JPH0263552A - Ozonolysis catalyst - Google Patents

Abstract

PURPOSE:To enhance the low-temp. activity and heat resistance of the title ozonolysis catalyst by forming the catalyst from a first component consisting of the oxide of the element selected from Ti, Si, Al, etc., and a second component selected from manganese oxide, trimanganese tetroxide, etc. CONSTITUTION:An appropriate amt. of water is added to the powder consisting of the double oxides of Ti and Si along with a molding assistant, mixed, and kneaded. The kneaded material is molded by an extruder in the form of pellets, honeycombs, etc. The molded product is dried at 50-250 deg.C, and then calcined at 300-800 deg.C for 1 to 10hr under the circulation of air to obtain a TiO2-SiO2 molded body. The molded body is impregnated with an aq. manganate soln. to deposit the manganate on the body. The product is dried at 50-150 deg.C, then calcined at 300-800 deg.C, and further reduced with hydrogen at 150-800 deg.C for 1-10hr to produce an ozonolysis catalyst.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to an ozone decomposition catalyst that catalytically decomposes ozone contained in gas to render it harmless. More specifically, the present invention relates to an ozone decomposition catalyst that has excellent low-temperature activity and durability.

<Conventional technology and its problems> Ozone has strong oxidizing ability and becomes harmless oxygen when decomposed, so it is widely used in various fields for purposes such as de-fox sterilization, bleaching, and reducing COD in wastewater. ing.

However, some of the ozone used in the treatment is released into the atmosphere unreacted, which may cause secondary pollution such as photochemical smog. Also, the smell of ozone is 1pp
It can be detected at concentrations below 2 ppm, and at concentrations above 2 ppm it causes irritation to the respiratory system and is harmful to the human body.

For example, when an aircraft flies in the stratosphere, there is a risk that ozone-containing air may enter the cabin and have an adverse effect on passengers and crew. Furthermore, recently, ozone is generated from devices that incorporate high-voltage generators such as dry copying machines, and since these devices are mainly placed indoors, the amount of ozone generated is ff1ffl.
However, it has become a problem because indoors can be contaminated.

It is necessary to remove ozone mixed in or emitted from these various sources and render it harmless.

Conventionally used waste ozone treatment techniques include an activated carbon method, a chemical cleaning method, and a thermal decomposition method.

The activated carbon method is used to treat low-concentration ozone, but the activated carbon is consumed as ozone decomposition progresses, so it needs to be replenished, and when treating high-concentration ozone, the activated carbon itself is destroyed by the heat of reaction. There are problems in handling as there is a risk of ignition and combustion.

In the chemical cleaning method, waste ozone is cleaned with an aqueous solution of a reducing substance, so the treatment cost is high and problems arise in wastewater treatment.

The thermal decomposition method requires heating to 300° C. or higher in order to increase the decomposition efficiency, and has the disadvantage that heating costs are required to process a large amount of exhaust gas, which increases the processing cost.

On the other hand, in recent years, research has been conducted on the catalytic decomposition method as a waste ozone treatment method.This method has no risk of ignition or explosion, does not require wastewater treatment, and can decompose and remove ozone at low cost, making it an advantageous method. has been done.

As ozone decomposition catalysts, catalysts using oxides such as nickel, manganese, and cobalt exhibit excellent decomposition efficiency (Japanese Patent Laid-Open No. 60-97049). However, as a practical catalyst, a catalyst that exhibits high activity in an even lower temperature range is required.

<Problems to be Solved by the Invention> An object of the present invention is to provide an inexpensive ozone decomposition catalyst with excellent low-temperature activity and durability for catalytically decomposing ozone contained in gas into oxygen. It is in.

Means for Solving the Problems> As a result of intensive research, the present inventors have discovered an ozone decomposition catalyst that satisfies the above objectives.

That is, the present invention provides an oxide of at least one element selected from the group consisting of titanium, silicon, aluminum, and zirconium as a catalyst A component, and manganese oxide (II) as a catalyst B component.
), trimanganese tetroxide and manganese oxide (II+
) An ozone decomposition catalyst comprising at least one selected from the group consisting of:

It is. The catalyst of the present invention has f! low temperature activity and durability. i
It exhibits excellent ozone decomposition performance even in the low temperature range of 10 to 20°C, preferably 0 to 20°C. Furthermore, the catalyst of the present invention is inexpensive.

The present inventors have discovered that although sufficient ozone decomposition performance cannot be obtained with catalyst A component alone or catalyst B component alone, a catalyst containing both catalyst A component and catalyst B component has significantly improved ozone decomposition performance. It was found that it has excellent low-temperature activity and durability.

The composition of each catalyst component is as follows: Catalyst A component is 40~
It is preferable that the catalyst B component contains 95% by weight and 5 to 60% by weight, especially if the catalyst B component is out of this range, the ozone decomposition performance will decrease, and if it exceeds 60% by weight, it will be economical. It is also disadvantageous.

Furthermore, in the case where the catalyst A component in the catalyst of the present invention is a composite oxide of at least two elements selected from the group consisting of titanium, silicon, and zirconium, these composite oxides have strong solid acidity and a large BET surface area. It is more preferable in terms of catalytic activity, catalyst moldability, strength stability, etc.

The catalyst of the present invention can be prepared in a variety of ways. For example, (a) an appropriate amount of water is added to a powder made of a composite oxide of titanium and silicon together with a molding aid, the mixture is mixed and kneaded, and the mixture is molded into a pellet shape or honeycomb shape using an extrusion molding machine.
After drying at ~250°C, it is fired at 300~800°C for 1~10 hours under air circulation to obtain a TiO□-5in2 molded body. Next, the molded body is impregnated with an aqueous solution of manganese salt, supported, dried at 50 to 150°C, fired at 300 to 800°C, and then subjected to hydrogen reduction at 150 to 800°C for 1 to 10 hours to obtain the present invention. of the catalyst.

(b) In the method of (a) above, TiO□-5iOz
After impregnating the molded body with an aqueous solution of manganese salt and drying it, it is impregnated with an ethanolamine aqueous solution instead of hydrogen reduction, dried at 50 to 150°C, and then heated to 200 to 600°C.
1. The catalyst of the present invention is obtained by calcination under air flow for ~10 hours.

(c) In the method of (a) above, Ti0z 5if
The T-molded body is impregnated with an aqueous solution of manganese salt, supported, dried, and then subjected to hydrogen reduction without calcination to obtain the catalyst of the present invention.

(d) A mixed powder consisting of a composite oxide of TE01 and SiO□ and trimanganese tetroxide is molded into a pellet shape, honeycomb shape, etc. in the same manner as in (a) to obtain the catalyst of the present invention.

Although the catalyst preparation method has been specifically shown above, the present invention is not limited thereto. The shape of the catalyst is appropriately selected from pellet, honeycomb, columnar, cylindrical, plate, ribbon, corrugated plate, vibrator, donut, lattice, and integrally molded shapes.

<Examples> The present invention will be described in detail below with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples.

Practical JL Example - A composite oxide consisting of titanium and silicon was prepared by the method described below.

A commercially available sulfuric acid aqueous solution of titanyl sulfate having the following composition was used as a titanium source.

Ti0SO4 (TiO□ conversion) 250g/Q
Total t (zS041100 g/Q Separately, 25% by weight ammonia water 28Q was added to water 402, and Snowtex-NC3-30 (silica sol manufactured by 8 San Kagaku, containing approximately 30% by weight as SiO□) 2.4
kg was added. A diluted solution of 15.3Q of the titanyl sulfate sulfuric acid solution added to 30Q of water was dropped into the resulting solution while stirring to form a coprecipitated gel. It was left undisturbed for 15 hours. The thus obtained TiO□−
The 5iO□ 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 obtained powder was TiO□:Si0□=4:1
(molar ratio), the BET surface area was 185 m2/g (hereinafter, this powder will be referred to as TS-1).

Add an appropriate amount of water to 10 kg of TS-1 powder, and add it to the kneader.
The mixture was thoroughly mixed using a kneading machine, formed into a pellet shape, dried at 150°C for 5 hours, and then fired at 300°C for 2 hours in an air atmosphere. °Next, the obtained pellet was impregnated with an aqueous manganese nitrate solution, dried at 120°C for 3 hours, then calcined at 450°C for 3 hours, and then
A completed catalyst was obtained by hydrogen reduction at 0°C for 4 hours under a nitrogen atmosphere containing 10% hydrogen.

The manganese content in the finished catalyst is 12.
It was 5% by weight. From the X-ray diffraction analysis results, Mn is trimanganese tetroxide ()ln30a) and manganese oxide (]
It was a mixture of I[) (MnJ*).

1.2 Using the TS-1 powder obtained in Example 1, Example 1
It was molded into a pellet shape in the same manner as above, impregnated with manganese nitrate, dried at 120°C for 3 hours, and fired at 450°C for 3 hours. Thereafter, it was impregnated with an 8% by weight aqueous ethanolamine solution, dried at 120°C for 3 hours, and then heated at 450°C for 2 hours.
A completed catalyst was obtained by calcination for a period of time.

The manganese content in the finished catalyst is 12.
It was 5% by weight. According to the X-ray diffraction analysis results, Mn consists of trimanganese tetroxide (Mn: +0.t) and manganese oxide (
Ilt) (Mnz03).

Using the TS-1 powder obtained in Example 1, Example 1
It was molded into a pellet shape in the same manner as above, impregnated with manganese nitrate, dried at 120°C for 3 hours, and then reduced with hydrogen at 400°C for 4 hours in a nitrogen atmosphere containing 10% hydrogen to obtain a completed catalyst.

The manganese content in the finished catalyst is 12.
It was 5% by weight. According to the X-ray diffraction analysis results, Mn is composed of trimanganese tetroxide (Mn304) and manganese oxide (II
I) (MnzC1+).

Support 1 Commercially available γ-alumina pellets were impregnated with manganese nitrate,
It was dried at 120°C for 3 hours and then fired at 450°C for 3 hours. Thereafter, hydrogen reduction was performed at 400° C. for 4 hours in a nitrogen atmosphere containing 10% hydrogen to obtain a completed catalyst.

The manganese content in the finished catalyst is 12.
It was 5% by weight. According to the results of X-ray diffraction analysis, Mn is composed of trimanganese tetroxide (Mn30J) and manganese oxide (]II
) (Mnz03).

Mitate 5 A completed catalyst was obtained in the same manner as in Example 4, except that hydrogen reduction was carried out at 800° C. for 4 hours in a nitrogen atmosphere containing 10% hydrogen.

The manganese content in the finished catalyst is 12.
It was 5% by weight. According to the results of X-ray diffraction analysis, Mn was manganese(II) oxide (MnO).

Measurement of Ratio - A completed catalyst was obtained in the same manner as in Example 1, except that the hydrogen reduction treatment was omitted.

The manganese content in the finished catalyst is 12.
It was 5% by weight. According to the results of X-ray diffraction analysis, Mn was manganese(II) oxide (MnO□).

A completed catalyst was obtained in the same manner as in Example 4, except that the hydrogen reduction treatment was omitted for the first time.

The manganese content in the finished catalyst is 12.
It was 5% by weight. According to the results of X-ray diffraction analysis, Mn was manganese(II) oxide (MnO□).

Round 1 The ozone decomposition rate of each catalyst obtained in Examples 1 to 5 and Comparative Example 1.2 was measured by the following method, and the results shown in Table 1 were obtained. In addition, the ozone decomposition rate in the examples was determined by the following formula from the results of measuring the ozone concentration in the air at the inlet and outlet of the catalyst layer.

Ozone decomposition rate 0ω = Pyrex reaction tube with an inner diameter of 20 mm and a diameter of 3. 0mm
, long 3. Filled with 10.5 cc of catalyst in the form of a pellet of 0 mm diameter, air containing TOPPM of ozone was added to 0.5 cc of catalyst. 315
Flow rate of N m3/hr (space velocity 30000hr''''
) was introduced into the catalyst layer, and the ozone decomposition rate at a reaction temperature of 2°C was determined.

Using a pellet-shaped catalyst made of trimanganese tetroxide (Mn3oa), the reaction ozone decomposition rate was measured according to Example 6, and the results shown in Table 1 were obtained.

Using a pellet-shaped catalyst consisting of manganese oxide (Ill) 04n, 03), the reaction and ozone decomposition rate were measured according to Example 6, and the results shown in Table 1 were obtained.

Table-1

Claims (1)

[Scope of Claims] 1 Catalyst A component is an oxide of at least one element selected from the group consisting of titanium, silicon, aluminum and zirconium, and catalyst B component is manganese oxide (
II), trimanganese tetroxide, and manganese (III) oxide. 2. The ozone decomposition catalyst according to claim 1, comprising 40 to 95% by weight of catalyst A component as an oxide and 5 to 60% by weight of catalyst B component. 3. The ozone decomposition catalyst according to claim 1 or 2, wherein the catalyst A component is a composite oxide of at least two elements selected from the group consisting of titanium, silicon, and zirconium.