Cross-linked polymeric membranes for carbon dioxide separation
A membrane useful in gas separation, the membrane comprising a cross-linked polysiloxane structure having a cross-link density of about 0.1×10 −5 mol/cm 3 to about 6×10 −5 mol/cm 3 , where, in particular embodiments, the cross-linked polysiloxane structure has the following general structure: wherein R 1 , R 2 , R 3 , R 4 , R 5 , and R 6 are independently selected from hydrocarbon groups having at least 1 and up to 6 carbon atoms; A 1 and A 2 are independently selected from cyclic hydrocarbon groups; L 1 and L 2 are linking groups or covalent bonds; n is an integer of at least 1; r and s are independently selected from integers of at least 1; and p is an integer of at least 10. The invention also includes methods for making and using the above-described membranes for gas separation.
1. A membrane useful in gas separation, the membrane comprising a cross-linked polysiloxane structure having a cross-link density of about 0.1×10 −5 mol/cm 3 to no more than 2.5×10 −5 mol/cm 3 .
2. The membrane according to claim 1 , wherein the cross-linked polysiloxane structure has the following general structure:
wherein:
R 1 , R 2 , R 3 , R 4 , R 5 , and R 6 are independently selected from hydrocarbon groups having at least 1 and up to 6 carbon atoms;
A 1 and A 2 are independently selected from cyclic hydrocarbon groups;
L 1 and L 2 are linking groups or covalent bonds;
n is an integer of at least 1;
r and s are independently selected from integers of at least 1; and
p is an integer of at least 10.
3. The membrane according to claim 2 , wherein A 1 and A 2 are cyclopentyl rings.
4. The membrane according to claim 2 , wherein A 1 and A 2 are unsubstituted.
5. The membrane according to claim 2 , wherein at least some of L 1 and L 2 linkers are substituted with a non-acidic heteroatom-containing group containing at least one heteroatom selected from nitrogen, oxygen, and sulfur atoms.
6. The membrane according to claim 5 , wherein said non-acidic heteroatom-containing group contains at least one primary or secondary amine functionality and/or at least one or more hydroxy or ether functionalities.
7. The membrane according to claim 2 , wherein L 1 and L 2 each have at least 2 carbon atoms and are unsaturated.
8. A method for producing a membrane useful in gas separation, the method comprising subjecting a polysiloxane precursor to a cross-linking reaction under conditions that result in a cross-linked polysiloxane structure in the shape of a membrane and having a cross-link density of about 0.1×10 −5 mol/cm 3 to no more than 2.5×10 −5 mol/cm 3 .
9. The method according to claim 8 , wherein the polysiloxane precursor is cross-linked by subjecting the polysiloxane precursor to a hydrosilylation reaction.
10. The method according to claim 8 , wherein the polysiloxane precursor is cross-linked by subjecting the polysiloxane precursor to a peroxide curing reaction.
11. The method according to claim 8 , wherein the polysiloxane precursor is cross-linked by subjecting the polysiloxane precursor to a vinyl addition reaction.
12. The method according to claim 8 , wherein the polysiloxane precursor is cross-linked by subjecting the polysiloxane precursor to a ring opening metathesis polymerization (ROMP) reaction.
13. The method according to claim 12 , wherein said polysiloxane precursor has the following general formula
and said polysiloxane precursor is subjected to a ROMP reaction, wherein D 1 and D 2 are independently selected from bicyclic hydrocarbon groups having at least one accessible carbon-carbon double or triple bond capable of polymerization by said ROMP reaction;
wherein said ROMP reaction results in a cross-linked polysiloxane structure in the shape of a membrane and having the following general formula:
wherein:
R 1 , R 2 , R 3 , R 4 , R 5 , and R 6 are independently selected from hydrocarbon groups having at least 1 and up to 6 carbon atoms;
A 1 and A 2 are independently selected from cyclic hydrocarbon groups;
L 1 and L 2 are independently selected from hydrocarbon linking groups having at least 1 carbon atom;
n is an integer of at least 1;
r and s are independently selected from integers of at least 1; and
p is an integer of at least 10.
14. The method according to claim 13 , wherein D 1 and D 2 are norbornene rings and A 1 and A 2 are cyclopentyl rings.
15. The method according to claim 13 , wherein D 1 and D 2 and A 1 and A 2 are unsubstituted.
16. The method according to claim 13 , wherein the polysiloxane precursor is reacted with unsaturated carbocyclic molecules containing at least one non-acidic heteroatom-containing group containing at least one heteroatom selected from nitrogen, oxygen, and sulfur atoms, to result in a cross-linked polysiloxane structure according to Formula (1) in which a portion of L 1 and L 2 linkers are ring-opened versions of said unsaturated carbocyclic molecules containing said non-acidic heteroatom-containing groups.
17. The method according to claim 16 , wherein said non-acidic heteroatom-containing group contains at least one primary or secondary amine functionality and/or at least one or more hydroxy or ether functionalities.
18. The method according to claim 13 , wherein L 1 and L 2 each have at least 2 carbon atoms and are unsaturated.
19. The method according to claim 13 , wherein said ROMP reaction employs a ruthenium-based Grubbs catalyst.
20. The method according to claim 19 , wherein said Grubbs catalyst is included in the ROMP reaction in a molar ratio of precursor to catalyst of 130:0.5 to 130:10.
21. The method according to claim 19 , wherein said Grubbs catalyst is included in the ROMP reaction in a molar ratio of precursor to catalyst of 130:0.5 to 130:2.5.
22. The method according to claim 19 , wherein said Grubbs catalyst is included in the ROMP reaction in a molar ratio of precursor to catalyst of 130:0.5 to 130:2.
23. A method for at least partially separating carbon dioxide gas from a carbon dioxide-containing mixture of gases, the method comprising passing the carbon dioxide-containing mixture of gases through a membrane comprising a cross-linked polysiloxane structure having a cross-link density of about 0.1×10 −5 mol/cm 3 to no more than 2.5×10 −5 mol/cm 3 , wherein gas exiting the membrane has an increased carbon dioxide concentration relative to the carbon dioxide-containing mixture of gases before being passed through the membrane.
24. The method according to claim 23 , wherein said cross-linked polysiloxane structure has the following general formula:
wherein:
R 1 , R 2 , R 3 , R 4 , R 5 , and R 6 are independently selected from hydrocarbon groups having at least 1 and up to 6 carbon atoms;
A 1 and A 2 are independently selected from cyclic hydrocarbon groups;
L 1 and L 2 are linking groups or covalent bonds;
n is an integer of at least 1;
r and s are independently selected from integers of at least 1; and
p is an integer of at least 10.
25. The method of claim 24 , wherein the carbon dioxide-containing mixture of gases comprises carbon dioxide and nitrogen, and the method achieves a carbon dioxide to nitrogen selectivity of at least 10.
26. The method according to claim 24 , wherein A 1 and A 2 are cyclopentyl rings.
27. The method according to claim 24 , wherein A 1 and A 2 are unsubstituted.
28. The method according to claim 24 , wherein a least some of L 1 and L 2 linkers are substituted with a non-acidic heteroatom-containing group containing at least one heteroatom selected from nitrogen, oxygen, and sulfur atoms.
29. The method according to claim 28 , wherein said non-acidic heteroatom-containing group contains at least one primary or secondary amine functionality and/or at least one or more hydroxy or ether functionalities.
30. The method according to claim 24 , wherein L 1 and L 2 each have at least 2 carbon atoms and are unsaturated.