JPS6016368B2 - Phosphorus purification method - Google Patents

Description

Detailed Description of the Invention The present invention relates to a method for purifying yellow phosphorus, in which impurities contained in crude yellow phosphorus are oxidized using a mixed acid consisting of nitric acid and sulfuric acid, and then purified with dilute nitric acid. Relating to a method of removing by washing with water.

High purity phosphorus is important for use in the production of phosphorus compounds as materials in electronics and semiconductors. In particular, impurities in the diffusion raw material for semiconductor doping are 10-6
% or less, extremely high purity is required. Generally, the purity of commercially available phosphorus is approximately 99%, and it contains a considerable amount of phosphorus, sulfur, selenium, iron, carbon compounds, etc., and these impurities are removed by ordinary distillation operations and alkaline cleaning methods. Substantial removal is difficult with purification methods. A method for purifying crude yellow phosphorus containing such impurities is '1) Controlling oxidation of yellow phosphorus impurities with 10 to 50% nitric acid at 45 to 100 qo, and then or simultaneously steam distillation (retention). Kosho 39-2462
3), ■ After oxidizing yellow phosphorus impurities with nitric acid and removing the oxidized impurities by washing with water, approximately 0.5 to 2 skin/Hg
A method has been proposed in which distillation is carried out under reduced pressure while blowing an inert gas into the liquid (Jikai Publication No. 49-95891). However, the method of {11] requires a long time for distillation, has an extremely low yield per unit time, and has a removal rate of less than 50% of phosphorus, which is particularly difficult to remove among impurities. Method 2) involves oxidizing with nitric acid, washing with water, and then distilling under reduced pressure while blowing inert gas.
The major drawbacks are that the process is complicated and impurities other than heavy metals cannot be removed. This invention was developed as a result of many experiments in order to find a method for producing high-purity phosphorus at a high yield per unit time and for almost completely removing the phosphorus component, which is the most difficult to remove. By oxidizing the impurities in the crude phosphorus with a mixed acid of nitric acid and sulfuric acid, and washing and removing the oxidized impurities with dilute nitric acid and water, the yield of high-purity phosphorus per unit time is extremely high, and phosphorus as an impurity is removed. was found to be almost completely removed.

When attempting to remove impurities in sulfuric acid by simply using either nitric acid or sulfuric acid, for example, if the concentration is as low as 2% by weight of nitric acid or 4% by weight of sulfuric acid, most of the phosphorus content will be removed. cannot be removed.

If the acid concentration is higher than the above, the removal rate of Wakachirin will improve (approximately 20-30%), but then these acids will react violently not only with the impurities in the phosphorus but also with the phosphorus in the main body.
It is very dangerous and at the same time most of the phosphorus is lost by reacting with the acid. Based on the above knowledge, the present invention has been developed based on the above knowledge that a mixed acid, which is a combination of nitric acid and sulfuric acid in an appropriate ratio, is surprisingly effective in removing impurities in scales because the hydrogen ion concentration increases even if the acid concentration is low. As a result of further research, we have completed the present invention.

The nitric acid used to oxidize impurities in crude yellow phosphorus is 6 to 1
Mix 15% to 3% by weight of sulfuric acid and the total acid concentration as a mixed acid (nitric acid molar concentration, tensulfuric acid molar concentration, hereinafter referred to as total acid concentration) is 3.5 to 6.5 mol. The oxidation treatment is carried out at a temperature of 45 to 100 qo, preferably 45 to 60 qo. If a total acid concentration of 3.5 mol or less is used, the purification effect will decrease, while if a total acid concentration of 6.5 mol or more is used, the reaction between phosphorus and mixed acid will increase, resulting in phosphorus loss. I don't like it because it costs a lot. In addition, the concentration of nitric acid is 6 to 1% by weight, and the concentration of sulfuric acid is 15 to 3% by weight, and the mixing ratio of nitric acid and sulfuric acid is 1:1 to 1:4 for the same reason as the total acid concentration. If the above-mentioned concentration of nitric acid and sulfuric acid is not used, the removal rate of impurities will be reduced.On the other hand, if an acid with a concentration higher than the above-mentioned concentration is used, the impurity removal rate will be good, but the reaction with phosphorus will become violent and it will be dangerous. However, it is economically disadvantageous. The amount of mixed acid used varies depending on the purity of the target phosphorus and the amount of impurities in the raw crude phosphorus, but yellow phosphorus 100
100g or more, practically 500-1000g
is used.

The temperature of the oxidation treatment is 4, which is higher than the melting point of yellow phosphorus (44qo).
5o0 or more is required, but the reason why the upper limit is limited to 100qo is because as the temperature rises, the reaction between tsuric acid and phosphorus becomes more intense, which is not only dangerous but also results in increased loss of phosphorus. It is.

The time required for oxidation treatment is 5 to 1 feeding time in the case of 10 females of crude phosphorus, and the washing after oxidation treatment is performed at a temperature of approximately 50 to 60 oo and approximately 1 to 4 weight hours after separating the mixed acid. % nitric acid, and then 4 to 5 times with about 50 to 60 qo of purified hot water, both of which are about 5 times the amount of Rindo, and the washing and cooling are repeated alternately.

According to this method, by oxidizing 30 pieces of crude yellow phosphorus for about 1 hour, it is possible to reduce the 9 pm of sulfur contained in the basket scales to 1 ppm or less, and to make the yield of purified phosphorus about 70%. Incidentally, the processing time for the same amount of yellow phosphorus using the previously mentioned known method [1] is 12q hours. As explained above, according to the present invention, the acid concentration and treatment temperature are completely safe, and the quality of the purified phosphorus obtained and the yield per unit time are excellent, and its industrial significance is Extremely large. Examples will be described below.

Comparison 1 A rod-shaped crude yellow phosphorus containing 8 pm boronate stored in water in a quartz flask was mixed with 9-20% by weight (1.
5-3 moles) of nitric acid, or about 21-38 wt.% (2.5
~5 mol) of sulfuric acid into each 30 females at 70 pm.
It was oxidized by burning it in a molten state for a while.

After that, the solidified phosphorus was cooled to room temperature and separated from nitric acid or sulfuric acid, and washed and cooled repeatedly, once with about 100 g of dilute nitric acid of about 3% by weight at about 6,000 ml, and five times with purified warm water. I did the cleaning. The phosphorus in the purified phosphorus obtained was analyzed, and its removal rate was calculated from the phosphorus before and after treatment. The results are shown in Table 1. Table 1 Example 1 In a quartz flask, about 2 µm of rod-shaped crude yellow phosphorus containing 8 pm of phosphorus was stored in water.
．． Add 5 to 100% by weight of nitric acid and about 8 to 40% by weight of sulfuric acid to a molar ratio of 1 to 0.5 to 10 in a concentrated acid solution and melt at about 70 oo for 3.5 hours. I then performed oxidation treatment.

The oxidized product is cooled to room temperature to solidify the phosphorus, and then the lacrimal acid is separated from the phosphorus by diluting, and diluted nitric acid (approximately 3
Weight%) once with about 100g, 4 times with about 10 females of warm purified water,
Cleaning was performed by alternately repeating washing and cooling. The silica in the purified silane was analyzed, and the removal rate was calculated from the difference in the amount of silica before and after the treatment. The results are shown in Table 2. Second
As is clear from Table 2, when the total acid concentration is 4.5 to 6.5 mol and the molar ratio of muddy acid is 1 nitric acid to 2 to 3 sulfuric acid, the boronic removal rate is 95% or more under suitable conditions. showed that.

Example 2 20 g of crude yellow phosphorus containing 86 ppm of phosphorus was mixed with 300 g of a mixed acid consisting of 55 g of about 61% nitric acid, 100 g of sulfuric acid of about 61.6%, and 145 g of purified water. When oxidation treatment was performed, the amount of phosphorus in purified phosphorus was 0.08 ppm.
About 10.5 g of purified phosphorus was obtained.

The processing conditions and procedures are the same as in Example 1. The concentration of nitric acid in the boric acid is approximately 12.5% by weight, and the concentration of sulfuric acid is approximately 25% by weight. Example 3 20 g of rod-shaped crude yellow phosphorus containing the components shown in Table 3 was mixed with about 1% by weight of nitric acid and about 62
Lacrimal acid 300, which is a mixture of 1:1 weight percent of sulfuric acid
Purified phosphorus 1 shown in Table 3 was obtained by performing oxidation treatment at 60°C for 2 hours using
I got a hammer.

No phosphorus was detected in the purified yellow phosphorus, and all other impurities were below pm. Table 3 Impurities (ppm) Raw materials As SbSn Zn Cu Fe Ca K
CZ S Si Mg AZ Na B Crude phosphorus 10
030 9 11 1 35 12 53 28 33
38 3 39 30 2 Purified phosphorus ND ND N
D.O. 7ND 1 2 1 1 2
2 0.1 0.2 1 ND table note) ND = indicates not detected.

Example 4 30 pieces of crude phosphorus having the composition shown in Table 3 of Example 3 was added to about 61
300% nitric acid and about 61.1% sulfuric acid 450',
In addition, oxidation treatment was carried out at 55°C for about 2 hours using 1.8% of falconic acid consisting of 10% purified water, and the like. The three systems were operated in the same manner as in Example 1 to remove impurities in the machine and obtain 20% purified phosphorus.

In addition, the nitric acid concentration in the mixed acid is 11.8%, and the sulfuric acid concentration is 19.6%.
%. The results are shown in Table 4 in comparison with the impurity quality of commercially available products with high purity. Table 4 Impurities (ppm) As Zn Cu Fe Ca K S Si M
g Am Na B ND of the present invention o. 8ND
2 2 o. 4 3 1 0.3 0.3 0.
6 ND purified commercial product A I I ND 4
4 0.7 4 3 0.3 0.5 3 0
．． 05″ B O.5 5 3 4 4
2 3 3 0.2 1 2 ND It is clear from Table 4 that the purified phosphorus of the present invention has fewer impurities and is superior to commercially available products.

Claims (1)

[Claims] 1. Mix 6 to 18% by weight of nitric acid and 15 to 38% by weight of sulfuric acid at a molar ratio of 1:1 to 1:4 so that the total acid concentration as a mixed acid (nitric acid molar concentration + sulfuric acid molar concentration) 3.5～
Crude yellow phosphorus is converted into 4
A method for purifying phosphorus, which comprises treating at 5 to 100°C and separating impurities oxidized by a mixed acid.