Марганец(IV) оксид

Химические свойства

Manganese dioxide is a black crystalline solid or powder.

Физические свойства

Black tetragonal crystals; density 5.08 g/cm3; Moh’s hardness 6.3; decomposes at 535°C; insoluble in water.

Использование

As an oxidizing agent, source of metallic manganese, decolorizing glass, painting porcelain, as an analytical reagentManganese(IV) oxide is used as an oxidizing agent in organic synthesis such as oxidation of allylic/benzylic alcohols, as a textile dye, as a reducing agent, and as a component of dry cell batteries such as zinc-carbon battery and alkaline battery. It is also used in making pigments for glasses and ceramics, and drier for paints. Further it is used in the manufacture of manganese steel and several manganese derivatives including potassium permanganate, a powerful versatile oxidant. Catalytic hydration of nitriles to amides by flowing through manganese dioxide has been reported. Manganese dioxide supported on inorganic oxide can be used for oxidation of methylamine through CWAO (Catalytic Wet Air Oxidation). It has high potential as highly efficient and robust material for water oxidation reaction (WORs).

Подготовка

Pure manganese(IV) oxide (precipitate form) may be prepared by reducing permanganate ion with a manganous salt:
2KMnO4 + 3MnSO4 + 2H2O → 5MnO2 + K2SO4 + 2H2SO4
Manganese(IV) oxide can also be precipitated by oxidation of a manganese(II) salt using an oxidizing agent such as hypochlorite or peroxydisulphate:
Mn2+ + S2O82– + 2H2O → MnO2 + 2SO42– + 4H+
Manganese(IV) oxide may also be made by thermal decomposition of manganese(II) nitrate; or from roasting manganese(II) carbonate in air: Mn(NO3)2 → MnO2 + 2NO2
MnCO3 + ½ O2 → MnO2 + CO2
A highly active gamma-MnO2 can be produced by treating manganese(III) oxide with hot sulfuric acid:
Mn2O3 + H2SO4 → MnO2 + MnSO4 + H2O
Mn2O3 is derived from pyrolusite by heating the mineral at 600–800°C or reducing with powdered coal at 300°C.

Общее описание

Manganese(IV) oxide (MnO₂) is an eco-friendly chemical having a high theoretical specific capacitance.

Профиль реактивности

The stability of manganese dioxide is due primarily to its insolubility. It is, however, readily attacked by reducing agents in acid solution, for example oxidizing concentrated hydrochloric acid to chlorine. In hot concentrated alkali it dissolves to give a purple solution which contains an equimolar mixture of trivalent manganese, probably as (Mn(OH)6)3- and manganate(V), (MnO4)3-. Manganese dioxide is also one of the most active catalysts for the oxidation of carbon monoxide near room temperature.

Опасность

Oxidizing agent, may ignite organic materials.

Промышленное использование

Manganese dioxide (MnO₂) is soluble in water and HNO₃ and soluble in HCl. It occurs in nature as the blue-black mineral pyrolusite. In glass, manganese dioxide is used as a colorant and decolorizer.
The major use of manganese oxides is an ore of manganese for the manufacturing of steel; manganese serves to increase the hardness and decrease the brittleness of steel. Another important use of manganese oxides is as the cathode material of common zinc/carbon and alkaline batteries (such as flashlight batteries).

Профиль безопасности

Poison by intravenous and intratracheal routes. Moderately toxic by subcutaneous route. Experimental reproductive effects. A powerful oxidizer. Flammable by chemical reaction. It must not be heated or rubbed in contact with easily oxilzable matter. Violent thermite reaction when heated with aluminum. Potentially explosive reaction with hydrogen peroxide, peroxomonosulfuric acid, chlorates + heat, anilinium perchlorate. Ignition on contact with hydrogen sulfide. Violent reaction with oxidizers, potassium azide (when warmed), diboron tetrafluoride, Incandescent reaction with calcium hydride, chlorine trifluoride, rubidium acetylide (at 350℃). Vigorous reaction with hydroxylaminium chloride. Incompatible with H202, H2SO j, Naz02. Keep away from heat and flammable materials. See also MANGANESE COMPOUNDS.

Возможный контакт

Manganese dioxide is used as depolarizer for dry cell batteries, for production of manganese metal; as an oxidizing agent; laboratory reagent; and in making pyrotechnics and matches; in dry cell batteries.

Перевозки

UN1479 Oxidizing solid, n.o.s., Hazard Class: 5.1; Labels: 5.1-Oxidizer, Technical Name Required. UN3137 (powder) Oxidizing solid, flammable, Hazard Class: 5.1; Labels: 5.1-Oxidizer, 4.1 Flammable solid, Technical Name Required.

Несовместимости

A powerful oxidizer. Incompatible with strong acids; reducing agents; combustible materials (such as fuel and clothing; organic materials. Mixtures with calcium hydride is a heat- and friction-sensitive explosive. Vigorous reaction with hydrogen sulfide, diboron tetrafluoride; calcium hydride; chlorine trifluoride; hydrogen peroxide; hydroxyaluminum chloride; anilinium perchlorate. Decomposes when heated above 553C producing manganese(III)oxide and oxygen, which increases fire hazard. Reacts violently with aluminum (thermite reaction), potassium azide; rubidium acetylide; in the presence of hea

Утилизация отходов

Generators of waste (equal to or greater than 100 kg/mo) containing this contaminant, EPA hazardous waste number N450, must conform to USEPA regulations for storage, transportation, treatment, and disposal of waste. Dispose of waste material as hazardous waste using a licensed disposal contractor to an approved landfill. Dispose of contents and container to an approved waste disposal plant. Containers must be disposed of properly by following package label directions or by contacting your local or federal environmental control agency, or by contacting your regional EPA office. All federal, state, and local environmental regulations must be observed. Do not discharge into drains or sewers