Liquid carbon dioxide absorbents, methods of using the same, and related systems
A carbon dioxide absorbent composition is described, including (i) a liquid, nonaqueous silicon-based material, functionalized with one or more groups that either reversibly react with CO 2 or have a high-affinity for CO 2 , and (ii) a hydroxy-containing solvent that is capable of dissolving both the silicon-based material and a reaction product of the silicon-based material and CO 2 . The absorbent may be utilized in methods to reduce carbon dioxide in an exhaust gas, and finds particular utility in power plants.
1. A method for reducing the amount of carbon dioxide in a process stream comprising contacting the stream with a carbon dioxide absorbent comprising (i) a liquid, nonaqueous silicon-based material, functionalized with one or more nitrogen atom-containing groups that reversibly react with CO 2 and/or have a high-affinity for CO 2 ; and (ii) a hydroxy-containing solvent that is capable of dissolving both the silicon-based material and a reaction product of the silicon-based material and carbon dioxide.
2. The method of claim 1 , wherein the process stream comprises an exhaust stream.
3. The method of claim 1 , wherein the hydroxy-containing solvent comprises trimethylolpropane ethoxylates, glycerol, ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, 1,3-bis(3-hydroxypropyl)tetramethyldisiloxane, a hydrosilylation reaction product of 1,1,3,3-tetramethyldisiloxane and trimethylolpropane allylether, or combinations of these.
4. The method of claim 1 , wherein the carbon dioxide solvent further comprises water.
5. The method of claim 1 , wherein the functionalized silicon-based material comprises one or more aminosilicones.
6. The method of claim 1 , wherein the functionalized silicon-based material comprises silanes, or compounds containing one or more siloxy units, or combinations of thereof.
7. The method of claim 1 , wherein the functional group(s) comprise(s) one or more aliphatic amines, imines, amidines, amides, heterocyclic amino compounds, aromatic amines, and combinations thereof.
8. The method of claim 1 , wherein the functional group(s) comprise(s) one or more amino hydroxy groups.
9. The method of claim 1 , wherein the solvent has a vapor pressure below about 150 mm Hg at 100° C.
10. The method of claim 1 , wherein the absorbent further comprises antioxidants, stabilizers, accelerators, antifoaming agents or blends thereof.
11. The method of claim 1 , wherein the nitrogen atom-containing functional group is not a sterically hindered amine.
12. The method of claim 1 , wherein the functionalized, silicon-based material comprises less than 20 repeating, monomeric units.
13. The method of claim 12 , wherein the functionalized, silicon-based material comprises 10 or less repeating, monomeric units.
14. The method of claim 1 , wherein the solvent comprises two or more hydroxyl groups.
15. The method of claim 14 , wherein the solvent comprises a glycol, a hydroxylated silicone, a phenol, or combinations of the foregoing.
16. The method of claim 15 , wherein the solvent comprises trimethylolpropane ethoxylates, glycerol, triethylene glycol, tetraethylene glycol, 1,3-bis(3-hydroxypropyl)tetramethyldisiloxane, a hydrosilylation reaction product of 1,1,3,3-tetramethyldisiloxane and trimethylolpropane allyl ether, eugenol, isoeugenol, 2-allyl-6-methylphenol, 2-allylphenol or combinations of the foregoing.
17. The method of claim 1 , wherein the functional group(s) comprise(s) one or more amines.
18. The method of claim 17 , wherein the functional group(s) comprise(s) one or more di-, tri- and polyamines, or combinations of the forgoing.
19. The method of claim 18 , wherein the functional group(s) comprise(s) one or more aminoethylaminopropyl piperazinopropyl, aminomethylaminoethyl, 2-aminopropylpyridyl, groups or combinations of these.