Separation of rare earth metals

Abstract

A method for extracting a rare earth metal from a mixture of one or more rare earth metals, said method comprising contacting an acidic solution of the rare earth metal with a composition which comprises an ionic liquid to form an aqueous phase and a non-aqueous phase into which the rare earth metal has been selectively extracted.

1 - 68 . (canceled) 
     
     
         69 . An ionic liquid has the formula:
   [Cat + ][X − ]   in which:   [Cat + ] represents a cationic species having the structure:   
       
         
           
           
               
               
           
         
         where: [Y + ] comprises a group selected from ammonium, benzimidazolium, benzofuranium, benzothiophenium, benzotriazolium, borolium, cinnolinium, diazabicyclodecenium, diazabicyclononenium, 1,4-diazabicyclo[2.2.2]octanium, diazabicyclo-undecenium, dithiazolium, furanium, guanidinium, imidazolium, indazolium, indolinium, indolium, morpholinium, oxaborolium, oxaphospholium, oxazinium, oxazolium, iso-oxazolium, oxothiazolium, phospholium, phosphonium, phthalazinium, piperazinium, piperidinium, pyranium, pyrazinium, pyrazolium, pyridazinium, pyridinium, pyrimidinium, pyrrolidinium, pyrrolium, quinazolinium, quinolinium, iso-quinolinium, quinoxalinium, quinuclidinium, selenazolium, sulfonium, tetrazolium, thiadiazolium, iso-thiadiazolium, thiazinium, thiazolium, iso-thiazolium, thiophenium, thiuronium, triazinium, triazolium, iso-triazolium and uronium groups; 
         each EDG represents an electron donating group; and 
         L 1  represents a linking group selected from C 1-10  alkanediyl, C 2-10  alkenediyl, C 1-10  dialkanylether and C 1-10  dialkanylketone groups; 
         each L 2  represents a linking group independently selected from C 1-2  alkanediyl, C 2  alkenediyl, C 1-2  dialkanylether and C 1-2  dialkanylketone groups; and 
         [X − ] represents an anionic species. 
       
     
     
         70 . The ionic liquid of  claim 69 , wherein when the nitrogen linking L 1  to each L 2  and one of the EDG both coordinate to a metal, the ring formed by the nitrogen, L 2 , the EDG and the metal is a 5 or 6 membered ring. 
     
     
         71 . The ionic liquid of  claim 69 , wherein [Y + ] represents an acyclic cation selected from:
   [—N(R a )(R b )(R c )] + , [—P(R a )(R b )(R c )] +  and [—S(R a )(R b )] + ,
   wherein: R a , R b  and R c  are each independently selected from optionally substituted C 1-30  alkyl, C 3-8  cycloalkyl and C 6-10  aryl groups.   
     
     
         72 . The ionic liquid of  claim 69 , wherein [Y + ] represents a cyclic cation selected from: 
       
         
           
           
               
               
           
         
         wherein: R a , R b , R c , R d , R e  and R f  are each independently selected from: hydrogen and optionally substituted C 1-30  alkyl, C 3-8  cycloalkyl and C 6-10  aryl groups, or any two of R a , R b , R c , R d and R e  attached to adjacent carbon atoms form an optionally substituted methylene chain —(CH 2 ) q — where q is from 3 to 6. 
       
     
     
         73 . The ionic liquid of  claim 69 , wherein [Y + ] represents a saturated heterocyclic cation having the formula: 
       
         
           
           
               
               
           
         
         wherein: R a , R b , R c , R d , R e  and R f  are each independently selected from: hydrogen and optionally substituted C 1-30  alkyl, C 3-8  cycloalkyl and C 6-10  aryl groups, or any two of R a , R b , R c , R d  and R e  attached to adjacent carbon atoms form an optionally substituted methylene chain —(CH 2 ) q — where q is from 3 to 6. 
       
     
     
         74 . The ionic liquid of  claim 72  or  claim 73 , wherein at least one of R a , R b , R c , R d , R e  and R f  is a C 1-5  alkyl group substituted with —CO 2 R x , —OC(O)R x , —CS 2 R x , —SC(S)R x , —S(O)OR x , —OS(O)R x , —NR x (O)NR y R z , —NR x C(O)OR y , —OC(O)NR y R z , —NR x C(S)OR y , —OC(S)NR y R z , —NR x C(S)SR y , —SC(S)NR y R z , —NR x C(S)NR y R z , —C(O)NR y R z , —C(S)NR y R z , wherein R x , R y  and R z  are independently selected from hydrogen or C 1-6  alkyl. 
     
     
         75 . The ionic liquid of  claim 74 , wherein at least one of R a , R b , R c , R d , R e  and R f  represents a group selected from: 
       
         
           
           
               
               
           
         
         wherein R y =R z , and wherein R x , R y  and R z  are each selected from C 3-6  alkyl. 
       
     
     
         76 . The ionic liquid of  claim 72  or  claim 73 , wherein one of R a , R b , R c , R d , R e  and R f  is a substituted C 1-5  alkyl group, and the remainder of R a , R b , R c , R d , R e  and R f  are independently selected from H and unsubstituted C 1-5  alkyl groups. 
     
     
         77 . The ionic liquid of  claim 69 , wherein L 1  represents a linking group selected from C 1-10  alkanediyl and C 1-10  alkenediyl groups. 
     
     
         78 . The ionic liquid of  claim 69 , wherein each L 2  represents a linking group independently selected from C 1-2  alkanediyl and C 2  alkenediyl groups. 
     
     
         79 . The ionic liquid of  claim 69 , wherein each EDG represents an electron donating group independently selected from  13  CO 2 R x , —OC(O)R x , —CS 2 R x , —SC(S)R x , —S(O)OR x , —OS(O)R x , —NR x (O)NR y R z , —NR x C(O)OR y , —OC(O)NR y R z , —NR x C(S)OR y , —OC(S)NR y R z , —NR x C(S)SR y , —SC(S)NR y R z , —NR x C(S)NR y R z , —C(O)NR y R z , —C(S)NR y R z , wherein R x , R y  and R z  are independently selected from hydrogen or C 1-6  alkyl, such as wherein each EDG represents an electron donating group independently selected —CO 2 R x  and —C(O)NR y R z , wherein R x , R y  and R z  are each independently selected from C 3-6  alkyl. 
     
     
         80 . The ionic liquid of  claim 69 , wherein each -L 2 -EDG represents an electron donating group independently selected from: 
       
         
           
           
               
               
           
         
         wherein R y =R z , and wherein R x , R y  and R z  are each selected from C 3-6  alkyl. 
       
     
     
         81 . The ionic liquid of  claim 69 , wherein [X − ] represents one or more anionic species selected from: hydroxides, halides, perhalides, pseudohalides, sulphates, sulphites, sulfonates, sulfonimides, phosphates, phosphites, phosphonates, methides, borates, carboxylates, azolates, carbonates, carbamates, thiophosphates, thiocarboxylates, thiocarbamates, thiocarbonates, xanthates, thiosulfonates, thiosulfates, nitrate, nitrite, tetrafluoroborate, hexafluorophosphate and perchlorate, halometallates, amino acids, borates, polyfluoroalkoxyaluminates. 
     
     
         82 . The ionic liquid of  claim 81 , wherein [X − ] represents one or more anionic species selected from:
 a) a halide anion selected from: F − , Cl − , Br − , I − ;   b) a perhalide anion selected from: [I 3 ] − , [I 2 Br] − , [IBr 2 ] − , [Br 3 ] − , [Br 2 C] − , [BrCl 2 ] − , [ICl 2 ] − , [I 2 Cl] − , [Cl 3 ] − ;   c) a pseudohalide anion selected from: [N 3 ] − , [NCS] − , [NCSe] − , [NCO] − , [CN] − ;   d) a sulphate anion selected from: [HSO 4 ] − , [SO 4 ] 2− , [R 2 OSC 2 O] − ;   e) a sulphite anion selected from: [HSO 3 ] − , [SO 3 ] 2− , [R 2 OSO 2 ] − ;   f) a sulfonate anion selected from: [R 1 SC 2 O] − ;   g) a sulfonimide anion selected from: [(R 1 SO 2 ) 2 N] − ;   h) a phosphate anion selected from: [H 2 PO 4 ] − , [HPO 4 ] 2− , [PO 4 ] 3− , [R 2 OPO 3 ] 2− , [(R 2 O) 2 PO 2 ] − ;   i) a phosphite anion selected from: [H 2 PO 3 ] − , [HPO 3 ] 2− , [R 2 OPO 2 ] 2− , [(R 2 O) 2 PO] − ;   j) a phosphonate anion selected from: [R 1 PO 3 ] 2− , [R 1 P(O)(OR 2 )O] − ;   k) a methide anion selected from: [(R 1 SO 2 ) 3 C] − ;   l) a borate anion selected from: [bisoxalatoborate], [bismalonatoborate] tetrakis[3,5-bis(trifluoromethyl)phenyl]borate, tetrakis(pentafluorophenyl)borate;   m) a carboxylate anion selected from: [R 2 CO 2 ] − ;   n) an azolate anion selected from: [3,5-dinitro-1,2,4-triazolate], [4-nitro-1,2,3-triazolate], [2,4-dinitroimidazolate], [4,5-dinitroimidazolate], [4,5-dicyanoimidazolate], [4-nitroimidazolate], [tetrazolate];   o) a sulfur-containing anion selected from: thiocarbonates (e.g. [R 2 OCS 2 ], thiocarbamates (e.g. [R 2   2 NCS 2 ] − ), thiocarboxylates (e.g. [R 1 CS 2 ]), thiophosphates (e.g. [(R 2 O) 2 PS 2 ] − ), thiosulfonates (e.g. [RS(O) 2 S]) , thiosulfates (e.g. [ROS(O) 2 S]) − );   p) a nitrate ([NO 3 ] − ) or nitrite ([NO 2 ] − ) anion;   q) a tetrafluoroborate ([BF 4   − ]), hexafluorophosphate ([PF 6   − ]), hexfluoroantimonate ([SbF 6   − ]) or perchlorate ([ClO 4   − ]) anion;   r) a carbonate anion selected from [CO 3 ] 2− , [HCO 3 ] − , [R 2 CO 3 ] − ; preferably [MeCO 3 ] − ;   s) polyfluoroalkoxyaluminate anions selected from [Al(OR F ) 4   − ], wherein R F  is selected from C 1-6  alkyl substituted by one or more fluoro groups;   
       where: R 1  and R 2  are independently selected from the group consisting of C 1 -C 10  alkyl, C 6  aryl, C 1 -C 10  alkyl(C 6 )aryl and C 6  aryl(C 1 -C 10 )alkyl each of which may be substituted by one or more groups selected from: fluoro, chloro, bromo, iodo, C 1  to C 6  alkoxy, C 2  to C 12  alkoxyalkoxy, C 3  to C 8  cycloalkyl, C 6  to C 10  aryl, C 7  to C 10  alkaryl, C 7  to C 10  aralkyl, —CN, —OH, —SH, —NO 2 , —CO 2 R x , —OC(O)R x , —C(O)R x , —C(S)R x , —CS —2 R x , —SC(S)R x , —S(O)(C 1  to C 6 )alkyl, —S(O)O(C 1  to C 6 )alkyl, —OS(O)(C 1  to C 6 )alkyl, —S(C 1  to C 6 )alkyl, —S—S(C 1  to C 6  alkyl), —NR x C(O)NR y R z , —NR x C(O)OR y , —OC(O)NR y R z , —NR x C(S)OR y , —OC(S)NR y R z , —NR x C(S)SR y , —SC(S)NR y R z , —NR x C(S)NR y R z , —C(O)NR y R z , —C(S)NR y R z , —NR y R z , or a heterocyclic group, wherein R x , R y  and R z  are independently selected from hydrogen or C 1  to C 6  alkyl, wherein R 1  may also be fluorine, chlorine, bromine or iodine. 
     
     
         83 . The ionic liquid of  claim 69 , wherein [Cat + ] represents one or more ionic species having the structure: 
       
         
           
           
               
               
           
         
         where: [Z + ] represents a group selected from ammonium, benzimidazolium, benzofuranium, benzothiophenium, benzotriazolium, borolium, cinnolinium, diazabicyclodecenium, diazabicyclononenium, 1,4-diazabicyclo[2.2.2]octanium, diazabicyclo-undecenium, dithiazolium, furanium, guanidinium, imidazolium, indazolium, indolinium, indolium, morpholinium, oxaborolium, oxaphospholium, oxazinium, oxazolium, iso-oxazolium, oxothiazolium, phospholium, phosphonium, phthalazinium, piperazinium, piperidinium, pyranium, pyrazinium, pyrazolium, pyridazinium, pyridinium, pyrimidinium, pyrrolidinium, pyrrolium, quinazolinium, quinolinium, iso-quinolinium, quinoxalinium, quinuclidinium, selenazolium, sulfonium, tetrazolium, thiadiazolium, iso-thiadiazolium, thiazinium, thiazolium, iso-thiazolium, thiophenium, thiuronium, triazinium, triazolium, iso-triazolium and uronium groups. 
       
     
     
         84 . The ionic liquid of  claim 69  further comprising a lower viscosity ionic liquid, selected from ammonium, benzimidazolium, benzofuranium, benzothiophenium, benzotriazolium, borolium, cinnolinium, diazabicyclodecenium, diazabicyclononenium, 1,4-diazabicyclo [2.2.2]octanium, diazabicyclo-undecenium, dithiazolium, furanium, guanidinium, imidazolium, indazolium, indolinium, indolium, morpholinium, oxaborolium, oxaphospholium, oxazinium, oxazolium, iso-oxazolium, oxothiazolium, phospholium, phosphonium, phthalazinium, piperazinium, piperidinium, pyranium, pyrazinium, pyrazolium, pyridazinium, pyridinium, pyrimidinium, pyrrolidinium, pyrrolium, quinazolinium, quinolinium, iso-quinolinium, quinoxalinium, quinuclidinium, selenazolium, sulfonium, tetrazolium, thiadiazolium, iso-thiadiazolium, thiazinium, thiazolium, iso-thiazolium, thiophenium, thiuronium, triazinium, triazolium, iso-triazolium and uronium groups. 
     
     
         85 . The ionic liquid of  claim 69  comprising than 25% halide or pseudohalide anions as a proportion of the total anions. 
     
     
         86 . The ionic liquid of  claim 69  further comprising one or more organic solvents. 
     
     
         87 . The ionic liquid of  claim 86 , further comprising a rare earth metal. 
     
     
         88 . A method for preparing an ionic liquid as defined in  claim 69 , said method comprising reacting: 
       
         
           
           
               
               
           
         
         where: LG represents a leaving group.