JPH03114540A - Catalyst for ozone decomposition - Google Patents

Abstract

PURPOSE:To obtain a catalyst which decomposes ozone in air even at a low temperature close to room temperature by using Ni (III) oxide, Ni2O3, as the ozone decomposing catalyst. CONSTITUTION:A particle growth suppressing agent such as for colloidal silica, alumina, etc., is added to an aqueous solution of water-soluble nickel salt such as nickel nitrate, nickel carbonate, etc., so as to raise the specific surface area of the nickel salt to about 100-250m<2>/g. Then, the solution is dried and fired to give Ni (III) oxide, Ni2O3. A catalyst prepared in this way stably decomposes ozone even at a temperature from room temperature to relatively low temperature such as about 350 deg.C for a long duration when the catalyst is brought into contact with ozone-containing air.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a catalyst capable of decomposing ozone in the air at low temperatures around room temperature.

[Conventional technology]

It has been confirmed that ozone has both good and bad effects on living organisms. In other words, ozone's strong oxidizing ability sterilizes
Ozone is useful for disinfection and is widely used in fields such as medicine and food, but on the other hand, due to the toxicity of ozone itself,
The concentration in the air is 0. If it exceeds lppm, it will irritate the respiratory system, and if it exceeds 50ppm, it will be life-threatening.

Therefore, among air pollutants, ozone is one of the most powerful harmful substances for living organisms.Especially in recent years, with the spread of office equipment that generates ozone such as electrostatic copying machines, the causes of ozone generation have increased. Therefore, it has become desirable to develop a simple ozone decomposition method.

Conventional ozone treatment techniques include an activated carbon adsorption decomposition method, a thermal decomposition method, a wet method, and a catalytic decomposition method. Among these methods, the activated carbon adsorption and decomposition method utilizes a chemical reaction with activated carbon, so activated carbon is a consumable item and running costs are high. Furthermore, there is a risk of twisting or explosion due to reaction heat when processing high concentration ozone, and ozone accumulation when processing low concentration ozone. In the thermal decomposition method, it is necessary to hold the waste gas at 300 to 400°C for about 1 second, and there is a problem in that the running cost is too high to treat a large amount of exhaust gas.

The wet method is suitable for large air volumes, but it is not suitable for small-scale implementation because the chemicals used for decomposition and equipment construction costs are high, and waste liquid treatment is also required. On the other hand, decomposition using a catalyst has attracted attention in recent years because it has many advantages, such as there is no danger of twisting or explosion, it can be decomposed at a lower temperature than thermal decomposition, and it can be easily implemented on a small scale. are collecting.

Various ozone decomposition catalysts have been proposed in the past, but among the nickel-based ones, Ni (Japanese Unexamined Patent Publication No. 567082
No. 3), N1p- (Ti or P oxide) (Unexamined Japanese Patent Publication No. 6
2-132546), Ni0-Mn02-Coo.

(Japanese Unexamined Patent Publication No. 60-97049) and N1p supported on an inorganic fibrous carrier (Japanese Unexamined Patent Publication No. 62-201648).

[Problem to be solved by the invention]

An object of the present invention is to provide a novel ozone decomposition catalyst that exhibits excellent ozone decomposition ability even at low temperatures around room temperature.

[Failure to solve the problem]

The ozone decomposition catalyst provided by the present invention consists of N1(I[[) oxide/Ni2O3.

As Ni203 for this catalyst, one having a specific surface area of approximately 20 m2/g or more is suitable, but it is desirable that the specific surface area is as large as possible;
The most preferable one is about 0 m''/g.

Ni□03, which has a large specific surface area, is treated with an aqueous solution of a water-soluble nickel salt such as nickel nitrate, nickel carbonate, or nickel acetate, and preferably with colloidal silica, alumina, titania, etc. as a grain growth inhibitor to increase the specific surface area. After drying at a temperature of 80 to 120°C, the added state is dried at a temperature of about 200 to 400°C for 1 to 10 hours, preferably about 2 to 120°C.
It can be obtained by firing in the air for 6 hours, but it can be used for porcelain, earthenware,
Commercially available pigments for use in coloring glass, catalysts for organic synthesis, raw materials for producing nickel compounds, and the like may be used.

N i,o is used for ozonolysis by being supported on a suitable carrier depending on the method of use, but particularly preferred carriers are:
For example, it is an inorganic fibrous paper with high porosity or a honeycomb structure made of it, as described in Japanese Patent Application Laid-Open No. 59-10345. A carrier having a honeycomb structure can efficiently treat a large amount of air to be treated with low pressure loss, and is excellent as a carrier for a catalyst that treats air containing low concentration ozone. A preferred honeycomb structure is
Effective surface area 8-40 cm2/cm3 (particularly preferably 20-40 cm2/cm'), aperture ratio 50-90% (
Particularly preferably 50 to 70%).

To support N i203 on a carrier, a suspension of N i203 is mixed with an inorganic binder such as silica sol, alumina sol, titania sol, or a mixture thereof, and an organic binder such as polyvinyl alcohol, vinylidene chloride,
An acrylic emulsion or the like may be applied to a carrier by impregnation or coating, and then dried. Alternatively, the carrier is impregnated with a precursor of Ni203, such as nickel nitrate, dried, and then calcined under Ni2O3 producing conditions to produce Ni203 on the carrier.

The catalyst of the present invention decomposes ozone with high efficiency when brought into contact with ozone-containing air. The usable temperature is room temperature to about 350°C, and it is particularly excellent in that it exhibits strong catalytic action even at low temperatures around room temperature.

〔Example〕

Hereinafter, the present invention will be explained with reference to Examples.

Example 1 Paper with a thickness of 0.2 mrQ was made using ceramic fibers (average fiber diameter 3 μm, fiber length 10 mm) consisting of 5i0250% and A1□0.50%, and a flat paper and a corrugated paper were made. By stacking the cells alternately and gluing the contacts with an acrylic binder, the number of cells is 205.
/ 1112, a honeycomb structure carrier with an aperture ratio of 67% was obtained.

Separately, N i2o 3 powder with a specific surface area i 90 m2/g obtained by heat treating nickel nitrate was stirred in water with a vinylidene chloride binder of 1/1 Offi to make a slurry, and the honeycomb structure carrier was added thereto. was immersed for 5 minutes and then dried at 105°C for 3 hours to carry 200 kg/m3 of Ni203.

Example 2 A N i20 powder with a specific surface area of 190 m27 g obtained by heat treating nickel nitrate was made into a slurry with 1/2 the amount of colloidal silica, and the same honeycomb structure carrier as produced in Example 1 was added thereto. was soaked for 5 minutes. After lifting from the slurry, the carrier was heated to 105°C.
It was dried for 3 hours to carry 200 kg/m'' of Ni203.

Example 3 Paper with a thickness of 0.2 mm and an interfiber porosity of 94% was made from E-glass fibers (fiber diameter 9 μm, fiber length 10 mm), and Ni203 powder with a specific surface area of 190 m2/g and 1/lO of it were made. A slurry containing a certain amount of vinylidene chloride binder was applied and dried. The obtained coated paper is made of Ni2O
3 was carried at 150 g/m2. A portion of this coated paper is corrugated, and the corrugated paper and unprocessed flat paper are alternately layered and bonded with a binder at the contact points of the two, resulting in a cell count of 2057 in2.
A honeycomb structure with an aperture ratio of 67% was used.

Comparative Example 1 The same honeycomb structure carrier as produced in Example 1 was immersed in a slurry containing a known ozone decomposition catalyst NiO and a vinylidene chloride binder in an amount of 1/10 of the known ozone decomposition catalyst NiO.
It was dried at ℃ for 3 hours and loaded with 200 kg/m3 of NiO.

Comparative Example 2 The same honeycomb structure carrier produced in Example 1 was treated with a known ozone decomposition catalyst M no 2-A I203-Cu
o-Ce.

It was immersed in a slurry containing powder of composite oxide (weight ratio 70:15:12:1) and a vinylidene chloride binder in an amount of 1/10 of the powder, and then dried at 105°C for 3 hours. m3 was supported.

Comparative Example 3 The same honeycomb structure carrier as produced in Example 1 was immersed in a slurry containing activated carbon with a specific surface area of 1300 m''/g and a vinylidene chloride binder in an amount of 1/10 of the activated carbon, and then dried at 105°C for 3 hours. , activated carbon at 200 kg/m3
carried it.

Test Example The ozone decomposition ability of the ozone decomposition catalysts obtained on each side above was investigated using the following method.

Test method: Ozone-containing air obtained by treating dehumidified air with a silent discharge ozone generator is diluted with clean air to adjust the ozone concentration to 1.5 ppm to prepare a gas to be treated.

This gas was transferred to a reaction tube with an inner diameter of 80 mm and a cross-sectional area of 0.0283 m2 at a catalyst loading part at a temperature of 2000 m2. Wind speed 1.5
m/s, wind Ik15.3 m'/hr (space velocity 27
1, OOO/hr). Sample the gas before and after passing through the catalyst loading section, and measure the ozone concentration using an ultraviolet absorption ozone concentration meter. In addition, the catalyst was prepared so that the cell opening surface of the honeycomb structure carrier was perpendicular to the ventilation direction.
Load one with a thickness of 20 mm in the ventilation direction. From the ozone concentration measurement results, the ozone decomposition rate is calculated using the following formula.

The test results are shown in FIGS. 1 to 3. From the results shown,
It can be seen that the catalyst of the present invention has excellent room temperature ozone decomposition ability and is also excellent in durability.

〔Effect of the invention〕

The catalyst of the present invention has excellent ability to decompose ozone at room temperature and exhibits stable decomposition performance over a long period of time, so it can be used not only in industrial ozone decomposition equipment, but also in small office equipment that requires ozone decomposition. Also suitable for use with
It is extremely useful and has a wide range of uses.

[Brief explanation of drawings]

FIGS. 1 to M3 are graphs showing the results of performance tests of Examples and Comparative Examples.

Claims (3)

[Claims] (1) Ozone decomposition catalyst consisting of Ni(III) oxide/Ni_2O_3. (2) Specific surface area of Ni_2O_3 is 100-250m^
2/g of the ozone decomposition catalyst according to claim 1. (3) Claim 1 or 2, wherein Ni_2O_3 is supported on inorganic fiber paper or a honeycomb structure made of it.
The ozone decomposition catalyst described above.