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AssigneeCompagnie Europeenne du Zirconium Cezus
InventorsLaurence Delons, Gerard Picard, Delphine Tigreat
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The invention relates to a method of separating zirconium and hafnium tetrachlorides using a solvent comprising firstly an alkaline metallic solvent comprising a salt made up of an alkali metal chloride and an acidic metal chloride A, for example a chloroaluminate or an alkaline chloroferrate, and secondly an acidic metal or metalloid chloride B of acidity that is less than that of the acidic metal chloride A. The acidic metal or metalloid chloride B is preferably selected from chlorides of Mg, Zn, and Cu. The method may be a continuous separation method by selective absorption of the tetrachloride vapors by the solvent in the substantially or totally molten state.
1/ A method of continuously separating tetrachlorides of zirconium and hafnium by selective absorption of their vapors by means of a solvent that is substantially or totally molten and flowing as a countercurrent to said vapors in a distillation column, the method being characterized in that the molten solvent comprises firstly an alkaline metallic solvent comprising a salt made up of an alkali metal chloride and an acidic metal chloride A, and secondly an acidic metal or metalloid chloride B of acidity that is lower than that of the acidic metal chloride A.
2/ A method according to claim 1, characterized in that the molten solvent comprises an alkaline chloroaluminate or chloroferrate or a mixture thereof, and an acidic metal or metalloid chloride B.
3/ A method according to claim 1 or claim 2, characterized in that the acidic metal or metalloid chloride B comprises a chloride of an alkaline earth and/or of a transition metal and/or of a metalloid.
4/ A method according to claim 3, characterized in that the acidic metal or metalloid chloride B has a degree of oxidation equal to 2 and preferably a coordination number of 4.
5/ A method according to claim 3 or claim 4, characterized in that the metal is selected from the group consisting in Mg, Zn, Cu, Ni, Co, Fe, Pb, Sn, preferably Mg, Zn, Cu.
6/ A method according to claim 3, characterized in that the acidic metal or metalloid chloride B is a magnesium chloride and/or a zinc chloride.
7/ A method according to any one of claims 1 to 6, characterized in that the alkali metal chloride in the alkaline solvent comprises Li, Na, K, or Cs as its metal, and preferably K or Na.
8/ A method according to any one of claims 1 to 6, characterized in that the acidic metal chloride A in the alkaline solvent comprises AlCl3 and/or FeCl3.
9/ A method according to any one of claims 1 to 6, characterized in that the alkaline solvent comprises AlCl3+KCl and/or FeCl3+NaCl.
10/ A method according to any one of claims 1 to 9, characterized in that, in the alkaline solvent, the molar ratio of acidic metal chloride A over alkali metal chloride lies in the range 0.7 to 1.3, and preferably in the range 0.8 to 1.
11/ A method according to any one of claims 1 to 10, characterized in that the molar ratio of acidic metal or metalloid chloride B over acidic metal chloride A lies in the range 0.01 to 1.5, and preferably in the range 0.1 to 0.3.
12/ A method according to any one of claims 1 to 11, characterized in that the method is conducted at a temperature lying in the range about 250° C. to about 550° C., and preferably in the range about 250° C. to about 350° C.
13/ The use of a solvent as described in any one of claims 1 to 11, for separating zirconium and hafnium tetrachlorides.
14/ A use according to claim 13, characterized in that the solvent is used partially, substantially, or totally molten.