Manganese phases

E. A. Brandes and R. E. Flint, Manganese Phase Diagrams, The Manganese Centre, Paris, 1980 L. B. Pankratz, Thermodynamic Properties of Elements and Oxides, Bull. 672, U.S. Bureau of Mines, Washington, D.C., 1982. 

Mill-). Barnes (1967) examined the depth dependence of the mineralogy in nodules taken Iron) the Pacific. His data indicate that above 3.500 ni in depth, the only important manganese phase is <5 MnO , but. below the 3.51 Hi m depth, both 10-A manganitc and 7-A manganitc coexist with the /i MnO-. The observed phase changes may be pressure induced. 

A portion of the isothermal section of an aluminum-iron-manganese phase diagram at 600 °C is shown in Figure 6.10. Assuming equilibrium, list the phases present, give their compositions, and calculate the relative amounts of them for... 

Cobalt is mostly incorporated into the iron phase of manganese nodules. However, theoretically, it would suit much better in the manganese phase which has experimentally been confirmed by Giovanoli and Brutsch There is a theory, not yet proved by experiments, staling that Co is oxidized to Co in sea-water. This process should be catalyzed by Fe(OH)3, The final product of oxidation, Co(OH)3, forms a solid solution with Fe(OH)3 The theory does not include a discussion about the possibilities of diadochic incorporation of cobalt after cristalliza-tion of iron hydroxide. 

Comparatively speaking, the main phase of Mn02 (in lithiophorite) disappeared, whereas the new manganese phase, which was MnO, existed in the reduced ores. As for Fe203, most of them were reduced to Fe304. Maybe, they should be separated from manganese by the pretreatment process of magnetie separation. It would be discussed in our future researches. 

The solubility of the mixed manganese phase (hausmannite MnjO (s)) can be described by the following reaction ... 

Manufactured by the liquid-phase oxidation of ethanal at 60 C by oxygen or air under pressure in the presence of manganese(ii) ethanoate, the latter preventing the formation of perelhanoic acid. Another important route is the liquid-phase oxidation of butane by air at 50 atm. and 150-250 C in the presence of a metal ethanoate. Some ethanoic acid is produced by the catalytic oxidation of ethanol. Fermentation processes are used only for the production of vinegar. 

Oxidation. Acetaldehyde is readily oxidised with oxygen or air to acetic acid, acetic anhydride, and peracetic acid (see Acetic acid and derivatives). The principal product depends on the reaction conditions. Acetic acid [64-19-7] may be produced commercially by the Hquid-phase oxidation of acetaldehyde at 65°C using cobalt or manganese acetate dissolved in acetic acid as a catalyst (34). Liquid-phase oxidation in the presence of mixed acetates of copper and cobalt yields acetic anhydride [108-24-7] (35). Peroxyacetic acid or a perester is beheved to be the precursor in both syntheses. There are two commercial processes for the production of peracetic acid [79-21 -0]. Low temperature oxidation of acetaldehyde in the presence of metal salts, ultraviolet irradiation, or osone yields acetaldehyde monoperacetate, which can be decomposed to peracetic acid and acetaldehyde (36). Peracetic acid can also be formed directiy by Hquid-phase oxidation at 5—50°C with a cobalt salt catalyst (37) (see Peroxides and peroxy compounds). Nitric acid oxidation of acetaldehyde yields glyoxal [107-22-2] (38,39). Oxidations of /)-xylene to terephthaHc acid [100-21-0] and of ethanol to acetic acid are activated by acetaldehyde (40,41). 

Butane-Naphtha Catalytic Liquid-Phase Oxidation. Direct Hquid-phase oxidation ofbutane and/or naphtha [8030-30-6] was once the most favored worldwide route to acetic acid because of the low cost of these hydrocarbons. Butane [106-97-8] in the presence of metallic ions, eg, cobalt, chromium, or manganese, undergoes simple air oxidation in acetic acid solvent (48). The peroxidic intermediates are decomposed by high temperature, by mechanical agitation, and by action of the metallic catalysts, to form acetic acid and a comparatively small suite of other compounds (49). Ethyl acetate and butanone are produced, and the process can be altered to provide larger quantities of these valuable materials. Ethanol is thought to be an important intermediate (50) acetone forms through a minor pathway from isobutane present in the hydrocarbon feed. Formic acid, propionic acid, and minor quantities of butyric acid are also formed. 

The Acetaldehyde Oxidation Process. Liquid-phase catalytic oxidation of acetaldehyde (qv) can be directed by appropriate catalysts, such as transition metal salts of cobalt or manganese, to produce anhydride (26). Either ethyl acetate or acetic acid may be used as reaction solvent. The reaction proceeds according to the sequence... 

Tables 1 and 2, respectively, Hst the properties of manganese and its aHotropic forms. The a- and P-forms are brittle. The ductile y-form is unstable and quickly reverses to the a-form unless it is kept at low temperature. This form when quenched shows tensile strength 500 MPa (72,500 psi), yield strength 250 MPa (34,800 psi), elongation 40%, hardness 35 Rockwell C (see Hardness). The y-phase may be stabilized usiag small amounts of copper and nickel. Additional compilations of properties and phase diagrams are given ia References 1 and 2.

Using high manganese slag practice. Furnace has three 1.9-m Smderberg electrodes. Assuming single-phase reactance = 1.0 m Q. 

In the sohd phase the most stable forms of Mn (ITT) are manganese sesquioxide [1317-34-6] M1I2O2, and its hydrate Mn202 and manganese... 

The crystal stmcture of ramsdeUite [12032-73-4] is similar to that of P Mn02 except that double chains of MnO octahedra are cross-Unked to adjacent double chains through the sharing of oxygen atoms located at the corners. RamsdeUite and pyrolusite are the only manganese dioxide phases where the composition approaches the stoichiometric Mn02 formula. Heating ramsdeUite to 250°C transforms it to pyrolusite. 

The thermal transitions of the manganese dioxides can be iUustrated by the beta phase which undergoes successive reductions and corresponding loss of oxygen as the temperature is increased (49). 

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