Guanidine compounds for carbon dioxide capture
A method for removing carbon dioxide from a gaseous source, the method comprising: (i) contacting said gaseous source with an aqueous solution of a carbon dioxide sorbent that reacts with carbon dioxide to form an aqueous-soluble carbonate or bicarbonate salt of said carbon dioxide sorbent; (ii) contacting the aqueous solution from step (i) with a bis-iminoguanidine carbon dioxide complexing compound, which is different from the carbon dioxide sorbent, to result in precipitation of a carbonate or bicarbonate salt of said carbon dioxide complexing compound and regeneration of the carbon dioxide sorbent; and (iii) removing the precipitated carbonate or bicarbonate salt from the aqueous solution in step (ii) to result in a solid form of said carbonate or bicarbonate salt of the carbon dioxide complexing compound. The method may further include a step (iv) of regenerating the carbon dioxide complexing compound by subjecting the precipitated salt to sufficient heat and/or vacuum.
1. A method for removing carbon dioxide from a gaseous source, the method comprising:
(i) contacting said gaseous source with an aqueous solution of a carbon dioxide sorbent that reacts with carbon dioxide to form an aqueous-soluble carbonate or bicarbonate salt of said carbon dioxide sorbent;
(ii) contacting the aqueous solution from step (i) with a carbon dioxide complexing compound, which is different from the carbon dioxide sorbent, after the aqueous-soluble carbonate or bicarbonate salt of said carbon dioxide sorbent is formed in step (i), to result in precipitation of a carbonate or bicarbonate salt of said carbon dioxide complexing compound and regeneration of the carbon dioxide sorbent; and
(iii) removing the precipitated carbonate or bicarbonate salt from the aqueous solution in step (ii) to result in a solid form of said carbonate or bicarbonate salt of the carbon dioxide complexing compound;
wherein said carbon dioxide complexing compound has the following structure:
and wherein said carbonate or bicarbonate salt of said carbon dioxide complexing compound has the following structure:
wherein:
A is a ring-containing moiety or a bond;
one or more of the hydrogen atoms in Formulas (1), (1a), and (1a′) may be replaced with one or more methyl groups;
X m− is a carbonate or bicarbonate anion, with m being 1 for bicarbonate and 2 for carbonate; and
n is 0.5, 1, or 2;
provided that n×m=2 in the case of Formula (1a), and n×m=1 in the case of Formula (1a′).
2. The method of claim 1 , wherein said carbon dioxide sorbent is selected from organoamines, alkali hydroxides, alkali carbonates, and alkaline earth hydroxides.
3. The method of claim 1 , wherein said carbon dioxide sorbent is an organoamine.
4. The method of claim 3 , wherein said organoamine is an amino acid.
5. The method of claim 4 , wherein said amino acid is selected from glycine and N-alkylglycines, wherein alkyl is independently selected from hydrocarbon groups containing 1-6 carbon atoms.
6. The method of claim 1 , further comprising: (iv) regenerating the carbon dioxide complexing compound by subjecting the carbonate or bicarbonate salt of said carbon dioxide complexing compound to heat, vacuum, or both, sufficient to result in release of carbon dioxide gas emanating from said carbonate or bicarbonate salt of said carbon dioxide complexing compound along with simultaneous restoration of the carbon dioxide complexing compound, wherein the released carbon dioxide gas is either quarantined for storage and/or converted into a chemical substance or feedstock.
7. The method of claim 6 , wherein said carbonate or bicarbonate salt of said carbon dioxide complexing compound is heated to a temperature within a range of 30° C.-250° C.
8. The method of claim 6 , wherein said carbonate or bicarbonate salt of said carbon dioxide complexing compound is heated to a temperature within a range of 40° C.-160° C.
9. The method of claim 6 , wherein said heat is provided by a renewable energy source.
10. The method of claim 9 , wherein said renewable energy source is solar energy.
11. The method of claim 10 , wherein said solar energy is a direct solar heat concentrator.
12. The method of claim 1 , wherein said gaseous source is contacted intimately with said aqueous solution of a carbon dioxide sorbent by use of an air-liquid contact facilitator, wherein said air-liquid contact facilitator increases surface area of said aqueous solution to increase the air-liquid contact area between the gaseous source and said aqueous solution.
13. The method of claim 12 , wherein said air-liquid contact facilitator is a humidifying device that contains a reservoir of the aqueous solution containing the carbon dioxide sorbent, and wherein said humidifying device increases the surface area of said aqueous solution by wicking said aqueous solution or forming a mist of said aqueous solution.
14. The method of claim 1 , wherein A is a monocyclic ring.
15. The method of claim 14 , wherein said monocyclic ring is a five-membered, six-membered, or seven-membered ring.
16. The method of claim 1 , wherein A is a carbocyclic ring or ring system.
17. The method of claim 16 , wherein said carbocyclic ring or ring system is unsaturated.
18. The method of claim 17 , wherein A comprises a benzene ring.
19. The method of claim 1 , wherein A is a heterocyclic ring or ring system.
20. The method of claim 19 , wherein said heterocyclic ring or ring system is unsaturated.
21. The method of claim 19 , wherein said heterocyclic ring or ring system contains at least one nitrogen ring atom.
22. The method of claim 19 , wherein A comprises a pyridine ring.
23. The method of claim 1 , wherein A is a bond.