Methanol Carbonylation System with Multiple Absorber Feed Options

• US 20130096341A1
• Filed: 11/20/2012
• Published: 04/18/2013
• Est. Priority Date: 04/29/2008
• Status: Active Grant

• Current Assignee: Celanese International Corporation (Celanese Corporation)
• Original Assignee: Celanese International Corporation (Celanese Corporation)
• Inventors: Zinoble, Raymond J., Doggett, Tommy W., Liu, Lun-kuang
• Granted Patent: US 9,446,363 B2
• Time in Patent Office: Days
• US Class Current: 562/519
• CPC Class Codes: B01D 2252/2021 Methanol
• CPC Class Codes: B01D 2252/205 Other organic compounds not covered by B01D2252/00 - B01D2252/20494
• CPC Class Codes: B01D 2257/2068 Iodine
• CPC Class Codes: B01D 3/148 in combination with at least one evaporator
• CPC Class Codes: B01D 53/1418 Recovery of products
• CPC Class Codes: B01D 53/18 Absorbing units; Liquid distributors therefor B01D3/16, B01D3/26, B01D3/30 take precedence; packing elements B01J19/30, B01J19/32
• CPC Class Codes: B01D 53/185 Liquid distributors
• CPC Class Codes: B01D 53/77 Liquid phase processes
• CPC Class Codes: B01J 19/24 Stationary reactors without moving elements inside B01J19/08, B01J19/26 take precedence; with stationary particles B01J8/02
• CPC Class Codes: B01J 2208/00796 Details of the reactor or of the particulate material
• CPC Class Codes: B01J 2219/24 Stationary reactors without moving elements inside
• CPC Class Codes: B01J 8/00 Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes
• CPC Class Codes: C07C 51/12 on an oxygen-containing group in organic compounds, e.g. alcohols
• CPC Class Codes: C07C 53/08 Acetic acid pyroligneous acid C10C; preparation of vinegar C12J
• CPC Class Codes: Y02P 20/151 Reduction of greenhouse gas [GHG] emissions, e.g. CO2

Abstract

A methanol carbonylation system 10 includes an absorber tower 75 adapted for receiving a vent gas stream and removing methyl iodide therefrom with a scrubber solvent, the absorber tower being coupled to first and second scrubber solvent sources 16, 56 which are capable of supplying different first and second scrubber solvents. A switching system including valves 90, 92, 94, 96, 98 alternatively provides first or second scrubber solvents to the absorber tower and returns the used solvent and sorbed material to the carbonylation system to accommodate different operating modes.

Claims

1. An apparatus for producing acetic acid comprising:

(a) a reactor for carbonylating methanol or its reactive derivatives, the reactor containing a catalyst selected from rhodium catalysts, iridium catalysts and mixtures thereof, and a methyl iodide promoter in an acetic acid reaction mixture;

(b) a feed system for providing carbon monoxide and methanol or its reactive derivatives to the reactor;

(c) a flash system configured to receive a stream of the reaction mixture and separate it into (i) at least a first liquid recycle stream, and (ii) a crude process stream containing acetic acid;

(d) a first distillation column coupled to the flash system, the first distillation column being adapted to separate low boiling components including methyl iodide from the crude process stream, and generate a purified process stream,

the first distillation column and optionally the reactor and flash system also operating to generate a vent gas stream comprising volatile organic components including methyl iodide;

(e) an absorber tower adapted for receiving the vent gas stream and removing methyl iodide therefrom with a scrubber solvent, the absorber tower also being coupled to first and second scrubber solvent sources which are capable of supplying different first and second scrubber solvents; and

(f) a switching system for alternatively providing first or second scrubber solvents to the absorber tower from either the first scrubber solvent source or the second scrubber solvent source.

2. The apparatus according to claim 1, wherein the first scrubber solvent comprises methanol and the second scrubber solvent consists essentially of acetic acid.

3. The apparatus according to claim 2, wherein the first scrubber solvent consists essentially of methanol.

4. The apparatus according to claim 1, further comprising a chiller coupled to the absorber tower and first and second scrubber solvent sources for cooling the scrubber solvents.

5. The apparatus according to claim 1, wherein a return stream from the absorber tower is selectively coupled to the feed system to the reactor or the first and/or second distillation columns.

6. The apparatus according to claim 1, further including a catalyst reservoir system and wherein a return stream from the absorber tower is selectively coupled to the feed system to the reactor, the first and/or second distillation columns, or the catalyst reservoir system.

7. The apparatus according to claim 1, wherein the feed system includes a methanol surge tank which is connected to the absorber tower as the first scrubber solvent source.

8. The apparatus according to claim 1, further comprising a drying column coupled to said first distillation column adapted for receiving the purified product stream and removing water therefrom.

9. The apparatus according to claim 1, wherein the reactor is vented to the flash system.

10. An improved method of operating an apparatus for making acetic acid of the class including a production system having a reactor containing a reaction medium and a product purification train wherein the production system is vented to an absorber tower, the improvement comprising:

(a) carbonylating methanol or reactive derivatives thereof in the reactor in the presence of a Group VIII metal catalyst and a methyl iodide promoter while maintaining a concentration of water in the reactor of from 1-10% by weight of the reaction medium and concurrently maintaining in the reactor a predetermined partial pressure of carbon monoxide;

(b) venting non-condensables from the production system so as to provide low pressure vent gas only;

(c) feeding the low pressure vent gas from the production system to the absorber tower, the vent gas including methyl iodide and optionally additional volatile components;

(d) supplying a scrubber solvent to the absorber tower, the scrubber solvent comprising methanol, methyl acetate or mixtures thereof;

(e) contacting the low pressure vent gas with the scrubber solvent thereby removing methyl iodide and optionally additional volatile components from the gas and absorbing methyl iodide and optionally additional volatile components into the scrubber solvent; and

(f) feeding an absorber return stream including scrubber solvent and absorbed methyl iodide and optionally additional absorbed volatile components to the reactor.

11. The method according to claim 10, wherein the Group VIII metal catalyst is a supported catalyst.

12. The method according to claim 11, wherein the Group VIII metal catalyst is a supported rhodium catalyst.

13. The method according to claim 12, wherein the rhodium catalyst is supported on a crosslinked polyvinylpyrrolidone polymer.

14. The method according to claim 12, wherein the rhodium catalyst is supported on a crosslinked polyvinylpyridine polymer.