Process for recovering paraxylene from at least two feedstreams containing xylene isomers

Patent metadata

Field	Value
Publication number	US-10351491-B2
Application number	US-201414777077-A
Country	US
Kind code	B2
Filing date	Mar 14, 2014
Priority date	Mar 15, 2013
Publication date	Jul 16, 2019
Grant date	Jul 16, 2019

Abstract

Processes for recovering paraxylene from at least two feedstreams containing xylene isomers. The process includes directing to a paraxylene recovery zone comprising at least one crystallization zone, a paraxylene-lean feedstream having a paraxylene to total xylene isomer ratio of 0.50 or less, and also directing to the paraxylene recovery zone, a paraxylene-rich feedstream having a paraxylene to total xylene isomer ratio of greater than 0.50. A paraxylene-containing product stream is recovered from the paraxylene recovery zone having a paraxylene to total xylene isomer ratio greater than that of the paraxylene-rich feedstream. The process provides improvements in paraxylene recovery efficiency and/or cost effectiveness.

First claim

What is claimed is:

1. A process for recovering paraxylene from at least two feedstreams containing xylene isomers, comprising:
directing to a paraxylene recovery zone a paraxylene-lean feedstream having a paraxylene to total xylene isomer ratio of 0.50 or less, the paraxylene recovery zone comprising at least one crystallization zone and at least one reslurry zone;
directing to the paraxylene recovery zone a paraxylene-rich feedstream having a paraxylene to total xylene isomer ratio of greater than 0.50; and
recovering from the paraxylene recovery zone a paraxylene containing product stream having a paraxylene to total xylene isomer ratio greater than that of the paraxylene-rich feedstream;
wherein the at least one reslurry zone comprises at least one efficiency stage and a product stage downstream of the at least one efficiency stage, and at least a portion of the paraxylene-rich feedstream is directed to the product stage.

2. The process of claim 1 , wherein at least a portion of the paraxylene-lean feedstream is directed to the at least one crystallization zone.

3. The process of claim 1 , wherein at least one of the paraxylene-rich feedstream and the paraxylene-lean feedstream comprises at least a portion of an effluent downstream of a non-selective source of mixed xylenes.

4. The process of claim 3 , wherein at least one of the paraxylene-rich feedstream and the paraxylene-lean feedstream comprises at least a portion of an effluent downstream of a refinery catalytic reformer.

5. The process of claim 3 , wherein at least one of the paraxylene-rich feedstream and the paraxylene-lean feedstream comprises at least a portion of an effluent downstream of a non-selective toluene disproportionation unit.

6. The process of claim 3 , wherein at least one of the paraxylene-rich feedstream and the paraxylene-lean feedstream comprises at least a portion of an effluent downstream of a non-selective toluene/aromatic C9 plus transalkylation unit.

7. The process of claim 3 , wherein at least one of the paraxylene-rich feedstream and the paraxylene-lean feedstream comprises at least a portion of an effluent downstream of a non-selective aromatic C9 plus transalkylation unit or a non-selective methylation unit.

8. The process of claim 1 , wherein the paraxylene-lean feedstream comprises at least a portion of an effluent downstream of an isomerization zone.

9. The process of claim 1 , wherein the paraxylene-lean feedstream comprises at least a portion of an effluent downstream of a fractionation zone.

10. The process of claim 1 wherein the paraxylene-rich feedstream comprises at least a portion of an effluent downstream of a second paraxylene recovery zone.

11. The process of claim 10 , wherein the second paraxylene recovery zone comprises at least one crystallization zone comprising at least one crystallizer.

12. The process of claim 11 wherein the least one crystallizer of the second paraxylene recovery zone is cooled by a high level refrigerant.

13. The process of claim 10 , wherein the second paraxylene recovery zone comprises at least one crystallization zone and at least one reslurry zone.

14. The process of claim 10 , wherein the second recovery zone comprises at least one selective adsorption zone.

15. The process of claim 1 , wherein the paraxylene-lean feedstream has a ratio of paraxylene to total xylene isomers of 0.4 or less.

16. The process of claim 1 , wherein the paraxylene-lean feedstream has a ratio of paraxylene to total xylene isomers of 0.15 to 0.5.

17. The process of claim 1 , wherein the paraxylene-rich feedstream has a ratio of paraxylene to total xylene isomers of 0.55 or more.

18. The process of claim 1 , wherein the paraxylene-rich feedstream has a ratio of paraxylene to total xylene isomers of 0.70 or more.

19. The process of claim 1 , wherein the paraxylene-rich feedstream has a ratio of paraxylene to total xylene isomers of 0.80 or more.

20. The process of claim 1 , wherein the paraxylene-rich feedstream has a ratio of paraxylene to total xylene isomers of 0.90 or more.

21. The process of claim 1 , wherein the paraxylene containing product stream has a concentration of paraxylene of at least 99.0 wt %.

22. The process of claim 1 , wherein the paraxylene containing product stream has a concentration of paraxylene of at least 99.5 wt %.

23. The process of claim 1 , wherein the paraxylene containing product stream has a concentration of paraxylene of at least 99.7 wt %.

24. The process of claim 1 , wherein at least a portion of the paraxylene-rich feedstream is directed to the at least one reslurry zone.

25. The process of claim 1 , wherein at least a portion of the paraxylene-rich feedstream is cooled prior to its introduction to the product stage.

26. The process of claim 1 , wherein at least a portion of the paraxylene-rich feedstream is cooled by a high level refrigerant.

27. The process of claim 1 , wherein at least a portion of the paraxylene-rich feedstream is directed to the at least one crystallization zone.

28. The process of claim 27 , wherein the at least one crystallization zone comprises at least two stages, and the paraxylene-rich feedstream is directed to a stage other than the first stage.

29. The process of claim 27 , wherein at least a portion of the paraxylene-rich feedstream is cooled prior to its introduction to the at least one crystallization zone with a high level refrigerant.

30. The process of claim 27 , wherein at least a portion of the paraxylene-rich feedstream is cooled prior to its introduction to the at least one crystallization zone with an indirect cooling medium.

31. The process of claim 30 , wherein the indirect cooling medium comprises chilled water, or a chilled glycol solution.

32. The process of claim 30 , wherein the indirect cooling medium comprises propane.

33. The process of claim 30 , wherein the indirect cooling medium comprises propylene.

34. The process of claim 30 , wherein the indirect cooling medium comprises ammonia.

35. The process of claim 12 , wherein the high level refrigerant comprises propane.

36. The process of claim 12 , wherein the high level refrigerant comprises propylene.

37. The process of claim 12 , wherein the high level refrigerant comprises ammonia.

38. The process of claim 1 , wherein at least a portion of the paraxylene-rich feedstream is cooled by chilled water or a chilled glycol solution.

39. The process of claim 26 , wherein the high level refrigerant comprises propane.

40. The process of claim 26 , wherein the high level refrigerant comprises propylene.

41. The process of claim 26 , wherein the high level refrigerant comprises ammonia.

42. The process of claim 29 , wherein the high level refrigerant comprises propane.

43. The process of claim 29 , wherein the high level refrigerant comprises propylene.

44. The process of claim 29 , wherein the high level refrigerant comprises ammonia.

45. The process of claim 1 , wherein the paraxylene-rich feedstream comprises at least a portion of an effluent downstream of a selective source of

Assignees

• Bp Corp North America Inc

Inventors

• Norwood Steven
• Lin Chyau
• Amelse Jeffrey
• Roberts Scott
• Wilsak Richard
• Slusar Brian

Classifications

• C07C7/14 Primary

  by crystallisation; Purification or separation of the crystals · CPC title

• C07C7/12

  by adsorption, i.e. purification or separation of hydrocarbons with the aid of solids, e.g. with ion-exchangers · CPC title

• C07C15/08

  Xylenes · CPC title