JPH0738936B2 - Ozone decomposition method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method of catalytically decomposing ozone contained in a gas by using a catalyst.

[Prior Art] Ozone has a strong oxidizing ability and when decomposed into harmless oxygen, it is widely used in various fields for the purpose of deodorization, sterilization, bleaching and reduction of COD in wastewater. However, some of the ozone used for the above-mentioned purposes is released into the atmosphere in an unreacted state, which may cause secondary pollution such as photochemical smog. Further, when the aircraft flies in the stratosphere, air containing ozone is introduced into the aircraft, which may adversely affect passengers and crew. Further, in recent years, various high-voltage generators, such as dry-type copying machines, have become widespread, and even if the amount of ozone generated from these devices is very small, the interior of the room is contaminated, which is a situation that cannot be ignored for environmental hygiene. is there.

Ozone not only causes odor to be unpleasant, but also has a strong toxic effect on the human body. At a certain concentration or higher, ozone damages the respiratory tract, and even if a minute amount, ozone is extremely harmful if inhaled for a long time. Therefore, it is desired to establish a technology for detoxifying waste ozone generated from various sources by decomposing and removing it.

The conventional waste ozone treatment methods include (I) activated carbon treatment method, (II) chemical cleaning treatment method, and (II)
There are known methods such as I) treatment method by thermal decomposition and (IV) treatment method by ozone decomposition catalyst.

The treatment method using activated carbon is used for the treatment of low-concentration ozone, but due to the reaction mechanism of activated carbon and ozone, the activated carbon is oxidized and consumed at an early stage, resulting in a short service life and the need for frequent replenishment of activated carbon. There is. Also, when treating high-concentration ozone, there is a risk of ignition and combustion of the activated carbon itself due to reaction heat, which is a handling problem.

The treatment method by chemical cleaning is a method of washing waste ozone with an aqueous solution containing a reducing substance, but the treatment cost is high,
Problems of wastewater treatment also arise.

The treatment method by thermal decomposition is 300 ℃ to increase the decomposition efficiency.
The above-mentioned heating is required, and there is a drawback that the heating cost becomes large in order to process a large amount of exhaust gas and the processing cost becomes high.

On the other hand, the treatment method using an ozone decomposing catalyst is said to be the most advantageous method for decomposing ozone because it has no risk of ignition and explosion, does not require wastewater treatment, and can decompose and remove ozone at low cost.

[Problems to be Solved by the Invention] As an ozone decomposition catalyst, various catalysts having excellent catalytic ability have been developed and are commercially available. However, even with these catalysts, there has been a situation in which the performance is not sufficiently exhibited depending on the use conditions. That is, when ozone in high-humidity gas is targeted, there is a disadvantage that the activity of the catalyst is lowered due to the influence of water. It is considered that this is because the active sites on the catalyst surface are covered with water molecules, and the chances of contact between ozone and the catalyst are reduced. Ozone-containing gas generated when ozone is used for water treatment, especially when ozone is used for the purpose of sterilizing and decolorizing clean water, has a relative humidity of almost 100%. The effect becomes remarkable, and it becomes difficult to use the catalyst while maintaining high activity for a long period of time. As a means to avoid such inconvenience,
It is considered that the ozone-containing gas having high humidity is heated to remove the water vapor, but if such a means is adopted, it is necessary to install a heating source, and there are problems in terms of cost and space.

The present invention has been made under these circumstances,
It is an object of the present invention to provide a method for decomposing ozone by a catalyst that can efficiently decompose and remove ozone over a long period of time.

[Means for Solving the Problems] The present invention that has achieved the above-mentioned objects means the following (a) to (c).
The ozone decomposition catalyst consisting of the above components is heated directly by applying electric current, and the ozone decomposition conditions are
To 200 ° C. and / or (ii) heating the catalyst intermittently, and introducing ozone-containing gas to the ozone decomposition catalyst to catalytically decompose ozone. Is.

(A) a catalyst component consisting of one or more elements selected from the group consisting of Ti, Si, Al, Mg and Zr, (b) Mn, Fe, Co, Ni, Ag, Au, Pt, Pd And a catalyst component comprising one or more elements selected from the group consisting of Rh, and (c) one or more conductors selected from the group consisting of metal powder, metal fibers, graphite and activated carbon. .

Further, the present invention uses the catalyst of any of the following catalysts A to C, and does not necessarily control the ozone decomposing conditions as in the above (i) and (ii), but only by directly energizing and heating. Is achieved.

(Catalyst A) (a) Binary oxide of Ti and Si, Binary oxide of Ti and Zr,
And a catalyst component consisting of at least one ternary oxide of Ti, Si, Zr, (b) one selected from the group consisting of Mn, Fe, Co, Ni, Ag, Au, Pt, Pd and Rh. Alternatively, a catalyst component composed of two or more elements, and (c) one or more conductors selected from the group consisting of metal powder, metal fibers, graphite and activated carbon.

(Catalyst B) (a) Catalyst component composed of one or more elements selected from the group consisting of Ti, Si, Al, Mg and Zr, (b) Catalyst component composed of β-type manganese dioxide, (c) ) One or more conductors selected from the group consisting of metal powder, metal fibers, graphite and activated carbon.

(Catalyst C) (a) Binary oxide of Ti and Si, Binary oxide of Ti and Zr,
And a catalyst component comprising at least one of ternary oxides of Ti, Si and Zr, (b) a catalyst component comprising β-type manganese dioxide, (c) a metal powder, a metal fiber, graphite and activated carbon. One or more conductors that are used.

[Operation] The present inventors have studied from various angles from the viewpoint of eliminating the deterioration of the ozone decomposing ability of the catalyst due to water molecules. As a result, the ozone decomposing catalyst to be used is constructed so that it can be directly energized and heated, and the ozone decomposing condition is (i) controlling the direct energizing heating temperature to 50 to 200 ° C., and / or By controlling the heating as being performed intermittently and treating the ozone while electrically heating the catalyst, stable ozone can be obtained for a long period of time even when the gas to be treated contains water molecules. It was found that the treatment effect was exhibited. Further, as the catalyst used at this time, it was found that the catalysts composed of the following components (a) to (c) were optimal, and the present invention was completed here.

(A) a catalyst component consisting of one or more elements selected from the group consisting of Ti, Si, Al, Mg and Zr, (b) Mn, Fe, Co, Ni, Ag, Au, Pt, Pd And a catalyst component consisting of one or more elements selected from the group consisting of Rh, and (c) conductivity consisting of one or more selected from the group consisting of metal powder, metal fibers, graphite and activated carbon. body.

In the present invention, as described above, the catalyst is catalytically decomposed with ozone while being directly energized and heated, and the heating temperature at this time is preferably controlled to 50 to 200 ° C as described above. It cannot exert highly efficient ozone decomposition performance below 50 ° C,
If the temperature exceeds 200 ° C, not only the running cost becomes high, but also the durability of the catalyst becomes problematic.

Further, in the present invention, the direct energization heating does not necessarily have to be continuously carried out, and the heating may be controlled intermittently. That is, the ozone decomposing catalyst according to the present invention has the ability to initially show high activity even under conditions of high humidity at room temperature. When the catalyst is regenerated, the electricity adsorbed on the surface of the catalyst is removed by conducting electric heating to remove the moisture, and regeneration is performed in a short time.When the regeneration of the catalyst is completed, the electric heating is stopped and the catalyst is used at room temperature. The operation can be repeated. By such operation,
It is possible to maintain a highly efficient ozone decomposition treatment capacity for a long period of time while saving running costs.

The catalyst component (a) used in the present invention is Ti, Si, Al, Mg and Z.
One or more elements such as r may be used in an appropriate combination, but a binary complex oxide composed of Ti and Si,
It is particularly preferable to use at least any one of a binary composite oxide composed of Ti and Zr and a ternary composite oxide composed of Ti, Si and Zr (the above catalyst A or catalyst C). By using this catalyst A (or catalyst C), the object of the present invention can be achieved without necessarily controlling the ozone decomposition conditions as in the above (i) and (ii). However, even when the catalyst A (or the catalyst C) is used, the above (i),
Of course, the ozone decomposition conditions may be controlled as in (ii), and the effects of the present invention can be further improved by adopting such a configuration.

Generally, a binary complex oxide composed of Ti and Si is known as a solid acid as shown in, for example, "Catalyst, Vol. 17, No. 3, p. It shows a remarkable acidity that is not found in other things and has a large surface area. In other words, not only a binary compound oxide composed of Ti and Si is simply mixed with titanium oxide and silicon oxide, but also Ti and Si form a so-called binary compound oxide, so that its unique physical properties are expressed. Can be made. Also Ti, Z
The binary composite oxide composed of r and the ternary composite oxide composed of Ti, Zr, and Si also have the same properties as the binary composite oxide composed of Ti and Si. As a result of analysis by X-ray diffraction, each of the above complex oxides is said to have an amorphous or almost amorphous microstructure.

It is not possible to elucidate all of the mechanisms by which the catalyst A (or the catalyst C) according to the present invention exhibits excellent ozone decomposing activity, especially at low temperature (normal temperature), but various properties of the above composite oxides. Is considered to have a favorable effect on ozonolysis activity.

On the other hand, for the catalyst component (b), Mn, Fe, Co, Ni, Ag, Au, P
One or two or more of the elements such as t, Pd and Rh may be used in an appropriate combination, and the use of β-type manganese dioxide is most effective (catalyst B or catalyst C).
If this catalyst B (or catalyst C) is used, (i),
Even if the ozone decomposition conditions are not necessarily controlled as in (ii),
The object of the present invention is achieved. However, even when the catalyst B (or the catalyst C) is used, the ozone decomposition conditions may be controlled as in the above (i) and (ii), as in the case of using the catalyst A. .

The metal powder and metal fibers used as conductors are Al, Ag, Cu.
It may be manufactured by a known method using a conductive metal such as. Further, the catalyst needs to be directly energized and heated and needs to be integrally molded, but the molding shape is not particularly limited.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the following Examples are not of a nature limiting the present invention.
Any design modification that is based on the gist of the later description is included in the technical scope of the present invention.

Example 1 Example 1 A catalyst was prepared as follows.

First, a composite oxide composed of Ti and Si was prepared by the following procedure.

As a Ti source, a sulfuric acid aqueous solution of titanyl sulfate having the following composition was used.

TiOSO ₄ 250g / l (converted to TiO ₂ ) Total H ₂ SO ₄ 1100g / l To 400l of water, 280l of ammonia water (NH ₃ , 25%) was added, and Snowtex-NCS-30 (Nissan Chemical's silica gel, S
A solution containing 24 kg of iO _{2 (} containing about 30% by weight) was prepared separately, and 153 l of the above sulfuric acid aqueous solution was added to 300 l of water, and a diluted titanium-containing sulfuric acid aqueous solution was gradually added dropwise to the solution under stirring. A precipitated gel was produced. TiO ₂ thus obtained
The SiO ₂ gel was filtered, washed with water, and dried at 200 ° C. for 10 hours. Then, it was baked at 550 ° C. in an air atmosphere for 6 hours. The composition of the obtained powder was TiO ₂ : SiO ₂ = 4: 1 (molar ratio), and the BET surface area was 185 m ² / g.

Using the obtained powder (hereinafter referred to as TS-1), an ozone decomposition catalyst was prepared by the procedure described below.

To the mixed powder of the TS-1 powder 8 kg and the graphite powder 1 kg, after adding an appropriate amount of water and mixing well with a kneader,
Knead thoroughly with a kneading machine and extrude a uniform kneaded product to produce a lattice-shaped honeycomb (thickness 0.3 mm, opening 1.4 mm) with an outer shape of 50 mm in length, 50 mm in width, and 50 mm in length. After being dried for an hour, it was fired at 300 ° C. for 2 hours in an air atmosphere to obtain a honeycomb formed body. Then, impregnate it with an aqueous solution of manganese nitrate, dry it and bake it, and use TS-
A catalyst of 1: graphite: MnO ₂ = 80: 10: 10 was obtained.

The ozone decomposition performance of the prepared catalyst was investigated as follows.

125cc of the lattice honeycomb catalyst is filled in a SUS reaction tube,
Water vapor saturated air containing 5000 ppm of ozone was introduced into the catalyst so that the flow rate was 1.25 Nm ³ / hr (space velocity 10,000 hr ⁻¹ ) at room temperature. At this time, the voltage and current were adjusted so that the catalyst temperature became 80 ° C., and the ozone decomposition rate after 3000 hours was determined, whereby 100% was decomposed. The ozone decomposition rate was calculated by the following formula.

Example 2 Using the catalyst prepared in Example 1, ozone decomposition performance was investigated under the following conditions.

A reaction tube made of SUS was filled with 125 cc of the above-mentioned lattice-shaped honeycomb catalyst obtained in Example 1, and steam saturated air containing 5000 ppm of ozone was supplied at room temperature so that the flow rate was 0.25 Nm ³ / hr (space velocity 2000 hr ^-1 ). Was introduced into the catalyst. At this time, the catalyst was heated to 110 ° C. for 30 minutes at a rate of once a day to carry out catalyst regeneration without stopping ozone decomposition.

The ozone decomposition rate was measured 120 days after the introduction of air, immediately before the electric heating. As a result, a high decomposition rate of 99.9% was shown.

[Effects of the Invention] By adopting the configuration of the present invention, the following effects can be obtained.

Since the catalyst itself can be electrically heated, the adhesion of water, which is a major cause of the decrease in catalytic activity, is eliminated, and highly efficient ozone decomposition activity can be maintained for a long period of time.

Since the catalyst itself is a heating element, there is no need to install a heating source separately, which is advantageous in terms of cost and space.
Further, as compared with the case where the catalyst is indirectly heated by another heating source, it is excellent in thermal efficiency and the running cost becomes low.

Employing a method of regenerating the catalyst by intermittently energizing and heating without energizing the catalyst is advantageous in that the catalyst can be regenerated in a state where the catalyst is installed in the reactor.

Continuation of the front page (51) Int.Cl. ⁶ Identification number Reference number within the agency FI Technical indication location B01J 35/02 ZAB G 8017-4G (72) Inventor Kayoshi Nishikawa 1 of 992 Nishioki, Nishihama, Aboshi-ku, Himeji-shi, Hyogo Japan Catalytic Chemical Industry Co., Ltd., Catalytic Research Laboratory (72) Inventor Akira Inoue, 992, Nishi-oki, Nishihama, Aki-ku, Himeji-shi, Hyogo 1 Catalytic Chemical Industry Co., Ltd. (56) Reference JP-A-2-284628 (JP , A)

Claims (6)

[Claims] 1. An ozone decomposing catalyst comprising the following components (a) to (c) is directly energized and heated, and ozone decomposing conditions are (i) a direct energizing heating temperature of 50 to 200 ° C., and And / or (ii) an ozone decomposition method characterized in that the heating of the catalyst is controlled to be performed intermittently, and an ozone-containing gas is introduced into the ozone decomposition catalyst to catalytically decompose ozone. (A) a catalyst component consisting of one or more elements selected from the group consisting of Ti, Si, Al, Mg and Zr, (b) Mn, Fe, Co, Ni, Ag, Au, Pt, Pd And a catalyst component comprising one or more elements selected from the group consisting of Rh, and (c) one or more conductors selected from the group consisting of metal powder, metal fibers, graphite and activated carbon. . 2. The catalyst component (a) is at least one of a binary oxide of Ti and Si, a binary oxide of Ti and Zr, and a ternary oxide of Ti, Si and Zr. The ozone decomposing method according to claim 1. 3. The ozone decomposing method according to claim 1, wherein the catalyst component (b) is β-type manganese dioxide. 4. Ozone decomposing catalyst comprising the following components (a) to (c) is directly heated by electric current, and ozone-containing gas is introduced into the ozone decomposing catalyst to catalytically decompose ozone. Disassembly method. (A) a catalyst component comprising at least one of a binary oxide of Ti, Si, a binary oxide of Ti and Zr, and a ternary oxide of Ti, Si, Zr, (b) Mn, Fe , Co, Ni, Ag, Au, Pt, Pd and Rh, a catalyst component consisting of one or more elements selected from the group consisting of (c) metal powder, metal fiber, graphite and activated carbon One or more conductors selected. 5. Ozone decomposing catalyst comprising the following components (a) to (c) is directly heated by electric current, and ozone-containing gas is introduced into the ozone decomposing catalyst to catalytically decompose ozone. Disassembly method. (A) a catalyst component composed of one or more elements selected from the group consisting of Ti, Si, Al, Mg and Zr, (b) a catalyst component composed of β-type manganese dioxide, (c) a metal powder, One or more conductors selected from the group consisting of metal fibers, graphite and activated carbon. 6. Ozone decomposing catalyst comprising the following components (a) to (c) is directly heated by electricity, and ozone-containing gas is introduced into the ozone decomposing catalyst to catalytically decompose ozone. Disassembly method. (A) Binary oxide of Ti and Si, Binary oxide of Ti and Zr,
And a catalyst component comprising at least one of ternary oxides of Ti, Si and Zr, (b) a catalyst component comprising β-type manganese dioxide, (c) a metal powder, a metal fiber, graphite and activated carbon. One or more conductors that are used.