JPH0673412A - Production of palladium particulate - Google Patents

Abstract

PURPOSE:To provide the process for production capable of controlling the grain sizes of the palladium particles which are narrow in the width of a dispersed grain size distribution. CONSTITUTION:D-erysorbic acid or D-erysorbate is used as a reducing agent at the time of producing the palladium particulates by reducing an aq. soln. contg. palladium. The pH of the D-erysorbic acid is preferably >=0.5. This pH is adjusted to a 0.1 to 8 range at the time of using an aq. palladium nitrate soln. is used as a raw material. The pH is adjusted to an 8 to 13 range at the time of using a palladium ammonium complex soln.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing fine palladium particles.

[0002]

2. Description of the Related Art Conventionally, as a method for producing fine palladium particles, a method has been used in which hydrazine is used as a reducing agent and sodium hydroxide is added to an aqueous solution of chloropalladic acid for reduction.

[0003]

However, this method has a drawback in that reduced particles are attracted to each other so that only agglomerated palladium particles having a wide particle size distribution can be obtained. The present invention has been made in order to solve the above drawbacks, and an object of the present invention is to provide a method for producing dispersed fine palladium particles having a narrow particle size distribution and capable of controlling the particle size.

[0004]

The present invention is a method for producing palladium fine particles by reducing palladium ions in a palladium-containing aqueous solution, particularly a palladium nitrate aqueous solution and a palladium ammonium complex solution, and D-erythorbic acid or D is used as a reducing agent. -It is characterized in that monodispersed palladium fine particles are obtained by using erythorbates.

Thus, in the production method of the present invention, D-erythorbic acid or D-erythorbic acid salts are used because the redox potential of them is suitable for reducing palladium ions and at the same time the particles are aggregated. This is because it has the function of preventing Further, in the claims of the present invention, D-
The erythorbic acid and D-erythorbic acid salts may be sodium salts, potassium salts, ammonium salts or the like.

Further, in the present invention, when an aqueous palladium nitrate solution is used as the palladium-containing aqueous solution, its pH is
Is lower than 0.1, the reaction becomes slower, and if higher than 8, the reaction becomes slower. Therefore, the range of 0.1 to 8 is more preferable.
If the pH of erythorbic acid is lower than 0.5, the reaction becomes extremely slow, so 0.5 or more is more preferable. When a palladium ammonium aqueous solution is used as the palladium-containing aqueous solution, when the pH is lower than 8, the precipitated particles are aggregated, and when it is higher than 13, the generation of ammonia gas is increased,
Since the reaction becomes slow, the range of 8 to 13 is more preferable, and if the pH of D-erythorbic acid is lower than 0.5, the reaction becomes extremely slow, so 0.5 or more is more preferable. Further, when the temperature during the reaction is lower than 10 ° C, the reaction is slow, and when the temperature exceeds 100 ° C, the fine palladium particles are aggregated. Therefore, the range of 10 to 100 ° C is more preferable. Examples of the present invention will now be described.

[0007]

Example 1 Palladium nitrate liquid [Pd (50 g / l)] 1
After diluting 00 ml with water to make 1 liter aqueous solution, 28%
The pH is adjusted to 3 by adding ammonia water. Also, D
-Erythorbic acid 100g is dissolved in water to make 500ml aqueous solution, then 28% ammonia water is added to adjust pH = 7. Here, the temperature of these two liquids is set to 30 ° C., the D-erythorbic acid solution is added to the aqueous solution of palladium nitrate with stirring, and the mixture is reacted for 30 minutes. The obtained palladium fine particles were filtered and washed, and the particle size distribution was measured and observed with an electron microscope. As a result, the palladium fine particles were almost spherical, and the average particle size was 0.5 μm, and the particle size distribution was as sharp as 70% in 0.3 to 0.8 μm.

[0008]

[Example 2] Palladium nitrate solution [Pd (50 g / l)] 1
After diluting 00 ml with water to make 1 liter aqueous solution, 28%
The pH is adjusted to 9 by adding ammonia water. Also, D
-Erythorbic acid 100 g is dissolved in water to make 500 ml aqueous solution, and then 28% ammonia water is added to adjust pH = 4. Here, the temperature of the two liquids is set to 50 ° C., the D-erythorbic acid solution is added to the palladium ammonium complex solution while stirring, and the reaction is performed for 60 minutes. The obtained palladium fine particles were filtered and washed, and the particle size distribution was measured and observed with an electron microscope. As a result, the fine palladium particles were almost spherical, the average particle size was 0.7 μm, and the particle size distribution was 0.5 to 0.9 μm.
It was a sharp one with 70% in m.

[0009]

[Example 3] Palladium nitrate liquid [Pd (50 g / l)] 50
After diluting ml with water to make 1 liter of aqueous solution, 28% ammonia water is added to adjust pH = 1. Also, D-
After dissolving 50 g of erythorbic acid in water to prepare a 500 ml aqueous solution, 28% ammonia water is added to adjust the pH to 9.
Here, the temperature of the two liquids was set to 60 ° C., and the D-erythorbic acid solution was added while stirring the palladium nitrate aqueous solution,
Incubate for 60 minutes. The obtained palladium fine particles are filtered,
After washing, particle size distribution measurement and electron microscope observation were performed.
As a result, the palladium fine particles were almost spherical, and the average particle size was 0.3 μm, and the particle size distribution was as sharp as 75% in 0.1 to 0.5 μm.

[0010]

[Example 4] Palladium nitrate liquid [Pd (50 g / l)] 50
After diluting ml with water to make 1 liter of aqueous solution, 28% ammonia water is added to adjust pH = 11. Also, D-
After dissolving 50 g of erythorbic acid in water to make a 500 ml aqueous solution, 28% ammonia water is added to adjust pH = 6.
Here, the temperature of the two liquids is set to 30 ° C., the D-erythorbic acid solution is added to the palladium ammonium complex solution while stirring, and the reaction is performed for 30 minutes. The obtained palladium fine particles were filtered and washed, and the particle size distribution was measured and observed with an electron microscope. As a result, the fine palladium particles were almost spherical with an average particle size of 0.2 μm and a particle size distribution of 0.1-0.4 μm.
It was a sharp one with 70%.

[0011]

Example 5 Palladium nitrate liquid [Pd (50 g / l)] 1
After diluting 00 ml with water to make 1 liter aqueous solution, 28%
The pH is adjusted to 5 by adding ammonia water. Also, D
-Sodium erythorbate 100g dissolved in water 500ml
Of water. Here, the temperature of the two liquids is set to 50 ° C., sodium D-erythorbate is added to the aqueous solution of palladium nitrate with stirring, and the mixture is reacted for 30 minutes. The obtained palladium fine particles were filtered and washed, and the particle size distribution was measured and observed with an electron microscope. As a result, the fine palladium particles were almost spherical, the average particle size was 0.7 μm, and the particle size distribution was 0.5 to 0.9.
It was a sharp one with 75% in μm.

[0012]

Example 6 Palladium nitrate liquid [Pd (50 g / l)] 1
After diluting 00 ml with water to make 1 liter aqueous solution, 28%
The pH is adjusted to 10 by adding ammonia water. Also, D
Dissolve 100 g of sodium erythorbate in water to make 1 liter of aqueous solution. Here, the temperature of the two liquids is adjusted to 70 ° C., sodium D-erythorbate is added to the palladium ammonium complex solution while stirring, and the mixture is reacted for 120 minutes.
The obtained palladium fine particles were filtered and washed, and the particle size distribution was measured and observed with an electron microscope. As a result, the palladium fine particles were almost spherical, and the average particle size was 1.2 μm, and the particle size distribution was as sharp as 70% in 1.0 to 1.4 μm.

[0013]

[Prior art example] Palladium nitrate liquid [Pd (50 g / l)] 100
After diluting ml with water to make 1 liter of aqueous solution, sodium hydroxide is added to adjust pH = 8. Further, while stirring this solution, 50 ml of an 80% hydrazine hydrate aqueous solution was added, and the mixture was stirred at 50 ° C. for 2 hours. The obtained palladium fine particles were filtered and washed, and the particle size distribution was measured and observed with an electron microscope. As a result, the palladium fine particles are amorphous
The average particle size was 1.8 μm, and the particle size distribution was as wide as 0.3 to 12 μm, and the particles were aggregated.

[0014]

As is apparent from the above description, the production method of the present invention uses D-erythorbic acid or D-erythorbates as a reducing agent in the method of producing palladium fine particles by reducing an aqueous palladium-containing solution. Thus, it is possible to manufacture fine palladium particles having a narrow width of the particle size distribution, which cannot be obtained by the conventional method, by controlling the particle size, and thus it can be said to be a revolutionary alternative to the conventional manufacturing method.

Claims (3)

[Claims] 1. A method for producing palladium fine particles by reducing a palladium-containing aqueous solution, wherein D- is used as a reducing agent.
A method for producing palladium fine particles, which comprises obtaining monodispersed palladium fine particles by using erythorbic acid or D-erythorbic acid salts. 2. The method for producing palladium fine particles according to claim 1, wherein the palladium-containing aqueous solution is a palladium nitrate aqueous solution, the pH of which is 0.1 to 8, and the pH of D-erythorbic acid is 0.5 or more. 3. The palladium-containing aqueous solution is a palladium ammonium complex solution, the pH of which is 8 to 13, and D-
The method for producing palladium fine particles according to claim 1, wherein the pH of erythorbic acid is 0.5 or more.