JPH07247122A - Activated manganese dioxide and method for producing the same - Google Patents

Abstract

PURPOSE:To provide activated manganese dioxide capable of being suitably used as an adsorbing agent or an oxidizing agent for special gases, special heavy metals, etc., namely having a small particle size and a large specific surface area. CONSTITUTION:A method for producing the activated manganese dioxide comprises blowing oxygen gas, etc., on a manganese-containing raw material for evaporating off the manganese content contained in the particles to produce substantially spherical manganese dioxide consisting mainly of Mn3O4 and subsequently treating the managaness dioxide with an Mn3O4, and treating component and other impure components to leave Mn2+ in a skeleton-like state. The produced activated manganese dioxide has an uneven surface, many pores, an average particle size of 0.1-5mum and a specific surface area (BET value) of >=50 m<2>/g.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to activated manganese dioxide and a method for producing the same, and more particularly to active manganese dioxide having a large specific surface area and little deterioration over time and a method for producing the same.

The manganese dioxide according to the present invention is used for the following purposes by taking advantage of its large specific surface area. Adsorbent for air purification: Effective as an adsorbent for removing odors such as mercaptans and amines, and an adsorbent for harmful gases such as sulfur dioxide. Adsorbent for harmful metals ... Effective as an adsorbent for removing these metals from aqueous solutions of heavy metals such as Hg, Cr, Pb. Adsorbent for valuable metals: L contained in geothermal water, seawater, etc.
It is effective as an adsorbent for recovering valuable metals such as i and Au. Special gas oxidizer: Effective for oxidizing special gases such as trimethylamine. Others ... Effective for applications where manganese dioxide is used as raw materials for batteries, raw materials for ferrites, catalysts, etc.

[0003]

2. Description of the Related Art Conventionally, as a method for producing manganese dioxide (powder / granular), a method of electrolyzing a manganese sulfate solution, a method of heating manganese oxide in the presence of oxygen, a method of heating manganese nitrate, etc. are known. ing. However, in these conventional methods, the main purpose is simply to obtain manganese dioxide, and since it is manufactured through treatments such as mechanical pulverization and oxidative heating, it is difficult to pulverize it and the product particle size is limited.
It was also impossible to process the particle surface into a complicated shape. As a result, the specific surface area (BET value) is 30 ~
The reality is that only 40m ² / g can be obtained.

On the other hand, as a conventional technique for obtaining fine manganese oxide, Japanese Patent Application Laid-Open No. 63-210029 proposes a method of blowing oxygen into a ferromanganese melt.
However, manganese oxide produced under this method is mainly composed of trimanganese tetraoxide (Mn ₃ O ₄ ), not manganese dioxide (MnO ₂ ). Therefore, conventionally, trimanganese tetraoxide (M
n ₃ O ₄ ) has been studied by heating it in an oxidizing atmosphere to convert it to manganese dioxide.However, this method does not change the shape of the particle surface so much that the particle size is satisfactory. However, the specific surface area (BET value) is at most 1
It was found that only about 5 m ² / g could be obtained.

[0005]

After all, in the above-mentioned respective prior arts, it was not possible to produce manganese dioxide which is fine and has a large specific surface area having many projections on the surface of the particles. A main object of the present invention is to provide active manganese dioxide having a small so-called particle size and a large specific surface area, which is preferably used as an adsorbent or an oxidizing agent for special gases and heavy metals. Another object of the present invention is to establish a technique for easily and inexpensively producing the above active manganese dioxide.

[0006]

With respect to each of the above objects, the present invention provides (1) a surface having irregularities and a large number of pores, and an average particle diameter: 0.
We propose an activated manganese dioxide consisting of a substantially spherical porous body having a specific surface area (BET value) of 1 to 5 μm of 50 m ² / g or more, preferably 150 m ² / g or more. (2) The irregularities on the surface of the fine particles are not merely rough surfaces, but the irregular surface is formed by a series of many protrusions. (3) The fine particles are a porous body, and are manganese dioxide forming a network skeleton due to open pores communicating with each other. That is, the porosity of this porous body is 20-70.
%.

The above activated manganese dioxide can be produced by the following method. (4) Oxygen gas or oxygen acetylene gas, oxygen LP for lumps or particles of metal manganese or manganese alloy
By blowing an oxidizing gas which is a G gas, the manganese content in the lumps or particles is vaporized and dispersed to be rapidly cooled, thereby being made into particles, and thereby a substantially spherical manganese oxide containing Mn ₃ O ₄ as a main component is oxidized. To form a substance, dissolve and remove the Mn ²⁺ component and other impurity components by treating the manganese oxide with an acid, and leave the MnO ₂ in a skeleton-like structure to make it porous. ) For molten metal of manganese or manganese alloy,
By blowing oxygen gas or oxygen-enriched air or oxidizing gas that is a mixed gas of oxygen and carbon dioxide gas,
The manganese content in the particles is vaporized to form particles by quenching, thereby forming a substantially spherical manganese oxide containing the main component as the main component, and the manganese oxide is treated with an acid to obtain a Mn ²⁺ component and other components. Dissolve and remove impurity components,
It is produced by leaving MnO ₂ in a skeleton shape and making it porous. In carrying out these production methods, (6) it is preferable to use at least one acid selected from hydrochloric acid, sulfuric acid and nitric acid or a mixed acid thereof in the acid treatment. (7) The acid treatment may be carried out at room temperature and atmospheric pressure, or the acid treatment may be carried out at a high temperature, in this case, 50 ° C.
The above method is the preferred method.

[0008]

The first feature of the ozone decomposing catalyst of the present invention having the above-described structure is that it has a large specific surface area. That is, the specific surface area of the particulate manganese oxide mainly composed of Mn ₃ O ₄ is only about 1 m ² / g, whereas the catalyst of the present invention has a specific surface area of 50 m ² / g or more, preferably Is 150 m ² / g or more, which is an extremely large point. According to the research conducted by the present inventors, it is considered that this is caused by further acid treatment of the particulate trimanganese tetroxide oxide. In particular, when the temperature of the acid treatment is increased to 60 ° C. or higher, a catalyst having a specific surface area of 200 m ² / g or higher can be obtained very easily.

The second feature of the manganese dioxide for catalyst according to the present invention is that the manganese dioxide has a mesh-like shape due to the fact that it has an uneven surface with a large number of projections on its surface and the pores communicating with the inside and outside. The skeleton is formed into porous, substantially spherical fine particles. In addition, the main component is manganese dioxide having an average particle size of 0.1 to 5 μm and grown in a skeleton of relatively high purity, and other small amounts of Fe ₂ O ₃ , SiO ₂ , Al ₂ O ₃ , CaO, MgO, etc. It is composed of impurities.

The uneven surface of the catalyst fine particles is formed by forming a number of projections and depressions.
Further, the catalyst fine particles are substantially porous bodies in which manganese dioxide grows like a net to form a skeleton due to open pores which are formed by acid treatment and communicate with each other inside and outside. The porosity as particles is about 20 to 70%.

As described above, the reason why the surface of the porous manganese dioxide becomes uneven due to many protrusions is not clear, but the pores formed inside the Mn ²⁺
It is considered that this is probably because many protrusions on the surface were also melted out of Mn ²⁺ , which is probably the result of the melting of the Mn ²⁺ .

Next, the production of the activated manganese dioxide according to the present invention will be described. (1) First, by blowing oxygen gas or an oxidizing gas such as oxygen acetylene gas or oxygen LPG gas onto manganese alloy lumps or particles such as metal manganese or ferromanganese contained in a reaction vessel, the metal Manganese in manganese or a manganese alloy is vaporized and vaporized, and further cooled during vaporization to be finely divided into fine particles, and Mn ₃ O ₄
Is a spherical manganese oxide having an average particle diameter of 0.1 to 5 μm. When a molten metal of manganese metal or a manganese alloy (ferromanganese) is used, the molten metal is sprayed with an oxidizing gas such as oxygen or oxygen-enriched air or a mixed gas of oxygen and carbon dioxide. To evaporate and vaporize, and rapidly cool during the vaporization flight to recover fine-grained manganese oxide.

(2) Next, by adding at least one acid selected from hydrochloric acid, sulfuric acid, and nitric acid or a mixed acid thereof to the obtained fine-particle manganese oxide to maintain the particle size before the acid treatment. At the same time, Mn ²⁺ components (that is, MnO components in Mn ₃ O ₄ ) and impurity components that exist even inside the particles were dissolved and removed, and a mesh surface was formed with MnO ₂ as a skeleton. It is possible to obtain a porous high surface area catalyst, ie manganese dioxide.

In the production method of the present invention, as the starting material, as described above, in addition to metallic manganese, manganese alloy, for example, lumps or particles of ferromanganese, or a molten metal thereof is used. Among them, it is particularly effective to use manganese oxide or the like generated during decarburization / melting from high carbon ferromanganese to medium / low carbon ferromanganese in a converter.

Further, in the present invention, the above-mentioned starting material is treated as described below prior to the acid treatment to obtain fine particle manganese oxide. (B) A ferrous manganese melt is sprayed with oxygen or a gas containing oxygen, such as oxygen-enriched air, or an oxidizing gas composed of a mixed gas of oxygen and carbon dioxide, through a lance,
Particulate manganese oxide that was collected by evaporating the components and cooling. (B) Oxygen gas, oxygen acetylene gas, or oxygen LPG on metal manganese or ferromanganese lumps or particles.
Particulate manganese oxide collected as described above by blowing gas.

The reason why such a manganese oxide is used as an acid treatment material is that the fine-particle manganese oxide raw material obtained as described in (a) and (b) above has an average particle size of 0.1 to 5 μm.
Since it is a fine spherical particle of m, and its main component is trimanganese tetroxide, only about 2/3 of the Mn ²⁺ component is dissolved in the total Mn content when it is treated with the acid described later. And then Mn
^{This is because the 4+} component has a property of remaining as particles having innumerable protrusions. That is, this increases the specific surface area of manganese dioxide. Moreover, since it is a fine powder from the beginning, a pulverization step is unnecessary, and therefore a high-purity product can be manufactured without the risk of impurities being mixed in.

Next, in the production method of the present invention, the above-mentioned manganese oxide (Mn ₃ O ₄ ) is immersed in an acid such as sulfuric acid or hydrochloric acid heated at room temperature or higher (for example, 50 ° C. or higher). Then, it is acid-treated to dissolve / remove Mn ²⁺ components and impurity components and leave MnO ₂ in a net form to obtain a final product (activated manganese dioxide).

The activated manganese dioxide according to the present invention produced by the method as described above has been investigated and measured by the present inventors, and it was confirmed that the activated manganese dioxide depends on the properties of the starting material regardless of the production conditions. It has manganese dioxide as its main component, has an average particle size of 0.1 to 5 μm, has a large number of protrusions on the surface to form a rough surface, and the inside has open pores to form Mn.
It becomes an almost spherical porous material that retains O ₂ in a net-like shape, and its specific surface area (BET value) is 50 m ² / g or more, preferably 15
It becomes spherical fine particles of 0 m ² / g or more.

In the production method of the present invention, the acid treatment is carried out at a temperature above room temperature. The acid used in this treatment is 1 wt% or more, and any hydrochloric acid, sulfuric acid or nitric acid having a weight equal to or more than the molar amount of manganese oxide can be used. Even if one kind or a mixture of two or more kinds is used. Well, its concentration can be arbitrarily selected. The acid treatment is performed at room temperature and atmospheric pressure for about 2 hours, preferably at 50 ° C or higher for 4 hours.
It is preferable to carry out for more than an hour. Then, after this acid treatment, it may be filtered or further neutralized with an alkaline solution.

[0020]

【Example】

Example 1 Oxygen-enriched air was blown to the molten metal produced during the converter melting of low-carbon ferromanganese in a ladle to be pulverized, and 250 g of manganese oxide particles thus obtained was gradually added with 1250 g of 23% sulfuric acid. After heating at 60 ° C. for 4 hours with stirring, filtration was performed. To this insoluble matter after filtration, 1250 g of 23% sulfuric acid was added once again, the same operation was repeated, the insoluble matter was neutralized with an alkaline solution, filtered again, washed and dried at 120 ° C. . The chemical composition of the activated manganese dioxide powder thus obtained is shown in Table 1, the particle size distribution is shown in Table 2, and the specific gravity and the specific surface area (BET value) are shown in Table 3.
Shown in. In addition, electron microscope photographs (× 20000) of the raw material manganese oxide and the activated manganese dioxide obtained here are shown in FIGS. 1 and 2, respectively.

[0021]

[Table 1]

[0022]

[Table 2]

[0023]

[Table 3]

Example 2 250 g of manganese oxide particles obtained by blowing oxygen gas onto flaky metallic manganese contained in a container and 20% hydrochloric acid
Gradually add 1100cc under normal temperature and pressure, and stir at 70 ℃.
After heating for 2 hours, the mixture was filtered. To this insoluble matter after filtration, 1200 cc of 20% hydrochloric acid was added once again, the same operation was repeated, the insoluble matter was neutralized with an alkaline solution, filtered again, washed and dried at 120 ° C. . The chemical components, particle size distribution, and specific gravity and specific surface area (BET value) of the thus-obtained activated manganese dioxide powder are shown in Table 4, Table 5, and Table 6, respectively. In addition, electron micrograph of activated manganese dioxide obtained here (× 20000)
Are shown in FIG.

[0025]

[Table 4]

[0026]

[Table 5]

[0027]

[Table 6]

[0028]

As described above, the manganese dioxide obtained under the manufacturing method of the present invention has a large specific surface area because it has an uneven surface having innumerable projections on the surface of ultrafine particles. Therefore, air purification such as deodorization, detoxification treatment of wastewater containing heavy metals, recovery of valuable metals such as Li and Au from geothermal water or seawater, other fields where adsorbents are generally effective, and fields where manganese dioxide is generally effective It is preferably used for. Moreover, its manufacture is extremely easy.

[Brief description of drawings]

FIG. 1 is an electron micrograph showing the particle shape of the product manganese dioxide.

(72) Inventor Yukio Matsunami Yukio Matsunami Oguni-machi, Nishikitama-gun, Yamagata Oguni-machi, Oguni-machi, Tateno, Niie 2 232 Nippon Heavy Industries Co., Ltd. Oguni Plant

Claims (5)

[Claims] 1. An activated dioxide composed of a substantially spherical porous body having an uneven surface and pores, an average particle diameter of 0.1 to 5 μm, and a specific surface area (BET value) of 50 m ² / g or more. manganese. 2. A sphere or particles of metallic manganese or a manganese alloy are blown with an oxidizing gas such as oxygen gas, oxygen acetylene gas, or oxygen LPG gas to give a substantially spherical shape containing Mn ₃ O ₄ as a main component. Manganese oxide is formed, and this manganese oxide is acid-treated to dissolve and remove Mn ²⁺ components and other impurity components to form skeleton MnO ₂
A method for producing activated manganese dioxide, characterized in that 3. Mn ₃ O ₄ is contained as a main component by blowing oxygen gas, oxygen-enriched air, or an oxidizing gas, which is a mixed gas of oxygen and carbon dioxide, onto a molten metal of manganese or a manganese alloy. It forms almost spherical manganese oxide, and the manganese oxide is treated with acid to produce Mn ²⁺
Skeletal MnO ₂ by dissolving and removing components and other impurities
A method for producing activated manganese dioxide, characterized in that 4. In the acid treatment, at least one acid selected from hydrochloric acid, sulfuric acid and nitric acid or a mixed acid thereof is used.
The manufacturing method described in. 5. The manufacturing method according to claim 2, wherein the acid treatment is carried out at room temperature or at a temperature higher than room temperature.