Processes for forming titanium catechol complexes

• US 10,377,687 B2
• Filed: 02/17/2017
• Issued: 08/13/2019
• Est. Priority Date: 07/26/2016
• Status: Active Grant

• Current Assignee: Lockheed Martin Corporation (Martin Marietta Corporation)
• Original Assignee: Lockheed Martin Corporation (Martin Marietta Corporation)
• Inventors: Millard, Matthew, Goeltz, John
• Primary Examiner(s): Conley, Helen Oi K
• Application Number:
  US15/436,716
• Publication Number:
  US 20180029966A1
• Time in Patent Office: 907 Days
• CPC Class Codes: C07C 37/66 by conversion of hydroxy groups to O-metal groups
• CPC Class Codes: C07F 7/28 Titanium compounds
• CPC Class Codes: H01M 8/188 by recharging of redox couples containing fluids; Redox flow type batteries
• CPC Class Codes: Y02E 60/50 Fuel cells

Abstract

Titanium complexes containing at least one catecholate ligand can be desirable active materials for flow batteries and other electrochemical energy storage systems. Such complexes can be formed through reacting a catechol compound with a titanium reagent in an organic solvent, removing a byproduct species, and then obtaining an aqueous phase containing a salt form of the titanium catechol complex, particularly an alkali metal salt form. More specifically, the methods can include: forming a catechol solution containing a catechol compound and an organic solvent, contacting a titanium reagent with the catechol solution to form a reaction mixture, reacting the titanium reagent with the catechol compound to form an intermediate titanium catechol complex and a byproduct species, separating the byproduct species, and combining an alkaline aqueous solution containing a base with the intermediate titanium catechol complex to produce a salt form titanium catechol complex at least partially dissolved in an aqueous phase.

Claims

1. A method comprising:

forming a catechol solution comprising a catechol compound and an organic solvent;

contacting a titanium reagent with the catechol solution to form a reaction mixture;

reacting the titanium reagent with the catechol compound to form an intermediate titanium catechol complex and a byproduct species;

separating the byproduct species from the intermediate titanium catechol complex; and

combining an alkaline aqueous solution with the intermediate titanium catechol complex, the alkaline aqueous solution comprising a base;

wherein the base converts the intermediate titanium catechol complex into a salt form titanium catechol complex that is at least partially dissolved in an aqueous phase.

2. The method of claim 1, wherein the base comprises an alkali metal base.

3. The method of claim 2, wherein the alkali metal base comprises an alkali metal hydroxide.

4. The method of claim 2, wherein the base further comprises an ammonium base.

5. The method of claim 1, wherein the titanium reagent is selected from the group consisting of titanium tetrachloride, titanium tetrabromide, titanium tetraiodide, a titanium mixed tetrahalide, titanium oxychloride, titanium oxybromide, titanium oxyiodide, titanium oxysulfate, and a titanium alkoxide.

6. The method of claim 5, wherein the byproduct species comprises one or more hydrogen halides.

7. The method of claim 6, wherein the byproduct species is separated from the intermediate titanium catechol complex by maintaining the reaction mixture at reduced pressure, contacting the reaction mixture with a flowing inert gas, or any combination thereof before combining the alkaline aqueous solution with the intermediate titanium catechol complex.

8. The method of claim 6, wherein the intermediate titanium catechol complex is isolated from the reaction mixture to separate the byproduct species from the intermediate titanium catechol complex before combining the alkaline aqueous solution with the intermediate titanium catechol complex.

9. The method of claim 5, wherein the byproduct species comprises sulfuric acid.

10. The method of claim 9, wherein the intermediate titanium catechol complex is isolated from the reaction mixture to separate the byproduct species from the intermediate titanium catechol complex before combining the alkaline aqueous solution with the intermediate titanium catechol complex.

11. The method of claim 9, wherein the byproduct species is separated from the intermediate titanium catechol complex by contacting the reaction mixture with a solvent in which the sulfuric acid is miscible but the intermediate titanium catechol complex is not, the solvent in which the sulfuric acid is miscible also being immiscible with the organic solvent comprising the reaction mixture.

12. The method of claim 5, wherein the byproduct species comprises an alcohol.

13. The method of claim 12, wherein the byproduct species is separated from the intermediate titanium catechol complex by maintaining the reaction mixture at reduced pressure, contacting the reaction mixture with a flowing inert gas, or any combination thereof before combining the alkaline aqueous solution with the intermediate titanium catechol complex.

14. The method of claim 12, wherein the intermediate titanium catechol complex is isolated from the reaction mixture to separate the byproduct species from the intermediate titanium catechol complex before combining the alkaline aqueous solution with the intermediate titanium catechol complex.

15. The method of claim 12, wherein the byproduct species is separated from the intermediate titanium catechol complex by contacting the reaction mixture with a solvent in which the alcohol is miscible but the intermediate titanium catechol complex is not, the solvent in which the alcohol is miscible also being immiscible with the organic solvent comprising the reaction mixture.

16. The method of claim 1, wherein the organic solvent comprises a water-immiscible organic solvent.

17. The method of claim 16, wherein the water-immiscible organic solvent is selected from the group consisting of toluene, xylenes, cyclohexane, dichloromethane, dichloroethane, and any combination thereof.

18. The method of claim 1, wherein an amount of base in the alkaline aqueous solution is such that the aqueous phase containing the salt form titanium catechol complex has a pH of from about 6 to about 8.

19. The method of claim 18, further comprising adding an additional quantity of the alkaline aqueous solution or a different alkaline aqueous solution to the aqueous phase to adjust the pH of the aqueous phase to a range of from about 9 to about 10.

20. The method of claim 1, wherein the intermediate titanium catechol complex and the salt form titanium catechol complex are formed consecutively in a single reaction vessel.

21. The method of claim 1, further comprising separating the aqueous phase and an organic phase from one another, the organic phase comprising the organic solvent.

22. A method comprising:

forming a catechol solution comprising a catechol compound and an organic solvent;

contacting a titanium alkoxide with the catechol solution to form a reaction mixture;

reacting the titanium alkoxide with the catechol compound to form an intermediate titanium catechol complex and an alcohol; and

without separating the intermediate titanium catechol complex from the alcohol, combining an alkaline aqueous solution with the intermediate titanium catechol complex, the alkaline aqueous solution comprising a base;

wherein the base converts the intermediate titanium catechol complex into a salt form titanium catechol complex that is at least partially dissolved in an aqueous phase further comprising the alcohol.

23. The method of claim 22, further comprising separating the alcohol from the aqueous phase.