JP2000302411A - Production of monogermane - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the production of both a digermane and impurities derived from an acid and produce a high-purity product in high yield by using the acid which is a solid in an anhydrous state at normal temperatures and soluble in water when reacting germanium dioxide and a hydrogenating agent with the acid. SOLUTION: A hydrogenating agent is preferably an alkali metal borohydride, especially sodium borohydride, potassium borohydride or the like and boric acid, oxalic acid, citric acid, ascorbic acid, erythorbic acid, succinic acid, glutamic acid and nicotinic acid are preferred as an acid to be used. A 20-50 wt.% aqueous solution is preferred as the form of use in order to improve the mixing of the acid with an aqueous solution of a reactional raw material and stably produce a monogermane. The concentration of the germanium dioxide in the aqueous solution of the reactional raw material is preferably <=0.5 mol/L and the amount of the alkali metal borohydride is >=4 mol based on 1 mol of the germanium dioxide.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a method for producing monogerman gas. More specifically, the present invention relates to a method for producing monogermane with high purity and low cost while suppressing generation of impurities by using an acid having no volatile component.

[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.

The production of germane was reported in the early 1900's, but full-scale research began in the 1920's. Among them, a typical example of a monogermane formation reaction includes a stable germanium dioxide (GeO ₂ ) as a germanium source and an alkali metal borohydride as a hydrogenating agent which can be handled as an aqueous solution even in the air, and an acid aqueous solution. A method for obtaining monogermane using is well known. Since germanium dioxide itself is extremely expensive, it is desirable to produce monogermane in high yield. The term “high yield” as used herein means that the conversion rate of the raw material is high and that high-order germane by-products such as digermane and trigermane are less produced.

[0004] As an example of the production from germanium dioxide and alkali metal borohydride, for example, Pipe
r, Wilson [J. Inorg. Nu
cl. 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.

[0006] Since these use stable raw materials, the reaction operation is not complicated, but the yield is as low as 70% even under the optimum conditions, and the loss is large unless the unreacted components are collected. Industrially disadvantageous.

[0007] On the other hand, 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 this publication is a method in which an aqueous solution (second solution) obtained by adding an alkali metal borohydride to germanium dioxide and an aqueous alkali solution (first solution) is brought into contact with an aqueous sulfuric acid solution to obtain monogermane. 78% or more by adjusting the conditions such as the concentration of germanium dioxide in one 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 specific ranges. According to 90%
This is a method for obtaining monogermane with the above yield.

[0008]

SUMMARY OF THE INVENTION
No. 4,668,502, the conditions are adjusted and monogermane production experiments are carried out, and about 90% of the germanium dioxide used as the raw material is converted, so that monogermane is obtained in high yield. This was confirmed experimentally.

However, according to this method, a large amount of digermane is produced, and depending on the conditions, a yellow higher-order germane precipitate is formed in the reaction solution, so that the yield of monogermane is reduced. Since it is used, many impurities derived from acid are generated in the germane gas, and the purity is reduced. Therefore, the above situation is a problem that can be said to be fatal in order to industrially produce monogermane with high yield in high yield.

[0010]

SUMMARY OF THE INVENTION The present inventors presuppose a method for obtaining monogermane by reacting germanium dioxide with a hydrogenating agent and an acid, and to produce higher-order germanes including digermane and impurities derived from acids. We studied diligently how to produce monogermane with high yield and high purity at low cost and industrially stably.

As a result, the type of reaction is USP 4,66
As described in JP-A-8,502, as an example, an alkaline aqueous solution containing germanium dioxide and an alkali metal borohydride (hereinafter, referred to as an aqueous solution of a reaction raw material) is prepared in advance, which is a solid at room temperature in an anhydrous state and is dissolved in water. The inventors found that the method of reacting with a soluble acid was the easiest, and completed the present invention.

That is, the present invention relates to a method for producing monogermane by reacting an acid with germanium dioxide and a hydrogenating agent, wherein the acid used is a solid at room temperature in an anhydrous state and is soluble in water. The present invention relates to a method for producing monogermane, which is an acid.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.
Preferred examples of the hydrogenating agent used in the present invention include alkali metal borohydride, sodium borohydride, potassium borohydride and the like.

The acid used in the present invention has an effect of suppressing the formation of digermane in this reaction. These acids are solids at room temperature in an anhydrous state and soluble in water. For example, boric acid, oxalic acid, citric acid,
Ascorbic acid, erythorbic acid, succinic acid, glutamic acid, nicotinic acid and the like can be used. Above all, boric acid and citric acid are preferable because they have low toxicity and are easy to handle, and are relatively inexpensive. The acid used in the reaction may be added as it is in a solid state, but is preferably an aqueous solution of 20 to 50% by weight in order to improve the mixing with the aqueous solution of the reaction raw material and stably generate monogermane.

The reaction in the present invention is, as described above, a reaction between germanium dioxide, an alkaline aqueous solution containing a hydrogenating agent (described above, an aqueous solution of a reaction raw material), and an acid. Even if germanium dioxide and the hydrogenating agent 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. USP 4,668,502
As described in the publication, an alkali metal borohydride powder as a powder may be added to a predetermined ratio of an aqueous solution of germanium dioxide metal hydroxide, or a predetermined concentration of an aqueous alkali solution may be prepared in advance. Germanium dioxide powder and alkali metal borohydride powder may be added. Sodium hydroxide, potassium hydroxide, calcium hydroxide and the like are used as the metal hydroxide.

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 hydrogenating agent is not particularly limited, but monogermane is difficult to handle and it is desirable to simplify the purification process. In this sense, it is preferable to use a raw material having a relatively high purity.

The reaction raw material aqueous solution is reacted with an acid to form monogermane. 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, 5
If the temperature exceeds 0 ° C., the amount of higher-order germane including digermane increases, which is not preferable. 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. The present invention is a method for industrially and stably producing monogelmane of high purity and high yield from inexpensive raw materials, and can be used in batch operation or continuous operation.

As described above, in order to produce monogermane of high purity in an industrially stable and safe manner, the acid used in the reaction must be an acid which is solid at room temperature in an anhydrous state and soluble in water. There must be.

[0021]

The present invention will be described below in detail with reference to examples. Germanium dioxide is a reagent manufactured by Gemco Co., Ltd., sodium borohydride, potassium hydroxide, boric acid, oxalic acid, citric acid, sulfuric acid, phosphoric acid and acetic acid are all reagents manufactured by Wako Pure Chemical Industries, and water is ion-exchanged water. used. 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.
Further, 30 g of boric acid and 120 g of ion-exchanged water were added to another 1-L glass Erlenmeyer flask and stirred to prepare a 20% supersaturated boric acid aqueous solution (3.20 mol / L).

A 1-liter Teflon reactor having a lid capable of sealing was charged with 150 g of a 20% supersaturated boric acid aqueous solution, and the lid was closed. 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 is supplied to this reactor using a plunger pump, and is 2.7.
Helium was supplied quantitatively at a rate of 30 cc / min at a rate of cc / min and as a gas carrier. Monogerman is generated at the start of the supply of the aqueous solution of the reaction raw material, and the outlet gas of the Teflon-made reactor is analyzed by a temperature rising analysis type gas chromatography (GC-made by Shimadzu) equipped with a heat conduction type detector (TCD).
8APT) The separation column was analyzed by Porapak-P, and it was confirmed that monogermane and hydrogen were the main components, and as shown in Table 1, generation of digermane and almost no impurity derived from acid were generated. . The yield of monogermane was 97.3%. The reaction was stopped when about 500 g of the aqueous solution of the reaction raw material was supplied for about 3 hours, but it was confirmed that the generation of gas was stopped within a few seconds after the supply of the aqueous solution of the reaction raw material was stopped. The gas generation rate was stable at 160 to 170 L / min during the reaction period.

Example 2 The acid added to the aqueous solution of the reaction raw material was changed to oxalic acid, and 30 g of oxalic acid and 120 g of ion-exchanged water were placed in a 1-L glass Erlenmeyer flask.
Was added and stirred, and a 20% aqueous solution of supersaturated oxalic acid (2.22 mol) was added.
1 / L), and the reaction was carried out in the same manner as in Example 1 except that 150 g of a 20% supersaturated oxalic acid aqueous solution was charged into a Teflon-made reactor having a capacity of 1 L and capable of being sealed. Table 1 shows the results of gas chromatography analysis.

Example 3 The acid to be added to the aqueous solution of the reaction raw material was changed to citric acid, and 1 L
45 g of citric acid and 105 g of ion-exchanged water were added to a glass Erlenmeyer flask, and stirred to prepare a 30% aqueous solution of supersaturated citric acid (1.56 mol / L). The reaction was carried out in the same manner as in Example 1 except that 150 g of a 30% aqueous solution of supersaturated citric acid was charged. Table 1 shows the results of gas chromatography analysis.

COMPARATIVE EXAMPLE 1 The acid added to the reaction raw material aqueous solution was changed to sulfuric acid, and the volume was 1 L.
40% sulfuric acid in a Teflon reactor with a lid
The reaction was carried out in the same manner as in Example 1 except that 50 g (4.10 mol / L) was charged. Gas was generated along with the supply of the reaction raw material aqueous solution, and the results of gas chromatography analysis are shown in Table 1. It was also found that the amount of digermane produced and the impurities derived from the acid were significantly increased.

Comparative Example 2 The acid added to the aqueous solution of the reaction raw material was changed to phosphoric acid, and the volume was 1 L.
25% phosphoric acid in a Teflon reactor with a lid
The reaction was carried out in the same manner as in Example 1 except that 50 g (2.55 mol / L) was charged. Gas was generated along with the supply of the reaction raw material aqueous solution, and the results of gas chromatography analysis are shown in Table 1. It was also found that the amount of digermane produced and the impurities derived from the acid increased.

Comparative Example 3 The acid added to the aqueous solution of the reaction raw material was changed to acetic acid, and the volume was 1 L.
30% acetic acid in a Teflon reactor with a lid
The reaction was carried out in the same manner as in Example 1 except that 50 g (5.00 mol / L) was charged. Gas was generated along with the supply of the reaction raw material aqueous solution, and the results of gas chromatography analysis are shown in Table 1. Further, it was found that impurities derived from the acid increased.

[0028]

[Table 1]

[0029]

Industrial Applicability The present invention relates to a method for producing monogermane by reacting germanium dioxide with a hydrogenating agent and an acid. The monogermane is solid at room temperature in an anhydrous state in an acid used in the reaction and is soluble in water. A method for producing monogermane, characterized by using an acid. As described above, this method can suppress the formation of digermane and the formation of impurities derived from acids, and can safely produce monogermane with high purity in high yield. Therefore, the purification step can be simplified, and as a result, monogermane can be obtained at low cost. Considering all the above, the effect of the present invention is considered to be great.

Claims (5)

[Claims] 1. A method for producing monogermane by reacting an acid with germanium dioxide and a hydrogenating agent, wherein the acid used is an acid-free solid at room temperature and soluble in water. A method for producing monogermane, comprising: 2. The method according to claim 1, wherein the hydrogenating agent is an alkali metal borohydride. 3. The water-soluble acid which is solid at room temperature in an anhydrous state and soluble in water is boric acid, oxalic acid, citric acid, ascorbic acid, erythorbic acid, succinic acid, glutamic acid and nicotinic acid. Manufacturing method. 4. The method according to claim 1, wherein the temperature at which the acid is reacted with the germanium dioxide and the hydrogenating agent is in the range of 0 to 50 ° C. 5. The monogermane yield of at least 90.
2. The production method according to claim 1, wherein the amount is not less than% by weight.