JPS6333419B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improved method for producing a carbon monoxide oxidation catalyst comprising a mixture of palladium or a palladium compound and activated manganese dioxide.

Conventionally, from the perspective of human health management, various CO oxidation catalysts have been proposed for the purpose of removing or reducing carbon monoxide (hereinafter abbreviated as CO) generated from heating equipment exhaust gas and smoking. However, it is easily deactivated by trace amounts of moisture coexisting in the gas.
Currently, it is difficult to obtain a CO oxidation catalyst that is satisfactory for practical use, as many of them have drawbacks such as being active only at high temperatures, insufficient CO oxidation activity, poor sustainability of oxidation activity, or being expensive. be.

The present inventors have proposed a CO
As a result of intensive research to provide an oxidation catalyst,
We have discovered that palladium or a mixture of palladium compounds and activated manganese dioxide is a fully satisfactory CO oxidation catalyst with few of the above-mentioned drawbacks,
The content thereof was disclosed in Japanese Patent Application Laid-Open No. 57-65331.

Therefore, the method for producing the CO oxidation catalyst disclosed in the above specification involves simply mixing pre-produced active manganese dioxide powder with palladium or palladium compound powder, or immersing active manganese dioxide in an aqueous palladium salt solution and then removing the solvent. Methods such as distilling off the CO and supporting palladium salts on the surface of active manganese dioxide have been used, but the present inventors further researched a method for producing a CO oxidation catalyst made of palladium and active manganese dioxide. As a result, we have found a production method that significantly reduces the content of palladium, which is a precious metal, and has significantly superior CO oxidation activity compared to the CO oxidation catalyst obtained by the above production method, leading to the present invention. Ivy.

That is, the gist of the present invention is to produce active manganese dioxide from a manganese salt in the presence of palladium or a palladium compound in a method for producing a CO oxidation catalyst consisting of a mixture of palladium or a palladium compound and active manganese dioxide.

Active manganese dioxide from manganese salts (hereinafter
As for the preparation method of divalent manganese salt and potassium permanganate (hereinafter abbreviated as KMnOx) _,
abbreviated as) under alkaline conditions (J. Atztenbrough et al., J.Chem.Soc., 1094
(1952)), the method prepared under nitric acid (T. Tolman, British Patent No. 1315374) and the method prepared from neutral solutions (S. Ball, Biochem.J, 42 516
(1948)), but any of the above-mentioned alkaline, acidic, and neutral methods may be used to prepare MnOx used in the present invention.

The palladium used in the method for producing the carbon monoxide removal catalyst of the present invention is preferably a water-soluble palladium salt, but insoluble palladium compounds, palladium black, etc. can also be used.

Palladium or a palladium compound may be added to the divalent manganese salt aqueous solution in advance, or may be added at the same time when mixing KMnO ₄ or the KMnO ₄ aqueous solution and the divalent manganese salt aqueous solution.

The precipitate generated by adding KMnO ₄ or KMnO ₄ aqueous solution is thoroughly washed with water, filtered and dried before use. In the catalyst obtained by the method of the present invention, the added palladium completely remains.

Divalent manganese salt and KMnO ₄ used as raw materials
Although there are changes in the color tone and physical properties of the produced catalyst depending on the amount ratio, there is no major difference in catalytic activity.

The obtained powdered catalyst may be used as it is, or may be made into pellets or granules by compression molding or a known molding method using a binder such as CMC.

The properties of the catalyst obtained by the method of the present invention are as follows:
Compared to the palladium/MnOx catalyst described in JP-A-57-65331 previously disclosed by the present inventors, the palladium content is 1/10 or less, that is, 0.5%.
The following points show that it has remarkable effects on CO oxidation activity and water resistance at room temperature.

The CO oxidation catalyst of the present invention can be used as a CO remover for gas masks, as an air purifier for air cleaners in closed spaces such as inside cars or indoors, and as a reducer for CO in cigarette smoke used to fill filters and cigarette holders. Wide.

The details of the present invention will be explained below using Examples. The CO oxidation activity was assayed by the pulse method. Specifically, after filling a glass tube with an inner diameter of 6 mm with a certain amount of dry catalyst, a pulse of CO-containing gas is passed through it at room temperature using helium as a carrier gas at a flow rate of 60 ml per minute, and changes in the composition of the gas during the pulse are measured using a gas chromameter. It was quantified by tography. Pulse volume is 10ml each, gas composition during pulse is CO5%,
O ₂ 5%, remainder helium. In this specification, % representing gas composition is volume % under standard conditions.
, and other percentages are by weight.

Example 1 10g of manganese nitrate (Mn(NO ₃ ) _{2.6H 2} O)
It was dissolved in 100 ml of water, and to this was added 2 ml of water in which 40 mg of palladium chloride was dissolved. After adding another 5 ml of concentrated nitric acid, while stirring the solution well,
100 ml of KMnO ₄ aqueous solution was slowly added dropwise. Stirring was continued for 30 minutes after the dropwise addition was completed, and the resulting precipitate was thoroughly washed with distilled water, and when the pink color of permanganate ions was almost no longer observed, it was filtered under reduced pressure. The obtained solid was air-dried and further heated at 100℃.
After drying for 24 hours, 5.6 g of a blackish brown powder catalyst according to the present invention was obtained.

Analysis of this material by atomic absorption spectroscopy showed that the added palladium element remained completely, and its content was 0.43% in the obtained catalyst.

Using 100 mg of this catalyst, the CO oxidation activity was examined using the pulse method. As a result of this pulse test, the CO in the pulse completely disappeared over 10 pulses or more, and it was observed that CO ₂ with an equimolar amount of CO was produced.

On the other hand, as a control, 5 g of MnOx was immersed in 10 ml of 5% palladium nitrate aqueous solution and then dried under reduced pressure.
A MnOx catalyst containing 9.1% palladium nitrate was prepared. When 100 mg of this material was weighed and subjected to the same pulse test, the CO during the first pulse was
The reduction rate was 86%, and the activity gradually decreased with the number of pulses, and the CO reduction rate at the 5th pulse was 76%.
It was %.

Example 2 10g of manganese sulfate ( _MnSO4.4 ~ _5H2O )
It was dissolved in 100 ml of water, and 10 ml of 40% aqueous sodium hydroxide solution and 50 mg of palladium nitrate were added thereto.
While stirring this solution well, add 5% KMnO ₄ aqueous solution.
200ml was slowly dripped. Thereafter, the same treatment as described in Example 1 was carried out to obtain 6.0 g of a blackish brown dry powder catalyst according to the present invention. The palladium content in this catalyst was 0.37%.

When 100 mg of this catalyst was weighed and the CO oxidation activity was examined using the pulse method, it was found that over 10 pulses,
The CO in the pulse was completely converted to _CO2 .

Example 3 The dried catalyst obtained by the method of the present invention obtained in Example 1 was heated at 22°C.
When I left it in a room with relative humidity of 60% for a week,
A 14% weight increase was observed. 100 out of these
When mg was weighed and the CO oxidation activity was measured using the pulse method, 37% of the CO was converted to CO ₂ in the first pulse. A second pulse was subsequently passed and 58% of the CO was converted to _CO2 . CO oxidation activity increased as the number of pulses increased, and the CO peak completely disappeared at the fifth pulse.

On the other hand, a control product similar to that used in Example 1 was left in a room with a relative humidity of 60% for one week, and then 100 mg was weighed out and a pulse test was conducted. As a result, the conversion rate of CO to CO ₂ during the first pulse was 22%.
The CO conversion rate at the 10th pulse was 80%, indicating almost steady activity.

Example 4 10g of manganese acetate (Mn(CH ₃ COO) ₂ .
4H ₂ O) with 50 mg of palladium chloride dissolved in 10
ml of 0.1N hydrochloric acid and 150 ml of water were added. While stirring the mixture, 5 g of KMnO ₄ powder was slowly added. After continued stirring for 30 minutes, the resulting precipitate was washed with distilled water using a decanting method and then filtered. The obtained precipitate was air-dried and further dried at 110° C. for 24 hours to obtain 5.8 g of a blackish brown powder catalyst according to the method of the present invention.
The palladium content in the catalyst was 0.50%. When 100 mg of this catalyst was weighed and the CO oxidation activity was examined using the pulse method, CO was completely converted to CO ₂ over 10 pulses or more.

Example 5 2 ml of a 2% CMC aqueous solution was added to 3 g of a dark brown powder catalyst produced in the same manner as in Example 2, and the mixture was thoroughly kneaded.
The mixture was extruded through a 16-mesh sieve and formed into granules with a diameter of about 1 mm. This is 110
After drying at ℃ for 16 hours, 300 mg of the mixture was weighed and filled into a glass tube with an inner diameter of 6 mm. To one end of this glass tube, a cigarette manufactured by Japan Monopoly Corporation (trade name: Mild Seven) was attached with cellophane tape. Insert the other end of the glass tube into the automatic smoking device,
Standard smoking conditions (1 puff/min, 2 seconds/puff, 35ml/
The gas phase of the smoke obtained by passing through the catalyst layer using a puff (shell length: 30 mm) was analyzed using a non-dispersive infrared spectrophotometer (manufactured by Fuji Electric Keiso KK).

Instead of the catalyst according to the present invention, "Mild Seven" was attached to a glass tube filled with 300 mg of the catalyst used as a control sample in Example 1 as Control 1, and "Mild Seven" was attached to a glass tube filled only with 100 mg of activated carbon. The gas phase was analyzed in the same manner using the control 2 as control 2.

As a result, the CO in the smoke of Control 1 was reduced by 32% compared to Control 2, but the CO concentration in the smoke of cigarettes equipped with the catalyst of the present invention was reduced by 53% compared to Control 2.

Example 6 Add 50 mg of palladium black to 10 g of manganese nitrate, and add 5% KMnO ₄ to this while stirring well.
100 ml of the aqueous solution was added dropwise over about 10 minutes. After dripping
After continued stirring for 30 minutes, the generated precipitate was thoroughly washed with distilled water and then filtered. Then 24 at 100℃
Black powder catalyst according to the invention method after drying for 6.0 hours
I got g. This catalyst contained 0.81% palladium. 100 mg of this catalyst was weighed and a pulse test was conducted.

On the other hand, 30 g of manganese sulfate ( _MnSO4 .
_4H2O ) was dissolved in 350ml of water, 35ml of concentrated nitric acid was added, and then 21g of powdered _KMnO4 was added. 50mg of palladium black was mixed well with 5g of MnOx powder, and the mixture was dried at 110℃ for 24 hours. As a control, we weighed 100 mg and conducted a pulse test.

As a result, the reduction rate of CO during the first pulse of the control was
The catalyst produced by the method of the present invention converted 100% of the CO in the first pulse to _CO2 , compared to 32%.

As is clear from the above examples, the CO oxidation catalyst produced by the method of the present invention is
-Compared to the catalyst manufactured by No. 56331, it has a lower palladium content, has the ability to efficiently oxidize CO in gas at room temperature, and exhibits high resistance to moisture in the atmosphere during storage. It has been demonstrated that it has a significant effect.

Claims (1)

[Claims] 1. In a method for producing a carbon monoxide oxidation catalyst consisting of palladium or a palladium compound and active manganese dioxide, active manganese dioxide is reacted with a divalent manganese salt and potassium permanganate in a solution containing palladium or a palladium compound. 1. A method for producing a carbon monoxide oxidation catalyst, the method comprising: producing a carbon monoxide oxidation catalyst;