Process to control HI concentration in residuum stream

Patent metadata

Field	Value
Publication number	US-9512056-B2
Application number	US-201514724197-A
Country	US
Kind code	B2
Filing date	May 28, 2015
Priority date	Feb 4, 2015
Publication date	Dec 6, 2016
Grant date	Dec 6, 2016

Abstract

A process directed to acetic acid production comprising providing a feed stream comprising methyl iodide, water, acetic acid, methyl acetate, and at least one PRC to a distillation column comprising a distillation zone and a bottom sump zone and distilling the feed stream at a pressure and a temperature sufficient to produce an overhead stream comprising methyl iodide and at least one PRC, and a residuum stream flowing from the bottom sump zone comprising water and greater than or equal to about 0.11 weight percent HI is disclosed herein.

First claim

We claim:

1. A process comprising:
a. directing a methanol-containing feed stream and a carbon monoxide-containing feed stream into a liquid phase reaction medium of a carbonylation reactor in the presence of a catalyst, water, methyl iodide, methyl acetate, acetic acid, an iodide salt, and HI and carbonylating the reaction medium to produce acetic acid;
directing a portion of the reaction medium into a flasher to produce a vapor product stream comprising acetic acid, water, methyl iodide, methyl acetate and at least one PRC, and a non-volatile stream comprising the catalyst and directing the non-volatile stream back into the reaction medium;
b. directing the vapor product stream from the flasher into a first distillation column to produce a first overhead stream comprising methyl iodide, water, acetic acid, methyl acetate, and at least one PRC; and a crude acetic acid stream as a side stream and directing a second column feed stream comprising or derived from the first overhead stream and comprising methyl iodide, water, acetic acid, methyl acetate, and at least one PRC to a second distillation column comprising a distillation zone and a bottom sump zone;
c. distilling the second column feed stream at a pressure and a temperature sufficient to produce a second column overhead stream comprising methyl iodide and at least one PRC, and a second column residuum stream flowing from the bottom sump zone comprising water and greater than or equal to about 0.11 weight percent HI.

2. The process of claim 1 , wherein the second column residuum stream comprises about 0.6 weight percent HI to about 1.2 weight percent HI.

3. The process of claim 1 , wherein an average liquid phase residence time within the distillation zone is about 1 minute to about 60 minutes.

4. The process of claim 3 , wherein the liquid phase comprises a first liquid phase comprising greater than about 50 weight percent water and a second liquid phase comprising greater than about 50 weight percent methyl iodide.

5. The process of claim 4 , wherein the distillation zone comprises a plurality of internal components, each having a component liquid retention volume, wherein an average residence time of the first liquid phase and an average residence time of the second liquid phase in each of the component liquid retention volumes is less than about 30 minutes.

6. The process of claim 5 , wherein the average residence time of the first liquid phase is greater than or equal to the average residence time of the second liquid phase in the component liquid retention volume of at least one of the plurality of internal components.

7. The process of claim 6 , wherein the average residence time of the first liquid phase in the liquid retention volume of at least one of the plurality of internal components is from about 0.1 minutes to about 20 minutes.

8. The process of claim 7 , wherein the average residence time of the second liquid phase in the liquid retention volume of at least one of the plurality of internal components is from about 0.1 minutes to about 20 minutes.

9. The process of claim 1 , further comprising directing a top flush stream comprising water into the distillation zone simultaneous with distilling of the second column feed stream.

10. The process of claim 9 , wherein a mass flow rate of the top flush stream is greater than or equal to about 0.1 percent of the mass flow rate of the second column feed stream.

11. The process of claim 9 , wherein the top flush stream comprises greater than or equal to about 20 weight percent water, a portion of the second column residuum stream, or a combination thereof.

12. The process of claim 1 , further comprising directing a bottom flush stream comprising acetic acid into the distillation zone, the bottom sump zone, or both, simultaneous with distilling of the second column feed stream.

13. The process of claim 12 , wherein the bottom flush stream comprises greater than or equal to about 20 weight percent acetic acid.

14. The process of claim 12 , wherein a mass flow rate of the bottom flush stream is greater than or equal to about 0.1 percent of the mass flow rate of the second column feed stream.

15. The process of claim 1 , wherein the second column overhead stream comprises dimethyl ether.

16. The process of claim 1 , further comprising:
d. extracting at least a portion of the second column overhead stream comprising methyl iodide and at least one PRC with water at a temperature below about 25° C. to produce an aqueous waste stream comprising the at least one PRC, and a raffinate stream comprising methyl iodide; and
e. directing at least a first portion of the raffinate stream back into the second distillation column.

17. The process of claim 16 , wherein the second column residuum stream comprises about 0.6 weight percent HI to about 1.2 weight percent HI.

18. The process of claim 16 , wherein the second column overhead stream comprises dimethyl ether.

19. The process of claim 16 , wherein an average liquid phase residence time within the distillation zone of the second distillation column is about 1 minute to about 60 minutes.

20. The process of claim 16 , further comprising directing a top flush stream comprising water into the distillation zone of the second distillation column simultaneous with distilling of the second column feed stream.

21. The process of claim 20 , wherein a mass flow rate of the top flush stream is greater than or equal to about 0.1 percent of the mass flow rate of the second column feed stream.

22. The process of claim 20 , wherein the top flush stream comprises greater than or equal to about 20 weight percent water, a portion of the second column residuum stream, or a combination thereof.

23. The process of claim 16 , further comprising directing a bottom flush stream comprising acetic acid into the distillation zone and/or the bottom sump zone of the second distillation column simultaneous with distilling of the second column feed stream.

24. The process of claim 23 , wherein the bottom flush stream comprises greater than or equal to about 20 weight percent acetic acid.

25. The process of claim 18 , further comprising:
f. directing a second portion of the raffinate stream comprising methyl iodide and dimethyl ether back into the reaction medium.

26. The process of claim 25 , wherein a mass flow rate of the first portion of the raffinate stream is greater than or equal to a mass flow rate of the second portion of the raffinate stream.

27. The process of claim 16 , wherein the temperature of the second distillation column includes a bottom temperature of about 90° C. to about 130° C., the pressure of the second distillation column is from atmospheric pressure to about 700 kPa above atmospheric pressure, or a combination thereof.

28. A process comprising:
a. directing a methanol-containing feed stream and a carbon monoxide-containing feed stream into a liquid phase reaction medium of a carbonylation reactor in the presence of a catalyst, water, methyl iodide, methyl acetate, acetic acid, an iodide salt, and HI and carbonylating the reaction medium to produce acetic acid;
directing a portion of the reaction medium into a flasher to produce a vapor product stream comprising acetic acid, water, methyl iodide, methyl acetate and at least one PRC, and a non-volatile stream comprising the catalyst and directing the non-volatile strea

Assignees

• Celanese Int Corp

Inventors

• Scates Mark O
• Shaver Ronald David
• Liu Yaw-Haw

Classifications

• C07C51/44 Primary

  by distillation · CPC title

• B01D3/009

  in combination with chemical reactions · CPC title

• C07C53/08

  Acetic acid (pyroligneous acid C10C; preparation of vinegar C12J) · CPC title

• B01D3/34

  with one or more auxiliary substances · CPC title

• B01D3/4283

  Bottom stream · CPC title