An Efficient, Solvent-Free Process for Synthesizing Anhydrous MgCl2

A new efficient and solvent-free method for the synthesis of anhydrous MgCl2 from its hexahydrate is presented. Fluidized dehydration of MgCl2 center dot 6H(2)O feedstock at 200 degrees C in a porous bed reactor yields MgCl2 center dot nH(2)O (0 < n < 1), which has a similar diffraction pattern as activated MgCl2. The MgCl2 center dot nH(2)O is then ammoniated directly using liquefied NH3 in the absence of solvent to form MgCl2 center dot 6NH(3). Calcination of the hexammoniate complex at 300 degrees C then yields anhydrous MgCl2. Both dehydration and deammoniation were thoroughly studied using in situ as well as ex situ characterization techniques. Specifically, a detailed understanding of the dehydration process was monitored by in situ PXRD and in situ FTIR techniques where formation of salt with nH(2)O (n = 4, 2, 1, <1) was characterized. Given the reduction in thermal energy required to produce dehydrated feedstock with this method compared with current strategies, significant cost benefits are expected. Overall, the combined effect of activation, macroporosity, and coordinated water depletion allows the formation of hexammoniate without using solvent, thus minimizing waste formation.