Reverse selective o 2 / h 2 membranes

Abstract

An exemplary embodiment of the present disclosure provides a reverse selective O2 / H2 (RSOH) membrane having an O2 / H2 permselectivity of greater than unity.

Description

REVERSE SELECTIVE O2 / H2 MEMBRANESCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. Provisional Application Serial No. 63 / 531,668, filed on August 9, 2023, and U.S. Provisional Application Serial No. 63 / 583,306, filed on September 17, 2023, which are incorporated herein by reference in their entirety as if fully set forth below.FIELD OF THE DISCLOSURE

[0002] The various embodiments of the present disclosure relate generally to membranes, and more particularly to reverse selective O2 / H2 membranes.BACKGROUND

[0003] Hydrogen is a valuable energy resource for the 21st century because of its diverse sources, cleanliness, low carbon emission, flexibility and high efficiency. An important use of hydrogen is in fuel cell-driven power systems, which provide zero pollutant discharge. Hydrogen can be produced using renewable energy, thereby encouraging fuel cell use for vehicles and other power generation industries to develop rapidly. Hydrogen purity for fuel cells must be high, since some impurities can reduce efficiency and even irreversibly damage fuel cell performance and running life. Hydrogen can be produced from various resources, but “green” hydrogen produced from water electrolysis is especially appealing, since it produces only O2, H2 and H2O. As the price of renewable electricity continues to fall, sustainable hydrogen production via water electrolysis is gaining momentum globally.

[0004] Two main electrolyzer technologies are used to produce “green” hydrogen via electrolysis of water. One approach is alkaline electrolysis and the other is proton exchange membrane electrolysis. The alkaline electrolysis approach has a longer lifetime (e.g., 10 years). Alkaline electrolysis produces hydrogen with purity near 99.8% and at oxygen concentrations of 0.2%-0.6%in the leaving H2 stream. Such “green” hydrogen still contains the key impurities of water and oxygen, and each must be reduced to < 5 ppm, with an overall 99.97% H2 purity as noted in Table 1. These facts indicate that water and oxygen impurities from the water electrolysis must be reduced to 5 ppm levels, which would meet the overall 99.97% H2guideline in Table 1. Normally the oxygen can be removed by an additional deoxygenation reactor where catalytic formation of water occurs, followed by additional water removal in a chilled coalescing filter. Finally, the hydrogen can be further dried in a Vacuum-assisted Pressure Swing Adsorption (“VPSA”) system, making the purification process complex and costly. The present disclosure addresses these challenges by providing a membrane separation approach that can, in some embodiments, remove oxygen by a facilitated oxygen transport membrane and, in some embodiments, simultaneously remove water present in the hydrogen / oxygen gas mixture.Table 1. Guidelines for the impurity content in H2 for fuel cells in previous and new standards.

[0005] The present disclosure is directed to overcoming limitations in the art.BRIEF SUMMARY

[0006] An exemplary embodiment of the present disclosure provides a reverse selective O2 / H2 (RSOH) membrane having an O2 / H2 permselectivity of greater than unity.

[0007] In any of the embodiments disclosed herein, the membrane comprises one or more entities capable of forming a reverse selective O2 / H2 (RSOH) membrane.

[0008] In any of the embodiments disclosed herein, one of the entities capable of forming a RSOH membrane is a cobalt porphyrin.

[0009] In any of the embodiments disclosed herein, one of the entities capable of forming a RSOH membrane is a cobalt Schiff base.

[0010] In any of the embodiments disclosed herein, one of the entities capable of forming a RSOH membrane is a cobalt porphyrin-Schiff base conjugate.

[0011] In any of the embodiments disclosed herein, the membrane comprises a material having the following structure:whereinR1, R2, R3, and R4are independently selected from H and aryl, wherein when R1, R2, R3, or R4is aryl, each one can be optionally substituted with -CH2-O-CO-CH2-CO-CH3 or -CH2OH.

[0012] In any of the embodiments disclosed herein, the membrane comprises a material selected from the following compounds:

[0013] In any of the embodiments disclosed herein, the membrane comprises a material having the following structure:

[0014] In any of the embodiments disclosed herein, the membrane comprises a material having a structure of Formula (I):wherein,R5and R7are independently selected from H, Ci-Ce alkyl, aryl, or R5and R7can be selected to combine with the carbons to which they are attached;R6and R8are optional, and if present, are selected independently from H and Ci-C6alkyl;R9is H or Ci-C6alkyl; andR10, R11, R12, and R13are independently selected from H, halogen, Ci-Ce alkoxy, and -SO3.

[0015] In any of the embodiments disclosed herein, the membrane comprises a material having a structure of Formula (la):wherein,R9is H or Ci-Ce alkyl; andR10, R11, R12, and R13are independently selected from H, halogen, Ci-Ce alkoxy, and -SO3.

[0016] In any of the embodiments disclosed herein, the membrane comprises a material having a structure selected from the group consisting of:

[0017] In any of the embodiments disclosed herein, the membrane is in the form of a flat sheet.

[0018] In any of the embodiments disclosed herein, the membrane is spiral wound.

[0019] In any of the embodiments disclosed herein, the membrane comprises a hollow fiber.

[0020] In any of the embodiments disclosed herein, the hollow fiber is a dual layer fiber.

[0021] In any of the embodiments disclosed herein, the hollow fiber comprises a hollow bore, a core layer surrounding the hollow bore, and a sheath layer surrounding the core layer.

[0022] In any of the embodiments disclosed herein, the membrane can further comprise a coating on the sheath layer.

[0023] In any of the embodiments disclosed herein, the coating comprises a cobalt-porphyrin polymer solution.

[0024] In any of the embodiments disclosed herein, the coating comprises a cobalt-Schiff base polymer solution.

[0025] In any of the embodiments disclosed herein, the hollow fiber comprises a sheath layer comprising a cobalt-porphyrin polymer.

[0026] In any of the embodiments disclosed herein, the hollow fiber comprises a sheath layer comprising a cobalt-Schiff base polymer.

[0027] In any of the embodiments disclosed herein, the membrane comprises a sheath layer having a thickness of less than 50 Microns.

[0028] In any of the embodiments disclosed herein, the membrane is a mixed matrix membrane comprising one or more molecularly dispersed additives.

[0029] In any of the embodiments disclosed herein, the membrane has H2O / H2 permeability ratios greater than unity.

[0030] In any of the embodiments disclosed herein, the membrane can achieve hydrogen purity of greater than 99.99%.

[0031] In any of the embodiments disclosed herein, the membrane can achieve hydrogen purity of greater than 99.9995%.

[0032] In any of the embodiments disclosed herein, the membrane has selective layers with features with cobalt-Schiff base in a functionalized layer in a 2-Stage Membrane Unit with 96% recover rate.

[0033] In any of the embodiments disclosed herein, a first layer of the membrane is a cobalt- Schiff base functionalized membrane.

[0034] In any of the embodiments disclosed herein, a second layer of the membrane is a cobalt- Schiff base functionalized membrane.

[0035] In any of the embodiments disclosed herein, the membrane comprises a polymer backbone and a plurality of cobalt-Schiff base complexes.

[0036] In any of the embodiments disclosed herein, at least a first portion of the cobalt-Schiff base complexes are tethered to the polymer backbone.

[0037] In any of the embodiments disclosed herein, at least a second portion of the cobalt- Schiff base complexes are untethered to the polymer backbone.

[0038] In any of the embodiments disclosed herein, each of the cobalt-Schiff base complexes are tethered to the polymer backbone.

[0039] In any of the embodiments disclosed herein, each of the cobalt-Schiff base complexes are untethered to the polymer backbone.

[0040] In any of the embodiments disclosed herein, the cobalt-Schiff base complexes are imidazole-cobalt-Schiff base complexes.

[0041] In any of the embodiments disclosed herein, the polymer backbone comprises polydimethyl siloxane (PDMS).

[0042] In any of the embodiments disclosed herein, the polymer backbone comprises one or more (dimethylsiloxane)-(etherimide) copolymers.

[0043] In any of the embodiments disclosed herein, the polymer backbone comprises (dimethylsiloxane)-phenylinediaminepolyetherimide.

[0044] In any of the embodiments disclosed herein, the polymer backbone comprises one or more aromatic polyimides.

[0045] In any of the embodiments disclosed herein, the polymer backbone comprises ULTEM polyetherimide material.

[0046] In any of the embodiments disclosed herein, the plurality of cobalt-Schiff base complexes comprises the following structure:whereinR14is H, -NH2, -CH2NH2, or -(CH2)nCH2NH2, wherein n= 1- 4; and R15is H, -CH2-aryl, or Ci-Ce alkyl.

[0047] Another exemplary embodiment of the present disclosure provides a method of separating oxygen and / or hydrogen in a stream, the method comprising filtering the stream with the membrane described herein.

[0048] Another exemplary embodiment of the present disclosure provides a method of separating oxygen and / or hydrogen in a stream, wherein the method comprises passing a fluid through the membrane described herein, wherein the fluid comprises H2 and O2; and removing, with the membrane, at least a portion of the O2 from the fluid.BRIEF DESCRIPTION OF THE DRAWINGS

[0049] The following detailed description of specific embodiments of the disclosure will be better understood when read in conjunction with the appended drawings. For the purpose of illustrating the disclosure, specific embodiments are shown in the drawings. It should be understood, however, that the disclosure is not limited to the precise arrangements and instrumentalities of the embodiments shown in the drawings.

[0050] FIG. 1 provides a schematic of a dry-jet / wet-quench process for producing precursor hollow fiber membranes (Cao et. al., “Carbon Molecular Sieve Membrane Preparation by Economical Coating and Pyrolysis of Porous Polymer Hollow Fibers,” Angew Chem hit Ed Engl, 58(35): 12149-12153 (2019)), in accordance with some embodiments of the present disclosure.

[0051] FIG. 2 provides dip-coating of a hollow fiber membrane in the chamber, in accordance with some embodiments of the present disclosure.

[0052] FIG. 3 provides an integrated membrane process for water / oxygen removal from water / oxygen / hydrogen, in accordance with some embodiments of the present disclosure.

[0053] FIG. 4 provides a 2-stage membrane process for a reverse selective O2 / H2 process, in accordance with some embodiments of the present disclosure.

[0054] FIG. 5 provides imidazole-cobalt-Schiff base polydimethylsiloxane (PDMS), in accordance with some embodiments of the present disclosure.

[0055] FIG. 6 provides mixed matrix imidazole-cobalt-Schiff base polydimethylsiloxane (PDMS), in accordance with some embodiments of the present disclosure.

[0056] FIG. 7 provides untethered imidazole-cobalt-Schiff base polydimethylsiloxane (PDMS), in accordance with some embodiments of the present disclosure.

[0057] FIG. 8 provides untethered imidazole-cobalt-Schiff base 6FDA-DAM, in accordance with some embodiments of the present disclosure.DETAILED DESCRIPTION

[0058] Although preferred exemplary embodiments of the disclosure are explained in detail, it is to be understood that other exemplary embodiments are contemplated. Accordingly, it is not intended that the disclosure is limited in its scope to the details of construction and arrangement of components set forth in the following description or illustrated in the drawings. The disclosure is capable of other exemplary embodiments and of being practiced or carried out in various ways. Also, in describing the preferred exemplary embodiments, specific terminology will be resorted to for the sake of clarity.

[0059] To facilitate an understanding of the principles and features of the present disclosure, various illustrative embodiments are explained below. The components, steps, and materials described hereinafter as making up various elements of the embodiments disclosed herein are intended to be illustrative and not restrictive. Many suitable components, steps, and materials that would perform the same or similar functions as the components, steps, and materials described herein are intended to be embraced within the scope of the disclosure. Such other components, steps, and materials not described herein can include, but are not limited to, similar components or steps that are developed after development of the embodiments disclosed herein.

[0060] As used above, and throughout the description herein, the following terms, unless otherwise indicated, shall be understood to have the following meanings. If not defined otherwise herein, all technical and scientific terms used herein have the same meaning as is commonly understood by one of ordinary skill in the art to which this technology belongs. In the event that there is a plurality of definitions for a term herein, those in this section prevail unless stated otherwise.

[0061] As used in the specification and the appended claims, the singular forms “a,” “an” and “the” include plural referents unless the context clearly dictates otherwise.

[0062] The term “alkyl” means an aliphatic hydrocarbon group which may be straight or branched. When not otherwise restricted, the term refers to an alkyl of 20 or fewer carbons. Branched means that one or more lower alkyl groups such as methyl, ethyl, or propyl are attached to a linear alkyl chain. Exemplary alkyl groups include methyl, ethyl, n-propyl, i- propyl, n-butyl, t-butyl, n-pentyl, 3 -pentyl, and the like.

[0063] The term “aryl” means an aromatic monocyclic or multi-cyclic (polycyclic) ring system of 6 to about 19 carbon atoms, or of 6 to about 10 carbon atoms. The ring system of the aryl group may be optionally substituted. Representative aryl groups include, but are not limited to, groups such as phenyl, naphthyl, azulenyl, phenanthrenyl, anthracenyl, fluorenyl, pyrenyl, triphenylenyl, chrysenyl, and naphthacenyl.

[0064] The term “halogen” means fluoro, chloro, bromo, or iodo.

[0065] The term “optionally substituted” is used to indicate that a group may have a substituent at each substitutable atom of the group (including more than one substituent on a single atom), provided that the designated atom's normal valency is not exceeded, and the identity of each substituent is independent of the others. The referenced group may be substituted with one or more additional group(s), including various known protecting groups. The protecting groups that may form the protected derivatives of the above substituents are known to those of skill in the art and may be found in references such as Greene and Wuts. Unless otherwise specified, any of the substituents described herein can be substituted or unsubstituted. For example, “alkyl” can include, e.g., propyl or substituted propyl (e.g., propyl bromide).

[0066] Also, in describing the preferred exemplary embodiments, terminology will be resorted to for the sake of clarity. It is intended that each term contemplates its broadest meaning as understood by those skilled in the art and includes all technical equivalents that operate in a similar manner to accomplish a similar purpose.

[0067] Ranges can be expressed herein as from “about” or “approximately” one particular value and / or to “about” or “approximately” another particular value. When such a range is expressed, another exemplary embodiment includes from the one particular value and / or to the other particular value.

[0068] By ‘ ‘comprising” or “containing” or “including” is meant that at least the named compound, member, particle, or method step is present in the composition or article or method, but does not exclude the presence of other compounds, materials, particles, method steps, even if the other such compounds, material, particles, method steps have the same function as what is named.

[0069] Mention of one or more method steps does not preclude the presence of additional method steps or intervening method steps between those steps expressly identified. Similarly, it is also to be understood that the mention of one or more components in a device or system does not preclude the presence of additional components or intervening components between those components expressly identified.

[0070] The materials described as making up the various members of the invention are intended to be illustrative and not restrictive. Many suitable materials that would perform the same or a similar function as the materials described herein are intended to be embraced within the scope of the invention. Such other materials not described herein can include, but are not limited to, for example, materials that are developed after the time of the development of the invention.

[0071] The present disclosure provides systems and methods for removing oxygen from hydrogen. Some embodiments of the present disclosure provide an oxygen- facilitated membrane separation process, which can remove oxygen and achieve required hydrogen purity > 99.9995%.

[0072] Some embodiments of the present disclosure provide a “reverse selective” membrane having O2 / H2 permselectivity greater than unity, which is not achievable with conventional pure polymer membranes. This membrane can be termed a RSOH (reverse selective O2 / H2) membrane. The RSOH membrane can comprise cobalt-porphyrin derivatives or cobalt-Schiff base complexes, or other entities capable of creating a RSOH membrane in flat sheet, spiral wound or hollow fiber forms. In some embodiments, the membranes can be in composite forms with a RSOH thin (<50 pm) layer supported on a porous support in the forms identified above. For example, in some embodiments, the membranes can be in composite forms with a RSOH layer having a thickness that is less than 5 pm, less than 10 pm, less than 15 pm, less than 20pm, less than 25 pm, less than 30 pm, less than 35 pm, less than 40 pm, or less than 45 pm. In some embodiments, the RSOH membranes can have H2O / H2 permeability ratios greater than unity to allow at least partial dehydration as well as deoxygenation of gas streams containing H2, O2, and H2O. Some embodiments of the present disclosure also provide processes for using the membranes discussed above, including recompression and recycle of part of the O2- enriched permeate to minimize loss of H2 in the process.Oxygen-Carrier Examples

[0073] Non-limiting examples of a RSOH membrane can use a compound having the following structure:whereinR1, R2, R3, and R4are independently selected from H and aryl, and wherein when R1, R2, R3, or R4is aryl, each one can be optionally substituted with -CH2-O-CO-CH2-CO-CH3 or -CH2OH.

[0074] In some embodiments, the RSOH membrane can use a cobalt-porphyrin (5-(4- Benzylacetoacetate)-10,15,20-triphenylcobaltporphyrin (CoPac) or 5-(4-benzylalcohol)- 10,15,20-triphenylcobaltporphyrin (CoPai)) or a cobalt-Schiff base complex:CoPacCopalComplex-1 : R = -OCH3Complex-2: R = -OHCopac can be synthesized using methods known in the art. The cobalt-Schiff base complex can be synthesized by the method described elsewhere (see K. Kar, D. Ghosh, B. Kabi, A. Chandra, Polyhedron 2022, 222).

[0075] In some embodiments, the RSOH membrane can use a compound having the following structure:

[0076] Other non-limiting examples of a RSOH membrane can use a compound of formula (I):wherein,R5and R7are independently selected from H, Ci-Ce alkyl, aryl substituted with -OCH3 or -OH , or R5and R7can combine with the carbons to which they are attached, for example, to form an aryl ring;R6and R8are optional, and if present, are selected independently from H and Ci-C6alkyl;R9is H or Ci-Ce alkyl; andR10, R11, R12, and R13are independently selected from H, halogen, Ci-Ce alkoxy, and -SO3.

[0077] In some embodiments, the RSOH membrane can use a cobalt-Schiff base complex selected from the following:

[0078] In some embodiments, the RSOH membrane comprises a polymer backbone and a plurality of cobalt-Schiff base complexes. In certain embodiments, the plurality of cobalt- Schiff base complexes are tethered to the polymer backbone. As used herein, “tethered” is defined to mean that the complexes are bonded to the polymer backbone with at least one covalent bond. In other embodiments, the plurality of cobalt-Schiff base complexes are untethered to the polymer backbone. As used herein, “untethered” is defined to mean that the complexes are not attached to the polymer backbone by a covalent bond. In other embodiments, a first portion of the cobalt-Schiff base complexes are tethered to the polymer backbone while a second portion of the cobalt-Schiff base complexes are untethered to the polymer backbone. In certain embodiments, the polymer backbone comprises ULTEM polyetherimide material that has a lower Tg than most polyimides to allow stress relaxation around the O2 selective entities. In some embodiments, the plurality of cobalt-Schiff base complexes comprises the following structure:wherein R14is H, -NH2, -CH2NH2, or -(CH2)nCH2NH2; and R15is H, -Ctb-aryl, or Ci-Ce alkyl. When R14is -(CH2)nCH2NH2, n=l-4 to enable covalent reaction with a polyimide to provide attachment along the polymer backbone.

[0079] To modify the hydrophilicity of the as-mentioned oxygen-carrier, additional treatment may be performed. Without being limited, oxygen-carriers with cobalt could have various structures depending on the precursor material chosen for the derivative or complex formation.RSOH Composite Hollow Fiber Membrane Fabrication via Dip-CoatingComposite Precursor Hollow Fiber Membrane Formation

[0080] To illustrate an exemplary embodiment of the present disclosure, an asymmetric duallayer hollow fiber membrane can be formed using a modified dry-jet / wet-quench spinning process like that reported in US Patent Application Publication No. 2015 / 0011815A1, which is incorporated herein by reference in its entirety, shown in FIG. 1. This dual-layer fiber can comprise one sheath layer of neat Torlon®, one porous core layer with Torlon®, and a hollow bore. A bore fluid and two spinning dopes (core spinning dope and sheath spinning dope), used to spin Torlon® dual-layer fiber membranes, can enable precise tuning of the outer fiber surface porosity for facile coating. Such fibers are included herein by example.Dip-Coating for RSOH Composite Hollow Fiber Membrane Preparation

[0081] A dip-coating method can be applied to coat cobalt-porphyrin network polymer solutions onto the outer surface of the Torlon® dual-layer fiber membranes, which follows the protocol we developed previously (see Y. Cao, K. Zhang, O. Sanyal, W. J. Koros, Angew Chem Int Ed Engl 2019, 58, 12149-12153). As is shown in FIG. 2, one end of the fiber can be sealed by epoxy to prevent the solution from entering the lumen side. Coating of polymer on the precursor hollow fiber membrane can be conducted by dipping the precursor in the polymer solution for 30s. The fiber can be taped onto a stainless-steel rod to move the fiber in and out of the coating solution and evaporation zone. The dip-coated hollow fibers can be dried under vacuum at 75 °C for 2 hours. The dip-coating can be conducted at high relative humidity (RH) of 60% (in atmosphere) or low RH of 10% (in a coating chamber purged by dry nitrogen, FIG. 2).

[0082] To expedite large module formation, a continuous coater can also be used, based on the optimized lab-scale batch coating conditions.Sheath-Core Spun RSOH Composite Hollow Fiber Membrane

[0083] In yet another exemplary embodiment of the present disclosure, for one skilled in the art that with optimization of the spinning process in FIG. 1 , the sheath layer can comprise amaterial like the cobalt-porphyrin polymer solution. This sheath-core aspect is known in the art for different membranes but has not been disclosed for the RSOH membranes. Without being bound by details, this aspect of spinning a RSOH sheath layer on a core support is used in some embodiments of the present disclosure.Mixed Matrix RSOH Membrane

[0084] Rather than covalently including the RSOH agents in the polymer backbone, in some embodiments, the RSOH agents can be included in the coating solution or sheath solution discussed above as molecularly dispersed additives. Such membranes fall in the category normally considered to be a mixed matrix membrane, and are also used in some embodiments of the present disclosure to create RSOH membranes.Modeling and Simulation of the Membrane Efficiency with Different Operation Conditions

[0085] Below, is illustrated the ability of such a RSOH membrane in an actual module for a countercurrent flow pattern. Other calculations of flow patterns such as crossflow modules can be considered, but the current example effectively shows the benefits some embodiments of the present disclosure. For this section, CoPac-Im-PTA is used, which is a rubbery matrix, only described previously for O2 / N2 separation. Since this is a rubbery matrix, the 0.112 2 should be similar to PDMS ~ 65 / 28 = 2.3 in the absence of O2 facilitation. On the other hand, since ao2 / N2 = 30 with facilitation, the ao2 / H2 should equal ao2 / N2 / ai 12 2 = 30 / (2.3) ~ 13 = ao2 / H2, which is used here.

[0086] Simulation with 0.2% oxygen feed: The product leaving alkaline hydrolysis units have O2 contamination ranging from 0.2% to 0.6% on a water-free basis. Using this fact, a H2 / O2 mixture feed gas with 0.2% O2 and an O2 impurity of 5 ppm in the final purified H2 listed in Table 1 allows us to assess the requirements for a realistic RSOH membrane. The above- mentioned CoPac-Im-PTA, showed a 130 Barrer O2 permeability for a 14.7 psia upstream. For an easily achievable 10pm selective layer, the estimated oxygen permeance is 13 GPU with hydrogen permeance of 1 GPU based on the above-mentioned 13 = ao2 / H2. The feed gas composition and membrane permeances are listed in Table 2. A RSOH membrane can therefore be illustrated with a membrane simulator (Version 2.0) with countercurrent flow, using parameters of the membrane process shown in Table 3. With a hollow fiber membrane active length of 1.55 m, —100% purity hydrogen with 63.01% recovery is achieved in the retentate(shown in Table 4). If the hollow fiber membrane active length reduces to 1.50 m with the same other parameters, 99.99% purity hydrogen can be generated on the retentate side (detailed results are shown in Table 5). Therefore, the hollow fiber membrane active length can desirably be between 1.50 m to 1.55 m.Table 2. Feed gas composition and membrane permeance.Table 3. Parameters of membrane process.Table 4. Simulation results with 1.55 m hollow fiber membrane active length.Table 5. Simulation results with 1.50 m hollow fiber membrane active length.

[0087] Simulation with 0.6% oxygen feed. Another simulation case for the more challenging feed with 0.6% oxygen concentration is also useful. With 1.90 m hollow fiber membrane active length (the other parameters are the same), the simulation results are shown in Table 6, indicating that the hydrogen concentration in the retentate is not high enough (>0.999995). Nevertheless, by simply using 12000 hollow fibers instead of 8000 with the membrane active length of 1.20 meter, the hydrogen purity in the retentate increases to nearly 100%. The simulation results are shown in Table 7.Table 6. Simulation results with 1.90 m hollow fiber membrane active length (8000 fibers with 0.6% oxygen feed).Table 7. Simulation results with 1.20 m hollow fiber membrane active length (12000 fibers with 0.6% oxygen feed).

[0088] In summary, based on the oxygen concentration in the feed, increasing the membrane area can be an effective way to achieve high purity hydrogen in the retentate. The effective hollow fiber membrane length can be a key factor for high purity hydrogen production.

[0089] The RSOH membranes can also remove moisture from the mixed gas feed. Clearly, the water concentration in the hydrogen product stream (>99.9995%) can be very low since H2O / H2 and H2O / O2 selectivities tend to be > 100 for most membranes. Of course, a VPSA process can also added after the one stage membrane process to ensure the water concentration in the product is <5ppm, but it is unlikely to be needed. Finally, multiple membrane units can be used to maximize high hydrogen recovery rate. Simple re-pressurization of permeate from the first stage, with recycling of the 2nd stage retentate to the first stage feed (FIG. 3), will increase overall H2 recovery rate. FIG. 3 shows such an integrated membrane process to remove water and oxygen, which can significantly reduce operation cost even if a small VPSA process may be used for the final product to meet the ISO 14687 standard.Co-Schiff Base In Imidazole Functionalized PDMS 2-Stage Membrane Unit With 96% Recover Rate

[0090] In this section, new membrane selective layers are disclosed with appealing features with Co-Schiff base in Imidazole Functionalized PDMS 2-Stage Membrane Unit with 96% recover rate.

[0091] The 2-stage membrane process is illustrated in FIG. 4.

[0092] The membrane separation layer can have two main structures illustrated in FIGs. 5 and 6.

[0093] PDMS membrane has 800 Barrer O2. It is estimated that the imidazole functionated PDMS has 600 Barrer O2 and 01O2 / H2 = 13.

[0094] For a 1 pm skin layer, we used (Pi / L) = 600 GPU O2 & 46.2 GPU H2 in simulation here.Table 8. Parameters of stage 1 membrane process with 0.2% O2 in theTable 9. Simulation results of stage 1 with 0.35 m membrane active length.

[0095] 45.18% of the feed gas comprises the permeate with 0.44% O2, which needs further purification in stage 2 to reach 99.8% purity and can be recycled and merged with the feed stream in the stage 1.

[0096] The stage 2 simulation results for the same fundamental membrane properties as stage 1 but with smaller required membrane area will be shown in Tables 10-11.Table 10. Parameters of stage 2 membrane process with 0.44% O2 in the feed.Table 11. Simulation results of stage 2 with 0.2 m membrane active length.

[0097] The 99.76% hydrogen can be recycled and merged with the feed stream of the stage 1 process.

[0098] The overall H2 yield of the 2-stage hollow fiber membrane process- 1 -stage cutlxstage cut2=l-45.18% x 8.26% 96.3%.

[0099] The total membrane areas that can be utilized for for the 2-stage membrane process- 1 1.0 m2+0.9 m2- 1 1.9 m2.

[0100] The productivity of the 2-stage membrane process for a 100 SCFH feed- 100 SCFH x 96.3% overall -96.3 SCFH product.Assuming membrane lifetime: 3 years, 96% capacity factor operation time in a year= 365x24hx96%x3=25,229hA total of 11.9 m2membrane modules can yield approximately 100% H2 with 96.3 SCFH.Total amount of H2 treated in 3 years=25,229hx96.3SCFH=2,429,553SCF=2,429,553SCFx0.002363Kg / SCF=5741.0KgIf 3 kilo tons hydrogen produced in 3 years, then in the 3 -year membrane lifetime, the membrane cost$62, 1 84 / (kT- year)Co-Schiff Base In Imidazole Functionalized 6DFA-DAM Polyimide

[0101] Vinyl Imidazole Co-Schiff Base tethered to PDMS showed insufficient capacity and “mixed matrix” materials with disperse aromatic Schiff bases had limited solubility in PDMS. Unlike PDMS, 6FDA-DAM is miscible in one of the favored fiber spinning solvents, N- methyl-pyrrolidone (NMP), with Co-Schiff base benzyl imidazole, and would allow highly scalable sheath-core fiber spinning with high loading.

[0102] It is to be understood that the embodiments and claims disclosed herein are not limited in their application to the details of construction and arrangement of the components set forth in the description and illustrated in the drawings. Rather, the description and the drawings provide examples of the embodiments envisioned. The embodiments and claims disclosed herein are further capable of other embodiments and of being practiced and carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein are for the purposes of description and should not be regarded as limiting the claims.

[0103] Accordingly, those skilled in the art will appreciate that the conception upon which the application and claims are based may be readily utilized as a basis for the design of other structures, methods, and systems for carrying out the several purposes of the embodiments and claims presented in this application. It is important, therefore, that the claims be regarded as including such equivalent constructions.

[0104] Furthermore, the purpose of the foregoing Abstract is to enable the United States Patent and Trademark Office and the public generally, and especially including the practitioners in the art who are not familiar with patent and legal terms or phraseology, to determine quickly from a cursory inspection the nature and essence of the technical disclosure of the application. The Abstract is neither intended to define the claims of the application, nor is it intended to be limiting to the scope of the claims in any way.

Claims

CLAIMSWhat is claimed is:

1. A reverse selective O2 / H2 (RSOH) membrane having an O2 / H2 permselectivity of greater than unity.

2. The membrane of claim 1, wherein the membrane comprises one or more entities capable of forming a reverse selective O2 / H2 (RSOH) membrane.

3. The membrane of claim 2, wherein one of the entities capable of forming a RSOH membrane is a cobalt porphyrin.

4. The membrane of claim 2, wherein one of the entities capable of forming a RSOH membrane is a cobalt Schiff base.

5. The membrane of claim 2, wherein one of the entities capable of forming a RSOH membrane is a cobalt porphyrin- Schiff base conjugate.

6. The membrane of claim 3, wherein the membrane comprises a material having the following structure:whereinR1, R2, R3, and R4are independently selected from H and aryl, wherein when R1, R2, R3, or R4is aryl, each one can be optionally substituted with -CH2-O-CO-CH2-CO-CH3 or -CH2OH.

7. The membrane of claim 6, wherein the membrane comprises a material selected from the following compounds:

8. The membrane of claim 3, wherein the membrane comprises a material having the following structure:

9. The membrane of claim 3, wherein the membrane comprises a material having a structure of Formula (I):wherein,R5and R7are independently selected from H, Ci-Ce alkyl, aryl, or R5and R7can be selected to combine with the carbons to which they are attached;R6and R8are optional, and if present, are selected independently from H and Ci-C6alkyl;R9is H or Ci-C6alkyl; andR10, R11, R12, and R13are independently selected from H, halogen, Ci-Ce alkoxy, and -SO3.

10. The membrane of claim 9, wherein the membrane comprises a material having a structure of Formula (la):wherein,R9is H or Ci-Ce alkyl; andR10, R11, R12, and R13are independently selected from H, halogen, Ci-Ce alkoxy, and -SO3.

11. The membrane of claim 9, wherein the membrane comprises a material having a structure selected from the group consisting of:

12. The membrane of claim 1, wherein the membrane is in the form of a flat sheet.

13. The membrane of claim 1, wherein the membrane is spiral wound.

14. The membrane of claim 1, wherein the membrane comprises a hollow fiber.

15. The membrane of claim 14, wherein the hollow fiber is a dual layer fiber.

16. The membrane of claim 14, wherein the hollow fiber comprises: a hollow bore; a core layer surrounding the hollow bore; and a sheath layer surrounding the core layer.

17. The membrane of claim 16, further comprising a coating on the sheath layer.

18. The membrane of claim 17, wherein the coating comprises a cobalt-porphyrin polymer solution.

19. The membrane of claim 17, wherein the coating comprises a cobalt-Schiff base polymer solution.

20. The membrane of claim 14, wherein the hollow fiber comprises a sheath layer comprising a cobalt-porphyrin polymer.

21. The membrane of claim 14, wherein the hollow fiber comprises a sheath layer comprising a cobalt-Schiff base polymer.

22. The membrane of claim 14, comprising a sheath layer having a thickness of less than 50 Microns.

23. The membrane of claim 1, wherein the membrane is a mixed matrix membrane comprising one or more molecularly dispersed additives.

24. The membrane of claim 1, wherein the membrane has H2O / H2 permeability ratios greater than unity.

25. The membrane of claim 1, wherein the membrane can achieve hydrogen purity of greater than 99.99%.

26. The membrane of claim 1, wherein the membrane can achieve hydrogen purity of greater than 99.9995%.

27. The membrane of claim 1, wherein the membrane has selective layers with features with cobalt-Schiff base in a functionalized layer in a 2-Stage Membrane Unit with 96% recover rate.

28. The membrane of claim 27, wherein a first layer is a cobalt-Schiff base functionalized membrane.

29. The membrane of claim 28, wherein a second layer is a cobalt-Schiff base functionalized membrane.

30. The membrane of claim 1, wherein the membrane comprises a polymer backbone and a plurality of cobalt-Schiff base complexes.

31. The membrane of claim 30, wherein at least a first portion of the cobalt-Schiff base complexes are tethered to the polymer backbone.

32. The membrane of claim 31, wherein at least a second portion of the cobalt-Schiff base complexes are untethered to the polymer backbone.

33. The membrane of claim 31, wherein each of the cobalt-Schiff base complexes are tethered to the polymer backbone.

34. The membrane of claim 31, wherein each of the cobalt-Schiff base complexes are untethered to the polymer backbone.

35. The membrane of any one of claims 30-34, wherein the cobalt-Schiff base complexes are imidazole-cobalt-Schiff base complexes.

36. The membrane of claim 30, wherein the polymer backbone comprises polydimethyl siloxane (PDMS).

37. The membrane of claim 30, wherein the polymer backbone comprises one or more (dimethylsiloxane)-(etherimide) copolymers.

38. The membrane of claim 30, wherein the polymer backbone comprises (dimethylsiloxane)-phenylinediaminepolyetherimide.

39. The membrane of claim 30, wherein the polymer backbone comprises one or more aromatic polyimides.

40. The membrane of claim 30, wherein the polymer backbone comprises ULTEM polyetherimide material.

41. The membrane of claim 30, wherein the plurality of cobalt-Schiff base complexes comprises the following structure:whereinR14is H, -NH2, -CH2NH2, or -(CH2)nCH2NH2, wherein n= 1- 4; and R15is H, -CH2-aryl, or Ci-Ce alkyl.

42. A method of separating oxygen and / or hydrogen in a stream, the method comprising filtering the stream with the membrane of any one of claims 1-41.

43. A method of separating oxygen and / or hydrogen in a stream, wherein the method comprises: passing a fluid through the membrane of any one of claims 1-41, wherein the fluid comprises H2 and O2; and removing, with the membrane, at least a portion of the O2 from the fluid.