JP2002180140A - Method for refining sponge platinum - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for refining sponge platinum by which the grade of chlorine can remarkably be reduced, e.g. to <=0.1 wt.% without performing hydrogen reduction. SOLUTION: In the method, ammonium chloroplatinate is heated at 350 to 450 deg.C to decompose a chlorine component and ammonia. Next, the temperature is further raised to heat sponge platinum at 850 to 950 deg.C. Then, the sponge platinum is cleaned at a pulp concentration of <=400 g/L two or more times without its pulverization.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for purifying sponge platinum from ammonium chloroplatinate and to a method for purifying platinum.
In particular, the present invention relates to a technique for efficiently removing chlorine adhering to sponge platinum to obtain high-quality sponge platinum.

[0002]

2. Description of the Related Art Conventionally, when purifying sponge platinum,
Ammonium chloroplatinate was thermally decomposed at about 400 ° C. and further heated to about 800 ° C. in hydrogen gas. This last heating was performed to reduce chlorine, which is a component other than platinum, with hydrogen, and to sinter powdery platinum constituting the sponge to facilitate removal.

[0003]

By the way, sponge platinum purified by the above-mentioned method has a chlorine content of 0.1 to 0.1%.
0.5% by weight, but lower the chlorine grade,
We want to manufacture products that meet the needs of consumers. Further, in the above-mentioned prior art, the second heating is performed in a hydrogen gas atmosphere, but there has been a request to avoid using hydrogen gas in order to pay attention to handling. Accordingly, the present invention is to provide a method for purifying sponge platinum, which can drastically lower the chlorine grade without hydrogen reduction, for example, can reduce the chlorine grade to 0.01% by weight or less. The purpose is.

[0004]

The present inventors have studied the causes of chlorine contained in platinum sponge and found that chlorine evaporated in the final heating adheres again to the surface of the filament of platinum sponge. The inference was reached. Then, when the sponge platinum after heating was washed with water, it was found that the chlorine quality was dramatically reduced.

The present invention has been made based on the above findings. (1) Ammonium chloroplatinate is heated at 350 to 450 ° C. to decompose chlorine and ammonia, and then further heated to 850 to 850 ° C. The sponge platinum is heated at 950 ° C. and then 400 g / L without grinding the sponge platinum.
A method for purifying sponge platinum which is washed at least twice with the following pulp concentrations. (2) A method for purifying platinum sponge, comprising drying immediately after washing two or more times in (1).

According to the present invention, the first stage 350 to 450
Impurities such as chlorine and ammonia decomposed by heating at ℃ and Se and the like are evaporated by heating at 850 to 950 ° C. in the second stage, and platinum is sintered. At this time, the evaporated chlorine adheres again to the sponge platinum, but the chlorine can be efficiently removed by washing the sponge platinum with water. Here, the ratio of sponge platinum to water is desirably 400 g / L or less. In the present invention, it is desirable to dry the sponge platinum quickly after washing with water in order to prevent contamination of impurities.

[0007]

Embodiment 1 Next, the present invention will be described in more detail with reference to embodiments. Ammonium chloroplatinate was heated in the air at 400 ° C. for 2 hours, and then the heating furnace was heated to 900 ° C. and held for 3 hours. 3,000 g and 4,000 g of two kinds of sponge platinum from different lots thus obtained were collected.
Next, 10 L of pure water was poured into the washing tank, and sponge platinum was put into each of the tanks and washed with stirring for 30 minutes. Thereafter, filtration was performed, and several g of the sponge platinum after washing and filtration was collected and analyzed as a sample for an analysis sample. This operation was performed twice. The second washing was carried out by replacing the pure water with new one each time.

[0008] Table 1 shows the Cl grade in the sponge platinum before washing, after the first washing, and after the second washing.

[0009]

[Table 1]

According to Table 1, under the condition that the ratio of sponge platinum to the pure water amount in Example 1 is 300 g / L, the Cl grade in the sponge platinum is 0.40% before washing and is 0.1% in the first washing.
02% and <0.01% after repeated washing
Down to Further, under the condition that the ratio of the sponge platinum to the pure water amount in Example 2 was 400 g / L, the Cl grade in the sponge platinum was reduced from 0.4% to 0.03% by the first washing, and further washing was repeated. And <0.01%, satisfying less than 0.01% of the control value. On the other hand, in Comparative Example 1 of Table 1, since the pulp concentration of the sponge platinum was as high as 500 g / L, it was as high as 0.05% in the first washing.
Even in the second washing, the value was not as low as 0.02%.

As shown in Table 1, when the pulp concentration of the sponge platinum is 400 g / L or less, if the number of times of washing is twice, the chlorine quality in the sponge platinum becomes 0.01.
It is less than 10% by weight and has sufficient quality. On the other hand, when the washing was not performed, the chlorine grade of the sponge platinum was 0.1 to 0.4% by weight, which was considerably lower than that of the present invention.

[0012]

As described above, in the method for purifying sponge platinum of the present invention, ammonium chloroplatinate is used in an amount of 350 to 4%.
Heat at 50 ° C to decompose chlorine and ammonia,
Next, the temperature was further increased to heat the sponge platinum at 850 to 950 ° C., and then the sponge platinum was heated twice or more at 400 / L
By washing with water at the following low pulp concentration of sponge platinum, high-grade sponge platinum with low chlorine grade can be obtained without performing hydrogen reduction.

Claims (2)

[Claims] (1) Ammonium chloroplatinate is heated at 350 to 450 ° C. to decompose chlorine and ammonia, and then heated to 850 to 950 ° C. to heat the sponge platinum. 40 without crushing
A method for purifying sponge platinum, comprising washing at least twice with a pulp concentration of 0 g / L or less. 2. A method for purifying sponge platinum, comprising drying immediately after washing two or more times according to claim 1.