Ionic liquid solvents of perhalide type for metals and metal compounds

Abstract

The present invention relates to a process for dissolving metals in perhalide containing ionic liquids, and to the extraction of metals from mineral ores; the remediation of materials contaminated with heavy, toxic or radioactive metals; and to the removal of heavy and toxic metals from hydrocarbon streams.

Claims

1. A method of extracting metals and metal compounds from aqueous solutions comprising contacting the aqueous solution with an ionic liquid having the formula:
[Cat.sup.+][X.sup.−] wherein: [Cat.sup.+] represents one or more cationic species, and [X.sup.−] represents one or more perhalide anions, wherein the ionic liquid is free of additional solvents and/or oxidants.

2. A method according to claim 1, wherein [X.sup.−] comprises at least one perhalide anion selected from [I.sub.3].sup.−, [BrI.sub.2].sup.−, [Br.sub.2I].sup.−, [ClI.sub.2].sup.−, [Br.sub.3].sup.−, [ClBr.sub.2], [BrCl.sub.2].sup.−, [ICl.sub.2].sup.−, or [Cl.sub.3].sup.−.

3. A method according to claim 2, wherein [X.sup.−] comprises at least one perhalide anion selected from [BrI.sub.2].sup.−, [Br.sub.2I].sup.−, [ClI.sub.2].sup.−, [ClBr.sub.2].sup.−, [BrCl.sub.2].sup.−; or [ICl.sub.2].sup.−.

4. A method according to claim 2, wherein [X.sup.−] comprises at least one perhalide anion selected from [I.sub.3].sup.−, [Br.sub.3].sup.−, or [Cl.sub.3].sup.−.

5. A method according to claim 1, wherein [Cat.sup.+] is a cationic species selected from the group consisting of: ammonium, azaannulenium, azathiazolium, benzimidazolium, benzofuranium, benzotriazolium, borolium, cinnolinium, diazabicyclodecenium, diazabicyclononenium, diazabicyclo-undecenium, dithiazolium, furanium, guanidinium, imidazolium, indazolium, indolinium, indolium, morpholinium, oxaborolium, oxaphospholium, oxazinium, oxazolium, iso-oxazolium, oxathiazolium, pentazolium, phospholium, phosphonium, phthalazinium, piperazinium, piperidinium, pyranium, pyrazinium, pyrazolium, pyridazinium, pyridinium, pyrimidinium, pyrrolidinium, pyrrolium, quinazolinium, quinolinium, iso-quinolinium, quinoxalinium, selenozolium, sulfonium, tetrazolium, iso-thiadiazolium, thiazinium, thiazolium, thiophenium, thiuronium, triazadecenium, triazinium, triazolium, iso-triazolium, and uronium.

6. A method according to claim 5 wherein [Cat.sup.+] is a cationic species selected from the group consisting of: ##STR00010## wherein: R.sup.a, R.sup.b, R.sup.c, R.sup.d, R.sup.e, R.sup.f and R.sup.g are each independently selected from hydrogen, a C.sub.1 to C.sub.30, straight chain or branched alkyl group, a C.sub.3 to C.sub.8 cycloalkyl group, or a C.sub.6 to C.sub.10 aryl group, or any two of R.sup.b, R.sup.c, R.sup.d, R.sup.e and R.sup.f attached to adjacent carbon atoms form a methylene chain —(CH.sub.2).sub.q— wherein q is from 3 to 6; and wherein said alkyl, cycloalkyl or aryl groups or said methylene chain are unsubstituted or may be substituted by one to three groups selected from: C.sub.1 to C.sub.6 alkoxy, C.sub.2 to C.sub.12 alkoxyalkoxy, C.sub.3 to C.sub.8 cycloalkyl, C.sub.6 to C.sub.10 aryl, C.sub.7 to C.sub.10 alkaryl, C.sub.7 to C.sub.10 aralkyl, —CN, —OH, —SH, —NO.sub.2, —CO.sub.−2R.sup.x, —OC(O)R.sup.x, —C(O)R.sup.x, —C(S)R.sup.x, —CS.sub.2R.sup.x, —SC(S)R.sup.x, —S(O)(C.sub.1 to C.sub.6)alkyl, —S(O)O(C.sub.1 to C.sub.6)alkyl, —OS(O)(C.sub.1 to C.sub.6)alkyl, —S(C.sub.1 to C.sub.6)alkyl, —S—S(C.sub.1 to C.sub.6 alkyl), —NR.sup.xC(O)NR.sup.yR.sup.z, —NR.sup.xC(O)OR.sup.y, —OC(O)NR.sup.yR.sup.z, —NR.sup.xC(S)OR.sup.y, —OC(S)NR.sup.yR.sup.z, —NR.sup.xC(S)SR.sup.y, —SC(S)NR.sup.yR.sup.z, —NR C(S)NR.sup.yR.sup.z, —C(O)NR.sup.yR.sup.z, —C(S)NR.sup.yR.sup.z, —NR.sup.yR.sup.z, or a heterocyclic group, wherein R.sup.x, R.sup.y and R.sup.z are independently selected from hydrogen or C.sub.1 to C.sub.6 alkyl.

7. A method according to according to claim 6 wherein [Cat.sup.+] is a cationic species selected from the group consisting of: ##STR00011## wherein: R.sup.a, R.sup.b, R.sup.c, R.sup.d, R.sup.e, R.sup.f and R.sup.g are as defined in claim 6.

8. A method according to according to claim 7 wherein [Cat.sup.+] is a cationic species selected from the group consisting of: ##STR00012## wherein: R.sup.a and R.sup.g are as defined in claim 6.

9. A method according to claim 5, wherein [Cat.sup.+] is selected from the group consisting of:
[N(R.sup.a)(R.sup.b)(R.sup.c)(R.sup.d)].sup.+,[P(R.sup.a)(R.sup.b)(R.sup.c)(R.sup.d)].sup.+, and [S(R.sup.a)(R.sup.b)(R.sup.c)].sup.+, wherein: R.sup.a, R.sup.b, R.sup.c, and R.sup.d are each independently selected from a C.sub.1 to C.sub.30, straight chain or branched alkyl group, a C.sub.3 to C.sub.8 cycloalkyl group, or a C.sub.6 to C.sub.10 aryl group, or any two of R.sup.b, R.sup.c, R.sup.d, R.sup.e and R.sup.f attached to adjacent carbon atoms form a methylene chain —(CH.sub.2).sub.q— wherein q is from 3 to 6; and wherein said alkyl, cycloalkyl or aryl groups or said methylene chain are unsubstituted or may be substituted by one to three groups selected from: C.sub.1 to C.sub.6 alkoxy, C.sub.2 to C.sub.12 alkoxyalkoxy, C.sub.3 to C.sub.8 cycloalkyl, C.sub.6 to C.sub.10 aryl, C.sub.7 to C.sub.10 alkaryl, C.sub.7 to C.sub.10 aralkyl, —CN, —OH, —SH, —NO.sub.2, —CO.sub.−2R.sup.x, —OC(O)R.sup.x, —C(O)R.sup.x, —C(S)R.sup.x, —CS.sub.2R.sup.x, —SC(S)R.sup.x, —S(O)O(C.sub.1 to C.sub.6)alkyl, —OS(O)(C.sub.1 to C.sub.6)alkyl, —S(C.sub.1 to C.sub.6)alkyl, —S—S(C.sub.1 to C.sub.6)alkyl, —NR.sup.xC(O)NR.sup.yR.sup.z, —NR.sup.xC(O)OR.sup.y, —OC(O)NR.sup.yR.sup.z, —NR.sup.xC(S)OR.sup.y, —OC(S)NR.sup.yR.sup.z, —NR.sup.xC(S)SR.sup.y, —SC(S)NR.sup.yR.sup.z, —NR.sup.1C(S)NR.sup.yR.sup.z, —C(O)NR.sup.yR.sup.z, —C(S)NR.sup.yR.sup.z, —NR.sup.yR.sup.z, or a heterocyclic group, wherein R.sup.x, R.sup.Y and R.sup.z are independently selected from hydrogen or C.sub.1 to C.sub.6 alkyl, and wherein one of R.sup.a, R.sup.b, R.sup.c, and R.sup.d may also be hydrogen.

10. A method according to claim 1, wherein the ionic liquid is hydrophobic.

11. A method according to claim 1, wherein the metal is oxidized from an initial oxidation state below its maximum oxidation state to a higher oxidation state by reaction with the ionic liquid.

12. A method according to claim 11, wherein the metal is more soluble in the ionic liquid when in the higher oxidation state than when in the initial oxidation state.

13. A method according to claim 11, wherein the oxidized metal forms a complex ion with one or more halide anions formed during the oxidation.

14. A method according to claim 13, wherein the complex ion is a halometallate anion.

15. A method according to claim 1, wherein the metal comprises a metal selected from transition metals, lanthanides, actinides, aluminium, silicon, germanium, arsenic, selenium, indium, tin, antimony, tellurium, thallium, lead, bismuth or polonium.

16. A method according to claim 15, wherein the metal comprises a precious metal selected from gold, silver, platinum, palladium, rhodium and iridium.

17. A method according to claim 15, wherein the metal comprises a toxic heavy metal selected from cadmium, mercury, indium, thallium, germanium, tin, lead, arsenic, antimony, bismuth, selenium, tellurium and polonium.

18. A method according to claim 17, wherein the metal comprises mercury.

19. A method according to claim 17, wherein the metal comprises a metal selected from silicon and germanium.

20. A method according to claim 15, wherein the metal comprises a lanthanide or an actinide.

21. A method according to claim 1, wherein the metal comprises a metal in elemental form.

22. A method according to claim 1, wherein the metal comprises a metal oxide or a metal sulfide.

23. A method according to claim 1, wherein the metal is added to the ionic liquid at a temperature of from −80° C. to 200° C.

24. A method according to claim 1, wherein the metal is added to the ionic liquid at atmospheric pressure.

Description

EXAMPLES

Example 1: Synthesis of Perhalide Ionic Liquids

(1) Ionic liquids with mixed perhalide anions ([XY.sub.2].sup.−, where X=Cl or Br, and Y=Br or I) were prepared with dialkylimidazolium, tetraalkylammonium, tetraalkylphosphonium and alkylmethylpyridinium cations (see Table 1) following literature procedures. Briefly, liquid bromine or solid iodine was added to an appropriate amount of organic halide salt to achieve the desired 1:1 molar stoichiometry, generating perhalide anions. The mixtures were mixed overnight at room temperature to yield the respective perhalide ionic liquids, which were characterised by mass spectrometry and thermogravimetric analysis (TGA).

(2) Mass spectrometry identified the presence of mass ions for the cation ([Q].sup.+) and perhalide anions ([XY.sub.2].sup.−) in each case. TGA demonstrates that the volatility of the halogen has been significantly reduced by incorporation into the ionic liquid. Mass losses, over the temperature range 150 to 300° C., corresponded to initial loss of the most volatile dihalogen from the ionic liquid (Br.sub.2 or ClBr) and associated thermal decomposition of the organic halide salt consistent with literature decomposition temperatures.

(3) TABLE-US-00001 TABLE 1 Ionic liquids prepared and physical state Physical state at Thermal Stability Cation.sup.a Anion room temperature (determined by TGA) [C.sub.4mim].sup.+ [BrI.sub.2].sup.− liquid 208° C. [C.sub.4mim].sup.+ [Br.sub.3].sup.− liquid 185° C. [C.sub.4mim].sup.+ [ClI.sub.2].sup.− liquid 205° C. [C.sub.4mim].sup.+ [ClBr.sub.2].sup.− liquid 152° C. [P.sub.6,6,6,14].sup.+ [ClBr.sub.2].sup.− liquid 194° C. [C.sub.2C.sub.2im].sup.+ [Br.sub.3].sup.− liquid 156° C. [N.sub.4,4,4,1].sup.+ [Br.sub.3].sup.− crystalline 176° C. [C.sub.4.sup.4pic].sup.+ [Br.sub.3].sup.− crystalline 155° C. .sup.a[C.sub.4mim].sup.+ = 1-butyl-3-methylimidazolium; [P.sub.6,6,6,14].sup.+ = trihexyltetradecylphosphonium; [C.sub.2C.sub.2im].sup.+ = 1,3-diethylimidazolium; [N.sub.4,4,4,1].sup.+ = tributylmethylammonium; [C.sub.4.sup.4pic].sup.+ = 1-butyl-4-methylpyridinium (4-picolinium).

Comparative Example 2: The Solubility of Bromine in Non-Halide Ionic Liquids

(4) Bromine was not found to be completely miscible at 1:1 molar ratios with either 1-butylpyridinium bistriflimide or with 1-butyl-3-methylimidazolium hydrogensulfate, and extensive evolution of bromine vapour was observed from the ionic liquid/bromine mixtures on standing under ambient conditions.

Example 3: Dissolution of Metals

(5) A range of powdered elemental metal samples (approximately 0.1 g each, accurately measured) were mixed with 1-butyl-3-methylimidazolium tribromide (1.0 mL) producing mixtures of approximately 5 wt % metal in ionic liquid. The mixtures were stirred with heating to 60° C. for 72 h, then cooled to room temperature and filtered through 2 micron nylon filters. For each sample, approximately 0.1 g of the filtrate was accurately weighed, and digested in 50 mL of 5% w/w nitric acid and the metal content determined by inductively coupled plasma (ICP) analysis. The percentage of the metal sample dissolved in the ionic liquid in each test is shown in Table 2.

(6) TABLE-US-00002 TABLE 2 Metal dissolution test results. Percentage of metal Metal dissolved in ionic liquid Aluminium 5 Chromium 49 Copper 94 Iron 71 Antimony 98 Titanium trace Tungsten 7

Example 4: Qualitative Screening of Mercury Solubilisation

(7) Qualitative screening of elemental mercury solubility in the ionic liquid systems has been made by visually observing the state of a single droplet of mercury (ca. 0.05 g) stirred in ca. 1-2 mL of ionic liquid at room temperature and at 60° C. Complete dissolution under these conditions would give mercury loadings concentrations in the order of 25-50,000 ppm (about 5 mol %).

(8) TABLE-US-00003 TABLE 3 Perhalide ionic liquids screened and observations on mercury solubility. Cation.sup.a Anion Mercury Solubility.sup.b [C.sub.4mim].sup.+ [BrI.sub.2].sup.− no solubility observed visually [C.sub.4mim].sup.+ [Br.sub.3].sup.− soluble [C.sub.4mim].sup.+ [ClI.sub.2].sup.− no solubility observed visually [C.sub.4mim].sup.+ [ClBr.sub.2].sup.− soluble [P.sub.6,6,6,14].sup.+ [ClBr.sub.2].sup.− soluble [C.sub.2C.sub.2mim].sup.+ [Br.sub.3].sup.− soluble [N.sub.4,4,4,1].sup.+ [Br.sub.3].sup.− soluble [C.sub.4.sup.4pic].sup.+ [Br.sub.3].sup.− solvent solid under test conditions .sup.a[C.sub.4mim].sup.+ = 1-butyl-3-methylimidazolium; [P.sub.6,6,6,14].sup.+ = trihexyltetradecylphosphonium; [C.sub.2C.sub.2mim].sup.+ = 1,3-diethylimidazolium; [N.sub.4,4,4,1].sup.+ = tributylmethylammonium; [C.sub.4.sup.4pic].sup.+ = 1-butyl-4-methylpyridinium (4-picolinium). .sup.bApproximately 0.05 g mercury was contacted with 1-2 mL of ionic liquid, mercury solubility at least 25,000 ppm.

Example 5: Dissolution of Bulk Mercury

(9) Elemental mercury (1.213 g, 6.05 mmol) was added to 1-butyl-3-methylimidazolium tribromide (4.52 g, 12.1 mmol) and heated at 70° C. with stirring in a sealed vessel. The dense metallic mercury drop was observed to decrease in volume over time, and after 2 hours the mercury completely dissolved into the red ionic liquid solution. On cooling to room temperature, no precipitation of mercury or mercury-containing species was observed.

Example 6: Preparation of 1-butyl-3-methylimidazolium tribromomercurate(II)

(10) Elemental mercury (3.129 g, 15.6 mmol) was added to 1-butyl-3-methylimidazolium tribromide (5.91 g, 15.6 mmol) and heated at 70° C. with stirring in a sealed vessel. The dense metallic mercury drop was observed to decrease in volume over time, and after 4 hours the mercury completely dissolved with a change in the colour of the ionic liquid from deep red to pale yellow on complete dissolution of mercury and conversion of tribromide anions to tribromomercurate(II) anions. On cooling, the new ionic liquid, 1-butyl-3-methylimidazolium tribromomercurate(II) crystallised as a pale yellow solid at 40° C.

Example 7: Preparation of bis(1,3-diethylimidazolium)tetrabromomercurate(II)

(11) Elemental mercury was added to 1,3-diethylimidazolium tribromide and heated at 70° C. with stirring in a sealed vessel. The dense metallic mercury drop was observed to decrease in volume and after 4 hours the mercury completely dissolved in the red ionic liquid. Cooling to room temperature and standing resulted in the formation of crystals from the ionic liquid which were isolated and determined to be bis(1,3-diethylimidazolium)tetrabromomercurate(II) by single crystal X-ray diffraction.

Example 8: Dissolution of Mercury in Iodine-Based Perhalide Ionic Liquids

(12) Bulk dissolution of elemental mercury was not observed in iodine-based perhalide ionic liquids, [C.sub.4mim][ClI.sub.2] and [C.sub.4mim][BrI.sub.2] or with 1-butylpyridinium bistriflimide or with 1-butyl-3-methylimidazolium hydrogen sulfate under the conditions described in Example 4.