Method and absorption medium for absorbing CO2 from a gas mixture

• US 9,878,285 B2
• Filed: 11/28/2012
• Issued: 01/30/2018
• Est. Priority Date: 01/23/2012
• Status: Active Grant

• Current Assignee: Evonik Operations GmbH (Rag-Stiftung)
• Original Assignee: Evonik Degussa GmbH
• Inventors: Schraven, Alexander, Knaup, Gnter, Schneider, Rolf
• Primary Examiner(s): BERNS, DANIEL J
• Application Number:
  US14/373,350
• Publication Number:
  US 20140356268A1
• Time in Patent Office: 1,889 Days
• Field of Search: None
• CPC Class Codes: B01D 2252/20494 Amino acids, their salts or derivatives
• CPC Class Codes: B01D 2258/0233 from cement factories
• CPC Class Codes: B01D 2258/025 from metallurgy plants
• CPC Class Codes: B01D 2258/0283 Flue gases
• CPC Class Codes: B01D 2258/05 Biogas
• CPC Class Codes: B01D 53/1475 Removing carbon dioxide
• CPC Class Codes: B01D 53/1493 Selection of liquid materials for use as absorbents
• CPC Class Codes: B01D 53/62 Carbon oxides
• CPC Class Codes: C07C 227/18 by reactions involving amino or carboxyl groups, e.g. hydrolysis of esters or amides, by formation of halides, salts or esters
• CPC Class Codes: C07C 229/06 having only one amino and one carboxyl group bound to the carbon skeleton
• CPC Class Codes: C07C 229/12 to carbon atoms of acyclic carbon skeletons
• CPC Class Codes: Y02C 20/40 of CO2
• CPC Class Codes: Y02P 20/151 Reduction of greenhouse gas [GHG] emissions, e.g. CO2

Abstract

The absorption of CO₂ from a gas mixture by contacting the gas mixture with an absorption medium that comprises water and 5 to 50 wt % of amino acid salts of formula R¹R²CHNHCH₂COOK, in which R¹ and R² are n-alkyl radicals and the radicals R¹ and R² together have 2 to 4 carbon atoms, affords a high CO₂ absorption capacity per unit weight in the cyclical operation of absorption and desorption.

Claims

1. An absorption medium for absorbing CO₂ from a gas mixture, comprising water and 5 to 50 wt % of amino acid salts of formula (I):

R¹R²CHNHCH₂COOK 

 

(I)

in which R¹ and R² are n-alkyl radicals, and the radicals R¹ and R² together have 2 to 4 carbon atoms;

which further comprises potassium ions in the form of potassium carbonate or potassium hydrogen carbonate, wherein the molar ratio of potassium ions in the form of potassium carbonate or potassium hydrogen carbonate to amino acid salts of formula I is in the range from 0.01 to 0.1;

and wherein;

more than 90 wt % of the amino acid salts of formula (I) are potassium N-isopropylglycinate.

2. The absorption medium of claim 1, further comprising a corrosion inhibitor, a wetting promoter and/or a defoamer.

3. The absorption medium of claim 1, comprising 10 to 48 wt % of amino acid salts of formula (I).

4. The absorption medium of claim 1, comprising 35 to 45 wt % of amino acid salts of formula (I).

5. The absorption medium of claim 1, comprising more than 40 wt % of water.

6. A process for absorbing CO₂ from a gas mixture by contacting the gas mixture with the absorption medium of claim 1.

7. The process of claim 6, wherein the absorption medium comprises 10 to 48 wt % of amino acid salts of formula (I).

8. The process of claim 6, wherein the absorption medium comprises 35 to 45 wt % of amino acid salts of formula (I).

9. The process of claim 6, wherein the absorption medium comprises at least 40 wt % of water.

10. The process of claim 6, wherein the gas mixture is a combustion off-gas, a natural gas or a biogas.

11. The process of claim 6, wherein CO₂ absorbed in the absorption medium is desorbed again by increasing the temperature, reducing the pressure or both and, after this desorption of CO₂, the absorption medium is used again for absorbing CO₂.

12. The process of claim 11, wherein the absorption is carried out at a temperature in the range from 0 to 80°

C. and the desorption is carried out at a higher temperature in the range from 50 to 200°

C.

13. The process of claim 11, wherein the absorption is carried out at a pressure in the range from 0.8 to 50 bar and the desorption is carried out at a lower pressure in the range from 0.01 to 10 bar.

14. The process of claim 12, wherein the absorption is carried out at a temperature in the range from 20 to 70°

C. and the desorption is carried out at a higher temperature in the range from 80 to 150°

C.

15. The process of claim 12, wherein desorption is at a temperature at least 30°

C. above the temperature during desorption.

16. The process of claim 13, wherein the absorption is carried out at a pressure in the range from 0.9 to 30 bar and the desorption is carried out at a lower pressure in the range from 0.01 to 10 bar.

17. The process of claim 5, wherein the gas mixture further comprises SO₂ and, before absorbing CO₂ from the gas mixture, the SO₂ is depleted using a desulfurization process.

18. The process of claim 6, wherein, before being brought in contact with said absorption medium, the gas mixture has a CO₂ content of 0.1-50% by volume.

19. The process of claim 6, wherein, before being brought in contact with said absorption medium, the gas mixture has a CO₂ content of 8-20% by volume.