Solvent systems for carbon dioxide capture and methods of making and using said systems
Amine-based solvents, carbon dioxide capture systems, and methods for improving stability of carbamate during carbon dioxide capture are disclosed herein. The amine-based solvents comprise at least one cyclic amine having a first molecular site that is structurally modified to be protonated and a second molecular site that is structurally modified to hold carbon dioxide as carbamate. The carbon dioxide capture systems comprise at least one gaseous stream comprising carbon dioxide and the amine-based solvent in contact with the at least one gaseous stream. The methods for carbon dioxide capture comprise contacting at least one modified cyclic amine to a gaseous stream comprising carbon dioxide such that the modified at least one cyclic amine chemically reacts with carbon dioxide to form a soluble compound.
1 . An amine-based solvent for improving stability of carbamate during carbon dioxide capture, the amine-based solvent comprising:
at least one piperazine having a first molecular site that is structurally modified to be protonated and a second molecular site that is structurally modified to hold carbon dioxide as carbamate, wherein the first molecular site is a protonated site, the second molecular site is a carbamate site, and the at least one piperazine further comprises:
a methyl group present at an alpha position for the protonated site and an alpha position for the carbamate site that is free of a methyl group; or
a methyl group present at 1-position for the protonated site and a nitrogen site for the carbamate that is free of steric hindrance.
2 . The amine-based solvent of claim 1 , wherein the at least one piperazine comprises 2,5-dimethyl-piperazine and the amine-based solvent further comprises morpholine.
3 . The amine-based solvent of claim 2 , wherein a proton from NH 2 +(CH 2 ) 2 of morpholine is moved to the 2,5-dimethyl-piperazine.
4 . The amine-based solvent of claim 3 , wherein the NH(CH 2 ) 2 amino site of the morpholine is configured to hold a carbamate moiety in a mixed solution with the 2,5-dimethyl-piperazine.
5 . A carbon dioxide capture system comprising:
at least one gaseous stream comprising carbon dioxide; and
the amine-based solvent of claim 1 in contact with the at least one gaseous stream.
6 . A method for preparing an amine-based solvent configured to improve stability of carbamate during carbon dioxide capture, the method comprising:
modifying at least one cyclic amine molecule by at least one of an intramolecular site structure modulation and an intermolecular site structure modulation to provide the amine-based solvent such that a first molecular site of the at least one cyclic amine molecule is configured to be protonated and a second molecular site of the at least one cyclic amine molecule is configured to hold carbon dioxide as carbamate, wherein the modification of the at least one cyclic amine further comprises:
adding a methyl group to an alpha position for the first molecular site to be protonated and removing a methyl group from an alpha position for the second molecular site to hold carbon dioxide as carbamate; or
moving a methyl group from an alpha position to a 1-position for the first molecular site to be protonated and removing a steric hindrance on a N site for the second molecular site to hold carbon dioxide as carbamate.
7 . The method of claim 6 , further comprising:
intra-molecularly connecting the first molecular site and the second molecular site in the at least one cyclic amine molecule.
8 . The method of claim 6 , wherein the at least one cyclic amine comprises 2,5-dimethyl-piperazine, morpholine, or a combination thereof.
9 . The method of claim 6 , wherein the at least one cyclic amine comprises 2,5-dimethyl-piperazine, morpholine, piperidine, triethanolamine, or a combination thereof.
10 . A method for carbon dioxide capture, the method comprising:
contacting the modified at least one cyclic amine molecule of claim 6 to a gaseous stream comprising carbon dioxide such that the modified at least one cyclic amine molecule chemically reacts with carbon dioxide to form a soluble compound.
11 . The method of claim 10 , further comprising at least one of:
separating the modified at least one cyclic amine molecule and/or the formed soluble compound from a remaining portion of the gaseous stream;
releasing the remaining portion of the gaseous stream; and
separating the formed soluble compound from the modified at least one cyclic amine molecule.
12 . An amine-based solvent for improving stability of carbamate during carbon dioxide capture, the amine-based solvent comprising:
at least one piperazine having a first molecular site that is structurally modified to be protonated and a second molecular site that is structural modified to hold carbon dioxide as carbamate, wherein the at least one piperazine comprises 2,5-dimethyl-piperazine having a structurally modification such that a methyl group is moved from an alpha position to a 1-position for the first molecular site and a methyl group for the second molecular site is excluded.
13 . The amine-based solvent of claim 12 , wherein the first molecular site is a protonated site and the second molecular site is a carbamate site and the protonated site and the carbamate site are intra-molecularly connected in the same amine molecule of the at least one piperazine.
14 . The amine-based solvent of claim 12 , wherein the amine-based solvent further comprises at least one of morpholine, piperidine, or triethanolamine.