JP3309402B2 - Method for producing high purity phosphorus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing high-purity phosphorus. More particularly, the present invention relates to a method for producing high-purity phosphorus which is used as a raw material for a compound semiconductor and particularly has a very small arsenic content.

[0002]

2. Description of the Related Art High-purity phosphorus is an important material as an additive for compound semiconductors such as InP, GaP, GaAs _x P _{1 -x,} and silicon semiconductors. In particular, recently, with high integration of electronic materials, high-purity phosphorus from which impurities in phosphorus have been largely removed has been demanded. However, arsenic is homologous to phosphorus and is the most difficult to remove among the impurities in phosphorus. Conventionally, various methods for removing arsenic from phosphorus have been studied, and a cleaning method using an acid such as nitric acid, an alkali cleaning method, a distillation purification method, an alloy vacuum distillation method, a hydrogen treatment purification method, and the like are known. Among these, the alloy vacuum distillation method is a powerful method for removing many impurities including arsenic and sulfur which are difficult to separate and remove from phosphorus, and has a low melting point and phosphorus such as Al, Pb, In, and Tl. One or a mixture of two or more metals that easily alloy with arsenic or sulfur in the alloy is heated at a temperature above the melting point of the metal to alloy with the impurities, and then phosphorus is depressurized at a temperature below the melting point of the metal used. It is a method of distillation
14685).

[0003]

In the conventional vacuum distillation method for alloys, when heat treatment is performed on phosphorus and a metal, it is necessary to heat the metal to the melting point of each metal or more. The melting point of each metal is 660 ° C for Al, 327 ° C for Pb, In
157 ° C., Tl 304 ° C., Bi 271 ° C., Sb 631 ° C., etc. Of these metals, Al has the highest arsenic removal effect.However, when Al is used, heat treatment is performed at a temperature of about 700 ° C. or more, so that aluminum phosphide is generated and phosphorus is red-phosphorized at high temperatures. The recovery rate under reduced pressure distillation is reduced. Further, the apparatus also requires heat-resistant equipment, and the processing operation is complicated and difficult. The nitric acid cleaning method has high arsenic removal efficiency,
The yield is quite low, around 50%, due to the elution of phosphorus during processing. Further, since a large amount of nitric acid waste liquid mixed with phosphoric acid is produced, waste liquid treatment is a problem (Japanese Patent Laid-Open No. 49-95891). All other treatment methods have low arsenic removal efficiency. An object of the present invention is to provide a method for producing high-purity phosphorus that has solved the problems of the conventional method.

[0004]

According to the present invention, iodine is added to crude yellow phosphorus by adding at least one equivalent of iodine and heating, and reacting arsenic and iodine in phosphorus at a temperature of 300 ° C. or less. There is provided a method for producing high-purity phosphorus, which comprises recovering phosphorus by distillation under reduced pressure after arsenic conversion.

[0005] Arsenic is homologous to phosphorus and their properties are very similar. Incidentally, it is generally known that the yellow phosphorus molecule (P ₄ ) has a form in which P is disposed at each vertex of a tetrahedron, but arsenic in yellow phosphorus probably has one of the Ps of the tetrahedron. It is presumed that it exists in a state replaced with one. Therefore, it is difficult to separate arsenic in yellow phosphorus by a simple method such as distillation. Accordingly, the present invention provides a method for producing arsenic iodide having a boiling point (403
(° C / 1 atm) is higher than the boiling point of yellow phosphorus (280 ° C / 1 atm), add iodine to crude yellow phosphorus and heat it, and then react arsenic in yellow phosphorus with iodine. After converting to arsenic iodide (AsI ₃ ), distillation is performed under reduced pressure to recover phosphorus. In this case, phosphorus and arsenic can be easily separated because the difference in boiling point between yellow phosphorus and arsenic iodide is large.

The iodine source used in the present invention may be any of solid or gaseous iodine alone and iodine compounds such as potassium iodide, phosphorus iodide and hydrogen iodide.
In order to prevent components other than iodine from being mixed, it is preferable to use solid or gaseous iodine alone. The amount of iodine to be added in the present invention is in the range from the equivalent of the stoichiometric ratio at which arsenic in phosphorus reacts with iodine to produce AsI ₃ to 10,000 times. If the amount of iodine added is less than the above equivalent, arsenic in phosphorus cannot be completely converted to AsI ₃ . Also,
If the stoichiometric ratio exceeds 10,000 times, the arsenic removing effect is not changed, and the phosphorus yield is undesirably lowered.

The reaction temperature used in the method of the present invention is 300 ° C. or lower, preferably 280 ° C. (boiling point of yellow phosphorus). When the temperature exceeds 300 ° C., the amount of yellow phosphorus scattered due to the boiling of yellow phosphorus increases, and a change to red phosphorus starts, which is not preferable. The reaction is carried out at a temperature of 44 ° C. or higher (melting point of yellow phosphorus).
Below 44 ° C., yellow phosphorus does not reach the melting point and the reaction with iodine does not occur uniformly. At a temperature of 44 ° C. to 280 ° C., there is almost no yellow phosphorus that evaporates and scatters and little red phosphorus that is a by-product. If solid iodine is used as the iodine source, it is the melting point of iodine.
It is desirable to carry out the reaction at a temperature of 4 ° C. (113.7 ° C.) or higher in order to allow the reaction to proceed uniformly.

The reaction starts early after the addition of iodine,
The reaction time is desirably 1 hour or more so that the reaction proceeds uniformly throughout. The longer the reaction time, the more uniform the reaction.However, when the reaction temperature is high, the amount of red phosphorus produced as a by-product increases, the yield of yellow phosphorus decreases, and the effect of adding iodine reaches saturation. It is preferably within the range.

After completion of the reaction, yellow phosphorus is recovered by distillation under reduced pressure. At this time, the distillation temperature is preferably equal to or lower than the boiling point of the produced AsI ₃ (403 ° C./1 atm) and is as low as possible. Since AsI ₃ and yellow phosphorus have a large difference in boiling point, they can be easily separated to obtain high-purity phosphorus.

Examples 1 to 12 Iodine having a stoichiometric ratio shown in Table 1 was added to arsenic-containing crude yellow phosphorus, and the mixture was heated under a non-oxidizing atmosphere and heated to a temperature shown in Table 1. And time. After reaction, 1-10mm
Distillation was performed under reduced pressure to not more than Hg, and yellow phosphorus was recovered at about 120 ° C. Residual arsenic concentration (ppm) and yield in the obtained phosphorus
(%) Are shown in Table 1. Example 1 is provided for comparison.
You.

[0011]

Comparative Example 1 Under a nitrogen atmosphere, 150 parts by weight of crude yellow phosphorus containing arsenic and 30 parts by weight of nitric acid in a quartz flask
1000 parts by weight were added, and the mixture was heated and stirred for 3 hours to be oxidized.
After separating the nitric acid solution from the oxidized product, yellow phosphorus was recovered, washed with warm water, and dried. Then, the mixture was heated to 100 to 115 ° C. under reduced pressure of 1 to 5 mmHg, and distilled for 1 hour while supplying nitrogen gas at a rate of 5 cc / min. Table 1 shows the results.

[0012]

Comparative Example 2 30 g of crude yellow phosphorus and 3 g of Al were placed in a flask of a distillation apparatus, heated in a nitrogen stream from 400 ° C. to the melting point of Al for 2 hours, and then allowed to cool to distill yellow phosphorus. Table 1 shows the results.

[0013]

Table 1 例 Example Iodine addition amount Reaction temperature Time Arsenic content ( (ppm) Yield (stoichiometric ratio) (℃) (hr) Raw material recovered yellow phosphorus (%) ─────────────────────────── ─────── 1 0.5 150 5 61 25.5 92 2 1.0 150 5 61 2.3 86 3 20.0 150 5 61 0.9 80 4 200.0 150 5 61 <0.1 75 5 1000.0 150 5 61 <0.1 70 6 200.0 150 1 61 0.5 79 7 200.0 150 5 61 <0.1 75 8 200.0 150 16 61 <0.1 69 9 200.0 50 5 61 0.3 79 10 200.0 150 5 61 <0.1 75 11 200.0 250 5 61 0.1 75 12 200.0 400 5 61 0.1 63 ──── ────────────────────────────── Comparative example Treatment method Arsenic content (ppm) Yield Raw material Recovered yellow phosphorus (%) ─ ───────────────────────────────── 1 Nitric acid cleaning method 82 0.4 45 2 Vacuum distillation of alloy 60 4.2 92.4 ─────────────────────────────────

[0014]

According to the present invention, iodine is added to yellow phosphorus to cause arsenic and iodine in phosphorus to react with each other to produce arsenic iodide having a high boiling point. Can be separated and collected. By this vacuum distillation, impurities such as Si and Fe can be simultaneously removed in addition to arsenic. Furthermore, there is no large amount of waste liquid as in the nitric acid cleaning method. The yield is also considerably higher at 70-90% compared to about 50% for the nitric acid washing method.

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Claims (1)

(57) [Claims] 1. A method of adding at least one equivalent of iodine to crude yellow phosphorus, heating the mixture, and reacting arsenic and iodine in the phosphorus at a temperature of 300 ° C. or less to form arsenic iodide. A method for producing high-purity phosphorus, which comprises recovering.