POROUS CO-POLYMERIC GEL COMPOSITIONS, POROUS CARBON COMPOSITIONS, AND METHODS FOR SYNTHESIS THEREOF
20220055013 · 2022-02-24
Assignee
Inventors
- Nicholas Leventis (Worcester, MA, US)
- Chariklia Sotiriou-Leventis (Rolla, MT)
- Malik Adnan Saeed (Rolla, MO)
Cpc classification
B01D53/02
PERFORMING OPERATIONS; TRANSPORTING
C08J2205/044
CHEMISTRY; METALLURGY
C08J2205/026
CHEMISTRY; METALLURGY
C08J9/286
CHEMISTRY; METALLURGY
C08J2205/048
CHEMISTRY; METALLURGY
Y02C20/40
GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
C08J2377/00
CHEMISTRY; METALLURGY
B01J13/0091
PERFORMING OPERATIONS; TRANSPORTING
B01J20/3078
PERFORMING OPERATIONS; TRANSPORTING
Y02P20/151
GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
C10L2290/542
CHEMISTRY; METALLURGY
B01J20/3085
PERFORMING OPERATIONS; TRANSPORTING
B01J20/20
PERFORMING OPERATIONS; TRANSPORTING
C08J2379/08
CHEMISTRY; METALLURGY
B01J20/28042
PERFORMING OPERATIONS; TRANSPORTING
C08J2205/05
CHEMISTRY; METALLURGY
International classification
B01J20/20
PERFORMING OPERATIONS; TRANSPORTING
B01D53/02
PERFORMING OPERATIONS; TRANSPORTING
B01J13/00
PERFORMING OPERATIONS; TRANSPORTING
B01J20/28
PERFORMING OPERATIONS; TRANSPORTING
B01J20/30
PERFORMING OPERATIONS; TRANSPORTING
C08G18/34
CHEMISTRY; METALLURGY
C08J9/28
CHEMISTRY; METALLURGY
Abstract
The present invention discloses novel porous polymeric compositions comprising random copolymers of amides, imides, ureas, and carbamic-anhydrides, useful for the synthesis of monolithic bimodal microporous/macroporous carbon aerogels. It also discloses methods for producing said microporous/macroporous carbon aerogels by the reaction of a polyisocyanate compound and a polycarboxylic acid compound, followed by pyrolytic carbonization, and by reactive etching with CO.sub.2 at elevated temperatures. Also disclosed are methods for using the microporous/macroporous carbon aerogels in the selective capture and sequestration of carbon dioxide.
Claims
1. A porous co-polymeric composition comprising gels or aerogels, said composition including at least an amide linkage, an imide linkage and a urea linkage present in any random order.
2-7. (canceled)
8. The composition of claim 1, wherein the composition has the formula (VI): ##STR00014## wherein W1, W2, W3, W4, W5, and W6 represent the same or different linking moieties selected from an amide group, a urea group, an imide group, a carbamic-anhydride group, and/or any combinations thereof; and, n is an integer ranging from 2 to about 500.
9. The composition of claim 8, wherein R1, R2, R3, and R4 are H.
10. (canceled)
11. A porous co-polymeric composition comprising gels and/or aerogels:
-{-[G1-L5-G2]s-[G1-L6-G2].sub.t-[G1-L7-G2]u-}p- (Ib) wherein G1 is a moiety selected from C1-C10 straight chain alkyl or branched alkyl or cycloalkyl, alkylaryl, aryl, heteroalkyl, heterocyclylalkyl, or heteroaryl, each of which is optionally substituted; G2 is a moiety selected from alkyl, cycloalkyl, heteroalkyl, heterocylcoalkyl, alkylaryl, cycloalkylaryl, alkylheteroaryl, cycloalkylheteroaryl, an arene ring system, or a heteroarene ring system, each of which is optionally substituted; L5, L6, and L7 represent one or more linkages selected from any of amide, imide, and urea moieties, present in any random order, and/or any combinations thereof; s, t, and u are integers independently ranging from 0 to 10; and, p is an integer ranging from 1 to about 500.
12. (canceled)
13. The composition of claim 11, wherein the composition has the formula (VII): ##STR00015## wherein R1, R2, R3, and R4 are independently one or more substituents selected from H, alkyl, cycloalkyl, alkoxy, alkylthio, aryl, aryloxy, arylthio, each of which is optionally substituted, and halogen, nitro, or cyano; wherein W7, W8, W9, W10, W11, and W12 represent the same or different linking moieties selected from an amide group, a urea group, an imide group, and/or any combinations thereof; and, wherein n is an integer ranging from 2 to about 500.
14. The composition of claim 13, wherein R1, R2, R3, and R4 are H.
15. A porous carbon composition that comprises monolithic carbon gels and/or aerogels said composition obtained by a process comprising the step of pyrolizing a sample of the co-polymeric composition of claim 1 under an inert atmosphere at about 700° C. to about 1100° C., for a length of time until a constant weight is achieved; wherein the resultant porous carbon composition obtained from the pyrolysis step possesses a nanostructured form in which at least 70% of the surface area measured by the N.sub.2 sorption porosimetry method at 77 K is assigned to micropores; wherein the inert atmosphere is selected from Ar, Na, or He.
16. The porous composition of claim 15, wherein the pyrolysis step is carried out at about 800° C. for a period of about 5 hours.
17. A porous carbon composition that comprises monolithic open-pore carbon gels and/or aerogels, said composition obtained by a process comprising the step of reactive etching of a sample of the composition of claim 15 via pyrolysis under an atmosphere of an etching gas at a temperature ranging from about 900° C. to about 1100° C., for a period ranging from about 2 hours to about 4 hours; wherein the resultant porous carbon composition possesses a nanostructured form in which at least 60% of the surface area measured by the Na sorption porosimetry method at 77 K is assigned to micropores.
18. The porous carbon composition of claim 17, wherein the etching gas is selected from CO.sub.2, O.sub.2, air, or H.sub.2O.
19. The porous carbon composition of claim 17, wherein the etching gas is CO.sub.2.
20. The porous composition of claim 17, wherein the pyrolysis step is carried out at 1000° C. for a period of about 3 hours.
21. A method for separation of CO.sub.2 gas from mixtures of gasses, said method comprising the step of passing the mixtures of gasses through the carbon composition of claim 15.
22. The method of claim 21, wherein the mixture of gasses comprises CH.sub.4, H.sub.2, and/or N.sub.2, in addition to CO.sub.2.
23. A method for pre-combustion purification of fuel gas, said method comprising the step of passing the fuel gas through the carbon composition of claim 15.
24. The method of claim 23, wherein the pre-combustion fuel gas includes H.sub.2 in addition to CO.sub.2.
25. A method for separation of CO.sub.2 gas from mixtures of gasses, said method comprising the step of passing the mixtures of gasses through the carbon composition of claim 17.
26. The method of claim 25, wherein the mixture of gasses comprises CH.sub.4, H.sub.2, and/or N.sub.2, in addition to CO.sub.2.
27. A method for pre-combustion purification of fuel gas, said method comprising the step of passing the fuel gas through the carbon composition of claim 17.
28. The method of claim 27, wherein the pre-combustion fuel gas includes H.sub.2 in addition to CO.sub.2.
29. A porous carbon composition that comprises monolithic carbon gels and/or aerogels said composition obtained by a process comprising the step of pyrolizing a sample of the co-polymeric composition of claim 11 under an inert atmosphere at about 700° C. to about 1100° C., for a length of time until a constant weight is achieved; wherein the resultant porous carbon composition obtained from the pyrolysis step possesses a nanostructured form in which at least 70% of the surface area measured by the N.sub.2 sorption porosimetry method at 77 K is assigned to micropores; wherein the inert atmosphere is selected from Ar, N.sub.2, or He.
30. The porous composition of claim 29, wherein the pyrolysis step is carried out at about 800° C. for a period of about 5 hours.
31. A method for separation of CO.sub.2 gas from mixtures of gasses, said method comprising the step of passing the mixtures of gasses through the carbon composition of claim 29.
32. The method of claim 31, wherein the mixture of gasses comprises CH.sub.4, H.sub.2, and/or N.sub.2, in addition to CO.sub.2
33. A porous carbon composition that comprises monolithic open-pore carbon gels and/or aerogels, said composition obtained by a process comprising the step of reactive etching of a sample of the composition of claim 29 via pyrolysis under an atmosphere of an etching gas at a temperature ranging from about 900° C. to about 1100° C., for a period ranging from about 2 hours to about 4 hours; wherein the resultant porous carbon composition possesses a nanostructured form in which at least 60% of the surface area measured by the Na sorption porosimetry method at 77 K is assigned to micropores.
34. The porous carbon composition of claim 33, wherein the etching gas is selected from CO.sub.2, O.sub.2, air, or H.sub.2O.
35. The porous carbon composition of claim 33, wherein the etching gas is CO.sub.2.
36. The porous composition of claim 33, wherein the pyrolysis step is carried out at 1000° C. for a period of about 3 hours.
37. A method for separation of CO.sub.2 gas from mixtures of gasses, said method comprising the step of passing the mixtures of gasses through the carbon composition of claim 33.
38. The method of claim 37, wherein the mixture of gasses comprises CH.sub.4, H.sub.2, and/or N.sub.2, in addition to CO.sub.2.
39. A method for pre-combustion purification of fuel gas, said method comprising the step of passing the fuel gas through the carbon composition of claim 33.
40. The method of claim 39, wherein the pre-combustion fuel gas includes H.sub.2 in addition to CO.sub.2.
41. A method for pre-combustion purification of fuel gas, said method comprising the step of passing the fuel gas through the carbon composition of claim 29.
42. The method of claim 41, wherein the pre-combustion fuel gas includes H.sub.2 in addition to CO.sub.2.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
[0015]
[0016]
[0017]
[0018]
[0019]
[0020]
[0021]
[0022]
[0023]
[0024]
[0025]
[0026]
[0027]
[0028]
[0029]
[0030]
[0031]
[0032]
DETAILED DESCRIPTION
[0033] Before the present methods, implementations and systems are disclosed and described, it is to be understood that this invention is not limited to specific components, specific methods, specific implementation, or to particular compositions, and as such may, of course, vary. It is also to be understood that the terminology used herein is for the purpose of describing particular implementations only and is not intended to be limiting. Neither are mechanisms which have been provided to assist in understanding the disclosure meant to be limiting.
[0034] One embodiment of the invention provides novel porous co-polymeric compositions comprising gels and/or aerogels, useful as starting materials for porous carbons; these compositions have the general formula (Ia) below:
-{-[G.sub.1-L.sub.1-G.sub.2].sub.x-[G.sub.1-L.sub.2-G.sub.2].sub.y-[G.sub.1-L.sub.3-G.sub.2].sub.z-[G.sub.1-L.sub.4-G.sub.2].sub.w-}.sub.p- (Ia)
wherein:
G.sub.1 is a moiety selected from the following groups: C.sub.1-C.sub.10 straight chain alkyl or branched alkyl or cycloalkyl, alkylaryl, aryl, heteroalkyl, heterocyclylalkyl, heteroaryl, and the like, each of which is optionally substituted;
G.sub.2 is a moiety selected from the following groups: alkyl, cycloalkyl, heteroalkyl, heterocylcoalkyl, alkylaryl, cycloalkylaryl, alkylheteroaryl, cycloalkylheteroaryl, an arene ring system or a heteroarene ring system, and the like, each of which is optionally substituted;
L.sub.1, L.sub.2, L.sub.3, and L.sub.4 represent one or more linkages selected from any of amide, imide, urea, and carbamic-anhydride moieties, present in any random order, and/or any combinations thereof; x, y, z, and w are integers independently ranging from 0 to 10; and,
p is an integer ranging from 1 upwardly to 100, 200, 500, or even higher; preferably; preferably, p is an integer ranging from 1 to about 500.
[0035] In one aspect, compositions (Ia) possess structural attributes of microporosity and macroporosity. In another aspect, compositions (Ia) are monolithic. In another aspect, compositions (Ia) are extensively crosslinked. In another aspect, compositions (Ia) comprise co-polymers of polyamide, polyurea, polyimide, and polycarbamic-anhydride adducts. Stated another way, the copolymeric compositions (Ia) comprise co-(amide, urea, imide, and carbamic anhydride adduct). Thus, these compositions (Ia) include at least one or more of polyamide groups, polyurea groups, polyimide groups, and polycarbamic anhydride groups, or combinations thereof. In one variation of the invention, these compositions include at least two or more of polyamide groups, polyurea groups, polyimide groups, and polycarbamic anhydride groups, or combinations thereof.
[0036] A related embodiment of the invention provides a method for production of the novel compositions (Ia) comprising co-polymeric gels and/or aerogels. This method includes the reaction step of mixing together, at room temperature in a suitable solvent (vide infra), a polyisocyanate compound of the general formula (II) with a polycarboxylic acid compound of the general formula (III) to give the co-polymeric composition comprising gels and/or aerogels of the general formula (Ia), according to the following equation:
##STR00002##
wherein:
G.sub.1 is a moiety selected from the following groups: C.sub.1-C.sub.10 straight chain alkyl or branched alkyl or cycloalkyl, alkylaryl, aryl, heteroalkyl, heterocyclylalkyl, heteroaryl, and the like, each of which is optionally substituted;
G.sub.2 is a moiety selected from the following groups: alkyl, cycloalkyl, heteroalkyl, heterocylcoalkyl, alkylaryl, cycloalkylaryl, alkylheteroaryl, cycloalkylheteroaryl, an arene ring system or a heteroarene ring system, and the like, each of which is optionally substituted;
q=2-6; and,
r=3-8.
[0037] It is to be understood that the reaction step above of a polyisocyanate compound (II) with a polycarboxylic acid compound (III) can optionally include not only one of each, but also a mixture of two or more different polyisocyanate compounds (II) and a mixture of two or more different polycarboxylic acid compounds (III). Importantly, polycarboxylic acid compound (III) must include at least 3 carboxylic acid functional groups, of which at least 2 carboxylic acid functional groups must be positioned relative to each other, both geometrically and stereochemically, in such a manner so as to be able to form an intramolecular anhydride. Thus, illustratively, referring to the following two generic examples below, the two carboxylic acid groups in the top generic example are situated in 1,2-positions relative to each other, allowing them to form a 5-membered anhydride; likewise, the two carboxylic acid groups in the bottom generic example below are situated in 1,3-positions relative to each other, allowing them to form a 6-membered anhydride:
##STR00003##
[0038] The polyisocyanate compound of formula (II) and polycarboxylic acid compound of formula (III) are mixed together in such amounts so that the ratio of isocyanate functional groups to carboxylic acid functional groups is about 1:1. Stated another way, the ratio of NCO:COOH of about 1:1 is the preferred ratio. However, it is understood that, as contemplated herein, other ratios within the range 0.5≤NCO:COOH≤2.0 may be used, which may lead to different, but useful product distributions. A key aspect of this method of the invention, which leads to obtaining the copolymeric composition (Ia) comprising co-(amide, urea, imide, and carbamic anhydride adduct), is that the step of mixing together the polyisocyanate compound (II) with the polycarboxylic acid compound (III) should preferably be carried out without heating, i.e., at room temperature. Also, the step of mixing (II) and (III) is carried out in a suitable solvent, which can be a single solvent or a mixture of solvents. Illustratively, suitable solvents may be ether-type solvents (e.g., tetrahydrofuran (THF)), ester-type solvents (e.g., ethyl acetate (EtOAc)), amide-type solvents, ketone-type solvents, nitrile-type solvents, or mixtures of any of the foregoing solvents, or any other suitable organic solvents or mixtures of solvents that are chemically neutral towards the isocyanate and carboxylic acid reactive groups.
[0039] For the purpose of illustration, the following chemical formulae are provided below as examples of the polyisocyanate compounds (II) of the invention, wherein Ar is a 5-membered or 6-membered arene ring system or heteroarene ring system (it is understood that, as contemplated herein, the benzene rings shown below may be replaced with heteroarene rings as well):
##STR00004##
[0040] Illustrative examples of the 5-membered or 6-membered arene ring systems include, but are not limited to: benzenes; fused arene systems such as naphthalenes, anthracenes, phenanthrenes, and the like; bridged arene systems such as biphenyls, diphenymethanes, benzophenones, triphenylmethanes, and the like; heteroarene analogs of the foregoing; and combinations of the foregoing; all of which may be optionally substituted.
[0041] Also for the purpose of illustration, the following chemical formulae are given below as examples of the polycarboxylic acid compounds (III) of the invention, all of which are either commercially available, or may be readily obtained from the corresponding commercially available cyclic anhydride precursors shown:
##STR00005## ##STR00006##
[0042] It is understood that one of ordinary skill in the chemical arts could readily make or conceive of a nigh-infinite number of modifications to the foregoing illustrative chemical formulae of the polyisocyanate compounds (II) and the polycarboxylic acid compounds (III) that would come within the spirit of the invention, and that it would be impractical to attempt to list herein all such variations of contemplated chemical formulae.
[0043] Another embodiment of the invention provides novel nanoparticulate, porous co-polymeric compositions, comprising gels and/or aerogels, having the general formula (Ib) below:
-{-[G.sub.1-L.sub.5-G.sub.2].sub.s-[G.sub.1-L.sub.6-G.sub.2].sub.t-[G.sub.1-L.sub.7-G.sub.2].sub.u-}.sub.p- (Ib)
wherein G.sub.1 is a moiety selected from C.sub.1-C.sub.10 straight chain alkyl or branched alkyl or cycloalkyl, alkylaryl, aryl, heteroalkyl, heterocyclylalkyl, or heteroaryl, each of which is optionally substituted;
G.sub.2 is a moiety selected from alkyl, cycloalkyl, heteroalkyl, heterocylcoalkyl, alkylaryl, cycloalkylaryl, alkylheteroaryl, cycloalkylheteroaryl, an arene ring system, or a heteroarene ring system, each of which is optionally substituted;
L.sub.5, L.sub.6, and L.sub.7 represent one or more linkages selected from any of amide, imide, and urea moieties, present in any random order, and/or any combinations thereof;
s, t, and u are integers independently ranging from 0 to 10; and,
p is an integer ranging from 1 to about 500.
[0044] Thus, co-polymeric compositions (Ib) comprise co-polymers of polyamide, polyurea, and polyimide. Stated another way, the copolymeric compositions (Ib) comprise co-(amide, urea, and imide). Compositions (Ib) include at least one or more of polyamide groups, polyurea groups, and polyimide groups, and/or any combinations thereof. In one variation of the invention, compositions (Ib) include at least two or more of polyamide groups, polyurea groups, and polyimide groups, and/or combinations thereof.
[0045] A related embodiment of the invention of novel co-polymeric compositions (Ib), which comprise polymeric gels and/or aerogels, is a method for preparation of compositions (Ib). This method includes the reaction step of heating a sample of a co-polymeric composition (Ia) at about 100-200° C., preferably at about 150° C., according to the following equation:
##STR00007##
wherein G.sub.1, G.sub.2, L.sub.1, L.sub.2, L.sub.3, L.sub.4, L.sub.5, L.sub.6, L.sub.7, x, y, z, w, s, t, u, and p are as defined above. This method entails loss of CO.sub.2 from composition (Ia), giving a nanoparticulate composition (Ib), which comprises a co-poly(amide, imide, urea).
[0046] The following is provided for the sake of further illustration. Exemplary of the polyisocyanate compound of the general formula (II) above is a tris(isocyanatoaryl)methane of the formula (IV) below; and illustrative of the polycarboxylic acid compound of general formula (III) above is a 1,2,4,5-benzenetetracarboxylic acid of the formula (V) below; wherein when compounds (IV) and (V) are reacted together at room temperature, a co-polymeric composition (Ia) having the formula (VI) is formed according to the following equation:
##STR00008##
wherein the isocyanate groups of compound (IV) are independently attached to their respective aryl rings at the 2, 3, or 4-positions of the aryl rings;
wherein R1, R2, R3, and R4 are independently one or more substituents selected from H, alkyl, cycloalkyl, alkoxy, alkylthio, aryl, aryloxy, arylthio, each of which is optionally substituted, and halogen, nitro, cyano, and the like;
wherein W.sub.1, W.sub.2, W.sub.3, W.sub.4, W.sub.5, and W.sub.6 represent the same or different linking moieties selected from an amide group, a urea group, an imide group, a carbamic-anhydride group, and/or any combinations thereof; and,
n is an integer ranging from 2 upwardly to 100, 200, 500, or even higher; preferably, n is an integer ranging from 2 to about 500.
[0047] Upon heating of co-polymeric composition (VI) at 100-200° C., preferably at 150° C., CO.sub.2 is lost, and a co-polymeric composition (Ib) having the formula (VII) is obtained:
##STR00009##
wherein R1, R2, R3, R4, and n are the same as defined above; and,
wherein W.sub.7, W.sub.8, W.sub.9, W.sub.10, W.sub.11, and W.sub.12 represent the same or different linking moieties selected from an amide group, a urea group, an imide group, and/or any combinations thereof.
[0048] In another embodiment of the invention, described herein are compositions that comprise monolithic carbon gels and/or aerogels that include both closed and open micropores, and a related process for preparing said compositions. This process comprises the step of pyrolizing a co-polymeric composition (Ib), obtained as described above, at about 700° C. to about 1100° C., and preferably at about 800° C. The pyrolysis step is carried out for a sufficient length of time until a constant weight is achieved. Illustratively, this length of time may be a period ranging from about 3 hours to about 7 hours. An alternative process comprises a one-pot procedure that starts with a co-polymeric composition (Ia), obtained as described above, sequentially heating this composition to about 100-200° C., resulting in loss of CO.sub.2, then raising the temperature further to about 700° C. to about 1100° C. to carry out the pyrolysis step. The resultant porous carbon compositions obtained from the pyrolysis step possess a nanostructured form in which at least 70% of the surface area measured by the N.sub.2 sorption porosimetry method at 77 K is assigned to micropores. Further details of these compositions and the process steps to obtain them are included below and in the Examples section.
[0049] In another embodiment of the invention, described herein are compositions that comprise monolithic open-pore carbon gels and/or aerogels, and a related process for preparing said compositions. The process comprises the step of obtaining a composition comprising a monolithic carbon gel and/or aerogel that includes both closed and open micropores, prepared as described in the preceding paragraph, followed by the step of reactive etching via pyrolysis under an atmosphere of CO.sub.2 at a temperature ranging from about 900° C. to about 1100° C., and preferably at about 1000° C., for a period ranging from about 2 hours to about 4 hours, and preferably for about 3 hours. Besides using CO.sub.2 as the reactive etching agent, other etching agents known in the art may be used as well, such as O.sub.2, air, and H.sub.2O. In one important aspect, the resultant open-pore carbon gels and/or aerogels have an increased micropore surface area, which can be as much as quadruple, or more than quadruple, the micropore surface area prior to reactive etching. The resultant porous carbons possess a nanostructured form in which at least 60% of the surface area measured by the N.sub.2 sorption porosimetry method at 77 K is assigned to micropores.
[0050] In another embodiment of the invention, described herein is a method for selective separation and sequestration of CO.sub.2 gas from mixtures with other gasses. This method comprises the step of passing the mixtures of gasses through the “pre-reactive etching” composition comprising carbon gels and/or aerogels that includes both closed and open micropores, described above and in what follows, or through the “post-reactive etching” composition comprising open-pore carbon gels and/or aerogels, described above and in what follows. Illustratively, the mixture of gasses may include, but is not limited to, CO.sub.2, CH.sub.4, H.sub.2, and N.sub.2. One use of this method may be in the selective separation and sequestration of CO.sub.2 gas especially from post-combustion mixtures of gasses. Another use of this method may be in the pre-combustion purification of fuel gas by selective separation and sequestration of CO.sub.2. Illustratively, the fuel gas being purified may include, but is not limited to, CO.sub.2 and H.sub.2. Further details of this method for selective separation and sequestration of CO.sub.2 gas are described below and in the Examples section.
[0051] Provided in the following are additional embodiments and specific illustrative examples of the invention disclosed herein.
[0052] One embodiment of the invention provides novel compositions comprising microporous co-polymeric materials designed from an integrated systems perspective, and a method for producing these novel compositions in multiscale porous monolithic forms. These novel compositions include designer materials that provide an approach towards CO.sub.2 capture and sequestration (CCS). In one aspect, these compositions comprise carbon gels and/or aerogels that are obtained by pyrolytic conversion of co-polymeric gel and/or aerogel precursors.
[0053] Characteristic of these compositions comprising carbon gels and/or aerogels are added physicochemical stability and dramatically increased microporosity. In one aspect, microporosity is increased dramatically if the backbone of the co-polymeric aerogel precursor consists of a random co-polymer with functional groups that decompose at different temperatures. This is illustrated herein with polymeric aerogels (PA-xx) synthesized via a room-temperature reaction of an aromatic triisocyanate with pyromellitic acid, as is shown in Scheme 1. Using solid-state CPMAS .sup.13C and .sup.15N NMR, it was found that the skeletal framework of PA-xx was a statistical co-polymer of polyamide, polyurea, and polyimide, and also contained the primary condensation intermediate, a carbamic-anhydride adduct. Stepwise pyrolytic decomposition of those components yielded carbon gels and/or aerogels with both open and closed microporosity. The open micropore surface areas of those “as-prepared” carbon aerogels had increased to 340 m.sup.2 g.sup.−1 (from <15 m.sup.2 g.sup.−1 in PA-xx). Based on skeletal density data, it was discovered that reactive etching with CO.sub.2 at high temperatures, e.g., 1000° C., opened access to the closed pores, and the micropore area increased by almost four-fold, up to 1150 m.sup.2 g.sup.−1 (out of 1750 m.sup.2 g.sup.−1 of total Brunauer-Emmett-Teller (BET) surface area). Such compositions comprising carbon gels and/or aerogels demonstrated a good balance of adsorption capacity for CO.sub.2 (up to 4.9 mmol g.sup.−1), and selectivity towards other gasses. The selectivity for CO.sub.2 vs. H.sub.2 (up to 928:1) is suitable for pre-combustion fuel purification. Relevant to post-combustion CCS, the selectivity for CO.sub.2 vs. N.sub.2 was in the 17:1 to 31:1 range. Without being bound by theory, in addition to factors typically considered to explain differential gas sorption (e.g., kinetic diameters, quadrupole moments, and polarizabilities of the adsorbates), it is also suggested here that CO.sub.2 is preferentially engaged by pyridinic and pyridonic N on carbon (identified with XPS) in an energy-neutral surface reaction. Relatively high uptake of CH.sub.4 (2.16 mmol g.sup.−1 at 0° C./1 bar) may be attributed to its high polarizability. Overall, high CO.sub.2 selectivities, in combination with the attractive CO.sub.2 adsorption capacity, low monomer cost, and the innate physicochemical stability of carbon render the compositions disclosed herein as good candidates for practical consideration.
[0054] In one embodiment of the invention, a rigid aromatic polyisocyanate compound may be used, such as, illustratively, the tris(isocyanatoaryl)methane of the formula (IV) below, wherein the isocyanate groups are independently attached to their respective aryl rings at the 2, 3, or 4-positions of the aryl rings, and wherein R1, R2, and R3 are independently one or more substituents selected from H, alkyl, cycloalkyl, alkoxy, alkylthio, aryl, aryloxy, arylthio, each of which is optionally substituted, and halogen, nitro, cyano, and the like:
##STR00010##
[0055] A specific example of polyisocyanate compound (IV) is the readily available compound tris(4-isocyanatophenyl)methane, commonly known as TIPM.
[0056] In another embodiment of the invention, a rigid aromatic polycarboxylic acid compound may be used, such as, illustratively, the benzenetetracarboxylic acid (V) below, wherein R4 is one or more substituents selected from H, alkyl, cycloalkyl, alkoxy, alkylthio, aryl, aryloxy, arylthio, each of which is optionally substituted, and halogen, nitro, cyano, and the like:
##STR00011##
[0057] A specific example of compound (V) is pyromellitic acid (R4=H). Other representative rigid aromatic polycarboxylic acid compounds that may be used are polycarboxylic acids of fused arene systems such as naphthalenes, anthracenes, phenanthrenes, and the like; bridged arene systems such as biphenyls, diphenymethanes, benzophenones, triphenylmethanes, and the like; heteroarene analogs of the foregoing; and combinations of the foregoing. Examples are 1,4,5,8-naphthalenetetracarboxylic acid and 3,3′,4,4′-benzophenonetetracarboxylic acid. However, as stated earlier, the polycarboxylic acids of the invention must include at least 3 carboxylic acid functional groups, of which at least 2 carboxylic acid functional groups must be positioned relative to each other, both geometrically and stereochemically, in such a manner so as to be able to form an intramolecular anhydride.
[0058] Another embodiment of the invention provides a process for preparing a monolithic, nanoparticulate, co-polymeric gel and/or aerogel composition that includes at least one or more of polyamide groups, polyurea groups, polyimide groups, or combinations thereof. In one variation, the process results in a monolithic co-polymeric gel and/or aerogel composition that includes at least two or more of polyamide groups, polyurea groups, polyimide groups, or combinations thereof. This process comprises the step of mixing together at room temperature in a suitable solvent a polyisocyanate compound, as described above, and a polycarboxylic acid compound, as described above, in such amounts so that the ratio of isocyanate functional groups to carboxylic acid functional groups is about 1:1, and subsequently subjecting the product to heating at about 100-200° C.
[0059] In other embodiments of the invention, described herein is a monolithic, nanoparticulate carbon gel and/or aerogel composition that includes both closed and open micropores, and a process for preparing said composition. The process comprises the steps of: (a) mixing together in a suitable solvent at room temperature a polyisocyanate compound, as described above, and a polycarboxylic acid compound, as described above, in such amounts so that the ratio of isocyanate functional groups to carboxylic acid functional groups is about 1:1; (b) heating the resulting product at about 100-200° C., to lose CO.sub.2 and produce a nanoparticulate co-polymeric gel and/or aerogel composition that includes one or more of polyamide groups, polyurea groups, polyimide groups, and/or combinations thereof; and, (c) subjecting the product obtained in (b) to pyrolysis under an inert atmosphere at a temperature ranging from about 700° C. to about 1100° C., for a sufficient length of time until a constant weight is achieved; illustratively, this may be a period ranging from about 3 hours to about 7 hours.
[0060] In other embodiments of the invention, described herein is a monolithic, nanoparticulate, open-pore carbon gel and/or aerogel composition, and a process for preparing the same. The process comprises the steps of obtaining a monolithic carbon aerogel that includes both closed and open micropores as described in the preceding paragraph, followed by the step of reactive etching via pyrolysis under an atmosphere of CO.sub.2, or O.sub.2, or air, or H.sub.2O, preferably CO.sub.2, at a temperature ranging from about 900° C. to about 1100° C., for a period ranging from about 2 hours to about 4 hours, resulting in the open-pore carbon gel and/or aerogel composition. In one aspect, this composition has an increased micropore surface area. The increased micropore surface area can be as much as quadruple, or more than quadruple, the micropore surface area prior to reactive etching.
[0061] In another embodiment of the invention, described herein is a method for selective separation and sequestration of CO.sub.2 gas from mixtures with other gasses. This method comprises the step of passing the mixtures of gasses through the “pre-reactive etching” carbon gel and/or aerogel composition of the invention, or through the “post-reactive etching” open-pore carbon gel and/or aerogel composition of the invention. One use of this method may be in the selective separation and sequestration of CO.sub.2 gas especially from post-combustion mixtures of gasses. Another use of this method may be in the pre-combustion purification of fuel gas by selective separation and sequestration of CO.sub.2.
[0062] While the novel technology herein has been illustrated and described in detail in the foregoing description, and in the following examples and the figures herein, the same is to be considered as illustrative and not restrictive in character. It is understood that one of ordinary skill in the art could readily make a nigh-infinite number of insubstantial changes and modifications to the above-described embodiments and that it would be impractical to attempt to describe all such embodiment variations in the present specification. Accordingly, it is understood that all changes and modifications that come within the spirit of the novel technology are desired to be protected.
Examples
[0063] The following examples further illustrate specific embodiments of the invention. However, the following examples should not be interpreted in any way to limit the invention.
[0064] EXAMPLE 1. Synthesis of polymeric aerogels from TIPM and PMA. Materials design was based on the well-known reaction of isocyanates with carboxylic acids to provide amides. That reaction has been utilized for the synthesis of polyamide aerogels from TIPM and trimesic acid (see, Leventis, N. et al., J. Mater. Chem., 2011, 21:11981-11986), and more recently from TIPM and ferrocene dicarboxylic acid (see, Saeed, A. M., et al., Chem. Mater., 2016, 28:4867-4877). That reaction was implemented herein with PMA.
TABLE-US-00001 TABLE 1 Formulations and gelation times of PA-xx aerogels. PMA Desmodur RE TIPM THF mass volume .sup.a C volume mass .sup.b mass .sup.c C mass volume gelation Sample (g) (mL) mmol (M) (m1-) (g) (g) mmol (M) (g) (mL) time .sup.d PA-2.5 0.190 0.116 0.75 0.030 1.330 1.359 0.367 1.00 0.040 20.7 23.3 ~4 h PA-5 0.190 0.116 0.75 0.061 1.330 1.359 0.367 1.00 0.081 9.59 10.8 3 h 15 min PA-10 0.190 0.116 0.75 0.125 1.330 1.359 0.367 1.00 0.167 4.02 4.52 2 h 10 min PA-15 0.190 0.116 0.75 0.193 1.330 1.359 0.367 1.00 0.257 2.16 2.43 1 h 30 min PA-20 0.190 0.116 0.75 0.264 1.330 1.359 0.365 1.00 0.352 1.23 1.39 45 min PA-25 0.190 0.116 0.75 0.339 1.330 1.359 0.367 1.00 0.453 0.67 0.76 15 min .sup.aThe volume of PMA was calculated based on its density measured with helium pycnometry (1.642 g cm.sup.−3) .sup.bThe mass of commercial Desmodur RE was calculated based on its density as measured in Applicants' laboratory (1.022 g cm.sup.−3). .sup.cThe mass of TIPM in Desmodur RE was calculated based on the 27% w/w concentration given by the manufacturer. .sup.dAll gelation times, except for PA-2.5, are at room temperature. PA-2.5 gelled at 60° C.
[0065] EXAMPLE 2. Characterization of polymeric aerogels: General material properties and the porous structure of PA-xx. PA-xx shrunk during drying, in reverse order relative to the solution concentration (
TABLE-US-00002 TABLE 2 Characterization of the PA-xx aerogels. Π specific BET sur- average pore linear bulk Skeletal (% pore volume face area, diameter (nm) particle shrinkage density, p density, p
v/v) (cm
g
)
(m
4V
BJH.sup.J (nm) radius xx (%)
(g cm
)
(g cm
)
V
V
V
g
)
method method r.sup.k R.sub.1
R.sub.2.sup.m 5 35.39 ± 0.95 0.139 ± 0.008 1.316 ± 0.073 89 6.43 0.504 5.93 176 (15) 146 [10] 31 [52] 13 10.16 ± 0.55 54.95 ± 4.09 10 20.88 ± 0.33 0.169 ± 0.003 1.306 ± 0.008 87 5.15 0.456 4.70 163 (17) 126 [12] 27 [47] 14 9.74 ± 0.54 50.37 ± 3.11 15 17.21 ± 0.26 0.246 ± 0.010 1.307 ± 0.004 81 3.30 0.468 2.83 143 (14) 92 [14] 36 [66] 16 10.85 ± 0.55 50.98 ± 1.91 20 13.73 ± 1.08 0.285 ± 0.007 1.319 ± 0.004 78 2.75 0.295 2.46 91 (11) 121 [13] 38 [68] 25 10.31 ± 1.09 43.57 ± 1.98 25 12.90 ± 0.46 0.330 ± 0.008 1.321 ± 0.002 75 2.27 0.117 2.16 46 (6) 198 [10] 36 [65] 49 12.7 ± 0.92 48.45 ± 2.26 .sup.aAverage of 3 samples. .sup.bLinear shrinkage = 100 × (mold diameter − sample diameter)/(mold diameter). .sup.cSingle sample, average of 50 measurements. .sup.dPorosity, Π = 100 × (p.sub.s − p.sub.b)/p.sub.s. .sup.eCalculated via V.sub.Tota1 = (1/p.sub.b) − (1/p.sub.s). .sup.fCumulative volume of pores between 1.7 nm and 300 nm from N.sub.2-sorption data and the BJH desorption method. .sup.gV.sub.>300 nm = V.sub.Total − V.sub.1.7 − 300 nm. .sup.hNumbers in (parentheses): micropore surface areas were calculated via t-plot analysis using the Harkins and Jura model. .sup.iFor the first number, V was taken equal to V.sub.Total = (1/p.sub.b) − (1/p.sub.s); for the number in [brackets], V was set equal to the maximum volume of N.sub.2 absorbed along the isotherm as P/Po.fwdarw.1.0. .sup.jFrom the BJH plots: first numbers are peak maxima; numbers in (parentheses) are full widths at half maxima .sup.kParticle radius, r = 3/(p.sub.s × σ); .sup.lR1: radius of primary particles from SAXS; .sup.mR2: radius of secondary particles from SAXS.
indicates data missing or illegible when filed
[0066] EXAMPLE 3. Characterization of polymeric aerogels (cont.): The skeletal framework of PA-xx. According to scanning electron microscopy (SEM—
TABLE-US-00003 TABLE 3 SAXS data obtained by fitting the scattering profiles of FIG. 3 using the Beaucage Unified Model.sup.S.R-1 Primary particles Secondary Particles Sample R (I)
R
R
(II)
R
xx high-Q slope
(nm) (nm) low-Q slope
(nm) (nm) PA-xx 5 −4.05 ± 0.02 7.82 ± 0.42 10.16 ± 0.55 −3.51 ± 0.09 42.31 ± 3.15 54.95 ± 4.09 10 −4.23 ± 0.02 7.50 ± 0.41 9.74 ± 0.54 −3.69 ± 0.16 38.79 ± 2.40 50.37 ± 3.11 15 −4.00 ± 0.02 8.35 ± 0.42 10.85 ± 0.55 −3.72 ± 0.11 39.26 ± 1.47 50.98 ± 1.91 20 −4.25 ± 0.05 7.94 ± 0.84 10.31 ± 1.09 −3.96 ± 0.29 33.55 ± 1.53 43.57 ± 1.98 25 −4.22 ± 0.05 9.37 ± 0.71 12.17 ± 0.92 −4.13 ± 0.30 37.31 ± 1.74 48.45 ± 2.26 C-xx
5 −4.20 ± 0.01 27.94 ± 1.16 36.28 ± 0.21 — — — 10 −4.21 ± 0.01 24.19 ± 0.11 31.42 ± 0.14 — — — 15 −4.21 ± 0.01 25.37 ± 0.18 32.95 ± 0.23 — — — 20 −4.21 ± 0.01 24.74 ± 0.15 32.13 ± 0.19 — — 25 −4.20 ± 0.01 29.11 ± 0.14 37.80 ± 0.18 — — — S.R-1 (a) Beaucage, G. J. Appl. Crystallogr. 1995, 28, 717-728. (b) Beaucage, G. J. Appl. Crystallogr. 1996, 29, 134-146. Referring to FIG. 3: .sup.aFrom power-lawRegionI. Slopes <−4.00, signify primary particles with density-gradient boundaries. .sup.bRadius of gyration of primary particles, R.sub.G(I), from Region II (first Guinier knee). .sup.cPrimary particle radii R.sub.1 = (R.sub.G(I)/0.77). .sup.dFrom power-law Region III. All slopes <−3, meaning surface fractal secondary particles; surface fractal dimension, D.sub.s = 6-|slope|. .sup.eRadius of gyration of secondary particles, R.sub.G(II), from Region IV (second Guinier knee). .sup.fSecondary particle radii, R.sub.2 = (R.sub.G(II)/0.77). .sup.gWithin the accessible range of Q,scattering profiles of C-xx aerogels could be fitted only with a high-Q power law and one Guinier knee.
indicates data missing or illegible when filed
[0067] EXAMPLE 4. Characterization of polymeric aerogels (cont.): The chemical make-up of PA-xx. The chemical makeup of PA-xx was probed mainly with solid-state CPMAS .sup.13C and .sup.15N NMR. All solid-state .sup.13C NMR spectra of PA-xx are shown in
##STR00012## ##STR00013##
[0068] In solid-state .sup.15N NMR (
[0069] Specifically, it is speculated that the reaction sequence leading to urea and imide is initiated by an intramolecular acid-base neutralization within the carbamic-anhydride adduct toward its zwitterionic form, which in turn would then expel CO.sub.2, and yield free aromatic amine and pyromellitic anhydride (Eq 3). Both of those products are known to be highly reactive towards —N═C═O. Thus, newly formed free dangling —NH.sub.2 may react either with yet-unreacted isocyanate to give urea (Eq 4), or with newly formed anhydride to give imide (Eq 5). The latter reaction is known to proceed via an amic acid intermediate (see Eq 5) that, in a typical imide synthesis, requires a sacrificial dehydrating agent (usually acetic anhydride/pyridine). It is thus believed that the role of that dehydrating agent is played here by the isocyanate. As mentioned above, alternatively, polyimide may also be formed via reaction of anhydride groups with isocyanate via a 7-member intermediate that expels CO.sub.2 (Eq 6).
[0070] The obtained data may be taken as showing that PA-xx are mixtures of three main components: polyamide, polyimide and polyurea. The fact that the .sup.15N NMR resonances of polyimide and polyurea in PA-xx were near, but not exactly at the resonances of the homopolymers synthesized independently, may be taken as evidence that PA-xx was a random copolymer of the three components rather than a polymer blend. Furthermore, although .sup.15N NMR data may not be exactly quantitative, it is noticeable that the resonance at 102.3 ppm was disproportionally intense. Along those lines, heating of any as-prepared PA-xx sample to 150° C.: (a) liberates CO.sub.2 (the chemical identity of the evolving gas was confirmed with mass spectrometry); (b) decreases the intensity of the .sup.15N NMR resonance at 102.3 ppm and moves it closer to the resonance of polyurea (new position at 104.5 ppm vs. 105.3 ppm for the homopolymer); and, (c) increases the relative intensity of the amide resonance. (The post-heating .sup.15N NMR spectrum of PA-xx is included in
[0071] EXAMPLE 5. Pyrolysis of PA-xx aerogels to carbons and reactive etching with CO.sub.2. Preparation of C-xx and EC-xx carbon aerogels.
[0072] EXAMPLE 6. Chemical composition of C-xx and EC-xx aerogels. The carbonization yield of PA-xx to C-xx varied in the range of 42-57% w/w. Reactive etching removed less mass than carbonization: yields from C-xx to EC-xx were in the range of 65-78% w/w. CHN analysis of middle-density PA-15 gave (% w/w): C, 62.91; H, 4.40, and N, 7.93. After pyrolysis, C-15 consisted of: C, 85.95%, H, 1.54%; N, 5.44%. After etching, EC-15 consisted of: C, 80.92%, H, 1.18%; N, 5.61%. Considering those CHN analysis data together with the particular carbonization yield of PA-15 (47.82±0.63%), and the etching yield of C-15 (75.11±2.22%), it was calculated that C-15 retained (w/w) 65% of the C, and 33% of the N in the parent PA-15. By the same token, EC-15 retained (w/w) 71% of the C, and 77% of the N present in C-15. Overall, EC-15 retained 25% w/w of the N initially present in PA-15.
[0073] Because of the potential importance of N for sequestration of CO.sub.2 (see, Wang, M.; et al., RSC Adv. 2014, 4:61456-61464; and, Zhong, M.; et al., J. Am. Chem. Soc. 2012, 134:14846-14857), the chemical environment of N in C-xx and EC-xx was probed with XPS. The high-resolution spectra of the N1s peak in C-25 and EC-25 are shown in
[0074] EXAMPLE 7. General material properties and the nanostructure of C-xx and EC-xx aerogels. Microscopically, C-xx and EC-xx looked similar to one another (
[0075] According to the photographs of
TABLE-US-00004 TABLE 4 Characterization of carbon (C-xx) and etched-carbon (EC-xx) aerogels. Π specific pore volume BET sur- average pore micropore particle linear bulk skeletal (% (cm g
) face area, diameter (nm) width (nm)
radius shrinkage density,
density,
v/v) V
(m
4V
BJH cylindrical (nm) xx (%)
(g cm
)
(g cm
)
V
V
N.sub.2 CO.sub.2 g
)
method method slit
Carbon Aerogels (C-xx) 5 63.71 ± 0.28 0.322 ± 0.025 2.033 ± 0.021 84 2.614 0.090 0.130 0.134 429 (337) 24 [2.7] 29 [-] 0.580 0.347 3.44 10 54.92 ± 0.26 0.367 ± 0.006 2.030 ± 0.019 82 2.232 0.078 0.102 0.122 380 (291) 24 [2.8] 28 [17] 0.608 0.365 3.89 15 47.82 ± 0.63 0.404 ± 0.018 1.956 ± 0.017 79 1.964 0.070 0.155 0.125 353 (270) 22 [2.8] 32 [21] 0.577 0.342 4.34 20 43.93 ± 0.10 0.422 ± 0.008 1.954 ± 0.021 78 1.858 0.056 0.192 0.119 365 (301) 20 [2.7] 35 [24] 0.708 0.426 4.21 25 39.80 ± 0.28 0.451 ± 0.013 1.870 ± 0.025 76 1.683 0.068 0.255 0.126 302 (230) 22 [3.0] 36 [26] 0.669 0.403 5.31 Etched Carbon Aerogels (EC-xx) 5 83.60 ± 0.16 0.919 ± 0.037 1.763 ± 0.235 48 0.521 0.010 0.408 0.191 793 (741) 2.6 [2.1] 22 [13] 0.703 0.423 2.15 10 60.69 ± 0.36 0.284 ± 0.011 2.143 ± 0.126 87 3.054 0.127 0.414 0.189 1561 (1148) 7.8 [2.3] 27 [11] 0.698 0.420 0.90 15 59.81 ± 0.27 0.279 ± 0.007 2.169 ± 0.090 87 3.123 0.123 0.454 0.191 1556 (1130) 8.0 [2.3] 26 [9] 0.689 0.415 0.89 20 52.43 ± 0.23 0.255 ± 0.006 2.325 ± 0.123 89 3.491 0.120 0.439 0.190 1742 (1140) 8.0 [2.3] 28 [10] 0.654 0.394 0.74 25 45.12 ± 0.19 0.247 ± 0.001 2.246 ± 0.034 89 3.603 0.101 0.371 0.190 1394 (1122) 10 [2.8] 33 [11] 0.636 0.383 0.96 .sup.aAverage of 3 samples. .sup.bLinear shrinkage = 100 × (mold diameter − sample diameter)/(mold diameter). .sup.cSingle sample, average of 50 measurements. .sup.dPorosity, □ = 100 × (p.sub.s − p.sub.b/p.sub.s. .sup.eCalculated via V.sub.Tota1 = (l/p.sub.b) − (1/p.sub.s). .sup.fCumulative volume of pores between 1.7 nm and 300 nm from N.sub.2-sorption data and the BJH desorption method. .sup.gV.sub.micropre was calculated either with N.sub.2-sorption using low-pressure data at 77 K, or with CO.sub.2-sorption up to 760 ton (relative pressure of 0.03) at 273 K. (For comparison, t-plot micropore volumes derived from medium-pressure N.sub.2-sorption data at 77 K were as follows (running down the respective columns) for C-xx: 0.173; 0.150; 0.139; 0.155; 0.118. For EC-xx: 0.389; 0.592; 0.583; 0.591; 0.578.) .sup.hNumbers in (parentheses): micropore surface areas calculated via t-plot analysis using the Harkins and Jura model. .sup.iFor the first number, V was taken equal to V.sub.Total = (1/p.sub.b) −(1/p.sub.s); for the number in [brackets], V was set equal to the maximum volume of N.sub.2 absorbed along the isotherm as P/P.fwdarw.1.0. .sup.jFrom the BJH plots: first numbers are peak maxima; numbers in (parentheses) are full widths at half maxima .sup.kBy applying the Horvath-Kawazoe method on N.sub.2-sorption data under low-pressure dosing (P/Po ≤ 0.1). First column, assuming cylindrical pores; second column, assuming slit pores. .sup.lParticle radius, r = 3/(p.sub.s × σ).
indicates data missing or illegible when filed
[0076] EXAMPLE 8. The pore structure of C-xx and EC-xx aerogels. Overall, C-xx had pairwise about equal percent porosities to their parent PA-xx (compare data in Tables 2 and 4), descending from 84/89% v/v (C-5/PA-5) to 76/75% v/v (C-25/PA-25). That trend suggests that, closed pores notwithstanding, pyrolytic mass loss and shrinkage nearly compensated one another. On the other hand, with the exception of EC-5, which underwent excessive shrinkage (
[0077] The first profound effect of microporosity was on surface areas (Table 4). The BET surface area of C-xx was in the 300-400 m.sup.2 g.sup.−1 range (versus 50-170 m.sup.2 g.sup.−1 of the parent PA-xx; Table 2). A high portion of the surface area of C-xx (76-78% or 230-340 m.sup.2 g.sup.−1) was allocated (via t-plot analysis and the Harkins and Jura model) to micropores. After etching, the BET surface area of CE-xx (10≤xx≤25) was catapulted into the 1400-1750 m.sup.2 g.sup.−1 range, with 65-80% of that area (1120-1150 m.sup.2 g.sup.−1) attributed to micropores.
[0078] A quantitative evaluation of the micropore volume was carried out by considering three independent sets of data: (a) the low-pressure N.sub.2-sorption isotherms at 77 K (
[0079] Irrespective of the method mentioned in the previous paragraph, micropore volumes of EC-xx were always higher than those of C-xx. Methods (a) and (b) served as an internal cross-check of the micropore volumes calculated via N.sub.2-sorption. Thus, methods (a) and (b) gave micropore volumes within 12.5% of one another for C-xx, and within 31% for EC-xx. Next, in the case of C-xx, micropore volumes via CO.sub.2 adsorption were 34.4% lower than those obtained via N.sub.2 sorption. However, in the case of EC-xx, micropore volumes via CO.sub.2 adsorption were less than half of those obtained via N.sub.2-sorption. Therefore, although it can be claimed that in the case of C-xx the V.sub.micropore,N2 and V.sub.micropore,CO2 were within error from one another, in the case of EC-xx it is safe to conclude that CO.sub.2 did not fill its entire micropore volume (this may be a valid comparison given that the van der Waals radii of CO.sub.2 and N.sub.2 are similar: 1.57 Å vs. 1.55 Å, respectively); yet the micropore volume of EC-xx, as reflected by CO.sub.2 porosimetry, was still 1.52× higher than that of C-xx (note: all volumetric comparisons in this paragraph concern average values over all xx.) Representative PSD data in the micropore range are shown in FIG. 15B (PSD data for all samples are shown in
[0080] Overall, C-xx and EC-xx were monolithic materials with total specific pore volumes calculated via V.sub.Total=(1/ρ.sub.b)−(1/ρ.sub.s) many-fold higher (up to 12×) than the sum of pore volumes below 300 nm (V.sub.1.7-300_nm+V.sub.micropore,N2). Below 300 nm, porosities were dominated by pore sizes <1.7 nm: in C-xx V.sub.micropore,N2 was 60-70% of (V.sub.1.7-300_nm+V.sub.micropore,N2); in EC-xx that ratio was higher, in the range of 85-90%. In summary, both C-xx and EC-xx were essentially bimodal macroporous/microporous materials, which, together with their monolithicity, are highly desirable properties, as described in embodiments of the invention herein.
[0081] EXAMPLE 9. Comparative gas sorption of CO.sub.2, CH.sub.4, N.sub.2 and H.sub.2 by C-xx and EC-xx. It is known that CCS by nanoporous materials involves kinetic and thermodynamic factors related to the pore size, and the surface properties of the adsorber. The micropore size distribution of C-xx and CE-xx (
[0082] Using the van der Waals radius of CO.sub.2 (2.57 Å) and considering either the average BET surface area (366±46 m.sup.2 g.sup.−1), or the average pore volume of C-xx (0.167 cm.sup.3 g.sup.−1 via low-pressure N.sub.2 sorption; Table 4), the theoretical uptake of CO.sub.2 should be either at 2.93 mmol or at 3.90 mmol g.sup.−1, respectively. The experimental CO.sub.2 uptake (3.3 mmol of CO.sub.2 per gram of C-xx) is closer to the theoretical value calculated via the BET surface area, and in fact not very far off the value calculated from the micropore volume. Things, however, are different for EC-xx: considering the average BET surface area of those materials (1409±355 m.sup.2 g.sup.−1), the theoretical CO.sub.2 uptake (for monolayer coverage) should be 11.3 mmol g.sup.−1; considering the average micropore volume (0.417 cm.sup.3 g.sup.−1 via low-pressure N.sub.2 sorption; Table 4) the theoretical uptake of CO.sub.2 should be at 9.74 mmol per gram of EC-xx. Both calculated values are significantly higher than the top experimental CO.sub.2 uptake of 4.9 mmol of CO.sub.2 per gram of EC-xx. Clearly, on one hand EC-xx is more efficient than C-xx in uptaking CO.sub.2, however, the increased uptake is not as large as would have been expected by the increase in either surface area or micropore volume. Apart from a slight shift in the average pore sizes (
[0083] The promising levels of CO.sub.2 adsorption by C-xx and EC-xx motivated gas adsoprtion selectivity studies towards fuels (CH.sub.4 and H.sub.2, relevant to pre-combustion gas purification) as well as towards N.sub.2 (relevant to post-combustion CCS).
TABLE-US-00005 TABLE 5 Adsorption capacities and selectivities as shown. Gas sorption data for CO.sub.2, CH.sub.4, N.sub.2 and H2 by C-xx and by EC-xx at 273 K, 1 bar. N.sub.2 adsorption CO.sub.2 adsorption H.sub.2 adsorption CH.sub.4 adsorption @ 1 bar (273 K) @ 1 bar (273 K) @ 1 bar (273 K) @ 1 bar (273 K) Selectivity Sample mmol/g % w/w mmol/g % w/w mmol/g % w/w mmol/g % w/w CO.sub.2/N.sub.2 CO.sub.2/H.sub.1 CO.sub.2/ CH.sub.4 CH.sub.4/N.sub.2 CH.sub.4/H.sub.1 PA-xx 5 — — 0.91 4.00 — — 0.22 0.35 — — 10.0 — — 10 — — 0.85 3.74 — — 0.17 0.27 — — 13.0 — — 15 — — 0.86 3.78 — — 0.21 0.33 — — 9.40 — — 20 — — 0.86 3.78 — — 0.22 0.35 — — 9.60 — — 25 — — 0.80 3.52 — — 0.19 0.30 — — 10.5 — — C-xx 5 0.32 0.90 3.27 14.4 0.05 0.01 1.68 2.68 30.6 180 3.18 9.64 56.7 10 0.29 0.81 2.99 13.2 0.05 0.01 1.51 2.41 26.6 380 3.27 8.14 116 15 0.36 1.03 3.05 13.4 0.05 0.01 1.52 2.43 25.5 222 3.36 7.60 66.2 20 0.31 0.87 2.91 12.8 0.05 0.01 1.49 2.38 24.7 301 3.22 7.67 93.6 25 0.35 0.98 3.07 13.5 0.04 0.00 1.59 2.54 26.3 310 3.13 8.38 99.0 EC-xx 5 — — 4.66 20.5 0.08 0.01 2.12 3.39 30.9 284 3.08 10.0 92.4 10 0.25 0.70 4.62 20.4 0.04 0.00
2.09 3.34 20.5 336 2.74 7.51 122 15 0.38 1.06 4.67 20.5 0.04 0.00
2.04 3.26 17.1 342 2.94 5.81 116 20 0.33 0.92 4.64 20.4 0.02 0.00
2.05 3.28 16.8 928 2.60 6.47 356 25 0.44 1.23 4.85 21.3 0.03 0.00
2.16 3.45 17.9 584 2.84 6.32 205
indicates data missing or illegible when filed
[0084] The relative selectivity of C-xx and EC-xx towards the four gasses herein was quantified thermodynamically using Henry's law (Perry's Chemical Engineer's Handbook, 6th Edition, Green, D. W.; Perry, R. H, Eds, McGraw-Hill, 1984, pp 9-14, ISBN 0-07-049479-7). Selectivity for one gas versus another was defined as the ratio of the Henry's law constants, KH, for the gasses under consideration; in turn, the KH values were obtained from the slopes of the linear parts of the isotherms of
[0085] The following Examples provide additional experimental details of the procedures used in the invention.
[0086] EXAMPLE 10. Materials. All reagents and solvents were used as received, unless noted otherwise. Anhydrous tetrahydrofuran (THF) and 1,2,4,5-benzenetetracarboxylic acid (pyromellitic acid, PMA, 96%) were purchased from Sigma Aldrich Chemical Co. Deuterated DMSO (DMSO-d.sub.6) and deuterated chloroform (CDCl.sub.3) were obtained from Cambridge Isotope Laboratories. Tris(4-isocyanatophenyl)-methane (TIPM) was obtained from Covestro LLC (formerly Bayer Corporation U.S.A.) as a 27% w/w solution in dry ethyl acetate under the trade name Desmodur RE. Siphon grade CO.sub.2, argon (99.99999%), N.sub.2 (99.999%), H.sub.2 (99.999%), CO.sub.2 (99.999%), and CH.sub.4 (99.99%) were purchased from Ozark Gas (Rolla, Mo.).
[0087] EXAMPLE 11. Synthesis of polymeric aerogels (PA-xx). In a typical procedure, PMA (1.77 g, 6.96 mmol, re-dried at 120° C. for 24 h) was dissolved in variable amounts of anhydrous THF and the solution was added to 13.6 g of Desmodur RE (containing 3.67 g, 10.0 mmol of TIPM). The resulting solution was stirred at room temperature under N.sub.2 for 10 min, and subsequently was poured into molds (Wheaton 4 mL Polypropylene Omni-Vials 1.04 cm in inner diameter, Fisher part No. 225402), which were then sealed and left for gelation. The total weight percent concentration of monomers (PMA+TIPM) in the solution was varied by varying the amount of solvent (THF), and is denoted by extension -xx in the sample names, which are referred to as PA-xx. (PA: Polymeric Aerogels; xx was varied in the range 5≤xx≤25, at 5 levels). All solutions gelled at room temperature. (Attempted gelation of a PA-2.5 solution failed at room temperature, but that solution gelled at 60° C.). All formulations and gelation times are summarized in Table 1. All gels were aged for 12h at room temperature in their molds, then they were removed from the molds, washed with THF (2×, 8h each time), and acetone (4×, 8h each time), using an amount of solvent equal to 4× the volume of the gel for each wash. Finally, wet-gels were dried with liquid CO.sub.2 in an autoclave taken out as a supercritical fluid (SCF).
[0088] EXAMPLE 12. Conversion of PA-xx aerogels to carbon aerogels (C-xx). PA-xx aerogel monoliths were transferred into a MTI GSL1600X-80 tube furnace (alumina 99.8% pure, 72/80 mm inner/outer diameters, 457 mm heating zone). The temperature was raised to 800° C. at 5° C. min.sup.−1 under flowing Ar (150 mL min.sup.−1) for 5 h. At the end of the heating period the temperature was returned to room temperature at 5° C. min.sup.−1 under constant flow of Ar.
[0089] EXAMPLE 13. Conversion of C-xx aerogels to etched carbon aerogels (EC-xx). C-xx aerogels were placed in a tube furnace under flowing argon and were heated at 1000° C. The flowing gas was switched to CO.sub.2 and the temperature was maintained at that level for 3 h. Typically, that process was carried out in tandem with carbonization. Subsequently, the flowing gas was switched back to Ar and the temperature was returned to room temperature at 5° C. min.sup.−1 under constant flow of Ar.
[0090] EXAMPLE 14. Methods. Drying of acetone-exchanged wet-gels with supercritical fluid (SCF) CO.sub.2 was carried out in an autoclave (SPIDRY Jumbo Supercritical Point Dryer, SPI Supplies, Inc. West Chester, Pa.). Samples were loaded into the autoclave and acetone was added till all samples were submerged. The pressure vessel was closed and liquid CO.sub.2 was allowed in at room temperature until it displaced all acetone, which was then drained out. Liquid CO.sub.2 was allowed in the vessel several more times until acetone was extracted out of the pores of the samples completely. The criterion for the latter was that CO.sub.2 released from the vessel formed powder of dry ice. Finally, the temperature of the autoclave was raised to 40° C. and SCF CO.sub.2 was vented off as a gas.
[0091] EXAMPLE 15. Physical Characterization: Bulk densities (ρ.sub.b) were calculated from the weight and the physical dimensions of the samples. Skeletal densities (ρ.sub.s) were measured with helium pycnometry using a Micromeritics AccuPyc II 1340 instrument.
[0092] EXAMPLE 16. Chemical Characterization: CHN elemental analysis was performed by Intertek Pharmaceutical Services (Whitehouse, N.J.). Infrared (IR) spectra were taken in KBr, on a Nicolet-FTIR Model 750 spectrometer. Liquid .sup.13C-NMR spectra of monomers were obtained with a 400 MHz Varian Unity Inova NMR instrument (100 MHz carbon frequency). Solid-state CPMAS .sup.13C-NMR spectra were obtained with samples ground into fine powders on a Bruker Avance III 400 MHz spectrometer with a carbon frequency of 100 MHz, using a 7 mm Bruker MAS probe at a magic angle spinning rate of 5 kHz, with broadband proton suppression, and the CP TOSS pulse sequence. The Total Suppression of Spinning Sidebands (TOSS) pulse sequence was applied by using a series of four properly timed 180° pulses on the carbon channel at different points of a cycle before the acquisition of the FID, after an initial excitation with a 90° pulse on the proton channel. The 90° excitation pulse on the proton and the 180° excitation pulse on carbon were set to 4.2 μs and 10 μs, respectively. A contact time of 2 ms was used for cross polarization. Solid-state .sup.13C NMR spectra were referenced externally to glycine (carbonyl carbon at 176.03 ppm). Chemical shifts are reported versus TMS (0 ppm). Solid-state CPMAS .sup.15N-NMR spectra were also obtained on the same Bruker Avance III 400 MHz Spectrometer with a nitrogen frequency of 40.557 MHz, using a 7 mm Bruker MAS probe with broadband proton suppression and magic angle spinning rate of 5 kHz. For cross polarization, a 90° proton excitation pulse was set to 4.2 μs with 2 ms contact time. Chemical shifts are reported versus liquid ammonia (0 ppm) and were externally referenced to glycine (amine nitrogen at 33.40 ppm). In all solid-state NMR experiments the relaxation delay was set at 5 s.
[0093] XPS data were obtained with a Kratos Axis 165 Photoelectron Spectroscopy System. Flat samples were placed on conductive carbon tape that was then adhered to stainless steel sample holders. Samples were introduced into the analysis chamber one at a time and the chamber was evacuated at 10.sup.−8 Torr or lower. No ion sputtering was performed on any of the samples. An Al monochromatic source at 150 watts was used for excitation. A charge neutralizer was used to reduce the effects of differential or sample charging. The analysis area was 700×300 microns. Elemental quantification calculations were based on broad survey results from single sweeps at higher sensitivity (Pass Energy=80), and were carried out with the Kratos Axis Vision processing software and its appropriate relative sensitivity factors for the particular XPS system. High resolution elemental scans where carried out at a lower sensitivity (Pass Energy=20), using multiple sweeps to improve the signal-to-noise ratios.
[0094] EXAMPLE 17. Structural Characterization: Scanning electron microscopy (SEM) was conducted with Au-coated samples on a Hitachi Model S-4700 field-emission microscope. The fundamental building blocks of all aerogels were probed with small angle X-ray scattering (SAXS), using ˜2 mm thick disks cut either with a knife (in case of PA-xx, very important), or with a diamond saw (in case of C-xx). SAXS was conducted with a PANalytical X'Pert Pro multipurpose diffractometer (MPD) configured for SAXS, using Cu Kα radiation (wavelength=1.54 Å), a 1/32° SAXS slit, a 1/16° antiscatter slit on the incident beam side, and a 0.1 mm antiscatter slit together with a Ni 0.125 mm automatic beam attenuator on the diffracted beam side. Samples were placed in circular holders between thin Mylar sheets, and scattering intensities were measured by running 2θ scans from −0.1° to 5° with a point detector in the transmission geometry. All scattering data were reported in arbitrary units as a function of Q, the momentum transferred during a scattering event. Data analysis was conducted using the Beaucage Unified Model applied with the Irena SAS tool for modeling and analysis of small angle scattering within the Igor Pro application (a commercial scientific graphing, image processing, and data analysis software from Wave Metrics, Portland, Oreg.).
[0095] EXAMPLE 18. Thermal Characterization: Thermogravimetric analysis (TGA) was conducted under N.sub.2 with a TA Instruments Model TGA Q50 analyzer, using a heating rate of 5° C. min.sup.−1.
[0096] EXAMPLE 19. Porosimetry and gas sorption selectivity study: All samples were degassed at 80° C. for 24 h prior to each gas sorption study. BET surface areas and pore size distributions for pore sizes in the 1.7-300 nm range were determined with N.sub.2-sorption porosimetry at 77 K using a Micromeritics ASAP 2020 surface area and porosity analyzer. Micropore analysis was conducted either with N.sub.2-sorption, at 77 K using a low-pressure transducer (0.1 Torr) on the Micromeritics ASAP 2020 surface area and porosity analyzer, or with CO.sub.2-sorption up to 760 torr (0.03 relative pressure) at 273 K (ice-water bath) using a Micromeritics Tristar II 3020 version 3.02. The same instrument was used for a relative adsorption study for N.sub.2, H.sub.2, CH.sub.4 and CO.sub.2 at 273 K. Adsorption isotherms were obtained at 0° C. up to 1 bar, and the gas sorption selectivities were calculated with Henry's law: C=KH×p, where, C: concentration (mmol g.sup.−1) in phase I; p: pressure (bar) in phase II; k.sub.H: Henry's law constant (mmol g.sup.−1 bar.sup.−1), from the ratios of the low-pressure slopes (<0.1 bar) of the corresponding isotherms (
[0097] As can be easily understood from the foregoing, the basic concepts of the present invention may be embodied in a variety of ways. The invention involves numerous and varied embodiments of treatments of the conditions described herein, and the like.
[0098] As such, the particular embodiments or elements of the invention disclosed by the description or shown in the figures or tables accompanying this application are intended to be exemplary of the numerous and varied embodiments generically encompassed by the invention or equivalents encompassed with respect to any particular element thereof. In addition, the specific description of a single embodiment or element of the invention may not explicitly describe all embodiments or elements possible; many alternatives are implicitly disclosed by the description and figures.
[0099] It should be understood that each element of an apparatus or each step of a method may be described by an apparatus term or method term. Such terms can be substituted where desired to make explicit the implicitly broad coverage to which this invention is entitled. As but one example, it should be understood that all steps of a method may be disclosed as an action, a means for taking that action, or as an element which causes that action. Similarly, each element of an apparatus may be disclosed as the physical element or the action which that physical element facilitates.
[0100] In addition, as to each term used, it should be understood that unless its utilization in this application is inconsistent with such interpretation, common dictionary definitions should be understood to be included in the description for each term as contained in the Random House Webster's Unabridged Dictionary, second edition, each definition hereby incorporated by reference.
[0101] All numeric values herein are assumed to be modified by the term “about”, whether or not explicitly indicated. For the purposes of the present invention, ranges may be expressed as from “about” one particular value to “about” another particular value. When such a range is expressed, another embodiment includes from the one particular value to the other particular value. The recitation of numerical ranges by endpoints includes all the numeric values subsumed within that range. A numerical range of one to five includes, for example, the numeric values 1, 1.5, 2, 2.75, 3, 3.80, 4, 5, and so forth. It will be further understood that the endpoints of each of the ranges are significant both in relation to the other endpoint and independently of the other endpoint. When a value is expressed as an approximation by use of the antecedent “about,” it will be understood that the particular value forms another embodiment. The term “about” generally refers to a range of numeric values that one of skill in the art would consider equivalent to the recited numeric value or having the same function or result. Similarly, the antecedent “substantially” means largely, but not wholly, the same form, manner or degree and the particular element will have a range of configurations as a person of ordinary skill in the art would consider as having the same function or result. When a particular element is expressed as an approximation by use of the antecedent “substantially,” it will be understood that the particular element forms another embodiment.
[0102] It is to be understood that, as used herein, the grammatical conjunction “and/or” refers throughout to either or both of the stated possibilities.
[0103] The use of the term “or” in the claims is used to mean “and/or” unless explicitly indicated to refer to alternatives only or the alternatives are mutually exclusive, although the disclosure supports a definition that refers to only alternatives and “and/or.”
[0104] As used in this specification and claim(s), the words “comprising” (and any form of comprising, such as “comprise” and “comprises”), “having” (and any form of having, such as “have” and “has”), “including” (and any form of including, such as “includes” and “include”) or “containing” (and any form of containing, such as “contains” and “contain”) are inclusive or open-ended and do not exclude additional, unrecited elements or method steps.
[0105] Moreover, for the purposes of the present invention, the term “a” or “an” entity refers to one or more of that entity unless otherwise limited. As such, the terms “a” or “an”, “one or more” and “at least one” can be used interchangeably herein.
[0106] As used herein, the term “composition” generally refers to any product comprising the specified ingredients in the specified amounts, as well as any product which results, directly or indirectly, from combinations of the specified ingredients in the specified amounts. It is to be understood that the compositions described herein may be prepared from isolated compounds described herein or from salts, solutions, hydrates, solvates, and other forms of the compounds described herein. It is also to be understood that the compositions may be prepared from various amorphous, non-amorphous, partially crystalline, crystalline, and/or other morphological forms of the compounds described herein. It is also to be understood that the compositions may be prepared from various hydrates and/or solvates of the compounds described herein. Accordingly, such compositions that recite compounds described herein are to be understood to include each of, or any combination of, the various morphological forms and/or solvate or hydrate forms of the compounds described herein.
[0107] For the purpose of this invention, it is to be understood that terms such as “gel and/or aerogel composition”, “gel and/or aerogel material”, “gel and/or aerogel”, and related terms used herein, may be used interchangeably, unless clearly indicated by the context.
[0108] The background section of this patent application provides a statement of the field of endeavor to which the invention pertains. This section may also incorporate or contain paraphrasing of certain United States patents, patent applications, publications, or subject matter of the claimed invention useful in relating information, problems, or concerns about the state of technology to which the invention is drawn toward. It is not intended that any United States patent, patent application, publication, statement or other information cited or incorporated herein be interpreted, construed, or deemed to be admitted as prior art with respect to the invention.
[0109] The claims set forth in this specification are hereby incorporated by reference as part of this description of the invention, and the applicants expressly reserve the right to use all of or a portion of such incorporated content of such claims as additional description to support any of or all of the claims or any element or component thereof, and the applicants further expressly reserve the right to move any portion of or all of the incorporated content of such claims or any element or component thereof from the description into the claims or vice-versa as necessary to define the matter for which protection is sought by this application or by any subsequent application or continuation, division, or continuation-in-part application thereof, or to obtain any benefit of reduction in fees pursuant to, or to comply with the patent laws, rules, or regulations of any country or treaty, and such content incorporated by reference shall survive during the entire pendency of this application including any subsequent continuation, division, or continuation-in-part application thereof or any reissue or extension thereon.
[0110] Additionally, the claims set forth in this specification are further intended to describe the metes and bounds of a limited number of the preferred embodiments of the invention and are not to be construed as the broadest embodiment of the invention or a complete listing of embodiments of the invention that may be claimed. The applicants do not waive any right to develop further claims based upon the description set forth above as a part of any continuation, division, or continuation-in-part, or similar application.
[0111] While the disclosure has been illustrated and described in detail in the figures and foregoing description, the same is to be considered as illustrative and not restrictive in character, it being understood that only selected embodiments have been shown and described and that all changes, modifications and equivalents that come within the spirit of the disclosures described heretofore and/or defined by the following claims are desired to be protected. It will be apparent to one of ordinary skill in the art that various changes and modifications can be made to the claimed invention without departing from the spirit and scope thereof. Thus, for example, those skilled in the art will recognize, or be able to ascertain, using no more than routine experimentation, numerous equivalents to the specific substances and procedures described herein. In addition, all publications cited herein are indicative of the level of skill in the art and are hereby incorporated by reference in their entirety as if each had been individually incorporated by reference and fully set forth.