JPS59120250A - Preparation of catalyst - Google Patents

Abstract

PURPOSE:To contrive to curtail the amount of a catalyst used, while fixing a noble metal as a catalytic component at a facultative position on a carrier, by impregnating said carrier with the aqueous solution of a noble metal salt, drying it, dipping it in the aqueous solution of an alkali metal borohydride, and then reducing it. CONSTITUTION:An inorganic carrier, e.g. alpha-alumina, is impregnated with the aqueous solution of the nitrate or the like of a noble metal, e.g. Pt, Pd or Rh, as a catalytic component, dried, dipped in the aqueous solution of an alkali metal borohydride and then treated to reduce said noble metal salt into noble metal. Thus, the catalyst comprising the noble metal supported on the carrier is obtained. In the preparation of said catalyst, a position for supporting the catalytic component, the thickness of its supporting layer, etc. can be facultatively changed by changing the pH of the aqueous solution of said noble metal salt, a drying time, the concentration of the aqueous solution containing the alkali metal hydrohydride, e.g. NaBH, LiBH or KBH4, etc. Thus, the inexpensive catalyst which can exhibit maximum effect with a reduced amount of noble metal is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a catalyst that can be supported at any position on a noble metal all-catalyst carrier (hereinafter referred to as carrier).

Catalysts made of noble metals such as rhodium, palladium, and platinum supported on carriers are used in the petrochemical industry, exhaust gas purification of automatic warehouses, and the like.

However, in order for these expensive precious metals to function effectively as catalyst materials, it is necessary to support the entire catalyst material in an optimal position on the carrier where the catalytic conversion reaction is carried out. ' = 1: Ta. By freely controlling the position of the catalyst component on the carrier in this way, it is possible to reduce the use of precious metals, and it is also possible to prevent poisoning and deterioration of the catalyst.

Conventionally, there are several methods for controlling the distribution of noble metals supported on a carrier.
54), method of fully acting the surfactant (JP-A-49-7
7895), or a method in which urea water and ammonium citrate are used together (JP-A-54-156589.54-1)
49391).

Method of using an organic medium in the impregnating liquid (Japanese Patent Application Laid-Open No. 53-7978
5) etc. However, using these methods, 5. The only carriers that can be used are t-occupied materials such as tanzamo-alumina and silica-alumina.

a- Not applicable to inert materials such as alumina.

For example, when noble metals are supported on α-alumina as a carrier by the above-mentioned conventional methods, in all the methods, the precious metals are uniformly distributed inside the carrier, and the dispersion state is poor, and the supporting position is completely controlled. I can't.

The present invention aims to overcome all of the drawbacks of the prior art described above and to provide a method by which noble metals can be easily supported at desired positions on any type of support made of a-alumina metal. That is, in the present invention, a carrier is impregnated with an aqueous solution of a PL metal salt.

After drying, the entire carrier NnBH4, TLiEH4, K B
A method for producing a catalyst, characterized in that the noble metal salt is reduced to a total noble metal by immersing it in an aqueous solution of a borohydride salt of an alkali metal such as H4, and the noble metal is fixed at any position on the carrier. It is in.

According to the method of the present invention, noble metal gold such as platinum, rhodium, palladium, σ-alumina, γ-aluminum.

It can be supported at any position in an inorganic carrier such as f-alumina, silica/alumina, alumina/magnesia spinel, etc. Therefore, it is possible to produce a complete catalyst that can maximize the effects of these precious metals as catalyst components. In addition, this prevents the use of expensive precious metals in all areas.

All catalysts can be manufactured at low cost.

In addition, it is possible to produce a complete catalyst that is resistant to poisoning.

More specifically, precious metals are
It can be supported in any desired form, such as in the middle part between the center and the outermost surface, or uniformly over the entire surface, and the thickness of the supported layer can also be controlled.

In the present invention, the noble metal salt used is a nitrate, hydrochloride, ammonium salt, etc. of a noble metal such as platinum, palladium, or rhodium as a catalyst component. 1. Although the concentration of the noble metal salt in the aqueous solution varies depending on the amount of the catalyst component to be supported, it is preferably from o, oi to 10% by weight in terms of the noble metal. Impregnation of these aqueous solutions into the carrier is carried out by immersing the entire carrier into the solution nine times.

It is preferable to set it to 16.

Drying after impregnating with the above water bath liquid is carried out at 60 to 150°C.
It is preferable to carry out the treatment for 300 minutes to 300 minutes.

As the alkali metal borohydride salt, T-5-B
Ha.

N'L B H4, K B H (etc.) These are allowed to act on the noble metal-impregnated carrier in a water bath state.

As shown in the examples, the supported position of the catalyst component can be changed at will.

9 In addition, the present invention can be applied to a-alumina, alumina magnesia bio, which has conventionally been impossible to support a catalyst component at any position.
This method is of great significance in that it has become possible to use it for inert antibodies such as fluorophores. However, the present invention uses not only these inert carriers but also γ-alumina, S-alumina, silica 11. ．． It can also be added to active carriers such as Mina.

In addition, in the present invention, lanthanum oxide (La2O3)
Even on a carrier on which a co-catalyst such as cerium R ide (ce+os) is supported in advance, the precious metal can be supported at a desired position without being affected by the working medium.

Hereinafter, the present invention will be fully explained in more detail with reference to Examples.

Example 1 A catalyst comprising palladium supported at various positions on an a-alumina support was produced by the method of the present invention.

That is, as the noble metal salt, nitric acid) was used.

P day solution (F o 85, palladium concentration 0.2
5 car weight%), a spherical α with a diameter of 3 and a specific surface area of 10yd/9
- Alumina gold immersion for 30 minutes, after which the α-alumina was dried at 110°C. Then Nl7B H4
The catalyst was immersed in an aqueous solution, allowed to settle, and then dried to obtain a catalyst in which gold and silver were supported on an α-alumina carrier. 11 above
During drying at 0°C, the carrier was divided into five groups and subjected to three types of drying for 0.45.90 minutes. Then, they were immersed in NIZEH4 aqueous solutions of five different dry concentrations. In this way, the catalyst obtained by the method of the present invention was
The sample was cut from 0, and the mutual distribution of palladium in the cross section was measured visually and with an EPMA (X-ray microanalyzer). The results of visual inspection and EPM A were in good agreement. The visual result was calculated as the drying time, NIZB'f (4
Each species degree condition is shown in Figure 1. The circles in the diagram are
・Catalyst #JT, and the multi-dot areas shown in the catalysts obtained under drying conditions of 45 minutes and 90 minutes are smaller amounts of palladium dispersed than the shaded areas shown for catalysts under other conditions. It shows the position where you are.

As is known from Figure 1, 9 For example, Eri H4 concentrated water ( Under the conditions of 1.0ζ% degree and 90 minutes of drying time.

Palladium can be entirely supported inside the carrier in a circular shape with a radius of 172 or less.

For comparison, condensed α-alumina was impregnated with U.S. Pat. was prepared.

Also, for comparison, Tokukai Sho! 54; 1:,, 36
．． 58.9 and j4.5'391, a spherical α-alumina carrier was pre-impregnated with urea water (twice equivalent to palladium) by 1/2 of the total water absorption, and then impregnated with citrate The palladium nitrate aqueous solution was impregnated in the same manner as above in the coexistence of palladium (equimole of palladium).

After drying at 110'C for 12 hours, dry at 50°C in hydrogen gas.
A comparative catalyst was prepared by calcining the catalyst for 3 hours.

Regarding these comparative catalysts, we observed the entire cross section of the catalysts in the same manner as above, and as shown in Figure 2, α=
Alumina carrier Q spreads over the entire wall9. In the comparative method, palladium is supported at the designated position on the α-alumina support.According to the present invention, the inert α-aluminum □ It can be seen that it is possible to control the distribution of noble metals supported on the carrier, which was not possible with conventional techniques.

In the same manner as in Example 1, the α-alumina support was impregnated with the water bath solution for various impregnation times, and this was dried and immediately immersed in a 1.0% by weight NrLBH aqueous solution without drying. A catalyst was prepared. The state of supported strain of snow palladium is shown in FIG. 3 in the same manner as in FIG. 1, α8□5. Immersion time in the NαB island aqueous solution was 2 minutes.The prepared catalyst was coated with palladium on the surface of the box, and by increasing the immersion time further, the supported layer on the surface area was formed. You can see that the rabbit is thick. In this way, by changing the above-mentioned preparation conditions, the noble metal can be supported at a desired position and a desired thickness in the carrier.

Example 5 In the same manner as in Example 1', use glass as funds (■).

1st class degree of 0.5.・Under the conditions of weight%: ゛Badium nitrate stand: □Drying time after □□□o'(6'o,'
6 Total: ':q Change to o minutes.

A four-hung catalyst was prepared. Obtained, the cross-sectional state of the Rareen catalyst is i
``□Same as Figure 1 and □, and shown in Figure 4. □Figure 4' top 9. Under the above conditions, palladium was supported in a ring shape in the middle tray between the center of the carrier and the outermost layer. The thickness of the support layer can be adjusted by changing the drying time.

Example 4 A catalyst was prepared under the same conditions as in Example 6 except that a 2% by weight aqueous solution of Lj and EH400 was used.

As a result, the state of palladium supported was similar to that shown in FIG. Even if the LiBH4 aqueous solution is used in this way, palladium can be completely supported at the desired position and thickness as in Example 6.

Example 5 As a water-accumulating boron solution of alkali metals.

i(B) A catalyst was prepared in the same manner as in Example 5, except that an aqueous solution of gold with a concentration of 04% of Ha was used.

As a result, the state of palladium supported was similar to that shown in FIG.

By the method of the present invention from Examples 1 to 5 above.

α-Alumina, which is necessary for inert carriers, also has internal parts inside the carrier.

It can be seen that the noble metal can be entirely supported at various positions such as the surface or an intermediate layer thereof. Moreover.

According to Kenpo, it is also possible to adjust the thickness of the carrier layer.

[Brief explanation of the drawing]

The figure shows the supported positions of catalyst components in the cross section of the catalyst obtained in Example. Figure 1 shows the drying time and Nn, BH
, Catalysts obtained under various conditions of aqueous solution concentration; Figure 2 shows the catalyst obtained in the comparative method. → Figure 6 shows the palladium nitrate aqueous solution impregnation time and its P-■-
Figure 4 shows the respective I-lines of the catalysts obtained under various conditions of drying time after impregnation with palladium nitrate. . Patent Applicant Co., Ltd. Toyota Medium Fire Research Institute 1st Figure 2 3rd 4th

Claims (2)

[Claims] (1) A carrier is impregnated with an aqueous solution of a noble metal salt, and after drying, the carrier is immersed in an aqueous solution of a borohydride salt of the entire alkali metal to reduce the blue metal to the entire noble metal, and the precious metal gold. 2. A method for producing a catalyst, which comprises immobilizing it at an arbitrary position on a carrier. (2) Is the alkali metal borohydride salt one or more of lithium borohydride, thorium borohydride, and potassium borohydride? A method for producing a catalyst according to claim 1.