Integrated process for production of alcohol from syngas and removal of CO 2

• US 8,354,257 B2
• Filed: 01/08/2010
• Issued: 01/15/2013
• Est. Priority Date: 01/08/2010
• Status: Expired due to Fees

• Current Assignee: Synata Bio, Inc.
• Original Assignee: Coskata, Inc.
• Inventors: Datta, Rathin, Corley, Ralph
• Primary Examiner(s): Hanley, Susan
• Assistant Examiner(s): NGUYEN, NGHI V
• Application Number:
  US12/684,695
• Publication Number:
  US 20110171706A1
• Time in Patent Office: 1,103 Days
• Field of Search: 435/160, 435/161, 435/170, 435/171
• US Class Current: 435/161
• CPC Class Codes: C12P 7/065 with microorganisms other than yeasts
• CPC Class Codes: C12P 7/16 Butanols
• CPC Class Codes: Y02E 50/10 Biofuels, e.g. bio-diesel
• CPC Class Codes: Y02P 20/10 Process efficiency

Abstract

A process for producing alcohol from syngas integrates the alcohol recovery with the removal of CO₂ from syngas. A syngas feed containing CO, H₂, and CO₂ contacts an aqueous alcohol stream to remove CO₂ from the syngas that then passes to bioreactor containing microorganisms for conversion to alcohol and other liquid products. Flashing of the scrubbing liquid releases the CO₂ and simultaneously concentrates alcohol in the overhead flash vapor. Condensation of the flash vapor provides an enriched alcohol stream for enhanced recovery of the ethanol product in a product separation zone. The remainder of the scrubbing liquid along with make-up alcohol and water from the process gets returned for continued contact with the syngas feed.

Claims

1. A process for the production of alcohol from a feed gas comprising CO₂ and at least one of hydrogen and CO, the process comprising:

a) contacting a feed gas comprising CO₂ and at least one of hydrogen and CO with a first aqueous alcohol stream to absorb CO₂ from the feed gas to produce a contacted stream and separating the contacted stream into a CO₂ reduced feed gas and a CO₂ enriched liquid stream;

b) passing the CO₂ reduced feed gas to a bioreactor for contact therein with microorganisms that convert at least a portion of the hydrogen and CO₂, or CO to a bioreactor effluent stream comprising alcohol;

c) separating the CO₂ enriched liquid stream into a gaseous effluent stream comprising CO₂ and the alcohol and a second aqueous alcohol stream;

d) returning at least a portion of the second aqueous alcohol stream to the first aqueous alcohol stream for contact with the feed gas in step a);

e) recovering alcohol from the bioreactor effluent stream from step b);

f) introducing a portion of the alcohol from the bioreactor effluent stream of step b) into the first aqueous alcohol stream of step a); and

,

g) condensing the gaseous effluent stream from step c) to produce a CO₂ off gas stream and an alcohol enriched stream.

2. The process of claim 1 wherein the bioreactor effluent stream is a liquid comprising at least one of ethanol or butanol.

3. The process of claim 1 wherein the feed gas further comprises H₂S and COS, contact of the feed gas with the first aqueous alcohol stream absorbs CO₂, H₂S and COS, and the gaseous effluent stream further comprises H₂S and COS.

4. The process of claim 1 wherein before step b) the CO₂ reduced feed gas stream from step a) undergoes separation to produce a CO₂ feed off gas stream and a recovered alcohol containing stream and wherein the CO₂ feed off gas stream passes to the bioreactor of step b).

5. The process of claim 1 wherein in step c) a flash zone separates the CO₂ enriched liquid stream into the gaseous effluent stream and the second aqueous alcohol stream and flashing of the CO₂ enriched stream enriches the gaseous effluent stream in alcohol relative to the second aqueous alcohol stream.

6. The process of claim 1 wherein the first aqueous alcohol stream receives make-up alcohol comprising at least a portion of the alcohol enriched stream of step g).

7. The process of claim 1 wherein the first aqueous alcohol stream comprises from 30 to 70 mole % alcohol in water.

8. The process of claim 1 wherein the feed gas contacts the first aqueous alcohol stream at a pressure of from atmospheric to 7 bars g and a temperature of from 25 to 40°

C.

9. The process of claim 4 wherein the CO₂ feed off gas stream passes to an alcohol scrubber for the recovery of alcohol.

10. The process of claim 1 wherein the bioreactor retains microorganisms comprising a mono-culture or a co-culture of any of Clostridium ragsdalei, Butyribacterium methylotrophicum, Clostridium ljungdahli and Clostridium autoethanogenum.

11. The process of claim 10 wherein the bioreactor effluent stream is a liquid comprising ethanol.

12. A process for the production of ethanol from a feed gas comprising CO₂ and at least one of hydrogen and CO, the process comprising:

a) contacting a feed gas comprising CO₂ and at least one of hydrogen and CO with a first aqueous ethanol stream to absorb CO₂ from the feed gas to produce a contacted stream and separating the contacted stream into a CO₂ reduced feed gas and a CO₂ enriched liquid stream;

b) passing the CO₂ reduced feed gas to a bioreactor for contact therein with microorganisms that convert at least a portion of the hydrogen and CO₂, or CO to a bioreactor effluent stream comprising ethanol;

c) separating the CO₂ enriched liquid stream into a CO₂ effluent stream and a second aqueous ethanol stream;

d) recovering ethanol from the CO₂ effluent stream from step c) to produce a CO₂ off-gas stream and an ethanol enriched stream; and

,

e) adding a portion of the bioreactor effluent stream from step b) to the first aqueous ethanol stream to supply make-up ethanol for contact with the feed gas of step a).

13. The process of claim 12 wherein at least a portion of the bioreactor effluent stream from step b) undergoes separation in a rectification zone to provide an ethanol product stream and at least a portion of the ethanol enriched stream from step d) passes directly to the rectification zone.

14. The process of claim 12 wherein in step c) a flash vessel separates the CO₂ enriched stream into the CO₂ effluent stream and the second aqueous ethanol stream and the flash vessel enriches the CO₂ effluent stream in ethanol relative to the second aqueous ethanol stream.

15. The process of claim 12 wherein the CO₂ effluent stream of step c) passes to a condenser and the CO₂ off gas stream and the ethanol enriched stream are recovered from the condenser;

the ethanol enriched stream of step d) passes directly to a rectification zone, and the rectification zone provides make-up ethanol to the first aqueous alcohol stream to supply ethanol for contact with the feed gas of step a).

16. The process of claim 12 wherein the first aqueous ethanol stream comprises from 30 to70 mole % ethanol in water.

17. The process of claim 12 wherein the feed gas further comprises H₂S and COS, contact of the feed gas with the first aqueous ethanol stream absorbs CO₂, H₂S and COS, and theCO₂ off-gas stream further comprises H₂S and COS.

18. A process for the production of ethanol from a feed gas comprising CO₂, H₂, CO, COS and H₂S, the process comprising:

a) passing the feed gas to a contactor;

b) passing a first aqueous ethanol stream to the contactor;

c) absorbing CO₂, COS and H₂S from the feed gas in the contactor to produce a CO₂ reduced feed gas having a reduced concentration of CO₂, H₂S and COS relative to the feed gas and a CO₂ enriched stream containing CO₂, COS and H₂S;

d) passing the CO₂ reduced feed gas to a bioreactor for contact therein with microorganisms that convert at least a portion of the hydrogen and CO₂, or CO to a bioreactor effluent stream comprising ethanol;

e) separating ethanol from the CO₂ enriched stream from step c) in a separator to produce a CO₂ effluent stream comprising ethanol and CO₂ and a second aqueous ethanol stream;

f) condensing ethanol from the CO₂ effluent stream from step e) to produce an ethanol enriched stream and a CO₂ off gas stream containing CO₂, COS and H₂S;

g) passing at least a portion of the bioreactor effluent stream from step d) and the ethanol enriched stream from step f) to an ethanol recovery zone to produce an ethanol effluent stream having an ethanol concentration of at least 90 wt %;

h) passing at least a portion of the second aqueous ethanol stream from step e) to the contactor to supply a portion of the first aqueous ethanol stream to step b);

i) passing make-up ethanol to the contactor to supply a portion of the first aqueous ethanol stream; and

j) recovering an ethanol product stream from the ethanol recovery zone from step g).

19. The process of claim 18 wherein the first ethanol stream comprises from 30 to 70 mole % ethanol.

20. The process of claim 18 wherein the bioreactor produces a tail gas comprising CO₂ and ethanol, the tail gas passes to an ethanol scrubber for the recovery of ethanol, and the CO₂ off-gas stream passes to the ethanol scrubber for the recovery of ethanol.

21. The process of claim 18 wherein microorganisms comprises a mono-culture or a co-culture of any of Clostridium ragsdalei, Butyribacterium methylotrophicum, Clostridium ljungdahli and Clostridium autoethanogenum.

22. The process of claim 18 wherein the CO₂ reduced feed gas from step c) prior to step d) passes to a condenser to produce a recovered ethanol containing stream and at least a portion of the recovered ethanol containing stream and at least a portion of the ethanol enriched stream pass to a rectification column in the ethanol recovery zone and wherein the CO₂ reduced feed gas that is reduced in ethanol passes to the bioreactor of step d).