CO
Provided herein are CO 2 -selective membranes that can be used to efficiently separate CO 2 and CO. The membranes can be used to produce high-purity CO 2 and CO gas streams from a feed gas stream comprising a mixture of CO 2 and CO (e.g., an exhaust gas stream from a fuel cell, such as a solid oxide fuel cell). In this way, the membranes can be used with a solid oxide fuel cell system to covert CO 2 to CO.
1. A CO 2 -selective membrane for the separation of CO 2 and CO, the membrane comprising:
a support layer; and
a selective polymer layer disposed on the support layer, the selective polymer layer comprising a hydrophilic polymer matrix and an amine-containing carrier dispersed therein, wherein the amine-containing carrier comprises an amine-containing mobile carrier; and
wherein the CO 2 -selective membrane exhibits a CO 2 : CO selectivity of at least 500 at 100° C. and 2 atm feed pressure; and
wherein the amine-containing mobile carrier comprises a salt formed by reaction of an amine or a base with an amino acid,
wherein the amine is selected from a group consisting of piperazine, 2-(1-piperazinyl) ethylamine, ethylenediamine, diethylenetriamine, triethylenetetramine, tetramethylguanidine, and blends thereof,
wherein the base is selected from a group consisting of KOH, NaOH, LiOH, CsOH, NH 4 OH, and blends thereof; and
wherein the amino acid is selected from a group consisting of sarcosine, glycine, proline, lysine, arginine, histidine, aspartic acid, glutamic acid, serine, threonine, asparagine, glutamine, cysteine, selenocysteine, alanine, valine, isoleucine, leucine, methionine, phenylalanine, tyrosine, tryptophan, pipecolinic acid, N,N-dimethylglycine, and blends thereof.
2. The membrane of claim 1 , wherein the CO 2 -selective membrane exhibits a CO 2 : CO selectivity of at least 100 at 170° C. and 2 atm feed pressure.
3. The membrane of claim 1 , wherein the CO 2 -selective membrane exhibits a CO 2 permeability of at least 1500 Barrer at 100° C. and 2 atm feed pressure.
4. The membrane of claim 1 , wherein the CO 2 -selective membrane exhibits a CO 2 permeability of at least 500 Barrer at 170° C. and 2 atm feed pressure.
5. The membrane of claim 1 , wherein the hydrophilic polymer comprises a polymer selected from the group consisting of polyvinyl alcohol, polyvinyl acetate, polyethylene oxide, polyvinylpyrrolidone, polyacrylamine, a polysiloxane, copolymers thereof, and blends thereof.
6. The membrane of claim 1 , wherein the amine-containing carrier further comprises an amine-containing polymer.
7. The membrane of claim 6 , wherein the amine-containing polymer is selected from the group consisting of polyvinylamine, polyallylamine, polyethyleneimine, poly-N-isopropylallylamine, poly-N-tert-butylallylamine, poly-N-1,2-dimethylpropylallylamine, poly-N-methylallylamine, poly-N,N-dimethylallylamine, poly-2-vinylpiperidine, poly-4-vinylpiperidine, polyaminostyrene, chitosan, copolymers thereof, and blends thereof.
8. The membrane of claim 1 , wherein the amine-containing mobile carrier further comprises a salt defined by a general formula below
wherein R 1 , R 2 , R 3 , and R 4 are hydrogen or hydrocarbon groups having from 1 to 4 carbon atoms, n is an integer ranging from 0 to 4, and A m+ is a cation having a valence of 1 to 3, and m is an integer equal to the valence of the cation.
9. The membrane of claim 1 , wherein the amine-containing mobile carrier further comprises a salt selected from the group consisting of aminoisobutyric acid-potassium salt, aminoisobutyric acid-lithium salt, aminoisobutyric acid-piperazine salt, dimethylglycine-potassium salt, dimethylglycine-lithium salt, dimethylglycine-piperazine salt, piperidine-2-carboxylic acid-potassium salt, piperidine-2-carboxylic acid-lithium salt, piperidine-2-carboxylic acid-piperazine salt, piperidine-4-carboxylic acid-potassium salt, piperidine-4-carboxylic acid-lithium salt, piperidine-4-carboxylic acid-piperazine salt, piperidine-3-carboxylic acid-potassium salt, piperidine-3-carboxylic acid-lithium salt, piperidine-3-carboxylic acid-piperazine salt, and blends thereof.
10. The membrane of claim 1 , wherein the amine-containing mobile carrier comprises a glycinate salt, a sarcosinate salt.
11. The membrane of claim 1 , wherein the selective polymer layer further comprises a cross-linking agent.
12. The membrane of claim 1 , wherein the membrane further comprises a hydrophobic blocking layer disposed on the support layer, disposed between the support layer and the selective polymer layer, disposed on the selective polymer layer, or any combination thereof.
13. The membrane of claim 1 , wherein the membrane is used with a solid oxide fuel cell system to convert CO 2 to CO.
14. A method of separating CO 2 and CO, the method comprising
contacting a membrane defined by claim 1 with a feed gas stream comprising CO 2 and CO under conditions effective to afford transmembrane permeation of the CO 2 .
15. The membrane of claim 1 , wherein the amine-containing mobile carrier comprises a sarcosinate salt.