Magnesium chloride, molten

Electrolytic plant producing magnesium and chlorine from molten magnesium chloride. 

Molten magnesium chloride can be formed by the direct carbochlofination of magnesium oxide obtained from the calciaation of magnesium carbonate ores or magnesium hydroxide [1309-42-8]. 

Molten anhydrous magnesium chloride is tapped from the bottom of the reactor. Iron, aluminum, and siUcon-based impurities are also converted to their chlorides, which volatili2e out of the reactor. Carbon monoxide is generated from coke, carbon dioxide, and oxygen. The magnesium chloride is sent to electrolytic cells. Russian diaphragmless cells purchased from the defunct American Magnesium Co. are used. 

Heated zirconium is readily chlorinated by ammonium chloride, molten stannous chloride, zinc chloride, and chlorinated hydrocarbons and the common chlorinating agents. It is slowly attacked by molten magnesium chloride in the absence of free magnesium, which is always present in the KroU process. 

Early experimental work in electrorefining at Los Alamos by Mullins et-all ) demonstrated that americium could be partitioned between molten plutonium and a molten NaCl-KCl salt containing Pu+3 ions, and Knighton et-al(8), working at ANL on molten salt separation processes for fuel reprocessing, demonstrated that americium could be extracted from Mg-Zn-Pu-Am alloys with immiscible molten magnesium chloride salts. Work... 

Present production processes use two stage counter-current extraction to remove americium from molten plutonium with magnesium chloride based salts. Both 35 mole % NaCl - 35 mole % KC1 - 3D mole % MgCl2 and 50 mole % NaCl-26 mole % CaCl2 - 24 mole % Mg Cl 2 are used for americium extraction. Figures 4 and 5 show the ternary phase diagrams for these salt systemsU0). 

FIGURE 12.12 A schematic representation of the electrolytic cell used in the Dow process for magnesium. The electrolyte is molten magnesium chloride. As the current generated by the external source passes through the cell, magnesium ions are reduced to magnesium metal at the cathode and chloride ions are oxidized to chlorine gas at the anode. 

Sf.lf-Tksi 12.15A Determine the mass (in grams) of magnesium metal that can be obtained from molten magnesium chloride, by using a current of 7.30 A for 2.11 h. What volume of chlorine gas at 25°C and 1.00 atm will be produced at the anode ... 

Metallic magnesium is produced by either chemical or electrolytic reduction of its compounds. In chemical reduction, first magnesium oxide is obtained from the decomposition of dolomite. Then ferrosilicon, an alloy of iron and silicon, is used to reduce the MgO at about 1200°C. At this temperature, the magnesium produced is immediately vaporized and carried away. The electrolytic method uses seawater as its principal raw material magnesium hydroxide is precipitated by adding slaked lime (Ca(OH)2, see Section 14.10), the precipitate is filtered off and treated with hydrochloric acid to produce magnesium chloride, and the dried molten salt is electrolyzed. 

Titanium metal is obtained by reduction of TiClq with molten magnesium metal at high temperature. The reaction gives solid titanium metal (mp = 1660 °C) and liquid magnesium chloride (mp = 714 °C) ... 

At many plants, fluxes are added to the metal to reduce hydrogen contamination, remove oxides, and eliminate undesirable trace elements. Solid fluxes such as hexachloroethane, aluminum chloride, and anhydrous magnesium chloride may be used, but it is more common to bubble gases such as chlorine, nitrogen, argon, helium, and mixtures of chlorine and inert gases through the molten metal. 

Calculate the mass of magnesium that can he plated onto the cathode hy the electrolysis of molten magnesium chloride, using a current of 3.65 A for 55.0 min. 

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. 

Magnesium exhibits single displacement reactions, thus replacing lower metals in electrochemical series from their salt solutions or melt. For example, magnesium will replace iron from molten iron(II) chloride forming magnesium chloride ... 

The Kroll process involves heating molten magnesium and zirconium tetrachloride vapor in a sealed furnace in the absence of air under a helium atmosphere. The reaction forms zirconium sponge and magnesium chloride ... 

Magnesium chloride and excess magnesium are removed by distillation at reduced pressure. Pure zirconium may be prepared by several methods that include iodide decomposition process, zone refining, and electron beam melting. Also, Zr metal may be electrorefined in a molten salt bath of potassium zirconium fluoride, K2ZrFe... 

Figure 12.18 shows the layout of an electrolytic cell used for the commercial production of magnesium metal from molten magnesium chloride (the Dow process). As in a galvanic cell, oxidation occurs at the anode and reduction occurs at the cathode, electrons travel through the external wire from anode to cathode, cations move through the electrolyte toward the cathode, and anions move toward the anode. But unlike the spontaneous current in a galvanic cell, a current must be supplied by an external electrical power source. This current drives electrons through the wire in a predetermined direction (Fig. 12.19). The result is...

Finally, the magnesium chloride is dried and the molten salt is added to an electrolytic cell. Magnesium is produced at the cathode and chlorine is produced at the anode ... 

Before starting this work, it was feared that considerable chlorine would be lost as calcium chloride by interaction of the calcium in the coal ash with the zinc chloride, but it appears that essentially no chlorine is lost in this manner. In both runs 3 and 11, the bed solids contain substantially no chlorine whereas they contained a large percentage of the calcium that was fed. Since calcium chloride is molten but nonvolatile at combustion temperature, it would be expected that any calcium chloride would be retained in the bed solids. Since none was, it is concluded that no calcium chloride was formed. It also appears that no magnesium chloride was formed. 

Magnesium metal is produced by the electrolysis of molten magnesium chloride using inert electrodes. 

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