Process for separating zirconium and hafnium tetrachlorides from mixtures

Anhydrous solution comprising:

• an ionic liquid, the melting point of which is below 100° C., and
• a mixture of Zr tetrachloride/aromatic compound and Hf tetrachloride/aromatic compound complexes, in solution in said ionic liquid,
• said aromatic having in particular the following formula:
• in which Z1, Z2, Z3, Z4, Z5 and Z6 represent independently of each other:
• a hydrogen atom,
• an alkyl containing from 1 to 20, in particular from 1 to 12 carbon atoms, or
• an aryl,
• said ionic liquid being in particular a mixture, in particular stoichiometric, of one or more ammonium chlorides and one or more metal chlorides,
• the metal chloride or chlorides being in particular chosen from aluminium trichloride, zinc chloride, zirconium tetrachloride, hafnium tetrachloride, ferrous chloride, ferric chloride, boron trichloride, gallium trichloride, cupric chloride, cuprous chloride, titanium tetrachloride, cadmium trichloride, cobalt dichloride, tin dichloride, tin tetrachloride, antimony trichloride or mixtures thereof and
• the ammonium chloride or chlorides being in particular chosen from:
• the compounds corresponding to general formula NR1R2R3+Cl−, R1, R2, and R3 being linear or branched aliphatic groups with 1 to 20 carbon atoms
• the C5-C12 or aromatic cycloalkanes,
• the heterocyclic chlorides such as pyridine and the substituted pyridines,
• the dipyridyls,
• the mono-, di- or trisubstituted imidazolium chlorides,
• the benzymidazoliums and substituted benzymidazoliums,
• the triazoliums and substituted triazoliums,
• the piperadiziniums and substituted piperadiziniums,
• the pyrrolidiniums and substituted pyrrolidiniums,
• the oxazolidiniums and substituted oxazolidiniums,
• the morpholiniums and substituted morpholiniums,
• the guanidiniums and substituted guanidiniums,
• the thiazoliums and substituted thiazoliums,
• the phosphonium chlorides and substituted phosphonium chlorides,
• any other nitrogen- or phosphorus-containing heterocycle optionally also containing oxygen or sulphur atoms, and
• mixtures thereof.

Anhydrous reaction mixture comprising:

• an ionic liquid, the melting point of which is below 100° C.,
• a hydrocarbon or a mixture of hydrocarbons, and
• a mixture of Zr tetrachloride/aromatic compound and Hf tetrachloride/aromatic compound complexes,
• the Zr tetrachloride/aromatic compound complex:
• Zr(Ar)Cl2 (μ-Cl)3ZrCl3, (Ar representing an aromatic) being found in the hydrocarbon or the mixture of hydrocarbons, and the Hf tetrachloride/aromatic compound complex:
• [Hf(Ar)Cl3]+[Hf2Cl9] being found in the ionic liquid.
• said aromatic having in particular the following formula:
• in which Z1, Z2, Z3, Z4, Z5 and Z6 represent independently of each other:
• a hydrogen atom,
• an alkyl containing from 1 to 20, in particular from 1 to 12 carbon atoms, or
• an aryl,
• said ionic liquid being in particular a mixture, in particular stoichiometric, of one or more ammonium chlorides and one or more metal chlorides,
• the metal chloride or chlorides being in particular chosen from aluminium trichloride, zinc chloride, zirconium tetrachloride, hafnium tetrachloride, ferrous chloride, ferric chloride, boron trichloride, gallium trichloride, cupric chloride, cuprous chloride, titanium tetrachloride, cadmium trichloride, cobalt dichloride, tin dichloride, tin tetrachloride, antimony trichloride or mixtures thereof,
• the ammonium chloride or chlorides being in particular chosen from:
• the compounds corresponding to general formula NR1R2R3+Cl−, R1, R2, and R3 being linear or branched aliphatic groups with 1 to 20 carbon atoms,
• the cycloalkanes or aromatics, with 5 to 12 carbon atoms,
• the heterocyclic chlorides such as pyridine and the substituted pyridines, the dipyridyls,
• the mono-, di- or trisubstituted imidazolium chlorides,
• the benzymidazoliums and substituted benzymidazoliums,
• the triazoliums and substituted triazoliums,
• the piperadiziniums and substituted piperadiziniums,
• the pyrrolidiniums and substituted pyrrolidiniums,
• the oxazolidiniums and substituted oxazolidiniums,
• the morpholiniums and substituted morpholiniums,
• the guanidiniums and substituted guanidiniums,
• the thiazoliums and substituted thiazoliums,
• the phosphonium chlorides and substituted phosphonium chlorides
• any other nitrogen- or phosphorus-containing heterocycle optionally also containing oxygen or sulphur atoms, and
• mixtures thereof.
• said solvent being in particular a hydrocarbon or a mixture of hydrocarbons in particular chosen from:
• linear or branched alkanes, with 1 to 20 carbon atoms
• cycloalkanes with 5 to 12 carbon atoms and substituted cycloalkanes,
• aromatics substituted by alkyl and/or cycloalkyl chains, the alkyl groups having 1 to 20 carbon atoms
• mixtures thereof.

Method for separating hafnium tetrachloride and zirconium tetrachloride, comprising the following steps:

• bringing into contact under anhydrous conditions:
• a mixture of Zr tetrachloride/aromatic compound and Hf tetrachloride/aromatic compound complexes with an ionic liquid, the melting point of which is below 100° C.,
• the Zr tetrachloride/aromatic compound complex being molecular, and the Hf tetrachloride/aromatic compound complex being ionic
• recovery of the Zr tetrachloride/aromatic compound complex in a solvent, said solvent being such that:
• either it contains the abovementioned mixture of complexes,
• or it is added to the mixture of complexes at the same time as the ionic liquid is brought into contact with the abovementioned mixture of complexes, or it is added to the mixture of complexes after the ionic liquid is brought into contact with the abovementioned mixture of complexes.