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1. WO2020220064 - PROCESS FOR REGENERATING A LIQUID ABSORBENT

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[ EN ]

Claims

1. A process for regenerating a liquid absorbent, comprising:

contacting the liquid absorbent with a hydrophobic medium, wherein the liquid absorbent comprises at least one amine of Formula (I) and degradation product thereof comprising at least one imine of Formula (II):


wherein each Ar is independently an aromatic group and each R is independently selected from hydrogen, an organyl group and NFI2; and

selectively extracting the degradation product into or through the hydrophobic medium.

2. A process according to claim 1 , wherein the hydrophobic medium is an organic solvent.

3. A process according to claim 2, wherein the organic solvent is selected from the group consisting of aromatic hydrocarbon solvents, oxygen-containing solvents and halogenated solvents.

4. A process according to any one of claims 1 to 3, further comprising separating the liquid absorbent from the hydrophobic medium and recycling the liquid absorbent to a liquid absorbent stream in a gas absorption process.

5. A process according to any one of claims 1 to 4, further comprising converting the extracted degradation product to form at least one regenerated amine of Formula (I)ยท

6. A process according to claim 5, wherein the converting comprises hydrolysing the imine to form a first amount of regenerated amine of Formula (I) and an aldehyde of Formula (III):


7. A process according to claim 6, further comprising separating an aqueous solution comprising the first amount of regenerated amine and an organic solution comprising the aldehyde by liquid-liquid separation.

8. A process according to claim 6 or claim 7, further comprising converting the

aldehyde to form a second amount of regenerated amine of Formula (I) by reductive amination.

9. A process according to claim 8, wherein the reductive amination comprises:

i) reacting the aldehyde with hydroxylamine to form an oxime; and ii) reducing the oxime to form the second amount of regenerated amine.

10. A process according to any one of claims 5 to 9, further comprising recycling the regenerated amine to a liquid absorbent stream in a gas absorption process.

1 1. A process according to any one of claims 1 to 10, wherein the liquid absorbent is an aqueous composition comprising at least 10 wt % water.

12. A process according to any one of claims 1 to 1 1 , wherein the liquid absorbent comprises at least one additional base selected from tertiary amines, hindered amines, carbonate salts, amino acid salts and mixtures thereof having a pKa greater than the amine of Formula (I).

13. A process according to any one of claims 1 to 1 1 , wherein the liquid absorbent comprises at least one aliphatic amine as an absorbent.

14. A process according to claim 13, wherein the aliphatic amine is selected from unhindered primary or secondary amines and alkanolamines.

15. A process according to claim 13 or claim 14, wherein a molar ratio of the aliphatic amine to the combined total of the compounds of Formula (I) and Formula (II) in the liquid absorbent is greater than 2:1.

16. A process according to any one of claims 1 to 15, wherein the liquid absorbent comprises absorbed carbon dioxide.

17. A process according to claim 16, further comprising obtaining the liquid absorbent, for contact with the hydrophobic medium, from a liquid outlet stream of a carbon dioxide absorber column.

18. A process according to claim 16 or claim 17, further comprising returning the liquid absorbent, after extracting the degradation product, to an outlet stream of a carbon dioxide stripping column.

19. A process according to any one of claims 1 to 18, wherein the liquid absorbent comprises the amine of Formula (I) in an amount of in an amount of at least 10 wt%.

20. A process according to any one of claims 1 to 19, wherein the liquid absorbent comprises the imine of Formula (II) in an amount of at least 1 wt% before contact with the hydrophobic medium.

21. A process according to any one of claims 1 to 20, wherein extracting the

degradation product into or through the hydrophobic medium reduces the amount of imine of Formula (II) to less than 0.5 wt% in the liquid absorbent.

22. A process according to any one of claims 1 to 21 , wherein each R is a hydrogen.

23. A process according to any one of claims 1 to 22, wherein each Ar comprises a monocyclic six-membered aromatic group.

24. A process according to claim 23, wherein the monocyclic six-membered aromatic group comprises at least one nitrogen ring atom.

25. A process according to any one of claims 1 to 23, wherein each Ar is selected from the group consisting of 2-pyridyl, 3-pyridyl, 4-pyridyl and phenyl.

26. A process according to any one of claims 1 to 25, wherein the liquid absorbent comprises 3-aminomethylpyridine.

27. A method for absorbing carbon dioxide from a gas stream containing carbon

dioxide, the method comprising:

contacting the gas stream with a liquid absorbent comprising at least one amine of Formula (I), wherein the amine of Formula (I) degrades to form a degradation product comprising at least one imine of Formula (II):


wherein each Ar is independently an aromatic group and each R is independently selected from hydrogen, an organyl group and NFI2; and

regenerating the liquid absorbent by a process according to any one of claims 1 to 26.

28. A method for absorbing carbon dioxide from a gas stream containing carbon

dioxide and dioxygen (O2), the method comprising contacting the gas stream with a liquid absorbent comprising:

i) at least one amine of Formula (I):

ii) at least one aliphatic amine,

wherein the compound of Formula (I) is selectively degraded by the O2 to form a degradation product comprising at least one imine of Formula (II):


wherein, in the amine of Formula (I) and the imine of Formula (II), each Ar is independently an aromatic group and each R is independently selected from hydrogen, an organyl group and NFI2.

29. A method according to claim 28, wherein the aliphatic amine is selected from

unhindered primary or secondary amines and alkanolamines.

30. A method according to claim 28 or claim 29, wherein a molar ratio of the aliphatic amine to the combined total of the compounds of Formula (I) and Formula (II) in the liquid absorbent is greater than 2:1.

31. A method according to any one of claims 28 to 30, further comprising regenerating the liquid absorbent by a process according to any one of claims 1 to 26.