Diamine solvent system for CO
Disclosed herein is a method and system for CO 2 removal from a gas stream using a diamine solvent having a Formula I R 1 (R 2 )N-L 1 -NH—R 3 Formula I. With respect to Formula I, each of R 1 and R 2 independently is aliphatic, cycloaliphatic, or R 1 and R 2 together with the nitrogen to which they are attached, form a heterocyclyl ring; L 1 is aliphatic, cycloaliphatic, or L 1 and R 1 together with the nitrogen to which they are attached form a heterocyclyl ring; and R 3 is aliphatic, cycloaliphatic, cycloalkylalkyl, or alkoxyalkyl. And/or the compound may have a viscosity of less than 75 cP at a CO 2 -loading of 40 mol % and at a temperature of 40° C.
1. A method, comprising:
contacting a gas stream comprising a first amount of CO 2 with a CO 2 -lean solvent stream comprising a compound according to Formula I, to form a treated gas stream comprising a second amount of CO 2 that is less than the first amount, and to form a CO 2 -rich solvent stream; and
heating the CO 2 -rich solvent stream to form a CO 2 stream and regenerate the CO 2 -lean solvent;
wherein the compound according to Formula I has a structure
R 1 (R 2 )N-L 1 -NH—R 3 Formula I
each of R 1 and R 2 independently is aliphatic, cycloaliphatic, or R 1 and R 2 together with the nitrogen to which they are attached, form a heterocyclyl ring;
L 1 is aliphatic, cycloaliphatic, or L 1 and R 1 together with the nitrogen to which they are attached form a heterocyclyl ring; and
R 3 is aliphatic, cycloaliphatic, cycloalkylalkyl, or alkoxyalkyl; and
wherein
the CO 2 -lean solvent stream consists essentially of the compound of Formula I; and
the compound according to Formula I is not
2. The method of claim 1 , wherein the CO 2 -rich solvent comprises less than 10 wt % water.
3. The method of claim 1 , wherein at least one of R 1 and R 2 is branched alkyl or cycloalkyl.
4. The method of claim 1 , wherein R 1 forms a heterocyclyl with L 1 .
5. The method of claim 1 , wherein R 1 and R 2 together with the nitrogen to which they are attached, forms a heterocyclyl ring.
6. The method of claim 1 , wherein at least one of R 1 and R 2 is not linear alkyl.
7. The method of claim 1 , wherein R 3 is alkoxyalkyl.
8. The method of claim 1 , wherein each of R 1 and R 2 independently is C 1-6 alkyl.
9. The method of claim 1 , wherein R 1 and R 2 together with the nitrogen to which they are attached form a 5- or 6-membered heterocyclyl ring.
10. The method of claim 1 , wherein L 1 is C 2-4 alkyl.
11. The method of claim 1 , wherein L 1 and R 1 together with the nitrogen to which they are attached form a 5- or 6-membered heterocyclyl ring.
12. The method of claim 1 , wherein R 3 is branched C 3-6 alkyl, or alkoxyalkyl.
13. The method of claim 1 , wherein the compound is selected from
14. The method of claim 1 , wherein:
the solvent has a vapor pressure of less than 1 Torr at 40° C. and a residual water content of less than 0.1 wt %;
the solvent has a viscosity of less than 75 cP at a CO 2 -loading of 40 mol % and at a temperature of 40° C.; or
a combination thereof.
15. The method of claim 1 , wherein contacting the gas stream with the CO 2 -lean solvent comprises contacting the gas stream at a first temperature of from 30° C. to 80° C.
16. The method of claim 1 , wherein heating the CO 2 -rich solvent comprises heating the CO 2 -rich solvent to a second temperature of 80° C. to 160° C.
17. The method of claim 1 , further comprising cooling the regenerated CO 2 -lean solvent to a temperature of from 30° C. to 60° C.