Thermodynamics Research Center / ThermoML | Journal of Chemical and Engineering Data

ABSTRACT

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 soluble in the methanol-rich ternary liquid. The MgCl2-NH3-CH3OH system could potentially be used to produce magnesium chloride hexammoniate as feedstock for anhydrous magnesium chloride production, providing the ammonia concentration remains high enough to suppress formation of the ternary compound.