JP2006248857A - Process for producing β-MnOOH - Google Patents

Abstract

The present invention provides a method for stably and industrially advantageously producing γ-MnOOH and a pure crystal phase β-MnOOH containing no crystal phase such as manganese trioxide.
After hydrolyzing metal manganese, the hydrolyzate is oxidized with an oxidizing agent at room temperature to produce β-MnOOH. A metal having particularly high crystallinity can be obtained by adding alkali after hydrolyzing metal manganese and further oxidizing with an oxidizing agent. As the oxidizing agent, it is preferable to use at least one selected from the group consisting of hypochlorous acid, chloric acid, perchloric acid and salts thereof, peroxodisulfate and permanganate.
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Description

  The present invention proposes a method by which β-MnOOH, which is a kind of manganese hydroxide, can be stably and industrially advantageously produced by a liquid phase method in a pure crystalline phase.

  Manganese hydroxide, so-called manganese oxyhydroxide (MnOOH), is mainly used as a raw material for soft fate, but in recent years it has also been applied as a synthetic raw material for primary and secondary batteries.

  As MnOOH, γ-MnOOH and β-MnOOH are typical.

  Various methods for producing γ-MnOOH by a liquid phase method have been proposed, and it is known that the particle shape is usually needle-like or strip-like. As a production method, for example, a method is disclosed in which ammonia water and hydrogen peroxide solution are added in small amounts simultaneously to an aqueous manganese sulfate solution (see Patent Document 1). In addition, a method has been reported in which hydrogen peroxide is added to an aqueous manganese sulfate solution, ammonia water is added with vigorous stirring, and the mixture is boiled (see Non-Patent Document 2). Furthermore, although there is no description of the crystal system, as a method for producing MnOOH having a needle-like particle shape, an aqueous manganese sulfate solution is added while blowing an oxygen gas or an oxygen-containing gas into an aqueous ammonia solution set at 40 to 80 ° C. A manufacturing method is disclosed (see Patent Document 3).

  On the other hand, because β-MnOOH is difficult to synthesize stably, there are relatively few proposals for production methods. A method of simultaneously adding 20% equivalent or more hydrogen peroxide solution is disclosed (see Patent Document 4).

As described above, as a method for producing MnOOH by the liquid phase method, a soluble manganese salt aqueous solution is neutralized with an alkaline aqueous solution at the same time as oxidation, or is neutralized and then produced by a method of oxidation. Hydrogen peroxide water or oxygen gas has been mainly used. However, these methods have a problem that trimanganese tetroxide (Mn ₃ O ₄ ) and γ-MnOOH are easily generated as a priority or by-product. In particular, when the manganese concentration is high, it has been difficult to stably produce β-MnOOH having a pure crystal phase.

JP 50-80297 A (Claim 1) Chemical Dictionary Dictionary "Chemical Dictionary 2" Kyoritsu Shuppan, published March 15, 1984, page 66 JP-A-5-208825 (Claim 1) JP 50-67817 A (page 7)

  The present invention proposes a method by which β-MnOOH having a pure crystal phase can be stably and industrially advantageously produced by a liquid phase method.

  As a result of diligent studies to achieve the above-mentioned problems, the present inventor first performed hydrolysis using metal manganese, and purified the hydrolysis product at room temperature using a specific oxidizing agent. It is found that β-MnOOH having a simple crystalline phase can be produced, and that β-MnOOH having particularly high crystallinity can be produced by adding an alkali before adding an oxidant to the hydrolysis, thereby completing the present invention. Has been reached.

  The present invention is described in further detail below.

  In the present invention, after hydrolyzing metal manganese, β-MnOOH is produced by oxidizing the hydrolysis reaction product with an oxidizing agent at room temperature.

  The shape of the metal manganese used in the present invention is not particularly limited, and any of a plate shape, a block shape, and a powder shape can be applied. Of these, fine particles are preferable from the viewpoint of the reaction rate of hydrolysis, and particularly preferably 100 mesh (0.15 mm) or less.

  The hydrolysis reaction of metal manganese can be performed by bringing metal manganese into contact with water. As water to be used, it is preferable to use pure water, ultrapure water, ion-exchanged water or distilled water having a low impurity content. Moreover, after adding an alkali to these water, a hydrolysis reaction can also be performed.

Although the hydrolysis reaction of metal manganese can be performed at room temperature, it is preferably heated to 80 ° C. or higher, preferably 95 ° C. or higher in order to accelerate the hydrolysis reaction. In addition, hydrogen gas is generated due to the progress of the hydrolysis reaction of manganese metal and a reducing atmosphere is formed, so that the hydrolysis product Mn (OH) ₂ exists stably, but nitrogen gas is introduced for further stabilization. Also good.

In the present invention, it is particularly preferable to use metal manganese having a low impurity content. Although any manufacturing method can be applied to the metal manganese, it is preferable to use electrolytic metal manganese that does not contain a counter ion of the manganese compound and other impurity elements. In particular, when the manganese content is 99.9% or more, the counter ion concentration in Mn (OH) ₂ produced by hydrolysis can be controlled to be extremely low, and other impurities and crystal phases other than β-MnOOH can be produced. Is particularly preferred because it can be significantly reduced.

  In the present invention, β-MnOOH having a high purity can be synthesized by oxidizing the hydrolysis product at room temperature using a specific oxidizing agent.

  The normal temperature in the present invention refers to a temperature of 40 ° C. or lower, and is not particularly limited in this temperature range, but is 0 to 35 ° C. from the viewpoint of workability with respect to a temperature drop from the hydrolysis reaction. A range is preferable and 15-30 degreeC is especially preferable. When the temperature exceeds 40 ° C., other crystal phases such as γ-MnOOH may be by-produced.

  In the present invention, β-MnOOH can be synthesized by oxidation after hydrolysis, but β-MnOOH having particularly high crystallinity can be obtained by adding an alkali before oxidizing the hydrolyzate with an oxidizing agent. Is obtained.

  The alkali source added at the time of hydrolysis is not particularly limited as long as it is water-soluble, and examples thereof include sodium hydroxide, potassium hydroxide, sodium carbonate, ammonium carbonate, and aqueous ammonia. Among these, it is preferable to use ammonia water that can be used as a liquid in terms of handling.

  The oxidizing agent used in the present invention is preferably at least one selected from the group consisting of hypochlorous acid, chloric acid, perchloric acid and their salts, peroxodisulfate and permanganate. Here, the salt is preferably a water-soluble salt, and examples thereof include a sodium salt, a potassium salt, and an ammonium salt.

  Pure β-MnOOH can be produced stably by oxidizing the hydrolysis product of manganese metal at room temperature using a specific oxidizing agent. Further, β-MnOOH having particularly high crystallinity can be produced by adding an alkali to the hydrolysis product and then oxidizing with an oxidizing agent.

  EXAMPLES Hereinafter, although an Example demonstrates this invention, this invention is not restrict | limited to these Examples at all.

Example 1
200 ml of ion-exchanged distilled water was placed in a 1,000 ml separable flask and kept at 95 ° C. in a thermostatic bath. 0.2 mol of electrolytic metal manganese powder having a manganese purity of 99.9% and an average particle size of 100 μm was added thereto, and stirring was performed. Then, stirring was stopped and a hydrolysis reaction was performed for 24 hours. Then, the reactor was taken out from the thermostat and cooled with ice water. The slurry temperature at this time was about 15 ° C.

  To this slurry, 200 ml of a 1 mol / l sodium hypochlorite aqueous solution was added dropwise with stirring at a rate of 20 ml per minute to advance the oxidation reaction, followed by filtration, washing with water and drying.

  The X-ray diffraction result of the obtained brownish brown powder is shown in FIG. The diffraction pattern attributed to β-MnOOH of JCPDS card 18-0804 was shown. Moreover, as a result of measuring the oxidation degree (MnOx) of manganese of this powder, it was X = 1.56.

Example 2
The treatment was performed under the same conditions as in Example 1 except that sodium oxodisulfate was used as the oxidizing agent and 100 ml of a 1 mol / l aqueous solution was applied.

  The powder had a brownish brown color, and the X-ray diffraction pattern showed the same characteristics as in Example 1.

Example 3
The treatment was performed under the same conditions as in Example 1 except that potassium manganate was used as the oxidizing agent of Example 1 and 100 ml of a 1 mol / l aqueous solution was used. As a result, the X-ray diffraction of the powder showed the same characteristics as in Example 1.

Example 4
400 ml of ion-exchanged distilled water was put into the separable flask of Example 1, and kept at 95 ° C. in a thermostatic bath. 1.5 mol of electrolytic metal manganese powder having a manganese purity of 99.9% and an average particle size of 100 μm was added thereto and stirred. Then, the stirring was stopped and a hydrolysis reaction was performed for 24 hours. The reactor was taken out of the thermostatic bath, cooled with water, and the temperature was lowered to about 30 ° C., and then 2 mol / l sodium peroxodisulfate and 350 ml were added dropwise with stirring at a rate of 20 ml / min to oxidize. The reaction was allowed to proceed, after which it was filtered, washed with water and dried.

  When the X-ray diffraction evaluation of the powder after drying was performed, the same pattern characteristics with a somewhat higher peak intensity than Example 1 were shown.

Example 5
Synthesis was performed under the same conditions as in Example 1 except that 0.1 mol of ammonia water in terms of NH ₃ concentration was added to distilled water, followed by hydrolysis.

  The X-ray diffraction result of the obtained powder is shown in FIG. 1, and Example 1 showed an equivalent peak intensity.

Example 6
After completion of the hydrolysis in Example 1, 200 ml of 1 mol / l ammonia water in terms of NH ₃ concentration was added with stirring, and then allowed to stand for 1 hour, 20 ml of 1 mol / l sodium hypochlorite aqueous solution, 200 ml. Oxidized by dropping at a rate of / min.

  The X-ray diffraction result of the obtained powder is shown in FIG. The peak intensity was higher than in Examples 1 and 4, and the crystallinity was improved.

Comparative Example 1
Using the separable flask of Example 1, 0.2 mol / l concentration manganese sulfate aqueous solution, 200 ml of NH ₃ concentration conversion 0.3 mol / l concentration aqueous ammonia solution, 200 ml was added at a rate of 20 ml / min. Neutralized. Next, 200 ml of a 1 mol / l sodium hypochlorite aqueous solution was added to this slurry at a rate of 20 ml / min, and oxidation was performed at room temperature, followed by filtration, washing with water and drying.
A brownish brown powder was obtained, but as a result of X-ray diffraction, it showed a pattern mainly composed of trimanganese tetroxide.

Comparative Example 2
The synthesis was performed using the oxidizing agent of Comparative Example 1 as a hydrogen peroxide solution. The product was trimanganese tetroxide.

Comparative Example 3
The synthesis was performed under the same conditions as in Example 1 except that the oxidizing agent was hydrogen peroxide. As a result of X-ray diffraction, the product was trimanganese tetraoxide.

Comparative Example 4
The oxidation of Example 1 was performed at a temperature of 50 ° C. Although the obtained powder showed a dark brown color, a peak attributed to γ-MnOOH appeared from X-ray diffraction.

X-ray diffraction pattern showing powder characteristics of examples

Claims (3)

A method for producing β-MnOOH, in which after hydrolyzing metal manganese, the hydrolyzate is oxidized with an oxidizing agent at room temperature. The manufacturing method of (beta) -MnOOH of Claim 1 which adds an alkali after hydrolyzing metal manganese, and also oxidizes with an oxidizing agent. The production of β-MnOOH according to claim 1 or 2, wherein the oxidizing agent is at least one selected from the group consisting of hypochlorous acid, chloric acid, perchloric acid and salts thereof, peroxodisulfate and permanganate. Method.

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