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The ammoniated magnesium chloride hexammoniate compound (HEX) is the key precursor phase required for the production of anhydrous magnesium chloride by the Australian Magnesium (AM) process. It is produced by direct ammoniation of MgCl2-saturated ethylene glycol solutions at 323 K. To determine the conditions required to form HEX, the C2H4[OH]2-rich part of the MgCl2–NH3–C2H4[OH]2 system was investigated at 323 ± 0.5 K. Seven phase regions were determined. These were: NH3(g)+LiqT, HEX+LiqT+NH3(g), HEX+LiqT, HEX+T+LiqT, T+LiqT, MgCl2·3EG+T+LiqT, and LiqT. The symbol T represents a ternary compound of composition MgCl2·2NH3·2C2H4[OH]2, and LiqT represents a ternary liquid phase. To produce only hexammoniate in the AM process, bulk ammonia levels need to be maintained at levels of greater than about (11 to 13) % (w/w) NH3. At lower ammonia levels, the formation of T-phase is promoted, resulting in coprecipitation of HEX and T-phase.

This paper uses experimentally determined solid−liquid phase relation studies within the MgCl2−H2O−C2H4(OH)2 ternary system to identify the origin of scale which formed in the packing of the dehydration column of the Australian Magnesium (AM) process for producing anhydrous magnesium chloride. The scale formed during dehydration of a purified magnesium chloride (MgCl2) leach liquor plus recycled ethylene glycol (C2H4(OH)2) solution. Experiments at 333 K showed the following phase fields present: a liquid-only phase region (LiqT); three two-phase regions T + LiqT, MgCl2·6H2O + Liqα, and MgCl2·3[C2H4(OH)2] + Liqβ; plus two three-phase regions MgCl2·6H2O + T + Liqα and MgCl2·3[C2H4(OH)2] + T + Liqβ. The compositions Liqα and Liqβ represent liquid compositions that extend a small distance into the ternary from the invariant points A and B located along the respective MgCl2−H2O and MgCl2−C2H4(OH)2 binaries, while T represents a ternary phase of composition MgCl2·2H2O·2[C2H4(OH)2]. An additional four three-phas...

The ammoniated magnesium chloride compounds MgCl2·nNH3, where n is 2, 4, or 6, are potentially usable as materials for producing anhydrous magnesium chloride. The MgCl2−NH3−CH3OH system was investigated at 298 K to determine phase stability regions for hexammoniate (HEX), tetrammoniate (TET), and diammoniate (DI). Five phase regions were determined. These were: HEX+Liq, HEX+T+TLiq, T+TLiq, MgCl2·6CH3OH+T+TLiq, and a ternary liquid phase, TLiq. The phase represented by the symbol T is a previously unknown ternary compound of composition MgCl2·4NH3·2CH3OH, and Liq refers to the liquid phase with a composition along, or very close to, the NH3−CH3OH binary. An additional five phase regions were also predicted based on the existence of known crystalline phases. These were: HEX+Liq(17.45 %NH3/MeOH)+NH3, HEX+TET+T, TET+DI+T, DI+T+MgCl2, and MgCl2·6CH3OH+T+MgCl2. The ternary phase was unstable, breaking down to produce ammonium chloride, ammonia, and magnesium methoxide (Mg(CH3O)2). These were all partially solub...