Reduction of magnesium

Electrolytic Reduction. The largest manufacturers of magnesium use processes based on the electrolytic reduction of magnesium chloride... 

Thermal Reduction. Magnesium metal can also be formed by the thermal reduction of magnesium oxide with a reactive metal, such as siUcon [7440-21-3] which forms a stable oxide. 

Three basic processes exist for the thermal reduction of magnesium oxide the Pidgeon process, the Magnetherm process, and the BoKano process. 

Early reports for generating Mg involved reduction of magnesium chloride or bromide by potassium or sodium in refluxing THF or diglyme(16). The reductions required 4-6 h and necessitated handling potassium or sodium. 

Preparation. Magnesium is obtained by electrolysis of magnesium chloride melts or by metallothermic reduction of magnesium oxide. 

A new production technique fully cost competitive with current processes could be the reduction of magnesium oxide by carbon to produce magnesium metal as a vapour and carbon monoxide gas this technique, according to Brooks et al. (2006), will involve rapid quenching of the Mg vapour through a nozzle at supersonic velocity to avoid Mg reversion to magnesium oxide. 

The reduction of magnesium sulfate is thermodynamically feasible at reactor temperatures of 900°F and above, especially if H2S is the product. Figure 19 shows the standard AG for the reduction of magnesium sulfate with hydrogen or methane as a function of temperature to make either H2S or SO2 as the reduction product. (The calculations have all been made on the basis of 1 mole of SO2.) Also shown are the values for the reduction of SO2... 

Although many commercial processes have heen developed since the first electrolytic isolation of Mg metal hy Davy and Faraday, and Bussy, hy chemical reduction, the principles of the manufacturing processes have not changed. At present, the metal is most commonly manufactured by electrolytic reduction of molten magnesium chloride, in which chlorine is produced as a by-product. In chemical reduction processes, the metal is obtained by reduction of magnesium oxide, hydroxide, or chloride at elevated temperatures. 

In 1792 Anton Rupprecht prepared impure magnesium (contaminated with iron) by reduction of magnesium oxide with carbon and called the metal austrium in honor of Austria (68). 

Rieke magnesium by reduction of magnesium chloride with lithium naphthalene [7,8]. Lithium (224 mg, 3.3 mmol), anhydrous magnesium chloride (1.57 g, 16.5 mmol)1, naphthalene (436 mg, 3.4 mmol) and dry... 

Table 2 Reduction of Magnesium Chloride with Potassium in the Presence of Potassium Iodide...

The so-called Rieke magnesium [111], which is prepared by reduction of magnesium bromide with potassium, is highly reactive and allows preparation of Grignard reagents... 

Derivation (1) Electrolysis of fused magnesium chloride (Dow seawater process) (2) reduction of magnesium oxide with ferrosilicon (Pidgeon process). 

Vacuum reduction of oxides of the alkali and alkaline earth metals, has proved a very useful technique, of which the Pidgeon ferrosilicon process for reduction of magnesium (Bl) has been an outstanding example. Although this process is not currently competitive with electrolytic reduction, the cost differential is not so great that improved vacuum equipment and vacuum techniques could not swing the balance in favor of this process. 

The various processes used for the production of metallic magnesium are based on the reduction of magnesium oxide with ferrosilicon (FeSi). Calcined dolomite is used as the source of magnesium oxide and the reaction is carried out at 1200 to 1600 °C under reduced pressure (13 to 670 kPa). Gaseous magnesium distils from the other materials and is condensed at about 450 °C [32.15]. 

V. Sepelak, M. Menzel, K.D. Becker, F. Krumeich, Mechanochemical reduction of magnesium ferrite. J. Phys. Chem. 44, 1411-1415 (2001)... 

Cao] Cao, R., Li, G., Wu, X., Some Thermodynamic Properties in Process of Thermal Reduction of Magnesium with High Aluminium Alloy (in Chinese), Acta Metall. Sin., 21, A471-A476... 

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