Dissolution and processing of cellulose using ionic liquids

• US 6,824,599 B2
• Filed: 09/27/2002
• Issued: 11/30/2004
• Est. Priority Date: 10/03/2001
• Status: Expired due to Term

• Current Assignee: University of Alabama (University of Alabama System)
• Original Assignee: University of Alabama (University of Alabama System)
• Inventors: Holbrey, John David, Swatloski, Richard Patrick, Rogers, Robin Don
• Primary Examiner(s): BRUNSMAN, DAVID M
• Application Number:
  US10/256,521
• Publication Number:
  US 20030157351A1
• Time in Patent Office: 795 Days
• Field of Search: 106/164.3, 106/200.2, 106/163.01
• US Class Current: 106/163.01
• CPC Class Codes: C08B 1/003 Preparation of cellulose solutions, i.e. dopes, with different possible solvents, e.g. ionic liquids solutions used in the manufacture of monocomponent artificial filaments or cellulose or derivatives thereof D01F2/02
• CPC Class Codes: C08J 11/08 using selective solvents for polymer components
• CPC Class Codes: C08J 2301/02 Cellulose; Modified cellulose
• CPC Class Codes: C08J 3/096 Nitrogen containing compounds
• CPC Class Codes: C08J 3/28 Treatment by wave energy or particle radiation
• CPC Class Codes: C08L 1/06 Cellulose hydrate
• CPC Class Codes: C12N 11/12 Cellulose or derivatives thereof
• CPC Class Codes: D01F 2/02 from solutions of cellulose in acids, bases or salts
• CPC Class Codes: Y02W 30/62 Plastics recycling; Rubber recycling
• CPC Class Codes: Y10T 428/31772 Next to cellulosic
• CPC Class Codes: Y10T 428/31971 Of carbohydrate

Abstract

Cellulose is dissolved in an ionic liquid without derivatization, and is regenerated in a range of structural forms without requiring the use of harmful or volatile organic solvents. Cellulose solubility and the solution properties can be controlled by the selection of the ionic liquid constituents, with small cations and halide or pseudohalide anions favoring solution.

Claims

1. A method for dissolving cellulose that comprises admixing cellulose with a molten ionic liquid that is molten at a temperature of about −

10 to about 100°

C. and in the substantial absence of water or a nitrogen-containing base to form an admixture, wherein said ionic liquid is comprised of cations and anions, and agitating the a mixture until dissolution is complete.

2. The method according to claim 1 wherein said admixture is irradiated with microwave radiation to assist in dissolution.

3. The method according to claim 1 wherein the cations of said ionic liquid are selected from the group consisting of

wherein R¹ and R² are independently a C₁-C₆ alkyl group or a C₁-C₆ alkoxyalkyl group, and R³, R⁴, R⁵, R⁶, R⁷, R⁸ and R⁹ (R³-R⁹), when present, are independently a hydrido, a C₁-C₆ alkyl, a C₁-C₆ alkoxyalkyl group or a C₁-C₆ alkoxy group, and the anions of the ionic liquid are halogen, pseudohalogen, or C₂-C₆ carboxylate.

4. The method according to claim 1 wherein the anions of said ionic liquid are halogen or pseudohalogen.

5. A method for dissolving cellulose that comprises the steps of:

(a) admixing cellulose with an ionic liquid in the substantial absence of water or nitrogen-containing base to form an admixture, wherein said ionic liquid is molten at a temperature of about −

10 to about 100°

C. and is comprised of cations and anions, wherein the cations correspond in structure to a formula selected from the group consisting of

wherein R¹ and R² are independently a C₁-C₆ alkyl group or a C₁-C₆ alkoxyalkyl group, and R³, R⁴, R⁵, R⁶, R⁷, R⁸ and R⁹ (R³-R⁹), when present, are independently a hydrido, a C₁-C₆ alkyl, a C₁-C₆ alkoxyalkyl group or a C₁-C₆ alkoxy group, and the anions of the ionic liquid are halogen, pseudohalogen, or C₁-C₆ carboxylate;

(b) irradiating said admixture with microwave radiation to assist in dissolution; and

(c) agitating the admixture until dissolution is complete.

6. The method according to claim 5 wherein said cellulose is fibrous cellulose, wood pulp, linters, cotton balls or paper.

7. The method according to claim 5 wherein said cation contains a single five-membered ring that is free of fusion to other ring structures.

8. The method according to claim 5 wherein R³-R⁹ are hydrido.

9. A method for dissolving cellulose that comprises the steps of:

(a) admixing cellulose with an ionic liquid comprised of cations and anions in the substantial absence of water to form an admixture, wherein said ionic liquid is molten at a temperature of about −

44°

C. to about 120°

C. wherein said cations contain a single five-membered ring that is free of fusion to other ring structures and said anions are halogen, pseudohalogen, or C₁-C₆ carboxylate;

(b) irradiating said admixture with microwave radiation to assist in dissolution; and

(c) agitating the admixture until dissolution is complete.

10. The method according to claim 9 wherein said cellulose is fibrous cellulose, wood pulp, linters, cotton balls or paper.

11. The method according to claim 9 wherein said cations have a structure that corresponds to a formula selected from the group consisting of

wherein R¹ and R² are independently a C₁-C₆ alkyl group or a C₁-C₆ alkoxyalkyl group, and R³, R⁴, R⁵ (R³-R⁵) are independently a hydrido, a C₁-C₆ alkyl group, a C₁-C₆ alkoxyalkyl group or a C₁-C₆ alkoxy group.

12. The method according to claim 11 wherein R³-R⁵ are hydrido.

13. The method according to claim 11 wherein said cation is a 1,3-di-C₁-C₆-alkyl imidazolium ion.

14. The method according to claim 13 wherein one of said 1,3-di-C₁-C₆-alkyl groups is methyl.

15. A method for dissolving cellulose that comprises the steps of:

(a) admixing cellulose with an ionic liquid comprised of cations and anions in the substantial absence of water to form an admixture, wherein said ionic liquid is molten at a temperature of about −

44°

C. to about 120°

C., wherein the cations are 1,3-di-C₁-C₆-alkyl imidazolium ions corresponding in structure to Formula A

wherein R¹ and R² are independently a C₁-C₆ alkyl group or a C₁-C₆ alkoxyalkyl group, and R³, R⁴, R⁵ (R³-R⁵) are independently a hydrido, a C₁-C₆ alkyl group, a C₁-C₆ alkoxyalkyl group or a C₁-C₆ alkoxy group and the anions of the ionic liquid are a halogen or pseudohalogen;

(b) irradiating said admixture with microwave radiation to assist in dissolution; and

(c) agitating the admixture until dissolution is complete.

16. The method according to claim 15 wherein said cellulose is fibrous cellulose, wood pulp linters, cotton balls or paper.

17. The method according to claim 15 wherein R³-R⁵ are hydrido, and R¹ and R² are each a C₁-C₆ alkyl group.

18. The method according to claim 15 wherein one of said C₁-C₆-alkyl groups is methyl.

19. The method according to claim 15 wherein said anion is a chloride ion.

20. A method for dissolving cellulose that comprises the steps of:

(a) admixing cellulose with an ionic liquid comprised of cations and anions in the substantial absence of water to form an admixture, wherein said ionic liquid is molten at a temperature of about −

44°

C. to about 120°

C., and wherein the cations are 1,3-di-C₁-C₆-alkyl imidazolium ions corresponding in structure to Formula B

wherein R¹ is a C₁-C₆ alkyl group and the anions of the ionic liquid are a halogen or pseudohalogen;

(b) irradiating said admixture with microwave radiation to assist in dissolution; and

(c) agitating the admixture until dissolution is complete.

21. The method according to claim 20 wherein said cellulose is fibrous cellulose, wood pulp, linters, cotton balls or paper.

22. The method according to claim 20 wherein said R¹ C₁-C₆ alkyl group is a C₁-C₄ alkyl group.

23. The method according to claim 20 wherein said anions are chloride ions.

24. A solution comprised of cellulose in a molten ionic liquid solvent that is substantially free of water or a nitrogen-containing base, wherein said ionic liquid is comprised of cations and anions and is molten at a temperature of about −

44°

C. to about 120°

C., and wherein said cations contain a single five-membered ring that is free of fusion to other ring structures and said anions are halogen, pseudohalogen, or C₁-C₆ carboxylate.

25. The solution according to claim 24 wherein said cellulose is present in an amount of about 5 to about 35 weight percent of the solution.

26. The solution according to claim 24 wherein said cations of said ionic liquid correspond in structure to a formula selected from the group consisting of

wherein R¹ and R² are independently a C₁-C₆ alkyl group or a C₁-C₆ alkoxyalkyl group, and R³, R⁴, and R⁵ (R³-R⁵), when present, are independently a hydrido, a C₁-C₆ alkyl, a C₁-C₆ alkoxyalkyl group or C₁-C₆ alkoxy group, and the anions of the ionic liquid are halogen, pseudohalogen, or C₁-C₆ carboxylate.

27. The solution according to claim 24 wherein the anions of said ionic liquid are halogen or pseudohalogen.

28. A solution comprise of about 5 to about 35 weight percent cellulose in an ionic liquid solvent that is molten at a temperature of about −

10 about 100°

C. and is substantially free of water or nitrogen-containing base, wherein said ionic liquid is comprised of cations and anions in which the cations correspond in structure to a formula selected from the group consisting of

wherein R¹ and R² are independently a C₁-C₆ alkyl group or a C₁-C₆ alkoxyalkyl group, and R³, R⁴, R⁵, R⁶, R⁷, R⁸ and R⁹ (R³-R⁹), when present, are independently a hydrido, a C₁-C₆ alkyl, a C₁-C₆ alkoxyalkyl group or a C₁-C₆ alkoxy group, and the anions of the ionic liquid are halogen, pseudohalogen, or C₁-C₆ carboxylate.

29. The solution according to claim 28 wherein said cations contain a single five-membered ring that is free of fusion to other ring structures.

30. The solution according to claim 29 wherein said cations have a structure that corresponds to a formula selected from the group consisting of

wherein R¹ and R² are independently a C₁-C₆ alkyl group or a C₁-C₆ alkoxyalkyl group, and R³, R⁴, R⁵ (R³-R⁵) are independently a hydrido, a C₁-C₆ alkyl group, a alkoxyalkyl group or a C₁-C₆ alkoxy group.

31. The solution according to claim 30 wherein said cation is a 1,3-di-C₁-C₆ alkyl imidazolium ion that corresponds in structure to Formula A

32. The solution according to claim 31 wherein one of said 1,3-di-C₁-C₆ alkyl groups is methyl.

33. The solution according to claim 31 wherein said R³-R⁵ groups are each hydrido.

34. The solution according to claim 31 wherein said cellulose is present in an amount of about 10 to about 25 weight percent.

35. A solution comprised of about 10 to about 25 weight percent cellulose in an ionic liquid solvent that is molten a temperature of about −

10 to about 100°

C. and is substantially free of water, wherein said ionic liquid is comprised of cations and anions in which the cations are 1,3-di-C₁-C₆ alkyl imidazolium ions corresponding in structure to Formula A

wherein R¹ and R² are independently a C₁-C₆ alkyl group or a C₁-C₆ alkoxyalkyl group, and R³, R⁴, R⁵ (R³ R⁵) are independently a hydrido, a C₁-C₆ alkyl group, a C₁-C₆ alkoxyalkyl group or a C₁-C₆ alkoxy group and the anions of the ionic liquid are a halogen or pseudohalogen.

36. The solution according to claim 35 wherein one of said 1,3-di-C₁-C₆ alkyl groups is methyl.

37. The solution according to claim 35 wherein said R³-R⁵ groups are each hydrido.

38. The solution according to claim 37 wherein the other of said R¹ is C₁-C₄-alkyl.

39. The solution according to claim 38 wherein said cations correspond in structure to Formula B

40. The solution according to claim 39 wherein said anions are chloride ions.

41. A method for regenerating cellulose that comprises admixing a solution of cellulose in a molten ionic liquid solvent that is substantially free of water or nitrogen-containing base, wherein said ionic liquid is comprised of cations and anions and said molten ionic liquid is either (i) molten at a temperature of about −

10°

C. to about 100°

C. or (ii) is molten at a temperature of about −

44°

C. to about 120°

C. and wherein said cations contain a single five-membered ring that is free of fusion to other ring structures, with a liquid non-solvent for said cellulose that is miscible with said ionic liquid, said admixing causing the cellulose and ionic liquid to form solid and liquid phases, respectively.

42. The method according to claim 41 wherein the cations of said ionic liquid correspond in structure to a formula selected from the group consisting of

wherein R¹ and R² are independently a C₁-C₆ alkyl group or a C₁-C₆ alkoxyalkyl group, and R³, R⁴, R⁵, R⁶, R⁷, R⁸ and R⁹ (R³-R⁹), when present, are independently a hydrido, a C₁-C₆ alkyl, a C₁-C₆ alkoxyalkyl group or a C₁-C₆ alkoxy group, and the anions of the ionic liquid are halogen, pseudohalogen, or C₁-C₆ carboxylate.

43. The method according to claim 41 wherein the anions of said ionic liquid are halogen or pseudohalogen.

44. The method according to claim 41 including the further step of collecting the formed cellulose phase.

45. A method for regenerating cellulose that comprises the steps of:

(a) admixing a solution of cellulose in a molten ionic liquid solvent that is molten at a temperature of less than about 150°

C. and is substantially free of water or a nitrogen-containing base, wherein said ionic liquid is comprised of cations and anions, with a liquid non-solvent for said cellulose that is miscible with said ionic liquid, said admixing causing the cellulose and ionic liquid to form solid and liquid phases, respectively, wherein the cations correspond in structure to a formula selected from the group consisting of

wherein R¹ and R² are independently a C₁-C₆ alkyl group or a C₁-C₆ alkoxyalkyl group, and R³, R⁴, R⁵, R⁶ R⁷, R⁸ and R⁹ (R³-R⁹), when present, are independently a hydrido, a C₁-C₆ alkyl, a C₁-C₆ alkoxyalkyl group or a C₁-C₆ alkoxy group, and the anions of the ionic liquid are halogen, pseudohalogen, or C₁-C₆ carboxylate and the anions of said ionic liquid are halogen or pseudohalogen; and

(b) collecting the formed cellulose phase.

46. The method according to claim 45 wherein said ionic liquid is molten at a temperature of about −

44°

to about 120°

C.

47. The method according to claim 45 wherein said liquid non-solvent for said cellulose that is miscible with said ionic liquid is also miscible with water.

48. A method for regenerating cellulose that comprises the steps of:

(a) admixing a solution of cellulose in a molten ionic liquid solvent that is molten at a temperature of about −

44°

to about 120°

C. and is substantially free of water, herein said ionic liquid is comprised of cations and anions, with a liquid non-solvent for said cellulose that is miscible with said ionic liquid and is also miscible with water, said admixing causing the cellulose and ionic liquid to form solid a d liquid phases, respectively, wherein the cations correspond in structure to a formula selected from the group consisting of

wherein R¹ and R² are independently a C₁-C₆ alkyl group or a C₁-C₆ alkoxyalkyl group, and R³, R⁴, R⁵ (R³-R⁵) are independently a hydrido, a C₁-C₆ alkyl group, a C₁-C₆ alkoxyalkyl group or a C₁-C₆ alkoxy group and the anions of the ionic liquid are a halogen or pseudohalogen; and

(b) collecting the formed cellulose phase.

49. The method according to claim 48 wherein said cation is a 1,3-di-C₁-C₆ alkyl imidazolium ion that corresponds in structure to Formula A

50. The method according to claim 49 wherein one of said 1,3-di-C₁-C₆ alkyl groups is methyl.

51. The method according to claim 50 wherein R¹ is C₁-C₄-alkyl.

52. The method according to claim 51 wherein said R³-R⁵ groups are each hydrido.

53. The method according to claim 52 wherein said anions are chloride ions.

54. The method according to claim 53 wherein said liquid non-solvent for said cellulose that is miscible with said ionic liquid and is also miscible with water is water, an alcohol or ketone.

55. The method according to claim 54 wherein said admixing step is carried out by extruding said cellulose solution through a die and into said non-solvent.

56. The method according to claim 51 wherein said cations correspond in structure to Formula B

57. The method according to claim 56 wherein said cellulose is initially present in said solution in an amount of about 10 to about 25 weight percent.

58. The method according to claim 57 wherein said liquid non-solvent is water.