Method for separating hydrogen and carbonaceous compounds

Abstract

Hydrogen (H2) and a carbonaceous compound may be separated by a method including: introducing a mixed gas containing a target chemical and a secondary chemical into a first membrane; a first retentate and a first permeate at the first membrane, where the first retentate comprises an elevated concentration of a target chemical and the first permeate comprises an elevated concentration of a secondary chemical; introducing the first retentate into the second membrane; and separating the second retentate and the second permeate at the second membrane, where the second retentate comprises an elevated concentration of a secondary chemical and the second permeate comprises an elevated concentration of a target chemical, where the target chemical is H2 or a carbonaceous compound, the secondary chemical is H2 or a carbonaceous compound, and the second permeate comprises an elevated concentration of the target chemical. And the target chemical is different from the secondary chemical.

Description

Cross-references to related applications

[0001] This application claims the benefit of U.S. Provisional Application Serial No. 63 / 579,624, filed on August 30, 2023, the contents of which are incorporated herein by reference. Technical Field

[0002] This disclosure relates to gas separation, and more specifically to the separation of hydrogen and ethylene using a combination of reverse-selective and superselective membranes. Background Technology

[0003] Gas separation is a critical process in cracking plants, typically involving the extraction and purification of gases, such as ethylene and hydrogen, from mixed feedstocks using cryogenic distillation or, occasionally, membrane separation. Cryogenic distillation utilizes differences in boiling points to produce high-purity outputs. However, the energy-intensive nature of cryogenic distillation stems from the necessity of maintaining extremely low temperatures, leading to significant refrigeration requirements and complex infrastructure, in addition to high compression and associated costs. This results in substantial operating expenses and significant initial investment. In contrast, membrane separation offers energy efficiency and requires less space than cryogenic distillation. However, achieving stringent purity standards can be challenging, and the energy-intensive compression required by this technology increases costs. Essentially, both cryogenic distillation and membrane separation are well-suited for gas separation; however, the refrigeration requirements of the former and the compression requirements of the latter amplify their individual costs and complexities within a cracking plant. Therefore, new and more efficient methods for gas separation will be needed to address these challenges. Summary of the Invention

[0004] This document describes a method for separating gases such as hydrogen and carbonaceous compounds (e.g., ethylene and / or carbon dioxide). In the embodiments described herein, a gas mixture containing a target chemical and a secondary chemical can be separated using a two-stage membrane system. Depending on the composition of the gas mixture, each stage can utilize either a reverse-selective membrane or a superselective membrane. When the target chemical has a smaller representative molecular diameter than the secondary chemical, a reverse-selective membrane can be used in the first stage. For example, when hydrogen is the target chemical and ethylene is the secondary chemical, a reverse-selective membrane can be used in the first stage. Alternatively, when the secondary chemical has a smaller representative molecular diameter than the target chemical, a superselective membrane can be used as the first membrane. For example, when ethylene is the target chemical and hydrogen is the secondary chemical, a superselective membrane can be used in the first stage. The second membrane can separate the permeate produced by the separation by the first membrane, which is still under high pressure. When the first membrane is a superselective membrane, the second membrane can be a reverse-selective membrane, and vice versa. As described herein, the use of a combined system of reverse-selective and superselective membranes can be used to efficiently separate gases such as carbonaceous compounds and hydrogen.

[0005] According to one or more embodiments described herein, a method for separating hydrogen and a carbonaceous compound may include: introducing a mixed gas containing a target chemical substance and a secondary chemical substance into a first membrane. The method further includes: separating a first permeate and a first permeate at the first membrane, wherein the first permeate contains an elevated concentration of the target chemical substance, and the first permeate contains an elevated concentration of the secondary chemical substance. The method further includes: introducing the first permeate into a second membrane, and separating a second permeate and a second permeate at the second membrane, wherein the second permeate contains an elevated concentration of the secondary chemical substance, and the second permeate contains an elevated concentration of the target chemical substance. Additionally, the target chemical substance is either hydrogen or the carbonaceous compound, the secondary chemical substance is either hydrogen or the carbonaceous compound, and the target chemical substance is different from the secondary chemical substance.

[0006] It should be understood that both the foregoing general description and the following detailed description present embodiments of the described technology and are intended to provide an overview or framework for understanding the nature and characteristics of the described technology as claimed. Drawings are included to provide a further understanding of the described technology, and these drawings are incorporated in and form a part of this specification. The drawings illustrate various embodiments and, together with the description, serve to explain the principles and operation of the described technology. Furthermore, the drawings and description are intended to be illustrative only and are not intended to limit the scope of the claims in any way. Attached Figure Description

[0007] The following detailed description of specific embodiments of this disclosure is best understood in conjunction with the following drawings, in which similar reference numerals indicate similar structures, and in the drawings:

[0008] Figure 1 An apparatus for separating a target chemical substance from a secondary chemical substance, according to one or more embodiments disclosed herein, is schematically depicted.

[0009] Figure 2 An apparatus for separating a target chemical substance from a secondary chemical substance, according to one or more embodiments disclosed herein, is schematically depicted; and

[0010] Figure 3 A cross-section of an asymmetric hollow carbon fiber according to one or more embodiments of the present disclosure is depicted.

[0011] For the purpose of simplifying the schematic diagrams and illustrations of the related figures, numerous valves, temperature sensors, electronic controllers, and other components well-known to and likely employed by those skilled in the art in certain chemical processing operations are not included. It should be understood that these components are within the spirit and scope of the embodiments disclosed in this invention. However, operating components (such as those described in this disclosure) may be added to the embodiments described in this disclosure.

[0012] It should be understood that the features described in the various figures can be used in conjunction with other aspects in different figures. That is, as those skilled in the art will understand, Figure 1 The implementation plan can utilize Figure 2 The characteristics of the implementation plan.

[0013] It should be further noted that the arrows in the accompanying drawings refer to process streams. However, arrows can also refer equivalently to transfer lines that can be used to transfer process streams between two or more system components. Additionally, arrows connected to system components define the inlet or outlet of each given system component. The direction of the arrows generally aligns with the primary direction of movement of the stream material contained within the physical transfer line represented by the arrow. Furthermore, arrows not connected to two or more system components represent product streams leaving the depicted system or system inlet streams entering the depicted system. Product streams may be further processed in an accompanying chemical processing system or may be commercialized as a final product. System inlet streams may be streams transferred from an accompanying chemical processing system or may be unprocessed raw material streams. Some arrows may indicate recycle streams, which are outflow streams from system components and are recycled back into the system. However, it should be understood that in some embodiments, any illustrated recycle stream may be replaced by a system inlet stream of the same material, and a portion of the recycle stream may leave the system as a system product.

[0014] Additionally, the arrows in the accompanying drawings may schematically depict process steps for transferring material streams from one system component to another. For example, an arrow pointing from one system component to another may indicate the "transfer" of effluent from one system component to another, which may include the "discharge" or "removal" of process stream contents from one system component and the "introduction" of the product stream contents into another system component.

[0015] It should be understood that, according to the embodiments presented in the relevant figures, the arrow between two system components may indicate that the material flow is unprocessed between the two system components. In other embodiments, the material flow represented by the arrow may have substantially the same composition throughout the transport process between the two system components. Furthermore, it should be understood that in one or more embodiments, the arrow may indicate that at least 75% by weight, at least 90% by weight, at least 95% by weight, at least 99% by weight, at least 99.9% by weight, or even 100% by weight of the material flow is transported between the system components. Therefore, in some embodiments, not all of the material flow represented by the arrow will be transported between the system components, such as when there is a side flow.

[0016] It should be understood that in the schematic flow diagrams of the relevant accompanying figures, the intersection of two or more lines indicates that two or more process streams are "mixed" or "merged". Mixing or merging can also include mixing by directly introducing the two streams into similar reactors, separation units, or other system components. For example, it should be understood that when two streams are depicted as being merged directly before entering a separation unit or reactor, in some embodiments these streams may be equivalently introduced into the separation unit or reactor and mixed in the reactor.

[0017] Reference will now be made in more detail to various embodiments, some of which are illustrated in the accompanying drawings. Where possible, the same reference numerals will be used throughout the drawings to refer to the same or similar parts. Detailed Implementation

[0018] This disclosure relates to methods for separating a target chemical substance from secondary chemical substances. Generally, this document describes methods for separating target chemical substances from secondary chemical substances in processing systems (such as...). Figure 1 and Figure 2 These methods are described in the context of those processing systems. However, it should be understood that these methods can be utilized independently of the processing systems described herein, and it is expected that other systems can be used to practice the techniques currently described.

[0019] As used in this disclosure, "directly" transferring a stream or effluent from one unit to another can mean transferring a stream or effluent from the first unit to the second unit without transferring the stream or effluent through an intermediate reaction system or separation system that substantially alters the composition of the stream or effluent. Heat transfer devices such as heat exchangers, preheaters, coolers, condensers, or other heat transfer equipment, and pressure devices such as pumps, pressure regulators, compressors, or other pressure devices are not considered intermediate systems that alter the composition of the stream or effluent. Combining two streams or effluents is also not considered to include an intermediate system that alters the composition of one or both of the combined streams or effluents. Simply splitting a stream into two streams having the same composition is also not considered to include an intermediate system that alters the composition of the stream.

[0020] As used throughout this disclosure, the terms "upstream" and "downstream" can refer to the relative positioning of a unit operation with respect to the flow direction of the process flow. If the process flow through the system encounters a first unit operation before encountering a second unit operation, then the first unit operation of the system can be considered "upstream" of the second unit operation. Similarly, if the process flow through the system encounters a first unit operation before encountering a second unit operation, then the second unit operation can be considered "downstream" of the first unit operation.

[0021] It should be understood that the separation methods described in this disclosure may not completely separate all of one chemical component from all of another chemical component. It should be understood that the separation methods described in this disclosure separate different chemical components "at least partially" from each other, and even if not explicitly stated, it should be understood that separation may include only partial separation. It should be understood that a "separation unit" is a separation unit primarily used for separating two or more gases.

[0022] As used in this disclosure, a "reverse-selective" membrane refers to a membrane that exhibits the property of allowing some larger molecules to permeate faster than smaller molecules. Unlike conventional membranes that facilitate the movement of substances from regions of high concentration to regions of low concentration, reverse-selective membranes facilitate the faster transport of larger molecules across the separation membrane compared to smaller molecules.

[0023] As used in this disclosure, a "superselective" membrane refers to a membrane operated by a specialized material having a nanoporous structure or functional groups that enable preferential gas permeation of smaller substances. In a superselective membrane, gas molecules interact with the membrane surface and permeate based on size exclusion, adsorption, diffusion, or chemical affinity.

[0024] As used in this disclosure, a "storage container" means a container in which one or more fluids can be stored. For example, a storage container can store liquids, gases, or a combination of both. Storage containers are not limited by geometry and / or size and may include tanks, drums, silos, pipes, etc.

[0025] As used in this disclosure, the term "permeate" refers to the portion of the gas feed retained by the membrane. In other words, permeate does not pass through the membrane.

[0026] As used in this disclosure, the term "permeate" refers to the portion of the gas feed that diffuses through or permeates the membrane.

[0027] As used in this disclosure, the term "carbon-containing compound" refers to any chemical substance containing carbon atoms. For example, a carbon-containing compound may refer to, but is not limited to, ethylene or carbon dioxide.

[0028] As used in this disclosure, the term "analyte" refers to a gaseous stream whose chemical composition is identified and measured.

[0029] Now for reference Figure 1 The document describes a two-stage membrane separation apparatus 100 suitable for separating a target chemical substance from secondary chemical substances. The two-stage membrane separation apparatus 100 may include a first membrane 110 and a second membrane 120. The membranes may be housed within a mechanical device suitable for containing gases, such as a storage container. According to embodiments, and as described herein, the target chemical substance included in a gas mixture can be separated from the secondary chemical substances within the gas mixture.

[0030] Still referencing Figure 1 According to one or more embodiments, a mixed gas 101 may be introduced into a first membrane 110 through a gas inlet. The gas inlet may be a pipe or other similar conduit. In one or more embodiments, the mixed gas contains a target chemical substance and at least a secondary chemical substance. As described herein, a "target chemical substance" refers to a chemical substance that is selectively separated from the mixed gas as a first permeate at the first membrane. In embodiments, the target chemical substance may be a carbonaceous compound or hydrogen. The secondary chemical substance may be any chemical substance that is not the target chemical substance and permeates the first membrane. It is contemplated that more than a single chemical substance can be selectively separated from the mixed gas in the process described herein.

[0031] In some embodiments, the target chemical substance may be hydrogen, and the secondary chemical substance may be a carbon-containing compound, such as ethylene or carbon dioxide. It is also contemplated that the target chemical substance may be a carbon-containing compound, such as ethylene or carbon dioxide, and the secondary chemical substance may be hydrogen. The composition of the target chemical substance depends on the composition of the gas mixture. In one or more embodiments, the concentration of the target chemical substance in the gas mixture is greater than the concentration of the secondary chemical substance in the gas mixture. For example, when the concentration of hydrogen in the gas mixture is greater than the concentration of the carbon-containing compound, the target chemical substance may be hydrogen, and the secondary chemical substance may be a carbon-containing compound. Conversely, when the concentration of the carbon-containing compound is greater than or equal to the concentration of hydrogen, the target chemical substance may be a carbon-containing compound. The gas mixture containing the target chemical substance and the secondary chemical substance may be generated from, but is not limited to, a cracking plant, an autothermal reactor, a de-ethanizer, a C2 separator, or a C3 separator.

[0032] Still referencing Figure 1 After the mixed gas 101 is introduced into the first membrane 110, the mixed gas 101 separates into a first permeate 103 and a first permeate 102 at the first membrane 110. The first permeate 103 may contain a higher concentration of the target chemical substance compared to the mixed gas. The first permeate 103 can be introduced into a second membrane 120 downstream of the first membrane 110. Notably, the permeate 103 can be maintained at a pressure relatively the same as the mixed gas, thereby reducing the need for interstage compression.

[0033] In implementations, the concentrations of the target chemical and secondary chemical substances within any feed stream can differ, depending on the stage cut. As used herein, the term "stage cut" refers to the fraction of the feed gas into the permeate membrane. In some implementations, the stage cut can be from 1% to 50%, for example, 5% to 50%, 10% to 50%, 15% to 50%, 20% to 50%, 25% to 50%, 30% to 50%, 35% to 50%, 40% to 50%, 45% to 50%, 1% to 40%, 1% to 30%, 1% to 20%, or even 1% to 10%.

[0034] In some embodiments, the concentration of the target chemical substance in the first residue 103 can be from 50 mol% to 95 mol%, for example, 50 mol% to 95 mol%, 55 mol% to 95 mol%, 60 mol% to 95 mol%, 65 mol% to 95 mol%, 70 mol% to 95 mol%, 75 mol% to 95 mol%, 80 mol% to 95 mol%, 85 mol% to 95 mol%, 90 mol% to 95 mol%, 50 mol% to 90 mol%, 50 mol% to 80 mol%, 50 mol% to 70 mol%, or even 50 mol% to 60 mol%.

[0035] In some embodiments, the concentration of the secondary chemical substance in the first residue 103 can be from 5 mol% to 50 mol%, for example, 10 mol% to 50 mol%, 15 mol% to 50 mol%, 20 mol% to 50 mol%, 25 mol% to 50 mol%, 30 mol% to 50 mol%, 35 mol% to 50 mol%, 40 mol% to 50 mol%, 45 mol% to 50 mol%, 5 mol% to 40 mol%, 5 mol% to 30 mol%, 5 mol% to 20 mol%, or even 5 mol% to 10 mol.

[0036] Compared to the gas mixture, the first permeate 102 may contain a higher concentration of secondary chemicals. The first permeate 102 may be introduced into the atmosphere outside the mechanical device housing the first membrane 110. In some embodiments, the concentration of the secondary chemical substance in the first permeate 102 may be from 85 mol% to 99 mol%, for example, 87 mol% to 99 mol%, 89 mol% to 99 mol%, 91 mol% to 99 mol%, 93 mol% to 99 mol%, 95 mol% to 99 mol%, 97 mol% to 99 mol%, 90 mol% to 99 mol%, 92 mol% to 99 mol%, 94 mol% to 99 mol%, 96 mol% to 99 mol%, 98 mol% to 99 mol%, 90 mol% to 98 mol%, 92 mol% to 98 mol%, 94 mol% to 98 mol%, 96 mol% to 98 mol%, 90 mol% to 97 mol%, 92 mol% to 97 mol%, 94 mol% to 97 mol%, 96 mol% to 97 mol%, 90 mol% to 96 mol%, 92 mol% to 96 mol%, or even 94 mol% to 96 mol%.

[0037] In some embodiments, the concentration of the target chemical substance in the first permeate 102 can be from 1 mol% to 15 mol%, for example, 3 mol% to 15 mol%, 5 mol% to 15 mol%, 13 mol% to 15 mol%, 7 mol% to 15 mol%, 9 mol% to 15 mol%, 11 mol% to 15 mol%, or 13 mol% to 15 mol.

[0038] After the first permeate 103 is introduced into the second membrane 120, the first permeate separates at the second membrane 120 into a second permeate 105 and a second permeate 104. The second permeate 105 may contain a secondary chemical substance at an increased concentration. The second permeate 105 may be introduced into an atmosphere outside the machinery housing the second membrane 120. In some embodiments, the concentration of the secondary chemical substance in the second permeate 105 may be from 5 mol% to 50 mol%, for example, 10 mol% to 50 mol%, 15 mol% to 50 mol%, 20 mol% to 50 mol%, 25 mol% to 50 mol%, 30 mol% to 50 mol%, 35 mol% to 50 mol%, 40 mol% to 50 mol%, 45 mol% to 50 mol%, 5 mol% to 40 mol%, 5 mol% to 30 mol%, 5 mol% to 20 mol%, or even 5 mol% to 10 mol%.

[0039] In some embodiments, the concentration of the target chemical substance in the second residue 105 can be from 50 mol% to 95 mol%, for example, 50 mol% to 95 mol%, 55 mol% to 95 mol%, 60 mol% to 95 mol%, 65 mol% to 95 mol%, 70 mol% to 95 mol%, 75 mol% to 95 mol%, 80 mol% to 95 mol%, 85 mol% to 95 mol%, 90 mol% to 95 mol%, 50 mol% to 90 mol%, 50 mol% to 80 mol%, 50 mol% to 70 mol%, or even 50 mol% to 60 mol%.

[0040] After the first permeate 103 is introduced into the second membrane 120, the first permeate separates at the second membrane 120 into a second permeate 105 and a second permeate 104. The second permeate 105 may contain a higher concentration of secondary chemicals. The second permeate 105 may be introduced into the atmosphere outside the machinery housing the second membrane 120.

[0041] In some embodiments, the concentration of the secondary chemical substance in the second residue 105 can be from 5 mol% to 50 mol%, for example, 10 mol% to 50 mol%, 15 mol% to 50 mol%, 20 mol% to 50 mol%, 25 mol% to 50 mol%, 30 mol% to 50 mol%, 35 mol% to 50 mol%, 40 mol% to 50 mol%, 45 mol% to 50 mol%, 5 mol% to 40 mol%, 5 mol% to 30 mol%, 5 mol% to 20 mol%, or even 5 mol% to 10 mol.

[0042] In some embodiments, the concentration of the target chemical substance in the second residue 105 can be from 50 mol% to 95 mol%, for example, 50 mol% to 95 mol%, 55 mol% to 95 mol%, 60 mol% to 95 mol%, 65 mol% to 95 mol%, 70 mol% to 95 mol%, 75 mol% to 95 mol%, 80 mol% to 95 mol%, 85 mol% to 95 mol%, 90 mol% to 95 mol%, 50 mol% to 90 mol%, 50 mol% to 80 mol%, 50 mol% to 70 mol%, or even 50 mol% to 60 mol%.

[0043] The second permeate 104 may contain an increased concentration of the target chemical substance. The second permeate 104 may be introduced into an atmosphere outside the mechanical device housing the second membrane 120. In some embodiments, the concentration of the target chemical substance in the second permeate 104 may be from 95 mol% to 99.9 mol%, for example, 96 mol% to 99.9 mol%, 97 mol% to 99.9 mol%, 98 mol% to 99.9 mol%, or 99 mol% to 99.9 mol%. In some embodiments, the concentration of the secondary chemical substance in the second permeate 104 may be from 0.01 mol% to 5 mol%, for example, 1 mol% to 5 mol%, 2 mol% to 5 mol%, 3 mol% to 5 mol%, or 4 mol% to 5 mol%.

[0044] In the embodiments, the first membrane 110 and the second membrane 120 may contain any membrane material sufficient to provide a separation mechanism for hydrogen and carbonaceous compounds such as ethylene. For example, the membrane materials of the first membrane 110 and / or the second membrane 120 may include, but are not limited to, carbon molecular sieves, polymers, zeolites, metal-organic frameworks, transport-enhancing membranes, and mixed matrix membranes with different transport properties.

[0045] CMS membranes are typically produced by the pyrolysis of polymer precursors. For example, defect-free hollow fiber CMS membranes are well known to be produced by the pyrolysis of cellulose hollow fibers. In addition, many other polymers have been used to produce CMS membranes in both fibrous and dense membrane forms, with polyimide being a preferred choice. Polyimide has a high glass transition temperature, is easy to process, and performs better than most other polymer membranes even before pyrolysis.

[0046] In embodiments, the hollow fiber CMS membrane can be asymmetric. As used herein, the term "asymmetric" refers to a characteristic of the hollow fiber CMS membrane, wherein the hollow fiber CMS membrane has at least one relatively dense layer and at least one relatively non-dense layer. For example, in embodiments, one layer of the hollow fiber CMS membrane can be greater than or equal to 1 μm and less than or equal to 10 μm, and is denser than the second layer. The second layer can be thicker than the first layer, such as greater than or equal to 20 µm and less than or equal to 200 µm. In embodiments, the asymmetric membrane can be a solid consisting of an extremely thin, dense skin on a thick porous substructure, which can be the same or different material as the dense surface layer. In embodiments, the asymmetric membrane can be manufactured in a single step by phase inversion, or the thin layer can be coated onto a pre-prepared porous support using a dip-coating method. These layers in the asymmetric membrane can be produced by physical coating or by chemical modification. The asymmetric membrane can be in the form of a hollow fiber configuration or a membrane configuration. In the implementation scheme, the asymmetric membrane may include a third layer of the same or different materials as needed to enhance membrane performance.

[0047] The gas permeation characteristics of hollow fiber CMS membranes can be determined through gas permeation experiments. Two inherent properties are used to evaluate the separation performance of membrane materials: their "permeability" (a measure of the inherent productivity of hollow fiber CMS membranes) and their "selectivity" (a measure of the separation efficiency of hollow fiber CMS membranes). Permeability is typically determined in bar (barrer). ), which is based on the flux ( Divide by the partial pressure difference between the upstream and downstream sides of the hollow fiber CMS membrane ( ), and multiplied by the thickness of the hollow fiber CMS membrane ( ) to calculate.

[0048] Another term, “permeability,” is defined in this paper as the productivity of asymmetric hollow fiber membranes and is typically expressed in units of gas permeation (GPUs). The measurement is determined by dividing the permeability by the effective membrane separation layer thickness.

[0049] Finally, "selectivity" is defined in this paper as the ability of a gas to permeate through a hollow fiber CMS membrane or the permeability relative to another gas of the same nature. It is measured as a unitless ratio.

[0050] Now for reference Figure 3A cross-section of an asymmetric hollow carbon fiber 308 according to an embodiment is shown. The asymmetric hollow carbon fiber 308 may include an outer wall surrounding a hollow internal space 310. The outer wall may include a dense separation layer 314 and a porous support layer 312 between the dense separation layer 314 and the hollow internal space 310. The dense separation layer 314 may have a thickness of about 2 micrometers to about 6 micrometers. The dense separation layer 314 and the porous support layer 312 may include a nanographite structure having a crystallographic spacing of less than 3.6 angstroms and a basal plane greater than 1.3 nm. The dense separation layer 314 may include micropores having a radius greater than 4 angstroms. Methods for manufacturing such fibers and methods for manufacturing carbon molecular sieve membranes containing such fibers are also disclosed in the embodiments. Furthermore, methods for using carbon molecular sieve membranes containing such fibers to separate ethylene from a gas feed containing ethylene and ethane are also disclosed in the embodiments.

[0051] Unbound by theory, it is believed that the combination of properties of the asymmetric hollow carbon fibers disclosed herein (such as the thickness of the dense separation layer 314, interplanar spacing, basal plane size, and micropore size) is associated with high gas selectivity without a consequent decrease in gas permeability. It is believed that this combination of properties can synergistically provide improvements in both gas selectivity and gas permeability when compared to hollow carbon fibers that do not possess the disclosed combination of properties.

[0052] In embodiments, the hollow carbon fibers can be asymmetric. As used herein, the term "asymmetric" refers to the characteristic of hollow carbon fibers having at least one relatively dense layer (which may be a dense separation layer 314) and at least one relatively non-dense layer (which may be a porous support layer 312). For example, in embodiments, one layer of the hollow carbon may be greater than or equal to 2 µm and less than or equal to 6 µm, and is denser than the second layer. The second layer may be thicker than the first layer, such as greater than or equal to 20 µm and less than or equal to 200 µm. In one or more embodiments, the density of the dense separation layer 314 may be greater than the density of the porous support layer 120.

[0053] In one or more embodiments, the dense separation layer 314 may have a thickness of about 2 micrometers to about 6 micrometers. For example, the dense separation layer 314 may have a thickness of 2 micrometers to 6 micrometers, such as 2 micrometers to 5 micrometers, 2 micrometers to 4 micrometers, 2 micrometers to 3 micrometers, 3 micrometers to 6 micrometers, 3 micrometers to 5 micrometers, 3 micrometers to 4 micrometers, 4 micrometers to 6 micrometers, 4 micrometers to 5 micrometers, or 5 micrometers to 6 micrometers. Without being bound by theory, it is believed that when compared with asymmetric hollow carbon fibers that do not have the dense separation layer 110 (which has a thickness of about 2 micrometers to about 6 micrometers), the dense separation layer 110 having a thickness of about 2 micrometers to about 6 micrometers (when it is part of a combination of the properties of asymmetric hollow carbon fibers as disclosed herein) can improve the gas selectivity of the fiber.

[0054] In one or more embodiments, the dense separation layer 314 and the porous support layer 312 may comprise a nanographite structure. As used herein, the term "nanographite" refers to a structure comprising graphite crystals with a size less than 100 nm. In one or more embodiments, the nanographite structure may have a plane spacing of less than 3.6 Å. As used herein, the term "plane spacing" refers to the distance between the planes of carbon atoms forming the graphite crystals. For example, the nanographite structure may have a plane spacing of less than 3.5 Å, less than 3.4 Å, or even less than 3.35 Å. In some embodiments, the nanographite structure may have a plane spacing of 3.3 Å to 3.6 Å. For example, the nanographite structure may have a plane spacing of 3.3 Å to 3.6 Å, 3.3 Å to 3.5 Å, 3.3 Å to 3.4 Å, 3.4 Å to 3.6 Å, 3.4 Å to 3.5 Å, or 3.5 Å to 3.6 Å.

[0055] According to one or more embodiments, the basal plane of the nanographite structure can be greater than 1.3 nm. As used in this disclosure, the term "basal plane" refers to the size of the plane of carbon atoms forming the graphite crystal. For example, the basal plane of the nanographite structure can be greater than 1.5 nm, greater than 5 nm, greater than 10 nm, greater than 20 nm, greater than 30 nm, greater than 40 nm, or even greater than 50 nm. In some embodiments, the basal plane can be less than 100 nm. For example, the basal plane of the nanographite structure can be 1.3nm to 100nm, 1.3nm to 75nm, 1.3nm to 50nm, 1.3nm to 40nm, 1.3nm to 30nm, 1.3nm to 20nm, 1.3nm to 10nm, 1.3nm to 5nm, 1.3nm to 1.5nm, 1.5nm to 100nm, 1.5nm to 75nm, 1.5nm to 50nm, 1.5nm to 40nm, 1.5nm to 30nm, 1.5nm to 20nm, 1.5nm to 10nm, 1.5nm to 5nm, 5nm to 100nm, 5nm to 75nm, 5nm to 50nm, 5nm to 40nm, 5 nm to 30nm, 5nm to 20nm, 5nm to 10nm, 10nm to 100nm, 10nm to 75nm, 10nm to 50nm, 10nm to 40nm, 10nm to 30nm, 10nm to 20nm, 20nm to 100nm, 20nm to 75nm, 20nm to 50nm, 20nm to 40nm, 20nm to 30nm, 30nm to 100nm, 30nm to 75nm, 30nm to 50nm, 30nm to 40nm, 40nm to 100nm, 40nm to 75nm, 40nm to 50nm, 50nm to 100nm, 50nm to 75nm or 75nm to 100nm.

[0056] Unbound by theory, it is believed that nanographite structures with a basal plane greater than 1.3 nm and a crystal interplanar spacing less than 3.6 Å can be associated with asymmetric hollow carbon fibers, which exhibit improved gas selectivity and gas permeability when compared with asymmetric hollow carbon fibers that do not have such nanographite structures.

[0057] As disclosed herein, in one or more embodiments, the dense separation layer 314 may comprise micropores. In one or more embodiments, the micropores may have a radius greater than 4 Å, as determined by small-angle X-ray scattering. For example, the micropores may have radii greater than 4.2 Å, greater than 4.4 Å, greater than 4.6 Å, greater than 4.8 Å, greater than 5.0 Å, greater than 5.2 Å, greater than 5.4 Å, greater than 5.6 Å, greater than 5.8 Å, or even greater than 6.0 Å. In one or more embodiments, the micropores may have a radius less than 10 Å, as determined by small-angle X-ray scattering. For example, the micropores can have sizes of 4.2 Å to 10 Å, 4.2 Å to 9.5 Å, 4.2 Å to 9 Å, 4.2 Å to 8.5 Å, 4.2 Å to 8 Å, 4.2 Å to 7.5 Å, 4.2 Å to 7 Å, 4.2 Å to 6.5 Å, 4.2 Å to 6 Å, 4.2 Å to 5.5 Å, 4.2 Å to 5 Å, 4.2 Å to 4.5 Å, 4.5 Å to 10 Å, 4.5 Å to 9.5 Å, 4.5 Å to 9 Å, 4.5 Å to 8.5 Å, 4.5 Å to 8 Å, 4. 5Å to 7.5Å, 4.5Å to 7Å, 4.5Å to 6.5Å, 4.5Å to 6Å, 4.5Å to 5.5Å, 4.5Å to 5Å, 5Å to 10Å, 5Å to 9.5Å, 5Å to 9Å, 5Å to 8.5Å, 5Å to 8Å, 5Å to 7.5Å, 5Å to 7Å, 5Å to 6.5Å, 5Å to 6Å, 5Å to 5.5Å, 5.5Å to 10Å, 5.5Å to 9.5Å, 5.5Å to 9Å, 5.5Å to 8.5Å, 5.5Å to 8Å, 5.5Å to 7.5Å, 5.5Å to 7Å, 5.5Å to 6.5Å, 5.5Å to 6Å, 6Å to 10Å, 6Å to 9.5Å, 6Å to 9Å, 6Å to 8.5Å, 6Å to 8Å, 6Å to 7.5Å, 6Å to 7Å, 6Å to 6.5Å, 6.5Å to 10Å, 6.5Å to 9.5Å, 6.5Å to 9Å, 6.5Å to 8.5Å, 6.5Å to 8Å, 6.5Å to 7.5Å, 6.5Å to 7Å, 7Å to 10Å Radius ranges of 7 Å to 9.5 Å, 7 Å to 9 Å, 7 Å to 8.5 Å, 7 Å to 8 Å, 7 Å to 7.5 Å, 7.5 Å to 10 Å, 7.5 Å to 9.5 Å, 7.5 Å to 9 Å, 7.5 Å to 8.5 Å, 7.5 Å to 8 Å, 8 Å to 10 Å, 8 Å to 9.5 Å, 8 Å to 9 Å, 8.5 Å to 10 Å, 8.5 Å to 9.5 Å, 8.5 Å to 9 Å, 9 Å to 10 Å, 9 Å to 9.5 Å, or 9.5 Å to 10 Å. Unbound by theory, it is believed that asymmetric hollow carbon fibers containing a dense separation layer 110 with micropores larger than 4 Å in radius, as determined by a small angle, can improve the gas selectivity of asymmetric hollow carbon fibers when compared with asymmetric hollow fibers that do not contain micropores with a radius greater than 4 Å.

[0058] In one or more embodiments, the asymmetric hollow carbon fibers may have a nanocrystalline graphite structure. As used in this disclosure, the term "nanocrystalline graphite" refers to fibers that have transformed from an amorphous or non-crystalline carbon structure to a crystalline graphite structure. The transformation from amorphous carbon to crystalline graphite can be determined using Raman spectroscopy. Raman spectroscopy uses light to measure molecular vibrations, and these vibrations can be used to determine characteristics such as molecular structure and crystallinity. Without being bound by theory, it is believed that as the carbon fiber transforms from an amorphous structure to a nanocrystalline structure, the intensity ratio of the Raman D peak to the Raman G peak initially increases, and then decreases. This "flip" in the intensity ratio is believed to be used to determine whether the asymmetric hollow carbon fiber 100 has transformed from an amorphous carbon structure to a nanocrystalline graphite structure.

[0059] In one or more embodiments, the asymmetric hollow carbon fiber 308 may contain less than 50% pyrrole-based nitrogen as a percentage of the total nitrogen in the fiber. For example, the asymmetric hollow carbon fiber 308 may contain less than 45% pyrrole-based nitrogen as a percentage of the total nitrogen in the fiber, such as less than 40%, less than 35%, less than 30%, less than 25%, less than 20%, less than 15%, or even less than 10% pyrrole-based nitrogen as a percentage of the total nitrogen in the fiber. Without being bound by theory, it is believed that a pyrrole-based nitrogen percentage of less than 50% of the total nitrogen in the fiber can be indicative of a comparison with a fiber having a pyrrole-based nitrogen percentage of more than 50% of the total nitrogen in the fiber, which has been formed by pyrolysis at high temperatures.

[0060] In one or more embodiments, the dense separation layer 314 of the asymmetric hollow carbon fiber 308 may contain oxygen in an amount greater than 5 atomic% of the total atomic mass of the dense separation layer 314. In one or more embodiments, the dense separation layer 314 of the asymmetric hollow carbon fiber 100 may contain oxygen in an amount less than 15 atomic% of the total atomic mass of the dense separation layer 314. For example, the asymmetric hollow carbon fiber 100 may contain oxygen in an amount from 5 atomic% to 15 atomic% of the total atoms of the dense separation layer 110, such as 5 atomic% to 12.5 atomic%, 5 atomic% to 10 atomic%, 5 atomic% to 7.5 atomic%, 7.5 atomic% to 15 atomic%, 7.5 atomic% to 12.5 atomic%, 7.5 atomic% to 10 atomic%, 10 atomic% to 15 atomic%, 10 atomic% to 12.5 atomic%, or 12.5 atomic% to 15 atomic%. Unbound by theory, it is believed that when compared with fibers with oxygen content of less than 5 atomic% or greater than 15 atomic%, the total atomic oxygen content of the dense separation layer, ranging from 5 atomic% to 15 atomic%, can be correlated with the improved gas permeability and selectivity of the fiber.

[0061] In one or more embodiments, the asymmetric hollow carbon fiber 308 may have a D(002) peak of less than 4.0 Å in transmission, as measured by X-ray scattering at an energy level of 17 keV. For example, the asymmetric hollow carbon fiber 100 may have a D(002) peak of less than 3.9 Å, less than 3.8 Å, less than 3.7 Å, less than 3.6 Å, or even less than 3.5 Å. In some embodiments, the D(002) peak may be at least 3.3 Å in transmission. For example, asymmetric hollow carbon fiber 100 can have 3.3 Å to 4.0 Å, 3.3 Å to 3.9 Å, 3.3 Å to 3.8 Å, 3.3 Å to 3.7 Å, 3.3 Å to 3.6 Å, 3.3 Å to 3.5 Å, 3.3 Å to 3.4 Å, 3.4 Å to 4.0 Å, 3.4 Å to 3.9 Å, 3.4 Å to 3.8 Å, 3.4 Å to 3.7 Å, 3.4 Å to 3.6 Å, 3.4 Å to 3.5 Å, 3.5 Å to D(002) peaks at 4.0 Å, 3.5 Å to 3.9 Å, 3.5 Å to 3.8 Å, 3.5 Å to 3.7 Å, 3.5 Å to 3.6 Å, 3.6 Å to 4.0 Å, 3.6 Å to 3.9 Å, 3.6 Å to 3.8 Å, 3.6 Å to 3.7 Å, 3.7 Å to 4.0 Å, 3.7 Å to 3.9 Å, 3.7 Å to 3.8 Å, 3.8 Å to 4.0 Å, 3.8 Å to 3.9 Å, or 3.9 Å to 4.0 Å. Unbound by theory, it is believed that, as indicated by D(002) peaks less than 4.0 Å measured by X-ray scattering at an energy level of 17 keV, a large portion of the fiber undergoes carbonization to form asymmetric hollow carbon fiber 308.

[0062] In one or more embodiments, a plurality of asymmetric hollow carbon fibers are combined to form a carbon molecular sieve membrane. In one embodiment, the carbon molecular sieve membrane may include channels formed between dense separation layers 314 of adjacent fibers. In another embodiment, the carbon molecular sieve membrane may not include an external support.

[0063] In embodiments, the asymmetric membrane can be a solid consisting of an extremely thin, dense skin on a thick porous structure, the thick porous structure being the same or a different material as the dense surface layer. In embodiments, the asymmetric membrane can be manufactured in a single step via phase inversion, or a thin layer can be coated onto a pre-prepared porous support using a dip-coating method. These layers in the asymmetric membrane can be produced by physical coating or by chemical modification. The asymmetric membrane can be in the form of a hollow fiber configuration. In embodiments, the asymmetric membrane can, as needed, include a third layer of the same or a different material to enhance membrane performance.

[0064] Reverse selective membrane

[0065] In some embodiments, the first membrane 110 may be a reverse-selective carbon molecular sieve (CMS) membrane. In other embodiments, the second membrane 120 may be a reverse-selective carbon molecular sieve (CMS) membrane. In embodiments, the first membrane 110 or the second membrane 120 may be manufactured by any of the methods disclosed in U.S. Application No. 2022 / 037,840, “Reverse Selective / Surface Flow Polyimide Derived CMS Membrane for Gas Separation” and / or U.S. Application No. 2022 / 037,838, “Process of Making Reverse Selective / Surface Flow CMS Membrane for Gas Separation”, the entire contents of which are incorporated herein by reference.

[0066] In the implementation, the reverse-selective hollow fiber CMS membrane that has been pyrolyzed or oxidized can have an ethylene / hydrogen selectivity of greater than or equal to 5, such as greater than or equal to 5 and less than or equal to 50, greater than or equal to 10 and less than or equal to 50, greater than or equal to 15 and less than or equal to 50, greater than or equal to 20 and less than or equal to 50, greater than or equal to 25 and less than or equal to 50, greater than or equal to 30 and less than or equal to 50, greater than or equal to 35 and less than or equal to 50, greater than or equal to 40 and less than or equal to 50, greater than or equal to 45 and less than or equal to 50, greater than or equal to 5 and less than or equal to 40, such as greater than or equal to 5 and less than or equal to 35, greater than or equal to 5 and less than or equal to 30, greater than or equal to 5 and less than or equal to 25, greater than or equal to 5 and less than or equal to 20, greater than or equal to 5 and less than or equal to 15, or even greater than or equal to 5 and less than or equal to 10. It is envisioned that the range of ethylene / hydrogen selectivity may be greater than or equal to any of the selectivity described herein and less than or equal to any of the selectivity described herein.

[0067] In the implementation, the reverse-selective hollow fiber CMS membrane that has been pyrolyzed and oxidized can have a carbon dioxide / hydrogen selectivity of greater than or equal to 5, such as greater than or equal to 5 and less than or equal to 50, greater than or equal to 10 and less than or equal to 50, greater than or equal to 15 and less than or equal to 50, greater than or equal to 20 and less than or equal to 50, greater than or equal to 25 and less than or equal to 50, greater than or equal to 30 and less than or equal to 50, greater than or equal to 35 and less than or equal to 50, greater than or equal to 40 and less than or equal to 50, greater than or equal to 45 and less than or equal to 50, greater than or equal to 5 and less than or equal to 40, greater than or equal to 5 and less than or equal to 35, greater than or equal to 5 and less than or equal to 30, greater than or equal to 5 and less than or equal to 25, greater than or equal to 5 and less than or equal to 20, greater than or equal to 5 and less than or equal to 15, or even greater than or equal to 5 and less than or equal to 10. It is envisioned that the range of carbon dioxide / hydrogen selectivity may be greater than or equal to any of the selectivity described herein and less than or equal to any of the selectivity described herein.

[0068] In the implementation scheme, when measuring an analytical material stream containing ethylene in the permeate and hydrogen in the residue at a temperature greater than or equal to 20°C and less than or equal to 35°C, the pyrolyzed and oxidized reverse selective hollow fiber CMS membrane can have an ethylene permeability greater than or equal to 400 GPU. For example, ethylene permeability can be greater than or equal to 400 GPUs and less than or equal to 800 GPUs, greater than or equal to 400 GPUs and less than or equal to 800 GPUs, greater than or equal to 450 GPUs and less than or equal to 800 GPUs, greater than or equal to 500 GPUs and less than or equal to 800 GPUs, greater than or equal to 550 GPUs and less than or equal to 800 GPUs, greater than or equal to 600 GPUs and less than or equal to 800 GPUs, greater than or equal to 650 GPUs and less than or equal to 800 GPUs, greater than or equal to 700 GPUs and less than or equal to 800 GPUs, greater than or equal to 750 GPUs and less than or equal to 700 GPUs, greater than or equal to 400 GPUs and less than or equal to 650 GPUs, greater than or equal to 400 GPUs and less than or equal to 600 GPUs, greater than or equal to 400 GPUs and less than or equal to 550 GPUs. GPUs, greater than or equal to 400 GPUs and less than or equal to 500 GPUs, or even greater than or equal to 400 GPUs and less than or equal to 450 GPUs. It is envisioned that the range of ethylene permeability can be greater than or equal to any of the permeability ranges described herein and less than or equal to any of the permeability ranges described herein.

[0069] In the implementation, when measuring an analytical material stream containing carbon dioxide in the permeate and hydrogen in the residue at a temperature greater than or equal to 20°C and less than or equal to 35°C, the pyrolyzed and oxidized reverse selective hollow fiber CMS membrane can have a carbon dioxide permeability greater than or equal to 1200 GPU. For example, carbon dioxide permeability can be greater than or equal to 1200 GPUs and less than or equal to 1800 GPUs, greater than or equal to 1250 GPUs and less than or equal to 1800 GPUs, greater than or equal to 1300 GPUs and less than or equal to 1800 GPUs, greater than or equal to 1350 GPUs and less than or equal to 1800 GPUs, greater than or equal to 1400 GPUs and less than or equal to 1500 GPUs, greater than or equal to 1450 GPUs and less than or equal to 1800 GPUs, greater than or equal to 1500 GPUs and less than or equal to 1800 GPUs, greater than or equal to 1550 GPUs and less than or equal to 1800 GPUs, greater than or equal to 1600 GPUs and less than or equal to 1800 GPUs, greater than or equal to 1650 GPUs and less than or equal to 1800 GPUs, greater than or equal to 1700 GPUs and less than or equal to 1800 GPUs, greater than or equal to 1750 GPUs and less than or equal to 1800 GPUs, and greater than or equal to 1200 GPUs and less than or equal to 1750 GPUs. The range of permeability is defined as follows: 1200 GPUs or more and 1700 GPUs or less; 1200 GPUs or more and 1650 GPUs or more; 1200 GPUs or more and 1600 GPUs or more; 1200 GPUs or more and 1550 GPUs or more; 1200 GPUs or more and 1500 GPUs or more; 1200 GPUs or more and 1450 GPUs or more; 1200 GPUs or more and 1400 GPUs or more; 1200 GPUs or more and 1350 GPUs or more; 1200 GPUs or more and 1300 GPUs or more; 120 GPUs or more and 1300 GPUs or more; or even 1200 GPUs or more and 1250 GPUs or more. It is envisioned that the range of carbon dioxide permeability can be greater than or equal to any of the permeability ranges described herein and less than or equal to any of the permeability ranges described herein.

[0070] Superselective membrane

[0071] In some embodiments, the first membrane 110 may be a superselective carbon molecular sieve (CMS) membrane. In other embodiments, the second membrane 120 may be a superselective carbon molecular sieve (CMS) membrane. In embodiments, the first membrane 110 or the second membrane 120 may be manufactured by any of the methods disclosed in U.S. Application No. 2022 / 037,843, “Methods for Manufacturing Hollow Fiber Carbon Membranes,” the entire contents of which are incorporated herein by reference.

[0072] In the implementation scheme, the superselective hollow fiber CMS membrane has a value greater than or equal to 5, such as greater than or equal to 5 and less than or equal to 500, greater than or equal to 10 and less than or equal to 500, greater than or equal to 25 and less than or equal to 500, greater than or equal to 500 and less than or equal to 500, greater than or equal to 75 and less than or equal to 500, greater than or equal to 75 and less than or equal to 500, greater than or equal to 100 and less than or equal to 500, greater than or equal to 125 and less than or equal to 500, greater than or equal to 150 and less than or equal to 500, greater than or equal to 175 and less than or equal to 500, greater than or equal to 200 and less than or equal to 500, greater than or equal to 225 and less than or equal to 500, greater than or equal to 250 and less than or equal to 500, greater than or equal to 275 and less than or equal to 500, greater than or equal to 500, and so on. Hydrogen / ethylene selectivity is defined as follows: 300 and less than or equal to 500, greater than or equal to 325 and less than or equal to 500, greater than or equal to 375 and less than or equal to 500, greater than or equal to 400 and less than or equal to 500, greater than or equal to 425 and less than or equal to 500, greater than or equal to 450 and less than or equal to 500, greater than or equal to 475 and less than or equal to 500, greater than or equal to 5 and less than or equal to 450, greater than or equal to 5 and less than or equal to 400, such as greater than or equal to 5 and less than or equal to 350, greater than or equal to 5 and less than or equal to 300, greater than or equal to 5 and less than or equal to 250, greater than or equal to 5 and less than or equal to 200, greater than or equal to 5 and less than or equal to 150, greater than or equal to 5 and less than or equal to 100, or even greater than or equal to 5 and less than or equal to 50. It is envisioned that the range of hydrogen / ethylene selectivity can be greater than or equal to any of the selectivities described herein and less than or equal to any of the selectivities described herein.

[0073] In the implementation scheme, when measured at a temperature greater than or equal to 20°C and less than or equal to 35°C, the superselective hollow fiber CMS membrane has a permeate permeability greater than or equal to 50 GPUs. For example, hydrogen permeability can be greater than or equal to 200 GPUs and less than or equal to 800 GPUs, greater than or equal to 200 GPUs and less than or equal to 800 GPUs, greater than or equal to 250 GPUs and less than or equal to 800 GPUs, greater than or equal to 300 GPUs and less than or equal to 800 GPUs, greater than or equal to 350 GPUs and less than or equal to 800 GPUs, greater than or equal to 400 GPUs and less than or equal to 800 GPUs, greater than or equal to 500 GPUs and less than or equal to 800 GPUs, greater than or equal to 550 GPUs and less than or equal to 800 GPUs, greater than or equal to 600 GPUs and less than or equal to 800 GPUs, greater than or equal to 650 GPUs and less than or equal to 800 GPUs, greater than or equal to 700 GPUs and less than or equal to 800 GPUs, greater than or equal to 750 GPUs and less than or equal to 800 GPUs, greater than or equal to 40 ... The range of hydrogen permeability is envisioned to be greater than or equal to 750 GPUs and less than or equal to 400 GPUs and less than or equal to 700 GPUs, greater than or equal to 400 GPUs and less than or equal to 650 GPUs, greater than or equal to 400 GPUs and less than or equal to 600 GPUs, greater than or equal to 400 GPUs and less than or equal to 550 GPUs, greater than or equal to 400 GPUs and less than or equal to 500 GPUs, or even greater than or equal to 400 GPUs and less than or equal to 450 GPUs.

[0074] The two-stage membrane separation unit 100 is expected to be used in combination with other separation technologies, such as cryogenic distillation columns, as a hybrid process to achieve products with higher purity. The use of the two-stage membrane separation unit will reduce the energy load required for cryogenic distillation, while allowing for a purer starting feed.

[0075] Now for reference Figure 2 A two-stage membrane separation device 200 suitable for separating a target chemical substance from a secondary chemical substance is described, the two-stage membrane separation device being substantially similar to Figure 1 The device 100 is depicted. Figure 2 The device 200 described and Figure 1 The differences between the depicted devices 100 involve the introduction of recirculated material streams.

[0076] Still referencing Figure 2 According to one or more embodiments, the mixed gas 101 can be introduced into the first membrane 210 through a gas inlet. The mixed gas 101 may contain [missing information - likely related to...]. Figure 1 The same target chemicals and secondary chemicals disclosed in [the document].

[0077] After the mixed gas 101 is introduced into the first membrane 210 through the gas inlet, the mixed gas separates into a first permeate 203 and a first permeate 202 at the first membrane 210. The first permeate 203 may contain an increased concentration of the target chemical substance. The first permeate 203 may be introduced into the second membrane 220.

[0078] In some embodiments, the concentration of the target chemical substance in the first residue 203 can be from 5 mol% to 40 mol%, for example, 10 mol% to 40 mol%, 15 mol% to 40 mol%, 20 mol% to 40 mol%, 25 mol% to 40 mol%, 30 mol% to 40 mol%, 35 mol% to 40 mol%, 5 mol% to 30 mol%, 5 mol% to 20 mol%, or even 5 mol% to 10 mol.

[0079] In some embodiments, the concentration of the secondary chemical substance in the first residue 103 may be 60 mol% to 95 mol%, for example 65 mol% to 95 mol%, 70 mol% to 95 mol%, 75 mol% to 95 mol%, 80 mol% to 95 mol%, 85 mol% to 95 mol%, 90 mol% to 95 mol%, 60 mol% to 90 mol%, 60 mol% to 80 mol%, or even 60 mol% to 70 mol%.

[0080] The first permeate 202 may contain a secondary chemical substance at an increased concentration. The first permeate 202 may be introduced into the atmosphere outside the mechanical device containing the first membrane 220.

[0081] In some embodiments, the concentration of the secondary chemical substance in the first permeate 102 may be 90 mol% to 99 mol%, for example 92 mol% to 99 mol%, 94 mol% to 99 mol%, 96 mol% to 99 mol%, or 98 mol% to 99 mol%.

[0082] In some embodiments, the concentration of the target chemical substance in the first permeate 202 can be from 1 mol% to 10 mol%, for example, from 2 mol% to 10 mol%, from 4 mol% to 10 mol%, from 6 mol% to 10 mol%, or from 8 mol% to 10 mol%.

[0083] After the first permeate 203 is introduced into the second membrane 120, the first permeate is separated at the second membrane 220 into a second permeate 205 and a second permeate 204. The second permeate 205 may contain a higher concentration of secondary chemicals. The second permeate 205 may be combined with the mixed gas 101 to form a recirculated feed stream 201 upstream of the second permeate 205.

[0084] In some embodiments, the concentration of the secondary chemical substance in the second residue 205 can be from 50 mol% to 95 mol%, for example, 50 mol% to 95 mol%, 55 mol% to 95 mol%, 60 mol% to 95 mol%, 65 mol% to 95 mol%, 70 mol% to 95 mol%, 75 mol% to 95 mol%, 80 mol% to 95 mol%, 85 mol% to 95 mol%, 90 mol% to 95 mol%, 50 mol% to 90 mol%, 50 mol% to 80 mol%, 50 mol% to 70 mol%, or even 50 mol% to 60 mol%.

[0085] In some embodiments, the concentration of the target chemical substance in the second residue 205 can be from 5 mol% to 50 mol%, for example, 10 mol% to 50 mol%, 15 mol% to 50 mol%, 20 mol% to 50 mol%, 25 mol% to 50 mol%, 30 mol% to 50 mol%, 35 mol% to 50 mol%, 40 mol% to 50 mol%, 45 mol% to 50 mol%, 5 mol% to 40 mol%, 5 mol% to 30 mol%, 5 mol% to 20 mol%, or even 5 mol% to 10 mol.

[0086] The second permeate 204 may contain an increased concentration of the target chemical substance. The second permeate 204 may be introduced into an atmosphere outside the mechanical device housing the second membrane 220. In some embodiments, the concentration of the target chemical substance in the second permeate 204 may be 90 mol% to 98 mol%, for example, 92 mol% to 98 mol%, 94 mol% to 98 mol%, or 96 mol% to 98 mol%. In some embodiments, the concentration of the secondary chemical substance in the second permeate 204 may be 2 mol% to 10 mol%, for example, 4 mol% to 10 mol%, 6 mol% to 10 mol%, or 8 mol% to 10 mol%.

[0087] although Figure 1 and Figure 2The depicted membrane separation device comprises two stages, but the system is contemplated to contain any number of stages. For example, the membrane separation device may comprise three stages, wherein the second permeate 104 or 204 is introduced into a third membrane, wherein the second permeate 104 or 204 is further separated into a third permeate and a second permeate. The third membrane may be identical to the first or second membrane, and the third permeate may contain an elevated concentration of the target chemical substance, and the third permeate may contain an elevated concentration of at least one other chemical substance.

[0088] Example

[0089] This document provides embodiments that may disclose one or more implementations of this disclosure. However, these embodiments should not be construed as limiting the claims made below.

[0090] hydrogen and ethylene

[0091] Table 1 summarizes the performance data for various combinations of reverse-selective and superselective membranes as described in the embodiments herein. Advanced carbon molecular sieve membranes with both reverse-selective and superselective gas delivery characteristics are utilized, and these membranes can be manufactured according to any method described or disclosed above. The mixed gas feed comprises 50% ethylene and 50% hydrogen. In each case, the feed pressure is 52 psig, and the first permeate pressure is 2 psig. The feed temperature is 35°C, and the flow rate is 150 sccm. All concentrations are listed in mol% (%).

[0092] Four process simulation examples were investigated to understand the multi-stage membrane process proposed in this invention. The reverse-selective membrane showed an ethylene permeation of 611 GPUs and a hydrogen permeation of 37 GPUs, with an ethylene / hydrogen selectivity of 16.67. The superselective membrane showed an ethylene permeation of 2.7 GPUs and a hydrogen permeation of 506 GPUs, with a hydrogen / ethylene selectivity of 186.

[0093]

[0094] As seen above, embodiments 1 to 4 of the present invention show that, regardless of the order of the reverse selective membrane and the superselective membrane, the system produces very similar results for the same mixed gas.

[0095] Embodiment 1 of the present invention utilizes a reverse-selective membrane, followed by a superselective membrane. After separation of the mixed gas by the reverse-selective membrane, the first permeate contains 90.36 mol% ethylene. After separation of the first permeate by the superselective membrane, the second permeate contains 98.97 mol% hydrogen. For Embodiment 3 of the present invention, similar results are observed, wherein the order of the reverse-selective and superselective membranes is reversed. After separation of the mixed gas by the superselective membrane, the first permeate contains 98.94 mol% hydrogen. After separation of the first permeate by the reverse-selective membrane, the second permeate contains 90.61 mol% ethylene.

[0096] As demonstrated in Examples 1 and 3 of this invention, each membrane captures the majority of the hydrogen or the majority of the ethylene, regardless of the order in which the membranes are placed. Furthermore, the membrane system achieves these compositions without the need for interstage compression. Therefore, each component (hydrogen or ethylene) can be isolated and separated to the desired purity.

[0097] Embodiment 2 of the present invention utilizes a reverse-selective membrane, followed by a superselective membrane with recirculation. After separation of the mixed gas via the reverse-selective membrane, the first permeate contains 96.16 mol% ethylene. After separation of the first permeate via the superselective membrane, the second permeate contains 95.69 mol% hydrogen. For Embodiment 4 of the present invention, similar results are observed, wherein the order of the reverse-selective and superselective membranes is reversed, and recirculation is still included. After separation of the mixed gas via the superselective membrane, the first permeate contains 95.56 mol% hydrogen. After separation of the first permeate via the reverse-selective membrane, the second permeate contains 96.02 mol% ethylene.

[0098] It is noteworthy that, compared to Examples 1 and 3 of the present invention, where hydrogen purity is 98.97 mol% and 98.94 mol%, the addition of a recirculated feed stream (as seen in Examples 2 and 4) reduces hydrogen purity. However, compared to Examples 1 and 3 of the present invention, where ethylene purity is 90.36 mol% and 90.61 mol%, the recirculated feed stream in each of Examples 2 and 4 allows the system to achieve higher ethylene purity. Without being bound by any theory, it is believed that the recirculated feed stream system results in lower hydrogen purity because the addition of additional ethylene to the feed stream dilutes the hydrogen in the feed stream, which in turn results in a lower hydrogen concentration and lower drive force. Alternatively, without being bound by any theory, it is believed that the recirculated feed stream system results in lower hydrogen purity in exchange for a higher hydrogen recovery rate. Therefore, a recirculation system can be utilized where higher ethylene purity is desired or required.

[0099] Comparative Examples C1 and C2 showed similar results in achieving purity of a single composition. For example, Comparative Example C1 showed that approximately 90 mol% ethylene purity was achieved using two reverse-selective membranes, while Comparative Example C2 showed that approximately 98 mol% hydrogen purity was achieved using two superselective membranes. However, without the combination of both reverse-selective and superselective membranes, only one substance with relatively high purity can be achieved, and interstage compression is required, thus increasing the system's energy demand.

[0100] hydrogen and carbon dioxide

[0101] Table 2 summarizes the performance data for various combinations of reverse-selective and superselective membranes as described in the embodiments herein. Advanced carbon molecular sieve membranes with both reverse-selective and superselective gas delivery characteristics are utilized, and these membranes can be manufactured according to any of the methods described or disclosed above. The mixed gas feed comprises 50% carbon dioxide and 50% hydrogen. In each case, the feed pressure is 52 psig, and the first permeate pressure is 2 psig. The feed temperature is 35°C, and the flow rate is 150 sccm. All concentrations are listed in mol% (%).

[0102] Four process simulation examples were investigated to understand the multi-stage membrane process proposed in this invention. The reverse-selective membrane exhibited 1500 GPU of CO2 permeability and 75 GPU of hydrogen permeability, with a CO2 / H2 selectivity of 20. The superselective membrane exhibited 15 GPU of CO2 permeability and 500 GPU of hydrogen permeability, with a hydrogen / CO2 selectivity of 33.

[0103]

[0104] As seen above, embodiments 5 to 8 of the present invention show that, regardless of the order of the reverse selective membrane and the superselective membrane, the system produces very similar results for the same mixed gas.

[0105] Embodiment 5 of the present invention utilizes a reverse-selective membrane, followed by a superselective membrane. After separation of the mixed gas via the reverse-selective membrane, the first permeate contains 91.8 mol% carbon dioxide. After separation of the first permeate via the superselective membrane, the second permeate contains 94.8 mol% hydrogen. For Embodiment 7 of the present invention, similar results are observed, wherein the order of the reverse-selective and superselective membranes is reversed. After separation of the mixed gas via the superselective membrane, the first permeate contains 94.7 mol% hydrogen. After separation of the first permeate via the reverse-selective membrane, the second permeate contains 92.0 mol% carbon dioxide.

[0106] As demonstrated in Examples 5 and 7 of the present invention, each membrane captures the majority of hydrogen or the majority of carbon dioxide, regardless of the order in which the membranes are placed. Furthermore, the membrane system achieves these compositions without the need for interstage compression. Therefore, each component (hydrogen or carbon dioxide) can be isolated and separated to the desired purity.

[0107] Embodiment 6 of the present invention utilizes a reverse-selective membrane, followed by a superselective membrane with recirculation. After separation of the mixed gas via the reverse-selective membrane, the first permeate contains 91.2 mol% carbon dioxide. After separation of the first permeate via the superselective membrane, the second permeate contains 95.2 mol% hydrogen. For Embodiment 8 of the present invention, similar results are observed, wherein the order of the reverse-selective and superselective membranes is reversed, and recirculation is still included. After separation of the mixed gas via the superselective membrane, the first permeate contains 96.2 mol% hydrogen. After separation of the first permeate via the reverse-selective membrane, the second permeate contains 88.8 mol% carbon dioxide.

[0108] It is worth noting that, compared to Examples 5 and 7 of the present invention, where the carbon dioxide purity is 91.8 mol% and 92.0 mol%, the addition of a recirculated feed stream (as seen in Examples 6 and 8) reduces the carbon dioxide purity. However, compared to Examples 5 and 7 of the present invention, where the hydrogen purity is 94.8 mol% and 94.7 mol%, the recirculated feed stream in each of Examples 6 and 8 allows the system to achieve higher hydrogen purity. Therefore, a recirculation system can be utilized when higher hydrogen purity is desired or required.

[0109] Comparative Examples C3 and C4 showed similar results in achieving purity of a single composition. For example, Comparative Example C3 showed that approximately 91 mol% carbon dioxide purity was achieved using two reverse-selective membranes, while Comparative Example C4 showed that approximately 95 mol% hydrogen purity was achieved using two superselective membranes. However, without the combination of both reverse-selective and superselective membranes, only one substance with relatively high purity can be achieved, and interstage compression is required, thus increasing the system's energy demand.

[0110] It should now be understood that reverse-selective and superselective membranes can be used interchangeably in the separation of ethylene and hydrogen. Regardless of the membrane order, very similar product purities are achieved. Furthermore, this combination of reverse-selective and superselective membranes allows for the purification of both ethylene and hydrogen in the same system without the need for interstage recompression.

[0111] The subject matter of this disclosure has been described in detail and with reference to specific embodiments. It should be understood that any detailed description of a component or feature of an embodiment does not necessarily imply that such component or feature is necessary for a particular embodiment or any other embodiment. Furthermore, it will be apparent to those skilled in the art that various modifications and changes can be made to the described embodiments without departing from the spirit and scope of the claimed subject matter.

[0112] It should be noted that one or more of the appended claims use the term "wherein" as a transitional expression. For the purpose of defining this technology, it should be noted that this term is introduced in the claims as an open transitional phrase used to introduce a description of a series of features of the structure, and should be interpreted in a similar manner to the more commonly used open prepositional term "comprising".

[0113] Any quantitative value expressed in this application may be considered to include open-ended implementations consistent with the transitional phrases “comprising” or “including”.

[0114] It should be understood that when the first component is described as "containing" the second component, it is anticipated in some embodiments that the first component is "composed of" or "substantially composed of" the second component. It should also be understood that when the first component is described as "containing" the second component, it is anticipated in some embodiments that the first component contains at least 10%, at least 20%, at least 30%, at least 40%, at least 50%, at least 60%, at least 70%, at least 80%, at least 90%, at least 95%, or even at least 99% of the second component (where % is mole%, unless otherwise specified).

[0115] It should be understood that any two quantitative values ​​assigned to a certain characteristic can constitute a range for that characteristic, and all combinations of ranges formed by all said quantitative values ​​of a given characteristic are considered in this disclosure. It should be understood that in some embodiments, the compositional range of a chemical component in the composition should be understood as a mixture containing isomers of that component. In other embodiments, the chemical compound may be present in alternative forms, such as derivatives, salts, hydroxides, etc.

[0116] It should also be noted that references to “at least one” components, elements, etc. in this article should not be used to generate alternative uses of the article “a / an” and should be limited to inferences about a single component, element, etc.

[0117] It should also be understood that a flow can be named for its components, and the named components can be the main components of the flow (such as the contents of the flow comprising 50 wt% (wt%), 70 wt%, 90 wt%, 95 wt%, 99 wt%, 99.5 wt%, or even 99.9 wt% to 100 wt%) of the flow contents). It should also be understood that when a flow containing a component is disclosed as being transferred from one system component to another system component, that component of the flow is disclosed as being transferred from that system component to the other system component. For example, a disclosed "mixed gas" transfer from a first system component to a second system component should be understood as equivalently disclosing "hydrogen" transfer from the first system component to the second system component, etc.

Claims

1. A method for separating hydrogen (H2) and carbonaceous compounds, the method comprising: A mixed gas containing a target chemical substance and a secondary chemical substance is introduced into a first membrane; Separate a first residue and a first permeate at the first membrane, wherein the first residue contains an elevated concentration of the target chemical substance, and the first permeate contains an elevated concentration of the secondary chemical substance. The first permeate is introduced into the second membrane; as well as A second residue and a second permeate are separated at the second membrane, wherein the second residue contains an elevated concentration of the secondary chemical substance, and the second permeate contains an elevated concentration of the target chemical substance. The target chemical substance is H2 or the carbon-containing compound, the secondary chemical substance is H2 or the carbon-containing compound, and the target chemical substance is different from the secondary chemical substance.

2. The method according to claim 1, wherein the carbon-containing compound comprises ethylene (C2H4).

3. The method according to claim 1 or 2, wherein: Separating the first quaternite and the first permeate at the first membrane includes introducing the mixed gas into a reverse-selective membrane, the reverse-selective membrane comprising a carbon molecular sieve (CMS) membrane, the CMS membrane being operable to produce the first quaternite having an elevated concentration of the target chemical substance and the first permeate having an elevated concentration of the secondary chemical substance. The target chemical substance is H2.

4. The method according to claim 3, wherein Separating the second permeate and the second osmotic material at the second membrane includes introducing the first permeate into a superselective membrane, the superselective membrane comprising a carbon molecular sieve (CMS) membrane, the CMS membrane being operable to produce the second osmotic material having an elevated concentration of the target chemical substance and the second permeate having an elevated concentration of the secondary chemical substance.

5. The method according to claim 1 or 2, wherein: Separating the first permeate and the first osmotic residue at the first membrane includes introducing the mixed gas into a superselective membrane, the superselective membrane comprising a carbon molecular sieve (CMS) membrane, the CMS membrane being operable to produce the first osmotic residue having an elevated concentration of the target chemical substance and the first osmotic residue having an elevated concentration of the secondary chemical substance. The target chemical substance is C2H4.

6. The method according to claim 5, wherein: Separating the second residue and the second permeate at the second membrane includes introducing the first residue into a reverse selective membrane, wherein the reverse selective membrane is operable to produce the second residue having an elevated concentration of the target chemical substance and the second permeate having an elevated concentration of the secondary chemical substance.

7. The method according to any one of claims 3 to 6, wherein the reverse selective membrane is a hollow fiber or membrane CMS membrane comprising a pyrolytic and oxidized polyimide membrane.

8. The method of claim 7, wherein the reverse selective membrane has a selectivity of 10 or greater.

9. The method according to claim 7 or 8, wherein when the measurement is performed at a temperature greater than or equal to 20°C and less than or equal to 35°C, the reverse selective membrane has a permeate permeability greater than or equal to 100 GPUs.

10. The method according to any one of claims 3 to 6, wherein the superselective membrane is a CMS membrane comprising a plurality of asymmetric hollow carbon fibers, the plurality of asymmetric hollow fibers comprising an outer wall surrounding a hollow internal space.

11. The method of claim 10, wherein: The outer wall includes a dense separation layer with a thickness of 2 to 6 micrometers and a porous support layer located between the dense separation layer and the hollow internal space; and Channels are formed between the densely separated layers of adjacent asymmetric hollow carbon fibers.

12. The method according to claim 10 or 11, wherein the dense separation layer and the porous support layer comprise: A nanographite structure having a crystal plane spacing of less than 3.6 angstroms; A basal plane, said basal plane being greater than 1.3 nm; and The dense separation layer includes micropores having a radius greater than 4 angstroms.

13. The method according to any preceding claim, further comprising: The second permeate is introduced into the third membrane; as well as The third permeate and the third permeate are separated at the third membrane.

14. The method of claim 13, wherein: The third membrane is the same as the first membrane or the second membrane; and The third permeate contains an increased concentration of the target chemical substance, and the third residual contains an increased concentration of the secondary chemical substance.

15. The method according to any preceding claim, further comprising: The second permeate is combined with the mixed gas.

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