JPH0435223B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing an ozone decomposition catalyst containing manganese and copper and decomposing ozone (O ₃ ) contained in gas.

As an oxidation catalyst containing manganese, a hopcalite catalyst obtained by coprecipitating soluble salts of manganese, copper, cobalt, silver, etc. is known. Hopcalite catalysts are used as oxidation catalysts at low temperatures, such as CO removal agents for gas masks.
Various improved catalysts for hopcalite catalysts have been proposed so far, but basically none of them can significantly change the performance of hopcalite catalysts, and there is a need to further improve the catalytic activity at low temperatures.

However, recently, new methods for producing manganese dioxide oxidation catalysts have been proposed, such as Japanese Patent Application Laid-Open No. 17637/1983.
This method creates a suspension of by-product manganese dioxide (alkali metal delta manganese dioxide) produced from potassium permanganate used to oxidize organic substances under alkaline conditions, and produces a suspension of copper, chromium, iron, cobalt, nickel, etc. This is a method for producing a heavy metal manganese dioxide oxidation catalyst by replacing the alkali metal with an alkali metal at a pH that is at least 0.5 lower than that at which the heavy metal hydroxide precipitates. The fact that the catalyst is produced by replacing heavy metals with alkali metals in this specific pH range is a new method compared to U.S. Patent No. 3,700,605, which proposes producing a manganese dioxide oxidation catalyst from alkali metal delta manganese dioxide. It is becoming.

On the other hand, an electroless plating method is known as a method for depositing heavy metals on the surface of manganese dioxide. In this method, manganese dioxide is immersed in a sensitizer solution containing stannous chloride, and then separated.
It is washed with water, then immersed in an activator solution containing palladium chloride, and washed separately with water. after that,
The surface of manganese dioxide particles can be coated with heavy metals by treatment with an important heavy metal electroless plating solution. This method has drawbacks such as complicated electroless plating operations and high processing costs.

The present inventors have conducted various studies on oxidation catalysts containing manganese and copper (here, manganese is a general term for manganese and its compounds, and similarly includes compounds for copper). We have discovered a method in which a part of the manganese compound is replaced with copper at the same time when forming a precipitate. It was found that this method has a simple manufacturing process and the resulting catalyst has high oxidation catalytic activity at low temperatures, unlike the catalyst manufacturing method in which heavy metals are substituted with alkali metal delta manganese dioate in a specific pH range.

Furthermore, as a result of investigating the O ₃ decomposition performance at low temperatures using such a catalyst, it was found that the catalyst had extremely excellent O ₃ decomposition performance.

Therefore, the object of the present invention is to provide excellent O ₃ at low temperatures.
The object of the present invention is to provide an ozone decomposition catalyst containing manganese and copper that has decomposition performance.

The method for producing an ozone decomposition catalyst according to the present invention includes:
Aqueous hydrogen peroxide and an alkaline solution containing permanganate are added to a mixed solution of soluble salts of manganese and copper, then the precipitate is filtered and dehydrated, a binder is added and the mixture is wetted, and then molded. , characterized by drying. That is, the method of the present invention basically involves adding hydrogen peroxide to a mixed solution of a soluble manganese salt and a soluble copper salt, and then neutralizing it with an alkaline solution containing permanganate, or adding the mixed solution to the alkali solution. This is accomplished by adding hydrogen peroxide after neutralization with a solution.

Although the ozone decomposition catalyst obtained by the method of the present invention is amorphous according to X-ray diffraction analysis and the product cannot be identified, the present catalyst is characterized by being amorphous. . Furthermore, although differential thermal analysis shows that it is a compound of manganese and copper whose weight gradually decreases by releasing crystal water etc. up to about 500°C, the chemical formula of the compound is unknown.

The ozone decomposition catalyst produced by the method of the present invention was tested at a CO concentration of 2500±250ppm and 30%
When the CO concentration after passing through the catalyst was measured by passing through the catalyst at a flow rate of min, it was less than 100 ppm and 350 ppm.
It was found that the performance far exceeded the above-mentioned criteria, which set the following as acceptance criteria. Furthermore, in an O ₃ decomposition test using the test method described in the Examples below, even when air containing an O ₃ concentration of 1 to 5 ppm was treated at a space velocity of 10,000 to 150,000 _HY-1 , it had an O ₃ decomposition performance of 90% or more. However, it was also found that the O ₃ decomposition performance did not deteriorate even in a 500-hour durability test.

A preferred example of the method for producing the catalyst of the present invention will be described in detail below.

0.05 to 5 mol of manganese soluble salts such as manganese nitrate, manganese sulfate, and manganese chloride,
Preferably, an aqueous solution containing 0.1 to 0.3 mol and a soluble salt of copper such as copper nitrate, copper sulfate, copper chloride, etc. per 0.01 to 0.3 mol per mol.
and an aqueous solution containing 5 mol, preferably 0.1 to 0.3 mol. 0.01 to 0.5 mol, preferably 0.1 to 0.2 mol of hydrogen peroxide is gradually added to this mixed solution 1 as an oxidizing agent. As the hydrogen peroxide solution is added, a small amount of air bubbles will be generated.

Once this point is reached, add 0.01 to 0.15 mol per alkali metal salt of permanganate, preferably 0.05
After making an aqueous solution containing ~0.1 mol, an alkaline solution mixed in an aqueous solution containing 1 to 10 mol of potassium hydroxide or sodium hydroxide, preferably 5 to 10 mol per unit, and the above hydrogen peroxide solution is added to the mixed solution. When it is gradually added to the liquid, a blackish brown precipitate is formed and bubbles suddenly appear. It is better for oxidation of the precipitate to end the addition while bubbles are being generated. The alkaline solution may be added while being heated or at room temperature. The obtained precipitate is sufficiently stirred and left to stand, and the supernatant liquid is removed by decantation, and the repulping and decantation are repeated two to three times with heated deionized water. After the pH of the supernatant becomes 9.5 or less, preferably 9 or less, it is separated using a centrifuge. Once this state is reached, a product containing manganese and copper according to the invention is obtained, which is dehydrated to a semi-dry state at temperatures around 100°C and, if necessary, adsorbents such as activated carbon zeolite, bentonite, activated alumina, etc. and binder such as alumina sol, sodium silicate, etc. on a dry weight basis per 100 parts of precipitate.
The catalyst according to the present invention is obtained by adding 30 parts by weight, preferably 5 to 15 parts by weight, thoroughly stirring the mixture, molding it into the required shape using a pelleter, and drying it at 100 to 150 DEG C. for several hours.

In the above catalyst of the present invention, it is not necessary to exclude heavy metals other than manganese and copper. For example, iron, cobalt, nickel, silver, rare earth elements, etc. may be present in the mixed solution as metals or as compounds thereof, or may be mixed with adsorbents such as activated carbon and zeolite.

EXAMPLES Next, the present invention will be specifically explained using Examples, but the present invention is not limited thereto.

Example 1 Dissolve 1900gr _of manganese sulfate ( _MnSO4.OH2O ) in ion-exchanged water to make the liquid volume 50g. Dissolve 500g of copper sulfate (CuSO ₄ 5H ₂ O) in ion-exchanged water to make the liquid volume 13. Next, mix all of these solutions at room temperature, and add hydrogen peroxide (30%) while stirring.
Add 1.

Dissolve 170g of potassium permanganate (KMnO ₄ ) in ion-exchanged water to make the liquid volume 1.1. Dissolve 1050g of caustic soda in ion-exchanged water and reduce the liquid volume.
Add the mixed alkaline solution to the solution adjusted to 3.5. After a precipitate is formed, the mixture is stirred and left to stand for about 1 hour. After the precipitate has settled, the supernatant liquid is separated, warm ion-exchanged water is added to repulp the precipitate, and the same operation is performed. If the pH of the supernatant drops to below 9.5, separate it using a centrifuge.

The resulting cake was dried at 100 to 110°C for about 4 hours to a half-dry state, and then treated with alumina sol (10%).
500 gr was added and the mixture was kneaded using a kneader, formed into pellets with a diameter of 1.5 mm using a pelleter, and dried at 150°C for 5 hours to obtain a product.

As a result of analyzing the obtained product, Mn: 57%,
It contained Cu: 12% and was amorphous.

Example 2 The precipitate obtained in the same manner as in Example 1 was brought to a half-dried state, and 200 gr of activated carbon was added to 1000 gr on a dry basis.
Example 1 by adding 600gr of amminazole (10%)
A manganese catalyst was obtained in the same manner as above.

Comparative Examples 1 and 2 Comparative Examples 1 and 2 were obtained by performing the same operations as in Examples 1 and 2, except that hydrogen peroxide was not used.

Test Example O ₃ The decomposition test was conducted under the following conditions.

Air mixed with O ₃ obtained from an O ₃ generator was passed through water and humidified, and 10 ml of pellet catalysts obtained in Examples 1 and 2 and Comparative Examples 1 and 2 were filled into a cylindrical container with a diameter of 20 mm. The O ₃ decomposition performance was measured by flowing through the mixture at a flow rate of 1 to 30/min and analyzing the O ₃ concentration in the mixed air before and after passing through the catalyst layer.

The test results are shown in FIGS. 1 and 2.

As is clear from the above test results, the manganese catalyst of the present invention is extremely effective in removing carbon monoxide and decomposing ozone at low temperatures.

[Brief explanation of drawings]

Figures 1 and 2 are graphs showing ozone decomposition efficiency versus space velocity or test time.

Claims (1)

[Claims] 1. Add hydrogen peroxide solution and an alkaline solution containing permanganate to a mixed solution of soluble salts of manganese and copper, then filter the precipitate, dehydrate it, add a binder to make it wet, A method for producing an ozone decomposition catalyst, which comprises molding and drying.