JPH10291804A - Production method of germane - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce high purity monogermane in a high yield, inexpensively, industrially and stably by specifying a pH of a reaction soln. after reacting a metal hydroxide aq. soln. of germanium dioxide and alkali metal borohydride with an acid. SOLUTION: A reaction starting material aq. soln. is obtained by dissolving 1 mol germanium dioxide and >=4 mol alkali metal borohydride in the aq. soln. containing the metal hydroxide of more than two chemical equivalent per 1 mol germanium dioxide so that a germanium dioxide concn. becomes <=0.5 mol/L, preferably <=0.3 mol/L. An acid such as sulfuric acid, phosphoric acid, acetic acid and propionic acid is added to the reaction starting material aq. soln., and the mixture is allowed to react at 0-50 deg.C under the condition in which the pH of the aq. soln. after reaction becomes <=7 till a conversion of the germanium dioxide becomes >=90%, preferably >=93%. In this way, the production of digermane is reduced and a purifying process is simplified.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a method for producing germane gas. More specifically, the present invention relates to a method for efficiently and inexpensively producing monogermane while suppressing generation of higher-order germane.

[0002]

2. Description of the Related Art Monogermane is mainly used as a raw material for amorphous silicon germanium thin films.
This has the property that the absorption efficiency of light on the long wavelength side is higher than that of amorphous silicon thin films.Therefore, as the development of solar cells with high conversion efficiency for long wavelength light and photosensitive drums with high long wavelength light sensitivity progresses, Monogerman The demand for is expected to increase significantly. For this reason, there is a need for a technique for industrially stably producing high-purity monogermane, which can be used as a raw material of an amorphous silicon germanium thin film, and needless to say, at a low cost. Germanic production was reported in the early 1900's, but full-scale research began in the 1920's.

[0003] The types of Germane-forming reactions so far are roughly classified into the following three types. 1) Reaction of magnesium germanide (Mg ₂ Ge) with an acid or ammonium halide For example, Krans, Carney, J. et al. Am. Che
m. Soc. Vol. 56, P765 (1934) 2) Reaction of germanium tetrachloride (GeCl ₄ ) with a hydrogenating agent For example, see Finholt, Bond, J. et al. Am. Che
m. Soc. Vol. 69, P2692 (1947) 3) Reaction of germanium dioxide (GeO ₂ ) with a hydrogenating agent See, for example, Piper, Wilson, J. et al. Inorg.
Nucl. Chem. Vol. 4, P22 (195
7)

[0004] Metal germanium, germanium tetrachloride and germanium dioxide, which have been used as raw materials for germane, do not have a great difference in price in view of germanium. It is more advantageous to use raw materials that are easy to handle. In other words, rather than using germanium tetrachloride as a raw material that hydrolyzes in the air to generate a mist of hydrochloric acid, stable germanium dioxide can be handled as a germanium source, and it can be handled as an aqueous solution in the air as a hydrogenating agent. Since alkali metal borohydride is used as a raw material and germanium dioxide itself is extremely expensive, a method for producing monogermane with high yield is desirable.

[0005] The term "high yield" as used herein means that the conversion of the raw material is high and the by-products of higher-order germane such as digermane and trigermane are small.

As an example of the production from germanium dioxide and an alkali metal borohydride, for example, Pipe
r, Wilson et al. [J. Inorg. N
ucl. Chem. Vol. 4, P22 (195
7)]. They report that using sodium borohydride as a hydrogenating agent and hydrogenating germanium dioxide dissolved in hydrobromic acid gave a yield of 73% under optimal conditions.

A report by Drake, Jolly et al. [J. Chem. Soc. 2807 (1962)].
Is a method in which an alkali aqueous solution in which germanium dioxide and potassium borohydride are dissolved is brought into contact with an acid, and it is reported that a yield of 73% was obtained under optimal conditions when acetic acid was used as the acid. Since these use stable raw materials, the reaction operation is not complicated, but the conversion rate is as low as 70% even under the optimum conditions, and the loss is large if the unreacted components are not recovered. It is disadvantageous.

On the other hand, the disclosure of a method capable of obtaining monogermane in high yield from similar raw materials is disclosed as follows.
USP 4,668,502 (1987). The method disclosed in the publication is a method of contacting an aqueous solution (second solution) obtained by adding an alkali metal borohydride to an alkaline aqueous solution of germanium dioxide (first solution) with a sulfuric acid aqueous solution to obtain monogermane, By setting the conditions such as the concentration of germanium dioxide in the first solution, the ratio of alkali / germanium dioxide, the amount of alkali metal borohydride added to the first solution, the acid concentration, and the reaction temperature to a specific range, 78% or more can be achieved. According to the example,
This is a method for obtaining monogermane with a maximum yield of 97%.

[0009]

SUMMARY OF THE INVENTION
The conditions were adjusted according to the example of JP-A-4,668,502, and a germane generation experiment was carried out to confirm that about 90% of the germanium dioxide used as the raw material was converted, and that this method was a method for obtaining germane in high yield. Confirmed experimentally.

However, in this method, a large amount of digermane is generated, and depending on the conditions, a precipitate of yellow higher-order germane is formed in the reaction solution, so that the yield of monogermane is reduced. At the same time, it was also clarified that the generation rate was not stable and the production of germane continued for a while even after the supply of the raw material was stopped. Germane is self-degrading, and several accidents due to this property have been reported. Considering that it is ignitable and is a highly toxic gas, it is necessary to handle it very carefully, and the above situation is a fatal problem because monogermane is manufactured industrially stably.

[0011]

Means for Solving the Problems The inventors of the present invention presupposed a method for obtaining germane by reacting germanium dioxide with an alkali metal borohydride and an acid, and in a high yield, at a low cost and industrially stably. We studied diligently on the method for producing germane.

As a result, the type of reaction is USP 4,66
No. 8,502, as an example, it is easiest to prepare an alkaline aqueous solution containing germanium dioxide and an alkali metal borohydride in advance (hereinafter referred to as a reaction raw material aqueous solution) and react it with an acid. confirmed.

[0013] Further, if the production of higher-order germane including digermane is suppressed to a minimum, the purification process is simplified, and from the judgment that monogermane can be obtained at low cost, it is possible to stably produce industrially. In order to carry out the process, further studies were carried out from the judgment that it is preferable that the rate of generation of germane be stable and that the generation of germane be stopped immediately upon stopping the supply of the aqueous solution of the reaction raw material. As a result, when the pH of the reaction solution of the reaction raw material aqueous solution and the acid is in the range of 7 or less, the amount of digermane produced can be suppressed to a low level, and no higher-order germane precipitate is produced. It has been clarified that the formation reaction of benzene progresses, and that the production of germane is stopped in a short time even if the supply of the reaction raw material aqueous solution is stopped. On the other hand, when the pH is in the range of 7 or more, a large amount of digermane is generated and a precipitate of higher-order germane is formed in the reaction solution. It has been found that the production of germane is continued for a while even after the supply of is stopped, and the present invention has been completed.

That is, the present invention relates to a method for obtaining germane by reacting germanium dioxide with an aqueous metal hydroxide solution of an alkali metal borohydride to obtain germane, wherein the pH of the reaction solution after the reaction is 7 or less. The present invention relates to a method for producing germane.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.
The present invention is a method for producing monogermane of high purity from an inexpensive raw material in a high yield and in an industrially stable manner, and is applicable to both batch operation and continuous operation. As described above, the reaction is a reaction between an alkali aqueous solution containing germanium dioxide and an alkali metal borohydride (described above, an aqueous solution of a reaction raw material) and an acid. Even if germanium dioxide and the alkali metal borohydride are mixed, no reaction proceeds in the alkaline aqueous solution, and thus the method for preparing the reaction raw material aqueous solution is not particularly limited. As described in US Pat. No. 4,668,502, a powder of alkali metal borohydride powder may be added to a predetermined ratio of an aqueous solution of metal hydroxide of germanium dioxide, or an aqueous solution of an alkali having a predetermined concentration may be prepared in advance. Here, germanium dioxide powder and alkali metal borohydride powder may be added.

In the present invention, the concentration of germanium dioxide in the reaction raw material aqueous solution is preferably 0.5 mol / L or less, more preferably 0.3 mol / L or less, and the metal hydroxide is contained in 1 mol of germanium dioxide. It is preferable that the alkali metal borohydride is in a range of 4 moles or more with respect to 1 mole of germanium dioxide. Outside this range, the conversion of germanium dioxide is reduced, so that monogermane cannot be produced in high yield, that is, at low cost.

Here, the chemical equivalent of the metal hydroxide is defined as the amount of a base that neutralizes an acid containing one equivalent of hydrogen acting as an acid. For example, in the case of an alkali metal hydroxide such as sodium hydroxide, 2 chemical equivalents are 2 moles, 2 equivalents for alkaline earth metal hydroxides such as calcium hydroxide
Is a mole.

The purity of germanium dioxide, metal hydroxide and alkali metal borohydride is not particularly limited, but monogermane is difficult to handle and it is desirable to simplify the purification process, so that generation of impurities is suppressed as much as possible. In this sense, it is preferable to use a material having a relatively high purity.

The metal hydroxide and the alkali metal borohydride are not particularly limited in substance. The former is sodium hydroxide, potassium hydroxide, calcium hydroxide or the like simply because it is inexpensive, and the latter is sodium borohydride. Hydride or potassium borohydride are preferred materials.

The reaction raw material aqueous solution is reacted with an acid to form monogermane. There is no particular limitation on the type of acid,
For example, inorganic acids such as sulfuric acid and phosphoric acid, and organic acids such as acetic acid and propionic acid can be suitably used. However, considering the purification of monogermane, it is preferable to avoid volatile acids such as hydrochloric acid. Further, the reaction is preferably performed at a temperature of 0 to 50 ° C. If the reaction temperature is lower than 0 ° C., the conversion of germanium dioxide decreases, which is not preferable. Also, 50 ° C
Exceeding this is not preferable because the amount of higher-order germane including digermane increases. As a method of reacting the reaction raw material aqueous solution with the acid, the reaction raw material aqueous solution may be supplied into a predetermined amount of the acid, or the acid and the reaction raw material aqueous solution may be continuously contacted.

However, in the present invention, conditions must be selected so that the pH of the reaction solution of the reaction raw material aqueous solution and the acid is 7 or less, preferably 5 or less. This is the most important point of the present invention. Here, the reaction solution is defined as the remaining aqueous solution from which gas is no longer generated after the reaction of the reaction raw material aqueous solution with the acid, and specifically, generation of hydrogen due to decomposition of germane gas and alkali metal borohydride. It means the remaining or stopped aqueous solution.

In US Pat. No. 4,668,502, the concentration of sulfuric acid is limited to the range of 1.5 to 3.0 mol / L, but the absolute amount is not particularly limited. However, in the description of the optimum conditions of the examples, GeO ₂ : H ₂ SO
It is specified that the ratio of ₄ ranges from 1: 1 to 1: 2. However, when a reaction between the aqueous solution of the reaction raw material and the acid is carried out so as to satisfy this condition, the pH of the reaction solution is about 11 and the reaction solution is in an alkaline region. Therefore, when the reaction raw material aqueous solution and the acid are continuously contacted, the amount of digermane generated is large, the gas generation rate is not stable, and even if the reaction between the raw material and the acid is stopped, the reaction solution is kept for a while. There is a problem that the production of germane is continued.

When the reaction raw material solution is gradually added to a predetermined amount of acid by changing the reaction mode, the digerman content is low while the pH of the reaction solution is in the range of 7 or less. Monogermane is stably generated, and when the supply of the aqueous solution of the reaction raw material is stopped, the generation of germane is stopped in a few seconds. However, the addition is continued and the pH becomes 7 or more. Increases, the rate of gas generation becomes unstable, the reaction between the reaction raw material aqueous solution and the acid is stopped, germane continues to be generated from the reaction solution for a while, and the amount of digermane increases Such a problem occurs.

Although the details of this reason cannot be clarified,
Alkali metal borohydride is decomposed immediately in an aqueous solution of an acid, but is relatively stable in an aqueous alkaline solution, and is considered to be caused by a slower decomposition rate. That is, in order to produce monogermane of high purity in a high yield and industrially stably, the reaction raw material aqueous solution and the acid must be reacted under the condition that the aqueous solution after the reaction has a pH of 7 or less. is there. In order to achieve this condition range, there is no problem in carrying out the present invention, even if the concentration of the acid is increased or the absolute amount of the acid at a specific concentration is increased.

[0025]

The present invention will be described below in detail with reference to examples. Note that germanium dioxide, sodium borohydride, potassium hydroxide, and sulfuric acid all used reagents manufactured by Kanto Chemical Co., and water used was ion-exchanged water. The percentages are based on weight unless otherwise specified. Example 1 532 g of a 2.8% aqueous potassium hydroxide solution was prepared in a 1 L glass Erlenmeyer flask, and 7.2 g of germanium dioxide powder and sodium borohydride powder 1 were added thereto.
5.6 g was added, stirred and dissolved to prepare a reaction raw material aqueous solution. Under these conditions, the germanium dioxide concentration is 0.13
mol / L, potassium hydroxide concentration 0.5 mol / L, potassium hydroxide / germanium dioxide ≒ 3.8, sodium borohydride / germanium dioxide ≒ 6.
A 27% sulfuric acid aqueous solution (about 3 mol / L) was prepared in another 1-L glass Erlenmeyer flask. A 27% sulfuric acid aqueous solution is placed in a Teflon reactor with a lid that can be sealed with a capacity of 1 L.
g, the lid was closed, and a reaction raw material aqueous solution supply line, a thermometer, carrier nitrogen, and a generated gas outlet line were connected.
The reactor was allowed to stir with a stirrer, and the reactor was immersed in a warm bath to adjust the reaction temperature to 25 to 35 ° C.

An aqueous solution of the reaction raw material was quantitatively supplied to this reactor at a rate of 2.7 cc / min using a plunger pump, and nitrogen was supplied as a gas carrier at a rate of 30 cc / min. A gas was generated at the start of the supply of the aqueous solution of the reaction raw material, and the gas was analyzed by gas chromatography. The gas was mainly composed of monogermane and hydrogen, and IR analysis confirmed that digermane was hardly generated. did. The reaction is about 3 hours, about 500 g of aqueous solution of reaction raw materials
It stopped when the supply was completed, but it was confirmed that the generation of gas was stopped within a few seconds after the supply of the aqueous reaction raw material was stopped. In addition, the gas generation rate during the reaction period is 160 to 170 L / m.
It was stable in. After the completion of the reaction, the pH of the remaining solution was 2 or less, and no formation of a precipitate was observed. When germanium in the remaining aqueous solution was analyzed by ICP (inductively coupled plasma analysis), the conversion of germanium dioxide was 98%.

Comparative Example 1 A sulfuric acid aqueous solution supply line was further connected to the Teflon container used in Example 1, and the other conditions were the same as in Example 1.
The prepared aqueous solution of the reaction raw material was quantitatively and continuously supplied at a rate of 2.8 cc / min and the aqueous solution of sulfuric acid at a rate of 0.2 cc / min. Under these conditions, sulfuric acid / germanium dioxide ≒ 2. Gas was generated at the start of the supply of both aqueous solutions, and gas chromatography revealed that monogermane gas and hydrogen were the main components, and IR analysis showed that the amount of digermane produced was significantly increased as compared with Example 1. Was. The reaction is carried out for about 3 hours, about 500 g of the aqueous solution of the reaction raw material and 4
It stopped when 5 g was supplied, but the gas generation rate during the reaction period varied from 100 to 200 L / min. The generation of gas continued even after the supply of both liquids was stopped. When the composition of the generated gas was analyzed by gas chromatography at 120 minutes after the supply was stopped, it was confirmed that monogermane was present. After the completion of the reaction, the pH of the remaining solution was 10 or more, and it was confirmed that a yellow precipitate was formed in the reaction solution. After the liquid was filtered, the components of the precipitate were analyzed by XRF (fluorescence X
Line analysis), it was found that the main component was germanium. The conversion of germanium dioxide was 86%.

Example 2 A 13.5% aqueous sulfuric acid solution (about 1.5 mol / L) was prepared in a 1-L glass Erlenmeyer flask, and about 60 g of an aqueous sulfuric acid solution was charged into a Teflon reactor and capped. PH into this reactor
The same procedure as in Example 1 was conducted except that a meter was provided, and the aqueous solution of the reaction raw material was 2.2 cc / m2 using a plunger pump.
in speed and 30 c of nitrogen as gas carrier
It was supplied quantitatively at c / min. Gas was generated when the supply of the reaction raw material aqueous solution was started. The gas generation rate was stable at 130 to 150 L / min during the region where the liquid had a pH of 7 or less.
Increased, and entered into the region of pH 7 or more, and the gas generation rate was gradually slowed down, and there was a tendency that the dispersion became severe.

FIG. 1 shows the relationship between the change in pH and the flow rate of the produced gas in Example 2. FIG. 2 is an IR spectrum of a gas generated when the reaction solution has a pH of 7 or less, and FIG. 3 is an IR spectrum of a gas generated when the reaction solution has changed to a pH of 7 or more. The circles in FIGS. 2 and 3 indicate the absorption of digermane, and it is clear that the gas generated in the region of pH 7 or more in FIG. 3 has a large content of digermane. The reaction was stopped when about 280 g of the aqueous solution of the reaction raw material was supplied for about 2 hours, but the gas generation continued even after the supply of the aqueous solution of the reaction raw material was stopped. P of residual liquid after completion of reaction
H is about 10, and the conversion of germanium dioxide is 92
%Met.

[0030]

According to the present invention, there is provided a method for reacting an aqueous alkali metal hydroxide solution of germanium alkali metal borohydride with an acid under conditions where the reaction solution has a pH of 7 or less. According to this method, as described above, the generation rate of germane is stable, and the generation of germane is immediately stopped when the supply of the aqueous solution of the reaction raw material is stopped, so that the reaction for generating monogermane can be stably performed. In addition, since the amount of digermane produced is small, the purification step can be simplified, so that monogermane can be obtained at low cost. Considering all of the above,
The effect of the present invention is considered to be great.

[0031]

[Brief description of the drawings]

FIG. 1 shows a relationship between a pH change and a generated gas flow rate in Example 2.

FIG. 2 is an IR spectrum of a gas generated when the reaction solution is in a pH range of 7 or less.

FIG. 3 is an IR spectrum of a gas generated when the reaction solution has a pH of 7 or more.

[Explanation of symbols]

 D: Absorption of digermane

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[Procedure amendment]

[Submission date] June 6, 1997

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0026

[Correction method] Change

[Correction contents]

An aqueous solution of the reaction raw material was quantitatively supplied to this reactor at a rate of 2.7 cc / min using a plunger pump, and nitrogen was supplied as a gas carrier at a rate of 30 cc / min. A gas was generated at the start of the supply of the aqueous solution of the reaction raw material, and the gas was analyzed by gas chromatography. The gas was mainly composed of monogermane and hydrogen, and IR analysis confirmed that digermane was hardly generated. did. The reaction is about 3 hours, about 500 g of aqueous solution of reaction raw materials
It stopped when the supply was completed, but it was confirmed that the generation of gas was stopped within a few seconds after the supply of the aqueous reaction raw material was stopped. During the reaction period, the gas generation rate is 160 to 170 cc /
It was stable at min. After the completion of the reaction, the pH of the remaining solution was 2 or less, and no formation of a precipitate was observed. When germanium in the remaining aqueous solution was analyzed by ICP (inductively coupled plasma analysis), the conversion of germanium dioxide was 98%.

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0027

[Correction method] Change

[Correction contents]

Comparative Example 1 A sulfuric acid aqueous solution supply line was further connected to the Teflon container used in Example 1, and the other conditions were the same as in Example 1.
The prepared aqueous solution of the reaction raw material was quantitatively and continuously supplied at a rate of 2.8 cc / min and the aqueous solution of sulfuric acid at a rate of 0.2 cc / min. Under these conditions, sulfuric acid / germanium dioxide ≒ 2. Gas was generated at the start of the supply of both aqueous solutions, and gas chromatography revealed that monogermane gas and hydrogen were the main components, and IR analysis showed that the amount of digermane produced was significantly increased as compared with Example 1. Was. The reaction is carried out for about 3 hours, about 500 g of the aqueous solution of the reaction raw material and 4
It stopped when 5 g was supplied, but the gas generation rate during the reaction period varied from 100 to 200 cc / min. The generation of gas continued even after the supply of both liquids was stopped. When the composition of the generated gas was analyzed by gas chromatography at 120 minutes after the supply was stopped, it was confirmed that monogermane was present. The pH of the remaining solution after the reaction is 10
As described above, it was confirmed that a yellow precipitate was formed in the reaction solution. After the liquid was filtered, the components of the precipitate were analyzed by XRF (X-ray fluorescence analysis), and it was found that the precipitate contained germanium as a main component. The conversion of germanium dioxide was 86%.

[Procedure amendment 3]

[Document name to be amended] Statement

[Correction target item name] 0028

[Correction method] Change

[Correction contents]

Example 2 A 13.5% aqueous sulfuric acid solution (about 1.5 mol / L) was prepared in a 1-L glass Erlenmeyer flask, and about 60 g of an aqueous sulfuric acid solution was charged into a Teflon reactor and capped. PH into this reactor
The same procedure as in Example 1 was conducted except that a meter was provided, and the aqueous solution of the reaction raw material was 2.2 cc / m2 using a plunger pump.
in speed and 30 c of nitrogen as gas carrier
It was supplied quantitatively at c / min. Gas was generated when the supply of the reaction raw material aqueous solution was started. The gas generation rate was stable at 130 to 150 cc / min during the region where the liquid had a pH of 7 or less.
As H increased and entered the region of pH 7 or more, the generation rate of gas was gradually slowed down, and there was a tendency that the dispersion became severe.

Claims (9)

[Claims] 1. A method for obtaining germane by reacting germanium dioxide with an aqueous metal hydroxide solution of an alkali metal borohydride, wherein the pH of the reaction solution after the reaction is 7 or less. Germanic manufacturing method. 2. The method according to claim 1, wherein the pH of the reaction solution is 5 or less. 3. The concentration of germanium dioxide is 0.5 m.
The method according to claim 1 or 2, wherein the metal hydroxide is at least 2 chemical equivalents per mol of germanium dioxide and the alkali metal borohydride is at least 4 mol per mol of germanium dioxide. 4. The concentration of germanium dioxide is 0.3 m.
The method according to claim 1 or 2, wherein the metal hydroxide is at least 2 chemical equivalents per mol of germanium dioxide and the alkali metal borohydride is at least 4 mol per mol of germanium dioxide. 5. The method according to claim 1, wherein the reaction temperature ranges from 0 to 50 ° C. 6. The method according to claim 1, wherein the reaction is a batch operation. 7. The method according to claim 1, wherein the reaction is a continuous operation. 8. The method according to claim 1, wherein the conversion of germanium dioxide is at least 90% or more. 9. The method according to claim 1, wherein the conversion of germanium dioxide is at least 93% or more.