Process and system for capture of carbon dioxide
A process for absorbing carbon dioxide from a gas stream containing carbon dioxide, including contacting the gas stream with an aqueous composition having a substituted heteroaromatic compound including a six-membered heteroaromatic ring comprising from 1 to 3 nitrogen atoms in the heteroaromatic ring and at least one substituent wherein at least one of the substituents is of formula —R 1 NH 2 wherein R 1 is selected from C 1 to C 6 alkylene and ethers of formula —R 2 —O—R 3 — wherein R 2 and R 3 are C 1 to C 3 alkylene.
1. A process for absorbing carbon dioxide from a gas stream containing carbon dioxide, comprising contacting the gas stream with an absorbent comprising an aqueous composition comprising at least 10 wt % water and a substituted heteroaromatic compound according to formula Ia:
wherein
R 1 is methylene;
R 4 is an optional carbon substituent selected from the group consisting of C 1 to C 4 alkyl, hydroxy, hydroxy-C 1 to C 4 alkyl, C 1 to C 4 alkoxy, C 1 to C 4 alkoxy-(C 1 to C 4 alkyl); and
n is 0, 1 or 2.
2. The process of claim 1 , wherein the substituted heteroaromatic compound is selected from the group consisting of:
2-(aminomethyl)pyridine,
3-(aminomethyl)pyridine and
4-(aminomethyl)pyridine.
3. The process of claim 1 , wherein the substituted heteroaromatic compound is 3-(aminomethyl)pyridine.
4. The process of claim 1 , wherein the concentration of substituted heteroaromatic compound is 1 wt % to 80 wt % of the aqueous composition.
5. The process of claim 1 , wherein the substituted heteroaromatic compound is dissolved in the aqueous solution in an amount of at least 20 wt % of the water content of the aqueous composition.
6. The process of claim 1 , wherein the concentration of the substituted heteroaromatic compound is 10 wt % to 80 wt % of the aqueous composition.
7. The process of claim 1 , wherein the aqueous composition comprises an additional amine selected from tertiary amines, sterically hindered amine and mixture thereof having a pKa greater than that of the substituted heteroaromatic compound.
8. The process of claim 1 , wherein the aqueous composition further comprises a tertiary amine, sterically hindered amine or mixture thereof having a pKa at least 8.85 at 25° C.
9. The process of claim 1 , wherein the aqueous composition further comprises a carbon dioxide absorbent which is selected from the group consisting of Imidazole and N-functionalised imidazole.
10. The process of claim 1 , wherein the aqueous composition comprises the substituted heteroaromatic compound in an amount of 10 wt % to 80 wt % of the aqueous composition and further absorbent wherein the weight ratio of the substituted heteroaromatic compound to further absorbent is from 1:10 to 10:1.
11. The process of claim 1 , wherein the water content of the aqueous composition is at least 15 wt %.
12. The process of claim 1 , wherein the absorbent comprises
10 wt % to 60 wt % of (aminomethyl)pyridine comprising one or more of 2-(aminomethyl)pyridine, 3-(aminomethyl)pyridine and 4-(aminomethyl)pyridine;
10 wt % to 60 wt % of amine selected from tertiary amines and sterically hindered primary and secondary amines and mixtures thereof of pKa at least 8.85; and
20 wt % to 80 wt % water.
13. The process of claim 12 wherein the amine selected from tertiary amines and sterically hindered primary and secondary amines is selected from the group consisting of 2-amino-1-propanol, 2-amino-2-methyl-1-propanol, piperidine, 2-piperidinylmethanol, 3-piperidinylmethanol, 4-piperidinylmethanol, 2-piperidinylethanol, 4-piperidinylethanol, 2-(dimethylamino)ethanol and mixtures of two or more thereof.
14. A composition of absorbed carbon dioxide comprising:
A. an aqueous solvent containing water in an amount of at least 10 wt % of the composition;
B. at least one absorbent compound for carbon dioxide comprising a substituted heteroaromatic compound according to formula Ia
wherein
R 1 is methylene,
R 4 is an optional carbon substituent selected from the group consisting of C 1 to C 4 alkyl, hydroxy, hydroxy-C 1 to C 4 alkyl, C 1 to C 4 alkoxy, C 1 to C 4 alkoxy-(C 1 to C 4 alkyl); and n is 0, 1 or 2; and
C. absorbed carbon dioxide, wherein the absorbed carbon dioxide is at a concentration above the equilibrium concentration when the solution is exposed to air at below the boiling point of the solvent.
15. The composition of claim 14 , wherein the absorbed carbon dioxide constitutes at least 1% absorbed carbon dioxide by weight based on the total weight of the composition.
16. The composition of claim 14 , wherein the substituted heteroaromatic compound is selected from the group consisting of:
2-(aminomethyl)pyridine;
3-(aminomethyl)pyridine; or
4-(aminomethyl)pyridine.
17. A composition claim 14 , wherein, the solution comprises an additional amine selected from the group consisting of tertiary amines, sterically hindered amines and mixtures thereof having a pKa greater than that of the substituted heteroaromatic compound.
18. The composition of claim 14 , wherein the concentration of substituted heteroaromatic compound is 1 wt % to 80 wt % of the aqueous composition.
19. The composition of claim 14 , wherein the absorbent composition comprises
10 wt % to 60 wt % of (aminomethyl)pyridine comprising one or more of 2-(aminomethyl)pyridine, 3-(aminomethyl)pyridine and 4-(aminomethyl)pyridine;
10 wt % to 60 wt % of amine selected from tertiary amines and sterically hindered primary and secondary amines and mixtures thereof of pKa at least 8.85; and
20 wt % to 80 wt % water.
20. The process of claim 1 , wherein the absorbent does not include an ionic liquid.