JP3080738B2 - Manufacturing method of platinum-based supported catalyst - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to a method for producing a platinum-based supported catalyst,
More specifically, the present invention relates to a novel method for producing a catalyst supporting a platinum group metal, particularly platinum and / or palladium, which is useful for purifying exhaust gas from internal combustion engines, stoves, cookers and the like.

Conventionally, it has been proposed to use a platinum-based supported catalyst for purifying exhaust gas from internal combustion engines, stoves, cookers and the like [for example, JP-A-55-88848, JP-A-58-199042). See, for example, U.S. Pat. What is conventionally used as a carrier in such a supported catalyst is mainly alumina, silica,
It is a ceramic material such as zirconia. However, the ceramic carrier has drawbacks such as low mechanical strength and difficulty in downsizing.

On the other hand, it has been proposed to use a metal carrier because of its advantages, such as downsizing of the exhaust gas purifying apparatus and excellent mechanical strength.

However, since the metal carrier has a higher coefficient of thermal expansion and a denser surface than the ceramic carrier, the platinum group metal element has a good adhesion to the metal carrier, a uniform loading amount, and workability at the time of loading. And other problems, such as inferior performance or needing extra treatment such as coating a metal carrier with alumina or the like.
No. 752].

Japanese Patent Application Laid-Open No. 58-199042 discloses a method for supporting a platinum group element on an inorganic carrier such as silica, alumina, and zirconia.
For example, it is disclosed to use a nitric alcohol solution such as chloride, nitrate and sulfate.However, when this method is applied to a metal carrier as it is, the solution can be applied to the surface of the metal carrier or impregnated. Inferiorly, there is a problem that it is difficult to obtain a supported catalyst having high catalytic performance.

As a result of intensive studies to solve this problem, the present inventors have now found that 250 g of at least one of dinitrodiammine platinum and dinitrodiammine palladium is used.
It has been found that the above-mentioned problem can be solved by using a solution obtained by dissolving a nitric acid aqueous solution containing at a metal concentration of / l or more in a lower alcohol, thereby completing the present invention. .

Thus, according to the present invention, a nitric acid aqueous solution containing at least one of dinitrodiammineplatinum and dinitrodiamminepalladium at a metal concentration of at least 250 g / l is dissolved in a lower alcohol having good spreadability and permeability. And applying the resulting solution to a metal carrier, followed by heating and calcining.

In the present invention, only one of dinitrodiammineplatinum and dinitrodiamminepalladium may be used, or two or more may be used in combination. 2
When the species are used in combination, a solution containing a mixture of the two dinitrodiammine compounds may be used for the metal carrier, or a solution containing each of them may be separately prepared and applied to the metal carrier sequentially. You may make it.

The dinitrodiammine compound (dinitrodiamineplatinum and / or dinitrodiamminepalladium) is first dissolved in an aqueous nitric acid solution. The nitric acid concentration in the aqueous nitric acid solution at that time is generally 100 to 600 g /
l, preferably in the range from 200 to 500 g / l. If the dinitrodiammine compound is difficult to dissolve in an aqueous nitric acid solution at room temperature, it can be dissolved by heating to a temperature in the range of about 70 to about 100C, preferably about 80 to about 95C. In this case, the concentration of the dinitrodiammine compound can be increased to 250 g / l or more in terms of metal concentration in one step. However, when the concentration of the dinitrodiammine compound is high, the dissolution rate generally becomes slow, and the dissolution takes time. Therefore, as described below, it is usually convenient to prepare a low-concentration solution and then concentrate it to a predetermined concentration.

First, the concentration of a dinitrodiammine compound in an aqueous nitric acid solution is generally 1 to 200 g in terms of metal.
Per liter, preferably from 20 to 150 g / l. The concentration of the compound in terms of metal is 1 g / l
If it is lower, the work efficiency at the time of concentration becomes poor, and
If it exceeds 200 g / l, dissolution of the dinitrodiammine compound in the aqueous nitric acid solution becomes slow.

The aqueous nitric acid solution of the dinitrodiammine compound thus prepared is then added with about 50 to about 100
C., preferably at a temperature of about 70 to about 90 ° C.,
In order to perform this concentration quickly, the concentration may be performed under reduced pressure. Concentration is at least 250 g / l metal concentration, typically 2 g / l.
50 g / l to 450 g / l, preferably 300 g / l to 40
Repeat until the amount falls within the range of 0 g / l.

An aqueous nitric acid solution containing the dinitrodiammine compound thus obtained at a metal concentration of 250 g / l or more is dissolved in a lower alcohol. The lower alcohol that can be used includes, for example, methanol, ethanol, propanol, isopropanol, butanol and the like, butanol is particularly preferable.

The concentration of a dinitrodiammine compound in a lower alcohol solution in terms of metal is generally from 20 to 200.
g / l, preferably in the range of 40 to 150 g / l. If the metal concentration is lower than 20 g / l,
If the catalyst carrying efficiency is deteriorated, and if it exceeds 200 g / l, the catalyst is likely to agglomerate, and problems arise in terms of catalytic activity, carrying strength, uniformity of carrying amount and the like.

The solution thus prepared is then applied or impregnated on a metal carrier. Examples of the metal carrier include iron-nickel-based, iron-chromium-nickel-based, iron-chromium-based alloys, and alloys obtained by further adding aluminum, yttrium, lanthanum, cerium, neodymium, and the like to these alloys. . These metal carriers may be heat-treated at a temperature of about 400 ° C. or more to oxidize the surface as necessary, or alternatively, alumina, silica,
It is also possible to coat with a ceramic such as zirconia.

The application of the solution to the metal carrier can be performed by a method known per se, for example, a method of immersing the metal carrier in the solution, or applying the solution to the metal carrier by spraying or brushing. The method can be performed by a method such as

The metal carrier to which the solution has been applied is preferably dried to remove the solvent (particularly the alcohol). The drying temperature is not particularly limited, but is generally about 20 to
Temperatures in the range of about 150 ° C, especially 40-80 ° C, are suitable. Drying is at least 80% of the total solvent, preferably 9%
It is desirable to carry out until 0% or more is removed.

The appropriately dried metal carrier is then heated and calcined. This heat calcination is generally carried out in an oxidizing atmosphere such as air or a reducing atmosphere such as hydrogen at a temperature in the range of about 200 to about 1,000 ° C, preferably about 300 to about 700 ° C, for about 3 to about 30 ° C. It can be carried out by heating for about a minute.

According to the above-described method of the present invention, a platinum-supported catalyst having a catalyst is firmly and uniformly attached to a metal carrier, has excellent durability, high catalytic activity, and excellent catalytic performance. be able to.

The platinum-based catalyst produced according to the present invention can be used, for example, for purifying exhaust gas from internal combustion engines, stoves, cookers and the like.

Next, the present invention will be described more specifically with reference to examples.

[0021]

【Example】

Example 1 25 g of dinitrodiammineplatinum was added little by little to 200 ml of an aqueous nitric acid solution having a nitric acid concentration of 200 g / l heated to 85 ° C., and dissolved for 10 hours to prepare a nitric acid aqueous solution of dinitrodiammineplatinum.

The aqueous solution was heated to 70 ° C. under reduced pressure, concentrated to a platinum concentration of about 300 g / l, dissolved in butanol to prepare a coating and impregnating solution (platinum solution-1).

At this time, the concentration of platinum metal was 75 g / l.

A coating and impregnating solution was prepared in the same manner as described above except that 33 g of dinitrodiammine palladium was used instead of 25 g of dinitrodiammine platinum (palladium solution-1).

After the SUS310 metal carrier was immersed in the prepared coating and impregnating solution, it was taken out from the solution, dried at 50 ° C. for 30 minutes, and calcined at 600 ° C. for 1 hour in the air to obtain a platinum-supported catalyst (Example Catalyst-1). ) And a palladium-supported catalyst (Example Catalyst-2).

For comparison, a platinum-supported catalyst (Comparative Example Catalyst-1) was prepared in the same manner as described above except that a nitric acid aqueous solution of dinitrodiammineplatinum and dinitrodiamminepalladium was applied and used as an impregnating solution. And a palladium-supported catalyst (Comparative Example Catalyst-2).

Example catalysts 1 and 2 and comparative example catalysts 1 and 2
As a result of analyzing the state of loading of the catalyst on the metal carrier with an EPMA analyzer, the catalysts of Examples 1 and 2 were uniformly loaded on the metal carrier, whereas the catalysts of Comparative Examples 1 and 2 showed that the catalysts were aggregated. However, it was unevenly supported on the metal carrier.

The catalysts of Examples 1 and 2 and Comparative Examples 1 and 2 which were heated at 500 ° C. for 1 hour and then naturally cooled 20 times were put in water and ultrasonic waves were applied thereto to carry the catalyst on a metal carrier. Was subjected to a strength test. As a result, the catalysts of the example catalysts 1 and 2 had 5% or less of the catalyst falling off, whereas the catalysts of the comparative examples 1 and 2 had most of the catalyst dropped off.

Example 2 SUS310 was immersed in a 2: 1 mixture of the platinum solution-1 and the palladium solution-1 prepared in Example 1 in a metal carrier calcined at 450 ° C. for 30 minutes in the air, and then cooled to room temperature. , And then calcined at 550 ° C for 1 hour in the atmosphere to prepare Example Catalyst-3.

Example catalyst-3 and Example catalyst-1 and Example catalyst-2 produced in Example 1 were replaced with 800 pp of methane.
The reaction was carried out at 450 ° C. using a sample gas containing m, oxygen 5%, moisture 5% and nitrogen residue, and the methane gas amounts at the gas inlet and outlet were analyzed using a gas chromatograph to measure the methane purification rate.

As a comparative example, a solution prepared by adding 45% by volume of ethyl alcohol to a 200 g / l nitric acid aqueous solution was prepared.
0 ml, 40 g of chloroplatinic acid or palladium chloride 2
A metal carrier of SUS310 is immersed in a solution in which 5 g is dissolved,
After being taken out of the liquid and dried at 50 ° C. for 30 minutes, it was baked at 600 ° C. in the air for 1 hour, and Comparative Example Catalyst-3 (platinum supported)
And Comparative Example Catalyst-4 (supporting palladium) was produced.

Using these comparative catalysts, the same methane purification rate as in the above example was tested. Table 1 shows the results.

The results show that the activity of the catalyst according to the production method of the present invention is excellent.

[0034]

[Table 1]

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Tomomi Asagi 2-12-30 Aoyagi, Soka City, Saitama Prefecture Ishifuku Kinzoku Kogyo Co., Ltd. Soka No. 1 Plant (56) References JP-A-55-88848 (JP, A JP-A-58-199042 (JP, A) JP-A-63-107752 (JP, A) JP-A-1-307445 (JP, A) JP-A-4-298238 (JP, A) 4042 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) B01J 21/00-37/36 B01D 53/96

Claims (1)

(57) [Claims] 1. A solution obtained by dissolving a nitric acid aqueous solution containing at least one of dinitrodiammineplatinum and dinitrodiamminepalladium at a metal concentration of at least 250 g / l in a lower alcohol is applied to a metal carrier, and then heated. A method for producing a platinum-based supported catalyst, characterized by firing.