Process for the preparation of perfluorocarbons

• US 5,744,657 A
• Filed: 12/18/1995
• Issued: 04/28/1998
• Est. Priority Date: 12/22/1994
• Status: Expired due to Term

• Current Assignee: The Chemours Company FC, LLC (The Chemours Company)
• Original Assignee: E. I. du Pont de Nemours and Company (Corteva, Inc.)
• Inventors: Webster, James Lang
• Primary Examiner(s): SIEGEL, ALAN M
• Application Number:
  US08/573,828
• Time in Patent Office: 862 Days
• Field of Search: 570/150, 570/142
• US Class Current: 570/150
• CPC Class Codes: C07C 17/00 Preparation of halogenated hydrocarbons
• CPC Class Codes: C07C 17/007 from carbon or from carbides and halogens

Abstract

Tetrafluoroethylene and other valuable 2-carbon atom fluorocarbon is made by reacting fluorine-containing compound such metal fluoride with CO in an energized state, e.g. plasma excitation, to form a gaseous reaction mixture which is a precursor to COF₂, followed by reacting this reaction mixture with carbon and quenching to obtain the desired fluorocarbon.

Claims

1. Process for the preparation of perfluorocarbon containing at least two carbon atoms, comprising

feeding fluorine-containing compound having a molecular weight greater than 20 and gaseous CO to a reaction zone wherein the fluorine-containing compound is split apart to liberate fluorine from said fluorine-containing compound and obtaining a gaseous reaction mixture which contains said fluorine and said CO,

reacting said reaction mixture with carbon at a temperature of at least 1500°

C. to obtain a gaseous reaction product,

rapidly cooling said gaseous reaction product to obtain said perfluorocarbon as a result thereof, and

recovering said perfluorocarbon from said gaseous reaction product.

2. The process of claim 1 wherein said reaction zone is at an elevated temperature and said fluorine and CO are maintained in said gaseous mixture by cooling said mixture from the elevated temperature of said reaction zone.

3. The process of claim 2 wherein said fluorine-containing compound is metal fluoride and said gaseous reaction mixture contains metal from said metal fluoride.

4. The process of claim 3 and removing said metal from said gaseous reaction mixture prior to carrying out the reacting step.

5. The process of claim 3 wherein said gaseous reaction product of the reacting step contains said metal and said recovery of said perfluorocarbon in the recovery step includes recovery from said metal.

6. The process of claim 1 wherein the step of reacting with carbon to produce said gaseous reaction product produces CO and said CO is recycled to the feeding step.

7. The process of claim 2 wherein said process is carried out continuously and wherein heat is required for the reacting step, which heat includes heat recovered from the feeding step.

8. The process of claim 1 wherein the liberation of fluorine is caused by the energizing of said compound and said CO in said reaction zone at a temperature of at least 1500°

C.

9. The process of claim 8 wherein said temperature is at least 3500°

C.

10. The process of claim 9 wherein said reaction mixture is quenched to a temperature of 500°

C. to 2000°

C.

11. The process of claim 8 wherein the reaction temperature in the reacting step is at least 1500°

C.

12. The process of claim 3 wherein said metal fluoride is silicon fluoride.

13. The process of claim 3 wherein said metal fluoride is calcium fluorosilicate.

14. The process of claim 3 wherein said metal fluoride is calcium fluoride or sodium fluoride.

15. The process of claim 3 wherein said metal is silicon.

16. The process of claim 1 wherein at least one molecule of CO is present for each two fluorine atoms provided by said fluorine-containing compound.

17. The process of claim 1 wherein at least 50 mol % of said perfluorocarbon is tetrafluoroethylene.

18. The process of claim 1 wherein unreacted fluorine-containing compound and/or CO are recycled to the feeding step.

19. The process of claim 1 wherein any one-carbon-atom perfluorocarbon present in said resultant reaction product is recycled to the reacting step.

20. The process of claim 19 wherein said one-carbon-atom perfluorocarbon comprises CF₄.

21. The process of claim 1 wherein the splitting apart of said fluorine-containing compound is by energizing said compound by forming a plasma in said reaction zone.

22. The process of claim 21 wherein the plasma is formed of at least one of said fluorine-containing compound and said CO, and when only one of these feed materials forms said plasma, said one feed material in the resultant energized state is then brought into contact with the other of said feed materials.

23. The process of claim 1 wherein inert gas is fed to said reaction zone, and said inert gas is energized therein and in the energized state is brought into contact with said fluorine-containing compound and said CO in said reaction zone.

24. The process of claim 1 wherein said fluorine and CO in said gaseous reaction mixture is capable of forming COF₂.

34. The process of claim 1 wherein said fluorine-containing compound is selected from the group consisting of metal fluoride and organic-fluorine containing compound.

35. The process of claim 34 wherein said organic fluorine-containing compound is CH₄ or C₂ F₆.

36. The process of claim 34 wherein said metal of said metal fluoride is selected from the group consisting of elements in Groups IA, excluding hydrogen, IB, IIA, IIB, IIIA, IIIB, IVA, excluding nitrogen, VB, VIA, excluding oxygen, VIB, VIIB, and VIII of the Periodic Table.

25. Process comprising contacting and reacting fluorine-containing compound with CO to form a gaseous reaction mixture which is capable of being quenched to form COF₂ and contacting and reacting said gaseous reaction mixture with carbon to form a second gaseous reaction mixture which is capable of being quenched to form perfluorocarbon which contains at least 2 carbon atoms and quenching said second gaseous reaction mixture.

26. The process of claim 25 wherein said fluorine-containing compound is metal fluoride and said first-mentioned gaseous reaction mixture contains metal liberated from metal fluoride, and removing said metal from said gaseous reaction mixture prior to said contacting and reacting with carbon.

27. The process of claim 25 wherein said contacting and reacting with carbon produces CO which is recycled to the first-mentioned contacting and reacting step.

28. The process of claim 25 wherein said perfluorocarbon is perfluoroolefin.

30. The process of claim 26 wherein said perfluorocarbon is perfluoroolefin.

29. Process of reacting metal fluoride and CO by plasma excitation to form a gaseous reaction mixture which is capable of being quenched to COF₂ and reacting at least a portion of said gaseous mixture with carbon at a temperature of at least 1500°

C. to form a second gaseous mixture which is capable of being quenched to form perfluorocarbon containing at least 2 carbon atoms and quenching said second gaseous reaction mixture.

31. The process of claim 29 wherein said metal fluoride is heated to liberate fluorine therefrom for reaction with said CO and said metal is in the first-mentioned gaseous reaction mixture.

32. The process of claim 31 and recovering said metal from said first-mentioned or said second gaseous reaction mixture.

33. The process of claim 29 wherein said reaction of said metal fluoride with said CO occurs by plasma excitation and said first-mentioned gaseous reaction mixture is capable of being quenched to COF₂.