WO2018187588A1

WO2018187588A1 - Selectively gas permeable graphene oxide membrane element

Info

Publication number: WO2018187588A1
Application number: PCT/US2018/026283
Authority: WO
Inventors: Shijun Zheng; Weiping Lin; Peng Wang
Original assignee: Nitto Denko Corporation
Priority date: 2017-04-06
Filing date: 2018-04-05
Publication date: 2018-10-11

Abstract

Described herein are gas-permeable elements comprising a composite of functionalized graphene oxide distributed within a polyether block amide, which are coated on a porous support, wherein the membrane can be selectively permeable to select gases, such as CO2. Also described herein are methods of making such gas-permeable elements, methods and devices of using the elements for removing gases such as CO2 from unprocessed gas streams.

Description

SELECTIVELY GAS PERMEABLE GRAPHENE OXIDE MEMBRANE ELEMENT

Inventors: Shijun Zheng, Weiping Lin, and Peng Wang

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No. 62/482,451, filed April 06, 2017, which is incorporated by reference by its entirety.

FIELD

The present embodiments are related to polymeric membrane elements, such as a membrane including graphene materials with selective gas permeability.

BACKGROUND Increasing generation of greenhouse gases and harvesting of hydrocarbons have resulted in an abundance of greenhouse gases that are dispersed in air, such as carbon dioxide (C0₂). In some applications, it would be preferable to separate greenhouse gases from a primary gas stream in order to further purify the primary gas stream. Unfortunately, some methods of separating C0₂ require sub-ambient temperatures to effectively separate gas streams. Some membranes use molecular sieves, such as zeolites, to filter C0₂, however, the zeolites must be regenerated once saturated. Other membranes require a complex metal framework to separate carbon dioxide from a main gas stream. As a result, there is a need for a passive, cost-effective method for removing C0₂ from gas streams. Thus, new membrane materials that can achieve such desired properties are in high demand.

SUMMARY

This disclosure relates to a graphene oxide (GO) composition suitable for gas separation applications, such as separating C0₂ from other gas streams. The GO composition may be prepared by using one or more water soluble polymers. Water can be used as a solvent in preparing these GO compositions, which makes the preparation process more environmentally friendly and more cost effective.

Some embodiments include a gas permeable element comprising: a porous support; and a composite coated on the support, wherein the composite comprises a diamine-functionalized graphene oxide material and a polyether block amide, wherein the diamine-functionalized graphene oxide material is distributed within the polyether block amide; and wherein the gas permeable element is selectively permeable to C0₂ gas.

Some embodiments include a method of making a gas permeable element described herein, comprising: curing an aqueous mixture that is coated onto a porous support. In some embodiments, curing is carried out at room temperature until dry. The porous support is coated with the aqueous mixture by applying the aqueous mixture onto the porous support, and repeating as necessary to achieve a layer having a thickness of about 0.1-10 μιτι. The aqueous mixture is formed by mixing a diamine- functionalized graphene oxide material and a polyether block amide in an aqueous liquid.

Some embodiments include a method of preparing a diamine-functionalized graphene oxide material, comprising: mixing graphene oxide and a dimethyl alkyldiamine in an aqueous liquid, followed by heating the mixture at about 30-90 °C for about 4-24 hours, then cooling the mixture to room temperature, and quenching the mixture in an alcohol.

Some embodiments include a gas separation device, comprising: a wall separating a first plenum containing a first gas and second plenum containing a second gas, wherein the wall defines an aperture that allows fluid communication between both plena; and the gas permeable element described herein occluding the aperture, and wherein the device selectively allows C0₂ gas to pass between the plena. BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a depiction of a possible embodiment of an element without a protective coating.

FIG. 2 is a depiction a possible embodiment of an element with a protective coating.

FIG. 3 is a depiction of a possible embodiment for the method of making an element.

FIG. 4 is a diagram depicting the experimental setup for the gas permeability testing. DETAILED DESCRIPTION

I. General.

A selectively gas permeable membrane element includes a membrane element that is selectively permeable for some gas and selectively impermeable for other gases. For example, the gas permeable element may be selectively permeable to a gas of one species or multiple species, such as C0₂, but selectively impermeable to gas of one or more other species, such as N₂, air, or reducing gases. In some embodiments, the selectively permeable element can be permeable to C0₂ while being relatively impermeable to N₂.

Unless otherwise indicated, when a compound or a chemical structure, such as graphene oxide, is referred to as being "optionally substituted," it includes a compound or a chemical structure that either has no substituents (i.e., unsubstituted), or has one or more substituents (i.e., substituted). The term "substituent" has the broadest meaning known in the art, and includes a moiety that replaces one or more hydrogen atoms attached to a parent compound or structure. In some embodiments, a substituent may be any type of group that may be present on a structure of an organic compound, which may have a molecular weight (e.g., the sum of the atomic masses of the atoms of the substituent) of 15-50 g/mol, 15-100 g/mol, 15-150 g/mol, 15-200 g/mol, 15-300 g/mol, or 15-500 g/mol. In some embodiments, a substituent comprises, or consists of: 0-30, 0-20, 0-10, or 0-5 carbon atoms; and 0-30, 0-20, 0-10, or 0-5 heteroatoms, wherein each heteroatom may independently be: N, O, S, P, Si, F, CI, Br, or I; provided that the substituent includes one C, N, O, S, P, Si, F, CI, Br, or I atom. Examples of substituents include, but are not limited to, alkyl, alkenyl, alkynyl, heteroalkyl, heteroalkenyl, heteroalkynyl, aryl, heteroaryl, hydroxy, alkoxy, aryloxy, acyl, acyloxy, alkylcarboxylate, thiol, alkylthio, cyano, halo, thiocarbonyl, O-carbamyl, N-carbamyl, O-thiocarbamyl, N-thiocarbamyl, C-amido, N-amido, S-sulfonamido, N-sulfonamido, isocyanato, thiocyanato, isothiocyanato, nitro, silyl, sulfenyl, sulfinyl, sulfonyl, haloalkyl, haloalkoxyl, trihalomethanesulfonyl, trihalomethanesulfonamido, amino, etc.

For convenience, the term "molecular weight" is used with respect to a moiety or part of a molecule to indicate the sum of the atomic masses of the atoms in the moiety or part of a molecule, even though it may not be a complete molecule. As used herein the term "fluid" includes any substance that continually deforms, or flows, under an applied shear stress. Such non-limiting examples of fluids include Newtonian and/or non-Newtonian fluids. In some embodiments, examples of Newtonian can be gases, liquids, and/or plasmas. In some embodiments, non- Newtonian fluids can be plastic solids (e.g., corn starch aqueous solution, toothpaste). As used herein, the term "fluid communication" means that a fluid can pass through a first component and travel to and through a second component or more components regardless of whether they are in physical communication or the order of arrangement.

II. Selectively Gas Permeable Element. The present disclosure relates to gas separation elements wherein a composite material with high mechanical and chemical stability may be used to remove undesirable gases from a primary gas stream. This element material may be suitable for purification of an unprocessed fluid stream, or removal of a gas pollutant. Some selectively-permeable polymeric elements can have selective permeability to certain gas species, such as C0₂. Some selective gas permeable elements described herein can be GO-based elements having a highly selective permeability to C0₂. In some embodiments, the GO-based elements may comprise multiple layers, wherein at least one layer comprises a GO-based composite of a graphene oxide (GO) material embedded in a polymer matrix. In some embodiments, the graphene oxide can be functionalized. In some embodiments, the functionalized graphene oxide (FGO) comprises a diamine-functionalized GO. In some embodiments, the polymer can comprise a polyether block amide. These GO-based elements may also be prepared using water as a solvent, which can make the manufacturing process much more environmentally friendly and cost effective.

Generally, a selectively permeable element, such as a gas permeable membrane element comprises a porous support and a composite coated onto or disposed on the support. In some embodiments, the selectively permeable element comprises a porous support or substrate, such as a porous support comprising a polymer or hollow fibers. For some elements, the composite is a GO-based composite that is disposed on the porous support. The GO-composite can be in a layer form. The selectively permeable element may further comprise a protective layer. The protective layer can comprise a hydrophilic polymer. Some selectively permeable elements can be in the form of a membrane. In some embodiments, the fluid passing through the selectively permeable element travels through all of its components regardless of whether they are in physical communication or their order of arrangement. Some non-limiting examples of a gas permeable element 100 may be configured as depicted in Figures 1 and 2. For example, as depicted in FIG. 1, selectively permeable membrane element 100 can include porous support 120. Composite 110 is coated onto porous support 120. In some embodiments, as shown in Figure 2, the element may further comprise a protective coating, 140. In some embodiments, the porous support or substrate may be sandwiched between two composite layers.

In some embodiments, the gas permeable element selectively allows certain gas species to pass through while retaining the remaining gas species. In some embodiments, the gas upstream of the membrane element can comprise a mixture of C0₂ and another gas. In some embodiments, the other gas can comprise N₂, air, or reducing gases. In some embodiments, the gas in the downstream of the membrane element can contain an increased molar fraction of C0₂, as compared to the molar fractions of C0₂ in the gas in the upstream of the membrane element. In some embodiments, as a result of the layers, the element may provide a durable gas removal system that can be used to remove C0₂ from other gases such as N₂, air, or reducing gases.

In some embodiments, the element can exhibit a C0₂ permeability of about 1- 150 barrer, about 5-100 barrer, about 10-95 barrer, about 15-95 barrer, about 10-50 barrer, about 10-20 barrer, about 20-30 barrer, about 30-40 barrer, about 40-45 barrer, about 40-50 barrer, about 16.5 barrer, about 32.5 barrer, about 39.2 barrer, about 40.3 barrer, about 41.5 barrer, or any permeability in a range bounded by any of these values. In some embodiments, the element can exhibit an N₂ permeability of about 0.1-

10 barrer, about 0.2-5 barrer, about 0.3-2.5 barrer, about 0.4-1.0 barrer, about 0.4-0.7 barrer, about 0.9-1.0 barrer, about 0.41 barrer, about 0.69 barrer, about 0.91 barrer, about 0.97 barrer, about 0.98 barrer, or any permeability in a range bounded by any of these values. In some embodiments, an element may be selectively permeable. In some embodiments, the element can have a high selectivity of C0₂ in permeability over N₂. In some embodiments, the selectivity of C0₂ to N₂ (non-dimensional ratio of C0₂ permeability to N₂ permeability) can be about 8-100 fold, about 20-70 fold; about 30- 65 fold, about 30-40 fold, about 40-45 fold, about 40-50 fold, 50-60 fold, about 55-65 fold, about 33.3 fold, about 39.9 fold, about 40.6 fold, about 44.3 fold, about 60.2 fold, or any selectivity in a range bounded by any of these values. III. GO-Polymer-Based Composite.

The elements described herein comprise a GO-based polymeric composite. The GO-based composite comprises a graphene oxide material and a polymer, wherein the graphene oxide material can be distributed or dispersed in the polymer matrix. The polymer can comprise a polyether block amide. The graphene oxide can be functionalized.

The GO-based composite can be in a layer form with any suitable thickness. For example, some GO-based composite layers may have a thicknesses of about 5-2000 nm, about 5-1000 nm, about 1000-2000 nm, about 10-500 nm, about 500-1000 nm, about 50-500 nm, about 50-400 nm, about 600-1000 nm, about 600-800 nm, about 500-7000 nm, about 600-6500 nm, about 2000-3000 nm, about 6000-6500 nm, about 100 nm, about 200 nm, about 250 nm, about 300 nm, about 600 nm, about 800 nm, about 2000 nm, about 2600 nm, about 6400 nm, or any thickness in a range bounded by any of these values.

A. Graphene Oxide In general, graphene-based materials have many attractive properties, such as a 2-dimensional sheet-like structure with extraordinary high mechanical strength and nanometer scale thickness. Graphene oxide (GO), an exfoliated oxidation of graphite, can be mass produced at low cost. With its high degree of oxidation, graphene oxide has high water permeability and also exhibits versatility to be chemically modified in structure to have many functional groups, such as an amino-group or a hydroxyl group or a combination thereof to form functionalized graphene oxide (FGO). A graphene oxide material may be optionally substituted. In some embodiments, the optionally substituted graphene oxide may contain a graphene which has been chemically modified, or functionalized. Functionalized graphene oxide includes one or more functional groups not present in graphene oxide, such as functional groups that are not OH, COOH or epoxide group directly attached to a C- atom of the graphene base. Examples of functional groups that may be present in functionalized graphene include halogen, alkene, alkyne, cyano, ester, amide, or amine. In some embodiments, the graphene oxide can be functionalized by an amine. In some embodiments, the amine can be a diamine, such as an alkyldiamine. In some embodiments, the alkyldiamine can be substituted at a terminal position, or may be a terminal substituted alkyldiamine. In some embodiments, the alkyldiamine can be substituted by two methyl groups, or may be a dimethyl alkyldiamine. In some embodiments, the dimethyl alkyldiamine can comprise (2- (dimethylamino)ethyl)amine-yl with structure represented by Formula 1 below:

It is believed that there may be a large number (~30%) of epoxy groups on GO, which may be readily reactive with amine groups at elevated temperatures. In some embodiments, one or more functional groups can covalently attach to the graphene oxide. In some embodiments, one or more functional groups can react to an epoxide group on the surface of the graphene oxide. A possible representative example of (2- (dimethylamino)ethyl)amine-yl functionalized graphene may be depicted as the following:

In some embodiments, at least about 99%, at least about 95%, at least about 90%, at least about 80%, at least about 70%, at least about 60%, at least about 50%, at least about 40%, at least about 30%, at least about 20%, at least about 10%, or at least about 5% of the graphene oxide molecules may be functionalized. In some embodiments, the functionalized graphene oxide material may provide selective permeability for gases, fluids, and/or vapors.

In some embodiments, the graphene oxide material may be in the form of sheets, planes or flakes. In some embodiments, the graphene material may have a surface area of about 100-5000 m²/g, about 150-4000 m²/g, about 200-1000 m²/g, about 500-1000 m²/g, about 1000-2500 m²/g, about 2000-3000 m²/g, about 100-500 m²/g, about 400-500 m²/g, or any surface area in a range bounded by any of these values.

In some embodiments, the graphene oxide material may be in the form of platelets having 1, 2, or 3 dimensions with size of each dimension independently in the nanometer to micron range. In some embodiments, the graphene material may have a platelet size in any one of the dimensions, or may have a square root of the area of the largest surface of the platelet, of about 0.05-100 μιτι, about 0.05-50 μιτι, about 0.1- 50 μιτι, about 0.5-10 μιτι, about 1-5 μιτι, about 0.1-2 μιτι, about 1-3 μιτι, about 2-4 μιτι, about 3-5 μιτι, about 4-6 μιτι, about 5-7 μιτι, about 6-8 μιτι, about 7-10 μιτι, about 10- 15 μιτι, about 15-20 μιτι, about 50-100 μιτι, about 60-80 μιτι, about 50-60 μιτι, about 25-50 μιτι, or any platelet size in a range bounded by any of these values.

In some embodiments, the graphene oxide material can comprise at least 70%, at least 75%, at least 80%, at least 85%, at least 90%, at least 95%, at least 97%, or at least 99% of graphene material having a molecular weight of about 5,000 Daltons (Da) to about 200,000 Da.

In some embodiments, the mass percentage of the diamine relative to the total mass of the diamine-functionalized graphene oxide, is about 0.1-1%; about 1-5%, about 5-10%; 10-50 wt%, about 10-30 wt%, about 20-40 wt%, about 30-50 wt%, about 15-25 wt%, about 20-30 wt%, about 25-35 wt%, about 30-40%, about 40-50%, about 50-60%, about 55-60%, or any weight percent in a range bounded by any of these values.

In some embodiments, the diamine-functionalized graphene oxide has a nitrogen mass that, relative to the total mass of the diamine-functionalized graphene oxide, that is about 4-8%, about 4-5%, about 4.5-5.5%, about 5-6%, about 5-7%, about 5.9-6.4%, about 6-6.5%, about 6.1-6.6%, 6-6.2%, about 6.3-6.8%, about 5.5-6.5%, about 6-7%, about 6.5-7.5%, about 7-8%, about 6.1%, or any mass percent in a range bounded by any of these values.

In some embodiments, the mass percentage of the graphene oxide material relative to the total mass or weight of the GO-based composite can be about 0.1-10 wt%, about 0.15-5 wt%, about 0.2-2.5 wt%, about 0.25-2.0 wt%, about 0.3-1.5 wt%, about 0.5-1.0 wt%, about 0.1-0.5 wt%, about 0.3-0.7 wt%, about 0.5-0.9 wt%, about 0.7-1.1 wt%, about 0.9-1.3 wt%, about 1-1.5 wt%, about 0.5 wt%, about 1 wt%, or any mass percentage in a range bonded by any of these values. B. Polymer

In some embodiments, the GO-based composite can comprise a polymer. The polymer can comprise a thermoplastic elastomer. The thermoplastic elastomer can comprise a block amide of nylon and polyether, or a polyether block amide. The polyether block amide can comprise a block copolymer of a polyamide with a hydroxyl- terminated polyether. In some embodiments, the thermoplastic elastomer moieties can be crosslinked, or covalently bonded, with themselves to form a polymer matrix. In some embodiments, some of the thermoplastic elastomer moieties can be crosslinked while others may be only in physical contact without crosslinking. In some embodiments, the graphene oxide material can be physically suspended within the polymer matrix. some embodiments, the block copolymer can be obtained polycondensation of one or more polyamides and one or more polyethers. In some embodiments, the polyamide can comprise a polyamide A represented by - NH(CH₂)x-iCO- wherein x is 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 such as polyamide A6 ( -NH(CH₂)₅CO-), polyamide All ( -NH(CH₂)i₀CO-), polyamide A12 ( -NH(CH₂)nCO-), or a polyamide B represented by - NH(CH₂)xNHCO(CH₂)y-₂CO- wherein x is 3-20, such as 3, 3-4, 4-5, 5-6, 6-7, 7-8, 8-9, 9- 10, 10-11, 11-12, 12-13, 13-14, 14-15, 15-16, 16-17, 17-18, 18-19, 19-20, or 20, and y is 3-20, such as 3, 3-4, 4-5, 5-6, 6-7, 7-8, 8-9, 9-10, 10-11, 11-12, 12-13, 13-14, 14-15, 15-16, 16-17, 17-18, 18-19, 19-20, or 20, such as polyamide B6/12 (- NH(CH₂)6NHCO(CH₂)ioCO-). In some embodiments, the polyamide segment can range from about 1 polyamide to about 50 polyamides long. In some embodiments, the hydroxyl-terminated polyether can comprise a polyether of poly(tetramethylene oxide) (H-(OCH₂-CH₂-CH₂-CH₂)_z-OH)or polyethylene oxide (H-(OCH₂-CH₂)_z-OH), wherein z is about 1 to about 100. In some embodiments, the polyether block amide can be described by the trade names PEBAX^® (Arkema, Colombes, France) and/or VESTAMID^® E Evonik Industries, Marl, Germany), such as PEBAX MH 1657 (e.g.,

The molecular weight of the thermoplastic elastomer may be about 100- 1,000,000 Da, about 10,000-500,000 Da, about 10,000-50,000 Da, about 50,000- 100,000 Da, about 70,000-120,000 Da, about 80,000-130,000 Da, about 90,000- 140,000 Da, about 90,000-100,000 Da, about 95,000-100,000 Da, about 98,000 Da, or any molecular weight in a range bounded by any of these values.

IV. Porous Support.

A porous support may be any suitable material and in any suitable form upon which a layer, such as a layer of a GO-based composite, may be deposited or disposed. In some embodiments, the porous support can comprise hollow fibers or porous material. Some porous supports can comprise a non-woven fabric. In some embodiments, the porous material can be a polymer. The polymer may be polyamide (Nylon), polyimide (PI), polyvinylidene fluoride (PVDF), polyethylene (PE), polyethylene terephthalate (PET), polysulfone (PSF), polyether sulfone (PES), and/or mixtures thereof. In some embodiments, the porous support is PSF. In some embodiments, the porous support is PVDF.

V. Protective Coating.

Some elements may further comprise a protective coating. For example, the protective coating can be disposed on top of the selectively permeable element to protect it from the environment. The protective coating may have any composition suitable for protecting the selectively permeable element from the environment. Many polymers are suitable for use in a protective coating such as one or a mixture of hydrophilic polymers, e.g. polyvinyl alcohol (PVA), polyvinyl pyrrolidone (PVP), polyethylene glycol (PEG), polyethylene oxide (PEO), polyoxyethylene (POE), polyacrylic acid (PAA), polymethacrylic acid (PMMA), polyacrylamide (PAM), polyethylenimine (PEI), poly(2-oxazoline), polyethersulfone (PES), methyl cellulose (MC), chitosan, poly (allylamine hydrochloride) (PAH), poly (sodium 4-styrene sulfonate) (PSS), and any combinations thereof. Some protective coatings can comprise PVA. VI. Gas Separation Device.

Some embodiments include a gas separation device. The device can comprise a wall separating a first plenum containing a first gas and a second plenum containing a second gas, wherein the first gas is unprocessed and the second gas is processed. In some embodiments, the wall can define an aperture allowing fluid communication between the first gas in the first plenum and the second gas in the second plenum. In some embodiments, a selectively permeable gas element can occlude the aperture such that all fluid communication between the first and second plena must go through the selectively permeable membrane element. In some embodiments, the element can comprise any of the aforementioned selectively gas permeable elements. The device may selectively allow C0₂ gas to pass between the plena.

VII. Methods of Fabricating Selectively Gas Permeable Elements.

Some embodiments include methods for making any one of the aforementioned selectively gas permeable elements comprising: (a) obtaining a functionalized graphene oxide material, (b) mixing the graphene oxide material and a polyether block amide in an aqueous liquid to generate a composite mixture; (c) applying the composite mixture to a porous support to achieve a coated support; and (d) curing the coated support. In some embodiments, the step of applying the mixture to a porous support can be repeated as necessary to achieve the desired thickness of the composite layer that is about 0.1-10 μιτι. In some methods, the selectively gas permeable element can further comprise a protective layer. An example of one possible method of making elements is shown in Figure 3. In some embodiments, the step of obtaining a functionalized graphene oxide material can comprise generating a diamine-functionalized graphene oxide material. In some methods, functionalizing the graphene oxide comprises mixing the graphene oxide with an alkyldiamine and allowing them to react at certain conditions. The alkyldiamine can be substituted at terminal. The alkyldiamine can be substituted at terminal by two methyl groups to generate dimethyl alkyldiamine, such as N^N¹- dimethylethane-l,2-diamine. In some methods, reacting the graphene oxide and the alkyldiamine can be achieved by heating the reaction mixture at an elevated temperature of about 30 °C, about 40 °C, about 50 °C, about 60 °C, about 70 °C, about 80 °C, to about 90 °C, such as about 60 °C; for a duration of about 4 hours to about 24 hours, such as about 16 hours. In some embodiments, the step of heating also comprises stirring the mixture. After heating, the reaction mixture can be further cooled to room temperature followed by quenching the reaction with an alcohol, such as isopropyl alcohol. Some methods can further comprise purifying the products of the reaction, which results in a functionalized graphene oxide material.

In some embodiments, the step of mixing graphene oxide material and a polyether block amide in an aqueous liquid to generate a composite mixture can be accomplished by dissolving appropriate amounts of functionalized graphene oxide material and polyether block amide in water. The polyether block amide can comprise any of the aforementioned block copolymers of polyamide and a hydroxyl-terminated polyether. Some methods comprise mixing at least two separate aqueous liquids, e.g., a functionalized graphene oxide based liquid and a polyether block amide based liquid inappropriate mass ratios to achieve the desired results. Some methods comprise creating one aqueous mixture by dissolving appropriate amounts of graphene oxide material and polyether block amide together in the same aqueous liquid. The resulting mixture can be agitated at temperatures and times sufficient to ensure uniform dissolution of the solute to generate a composite coating mixture. In some embodiments, applying the composite coating mixture to the porous support can be done by methods known in the art for creating a layer of desired thickness. In some embodiments, applying the coating mixture to the support or substrate can be achieved by vacuum immersing the substrate into the coating mixture first, and then drawing the solution onto the substrate by applying a negative pressure gradient across the substrate until the desired coating thickness can be achieved. In some embodiments, applying the coating mixture to the substrate can be achieved by casting, blade coating, spray coating, dip coating, die coating, or spin coating. Some methods can further comprise gently rinsing the substrate with deionized water after each application of the coating mixture to remove excess loose material. In some embodiments, the coating is done such that a composite layer of a desired thickness is created. The desired thickness of the composite layer can range from about 0.1-10 μιτι, about 0.2-8 μιτι, about 0.5-7 μιτι, about 0.6-6.4 μιτι, about 0.6 μιτι, about 0.8 μιτι, about 2.0 μιτι, about 2.6 μιτι, about 4.8 μιτι, or about 6.4 μιτι. This process results in a fully coated substrate, or a coated support.

For some methods, the curing of the coated support can be done at certain temperatures for certain times sufficient enough to form a dry selectively gas permeable element. In some embodiments, the coated support can be heated at a temperature of about 10-100 °C, about 20-50 °C, about 23 °C, or about room temperature. In some embodiments, the heating can be done for a duration of about 30 seconds, about 1 minute, about 15 minutes, about 30 minutes, about 1 hour, about 3 hours, about 5 hours, or until dry. In some embodiments, the coated substrate can be cured at room temperature or at 23 °C until dry.

In some embodiments, the method for fabricating a selectively gas permeable element further comprises subsequently applying a protective coating on the element. In some embodiments, the applying a protective coating comprises adding a hydrophilic polymer layer. In some embodiments, applying a protective coating comprises coating the element with a polyvinyl alcohol aqueous solution. Applying a protective layer can be achieved by methods such as blade coating, spray coating, dip coating, spin coating, and etc. In some embodiments, applying a protective layer can be achieved by dip coating of the element in a protective coating solution for about 1- 10 minutes, about 1-5 minutes, about 5 minutes, or about 2 minutes. In some embodiments, the method further comprises drying the element at about 75-120 °C for about 5-15 minutes, or at about 90 °C for about 10 minutes. This process results is a selectively gas permeable element with a protective coating.

EMBODIMENTS

The following embodiments are specifically contemplated: Embodiment 1. A gas permeable membrane element comprising:

a porous support; and

a composite coated on the porous support, wherein the composite comprises a diamine-functionalized graphene oxide material and a polyether block amide, wherein the diamine-functionalized graphene oxide material is distributed within the polyether block amide; and

wherein the gas permeable membrane element is selectively permeable to C0₂ gas.

Embodiment 2. The gas permeable membrane element of embodiment 1, wherein the porous support is a non-woven fabric. Embodiment s. The gas permeable membrane element of embodiment 1 or 2, wherein the porous support comprises polyamide, polyimide, polyvinylidene fluoride, polyethylene, polyethylene terephthalate, polysulfone, or polyether sulfone.

Embodiment 4. The gas permeable membrane element of embodiment 1, 2, or 3, wherein the porous support is polysulfone (PSF). Embodiment 5. The gas permeable membrane element of embodiment 1, 2, or 3, wherein the porous support is polyvinylidene fluoride (PVDF). Embodiment 6. The gas permeable membrane element of embodiment 1, 2, 3, 4, or 5, wherein the diamine-functionalized graphene oxide comprises a graphene oxide with one or more functional groups of dimethyl alkyldiamine.

Embodiment 7. The gas permeable membrane element of embodiment 6, wherein the dimethyl alkyldiamine comprises 2-dimethylaminoethylamine-yl with structure represented by:

Embodiment s. The gas permeable membrane element of embodiment 6, wherein the mass percentage of diamine-functionalized graphene oxide to the total composite is about 0.1 wt% to about 10 wt%.

Embodiment 9. The gas permeable membrane element of embodiment 6, wherein the mass percentage of diamine-functionalized graphene oxide to the total composite is about 0.5 wt% to about 1 wt%.

Embodiment 10. The gas permeable membrane element of embodiment 6, wherein the mass percentage of diamine-functionalized graphene oxide to the total composite is about 0.5 wt%.

Embodiment 11. The gas permeable membrane element of embodiment 6, wherein the mass percentage of diamine-functionalized graphene oxide to the total composite is about 1 wt%. Embodiment 12. The gas permeable membrane element of embodiment 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, or 11, wherein the polyether block amide comprises a block co-polymer of a polyamide and a hydroxyl-terminated polyether.

Embodiment 13. The gas permeable membrane element of embodiment 12, where the polyamide comprises a polyamide A represented by the formula: -N H(CH2)x iCO- wherein x is from 2 to 20. Embodiment 14. The gas permeable membrane element of embodiment 12, where the polyamide comprises a polyamide B represented by the formula: - N H(CH2)xN HCO(CH2)y-2CO- wherein x and y are independently from 3 to 20.

Embodiment 15. The gas permeable membrane element of embodiment 12, where the hydroxyl-terminated polyether comprises a poly(tetramethylene oxide) represented by the formula: H-(0(CH2)4)z-OH, wherein z is from 1 to 100.

Embodiment 16. The gas permeable membrane element of embodiment 12, wherein the hydroxyl-terminated polyether comprises a polyethylene oxide represented by the formula: H-(OCH2CH2)z-OH, wherein z is from 1 to 100. Embodiment 17. The gas permeable membrane element of embodiment 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, or 16, the composite is in a form of layer that has a thickness of about 0.1 μιτι to about 10 μιτι.

Embodiment 18. The gas permeable membrane element of embodiment 17, the composite is in a form of layer that has a thickness of about 0.6 μιτι to about 6.4 μιτι. Embodiment 19. The gas permeable membrane element of embodiment 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, or 18, further comprising a protective coating.

Embodiment 20. The gas permeable membrane element of embodiment 19, wherein the protective coating is disposed on the top of the gas permeable membrane. Embodiment 21. The gas permeable membrane element of embodiment 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20, having reduced N₂ permeability and enhanced CO2 selectivity in permeability over N2.

Embodiment 22. The gas permeable membrane element of embodiment 21, having reduced N2 permeability by at least 50%. Embodiment 23. The gas permeable membrane element of embodiment 21, having reduced N2 permeability by about 80% or more. Embodiment 24. The gas permeable membrane element of embodiment 21, having enhanced C0₂ selectivity in permeability over N₂ by at least 30-fold.

Embodiment 25. The gas permeable membrane element of embodiment 21, having enhanced C0₂ selectivity in permeability over N₂ by about 60-fold. Embodiment 26. A gas separation device comprising: the gas permeable membrane element of embodiment 1 in fluid communication with: 1) a first plenum containing a first gas, and 2) a second plenum containing a second gas, wherein the gas permeable membrane element selectively allows C0₂ gas to pass from the first plenum to the second plenum. Embodiment 27. A method of making a gas permeable element comprising:

curing an aqueous mixture that is coated onto a porous support;

wherein the aqueous mixture that is coated onto the porous support is cured at room temperature until dry;

wherein the porous support is coated with the aqueous mixture by applying the aqueous mixture to the porous support, and repeating as necessary to achieve a layer having a thickness of about 0.1 μιτι to about 10 μιτι; and

wherein the aqueous mixture is formed by mixing a diamine-functionalized graphene oxide material and a polyether block amide in an aqueous liquid.

Embodiment 28. The method of embodiment 27, wherein the diamine- functionalized graphene oxide material is obtained by mixing graphene oxide and a dimethyl alkyldiamine in an aqueous liquid followed by heating the resulting mixture at about 30 °C to about 90 °C for about 4 hours to about 24 hours, then cooling the mixture to room temperature, and finally quenching the mixture in an alcohol.

Embodiment 29. The method of c embodiment 28, wherein the dimethyl alkyldiamine comprises N¹,N¹-dimethylethane-l,2-diamine. Embodiment 30. The method of embodiment 27, wherein the polyether block amide comprises a block co-polymer of a polyamide and a hydroxyl-terminated polyether.

Embodiment 31. The method of embodiment 27, wherein the porous support is polysulfone (PSF) or polyvinylidene fluoride (PVDF).

EXAMPLES

Embodiments of the selectively gas permeable elements described herein have improved performance as compared to other selectively permeable membranes. These benefits are further demonstrated by the following examples, which are intended to be illustrative of the disclosure, but are not intended to limit the scope or underlying principles in any way.

Example 1.1.1: Preparation of Coating Mixture.

Graphene Oxide (GO) Solution Preparation: GO was prepared from graphite using the modified Hummers method. Graphite flakes (2.0 g) (Sigma Aldrich, St. Louis, MO, USA, 100 mesh) were oxidized in a mixture of 2.0 g of NaN0₃ (Aldrich), 10 g KMn0₄ of (Aldrich) and 96 mL of concentrated H₂S0₄ (Aldrich, 98%) at 50 °C for 15 hours. The resulting paste like mixture was poured onto 400 g of ice followed by adding 30 mL of hydrogen peroxide (Aldrich, 30%). The resulting solution was then stirred at room temperature for 2 hours to reduce the manganese dioxide, then filtered through a filter paper and washed with Dl water. The solid was collected and then dispersed in Dl water with stirring, centrifuged at 6300 rpm for 40 minutes, and the aqueous layer was decanted. The remaining solid was then dispersed in Dl water again and the washing process was repeated 4 times. The purified GO was then dispersed in Dl water under sonication (power of 10 W) for 2.5 hours to get the GO dispersion (0.4 wt%) as GO-1. GO Functionalization: To a GO dispersion in water (0.4 g in 100 mL) was added N¹,N¹-dimethylethane-l,2-diamine (1.2 g, Aldrich). The resulting mixture was stirred at 60 °C for 16 hours and then cooled. After cooling to room temperature, the entire mixture was then poured into isopropanol (500 mL, Aldrich) to give black precipitate. The resulting precipitate was then filtered, washed with isopropanol (Aldrich), and then dried under vacuum to afford 500 mg of a solid. Elemental analysis: Calc'd: C, 57.32; H, 4.20; N, 6.37; Found: C, 57.55; H, 4.04; N, 6.10. The resulting GO was then dispersed in Dl water (100 mL) under sonication (power of 10 W) for 2.5 hours to get the functionalized GO dispersion (0.4 wt%) as FGO-1. Preparation of Polyether Block Amide (PEBAX) Solution: To a 500 mL solution of 70 wt% ethanol (Aldrich) in Dl water was added polyether block amide (PEBAX 1657, Arkema, Colombes, France) to create a 2.5 wt% solution. The resulting solution was then stirred on a hot plate at 60 °C until fully dissolved to create a polymer solution PEBAX-1. Preparation of Coating Mixture CS-1: GO-1 (1 mL) and PEBAX-1 (16 mL) solutions were mixed and sonicated for 1 hour to ensure uniform mixing to create a coating solution (CS-1).

Example 2.1.1: Preparation of a Gas Permeable Membrane.

Mixture Application: The coating mixture (CS-1) was then knife cast onto the pretreated PSF substrate (Hydranautics, San Diego, CA USA) using a die caster (Taku- Die 200, Die-Gate Co., Ltd., Tokyo, Japan), setting the knife thickness such that a layer was deposited on the support that would be 2.5 μιτι when dry. The resulting membrane was then dried at room temperature. This process generated a gas separation membrane (MD-1.1.1). Example 2.1.1.1: Preparation of Additional Gas Permeable Membranes. Additional membranes were constructed using the methods similar to Example 1.1.1 and Example 2.1.1, with the exception that parameters were varied as shown in Table 1. Specifically, individual concentrations were varied, and the knife coating was adjusted to vary the dry thickness of the membrane. Additionally for some embodiments a second-type of support, PVDF (CS Hyde Co., Lake Villa, IL USA), was used instead of PSF.

When membranes were identified as coated with die coating instead of filtering, the procedure was varied as follows. Instead of filtration, the coating solution was deposited on the membrane surface using a die caster (Taku-Die 200, Die-Gate Co., Ltd., Tokyo, Japan), which was set to create the desired coating thickness.

Table 1: Gas Separation Membranes.

Curing

FGO GO PEBAX Coating Thickness

Membrane Support

(wt%) Temp Time

(wt%) (wt%) Method (μηι)

(°C) (min)

Note: Membrane Numbering Scheme is MD-J.K.L, or CMD-J.K.L, wherein

J = 1 - no protective coating; 2 - protective coating

K = category of membrane

L = membrane # within category

Comparative Example 2.2.1: Preparation of Comparative Membranes.

A comparative gas permeable membrane (CMD-1.1.1) was created using methods similar to those used in Example 2.1.1 with the exception that a non- functionalized graphene oxide, GO-1 was used instead of functionalized graphene oxide, FGO-1, and the thickness was varied as shown in Table 1.

Two additional comparative membranes, CMD-1.2.1 and CMD-1.2.2, were also created which contained the bare substrates (e.g., PSF and PVDF respectively) coated with PEBAX alone without GO or FGO. Example 2.2.2: Preparation of a Membrane with a Protective Coating (Prophetic).

Any of the membranes can be coated with protective layers. First, a PVA solution of 2.0 wt% can be prepared by stirring 20 g of PVA (Aldrich) in 1 L of Dl water at 90 "C for 20 minutes until all the granules dissolved. The solution can then be cooled to room temperature. The selected substrates can be immersed in the solution for 10 minutes and then removed. Excess solution remaining on the membrane can then be removed by paper wipes. The resulting assembly can then be dried in an oven (DX400, Yamato Scientific) at 90 °C for 30 minutes. A membrane with a protective coating can thus be obtained.

Example 3.1: Performance Testing of Selected Membranes. Gas Permeability Testing: The selective gas permeability of GO-based membrane for C0₂ was found to be high as compared to other gases, such as N₂. To determine the selective gas permeability an experimental setup similar to the one depicted in Figure 4 was used. First, the sample to be measured was first enclosed in a filter pressure test stand (stainless steel, 47 mm dia., XX45 047 00, Millipore, Billerica, MA USA). The test stand was set up such that it was placed in fluid communication between two vacuum cylinders (150 mL, 316L-HDF4-150, Swagelok, San Diego, CA USA) via an isolation valves. The upstream vacuum cylinder was in fluid communication with a gas source via a tee and isolation valve, where the gas source allows reconfiguration to different species of gases. The tee further is in fluid communication to a vacuum pump via an isolation valve which allows for the evacuation the upstream cylinder before testing. The downstream cylinder is in fluid communication with a vacuum pump via an isolation valve. The downstream cylinder is in further fluid communication with the vacuum pump via yet another isolation valve that allows evacuation of the downstream cylinder and then isolation before testing. Both upstream and downstream vacuum cylinders are instrumented to read the cylinder pressures via an upstream gauge (MG1-100-9V, SSI Technologies, Janesville, Wl USA) and a downstream gauge (DG25, Ashcroft Inc., Stratford, CT USA).

To prepare a sample for testing, once a sample is secured in the test stand, the tee-valve is set to vacuum and so does the isolation values to the downstream vacuum so that the residual gas in the entire test section can be evacuated. Once the residual gas is evacuated, the test section isolation valves are closed to isolate the test section. The tee-valve is then switched to the gas source of the desired gas to be tested. The downstream vacuum cylinder is then isolated from the vacuum pump to create a downstream vacuum condition. The upstream vacuum cylinder is then filled with the desired pressure of gas to be measured and then isolated from the gas source, to create an upstream pressure condition. Then, at the beginning of measuring, the two isolation valves on each side of the test stand are opened and the gas is allowed to pass from the upstream pressure condition through the gas membrane to the downstream vacuum condition. The change in pressures as a function of time can then be used to determine the volumetric flow rate. To test the permeability of nitrogen gas, the difference in upstream vacuum cylinder was set to about 1 bar above atmospheric pressure, and downstream pressure was set to a vacuum or approximately zero bar such that the pressure differential across the membrane was about 1500 torr, or 2 bar. Similarly the test was repeated for C0₂ as the subject gas.

Based on the rise of the downstream pressure as a function of time, the flow rates and permeability of the gas species tested through the membrane can be calculated. Membrane selectivity can be further calculated by comparing permeability of different gases. The testing results are shown in Table 2. From the results shown in Table 2, it appears that the addition of graphene oxide (GO) not only reduces the N₂ permeability, but also reduces any C0₂ selectivity that the polyether block amide (PEBAX) may inherently have (e.g. comparing CMD-1.1.1 with CMD-1.2.1). Surprisingly, however, when diamine-functionalized graphene oxide (FGO) is used together with the polyether block amide (PEBAX), most of the resulting membranes have both reduced N₂ permeability and enhanced C0₂ selectivity (e.g. comparing MD- 1.1.1, MD-1.2.1, or MD-1.2.2 with CMD-1.1.1). An examination based on the membrane thickness did not reveal any overall trends, indicating that the material differences are the primary reason for resulting in the differences in permeability and selectivity of the different membranes.

Table 2: Membrane Gas Permeability Performance.

Unless otherwise indicated, all numbers expressing quantities of ingredients, properties such as molecular weight, reaction conditions, and etc. used in herein are to be understood as being modified in all instances by the term "about." Each numerical parameter should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques. Accordingly, unless indicated to the contrary, the numerical parameters may be modified according to the desired properties sought to be achieved, and should, therefore, be considered as part of the disclosure. At the very least, the examples shown herein are for illustration only, not as an attempt to limit the scope of the disclosure. The terms "a," "an," "the" and similar referents used in the context of describing embodiments of the present disclosure (especially in the context of the following claims) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. All methods described herein may be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g., "such as") provided herein is intended merely to better illustrate embodiments of the present disclosure and does not pose a limitation on the scope of any claim. No language in the specification should be construed as indicating any non-claimed element essential to the practice of the embodiments of the present disclosure.

Groupings of alternative elements or embodiments disclosed herein are not to be construed as limitations. Each group member may be referred to and claimed individually or in any combination with other members of the group or other elements found herein. It is anticipated that one or more members of a group may be included in, or deleted from, a group for reasons of convenience and/or patentability.

Certain embodiments are described herein, including the best mode known to the inventors for carrying out the embodiments. Of course, variations on these described embodiments will become apparent to those of ordinary skill in the art upon reading the foregoing description. The inventor expects skilled artisans to employ such variations as appropriate, and the inventors intend for the embodiments of the present disclosure to be practiced otherwise than specifically described herein. Accordingly, the claims include all modifications and equivalents of the subject matter recited in the claims as permitted by applicable law. Moreover, any combination of the above-described elements in all possible variations thereof is contemplated unless otherwise indicated herein or otherwise clearly contradicted by context.

In closing, it is to be understood that the embodiments disclosed herein are illustrative of the principles of the claims. Other modifications that may be employed are within the scope of the claims. Thus, by way of example, but not of limitation, alternative embodiments may be utilized in accordance with the teachings herein. Accordingly, the claims are not limited to embodiments precisely as shown and described.

Claims

CLAIMS What is claimed is:

1. A gas permeable membrane element comprising:

a porous support; and

2. The gas permeable membrane element of claim 1, wherein the porous support is a non-woven fabric.

3. The gas permeable membrane element of claim 1 or 2, wherein the porous support comprises polyamide, polyimide, polyvinylidene fluoride, polyethylene, polyethylene terephthalate, polysulfone, or polyether sulfone.

4. The gas permeable membrane element of claim 1, 2, or 3, wherein the porous support is polysulfone (PSF).

5. The gas permeable membrane element of claim 1, 2, or 3, wherein the porous support is polyvinylidene fluoride (PVDF).

6. The gas permeable membrane element of claim 1, 2, 3, 4, or 5, wherein the diamine-functionalized graphene oxide comprises a graphene oxide with one or more functional groups of dimethyl alkyldiamine.

7. The gas permeable membrane element of claim 6, wherein the dimethyl alkyldiamine comprises 2-dimethylaminoethylamine-yl with structure represented by:

8. The gas permeable membrane element of claim 6, wherein the mass percentage of diamine-functionalized graphene oxide to the total composite is about 0.1 wt% to about 10 wt%.

9. The gas permeable membrane element of claim 6, wherein the mass percentage of diamine-functionalized graphene oxide to the total composite is about 0.5 wt% to about 1 wt%.

10. The gas permeable membrane element of claim 6, wherein the mass percentage of diamine-functionalized graphene oxide to the total composite is about 0.5 wt%.

11. The gas permeable membrane element of claim 6, wherein the mass percentage of diamine-functionalized graphene oxide to the total composite is about 1 wt%.

12. The gas permeable membrane element of claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, or 11, wherein the polyether block amide comprises a block co-polymer of a polyamide and a hydroxyl-terminated polyether.

13. The gas permeable membrane element of claim 12, where the polyamide comprises a polyamide A represented by the formula: -N H(CH2)x-iCO-, wherein x is from 2 to 20.

14. The gas permeable membrane element of claim 12, where the polyamide comprises a polyamide B represented by the formula: -N H(CH2)xN HCO(CH2)y-2CO-, wherein x and y are independently from 3 to 20.

15. The gas permeable membrane element of claim 12, where the hydroxyl- terminated polyether comprises a poly(tetramethylene oxide) represented by the formula: H-(0(CH₂)4)z-OH, wherein z is from 1 to 100.

16. The gas permeable membrane element of claim 12, wherein the hydroxyl- terminated polyether comprises a polyethylene oxide represented by the formula: H- (OCH₂CH₂)z-OH, wherein z is from 1 to 100.

17. The gas permeable membrane element of claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, or 16, the composite is in a form of layer that has a thickness of about

0.1 μιτι to about 10 μιτι.

18. The gas permeable membrane element of claim 17, the composite is in a form of layer that has a thickness of about 0.6 μιτι to about 6.4 μιτι.

19. The gas permeable membrane element of claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, or 18, further comprising a protective coating.

20. The gas permeable membrane element of claim 19, wherein the protective coating is disposed on the top of the gas permeable membrane.

21. The gas permeable membrane element of claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20, having reduced N₂ permeability and enhanced C0₂ selectivity in permeability over N₂.

22. The gas permeable membrane element of claim 21, having reduced N₂ permeability by at least 50%.

23. The gas permeable membrane element of claim 21, having reduced N₂ permeability by about 80% or more.

24. The gas permeable membrane element of claim 21, having enhanced C0₂ selectivity in permeability over N₂ by at least 30-fold.

25. The gas permeable membrane element of claim 21, having enhanced C0₂ selectivity in permeability over N₂ by about 60-fold.

26. A gas separation device comprising: the gas permeable membrane element of claim 1 in fluid communication with: 1) a first plenum containing a first gas, and 2) a second plenum containing a second gas, wherein the gas permeable membrane element selectively allows C0₂ gas to pass from the first plenum to the second plenum.

27. A method of making a gas permeable element comprising:

curing an aqueous mixture that is coated onto a porous support;

28. The method of claim 27, wherein the diamine-functionalized graphene oxide material is obtained by mixing graphene oxide and a dimethyl alkyldiamine in an aqueous liquid followed by heating the resulting mixture at about 30 °C to about 90 °C for about 4 hours to about 24 hours, then cooling the mixture to room temperature, and finally quenching the mixture in an alcohol.

29. The method of claim 28, wherein the dimethyl alkyldiamine comprises N^N¹- dimethylethane-l,2-diamine.

30. The method of claim 27, wherein the polyether block amide comprises a block co-polymer of a polyamide and a hydroxyl-terminated polyether.

31. The method of claim 27, wherein the porous support is polysulfone (PSF) or polyvinylidene fluoride (PVDF).