JP2002173306A - Method of manufacturing metal hydrogen complex compound - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of obtaining an alkali metal salt of tetrahydro boric acid or tetrahydride aluminic acid with high yield under a mild condition of a room temperature and an atmospheric pressure by using a raw material, which is easily obtained and easy to handle. SOLUTION: The tetrahydroborate or tetrahydride aluminate expressed by the general formula: M1(M2H4) (M1 represents an alkali metal and M2 represents boron or aluminum) is manufactured by allowing the alkali metal salt of boric acid or aluminic acid to bring into contact with a metal hydride in a fine powder state to react with each other while giving mechanical energy.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a novel method for producing an alkali metal hydride complex compound, and more specifically, to a method for producing an alkali metal salt of tetrahydroboric acid or tetrahydridoaluminic acid by a simple treatment and with high efficiency. It is about the method.

[0002]

2. Description of the Related Art Alkali metal tetrahydroborate such as sodium tetrahydroborate Na [BH ₄ ] and alkali metal tetrahydride aluminate such as lithium tetrahydridoaluminate Li [AlH ₄ ] are used as reducing or hydrogenating agents. Widely used.

Hitherto, as a method for producing an alkali metal tetrahydroborate, two moles of an alkali metal hydride, for example, sodium hydride, and 1 mole of an alkali metal salt of a tetraborate, for example, 1 mole of borax, are mixed in a hydrogen atmosphere under anhydrous conditions. At 400 ° C. for reaction (Japanese Patent Publication No. 42-2
No. 7256), a method of reacting anhydrous borax with sodium hydride or metallic sodium at a temperature of 200 to 600 ° C. and a hydrogen pressure of 1 to 50 atm in the presence of aluminum or an alloy thereof (Japanese Patent Publication No. 43-2221). Publication), a method of heating a mixture of a borate of an alkali metal or an alkaline earth metal and a hydride of an alkali metal or a mixture of an alkali metal and hydrogen at 450 to 500 ° C. (Japanese Patent Publication No. 47-48117) is known. Have been. The most common method for producing an alkali metal tetrahydride aluminate is a method in which anhydrous aluminum chloride is reacted with excess lithium hydride in diethyl ether.

However, all of these methods require complicated operations in the preparation of raw materials, use difficult-to-handle raw materials such as metallic sodium, or organic solvents such as diethyl ether, and furthermore, under hydrogen pressure or high temperature. There are problems such as the necessity of using a specific apparatus for the treatment below, and this has not always been satisfactory as an industrial production method.

[0005]

DISCLOSURE OF THE INVENTION The present invention relates to a process for producing tetrahydroboric acid or tetrahydridoaluminic acid in a high yield under mild conditions at room temperature and atmospheric pressure using easily available and easy-to-handle materials. The purpose of the present invention is to provide a method for obtaining an alkali metal salt.

[0006]

DISCLOSURE OF THE INVENTION The present inventors have eagerly developed a simple and efficient production method which can be commonly applied to an alkali metal salt of tetrahydroboric acid or tetrahydridoaluminic acid. As a result of repeated studies, they have found that the object can be achieved by using mechanochemical technology, and have accomplished the present invention based on the knowledge.

Accordingly, the present invention is an alkali metal salt of boric acid or aluminate and the metal hydride is contacted with fine powder, characterized in that the reaction is performed while applying a mechanical energy, the general formula M ₁ [ M ₂ H ₄ ] (wherein M ₁ is an alkali metal, M ₂ is boron or aluminum) and a method for producing a tetrahydroborate or a tetrahydridoaluminate.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the method of the present invention, an alkali metal borate or an alkali metal aluminate and a metal hydride are used as raw materials. Examples of the alkali metal borate include alkali metal salts of metaboric acid, tetraboric acid, and pentaboric acid, and any of these can be used. Examples of such alkali metal salts include NaBO ₂ , KBO ₂ , LiBO ₂ , Na ₂ B ₄ O ₇ ,
K ₂ B ₄ O ₇ , Li ₂ B ₄ O ₇ , NaB ₅ O ₈ , KB ₅ O ₈ , Li
B ₅ O _{8 and the} like can be mentioned. Examples of the alkali metal aluminate include NaAlO ₂ , KAlO ₂ ,
LiAlO _{2 and the} like can be mentioned.

These alkali metal borates and alkali metal aluminates are preferably dried by heating to reduce the water of crystallization to 1 or less, and in particular, those obtained by pulverizing anhydrous substances into fine powder. The average particle size is 100 μm or less,
Preferably, a range of 100 nm or less is selected.

Alkali metal tetrahydroborate M
₁ [BH ₄ ] or alkali metal tetrahydride aluminate M ₁ [AlH ₄ ] (wherein M ₁ has the same meaning as described above)
Is contacted with water to generate hydrogen to form an alkali metal metaborate or an alkali metal metaaluminate. The thus obtained product is dehydrated and dried by heating to form a crystal water 1 or less, preferably a crystal water. It can be set to 0 and used.

In the method of the present invention, the alkali metal salt of boric acid or aluminate is preferably used after dehydration to 1 or less water of crystallization. When the water of crystallization is two or more, the desired tetrahydroborate or tetrahydridoaluminate cannot be obtained in high yield. Among these materials, particularly borax _{(Na 2 B 4 O 7 ·} 10H 2 O) and Car Night _{(Na 2 B 4 O 7 ·} 4H 2 O) is readily available preferred. These are dried by heating and used as crystallization water 1 or less, preferably as an anhydride.

Next, as the metal hydride used together with the above-mentioned alkali metal salt of boric acid or aluminate, one acting as a reducing agent, for example, LiH, Na
Alkali metal hydrides such as H, KH, RbH, CsH, alkaline earth metal hydrides such as MgH ₂ , MgNiH ₄ , CaH ₂ , SrH ₂ or composite hydrides thereof, or hydrides of known hydrogen storage alloys Can be used. Among them, MgH ₂ and MgNiH ₄ are particularly preferable in terms of easy handling and low risk. These metal hydrides are pulverized and pulverized to an average particle size of 100 μm or less, preferably 100 nm or less, particularly 10 to 100 nm. In the method of the present invention, the metal hydride is used in a stoichiometric ratio or a slight excess with respect to the alkali metal salt of boric acid or aluminate. For example, KBO ₂
When reacting with MgH ₂ , the latter is used in an amount of 2 moles, preferably 2.5 to 3.0 moles per mole of the former.

In the method of the present invention, the above-mentioned alkali metal salt of boric acid or aluminate and a metal hydride are each pulverized into fine powders, mixed, and reacted at room temperature and atmospheric pressure while applying mechanical energy. The mechanical energy at this time is added as grinding energy, grinding energy, impact energy and the like. These mechanical energies are applied using a ball mill, tube mill, rod mill, attrition mill, vibration mill, impact mill, jet mill, micronizer, etc. It is advantageous to use a ball mill with a mixing function. The application of the mechanical energy may be determined in consideration of the production rate of the target tetrahydroborate or tetrahydridoaluminate depending on the application method, and usually, the grinding energy E is at least 4.0 J / g, preferably 10.0
It is preferable to perform the treatment so as to be J / g or more. This is because, for example, when a ball mill is used, the ball acceleration is 100 m / s ^2.
At least for 60 minutes.

In the method of the present invention, there is no particular need to apply pressure and heating, and the reaction proceeds smoothly at room temperature and atmospheric pressure. However, if desired, the reaction can be promoted by heating. In addition, since it can be performed in air as an atmosphere, there is no need to particularly consider it. However, if desired, an atmosphere of nitrogen, hydrogen, or the like can be used.

The reaction in the method of the present invention, for example, when potassium metaborate and magnesium hydride are used, proceed according to the following reaction formula to produce potassium tetrahydroborate and magnesium oxide. KBO ₂ + 2MgH ₂ → KBH ₄ + 2MgO At this time, if KBO ₂ · 2H ₂ O is used, as shown below, KBO ₂ · 2H ₂ O + 2MgH ₂ → KBO ₂ + 2Mg
(OH) ₂ + 2H ₂ MgH ₂ reacts with the water of crystallization of potassium metaborate and is consumed without generating KBH ₄ . The time required for the reaction in the method of the present invention varies depending on the raw materials used, the method of applying mechanical energy and the conditions, but is usually 20 to 120.
Range of minutes.

[0016]

Next, the present invention will be described in more detail by way of examples.

REFERENCE EXAMPLE A 500-ml planetary ball mill pulverizer (Model P-5, manufactured by Fritsch Co., Ltd.) was mixed with potassium metaborate fine particles having water of crystallization of 0, 0.5, 1, 1.5 and 2. 0.3 g of powder (average particle size: 75 nm) and 0.2 g of magnesium hydride fine powder (average particle size: 100 nm) (molar ratio 1:
2) and reacted at room temperature (20 ° C.) and atmospheric pressure under conditions of a ball acceleration of 86.5 m / s ² for 60 minutes. Next, the reaction product was extracted with anhydrous ethylenediamine, and the concentration of BH ₄ ⁻ was measured to determine the amount of KBH ₄ produced. Table 1 shows the results.

[0018]

[Table 1]

As is clear from this table, KBH ₄ is not produced when the water of crystallization of potassium metaborate exceeds one molecule.

Example 1 Using the same reactor as in the Reference Example, under the same reaction conditions, anhydrous potassium metaborate fine powder (average particle diameter: 75 nm) and magnesium hydride fine powder (average particle diameter: 100 nm) were reacted at a reaction time of The reaction was changed. The concentration of BH ₄ ⁻ in the reaction product thus obtained was measured to determine the KBH ₄ production rate (%), and the results are shown by black circles in FIG.

Example 2 The anhydrous fine powder of potassium metaborate in Example 1 was used.
Example 1 was repeated except that 0.6 g of fine powder (average particle size: 75 nm) of anhydrous borax (Na ₂ B ₄ O ₇ ) was used instead of 3 g, and the amount of magnesium hydride was changed to 0.72 g. The reaction was carried out under the same conditions to determine the KBH ₄ generation rate (%), and the results are shown by black triangles in FIG.

Example 3 Anhydrous sodium metaborate fine powder (average particle size of 75) was used in place of the anhydrous potassium metaborate fine powder in Example 1.
nm), the same experiment was performed using 0.2 g.
NaBH ₄ was obtained with a BO ₂ conversion of 47%.

Example 4 Using the same reactor as in Example 1, without changing the reaction conditions other than the motor rotation speed, anhydrous potassium metaborate fine powder (average particle size 75 nm) and magnesium hydride fine powder (average particle size) (Diameter 100 nm) were reacted for 1 hour, respectively, by changing the ball acceleration according to the motor rotation speed. The production rate of KBH ₄ thus obtained is shown by a black circle in FIG. In addition, an experiment was conducted in the same manner as in Example 2 except that the ball acceleration was changed, and the results are shown by black triangles in FIG. As can be seen from these figures, in all cases, the generation rate of KBH ₄ increases at a ball acceleration of 100 m / s ² or more.

Example 5 The experiment was repeated under the same conditions as in Example 1 except that the number of moles of magnesium hydride used per mole of anhydrous potassium metaborate was changed from 0 to 3 moles and the reaction was carried out for 1 hour. FIG. 3 shows the KBH ₄ generation rate thus obtained. As can be seen from this figure, the number of moles of magnesium hydride used per mole of potassium metaborate is 2
Above the moles, the production rate of KBH ₄ increases sharply,
It reaches almost 100% at 2.5 mol.

[0025]

According to the present invention, a metal complex hydride such as tetrahydroborate or tetrahydride aluminate can be obtained from an easily available raw material by a very simple operation and at a high conversion. .

[Brief description of the drawings]

FIG. 1 is a graph showing the relationship between the reaction time of KBO ₂ and MgH ₂ and the rate of KBH ₄ generation.

FIG. 2 shows ball acceleration and KBH ₄ when KBO ₂ or Na ₂ B ₄ O ₇ is reacted with MgH ₂ using a ball mill.
4 is a graph showing a relationship between generation rates.

FIG. 3 shows the number of moles of MgH ₂ per mole of KBO ₂ and KB.
7 is a graph showing a relationship between H ₄ generation rates.

Claims (6)

[Claims] 1. A general formula M ₁ [M ₂ H _4, wherein an alkali metal salt of boric acid or aluminate is brought into contact with a metal hydride in the form of fine powder and reacted while applying mechanical energy. (Wherein M ₁ is an alkali metal and M ₂ is boron or aluminum). A method for producing a tetrahydroborate or a tetrahydride aluminate represented by the formula: 2. The method according to claim 1, wherein the alkali metal salt of boric acid is an alkali metal salt of metaborate or an alkali metal salt of tetraborate. 3. The production method according to claim 2, wherein the alkali metal metaborate is not more than 1 water of crystallization or anhydrous. 4. The production method according to claim 1, wherein an alkaline earth metal hydride is used as the metal hydride. 5. The method according to claim 1, wherein mechanical energy is applied by ball milling. 6. The grinding energy E is at least 4.0 J
6. The method according to claim 5, wherein mechanical energy is applied so as to be / g.