Patent Application
20250163219
Aspects of the present disclosure are described in Abdulhamid, Mahmoud A., “Tröger's base-derived dianhydride as a promising contorted building block for polyimide-based membranes for gas separation” published in Volume 310, Separation and Purification Technology on Apr. 1, 2023, which is incorporated herein by reference in its entirety.
The present disclosure is directed towards a membrane-based separation application, particularly to a multi-layered Tröger's base-derived dianhydride complex used as a building block for polyimide-based membranes for gas separation.
The “background” description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present invention.
Membrane processes for gas separation are gaining a larger acceptance in industry and are competing with consolidation operations. Gas separation across a membrane is a pressure-driven process, where the driving force is the difference in pressure between the inlet of raw material and the outlet of the product. Traditionally, the membrane used in the process is a non-porous layer. The performance of the membrane depends on permeability and selectivity of a gas. Permeability is affected by the penetrant size, where larger gas molecules have a lower diffusion coefficient. The polymer chain flexibility and free volume in the polymer of the membrane material influences the diffusion coefficient, as the space within the permeable membrane must be large enough for the gas molecules to diffuse across. Permeability is the ability of the membrane to allow the permeating gas to diffuse through the material of the membrane as a consequence of the pressure difference over the membrane. The selectivity of a membrane is a measure of the ratio of permeability of the relevant gases for the membrane. Traditional membrane separation techniques, such as pressure swing absorption and cryogenic distillation, are inefficient in challenging and harsh environments. Polyimides have attracted attention as high-performance polymer materials for membrane-based separation applications due to their thermal stability, mechanical properties, solution-processability, and structural tunability.
Gas separation was shown in soluble polyimides prepared from a commonly used dianhydride, 4,4′-(hexafluoroisopropylidene)diphthalic anhydride (6FDA), and various diamines units. Although the obtained selectivity was good, the permeability could use improvement. During the last three decades, different strategies were developed to boost membrane performance by incorporating fillers, blends, thermal annealers, and developing new contorted building blocks. Amongst the different strategies, the synthesis of new contorted building blocks allows fine-tuning of the structure to achieve higher separation performance. Contorted building blocks contribute to higher gas separation performance, due to their potential to improve insufficient packing of polymer chains, potential to increase fractional free volume, and potential to enhance membrane permeability.
Polyimides are made from diamines and dianhydrides, splitting the development of building blocks into two parts: i) diamine and ii) dianhydride synthesis. Due to the lesser complexity of diamine preparation, various contorted diamines were developed and used for the preparation of polyimides for gas separation applications, such as Tröger's base-, Tröger's base carbocyclic pseudo counterpart-, triptycene-, ethanoanthracene-, and catalytic arene-norbornene annulation (CANAL)-based diamines. Tröger's base-based diamines were investigated due to their V-shaped structure, simple chemistry, and various starting materials availability, allowing a tailoring the diamines to improve specific separation features. For instance, methyl substituted Tröger's base-based diamine was reacted with 6FDA, pyromellitic dianhydride (PMDA), and bisanhydride of 3,3,3′,3′-tetramethyl-6,6′,7,7′-tetracarboxy-1,1′-spirobisindane (SBIDA) to achieve high gas permeability and moderate selectivity [M. Lee, C. G. Bezzu, M. Carta, P. Bernardo, G. Clarizia, J. C. Jansen, N. B. McKeown, Enhancing the Gas Permeability of Tröger's Base Derived Polyimides of Intrinsic Microporosity, Macromolecules. 49 (2016) 4147-4154]. Moreover, polyimides prepared from hydroxyl-functionalized Tröger's base diamine (HTB) exhibited a CO2/CH4 selectivity of 73 and a CO2 permeability of 67 barrer [X. Ma, M. Abdulhamid, X. Miao, I. Pinnau, Facile Synthesis of a Hydroxyl-Functionalized Tröger's Base Diamine: A New Building Block for High-Performance Polyimide Gas Separation Membranes, Macromolecules. 50 (2017) 9569-9576]. This combination of selectivity and permeability allowed 6FDA-HTB to reach the 2008 CO2/CH4 selectivity upper bound, indicating the role of selecting a combination of diamines and dianhydride.
Although diamines have been investigated, the development of new dianhydrides was less progressed due to various challenges associated with dianhydride synthesis, such as solubility of dianhydrides, purity, and solubility of the polyimides. The contorted dianhydrides are limited to triptycene-, ethanoanthracene-, carbocyclic pseudo-Tröger's base-, spirobisindane-, and spirobifluorene-based dianhydride.
Therefore, further development of new contorted dianhydrides will provide a better understanding of diamine and dianhydride selection and also allow for improved separations by fine-tuning their chemical structure. Therefore, it is one object of the present disclosure to provide Tröger's base-based dianhydride (TBDA) and its corresponding polyimides as contorted building blocks for gas separation membranes to overcome the limitations of the art.
In an exemplary embodiment, a Tröger's base (TB) complex is disclosed. The TB complex includes a chemical structure as described:
The X in the above complex is O or N—R1. Further, R1 is a comomoner selected from the group comprising of an aryl group, a heteroaryl group, a Tröger's base compound, or a substituted Tröger's base compound.
In another exemplary embodiment, a polyimide is disclosed. The polyimide includes reacted units of Tröger's base complex as described above. The X is N—R1, and the comonomer R1 is a substituted aryl group.
In some embodiments, the substituted aryl group is a 2,3,5,6-tetramethyl-p-phenylenediamine (TMPD).
In some embodiments, a membrane film is disclosed. The membrane film includes reacted units of Tröger's base complex as described above and 2,3,5,6-tetramethyl-p-phenylenediamine (TMPD).
In some embodiments, the polyimide includes reacted units of the Tröger's base complex as described above. Further, the X is N—R1 and the comonomer R1 is a substituted Tröger's base compound.
In some embodiments, the substituted Tröger's base compound is a 1,7-diamino-6H,12H-5,11-methanodibenzo [1,5]diazocine-2,8-diol (HTB).
In some embodiments, a film membrane is disclosed. The film membrane includes reacted units of Tröger's base complex as described above and HTB.
In some embodiments, a method of making the polyimide is disclosed. The method includes heating the TB complex of Formula I with a phenol to a first temperature to form a reaction mixture and the X is O. Further, the method includes adding the comonomer to the reaction mixture; and heating the reaction mixture to a second temperature. Furthermore, the method includes precipitating the reaction mixture in a first organic solvent to form a solid, precipitating the solid in a second organic solvent to form the polyimide, and drying the polyimide.
In some embodiments, the membrane film has a decomposition temperature of 410° C. to 440° C. by TGA.
In some embodiments, the gas permeability of the membrane film is in the following order: carbon dioxide>hydrogen>oxygen>methane>nitrogen.
In some embodiments, the gas permeability of the membrane film is in the following order: hydrogen>carbondioxide>oxygen>nitrogen>methane.
In some embodiments, the membrane film comprises hydrogen bonds.
In some embodiments, the membrane film has a CO2 permeability of 1400 barrer to 1500 barrer.
In some embodiments, the membrane film has a CO2 permeability of 60 barrer to 80 barrer.
In some embodiments, the membrane film has a CO2/CH4 selectivity of 15 to 25.
In some embodiments, the membrane film has a CO2/CH4 selectivity of 30 to 60.
In some embodiments, the membrane film has a diffusion coefficient of CO2 of 2.0×10−7 cm2 s−1 to 5.0×10−7 cm2 s−1.
In some embodiments, the membrane film has a diffusion coefficient of CO2 of 2.0×10−1 cm2 s−1 to 3.0×10−1 cm2 s−1.
In some embodiments, after aging for 80 days to 100 days, the membrane film has a higher H2/N2, H2/CH4, O2/N2, and CO2/CH4 selectivity compared to the membrane film before the aging.
In some embodiments, after aging for 40 days to 60 days, the membrane film has a higher H2/N2, H2/CH4, O2/N2, and CO2/CH4 selectivity compared to the membrane film before the aging.
The foregoing general description of the illustrative present disclosure and the following detailed description thereof are merely exemplary aspects of the teachings of this disclosure and are not restrictive.
A more complete appreciation of this disclosure and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein:
In the following description, it is understood that other embodiments may be utilized, and structural and operational changes may be made without departure from the scope of the present embodiments disclosed herein.
When describing the present disclosure, the terms used are to be construed in accordance with the following definitions, unless a context dictates otherwise. Embodiments of the present disclosure will now be described more fully hereinafter with reference to the accompanying drawings wherever applicable in which some, but not all, embodiments of the disclosure are shown.
Reference will now be made to specific embodiments or features, examples of which are illustrated in the accompanying drawings. In the drawings, whenever possible, corresponding or similar reference numerals will be used to designate identical or corresponding parts throughout the several views. Moreover, references to various elements described herein are made collectively or individually when there may be more than one element of the same type; however, such references are merely exemplary in nature. It may be noted that any reference to elements in the singular may also be constructed to relate to the plural and vice-versa without limiting the scope of the disclosure to the exact number or type of such elements unless set forth explicitly in the appended claims. Further, as used herein, the words “a,” “an,” and the like generally carry a meaning of “one or more,” and “at least one,” unless stated otherwise.
Furthermore, the terms “approximately,” “approximate,” “about,” and similar terms generally refer to ranges that include the identified value within a margin of 20%, 10%, or preferably 5%, and any values therebetween.
The use of the terms “include,” “includes,” “including,” “have,” “has,” or “having” should be generally understood as open-ended and non-limiting unless specifically stated otherwise.
As used herein, “substituted” refers to all permissible substituents of the compounds described herein. Substituted refers to at least one hydrogen atom that is replaced with a non-hydrogen group, provided that normal valencies are maintained and that the substitution results in a stable compound. In the broadest sense, the permissible substituents include acyclic and cyclic, branched and unbranched, carbocyclic and heterocyclic, aromatic and nonaromatic substituents of organic compounds. Non-limiting examples of substituents include halogens, hydroxyl groups, or any other organic groupings containing any number of carbon atoms, preferably 1-14 carbon atoms, and optionally include one or more heteroatoms such as oxygen, sulfur, or nitrogen grouping in linear, branched, or cyclic structural formats. Representative substituents include alkyl, substituted alkyl, alkenyl, substituted alkenyl, alkynyl, substituted alkynyl, phenyl, substituted phenyl, aryl, substituted aryl, arylalkyl, heteroaryl, substituted heteroaryl, halo (e.g., chloro, bromo, iodo, fluoro), hydroxyl, alkoxy, substituted alkoxy, alkoxycarbonyl, oxo, alkanoyl, aryloxy, alkanoyloxy, phenoxy, substituted phenoxy, aroxy, substituted aroxy, thiol, substituted thiol, alkylthio, substituted alkylthio, phenylthio, substituted phenylthio, arylthiol, substituted arylthio, arylalkylthio, alkylthiono, arylthiono, arylalkylthiono, cyano, isocyano, substituted isocyano, carbonyl, substituted carbonyl, carboxyl, substituted carboxyl, amino, substituted amino, alkylamino, cycloalkylamino, arylamino, arylalkylamino, disubstituted amino, alkanoylamino, aroylamino, arylalkanoylamino, amido, substituted amido, sulfonyl, substituted sulfonyl, alkyl sulfonyl, aryl sulfonyl, arylalkylsulfonyl, sulfonamide, substituted sulfonamide, sulfonic acid, nitro, phosphoryl, substituted phosphoryl, phosphonyl, substituted phosphonyl, polyaryl, substituted polyaryl, C3-C20 cyclic, substituted C3-C20 cyclic, heterocyclic, substituted heterocyclic, amino acid, peptide, polypeptide groups, and mixtures thereof. Non limiting examples of substituents (or functional groups, moieties, etc.) include —OH, —F, —Cl, —Br, —I, —NH2, —NO2, —COOH, —CO2CH3, —CN, —SH, —CH3, —OCH3, —OCH2CH3, —C(O)CH3, —N(CH3)2, —C(O)NH2, or —OC(O)CH3. The substituents may themselves be optionally substituted and may be either unprotected, or protected as necessary, as known to those skilled in the art.
The term “alkyl”, as used herein, unless otherwise specified, refers to a straight, branched, or cyclic, saturated aliphatic fragment having 1 to 26 carbon atoms, (e.g., C1, C2, C3, C4, C5, C6, C7, C8, C9, C10, C11, etc.) and specifically includes, but is not limited to, methyl, ethyl, propyl, isopropyl, butyl, isobutyl, t-butyl, pentyl, isopentyl, neopentyl, hexyl, isohexyl, 3-methylpentyl, 2,2-dimethylbutyl, 2,3-dimethylbutyl, 2-ethylhexyl, heptyl, octyl, nonyl, 3,7-dimethyloctyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, octadecyl, nonadecyl, eicosyl, guerbet-type alkyl groups (e.g., 2-methylpentyl, 2-ethylhexyl, 2-propylheptyl, 2-butyloctyl, 2-pentylnonyl, 2-hexyldecyl, 2-heptylundecyl, 2-octyldodecyl, 2-nonyltridecyl, 2-decyltetradecyl, and 2-undecylpentadecyl), as well as cyclic alkyl groups (cycloalkyls) such as cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, norbornyl, and adamantyl.
As used herein, “aryl” refers to a mono-, bi-, or tri-cyclic aromatic hydrocarbon moiety of 6 to 15 ring atoms, which is optionally substituted with one or more, typically one, two, or three, substituents within the ring structure or that replace a hydrogen. When two or more substituents are present in an aryl group, each substituent is independently selected. An aryl may refer to a carbocyclic aromatic monocyclic group containing 6 carbon atoms, which may be further fused to a second 5- or 6-membered carbocyclic group, which may be aromatic, saturated, or unsaturated. Exemplary aryl includes, but is not limited to, benzene, phenyl, anthracenyl, indanyl, 1-naphthyl, 2-naphthyl, tetrahydronaphthyl, and the like, each of which can optionally be substituted. The fused aryls may be connected to another group either at a suitable position on the cycloalkyl/cycloalkenyl ring or the aromatic ring.
The term “arylalkyl”, as used herein, refers to a straight or branched chain alkyl moiety (as defined above), that is substituted with an aryl group (as defined above), examples of which include, but are not limited to, benzyl, phenethyl, 2-methylbenzyl, 3-methylbenzyl, 4-methylbenzyl, 2,4-dimethylbenzyl, 2-(4-ethylphenyl)ethyl, 3-(3-propylphenyl)propyl, and the like.
As used herein, “heteroaryl group” refers to a monovalent mono- or bicyclic aromatic moiety of 5 to 12 ring atoms containing one, two, or three ring heteroatoms selected from N, O, or S, the remaining ring atoms being C. The heteroaryl ring can be optionally substituted with one or more substituents, typically one or two substituents. Exemplary heteroaryl includes, but is not limited to, pyridyl, furanyl, thiophenyl, thiazolyl, isothiazolyl, triazolyl, imidazolyl, isoxazolyl, pyrrolyl, pyrazolyl, pyrimidinyl, benzofuranyl, isobenzofuranyl, benzothiazolyl, benzoisothiazolyl, benzotriazolyl, indolyl, isoindolyl, benzoxazolyl, quinolyl, isoquinolyl, benzimidazolyl, benzisoxazolyl, benzo thiophenyl, dibenzofuran, and benzodiazepin-2-one-5-yl, and the like.
As used herein, the term “alkoxy” refers to an alkyl group which is singularly bonded to oxygen; thus R—O, where R has C1-C10 carbon atoms.
As used herein, “Tröger's base” refers to any Tröger's base and/or any derivative thereof. Tröger's base is a white solid tetracyclic organic compound with the chemical formula (CH3C6H3NCH2)2CH2. The Tröger's base, as referred to herein, may be substituted or otherwise functionalized.
As used herein, “anhydride” refers to a moiety of the formula R1—C(═O)—O—C(═O)—R2, where R1 and R2 are independently alkyl, haloalkyl, aryl, heteroaryl, cycloalkyl, aromatic alkyl, (cycloalkyl)alkyl, and the like.
Aspects of the present disclosure are directed towards a Tröger's base-derived dianhydride (TBDA) as a contorted building block for polyimide-based membranes for gas separation. For this purpose, TBDA was prepared and used to synthesize two solution-processable polyimides using 2,3,5,6-tetramethyl-p-phenylenediamine (TMPD) and 1,7-diamino-6H,12H-5,11-methanodibenzo[1,5]diazocine-2,8-diol (HTB). The polyimides-, TBDA-TMPD and TBDA-HTB, based membranes demonstrated good thermal stability, CO2 permeability, and high gas selectivity. Fresh and aged polyimide-based membranes exhibited differentiated CO2 permeability and gas selectivity. The present polyimide-based membranes provide a new scope for designing high-performance polyimide-bearing nitrogen groups in backbones of structures for varied separation applications.
A Tröger's base (TB) complex having chemical structure I is described. The TB complex has a following chemical formula:
The compound of Formula I includes two ‘X’ where both ‘X’ may be same or different. In an embodiment, each X is independently selected from O or N—R1. R1 is an aryl group, a substituted aryl group, a heteroaryl group, a Tröger's base compound, or a substituted Tröger's base compound. In a preferred embodiment, ‘X’ is N—R1. Herein, ‘R1’ is a comonomer. In an embodiment, a molar ratio of the TB complex of the Formula I to the comonomer is in the range of 1:5 to 5:1, preferably 1:4 to 4:1, preferably 1:3 to 3:1, more preferably 1:2 to 2:1, and yet more preferably about 1:1. The TB complex of the Formula I and the comonomer may be in repeating units. In some embodiments, the repeating units of the TB complex of the Formula I and the comonomer may be in amounts of 1 to 100,00 units, preferably 50 to 80,000 units, preferably 100 to 60,000 units, preferably 1000 to 50,000 units, preferably 5,000 to 40,000 units, preferably 10,000 to 30,000 units, or preferably about 20,000 units. In some embodiments, R1 may be an aryl group. The aryl group may be one or more of a substituted aryl group and non-substituted aryl group. In some embodiments, the aryl group is substituted and may include one or more functional groups and/or substituents. For example, the substituted aryl group may include one or more of hydrogens, halogens, alkyl groups, alkoxy groups, and/or combinations thereof. Examples of suitable halogens may include, among others, one or more of fluorine, chlorine, bromine, and iodine. Examples of suitable alkyl groups may include, among others, one or more of methyl, ethyl, propyl, isopropyl, butyl, iso-butyl, and/or combinations thereof. Examples of suitable alkoxy groups may include, among others, one or more of methoxy, ethoxy, propoxy, butoxy, pentoxy, hexoxy, heptoxy, octoxy, and/or combinations thereof. These shall not be limiting as other substituents disclosed herein can be present or used. In an embodiment, R1 is a substituted aryl group. In a preferred embodiment, the substituted aryl group is a 2,3,5,6-tetramethyl-p-phenylenediamine (TMPD).
In some embodiments, ‘R1’ is a Tröger's base compound. The Tröger's base compound may be substituted or unsubstituted. In some embodiments, the Tröger's base compound is substituted with one or more functional groups and/or substituents such as halogens, alkyl groups, alkoxy groups, combinations thereof, and the like. In a preferred embodiment, R1 is a substituted Tröger's base compound, and the substituted Tröger's base compound is a 1,7-diamino-6H,12H-5,11-methanodibenzo[1,5]diazocine-2,8-diol (HTB).
A polyimide including the Tröger's base (TB) complex is described. In some embodiments, the polyimide includes repeating units of the TB complex of Formula I, where ‘X’ is N—R1 and R1 is a substituted aryl group. The substituted aryl group is TMPD. In some embodiments, the polyimide includes repeating units of the TB complex of Formula I, where ‘X’ is N—R1 and R1 is a substituted Tröger's base compound. The substituted Tröger's base compound is HTB.
At step 52, the method 50 includes heating the TB complex of Formula I with a phenol to a first temperature to form a reaction mixture. The TB complex has a following chemical formula:
The compound of Formula I includes two ‘X’ where both ‘X’ may be same or different. In an embodiment, each ‘X’ is independently selected from O or N—R1. In a preferred embodiment, ‘X’ is O. The TB complex is heated with a phenol and a catalytic amount of an organic compound containing at least one nitrogen (i.e., the comonomer). The phenol may include phenols and derivatives thereof. For example, in an embodiment, the phenol is a phenol derivative, such as m-cresol, and the phenol derivatives isomers, such as p-cresol and o-cresol. The organic compound containing at least one nitrogen may include a heterocyclic aromatic organic compound. In some embodiments, the organic compound containing at least one nitrogen is quinoline, as well as derivatives and isomers thereof. For example, the organic compound containing at least one nitrogen may be isoquinoline. The heating is preferably carried out in an inert atmosphere. The inert atmosphere may be a nitrogen, xenon, neon, argon, and/or helium atmosphere. The heating is carried out to a temperature range of 80-200° C., preferably 85-150° C., preferably 90-120° C., preferably 95-110° C., and more preferably about 100° C. to form the reaction mixture.
At step 54, the method 50 includes adding a comonomer to the reaction mixture. In an embodiment, the comonomer is 2,3,5,6-tetramethyl-p-phenylenediamine (TMPD). The molar ratio of the TB complex of the Formula I to the TMPD is in the range of 1:5 to 5:1, preferably 1:4 to 4:1, preferably 1:3 to 3:1, more preferably 1:2 to 2:1, and yet more preferably about 1:1. The molar ratio of the TB complex of the Formula I to the comonomer is in the range of 1:5 to 5:1, preferably 1:4 to 4:1, preferably 1:3 to 3:1, more preferably 1:2 to 2:1, and yet more preferably about 1:1.
At step 56, the method 50 includes heating the reaction mixture to a second temperature. In an embodiment, the reaction mixture may be heated under stoichiometric conditions and/or with compounds of high purity. The temperature may range from about room temperature to about 200° C. In many embodiments, the temperature may be gradually increased from a first temperature to one or more other temperatures. For example, the heating may proceed at a first temperature and may be subsequently increased to a second temperature. In an embodiment, the first temperature may be about 50-150° C., preferably 70-130° C., preferably 90-110° C., and more preferably about 100° C., and the second temperature may range from about 150° C. to about 250° C., preferably 160-240° C., preferably 170-230° C., preferably 180-220° C., preferably 190-210° C., and more preferably about 200° C. The duration of the reaction may range from about 1 hour to about 24 hours, preferably 2 to 20 hours, preferably 4 to 18 hours, preferably 6 to 16 hours, preferably 8 to 14 hours, more preferably 10 to 12 hours, and more preferably about 12 hours. In other embodiments, the duration of the reaction may be less than about 1 hour and/or greater than about 24 hours.
At step 58, the method 50 includes precipitating the reaction mixture in a first organic solvent to form a solid. In an embodiment, the first solvent is methanol; optionally other precipitating agents may be used in place of methanol and/or in combination with methanol or the first organic solvent.
At step 60, the method 50 includes precipitating the solid in a second organic solvent to form the polyimide. In some embodiments, the second organic solvent is chloroform; optionally other precipitating agents may be used in place of chloroform and/or in combination with chloroform or the second organic solvent.
At step 62, the method 50 includes drying the polyimide. The polyimide thus formed is dried to a temperature range of 100-150° C., preferably 105-145° C., preferably 110-140° C., preferably 115-130° C., and more preferably about 120° C., for about 18-36 hours, preferably 20-32, preferably 22-26 hours, and more preferably about 24 hours to allow for evaporation of the first organic solvent and the second organic solvent. It is preferred to carry out drying under vacuum to avoid oxidation of the polyimide.
Embodiments of the present disclosure describe membrane films including the polyimides—for example, the membrane films may include and/or may be prepared from any of the TB complexes of Formula I, TBDA-TMPD, and/or TBDA-HTB. The TBDA-HTB-based membrane film includes hydrogen bonds and corresponding polymers made therefrom. The polyimides may be used to fabricate the membrane films, such as thin film composite membranes and/or asymmetric membranes, according to processes and/or methods known in the art. For example, the membrane films may be fabricated by applying a dilute polymer solution containing the Tröger's base polyimides onto a support to form a polyimide coating on a microporous substrate in one step by solvent evaporation. The polyimide coating may be from 1 to 100 coats, preferably 2 to 75 coats, preferably 3 to 50 coats, preferably 4 to 40 coats, preferably 5 to 20 coats, and more preferably about 7 to 15 coats. In another example, the membrane films may be fabricated by one or more of phase separation and phase inversion processes.
In an embodiment, the membrane films may be provided in a variety of geometries, such as flat sheet geometry, a textured (e.g., waves) sheet geometry, a hollow fiber (e.g., cylindrical) geometry, and any geometry known in the art.
The membrane film of the present disclosure demonstrates thermal stability with a decomposition temperature in the range of 410° C. to 440° C., preferably 415 to 435° C., preferably 420 to 430° C., or preferably about 425° C., measured by TGA. In a specific embodiment, the TBDA-TMPD-based membrane has a thermal stability with a decomposition temperature of about 422° C. by TGA. At these temperatures, the carbon content was found to be greater than 90%, preferably 91 to 100%, preferably 92 to 99%, preferably 93 to 98%, preferably 94 to 97%, or preferably 95 to 96%.
The membrane of the present disclosure demonstrates high permeability to CO2. The gas permeability of the TBDA-TMPD-based membrane film lies in the following order: carbon dioxide>hydrogen>oxygen>methane>nitrogen. The gas permeability of the TBDA-HTB-based membrane film is in the following order: hydrogen>carbondioxide>oxygen>nitrogen>methane. In a specific embodiment, the TBDA-TMPD-based membrane has a CO2 permeability coefficient of 1400 barrer to 1500 barrer, preferably 1410 to 1490 barrer, preferably 1420 to 1480 barrer, preferably 1430 to 1470 barrer, preferably 1440 to 1460 barrer, or preferably about 1450 barrer. In an embodiment, the TBDA-HTB-based membrane film has a CO2 permeability coefficient of 60 barrer to 80 barrer, preferably 62 to 78 barrer, preferably 64 to 76 barrer, preferably 66 to 74 barrer, preferably 68 to 72 barrer, or preferably about 70 barrer.
The membrane of the present disclosure also demonstrates high gas selectivity. In a specific embodiment, the TBDA-TMPD-based membrane film has a CO2/CH4 selectivity of 15 to 25, preferably 16 to 20, preferably 17 to 18, and preferably about 17. In some embodiments, the TBDA-HTB-based membrane film has a CO2/CH4 selectivity of 30 to 60, preferably 31 to 55, preferably 32 to 50, preferably 33 to 45, preferably 35 to 40, and more preferably about 38. The TBDA-TMPD-based membrane film has a diffusion coefficient of CO2 of 2.0×10−7 cm2 s−1 to 5.0×10−7 cm2 s−1, preferably 2.5×10−7 to 4.5×10−7 cm2 s−1, preferably 3.0×10−7 to 4.0×10−7 cm2 s−1, or preferably about 3.5×10−7 cm2 s−1. The TBDA-HTB-based membrane film has a diffusion coefficient of CO2 of 2.0×10−8 cm2 s−1 to 3.0×10−1 cm2 s−1, preferably 2.2×10−7 to 2.8×10−7 cm2 s−1, or preferably about 2.4×10−7 to 2.6×10−7 cm2 s−1. The TBDA-TMPD-based membrane film after aging for 80 days to 100 days, preferably 85 to 95 days, preferably about 90 days, has a higher H2/N2, H2/CH4, O2/N2, and CO2/CH4 selectivity compared to the membrane film before the aging. The TBDA-HTB-based membrane film after aging for 40 days to 60 days, preferably 45 to 55 days, or preferably about 50 days, the membrane film has a higher H2/N2, H2/CH4, O2/N2, and CO2/CH4 selectivity compared to the membrane film before the aging.
The following examples demonstrate a Tröger's base-derived dianhydride as a contorted building block for polyimide-based membranes for gas separation. The examples are provided solely for illustration and are not to be construed as limitations of the present disclosure, as many variations thereof are possible without departing from the spirit and scope of the present disclosure.
2,3,5,6-Tetramethyl-p-phenylenediamine (TMPD, 97%), 3,4-dimethoxyaniline (98%), paraformaldehyde ((CH2O)n, 95%), trifluoroacetic acid (CF3COOH, 99%), boron tribromide (BBr3, 99.9%), 4,5-dichlorophthalonitrile (99%), m-cresol (99%), isoquinoline (97%), acetic anhydride ((CH3CO)2O, 98%), dichloromethane (DCM, 99%), N,N-dimethylformamide (DMF, 98.8%), chloroform (CHCl3, 99%), 1-methyl-2-pyrrolidone (NMP, 99.5%), potassium carbonate (K2CO3, 99%), magnesium sulfate (MgSO4, 97%), potassium hydroxide (KOH, >85%), hydrochloric acid (HCl, 37%), methanol (MeOH, 99%), and ethanol (99%) were purchased from Merck and used without further purification. 1,7-Diamino-6H,12H-5,11-methanodibenzo[1,5]diazocine-2,8-diol (HTB, 98%) was prepared as previously reported [X. Ma, M. Abdulhamid, X. Miao, I. Pinnau, Facile Synthesis of a Hydroxyl-Functionalized Tröger's Base Diamine: A New Building Block for High-Performance Polyimide Gas Separation Membranes, Macromolecules. 50 (2017) 9569-9576, incorporated herein by reference in its entirety].
1H NMR spectra of all intermediates (i-v) were obtained from Bruker AVANCE-III spectrometer at 400 MHz in deuterated dimethyl sulfoxide (DMSO-d6). High-resolution mass spectroscopy (HR-MS) analysis of compounds iii, iv, and v were obtained from Thermo LC/MS system with LTQ Orbitrap Velos detectors. Thermal gravimetric analysis (TGA) was conducted on TGA Q5000 under an inert atmosphere with a heating rate of 5° C. min−1. Fourier-transform infrared (FTIR) spectra of the polyimides was acquired using a Thermo Fisher Scientific Nicolet spectrometer (iS10) with a wave number range of 525 cm−1 to 4000 cm−1. Polymer molecular weight (Mw and Mn) and polydispersity index were measured using gel permeation chromatography (GPC) in an Agilent 1200 system. The measurements were performed in dimethylformamide (DMF) using polystyrene reference. The geometric density of the membranes was measured using film thickness, weight data, and area. The hydrogen bonding detection and fractional free volume were conducted by molecular dynamic simulation using Materials Studio 8.0 and Chemaxon software, respectively.
3,4-Dimethoxyaniline (6 g, 39.2 mmol) and paraformaldehyde (1.88 g, 62.7 mmol) were added to the round bottom flask and cooled to −20° C., followed by dropwise addition of CF3COOH (120 ml). The reaction was stirred at room temperature for 48 hours and poured into cooled water (200 ml). The product was extracted using dichloromethane, dried, and concentrated using rota-evaporation. White powder (6 g, 89%) was gained after silica gel column separation using petroleum ether/dichloromethane: 3/7 as eluent. 1H NMR (400 MHz, DMSO-d6): δ 3.64 (s, 6H), 3.72 (s, 6H), 3.99-4.03 (d, 2H, J=16.4 Hz), 4.13 (s, 2H), 4.45-4.49 (d, 2H, J=16.4 Hz), 6.49 (s, 2H), 6.67 (s, 2H).
A solution of intermediate i (2.24 g, 6.54 mmol) in dry dichloromethane was cooled to zero degrees, followed by slow addition of BBr3 (6.3 mL, 65.4 mmol). The reaction was stirred for 2 hours at zero degrees and left to stir overnight at room temperature. The reaction was poured onto 50 mL of cooled water, and the pH was adjusted between 4-5 by adding sodium bicarbonate. The obtained precipitates were filtered and desiccated in the oven at 70° C. under vacuum for 24 hours to achieve an off-white solid (1.0 g, 73% yield). 1H NMR (400 MHz, DMSO-d6): δ 3.72-3.76 (d, 2H, J=16 Hz), 4.01 (s, 2H), 4.31-4.35 (d, 2H, J=16 Hz), 6.25 (s, 2H), 6.42 (s, 2H), 8.57 (s, 2H), 8.75 (s, 2H).
To a round bottom flask containing intermediate ii (0.94 g, 3.28 mmol) and 4,5-dichlorophtalonitrile (1.42 g, 7.22 mmol), 50 mL of dry DMF was added. The reaction medium was heated to 80° C. for 15 minutes before adding potassium carbonate (K2CO3) (2.8 g, 20 mmol), which was added in portions over 5 minutes. The system was stirred overnight and then cooled down to room temperature, and the obtained precipitation was filtered and washed a few times with distilled water and acetone. The white product was then collected and refluxed with dichloromethane (DCM) for 10 hours, filtrated, and dried in the vacuum oven overnight at 120° C. The desired product was obtained as an off-white solid (1.5 g, 86% yield). 1H NMR (400 MHz, DMSO-d6): δ 4.02 (d, 2H, J=16 Hz), 4.15 (s, 2H), 4.45 (d, 2H, J=16 Hz), 6.68 (s, 2H), 6.82 (s, 2H), 7.74 (s, 4H). HR-MS for [M+H+, C31H15N6O4+, ESI]: Calcd: 535.1077; Found: 535.1149.
A solution of KOH (1.75 g, 31 mmol, 8 mL) was added gradually to a dispersion of intermediate iii (0.5 g, 0.935 mmol) in ethanol (8 mL). The reaction was heated to reflux overnight. The clear solution was concentrated in the rotary evaporator, and precipitates were obtained after adding distilled water and HCl (6 M, 2.6 mL). An off-white product was obtained upon HCl addition; the powder was filtered and washed a few times with diluted HCl (1 M). The product was dried for 18 hours in the vacuum oven at 40° C. then washed again with water to eradicate any salt traces. The desired product was obtained after drying as a yellow solid (0.486 g, 85%). 1H NMR (400 MHz, DMSO-d6): δ 3.99-4.03 (d, 2H, J=17 Hz), 4.14 (s, 2H), 4.43-4.47 (d, 2H, J=17 Hz), 6.62 (s, 2H), 6.76 (s, 2H), 7.16 (s, 2H), 7.17 (s, 2H). HR-MS for [M+H+, C31H19N2O12+, ESI]: Calcd: 611.0860; Found: 611.0932.
Intermediate iv (0.45 g, 0.74 mmol) was suspended in 20 mL acetic anhydride. The reaction medium was heated to 120° C. and left to stir overnight. The precipitated solid was filtered and washed three times with acetic anhydride. The product (0.4 g, 95% yield) was gained after vacuum drying at 140° C. for 12 h. 1H NMR (400 MHz, DMSO-d6): δ 4.04 (d, 2H, J=17 Hz), 4.16 (s, 2H), 4.46 (d, 2H, J=17 Hz), 6.66 (s, 2H), 6.7 (s, 2H), 7.63 (m, 4H). HR-MS [M+H+, C31H15N2O10+, ESI]: Calcd: 575.0648; Found: 575.0721.
TBDA (97 mg, 0.17 mmol) and HTB (48 mg, 0.17 mmol) or TMPD (29 mg, 0.17 mmol) were placed in a two-neck round bottom flask equipped with a nitrogen inlet and oil bubbler. 2 mL of m-cresol was added to the round bottom flask, and the reaction was heated to 100° C., where 0.1 mL of isoquinoline was added, followed by gradual heating to 200° C. The solution was precipitated into methanol to achieve fiber-like polymers. Re-precipitation of the polymers from their N-methyl-2-pyrrolidone (NMP) and chloroform solutions for TBDA-HTB and TBDA-TMPD, respectively, was conducted to remove any impurities. 93% to 95% yield was obtained after collecting the polymers from the vacuum oven which was heated at 120° C. for 24 hours. TBDA-HTB: FTIR (v, cm−1): 3000-3680 (—OH), 2830-2990 (—CH), 1776 (asym, C═O), 1706 (sym, C═O), 1354 (C—N); ρ=1.38 g cm−3; FFV=0.12. TBDA-TMPD: FTIR (v, cm−1): 2830-3000 (—CH), 1774 (asym, C═O), 1708 (sym, C═O), 1352 (C—N); Mw=57,115 g mol−1, M=37,429 g mol−1, PDI=1.52. ρ=1.21 g cm−3; FFV=0.20.
TBDA-HTB and TBDA-TMPD polymers were dissolved in NMP and chloroform (2% to 3% w/v), respectively, and the solutions were filtered through 0.45 μm PTFE filters and poured into flat glass Petri dishes. The TBDA-HTB solution was placed in the oven at 60° C. to slowly evaporate NMP under N2 flow, while the TBDA-TMPD membrane was attained from deliberate evaporation of chloroform at room temperature. The two flexible membranes were desiccated in the oven at 120° C. and 250° C. for TBDA-TMPD and TBDA-HTB, respectively, for 24 hours to ensure the total removal of any solvent residual.
The gas permeability of Tröger's base-based polyimides membranes was measured by the constant-volume/variable-pressure method. TBDA-HTB and TBDA-TMPD were degassed in the permeation box for 24 hours at 35° C. before starting measurements. All gases were tested at 2 bar and 35° C., and permeability was calculated based on the following equation:
where P is the gas permeability in barrer [1 barrer=10−10 cm3 (STP) cm cm−2 s−1 cmHg−1)], V is the calibrated permeate volume (cm3), L is the membrane thickness (cm), A is the effective membrane area (cm2), R is the gas constant (0.278 cm3 cmHg cm−3 (STP) K−1), T is the operating temperature (K), pup refers to upstream pressure (cmHg) and dp/dt represent the equilibrium permeate-side pressure increase (cmHg s−1). The selectivity was determined from the permeability ratio of the gases, that is, α=PA/PB.
Referring to
Tröger's base-based dianhydride (TBDA, v) was synthesized in five synthetic steps. Firstly, 3,4-dimethoxyaniline was reacted with paraformaldehyde in CF3COOH to form intermediate i as Tröger's base containing four methoxy groups. The methoxy groups in intermediate i are all converted into hydroxyl groups using BBr3 to achieve intermediate ii. Secondly, intermediate ii was reacted with 4,5-dichlorophthalonitrile through nucleophilic aromatic substitution reaction to produce intermediate iii. Further, the hydrolysis of intermediate iii was conducted using a KOH/water/ethanol system to convert cyano groups (CN) to carboxylic acid groups (COOH), resulting in intermediate iv. Furthermore, the conversion of tetracarboxylic acid to dianhydride was conducted by refluxing intermediate iv with acetic anhydride, resulting in the final product v.
Referring to
Referring to
Both polyimides displayed different solubility behavior in organic solvents due to the difference in functionalities on their backbone. For instance, TBDA-TMPD demonstrated good solubility in chlorinated solvents, such as dichloromethane (DCM), chloroform (CHCl3), and polar aprotic solvents, as shown in Table 1, due to the presence of four methyl groups which helps to increase solubility. However, TBDA-HTB displayed bad solubility, where it was only soluble in NMP and m-cresol at room temperature.
Referring to
TBDA-HTB revealed lower thermal stability and carbon content at all temperatures relative to TBDA-TMPD. This lower stability could be attributed to the earlier degradation of—OH groups on polymer chains of TBDA-HTB. Nonetheless, both polymers showed carbon content of approximately 60% at 700° C. indicating that these polymers can be good contenders to fabricate carbon-based membranes for gas separation applications.
Referring to
The gas separation performance of the aged TBDA-TMPD membrane, which was evaluated after 90 days of physical aging, demonstrated approximately 50% reduction in permeability with 6 to 17% enhancement in gas-pair selectivity. This reduction in permeability and marginal improvement in selectivity is attributed to the physical aging of polymer chains in porous polymers that shrinks pore size and reduce its free volume [R. Swaidan, B. Ghanem, E. Litwiller, I. Pinnau, Physical Aging, Plasticization and Their Effects on Gas Permeation in “rigid” Polymers of Intrinsic Microporosity, Macromolecules, which is incorporated herein by reference in its entirety]. The pure gas measurements of fresh and aged TBDA-HTB and TBDA-TMPD are displayed in Table 3.
amembrane was treated at 250° C.;
bmembrane was treated at 120° C.
Referring to
Furthermore, the low reduction rate in TBDA-HTB indicates a tight structure that is less affected by aging relative to the more open structure of TBDA-TMPD, which showed an about 50% reduction in permeabilities. The low reduction rate was ascribed to the strong hydrogen bond interaction [N. Alaslai, B. Ghanem, F. Alghunaimi, E. Litwiller, I. Pinnau, Pure- and mixed-gas permeation properties of highly selective and plasticization resistant hydroxyl-diamine-based 6FDA polyimides for CO2/CH4 separation, J. Memb. Sci. 505 (2016) 100-107, incorporated herein by reference in its entirety].
Furthermore, the TBDA-TMPD displayed higher diffusion coefficients than TBDA-HTB, as shown in Table 4. This reflects the higher gas permeability of TBDA-TMPD. Further, TBDA-HTB demonstrated higher solubility coefficients for O2 and N2 relative to TBDA-TMPD. Pure-gas diffusion and solubility coefficients of CO2, CH4, O2, and N2 are illustrated in Table 4.
TBDA-HTB revealed a higher diffusion selectivity coefficient relative to TBDA-TMPD, which exceeded two-fold, indicating a higher gas-pair selectivity in TBDA-HTB. The aforementioned diffusion selectivity is illustrated in Table 5. This increase in diffusion selectivity of TBDA-HTB is attributed to the tighter chain packing induced by the presence of tertiary amine and a hydroxyl group [M. A. Abdulhamid, X. Ma, X. Miao, I. Pinnau, Synthesis and characterization of a microporous 6FDA-polyimide made from a novel carbocyclic pseudo Tröger's base diamine: Effect of bicyclic bridge on gas transport properties, Polymer (Guildf), incorporated herein by reference in its entirety]. Further, aged samples of both polymers demonstrated marginal improvement in solubility selectivity.
No changes in diffusion selectivity of TBDA-TMPD were noted after aging; however, differences in diffusion selectivity were observed for the aged sample of TBDA-HTB, which increased by about 30% upon physical aging. This increase in diffusion selectivity reflects the 42% increase in CO2/CH4 after 50 days of aging.
Referring to
As can be seen from
A Tröger's base-based dianhydride (TBDA) was synthesized and characterized. Two TBDA-based polyimides were prepared from polycondensation reactions using two different diamines (i.e., TMPD and HTB). The TBDA-based polyimides demonstrated thermal stability at temperatures exceeding 400° C. TBDA-TMPD displayed higher permeability and selectivity for all tested gases relative to 6FDA-TMPD. Hydroxyl-functionalized TBDA-HTB showed a balanced combination between gas permeability and selectivity with CO2 permeability of 61 and CO2/CH4 selectivity of 55. The TBDA-TMPD membrane displayed CO2 permeability of 1457 barrer and CO2/CH4 selectivity of 17. Physical aging over 50 days of TBDA-HTB membrane revealed CO2 permeability of 61 barrer and CO2/CH4 selectivity of 54. Aged TBDA-HTB exhibited a performance that crossed 2008 upper bound for H2/CH4 separation with an H2 permeability of 147 barrer and an H2/CH4 selectivity of 129. The high gas-pair selectivity for TBDA-HTB is attributed to different hydrogen bonding interactions among the polymer chains. Developing contorted dianhydride provides scope for designing high-performance polyimide-bearing nitrogen groups in their backbones for different separation applications.
Numerous modifications and variations of the present disclosure are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the present disclosure may be practiced otherwise than as specifically described herein.
Support provided by the College of Petroleum Engineering and Geoscience, King Fahd University of Petroleum and Minerals, Saudi Arabia, through Project SF21012 is gratefully acknowledged.
