Process for the purification of ethylene glycol

Patent metadata

Field	Value
Publication number	US-11198664-B2
Application number	US-201816625015-A
Country	US
Kind code	B2
Filing date	Jun 26, 2018
Priority date	Jun 30, 2017
Publication date	Dec 14, 2021
Grant date	Dec 14, 2021

Abstract

The present invention is directed to a process for the purification of ethylene glycol from a crude stream thereof. The process comprises passing the stream of crude ethylene glycol to a first distillation column in which light compounds within the crude stream are separated overhead and a lights-removed crude ethylene glycol stream is removed from at or near the bottom of the first distillation column; passing the lights-removed crude ethylene glycol stream removed from at or near the bottom of the first distillation column to a second distillation column in which purified ethylene glycol is separated and recovered from heavy components present in the lights-removed crude ethylene glycol stream; removing a stream from at or near the bottom of the second distillation column which comprises residual ethylene glycol together with diethylene glycol and heavy compounds and passing said stream to a third distillation column in which the heavy compounds are separated from the stream comprising ethylene glycol and diethylene glycol; and removing the stream comprising ethylene glycol and diethylene glycol from the third distillation column and passing said stream to a fourth distillation column in which the ethylene glycol is separated from the diethylene glycol.

First claim

The invention claimed is:

1. A process for the purification of ethylene glycol from a crude stream thereof, the process comprising:
(a) passing the stream of crude ethylene glycol to a first distillation column in which light compounds within the crude stream are separated overhead and a lights-removed crude ethylene glycol stream is removed from at or near the bottom of the first distillation column;
(b) passing the lights-removed crude ethylene glycol stream removed from at or near the bottom of the first distillation column to a second distillation column in which purified ethylene glycol is separated and recovered from heavy components present in the lights-removed crude ethylene glycol stream;
and,
(c) performing steps (c1) and (c2):
(c1) removing a stream from at or near the bottom of the second distillation column which comprises residual ethylene glycol together with diethylene glycol and heavy compounds and passing said stream to a third distillation column in which the heavy compounds are separated from the stream comprising ethylene glycol and diethylene glycol; and,
(c2) removing the stream comprising ethylene glycol and diethylene glycol from the third distillation column and passing said stream to a fourth distillation column in which the ethylene glycol is separated from the diethylene glycol,

or, performing steps (c3) and (c4):
(c3) removing a stream from at or near the bottom of the second distillation column which comprises residual ethylene glycol together with diethylene glycol and heavy compounds and passing said stream to a third distillation column in which components that are lighter than diethylene glycol are separated in an overhead stream; and,
(c4) removing a stream comprising diethylene glycol from the third distillation column and passing said stream as a feed to a fourth distillation column in which a diethylene glycol stream is separated in a side draw.

2. The process according to claim 1 wherein the crude ethylene glycol stream is first treated in an alkanol distillation column in which water and alkanol will be removed before the crude stream is passed to the first distillation column in step (a).

3. The process according to claim 1 wherein each distillation column is operated a pressure below atmospheric pressure.

4. The process according to claim 2 wherein the alkanol distillation column is operated at a pressure at the column top of about 20 kPa to about 40 kPa or at about 30 kPa.

5. The process according to claim 1 wherein the first distillation column is operated at a pressure at the column top of from about 10 kPa to about 20 kPa or at about 15 kPa.

6. The process according to claim 1 wherein the second distillation column is operated at a pressure of from about 6 kPa to about 10 kPa or at about 8 kPa at the column top.

7. The process according to claim 1 wherein when steps (c1) and (c2) are performed, the third distillation column is operated at a pressure of from about 4 kPa to about 8 kPa or at about 6 kPa at the column top.

8. The process according to claim 1 wherein when steps (el) and (c2) are performed, the fourth distillation column is operated at from about 2 kPa to about 4 kPa or at about 3 kPa at the column top.

9. The process according to claim 1 , wherein when steps (c3) and (c4) are performed, the overhead stream from the third distillation column is recycled to the second distillation column.

10. The process according to claim 9 , wherein a purge is taken from the recycled overhead stream from the third distillation column.

11. The process according to claim 10 , wherein the purge is returned to an upstream hydrogenation to produce ethylene glycol.

12. The process according to claim 1 , wherein when steps (c3) and (c4) are performed, a bottoms stream is recycled from the fourth distillation column to an upstream hydrogenation.

13. The process according to claim 12 , wherein a purge is taken from the bottoms stream to control accumulation of any heavies which are not hydrogenated.

14. The process according to claim 1 , wherein when steps (c3) and (c4) are performed, an overhead stream is withdrawn from the fourth distillation column containing diethylene glycol and any lights that are formed from reactions in the fourth distillation column.

15. The process according to claim 14 , wherein the overhead stream from the fourth distillation column is recycled to the second distillation column.

16. The process according to claim 15 wherein a purge to an upstream hydrogenation is taken from the overhead stream from the fourth distillation column.

17. The process according to claim 14 , wherein the lights comprise monoethylene glycol, water, or both.

Assignees

• Johnson Matthey Davy Technologies Ltd

Inventors

• Jackson Simon
• Snaith Adam Armour
• Tuck Michael William Marshall
• Watson David John
• Wood Michael Anthony

Classifications

• C07C29/80 Primary

  by distillation · CPC title

• C07C31/202

  Ethylene glycol · CPC title

• C07C29/84 Primary

  by extractive distillation · CPC title