Zirconium and hafnium tetrachloride separation by extractive distillation with molten zinc chloride calcium and/or magnesium chloride solvent

Claim 1

In an extractive distillation method for separating hafnim tetrachloride from zirconium tetrachloride of the type wherein a mixture of zirconium and hafnium tetrachlorides is introduced into an extractive distillation column, which distillation column has a reflux reboiler connected at the bottom and a reflux absorber connected at the top and wherein a molten salt solvent is circulated into the reflux absorber and through the column to provide a liquid phase, and wherein molten salt solvent containing zirconium tetrachloride is taken from the reboiler and run through a stripper to remove zirconium tetrachloride product from said molten salt solvent and the stripped molten salt solvent is returned to the reflux absorber and hafnium tetrachloride enriched vapor is taken as product from the reflux absorber, the improvement comprising: said molten salt solvent having a composition of at least 80 weight percent zinc chloride and at least 5 percent of a viscosity reducer, said viscosity reducer being chosen from the group consisting of magnesium chloride, and calcium chloride, and mixtures thereof.