JPS60186408A - Preparation of high-purity phosphorus - Google Patents

Abstract

PURPOSE:To prepare phosphorus having extremely high purity, by passing a crude phosphine gas through a reaction pipe consisting of a thermal decomposition zone of arsine, a cooling zone, and a thermal zone of phosphine. CONSTITUTION:A mixed gas of the phosphine 1 prepared as a by-product in production of sodium hypophosphite and H2 2 as a carrier gas is fed from the conduit 4 to the arsine decomposition pipe 5 having the built-in heater 6 and the interior packed with one or more metals such as Zn, Mg, Cu, etc. to be easily reacted with As. The pipe is heated by the heater at <=the decomposition temperature of phosphine of <=450 deg.C, arsine (AsH3) contained in a phosphine gas is reacted with the metal such as Zn, etc., decomposed and fixed to give As compounds, which are removed. A mixed gas of phosphine and H2 from which arsine is removed is passed through the cooling zone 5, cooled, introduced into the phosphine decomposition zone 5'' packed with a substance such as quartz wool, etc. inert to phosphine, phosphine is heated by the heater 6 at 600-1,000 deg.C, decomposed, and phosphorus having extremely high purity of 99.999% is recovered in the ampul 9.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing high purity phosphorus that can be used as a material for semiconductors.

High-purity phosphorus is an important substance used in the production of phosphorus compounds for electronics and semiconductors, such as indium, gallium, boron, aluminum or mixtures thereof, and at least! A purity of around 119.999% is required.

Conventionally, the commonly produced elemental phosphorus is, for example, phosphate rock (
It is produced by reacting calcium phosphate or fluoroapatite with silica and coke under high temperature conditions in an electric furnace and recovering it as yellow phosphorus. The purity of the elemental phosphorus obtained in this way is approximately 89%, and it contains a considerable amount of impurities such as arsenic, sulfur, selenium, iron, lead, copper, aluminum, and carbon compounds, and cannot be used as the above-mentioned material.

Moreover, these impurities cannot be substantially removed by normal distillation operations.

Therefore, apart from the above, the conventional method for producing high-purity phosphorus is
Several methods are known, including steam distillation of yellow phosphorus and distillation of yellow phosphorus while blowing an inert gas such as nitrogen, helium, or argon (Japanese Patent Laid-Open No. 413-958
No. 91), a method of adding aluminum or aluminum and lead to crude yellow phosphorus, heating it at a temperature from 400°C to the melting point of aluminum, and then distilling it under reduced pressure (Special Publication No. 44-
14H5), but all of them have problems in their operation, and it is difficult to sufficiently improve the purity of phosphorus.

The present inventors used crude phosphine gas containing mainly arsine as an impurity as a raw material and thermally decomposed it under specific temperature conditions to produce high-purity elemental phosphorus from a completely different perspective from the above method. The present invention was completed based on the discovery that it could be recovered.

That is, the gist of the present invention is that when crude phosphine gas is thermally decomposed to produce elemental phosphorus, the gas introduction section is an arsine thermal decomposition zone, and the intermediate section is a cooling zone and a cooling zone at a lower temperature than the zone. The final section forms a temperature gradient as a phosphine thermal decomposition zone, and the gas introduction section is filled with a metal that can generate arsenide, and the other zones are filled with phosphine and an inert substance. The present invention relates to a method for producing high-purity phosphorus, which is characterized by introducing phosphine gas and recovering elemental phosphorus through thermal decomposition.

Yellow phosphorus, which is generally produced industrially by reducing phosphate rock, contains trace amounts of iron, copper, nickel, aluminum, lead, etc., but these metals are difficult to form into hydrides, so they are treated as gaseous substances. is not generated. On the other hand, phosphorus, arsenic, etc. easily form hydrides and gasify.

Therefore, since metals have already been substantially removed from phosphine even if it is a crude gas, it is most rational from an industrial perspective to recover high-purity phosphorus from such phosphine. This is based on the above principle.

Thus, in the present invention, the crude phosphine gas mainly refers to a gas in which arsenic hydride, that is, arsine is essentially mixed.

Such crude phosphine gas is produced exclusively from elemental phosphorus, mainly yellow phosphorus, but the present invention can be applied to phosphine produced by any production method as a raw material. It will be done.

(1) Phosphine by-produced during the production of sodium hypophosphite: P4 + 3 NaOH+ 3 H2O+p)+3 ↑
+3 NaH2PO2... (1) (2) Phosphine produced as a by-product during the production of sodium phosphite: 3P4 + 12H20+4 NaOH→8PH3↑+
4NaHPO3... (2) [3) Phosphine produced by hydrolysis of phosphorus: 2 P4. +
12H20→5 PI(3↑+31(3PO4...
...(3) or (4) Bosfin etc. produced by yellow phosphorus electrolysis method. However, in the present invention,
From an industrial perspective, it is most advantageous to effectively utilize phosphine, which is a by-product during the production of sodium hypophosphite. Such phosphine gases include arsine (AsHs) as described in 1.
Although nitrogen, oxygen, carbon dioxide gas, etc. are mixed in, most of the impurities contained in the crude yellow phosphorus obtained by other methods are removed without being mixed into the gas.

The present invention introduces such crude phosphine gas into a tubular heating zone in an oxygen-free state, heats it above the decomposition temperature of phosphine (approximately 450°C), thermally decomposes it, and selectively vaporizes elemental phosphorus. The objective is to recover elemental phosphorus by cooling it.

Hereinafter, typical embodiments of the present invention will be described based on the drawings.

In Fig. 1, phosphine gas is metered using a flow meter 3 from a phosphine pump 1 filled with crude phosphine gas, and hydrogen is passed through a conduit 4 as a carrier gas from a hydrogen pump 2 to decompose arsine in a heating zone in which air has been replaced in advance. Introduced into tube 5. This arsine decomposition tube 5 has a heater 6 attached to the outside. In other words, this heating zone is a gas introduction section and serves as an arsine thermal decomposition zone. Therefore, this heating zone is above the temperature at which thermal decomposition of arsine occurs or at which it can react with the filler metal to form arsenide, but the maximum temperature is above the temperature at which phosphine begins to thermally decompose, preferably by about 450°C. It is desirable that the temperature be controlled; if the maximum temperature exceeds the temperature at which phosphine starts to thermally decompose, the yield of recovered elemental phosphorus will be reduced and evaporation of the filler metal will tend to occur, which is undesirable. Note that the thermal decomposition temperature of phosphine is usually around 450°C,
This is not necessarily constant in relation to residence time. Therefore, the temperature at which phosphine starts to thermally decompose varies somewhat depending on the residence time of the gas. Further, this arsine decomposition tube 5 is filled with a metal capable of producing arsenide. Such metals include, for example, one or more metals selected from zinc, magnesium, copper, etc., and there is no need to particularly limit the size, shape, etc., as long as they can be filled.

The crude phosphine introduced by the heating zone is
Arsenic removal is carried out by fixing arsenic produced by thermal decomposition of mixed arsine with the filling metal, or by a reaction between arsine or decomposed arsenic and the filling metal to form metal arsenide.

The gas then passes into the intermediate cooling pipe 5'. This cooling pipe 5' is composed of a cooling outer layer 7 provided with an introduction lower 'and an outlet lower' for introducing a cooling medium such as cold air or water, and is controlled to a temperature lower than the temperature of the heating zone. The reason for this is to completely eliminate the risk of metals that may generate a small amount of arsenide being mixed into the gas due to evaporation, and to ensure a complete arsenic removal reaction. If a difference is formed, there is no need to provide this cooling layer 7.

This cooling pipe 5' is the same as the next phosphine decomposition pipe 5'',
To increase their efficiency, phosphine is loaded with inert substances as fillers. As the filler, a desired material such as quartz glass, magnetic lachsing, quartz wool, etc. may be selected.

Furthermore, the introduced gas moves to the next phosphine cracking tube 5'', which is configured as a phosphine thermal decomposition zone.Up to this point, the introduced gas is only completely purified phosphine gas, and the phosphine cracking tube 5'' A heater 6 is attached to the outside of the phosphine decomposition tube 5 in the same way as the phosphine decomposition tube 5, and it is a heating zone kept at a temperature higher than 450'C, which is the thermal decomposition temperature of phosphine, so that the thermal decomposition of phosphine is effective. The temperature is controlled as it should be.

As described above, one of the features of the present invention is that the above-mentioned temperature gradient is always provided when thermally decomposing the crude phosphine gas, and another feature is that the arsenic removal is completely carried out at the gas introduction part. metal is charged as a filler.

The temperature in this phosphine thermal decomposition zone must be at least 450°C or higher, but in most cases a range of 600°C to 1000°C is preferred, as this is related to residence time in terms of phosphorus recovery.

According to numerous experiments conducted by the present inventors, it has been found that an average residence time of 3 minutes or less at a temperature equal to or higher than the thermal decomposition temperature of phosphine is sufficient.

That is, the higher the heating temperature, the shorter the residence time, and vice versa. For example, at a yield of 85%, it takes less than 20 seconds at a decomposition temperature of about 1000°C;
℃, it is within about 100 seconds, and even if higher purity phosphorus is desired, a residence time of 3 minutes in the above sense is sufficient at most.

In this way, the elemental phosphorus produced by thermal decomposition is controlled at about 50°C by the thermistor 11. Collected as on the other hand,
Nitrogen gas, carbon dioxide gas, hydrogen gas for substitution or carrier use in the heating zone, etc. contained in the boss fin are removed through the off-gas outlet 10.

Furthermore, the yellow phosphorus recovered as elemental phosphorus can be converted into red phosphorus and recovered as necessary. In this case, a converter is provided to convert yellow phosphorus into red phosphorus and easily recover it using a conventional method.

As described below, the method of the present invention makes it easier to purify phosphorus compared to the conventional distillation method for yellow phosphorus.
Crude phosphine gas as a raw material can be used without any restrictions, so if phosphine, which is a by-product in the production of sodium hypophosphite, is effectively used, it is an extremely rational method to produce high-purity phosphorus from an industrial perspective. I can say it.

The present invention will be described in more detail below with reference to Examples.

1 Example 1 A reaction vessel equipped with a stirrer, a thermometer, nitrogen gas introduction, a dropping funnel, and a reflux condenser equipped with a gas discharge pipe at the tip was equipped with 30 g of yellow phosphorus, a small amount of an inert dispersion aid, and 500 m of water. The reactor was heated to 70°C to 75°C and stirred to disperse yellow phosphorus into fine particles. Next, 102.4 g of a 25% aqueous sodium hydroxide solution was added dropwise to this dispersion over 1 hour to cause a reaction. As the reaction progressed, good generation of phosphine was observed along with the production of sodium hypophosphite.

After the dropwise addition was completed, the mixture was further heated at 75°C to 80°C for 45 minutes and stirred to complete the reaction. When the generated phosphine is collected, a gas containing an average of 52.6% by volume of phosphine10. i was obtained. The yield of this phosphine was 84.
This corresponds to 9%. Since the crude phosphine gas thus obtained contained a large amount of water, it was dehumidified through an activated carbon column and sealed in a cylinder to obtain crude phosphine as a raw material.

In thermally decomposing this crude phosphine gas, 2 Using the apparatus shown in FIG. 1, the following conditions were set.

The arsine decomposition tube 5 was filled with metal pieces, and water at about 10°C was introduced into the cooling zone from the introduction lower ' and was discharged from the outlet lower ' for cooling. The tube 5'' was filled with a quartz ring, and the phosphine decomposition tube 5'' was heated to a temperature of soo'c.
It was kept warm at C.

Using such a device, the temperature of the arsine decomposition tube 5 and the filling metal are changed, and the above crude phosphine gas (100 ppnz &amp; was thermally decomposed, and the generated elemental phosphorus was recovered in ampoule 9 (recovery temperature 50°C). Other gases CCO2, N2, H2 contained in phosphine gas PH3
) was discharged out of the yarn from the off-gas discharge port 10. The analytical values of the yellow phosphorus thus obtained are as shown in Table 1, and the yellow phosphorus was of extremely high purity and could be fully applied as phosphorus for electronic materials.

Note 1) The flow rate of phosphine gas is 50 to 150 mKL/win.

Note 2) Arsine was analyzed using arsenic test paper using the gate site method.

Example 2 The filling of the arsine cracking tube 5 was sandy zinc, the temperature of this heating zone was 400°C, and the temperature of the heating zone of the phosphine cracking tube 5'' was 1.
Using the same equipment as in Example 1 except that the temperature was set at 000°C, crude phosphine gas (containing 150 ppm of arsine) was supplied together with hydrogen gas at a flow rate of 7 On+u/main to thermally decompose the phosphine and convert elemental phosphorus. Recovered. When the recovered phosphorus was similarly analyzed, it was found to be highly pure phosphorus with an arsine content of 0.0 lppm or less.

[Brief explanation of the drawing]

FIG. 1 is a process diagram showing one embodiment of the present invention. 1... Phosphine cylinder, 2... Hydrogen cylinder, 3
...Flowmeter, 4...Conduit, 5...Arsine decomposition tube, 5'...Cooling pipe, 5''...
- Phosphine decomposition tube, 6... Heater, 7... Cooling outer layer, 7'... Inlet, 7''... Outlet, 8...
・Hot water, 9... Ampoule for collecting yellow phosphorus, 10... Off gas outlet, 11... Thermistor. Applicant Nihon Kagaku Kogyo Co., Ltd. Agent Yutaka 1) Yoshio 5

Claims (5)

[Claims] (1) When producing elemental phosphorus by thermally decomposing crude phosphine gas, the gas introduction part is an arsine thermal decomposition zone, the middle part is a cooling zone at a lower temperature than the zone, and the final part is a phosphine thermal decomposition zone. forming a temperature gradient as a zone,
In addition, crude phosphine gas is introduced into a heating tube whose gas introduction section is filled with a metal capable of producing arsenide, and other zones are filled with phosphine and an inert substance, and the crude phosphine gas is thermally decomposed to recover elemental phosphorus. A method for producing high-purity phosphorus, which is characterized by: (2) The method for producing high-purity phosphorus according to claim 1, wherein the arsine thermal decomposition zone has a maximum temperature up to the temperature at which phosphine starts thermal decomposition. (3) The method for producing high-purity phosphorus according to claim 1, wherein the metal capable of producing arsenide is one or more metals selected from zinc, magnesium, and copper. (4) The method for producing high-purity phosphorus according to claim 1, wherein the phosphine thermal decomposition zone is up to 1000°C. (5) The method for producing high-purity phosphorus according to claim 1, wherein the crude phosphine is a phosphine produced as a by-product from the production process of sodium hypophosphite.