Amine-containing absorption medium, process and apparatus for absorption of acidic gases from gas mixtures
CO 2 is absorbed from a gas mixture by contacting the gas mixture with an absorption medium which comprises at least water as solvent and at least one amine of formula (I) where R 1 is an aliphatic radical, having 2 to 6 carbon atoms and at least one amino group, and R 2 is hydrogen, a C 1-4 alkyl radical or a radical R 1 .
1. A process for absorption of an acid gas from a gas mixture, comprising contacting the gas mixture with an absorption medium, wherein said absorption medium comprises at least water as solvent and at least one amine (A) of formula (I):
wherein:
R 1 =aliphatic radical having 2 to 6 carbon atoms and having at least one amino group;
R 2 =hydrogen, a C 1-4 alkyl group or a radical R 1 .
2. The process of claim 1 , wherein said absorption medium comprises at least one amine (A) of formula (II):
wherein:
R 3 =hydrogen or a C 1-4 alkyl group;
R 4 =C 1-4 alkyl group; and
n=2 to 4.
3. The process of claim 2 , wherein R 3 and R 4 =methyl and n=3.
4. The process of claim 1 , wherein said absorption medium further comprises an amine (B) of formula (III):
wherein R 5 =C 1-6 alkyl group.
5. The process of claim 2 , wherein said absorption medium further comprises an amine (B) of formula (III):
wherein R 5 =C 1-6 alkyl group.
6. The process of claim 1 , wherein said absorption medium further comprises a further physical solvent (C).
7. The process of claim 6 , wherein said physical solvent (C) is sulpholane.
8. The process of claim 1 , wherein said absorption medium comprises:
60 to 80% by weight of water and optionally solvent (C);
1 to 40% by weight of the amine (A); and
0 to 39% by weight of an amine (B) of formula (III):
wherein R 5 =C 1-6 alkyl group.
9. The process of claim 8 , wherein said absorption medium comprises 60 to 80% by weight of water and solvent (C).
10. The process of claim 1 , wherein said absorption medium further comprises corrosion inhibitors, activators, wetting-promoting additives and/or defoamers.
11. The process of claim 1 , wherein said gas mixture is natural gas or synthesis gas.
12. The process of claim 1 , wherein the partial pressure of the acid gas is from 0.1 bar to 20 bar.
13. The process claim 1 , wherein said acid gas is absorbed at a temperature of 20 to 60° C.
14. The process of claim 13 , wherein said acid gas is desorbed at a temperature of 60 to 100° C.
15. The process of claim 1 , wherein said acid gas comprises carbon dioxide.
16. The process of claim 1 , wherein the absorption medium, after it has been contacted with the gas mixture, is heated to a temperature at which a phase separation into an aqueous liquid phase and an organic liquid phase occurs.
17. The process of claim 16 , wherein:
a) said acid gas is desorbed from the aqueous liquid phase by reducing the pressure and/or supplying heat;
b) the resulting liquid phase is combined with the organic liquid phase obtained on phase separation; and
c) the combined liquid phases are again, as absorption medium, contacted with the gas mixture.
18. The process of claim 16 , wherein, after the phase separation, acid gas is desorbed from the resulting two-phase mixture by stripping with a gas.
19. An amine-containing absorption medium, comprising:
a) at least water as solvent;
b) at least one amine (A) of formula (I):
wherein:
R 1 =aliphatic radical having 2 to 6 carbon atoms and having at least one amino group; and
R 2 =hydrogen, a C 1-4 alkyl group or a radical R 1 ; and
c) an amine (B) of formula (III)
wherein R 5 =C 1-6 alkyl group.
20. A device for separating off acid gas from a gas mixture, said device comprising an absorption unit, a desorption unit and the circulating absorption medium of claim 19 .