of environmental hygiene, it is desired to establish a technology that decomposes and removes waste ozone and renders it harmless. There is.

Conventional waste ozone treatment methods include (I) treatment method using activated carbon, (II) treatment method using chemical cleaning, (
II+) A treatment method using thermal decomposition, (IV) A treatment method using an ozone decomposition catalyst, etc. are known.

Treatment methods using activated carbon are used to treat low concentrations of ozone, but due to the reaction mechanism between activated carbon and ozone, the activated carbon is quickly oxidized and consumed, resulting in a short service life and the hassle of having to replace the activated carbon frequently. There is. Furthermore, when treating high concentrations of ozone, there is a risk of the activated carbon itself igniting and burning due to the heat of reaction, which poses a problem in handling.

The treatment method using chemical cleaning is a method of cleaning waste ozone with an aqueous solution containing reducing substances, but the treatment cost is high and
The problem of wastewater treatment also arises.

The treatment method using thermal decomposition requires 300%
This method requires heating to a temperature higher than 0.degree. C., and has the disadvantage that heating costs are high in order to treat a large amount of exhaust gas, which increases the processing cost.

On the other hand, the treatment method using an ozone decomposition catalyst is said to be the most advantageous method for ozone decomposition because there is no danger of ignition and explosion, no waste water treatment is required, and ozone can be decomposed and removed at low cost.

Various technologies have been developed as ozone decomposition catalysts, but the catalyst disclosed in JP-A No. 62-97643 is an ozone decomposition catalyst with excellent characteristics, and is While catalysts require high-temperature heating, the above-mentioned catalysts have been put into practical use as ozone decomposition catalysts that can be used even at room temperature by increasing their low-temperature activity. However, in recent years, environmental problems have attracted particular attention, and there has been a demand for ozone decomposition catalysts that have significantly higher activity than conventional products.

[Problems to be Solved by the Invention] The present invention has been made in view of the above circumstances, and provides a method for producing a highly active ozone decomposition catalyst for catalytically decomposing ozone contained in gas. The purpose is to provide

[Means for Solving the Problems] The ozone decomposition catalyst of the present invention that achieves the above object is characterized in that a carrier is impregnated with organic silver, dried and then calcined at 150 to 300°C.

Further, if a molded body containing one or more elements selected from the group consisting of Ti, Si, Al, Mg, and Zr and/or manganese oxide is prepared and used as the above-mentioned carrier, the catalyst of the catalyst body can be further improved. Performance can be improved.

[Function] The inventors of the present invention have conducted intensive research on the production method of an ozone decomposition catalyst formed by supporting silver, and have found that the conventional catalyst preparation method does not fully utilize the catalytic ability of silver The present invention was conceived based on the knowledge that it is possible to further increase the activity of an ozone decomposition catalyst depending on the method.

Although the reason why the method of the present invention produces good results is not completely understood, it is speculated as follows. Conventional ozone decomposition catalysts generally use silver nitrate to support silver. However, the decomposition temperature of silver nitrate is 444
℃, and when preparing the catalyst, it is necessary to calcinate at a higher temperature range. As a result of this, silver aggregates and its degree of dispersion becomes low, so that silver cannot work effectively and it is thought that it is difficult to improve the activity.

On the other hand, when using organic silver, the decomposition temperature of organic silver is generally low, so it is possible to sinter at a lower temperature, which increases the degree of silver dispersion and is thought to lead to high activity. It will be done.

The organic silver used in the present invention may have a decomposition temperature of less than 300° C., and the type thereof is not limited. Silver salts of organic acids, chelate compounds and complexes containing silver, etc. are used. Among these, organic acid silver is particularly preferred, and examples of the organic acid silver include silver lactate, silver malate, silver succinate. Examples include silver tartrate and silver glycolate, and the decomposition temperature is, for example, 175°C for silver lactate and 180°C for silver acetate.

In the present invention, the firing temperature after impregnating and drying organic silver is preferably 150°C or more and 300°C or less. If the firing temperature is less than 150°C, it will be difficult to decompose the organic silver, while if it exceeds 300°C, silver will tend to agglomerate and the degree of dispersion of silver will deteriorate, which is not desirable.

The amount of silver supported in the present invention is preferably 0.1% by weight or more and 10% by weight or less. If the supported amount is less than 0.1% by weight, the activity will be insufficient.

On the other hand, if it exceeds 10% by weight, it is undesirable because the activity decreases and costs increase.

In addition to manganese dioxide, manganese oxides include Mn○. M
n203, Mn. , o4, etc., but it is preferable to use manganese dioxide from the viewpoint of catalytic activity.

Since moldability is poor when using manganese oxide alone during catalyst production, it is recommended that manganese oxide be supported on a molded body made of an inorganic compound, which will be described later.

In the present invention, inorganic compounds that can be used to create a molded body containing one or more elements selected from the group consisting of Ti, Si, Al, Mg, and Zr include titania. silica. Silica alumina, alumina, zirconia. Zeolite, diatomaceous earth. Common compounds such as magnesium silicate. If one or more of these are optionally used, the moldability during production can be improved, but in particular binary composite oxides consisting of Ti and Si and ternary composite oxides consisting of Ti, St and Zr. Composite oxides are recommended in terms of moldability and ozone decomposition performance.

The catalyst of the present invention is not particularly limited by its shape, and may be honeycomb-shaped, cylindrical, or plate-shaped. Ribbon-like, corrugated plate-like. An appropriate one may be selected from integrally molded shapes such as a pipe shape, a donut shape, and a lattice shape.

Next, the most preferred method for preparing the catalyst of the present invention will be described, but the present invention is not limited to the following method.

First, a binary composite oxide (hereinafter T
A molding aid is added to the powder (referred to as i02-Si02), mixed and kneaded while adding an appropriate amount of water, and molded into a pellet or honeycomb shape using an extruder. 50-20 molded items
After drying at 0°C, 300-800°C, preferably 35
The product is fired at 0 to 600° C. for 1 to 10 hours, preferably 2 to 6 hours under air circulation to obtain a molded body made of Ti02-Si02. The molded body is impregnated with a manganese nitrate aqueous solution to support manganese nitrate on the molded body, and then dried and fired to form manganese dioxide and Tie2-SiO. A molded body consisting of the following is obtained. Subsequently, a silver lactate aqueous solution was added to the molded body for 40~
After being impregnated and supported while heating at 50°C, drying,
A finished catalyst can be obtained by calcination.

[Example] Example! A composite oxide consisting of titanium and silicon was prepared by the method described below.

First, add 28 ml of ammonia water (NH, 25%) to 40 fl of water.
ft and add Snowtech NCS-30 to this.
(Silica sol manufactured by Nissan Chemical, approx. 30% by weight as Sin2)
(containing) 2.4 κg was added. A titanium-containing aqueous sulfuric acid solution prepared by diluting a sulfuric acid aqueous solution 15.3j2 of titanyl sulfate having the following composition with water 301 was gradually dropped into the obtained solution while stirring, and Ti02 and Sin. A co-precipitated gel was produced.

T i O S O 4 2 5 0 g / 1
(T i O 2 conversion) Total H2SO4 1100g
/u Tie2-S obtained by further standing still for 15 hours
The i02 gel was filtered, washed with water, and then dried at 200° C. for 10 hours. Then, it was fired at 550° C. for 6 hours in an air atmosphere. The composition of the powder obtained by firing is TiO2:SiO2=
4:1 (molar ratio), and the BET surface area is 1 8 5
It was 27g. The above powder will be referred to as TS-1 hereinafter, and an ozone decomposition catalyst was prepared using this TS-1 by the method described below.

First, the above TS-1 powder 1. Add 20g of microcrystalline cellulose [manufactured by Asahi Kasei Industries, Ltd., trade name: Avicel] together with an appropriate amount of water to O kg, mix and knead well with a kneader, and then extrude into pieces with a diameter of 3.0mm and a length of 3.0mm. 0mm
Tie2-Sin2
A pellet molded body consisting of the following was obtained.

Next, 190 g of the pellet molded body was placed in an evaporating dish, and 200 cc of a silver lactate aqueous solution containing 10 g of Ag was added.
After thoroughly mixing and impregnating, it was concentrated to dryness on a dry bath at 120%
It was dried at ℃ for 5 hours. Further, the catalyst was fired in an electric furnace at 250° C. for 3 hours in an air atmosphere to obtain a completed catalyst. The composition of the obtained catalyst was Ag:TS-1=5:95 (weight ratio), and the ozone decomposition rate was determined by the following method.

A Pyrex reaction tube with an inner diameter of 20 mm was filled with 10.5 cc of the above pellet-shaped catalyst, and air containing 10 pp+n of ozone was introduced into the catalyst layer at a flow rate of 0.525 8 m/Hr (space velocity 50,000 Hr-'). The ozone decomposition rate at a reaction temperature of 20°C was determined. The results are shown in Table 1.

A catalyst was prepared in the same manner as in Example 1 except that activated alumina was used instead of TS-1 in Example 1, and the ozone decomposition rate was determined. The results are shown in Table 1. The composition of the obtained catalyst was Ag:Al2 03 =5 +95 (
weight ratio).

Example 3 A catalyst was prepared in the same manner as in Example 1 except that zeolite was used instead of TS-1 in Example 1,
The ozone decomposition rate was determined. The results are shown in Table 1. The composition of the obtained catalyst was Ag:zeolite=5:95 (weight ratio).

Example 4 A catalyst was prepared in the same manner as in Example 1 except that manganese dioxide was used instead of TS-1 in Example 1, and the ozone decomposition rate was determined. The results are shown in Table 1. The composition of the obtained catalyst was Ag+Mn02 =5:95
(weight ratio).

Comparative Example 1 Tie. obtained in Example 1. An ozone decomposition catalyst was prepared by the following method using a pellet molded body made of -Sin2.

First, 190 g of the pellet molded body was placed in an evaporating dish, 200 cc of a silver nitrate aqueous solution containing 10 g of Ag was added, and the mixture was sufficiently mixed to impregnate the body, and then concentrated to dryness on a dry bath at 120°C.
It was dried for 5 hours. The catalyst was then calcined in an electric furnace at 450° C. for 3 hours in an air atmosphere, and the ozone decomposition rate was determined.

The results are shown in Table 1. The composition of the obtained catalyst was Ag:T.
S-1=5:95 (weight ratio).

Table 1 Example 5 Add an appropriate amount of water to 10 kg of the TS-1 powder obtained in Example 1, mix well in a seconder, knead further, and then use an extruder to mold the powder to a size of 50 mm in length and 50 mm in width. 50mm, length 100
A lattice-like honeycomb (wall thickness 0.2 mm, opening 1.2 mm) was formed and dried at 150°C for 5 hours.
It was baked at 300° C. for 2 hours in an air atmosphere. The lattice honeycomb thus obtained was impregnated with an aqueous manganese nitrate solution, dried at 120°C for 3 hours, and fired at 450°C for 3 hours. The lattice-shaped honeycomb supporting MnO2 in this manner was impregnated with an aqueous silver lactate solution, dried at 120°C for 3 hours, and then calcined at 250°C for 3 hours to obtain a completed catalyst.

The composition of the obtained catalyst was Ag:Mn02:TS1
=3:17:80C weight ratio), and the ozone decomposition rate was determined by the following method.

A Pyrex reaction tube is filled with a lattice honeycomb catalyst,
Air containing 10 ppm ozone at a flow rate of 2 5 8 m3
/}Ir (space velocity 100,000 Hr-') was introduced into the catalyst layer, and the ozone decomposition rate at a reaction temperature of 25°C was determined. The results are shown in Table 2.

Example 6 A catalyst was prepared in the same manner as in Example 5, except that a silver citrate aqueous solution was used instead of the silver lactate aqueous solution used in Example 5 to support Ag, and the ozone decomposition rate was determined.

The results are shown in Table 2. The composition of the obtained catalyst was Ag:M
n02:TS-1=3;17:80 (weight ratio).

Example 7 A catalyst was prepared in the same manner as in Example 5 except that the supported amount of Ag was changed from 3% by weight to 6% by weight, and the ozone decomposition rate was determined. The results are shown in Table 2. The composition of the obtained catalyst is Ag
+ MnO2: TS 1 =6: 16.5
: 77.5 (weight ratio).

Comparative Example 2 The MnO2-supported lattice honeycomb obtained in Example 5 was impregnated with a silver nitrate aqueous solution instead of a silver lactate aqueous solution, and 12
After drying at 0°C for 3 hours, it was calcined at 450°C for 3 hours to obtain a catalyst, and the ozone decomposition rate was determined. The results are shown in Table 2.

The composition of the obtained catalyst was Ag:MnO2:TS-1
=3:17:80 (weight ratio).

Table 2 From the experimental results shown in Tables 1 and 2, the ozone decomposition catalyst produced by the production method of the present invention has a much higher ozone decomposition ability than the conventional catalyst impregnated with Ag using a silver nitrate aqueous solution. I understand.

[Effects of the Invention] Since the present invention is configured as described above, it is possible to provide a method for producing a highly active ozone decomposition catalyst for catalytically decomposing ozone contained in gas.

Claims (4)

[Claims] (1) Impregnate the carrier with organic silver, and after drying, the
A method for producing an ozone decomposition catalyst, which comprises firing at ℃. (2) A method for producing an ozone decomposition catalyst, which comprises creating a molded body containing manganese oxide, impregnating the molded body with organic silver, drying, and then firing at 150 to 300°C. (3) After creating a molded body containing one or more elements selected from the group consisting of Ti, Si, Al, Mg, and Zr, the molded body is impregnated with organic silver, and after drying,
A method for producing an ozone decomposition catalyst, which comprises firing at 300°C. (4) After creating a molded body containing one or more elements selected from the group consisting of Ti, Si, Al, Mg, and Zr and manganese oxide, impregnating the molded body with organic silver, A method for producing an ozone decomposition catalyst, which comprises firing at 150 to 300°C after drying.