Methods for the separation of co 2 from a gas stream

Abstract

Disclosed herein are 3-stage membrane separation processes for capturing CO2 from a feed gas. The processes can employ three selectively permeable membranes, which may be the same or different. In some examples, the selectively permeable membranes can have a carbon dioxide permeance of from 500 to 3000 GPU at 57oC and 1 atm feed pressure and a carbon dioxide:nitrogen selectivity of from 10 to 1000 at 57oC and 1 atm feed pressure. High pressure ratios across the membranes can be achieved by compressing the feed gas to a high pressure, by using vacuum pumps to create a lowered pressure on the permeate side of the membrane, by using a sweep stream, or a combination thereof.

Description

[0001] ATTORNEY DOCKET NO. 103362-093WO1

[0002] OSU Tech ID T2025-160 METHODS FOR THE SEPARATION OF CO2FROM A GAS STREAM

[0003] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims benefit of priority of U.S. Provisional Application No.

[0004] 63 / 749,589, filed January 25, 2025, which is incorporated herein by reference in its entirety.

[0005] FIELD OF THE DISCLOSURE

[0006] This disclosure relates generally to methods for the separation of carbon dioxide from a gas stream.

[0007] BACKGROUND OF THE DISCLOSURE

[0008] In recent years it has become obvious that the generation of greenhouse gases leads to global warming and that further increase in greenhouse gas production will accelerate global warming. Since CO2 (carbon dioxide) is identified as a main greenhouse gas, CCS (carbon capture and storage) is considered as one of the potential major means to reduce the release of greenhouse gases into the atmosphere and to control global warming. To implement these strategies, improved methods and methods for separating CO2 from flue gas are needed.

[0009] SUMMARY OF THE DISCLOSURE

[0010] Provided herein are multistage (in particular three (3)-stage) membrane separation methods for capturing carbon dioxide (CO2) from feed gas stream. The feed gas stream can be from a variety of sources, provided that includes CO2 in combination with one or more additional gases. For example, the feed gas stream can include CO2 in combination with additional gases such as H2, N2, O2, CH4, CO, H2O, SO2, NO, NO2, and combinations thereof. In some cases, the feed gas stream can be a combustion gas, such as a gas stream that includes the combustion products of a hydrocarbon fuel (e.g., the combustion products from coal combustion or the combustion products from natural gas combustion). In certain embodiments, the feed gas can be emissions from a power plant (e.g., a natural gas-fired power plant or a coal-fired power plant). The feed gas can also be a natural gas stream. For example, the methods described herein can be used to remove CO2 from a natural gas stream (e.g., to upgrade CO2). The feed gas can also be, for example, emissions from a cement plant.ATTORNEY DOCKET NO. 103362-093WO1

[0011] OSU Tech ID T2025-160 The carbon dioxide content of the feed gas stream may vary. In some instances, the feed gas stream can include at least 2 vol% carbon dioxide (e.g., from 2 vol% to 80 vol% CO2, from 2 vol% to 40 vol% CO2, from 2 vol% to 25 vol%, from 2 vol% to 20 vol% CO2, from 2 vol% to 10 vol% CO2, from 5 vol% to 80 vol% CO2, from 5 vol% to 40 vol% CO2, from 5 vol% to 25 vol% CO2, from 5 vol% to 20 vol% CO2, from 5 vol% to 10 vol% CO2, or from 10 vol% to 20 vol% CO2). In certain embodiments, the feed gas stream can include from 20 vol% to 25 vol% CO2 or from 3 vol% to 5 vol% CO2).

[0012] The membrane separation methods can employ a first selectively permeable membrane, a second selectively permeable membrane, and a third selectively permeable membrane. The first selectively permeable membrane and the second selectively permeable membrane can be arranged in series (e.g., in an enriching cascade configuration). The first selectively permeable membrane and second selectively membrane can be the same or different. The residual flue gas (i.e., the first retentate stream) can be subjected to further decarbonization using a third selectively permeable membrane.

[0013] The selectively permeable membranes can have a carbon dioxide permeance of at least 500 gas permeance units (GPU), such as from 500 to 3000 GPU at 57°C and 1 atm feed pressure. In some examples, the selectively permeable membranes can have a high carbon dioxide permeance and a moderate carbon di oxi de: nitrogen selectivity. For example, the selectively permeable membranes can have a carbon dioxide permeance of from 1000 to 3000 GPU at 57°C and 1 atm feed pressure (e.g., a carbon dioxide permeance of from 1500 to 2500 GPU at 57°C and 1 atm feed pressure) and a carbon di oxi de: nitrogen selectivity of from 10 to 60 at 57°C and 1 atm feed pressure. In one embodiment, the selectively permeable membranes can have a carbon dioxide permeance of about 2000 GPU at 57°C and 1 atm feed pressure and a carbon di oxi de: nitrogen selectivity of about 20 at 57°C and 1 atm feed pressure. In these cases, the selectively permeable membranes can comprise a polymer layer that includes an amine-containing polymer, a polyalkylene oxide, a polyalkyl siloxane, a copolymer thereof, or a blend thereof. For example, the polymer layer can comprise polyvinylamine, polyethylene oxide, polydimethylsiloxane, or a combination thereof

[0014] The selectively permeable membranes can have a carbon di oxi de: nitrogen selectivity of at least 10 at 57°C and 1 atm feed pressure, such as from 10 to 1000 at 57°C and 1 atm feed pressure. In some examples, the selectively permeable membranes can have a high carbon di oxi de: nitrogen selectivity and a moderate or high carbon dioxide permeance. ForATTORNEY DOCKET NO. 103362-093WO1

[0015] OSU Tech ID T2025-160 example, the selectively permeable membrane can have a carbon di oxi de: nitrogen selectivity of from 50 to 1000 at 57°C and 1 atm feed pressure (e.g., a carbon

[0016] di oxi de: nitrogen selectivity of from 100 to 500 at 57°C and 1 atm feed pressure) and a carbon dioxide permeance of from 500 to 2500 GPU at 57°C (e.g., a carbon dioxide permeance of from 1500 to 2500 GPU at 57°C and 1 atm feed pressure). In one embodiment, the selectively permeable membranes can have a carbon dioxide permeance of about 1100 GPU at 57°C and 1 atm feed pressure and a carbon di oxi de: nitrogen selectivity of about 140 at 57°C and 1 atm feed pressure. In one embodiment, the selectively permeable membranes can have a carbon dioxide permeance of about 1100 GPU at 57°C and 1 atm feed pressure and a carbon di oxi de: nitrogen selectivity of about 140 at 57°C and 1 atm feed pressure. In these cases, the selectively permeable membranes can comprise a selective polymer layer comprising an amine-containing polymer chosen from polyvinylamine, polyallylamine, polyethyleneimine, poly-7V-isopropylallylamine, poly-7V-tert-butylallylamine, poly-7V-l,2-dimethylpropylallylamine, poly-7V-methylallylamine, poly-7V,7V-dimethylallylamine, poly-2 -vinylpiperidine, poly-4-vinylpiperidine, polyaminostyrene, chitosan, copolymers, and blends thereof. For example, the amine-containing polymer can comprise polyvinylamine. In certain cases, a mobile carrier, such as an aminoacid salt, can be dispersed within the amine-containing polymer.

[0017] Optionally, a driving force for transmembrane permeation can be supplied by lowering the partial pressure of the carbon dioxide permeant on the permeate side of the membrane, to a level below its partial pressure on the feed side. High pressure ratios across the membranes can be achieved by compressing the gas to a high pressure on the retentate side, by using vacuum pumps to create a lowered pressure on the permeate side, or a combination of both. In some embodiments, the feed gas stream can be compressed prior to passing the feed stream through any one of the selectively permeable membrane. For example, the initial (raw) feed gas stream and / or the first permeate stream can be compressed to a pressure of 1.5 atm or greater, such as from 1.5 to 2.5 atm or from 1.5 to 4 atm, prior to passing the feed stream through the selectively permeable membrane.

[0018] When a vacuum is used, the vacuum can be pulled at the permeate side of the selectively permeable membrane. In some cases, the vacuum is pulled at the permeate side of the selectively permeable membrane having a relatively high CC>2:N2 selectivity. The relatively high CC>2:N2 selectivity of the membranes employed in the methods described herein can allow one to apply a large pressure ratio to obtain a high CO2 removal as well asATTORNEY DOCKET NO. 103362-093WO1

[0019] OSU Tech ID T2025-160 a high CO2 purity in only one step (i.e., using a single membrane). In some embodiments, a vacuum can be applied to generate a pressure of from 0.1 to 0.9 atm (e.g., from 0.1 to 0.5 atm) on the permeate side of the selectively permeable membrane having a relatively high CC>2:N2 selectivity. In some embodiments, the feed pressure to permeate pressure ratio can be at least 5 (e.g., from 5 to 40, from 5 to 20, or from 5 to 10). In certain embodiments, the feed pressure to permeate pressure ratio can be at least 7 (e.g., from 7 to 40, from 7 to 20, or from 7 to 10).

[0020] Optionally, a sweep gas can be used to provide a low carbon dioxide partial pressure on the permeate side of selectively permeable membrane, thereby providing or augmenting the driving force for transmembrane permeation. When a sweep gas is used, the sweep gas can include air, oxygen-enriched air, oxygen, nitrogen, nitrogen-enriched air, steam, or combinations thereof. In other embodiments, the sweep gas can include a portion of the retentate gas stream obtained from one or more of the other selectively permeable membranes used during separation.

[0021] The carbon dioxide content of the carbon dioxide-depleted product gas stream (the first, second, and / or third retentate stream) may vary depending upon method requirements. In some embodiment, the carbon dioxide-depleted product gas stream can include 5 vol% or less carbon dioxide. For example, the carbon dioxide-depleted product gas stream can include 2 vol% or less carbon dioxide, 1.5 vol% or less carbon dioxide, 1 vol% or less carbon dioxide, 0.75 vol% or less carbon dioxide, or 0.5 vol% or less carbon dioxide.

[0022] In some embodiments, provided herein are processes for separating carbon dioxide from a feed gas stream. These methods can comprise passing the feed gas stream through a first selectively permeable membrane having a retentate side and an opposing permeate side to separate the feed gas stream into a first retentate stream and a first permeate stream; passing the first permeate stream through a second selectively permeable membrane having a retentate side and an opposing permeate side to separate the first permeate stream into a second retentate stream and a second permeate stream; passing the first retentate stream through a third selectively permeable membrane having a retentate side and an opposing permeate side to separate the first retentate stream into a third retentate stream and a third permeate stream; combining the third permeate stream with the first permeate stream prior to passing the first permeate stream through a second selectively permeable membrane; combining the second retentate stream with the feed gas stream prior to passing the feed gas stream through a first selectively permeable membrane; withdrawing the second permeateATTORNEY DOCKET NO. 103362-093WO1

[0023] OSU Tech ID T2025-160 stream, wherein the second permeate stream has a greater concentration of carbon dioxide than the feed gas stream; and withdrawing the third retentate stream, wherein the third retentate stream has a lower concentration of carbon dioxide than the feed gas stream.

[0024] In some embodiments, the feed gas stream comprises from 2% to 50%, by volume (e.g., from 5% to 25%, by volume) carbon dioxide. In some embodiments, the second permeate stream comprises at least 80%, by volume, carbon dioxide, such as at least 90%, by volume, carbon dioxide or at least 95%, by volume, carbon dioxide. In some embodiments, the third retentate stream comprises less than 1.5%, by volume, carbon dioxide, such as less than 1%, by volume, carbon dioxide or less than 0.5%, by volume, carbon dioxide.

[0025] In some embodiments, the second permeate stream is compressed and / or used in a downstream process utilizing carbon dioxide as an input.

[0026] In some embodiments, the third retentate stream is discharged into the atmosphere as an exhaust gas.

[0027] In some embodiments, the process achieves a carbon dioxide capture, measured as a percentage of carbon dioxide present in the feed gas that is collected in the second permeate stream, of greater than 90%, such as 95% or greater, 98% or greater, or 99% or greater.

[0028] In some embodiments, the process further comprises passing the feed gas stream through a SO2 and NO2 polishing unit prior to passing the feed gas stream through the first selectively permeable membrane. In some embodiments, the feed gas stream is contacted with caustic in the SO2 and NO2 polishing unit that reacts with and reduces the concentration of SO2 in the feed gas.

[0029] In some embodiments, the feed gas stream is cooled to a temperature of from 25°C to 100°C, such as a temperature of from 40°C to 100°C, from 50°C to 100°C, from 60°C to 100°C, from 60°C to 90°C, or from 70°C to 80°C prior to passing the feed gas stream through the first selectively permeable membrane. In certain embodiments, the feed gas stream is cooled via direct contact cooling.

[0030] In some embodiments, the feed gas stream is compressed to a pressure of at least 1.5 atm prior to passing the feed gas stream through the first selectively permeable membrane. In certain embodiments, the feed gas stream is compressed to a pressure of from 2 to 5 atm prior to passing the feed gas stream through the first selectively permeable membrane.ATTORNEY DOCKET NO. 103362-093WO1

[0031] OSU Tech ID T2025-160 In some embodiments, the process further comprises passing a sweep gas comprising a portion of the first retentate stream across the permeate side of the first selectively permeable membrane.

[0032] In some embodiments, the first permeate stream is compressed prior to passing the first permeate stream through the second selectively permeable membrane. In certain embodiments, the first permeate stream is compressed to a pressure of at least 1.5 atm prior to passing the first permeate stream through the second selectively permeable membrane. In certain embodiments, the first permeate stream is compressed to a pressure of from 2.5 to 5 atm prior to passing the first permeate stream through the second selectively permeable membrane.

[0033] In some embodiments, the process further comprises applying a vacuum to the permeate side of the second selectively permeable membrane. In certain embodiments, the vacuum is applied to generate a pressure of from 0.1 to 0.9 atm on the permeate side of the second selectively permeable membrane.

[0034] In some embodiments, the first retentate stream is compressed prior to passing the first retentate stream through the third selectively permeable membrane. In certain embodiments, the first retentate stream is compressed to a pressure of at least 1.5 atm prior to passing the first retentate stream through the third selectively permeable membrane. In certain embodiments, the first retentate stream is compressed to a pressure of from 2.5 to 5 atm prior to passing the first retentate stream through the third selectively permeable membrane.

[0035] In some embodiments, the process further comprises applying a vacuum to the permeate side of the third selectively permeable membrane. In some embodiments, the vacuum is applied to generate a pressure of from 0.1 to 0.5 atm on the permeate side of the third selectively permeable membrane.

[0036] In some embodiments, the process further comprises compressing the second permeate stream, such as compressing the second permeate stream to a pressure of at least 50 atm, at least 100 atm, or at least 150 atm. In some embodiments, the compressing the second permeate stream comprises a multistage compression and dehydration process.

[0037] In some of these embodiments, the first selectively permeable membrane, the second selectively permeable membrane, and the third selectively permeable membrane can each exhibit a carbon dioxide permeance of at least 500 GPU at 57°C and 1 atm feed pressure (e.g., from 500 to 3000 GPU at 57°C and 1 atm feed pressure, or from 1000 to 1500 GPU atATTORNEY DOCKET NO. 103362-093WO1

[0038] OSU Tech ID T2025-160 57°C and 1 atm feed pressure) and a carbon di oxi de: nitrogen selectivity of from 10 to 1000 at 57°C and 1 atm feed pressure (e.g., from 50 to 1000 at 57°C and 1 atm feed pressure, or from 100 to 500 at 57°C and 1 atm feed pressure).

[0039] In some embodiments, the first selectively permeable membrane can exhibit a carbon dioxide permeance of at least 1000 GPU at 57°C and 1 atm feed pressure (e.g., from 1000 to 3000 GPU at 57°C and 1 atm feed pressure, or from 1500 to 2500 GPU at 57°C and 1 atm feed pressure) and a carbon di oxi de: nitrogen selectivity of at least 10 at 57°C and 1 atm feed pressure (e.g., from 10 to 60 at 57°C and 1 atm feed pressure, or from 15 to 40 at 57°C and 1 atm feed pressure). In some embodiments, the second selectively permeable membrane can exhibit a carbon dioxide permeance of at least 500 GPU at 57°C and 1 atm feed pressure (e.g., from 500 to 3000 GPU at 57°C and 1 atm feed pressure, or from 1000 to 1500 GPU at 57°C and 1 atm feed pressure) and a carbon di oxi de: nitrogen selectivity of from 10 to 1000 at 57°C and 1 atm feed pressure (e.g., from 50 to 1000 at 57°C and 1 atm feed pressure, or from 100 to 500 at 57°C and 1 atm feed pressure). In some embodiments, the second third permeable membrane can exhibit a carbon dioxide permeance of at least 500 GPU at 57°C and 1 atm feed pressure (e.g., from 500 to 3000 GPU at 57°C and 1 atm feed pressure, or from 1000 to 1500 GPU at 57°C and 1 atm feed pressure) and a carbon di oxi de: nitrogen selectivity of from 10 to 1000 at 57°C and 1 atm feed pressure (e.g., from 50 to 1000 at 57°C and 1 atm feed pressure, or from 100 to 500 at 57°C and 1 atm feed pressure).

[0040] DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 is a flow diagram of an exemplary 3-stage membrane process for achieving -99% CO2 capture.

[0042] Figure l is a flow diagram of an exemplary SO2 and NO2 polishing unit.

[0043] Figure 3 is a flow diagram illustrating an example heat integration approach in a gas compression and energy recovery system.

[0044] Figure 4 is a flow diagram illustrating an example CO2 compression / dehydration process.

[0045] Figure 5 is a flow diagram illustrating and example TEG dehydration system for CO2 drying.

[0046] Figure 6 is a flow diagram of an exemplary 3-stage membrane process for achieving -95% CO2 capture.ATTORNEY DOCKET NO. 103362-093WO1

[0047] OSU Tech ID T2025-160

[0048] DETAILED DESCRIPTION

[0049] Provided herein are membrane separation methods for separating carbon dioxide from a feed gas stream. The feed gas stream can contain carbon dioxide and other constituents such as water, nitrogen, oxygen, hydrogen, a natural gas, and hydrogen sulfide. Such a feed gas stream may come from any of a number of sources. In some instances, the feed gas stream for separation may be derived from a fossil fuel that requires hydrogen purification for fuel cell, electricity generation, and hydrogenation applications, a biogas for renewable energy, or a natural gas for commercial uses. The gas stream may also be derived from a flue gas for removal of carbon dioxide from the flue gas. In some examples, the feed gas stream can be derived from a cement plant, a natural gas plant, or a coal plant.

[0050] Depending on the source, the carbon dioxide content of the feed gas stream may vary. In some embodiments, the feed gas stream can include 2 vol% or greater carbon dioxide. For example, the feed gas stream can include 5 vol% or greater carbon dioxide, 15 vol% or greater carbon dioxide, 10 vol% or greater carbon dioxide, 15 vol% or greater carbon dioxide, 20 vol% or greater carbon dioxide, 25 vol% or greater carbon dioxide, 30 vol% or greater carbon dioxide, 35 vol% or greater carbon dioxide, 40 vol% or greater carbon dioxide, 45 vol% or greater carbon dioxide, 50 vol% or greater carbon dioxide, 55 vol% or greater carbon dioxide, 60 vol% or greater carbon dioxide, 65 vol% or greater carbon dioxide, 70 vol% or greater carbon dioxide, 75 vol% or greater carbon dioxide, 80 vol% or greater carbon dioxide, 85 vol% or greater carbon dioxide, or 90 vol% or greater carbon dioxide. In some instances, the feed gas stream can include from 2 vol% to 80 vol% CO2 (e.g., from 2 vol% to 80 vol% CO2, from 2 vol% to 40 vol% CO2, from 2 vol% to 25 vol%, from 2 vol% to 20 vol% CO2, from 2 vol% to 10 vol% CO2, from 5 vol% to 80 vol% CO2, from 5 vol% to 40 vol% CO2, from 5 vol% to 25 vol% CO2, from 5 vol% to 20 vol% CO2, from 5 vol% to 10 vol% CO2, or from 10 vol% to 20 vol% CO2). In certain embodiments, the feed gas stream can include from 20 vol% to 25 vol% CO2 or from 3 vol% to 5 vol% CO2).

[0051] The gas feed streams described herein may be available at atmospheric pressure, such as a flue gas stream. Therefore, the methods described herein are sufficiently flexible to be used with gas feed streams having optimum pressure, low pressure, or high pressure. In some embodiments, compression of the feed gas stream, such as from atmospheric pressure to a pressure of 1.5 atm or greater, 2 atm or greater, 2.5 atm or greater, 3 atm orATTORNEY DOCKET NO. 103362-093WO1

[0052] OSU Tech ID T2025-160 greater, 3.5 atm or greater, 4 atm or greater, 4.5 atm or greater, or 5 atm or greater can provide part of the carbon dioxide separation method that is relatively energy efficient. In certain embodiments, the feed gas stream can be compressed to a pressure of from 1.5 to 2.5 atm, from 1.5 to 3 atm, from 1.5 to 4 atm, from 1.5 to 5 atm, or from 3 to 5 atm.

[0053] The feed gas stream along with air, oxygen enriched air or oxygen can be introduced into a combustor prior carrying out the membrane separation methods described herein. The combustion off-gas stream can then be processed as described herein.

[0054] Membranes

[0055] The membrane separation methods described herein can employ at least three membranes. In one embodiment, the at least three membranes comprise a first stage membrane, a second stage membrane, and a third stage membrane. Each membrane can independently introduce a specific characteristic to the separation method. Thus, by providing three membranes, one can change the characteristics or properties (such as purity) of the separated gases in a way not seen by simply using a single membrane. The at least three membranes used in the methods described herein can be the same. In some embodiments, the at least three membranes can be different. When the membranes are different, the membranes can be arranged in any order, or for example as described herein.

[0056] In some embodiments, the at least three membranes can include a first selectively permeable membrane, a second selectively permeable membrane, and a third selectively permeable. Selectively permeable membranes are disclosed in PCT / US2015 / 041282 and U.S. Patent No. 8,277,932, both of which are hereby incorporated herein by reference. The selectively permeable membrane can have a CCUN? selectivity of at least 10 at 57°C and 1 atm feed pressure. For example, the selectively permeable membrane can have a CC>2:N2 selectivity of at least 25 at 57°C and 1 atm feed pressure (e.g., at least 50, at least 75, at least 100, at least 150, at least 200, at least 250, at least 300, at least 350, at least 400, at least 500, at least 600, at least 700, at least 800, at least 900, or at least 1000) at 57°C and 1 atm feed pressure. In some embodiments, the selectively permeable membrane can have a CC>2:N2 selectivity of 1000 or less at 57°C and 1 atm feed pressure (e.g., 900 or less, 800 or less, 700 or less, 500 or less, 400 or less, 300 or less, 200 or less, 100 or less, 80 or less, 60 or less, or 50 or less) at 57°C and 1 atm feed pressure.

[0057] The selectively permeable membrane can have a CC>2:N2 selectivity ranging from any of the minimum values described above to any of the maximum values described above. For example, the selectively permeable membrane can have a CC>2:N2 selectivity of fromATTORNEY DOCKET NO. 103362-093WO1

[0058] OSU Tech ID T2025-160 10 to 1000 (e.g., from 10 to 500, from 10 to 100, from 10 to 60, from 50 to 1000, from 50 to 500, from 100 to 1000, or from 100 to 500) at 57°C and 1 atm feed pressure. The CC>2:N2 selectivity of the selectively permeable membrane is defined as the ratio of CO2 permeance to N2 permeances. The CO2 permeance and N2 permeance of the selectively permeable membrane can be measured using standard methods for measuring gas permeance known in the art, such as those described in ASTM D1434-82 (2015), which is incorporated herein by reference.

[0059] The selectively permeable membrane can have a CO2 permeance of at least 500 GPU at 57°C and 1 atm feed pressure. For example, the selectively permeable membrane can have a CO2 permeance of 750 GPU or greater (e.g., 1000 GPU or greater, 1500 GPU or greater, 2000 GPU or greater, 2500 GPU or greater, or 3000 GPU or greater) at 57°C and 1 atm feed pressure. In some embodiments, the selectively permeable membrane can have a CO2 permeance of 3000 GPU or less (e.g., 2500 GPU or less, 2000 GPU or less, or 1500 GPU or less) at 57°C and 1 atm feed pressure.

[0060] The selectively permeable membrane can have a CO2 permeance ranging from any of the minimum values described above to any of the maximum values described above. For example, the selectively permeable membrane can have a CO2 permeance of from 500 to 3000 GPU (e.g., from 500 to 2500 GPU, from 1000 to 3000 GPU, from 1000 to 2500 GPU, from 1500 to 3000 GPU, from 1500 to 2500 GPU, or from 2000 to 3000 GPU) at 57°C and 1 atm feed pressure. The CO2 permeance of the selectively permeable membrane can be measured using standard methods for measuring gas permeance known in the art, such as those described in ASTM D1434-82 (2015) which is incorporated herein by reference.

[0061] In some embodiments, the selectively permeable membrane can have a relatively high CC>2:N2 selectivity and a relatively moderate CO2 permeance. For example, the selectively permeable membrane can have a CC>2:N2 selectivity of from 50 or greater and a CO2 permeance of 500 GPU or greater at 57°C and 1 atm feed pressure (e.g., a CC>2:N2 selectivity of from 50 to 1000 at 57°C and 1 atm feed pressure and a CO2 permeance of from 500 to 2500 GPU at 57°C and 1 atm feed pressure).

[0062] In some embodiments, the selectively permeable membrane can have a relatively high CO2 permeance and a relatively low CC>2:N2 selectivity. For example, the selectively permeable membrane can have a CO2 permeance of from 1000 GPU or greater and a CC>2:N2 selectivity of 10 or greater at 57°C and 1 atm feed pressure (e.g., a CO2 permeanceATTORNEY DOCKET NO. 103362-093WO1

[0063] OSU Tech ID T2025-160 of from 1000 to 3000 GPU at 57°C and a CCUN? selectivity of from 10 to 60 at 57°C and 1 atm feed pressure).

[0064] The components in the selectively permeable membrane can vary depending on the permeability and selectivity required for a particular application. In some embodiments, the selectively permeable membrane can include one or more layers (e.g., one or more polymer layers). In some embodiments, the membranes can be derived from an amine-based polymer, a polyethyleneoxide (PEO)-based polymer, a polydimethylsiloxane (PDMS)-based polymer, or a combination thereof. In some instances, the membrane can include a selective polymer (a selective polymer layer) through which gas permeates via diffusion or facilitated diffusion.

[0065] Examples of suitable membranes are described, for example, in International Application No. PCT / US2015 / 041282, U.S. Patent No. 9,216,390, and U. S. Patent No. 8,277,932, each of which are hereby incorporated herein by reference in their entirety. In certain embodiments, the membranes can comprise a gas permeable support layer, an inorganic layer disposed on the gas permeable support layer, and a selective polymer layer disposed on the inorganic layer. In these embodiments, the gas permeable support layer, the inorganic layer, and the selective polymer layer can optionally comprise one or more sublayers.

[0066] The gas permeable support layer can be formed from any suitable material. The material used to form the gas permeable support layer can be chosen based on the end use application of the membrane. In some embodiments, the gas permeable support layer can comprise a gas permeable polymer. The gas permeable polymer can be a cross-linked polymer, a phase separated polymer, a porous condensed polymer, or a blend thereof.

[0067] Examples of suitable gas permeable polymers include polyamides, polyimides, polypyrrol ones, polyesters, sulfone-based polymers, polymeric organosili cones, fluorinated polymers, polyolefins, copolymers thereof, or blends thereof. Specific examples of polymers in the gas permeable support layer can include polydimethylsiloxane, polydiethylsiloxane, polydi-iso-propylsiloxane, polydiphenylsiloxane, polyethersulfone, polyphenyl sulfone, polysulfone, partially fluorinated or perfluorinated derivatives thereof, copolymers thereof, or blends thereof In some embodiments, the gas permeable polymer can be polyethersulfone. If desired, the gas permeable support layer can include inorganic particles to increase the mechanical strength without altering the permeability of the support layer.ATTORNEY DOCKET NO. 103362-093WO1

[0068] OSU Tech ID T2025-160 In certain embodiments, the gas permeable support layer can comprise a gas permeable polymer disposed on a base. The base can be in any configuration configured to facilitate formation of a membrane suitable for use in a particular application. For example, the base can be a flat disk, a tube, a spiral wound, or a hollow fiber base. The base can be formed from any suitable material. In some embodiments, the layer can include a fibrous material. The fibrous material in the base can be a mesh (e.g., a metal or polymer mesh), a woven or non-woven fabric, a glass, fiberglass, a resin, a screen (e.g., a metal or polymer screen). In certain embodiments, the base can include a non-woven fabric (e.g., a nonwoven fabric comprising fibers formed from a polyester.

[0069] The inorganic layer can be formed from a variety of suitable materials. In certain embodiments, the inorganic layer can be formed from a plurality of discreet nanoparticles having an average particle size of less than 1 micron. The inorganic layer can comprise multiple pores and / or channels formed between the nanoparticles and / or within the nanoparticles. The pores and / or channels formed can be in fluid contact with the gas permeable support layer. The nanoparticles can be selected to have a surface chemistry that is compatible with the selective polymer layer, the gas permeable support layer, or a combination thereof. For example, in certain cases, the nanoparticle can comprise hydrophilic nanoparticles. Examples of suitable nanoparticles include alkaline earth metal oxide nanoparticles, transition metal oxide nanoparticles, lanthanide metal oxide nanoparticles, group IVA metal oxide nanoparticles, transition metal nanoparticles, transition-metal catalyst nanoparticles, nanoparticles comprising a transition metal adsorbed on a non-reactive support, metal alloy nanoparticles, silicate nanoparticles, alumino-silicate nanoparticles, nanoparticles comprising clays, and combinations thereof. Specific examples of nanoparticles include alumina nanoparticles, silica nanoparticles, zeolite nanoparticles, titania nanoparticles, zirconia nanoparticles, palladium nanoparticles, platinum nanoparticles, nickel nanoparticles, transition-metal catalyst nanoparticles, and combinations thereof. In certain embodiments, the nanoparticles in the inorganic layer can be chosen from silicate nanoparticles, alumino-silicate nanoparticles, or combinations thereof. In certain embodiments, the nanoparticles can comprise zeolite nanoparticles. The zeolite nanoparticles can comprise zeolites having varying frameworks and differing Si / Al rations. For example, the nanoparticles can be zeolite Y nanoparticles.

[0070] The membranes can further include a selective polymer layer disposed on the inorganic layer. In some cases, the selective polymer layer can be a selective polymerATTORNEY DOCKET NO. 103362-093WO1

[0071] OSU Tech ID T2025-160 through which gas permeates via diffusion or facilitated diffusion. The selective polymer layer can include a hydrophilic polymer, an amino compound, or a combination thereof. In some embodiments, the hydrophilic polymer can be absent. In other embodiments, the polymer can comprise a combination of a hydrophilic polymer and an amino compound. For example, the polymer can comprise an amino compound (e.g., a small molecule or a polymer) dispersed in a hydrophilic polymer matrix.

[0072] The amino compound (e.g., a small molecule or a polymer) in the polymer can have one or more primary amine moieties and / or one or more secondary amine moieties. The amino compound can be, for example, an amine-containing polymer, a low molecular weight amino compound (i.e., a small molecule), or a combination thereof.

[0073] In some embodiments, the amino compound comprises an amine-containing polymer (also referred to herein as a “fixed carrier”). The amine-containing polymer can have any suitable molecular weight. For example, the amine-containing polymer can have a weight average molecular weight of from 5,000 Da to 2,000,000 Da, 50,000 Da to 2,000,000 Da, or from 50,000 Da to 200,000 Da. Suitable examples of amine-containing polymers include, but are not limited to, polyvinylamine, polyallylamine, polyethyleneimine, poly-7V-isopropylallylamine, poly-7V-tert-butylallylamine, poly-7V-l,2-dimethylpropylallylamine, poly-7V-methylallylamine, poly-7V,7V-dimethylallylamine, poly-2 -vinylpiperidine, poly-4-vinylpiperidine, polyaminostyrene, chitosan, copolymers, and blends thereof. In some embodiments, the amine-containing polymer can comprise polyvinylamine (e.g., polyvinylamine having a weight average molecular weight of from 50,000 Da to 2,000,000 Da, from 50,000 Da to 200,000 Da, or from 50,000 Da to 100,000 Da). In some embodiments when the amino compound comprises an amine-containing polymer, the hydrophilic polymer is absent. In some embodiments when the amino compound comprises an amine-containing polymer, the polymer can comprise a blend of an amine-containing polymer and a hydrophilic polymer (e.g., an amine-containing polymer dispersed in a hydrophilic polymer matrix).

[0074] In some embodiments, the amino compound can comprise a low molecular weight amino compound (also referred to herein as a “mobile carrier”). Without wishing to be bound by theory, for the facilitated transport mechanism, the CO2 transport of the fixed carrier may be limited by the mobility of the CCh-carrier complex. Therefore, the incorporation of mobile carriers can enhance the CO2 transport. With the incorporation of mobile carriers in the polymer, a higher mobile carrier amount can result in higher CO2ATTORNEY DOCKET NO. 103362-093WO1

[0075] OSU Tech ID T2025-160 permeance. However, in some embodiments, if the mobile carrier amount is too much, the polymer showed an unstable result. The reason was that the polymer matrix was not strong enough to hold too much amount of mobile carriers. In another words, there might be carrier leakage into the pores of the substrate, which caused the instability of the polymer performance. In some embodiments, the polymer can include up to 65 wt% of the mobile earner.

[0076] The low molecular weight amino compound can have a molecular weight of 1,000 Da or less (e.g., 800 Da or less, 500 or less, 300 Da or less, or 250 Da or less). In some embodiments, the low molecular weight amino compound can be non-volatile at the temperatures at which the polymer will be stored or used. For example, the low molecular weight amino compound can comprise a salt of a primary amine or a salt of a secondary amine. In some embodiments when the amino compound comprises a low molecular weight amino compound, the polymer can comprise a blend of the low molecular weight amino compound and a hydrophilic polymer (e.g., a low molecular weight amino compound dispersed in a hydrophilic polymer matrix).

[0077] In some cases, the low molecular weight amino compound can include an aminoacid salt having the formula:

[0078] > "

[0079]

[0080] wherein Ri, R2, R3, and R4 are hydrogen or hydrocarbon groups having from 1 to 4 carbon atoms, n is an integer ranging from 0 to 4, Am+is a cation having a valence of 1 to 3. In some cases, the cation (Am+) can be an amine cation having the formula:

[0081]

[0082] wherein R5 and Re are hydrogen or hydrocarbon groups having from 1 to 4 carbon atoms, R?is hydrogen or hydrocarbon groups having from 1 to 4 carbon atoms or an alkyl amine of from 2 to 6 carbon atoms and 1 to 4 nitrogen atoms, y is an integer ranging from 1 to 4, and m is an integer equal to the valence of the cation. In some embodiments, Am+is a metal cation selected from Groups la, Ila, and Illa of the Periodic Table of Elements or a transition metal. For example, Am+can comprise lithium, aluminum, or iron.ATTORNEY DOCKET NO. 103362-093WO1

[0083] OSU Tech ID T2025-160 Other suitable low molecular weight amino compounds include aminoisobutyric acid-potassium salt, aminoisobutyric acid-lithium salt, aminoisobutyric acid-piperazine salt, glycine-potassium salt, glycine-lithium salt, glycine-piperazine salt, dimethylglycinepotassium salt, dimethylglycine-lihium salt, dimethylglycine-piperazine salt, piperadine-2-carboxlic acid- potassium salt, piperadine-2-carboxlic acid-lithium salt, piperadine-2-carboxlic acid-piperazine salt, piperadine-4-carboxlic acid- potassium salt, piperadine-4-carboxlic acid-lithium salt, piperadine-4-carboxlic acid-piperazine salt, piperadine-3-carboxlic acid- potassium salt, piperadine-3-carboxlic acid-lithium salt, piperadine-3-carboxlic acid-piperazine salt, and blends thereof.

[0084] The polymer can comprise any suitable amount of the amino compound. For example, in some embodiments, the hydrophilic polymer can be absent. In these embodiments, the polymer can comprise from 100% to 80% by weight amino compound, based on the total weight of the polymer. In some cases, the polymer can comprise from 10% to 90% by weight (e.g., from 10% to 50% by weight) amino compound, based on the total weight of the components used to form the polymer.

[0085] Optionally, the polymer can include any suitable hydrophilic polymer. Examples of hydrophilic polymers suitable for use in the polymer layer can include polyvinylalcohol, polyvinylacetate, a polyalkylene oxide such as polyethylene oxide, polyvinylpyrrolidone, a polyalkyl siloxane such as polydimethylsiloxane, polyacrylamine, a polyamine such as polyallylamine, polyvinyl amine, or polyethylenimine, copolymers thereof, and blends thereof. In some embodiments, the hydrophilic polymer includes polyvinylalcohol.

[0086] When present, the hydrophilic polymer can have any suitable molecular weight. For example, the hydrophilic polymer can have a weight average molecular weight of from 15,000 Da to 2,000,000 Da (e.g., from 50,000 Da to 200,000 Da). In some embodiments, the hydrophilic polymer can include polyvinylalcohol having a weight average molecular weight of from 50,000 Da to 150,000 Da.

[0087] The polymer can comprise any suitable amount of the hydrophilic polymer. For example, in some cases, the polymer layer can comprise from 10% to 90% by weight (e.g., from 10% to 50% by weight) hydrophilic polymer, based on the total weight of the components used to form the polymer layer.

[0088] In some embodiments, the polymer can also include a cross-linking agent. Crosslinking agents suitable for use in the polymer can include, but are not limited to, formaldehyde, glutaraldehyde, maleic anhydride, glyoxal, di vinyl sulfone,ATTORNEY DOCKET NO. 103362-093WO1

[0089] OSU Tech ID T2025-160 toluenediisocyanate, trimethylol melamine, terephthalatealdehyde, epichlorohydrin, vinyl acrylate, and combinations thereof. In some embodiments, the cross-linking agent can comprise formaldehyde, glutaraldehyde, or maleic anhydride. The polymer can comprise any suitable amount of the cross-linking agent. For example, the polymer can comprise 1 to 40 percent cross-linking agents by weight of the polymer.

[0090] The polymer layer can further include a base. The base can act as a catalyst to catalyze the cross-linking of the polymer layer (e.g., cross-linking of a hydrophilic polymer with an amine-containing polymer). In some embodiments, the base can remain in the polymer and constitute a part of the polymer. Examples of suitable bases include potassium hydroxide, sodium hydroxide, lithium hydroxide, triethylamine, N,N-dimethylaminopyridine, hexamethyltriethylenetetraamine, potassium carbonate, sodium carbonate, lithium carbonate, and combinations thereof. In some embodiments, the base can include potassium hydroxide. The polymer can comprise any suitable amount of the base. For example, the polymer can comprise 1 to 40 percent base by weight of the polymer If desired, the polymer layer can be surface modified by, for example, chemical grafting, blending, or coating to improve the performance of the polymer layer. For example, hydrophobic components may be added to the polymer layer to alter the properties of the polymer layer in a manner that facilitates greater fluid selectivity.

[0091] As an example, the membrane can include a high molecular weight polyvinylamine (PVAm) that can act as a fixed carrier, while different kinds of aminoacid salts can be incorporated as mobile carriers in the coating solution for membrane synthesis. The viscous polyvinylamine / mobile carrier coating solution can be knife-coated onto the different substrates to form a thin layer of the membranes synthesized. As the fixed-carrier in the membrane, PVAm not only provides amino groups for CCh lSh separation, but also provides the mechanical strength and film-forming ability of the membrane. Therefore, a higher molecular weight of PVAm may be beneficial. Without wishing to be bound by theory, a higher molecular weight may be suitable since the polymer matrix will be stronger, which makes the membrane more stable. Further, due to the stronger polymer matrix, the polymer can allow more mobile carriers to be incorporated into the polymer solution, which can further improve the transport performance. Third, a higher viscosity of the casting solution can be obtained with a higher molecular weight of PVAm, which can reduce the penetration of polymer solution into the substrate, resulting in less mass transfer resistance and higher CO2 permeance. Moreover, thinner membranes can be obtained from the solution with aATTORNEY DOCKET NO. 103362-093WO1

[0092] OSU Tech ID T2025-160 low concentration and a high viscosity, which will lead to a higher CO2 permeance.

[0093] In addition to the polymer, the membranes described herein can further comprise a gas permeable support layer and an inorganic layer disposed on the gas permeable support layer as described in PCT / US2015 / 041282.

[0094] Sweep Gas, Compression of Feed Gas, and the Application of a Vacuum

[0095] As described herein, the driving force for transmembrane separation may be provided or augmented by using a sweep on the permeate side of the membrane. This driving force can provide an improvement in the separation achieved in this step, as well as a reduction in energy consumption. The methods can employ a sweep gas with / without additional compression. Particularly, the sweep gas can reduce the partial pressure of carbon dioxide on the permeate side of a membrane, thereby no excessive feed compression or vacuum are may be necessary to supply the transmembrane driving force. Accordingly, the methods described herein include separation methods that include or exclude a sweep gas, as will be described below. When a sweep gas is used, the sweep gas can include air, oxy gen-enriched air, oxygen, nitrogen, nitrogen-enriched air, steam, or combinations thereof. In some embodiments, the sweep gas can include a portion of the retentate gas stream obtained from the one or more of the membranes used during separation.

[0096] The methods described herein can employ a vacuum at the permeate side of the membrane to provide or augmented the transmembrane driving force. In these embodiments, the method can include or exclude a sweep gas. The vacuum can be applied to generate a pressure of 0.5 atm or less (e.g. 0.4 atm or less, 0.3 atm of less, or 0.2 atm or less, such as from 0.1 to 0.5 atm, from 0.1 to 0.3 atm, or from 0.1 to 0.2 atm) on the permeate side of the first selectively permeable membrane. The feed pressure to permeate pressure ratio can (whether including or excluding a sweep gas or a vacuum) can be 7 or greater, such as 10 or greater, 15 or greater, 20 or greater, 25 or greater, 30 or greater, 35 or greater, or 40 or greater.

[0097] Likewise the pressure of a feed gas contacting the retentate side of the membranes described herein can be increased to provide or augmented the transmembrane driving force. In certain embodiments, a feed gas stream can be compressed to a pressure of at least 1.5 atm prior to passing through a selectively permeable membrane. In certain embodiments, a feed gas stream can be compressed to a pressure of from 2.5 to 5 atm prior to passing through a selectively permeable membrane.ATTORNEY DOCKET NO. 103362-093WO1

[0098] OSU Tech ID T2025-160 The third retentate stream from the 3-stage membrane separation methods is depleted in carbon dioxide and can be discharged from the method. In some embodiments, the methods described herein can reduce the carbon dioxide concentration of the feed gas stream by at least 90%, such as at least 95%, at least 98%, or at least 99%.

[0099] In some embodiments, the carbon dioxide-depleted product gas stream can include 5 vol% or less carbon dioxide. For example, the carbon dioxide-depleted product gas stream can include 4 vol% or less carbon dioxide, 3 vol% or less carbon dioxide, 2 vol% or less carbon dioxide, 2.5 vol% or less carbon dioxide, 1.5 vol% or less carbon dioxide, 1 vol% or less carbon dioxide, 0.75 vol% or less carbon dioxide, or 0.5 vol% or less carbon dioxide. In certain embodiments, the carbon dioxide-depleted product gas stream can include 0.5 vol% to 2 vol% carbon dioxide. This stream can be discharged to the environment. The reduction of the carbon dioxide content to 20%, 10% or less of the content in the raw exhaust greatly reduces the environmental impact of discharging the stream.

[0100] Membrane Separation Methods

[0101] In some embodiments, provided herein are processes for separating carbon dioxide from a feed gas stream. These methods can comprise passing the feed gas stream through a first selectively permeable membrane having a retentate side and an opposing permeate side to separate the feed gas stream into a first retentate stream and a first permeate stream; passing the first permeate stream through a second selectively permeable membrane having a retentate side and an opposing permeate side to separate the first permeate stream into a second retentate stream and a second permeate stream; passing the first retentate stream through a third selectively permeable membrane having a retentate side and an opposing permeate side to separate the first retentate stream into a third retentate stream and a third permeate stream; combining the third permeate stream with the first permeate stream prior to passing the first permeate stream through a second selectively permeable membrane; combining the second retentate stream with the feed gas stream prior to passing the feed gas stream through a first selectively permeable membrane; withdrawing the second permeate stream, wherein the second permeate stream has a greater concentration of carbon dioxide than the feed gas stream; and withdrawing the third retentate stream, wherein the third retentate stream has a lower concentration of carbon dioxide than the feed gas stream.

[0102] In some embodiments, the feed gas stream comprises from 2% to 50%, by volume (e.g., from 5% to 25%, by volume) carbon dioxide. In some embodiments, the second permeate stream comprises at least 80%, by volume, carbon dioxide, such as at least 90%,ATTORNEY DOCKET NO. 103362-093WO1

[0103] OSU Tech ID T2025-160 by volume, carbon dioxide or at least 95%, by volume, carbon dioxide. In some embodiments, the third retentate stream comprises less than 1.5%, by volume, carbon dioxide, such as less than 1%, by volume, carbon dioxide or less than 0.5%, by volume, carbon dioxide.

[0104] In some embodiments, the second permeate stream is compressed and / or used in a downstream process utilizing carbon dioxide as an input.

[0105] In some embodiments, the third retentate stream is discharged into the atmosphere as an exhaust gas.

[0106] In some embodiments, the process achieves a carbon dioxide capture, measured as a percentage of carbon dioxide present in the feed gas that is collected in the second permeate stream, of greater than 90%, such as 95% or greater, 98% or greater, or 99% or greater.

[0107] In some embodiments, the process further comprises passing the feed gas stream through a SO2 and NO2 polishing unit prior to passing the feed gas stream through the first selectively permeable membrane. In some embodiments, the feed gas stream is contacted with caustic in the SO2 and NO2 polishing unit that reacts with and reduces the concentration of SO2 in the feed gas.

[0108] In some embodiments, the feed gas stream is cooled to a temperature of from 25°C to 100°C, such as a temperature of from 40°C to 100°C, from 50°C to 100°C, from 60°C to 100°C, from 60°C to 90°C, or from 70°C to 80°C prior to passing the feed gas stream through the first selectively permeable membrane. In certain embodiments, the feed gas stream is cooled via direct contact cooling.

[0109] In some embodiments, the feed gas stream is compressed to a pressure of at least 1.5 atm prior to passing the feed gas stream through the first selectively permeable membrane. In certain embodiments, the feed gas stream is compressed to a pressure of from 2 to 5 atm prior to passing the feed gas stream through the first selectively permeable membrane.

[0110] In some embodiments, the process further comprises passing a sweep gas comprising a portion of the first retentate stream across the permeate side of the first selectively permeable membrane.

[0111] In some embodiments, the first permeate stream is compressed prior to passing the first permeate stream through the second selectively permeable membrane. In certain embodiments, the first permeate stream is compressed to a pressure of at least 1.5 atm prior to passing the first permeate stream through the second selectively permeable membrane. In certain embodiments, the first permeate stream is compressed to a pressure of from 2.5 toATTORNEY DOCKET NO. 103362-093WO1

[0112] OSU Tech ID T2025-160 5 atm prior to passing the first permeate stream through the second selectively permeable membrane.

[0113] In some embodiments, the process further comprises applying a vacuum to the permeate side of the second selectively permeable membrane. In certain embodiments, the vacuum is applied to generate a pressure of from 0.1 to 0.9 atm on the permeate side of the second selectively permeable membrane.

[0114] In some embodiments, the first retentate stream is compressed prior to passing the first retentate stream through the third selectively permeable membrane. In certain embodiments, the first retentate stream is compressed to a pressure of at least 1.5 atm prior to passing the first retentate stream through the third selectively permeable membrane. In certain embodiments, the first retentate stream is compressed to a pressure of from 2.5 to 5 atm prior to passing the first retentate stream through the third selectively permeable membrane.

[0115] In some embodiments, the process further comprises applying a vacuum to the permeate side of the third selectively permeable membrane. In some embodiments, the vacuum is applied to generate a pressure of from 0.1 to 0.5 atm on the permeate side of the third selectively permeable membrane.

[0116] In some embodiments, the process further comprises compressing the second permeate stream, such as compressing the second permeate stream to a pressure of at least 50 atm, at least 100 atm, or at least 150 atm. In some embodiments, the compressing the second permeate stream comprises a multistage compression and dehydration process.

[0117] This disclosure can be further described by the following examples, which are intended to be illustrative of the disclosure, but not limit the scope or underlying principles in any way.

[0118] EXAMPLES

[0119] The following examples are put forth so as to provide those of ordinary skill in the art with a complete disclosure and description of how the methods claimed herein are practiced and evaluated, and are intended to be purely exemplary and are not intended to limit the scope of the disclosure. Unless indicated otherwise, parts are parts by volume, temperature is in °C or is at ambient temperature, and pressure is at or near atmospheric.ATTORNEY DOCKET NO. 103362-093WO1

[0120] OSU Tech ID T2025-160 Example 1: 3-Stage Membrane Processes for Carbon Dioxide Capture from Flue Gas Background

[0121] In the past two decades, methods to accelerate the decarbonization of energy sector have been extensively investigated in order to limit the impact of global warming. The removal of CO2 from fossil fuel combustion and the subsequent underground storage, commonly known as carbon capture and storage (CCS), is regarded as one of the most reliable and affordable options. In this context, a target of “90% capture” has become ubiquitous not only in academic studies but also in sustainability policies. However, there are still residual emissions escaping the capture system, which need to be captured by “negative emissions” technologies such as direct air capture (DAC) and bioenergy with carbon capture and storage (BECCS). Comparing with carbon capture from large stationary sources, the negative emissions technologies often involve the separation or bioconversion of CO2 from air; nevertheless, the low CO2 concentration (ca. 410 ppm) requires energy-intensive separation systems with sizable footprint, which, in turn, exacerbates the energy sustainability.

[0122] Alternatively, a deep CCS concept with >90% capture has been proposed as a necessary pathway to decarbonize the power generations. This scheme aims for a higher degree of CO2 removal so that the CO2 concentration in the exhaust flue gas approaches that in air. For instance, coal flue gases typically contain ca. 13% CO2, and residual emissions with 1-2% CO2 can slip through the capture system after 90% CO2 removal. If the capture is increased to 99%, the CO2 concentration in the resultant residual flue gas can be reduced to 0.1-0.2%. In order to achieve a carbon-neutral scenario, 99.7% of the CO2 must be captured. To distinguish from negative emissions technologies, methods capable of >90% capture from stationary sources are usually referred to as “near-zero emissions” technologies.

[0123] In the current literature archive, aqueous amine absorption is the only viable technology that can achieve a capture degree up to 99.7%. It has been shown that the capture cost for beyond 90% capture is only marginally higher than that at 90% capture, which makes this near-zero emissions technology competitive with DAC. The research status is in contrast to the “partial capture” scenario, where membranes are widely investigated for 70-90% carbon capture. In other words, membrane separation is ideal for bulk separation as it is a pressure-driven process. When applied to removing dilute CO2, however, most polymeric membrane materials are limited by their insufficient CO2 / N2ATTORNEY DOCKET NO. 103362-093WO1

[0124] OSU Tech ID T2025-160 selectivities and thereby cannot achieve >95% CO2 purity. Consequently, complicated enriching cascade designs with repeated permeate recompressions are required.

[0125] Previously, we have designed two membranes processes tailored for FTMs: (1) a retentate recycle process for 90% capture from coal flue gas; (2) a two-stage enriching cascade process to remove 90% CO2 from a dilute source with 1-2% CO2. Herein, we hypothesize that these two systems can be used in tandem to achieve an overall >90% capture degree, where the retentate recycle process is responsible for the primary, bulk CO2 removal, while the enriching cascade is used to polish the residual CO2 as a secondary capture step. Two scenarios of the three-stage membrane process operations are presented to show case the feasibility.

[0126] Example 1A - Carbon Capture from Cement Kiln Flue Gas

[0127] An example carbon capture system based on a three-stage process is shown in Figure 1. For a typical cement exhaust gas containing ca. 22.4% CO2, a two-stage retentate recycle process is used as the primary capture unit to remove 90% of the CO2, resulting in the retentate stream containing ca. 2.5% CO2. This stream is further decarbonized by the polishing unit employing a single membrane stage with a higher transmembrane pressure differential. The polishing unit captures an extra 9% CO2, leading to an overall 99% CO2 capture by the membrane system. Specifically, the cement gas is cooled to 77°C via direct contact cooling (@) and is pressurized by Blower 1 to 2.5 atm (@), which is then combined with the Stage 2 retentate (®) as the feed to Stage 1 (@). This stage removes 90% of the CO2 from the flue gas, resulting in a retentate containing 2.5% CO2 (®) and a permeate with 45% CO2 (®). 20% of the CCh-lean retentate (®) is expanded and recycled to the permeate side of Stage 1 as an internal sweep (®). The remaining retentate (®) is mildly compressed by Blower 2 to 3.5 atm (®) as the feed to Stage 3, where an extra 9% of the CO2 from the flue gas is stripped, resulting in a retentate with 0.3% CO2 (®) and a permeate with 40% CO2 (©). The retentate is expanded for energy recovery (@). Vacuum Pump 1 pulls a vacuum of 0.2 atm on the permeate side of Stage 3. The vacuum discharge (@) is combined with the Stage 1 permeate, and this stream (®) is repressurized by Blower 3 to 2.5 atm (©), which is separated by Stage 2 into a retentate containing ca. 20% CO2 (®) and a permeate with >95% CO2 on dry basis (©). Vacuum Pump 2 is used to pull a 0.8 atm vacuum on the permeate side, and its discharge (®) is sent to an 8-stage compressor train for a CO2 product pressure of 150 atm (©).

[0128] Figure 1 incorporates specific example design features within the flow diagrams.ATTORNEY DOCKET NO. 103362-093WO1

[0129] OSU Tech ID T2025-160 However, design elements for the membrane process’s operation will be discussed in detail below.

[0130] Firstly, the cement gas enters parallel SO2 and NO2 polishers, an example of which is shown in Figure 2.

[0131] The cement gas enters the bottom portion of the contactor, in which the SO2 polishing section is located. Here, a dilute caustic (5%) is utilized to react with SO2 and reduce its concentration in the flue gas from 25 to 2 ppmv. Makeup caustic (50 wt%) and is pumped the SO2 polishing recirculation loop. The caustic solution is circulated through the packed bed in the contractors by the trim SO2 recirculation pumps. Caustic strength is reduced from 50 wt% to 5 wt% by adding dilution water to the solution. The blowdown from the SO2 polishing section will contain ISfeSCh and NaHSCh. The diluted salt solution of 7 - 8 wt% will be sent to wastewater treatment. The top portion of the contractor holds the direct contact cooler (DCC) section. Once the cement gas exits the SO2 polishing portion, it then enters the top DCC section that cools the gas from 110 to 50°C. The DCC uses water in the pumps to circulate water over the packed bed in the contactors. The DCC exchanger temperature is maintained from the cooling water that is part of the plant system. The dilution water for the SO2 polisher section is from a slip stream from the DCC loop.

[0132] Furthermore, a heat integration approach is employed in the gas compression and energy recovery systems, as demonstrated for example in Figure 3. Specifically, the two turboexpanders generate power using the retentate stream from the Membrane Stage 1 unit. The thermal expansion process cools the retentate, which serves as the cooling agent for the compression of cement gas, reducing the need for cooling water. Additionally, the heating of the retentate upon thermal expansion mitigates water condensation and enhances energy recovery efficiency

[0133] Additionally, an example CO2 compression and dehydration process is shown in Figure 4. The permeate leaving the Membrane Stage 2 is rich in CO2 and is then precooled. A two-stage fan system is used to compress the cooled permeate to 196 kPa-abs. The two-stage fan system also incorporates interstage cooling along with separation vessels for the condensed water. The centrifugal compressor system is multistage with cooling and vessels for liquid knock-out in between each stage. The compressor system increases the CO2 to 15.3 MPa. The evaluation of the system is done using eight stages. Each stage is followed by a cooler that uses plant cooling water to decrease the temperature of the gas to approximately 30°C before the following compression stage. A dehydration system is usedATTORNEY DOCKET NO. 103362-093WO1

[0134] OSU Tech ID T2025-160 to remove residual water following the fourth stage. After the fourth stage, approximately 87% of the water is removed from the stream. In order to remove residual water, the dehydration train is the most cost-effective and space-efficient option. It is important to ensure that all the water is removed from the stream because of the safety concerns that come with transporting saturated CO2 in pipelines where the stream will cool further and cause corrosive conditions for the pipeline. The unit that is used for dehydration is a conventional triethylene glycol (TEG) system and is commonly used for the dehydration of CO2 and natural gas. An example dehydration unit is shown in Figure 5. The water that is condensed out of the stream is sent to the water circulation tank.

[0135] Table 1 shows a representative stream table for 99% CO2 capture and >95% purity in a reference Best Available Techniques (BAT) cement plant with a nominal 100,000 tonne of CO2 captured per year, which typically emits 18 - 23% CO2; hence the 22.4% CO2 is used in the cement gas.

[0136] Table 1. Stream table for 99% CO2 capture and >95% CO2 purity in a BAT cement plant.

[0137]

[0138] ATTORNEY DOCKET NO. 103362-093WO1

[0139] OSU Tech ID T2025-160

[0140]

[0141] The energy performance for the transformational membrane process was evaluated by the power needs for cement gas compression, permeate compression, and the CO2 compression. The power requirement estimations were done by using Aspen HYSYS process simulations. The membrane-based process does not use steam for any components; thus, the parasitic energy demand of the capture process on the power plant does not include steam. The result of the analysis is summarized in Table 2, which shows the categorization of the components that have an energy demand, or “derating”, due to the CO2 capture. The energy derate refers to the BAT cement plant with a nominal 100,000 tonne of CO2 captured per year.

[0142] Table 2. Energy performance summary.

[0143]

[0144] ATTORNEY DOCKET NO. 103362-093WO1

[0145] OSU Tech ID T2025-160 Example 1-2 - Carbon Capture from Natural Gas Combined Cycle (NGCC) Flue Gas

[0146] An example carbon capture system based on a three-stage process is shown in Figure 6. The primary capture unit, including Membrane Stage 1 and Membrane Stage 2 in an enriching cascade configuration, removes 80% of the CO2 from the NGCC flue gas (4.1% CO2). The residual flue gas contains 0.85% CO2 and is further decarbonized by Membrane Stage 3 to be added for the modified skid, using a higher transmembrane pressure differential, to achieve an additional 15% capture for an overall 95% CO2 capture. The permeate of Membrane Stage 3 is passed to Membrane Stage 2 for further enrichment to >95% CO2 purity, which is eventually compressed to 150 atm for enhanced oil recovery or sequestration. Specifically, the NGCC flue gas is cooled to 77°C via direct contact cooling (Q) and is pressurized by Blower 1 to 4 atm (@), which is then combined with the Stage 2 retentate (@) as the feed to Stage 1 ((D)- This stage removes 80% of the CO2 from the flue gas, resulting in a retentate containing 0.85% CO2 (@) and a permeate with 30% CO2 ((D)- The retentate is mildly compressed by Blower 3 to 4.5 atm (@) as the feed to Stage 3, where an extra 15% of the CO2 from the flue gas is recovered (with 80% recovery from Stage 1 for a total recovery of 95%), resulting in a retentate with 0.21% CO2 (( ) and a permeate with 20% CO2 ((D)- The retentate is expanded for energy recovery ((D)- The permeates of Stages 1 and 3 are combined (@) and processed by Vacuum Pump 1, which creates a vacuum of 0.2 atm for both Stages 1 and 3. The vacuum discharge (@) is repressurized by Blower 2 to 4 atm (©), which is separated by Stage 2 into a retentate containing ca. 4% CO2 (®) and a permeate with >95% CO2 on dry basis (@). Vacuum Pump 2 is used to pull a 0.2 atm vacuum on the permeate side, and its discharge (@) is sent to an 8-stage compressor train for a CO2 product pressure of 150 atm (@).

[0147] Table 3 shows a representative stream table for 95% CO2 capture and >95% purity in a reference NGCC plant delineated as Case B3 IB.95 in DOE’s Bituminous Baseline Study (BBS), Rev. 4a. To achieve 650 MW net power, the gross power generated is 691 MWewith an auxiliary load of 44.1 MWeincluding CO2 compression to 150 atm. No steam is extracted from the plant.ATTORNEY DOCKET NO. 103362-093WO1

[0148] OSU Tech ID T2025-160 Table 3. Stream table for 95% CO2 capture and >95% CO2 purity.

[0149]

[0150] The energy performance for the transformational membrane process was evaluated by the power needs for flue gas compression, permeate compression, and the CO2 compression. The power requirement estimations were done by using Aspen HYSYS process simulations. The membrane-based process does not use steam for any components; thus, the parasitic energy demand of the capture process on the power plant does not include steam. The result of the analysis is summarized in Table 4, which shows the categorization of the components that have an energy demand, or “derating”, due to the CO2 capture.ATTORNEY DOCKET NO. 103362-093WO1

[0151] OSU Tech ID T2025-160 Table 4. Energy performance summary.

[0152]

[0153] References

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[0167] 13. A. Hussain and M.-B. Hagg, “A Feasibility Study of CO2 Capture from Flue Gas by a Facilitated Transport Membrane”, Journal of Membrane Science, 359, 140-148 (2010). 14. P. Brandl, M. Bui, J. P. Hallett, and N. Mac Dowell, “Beyond 90% Capture: Possible, but at What Cost?”, International Journal of Greenhouse Gas Control, 105, 103239 (2021).

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[0171] OSU Tech ID T2025-160 18. K. Ramasubramanian, H. Verweij, and W. S. W. Ho, “Membrane Processes for Carbon Capture from Coal-Fired Power Plant Flue Gas: A Modeling and Cost Study”, Journal of Membrane Science, 421-422, 299-310 (2012).

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[0182] OSU Tech ID T2025-160 30. T. Schmitt, S. Leptinsky, M. Turner, A. Zoelle, C. W. White, S. Hughes, S. Homsy, M. Woods, H. Hoffman, T. Shultz, and R. James, Cost and Performance Baseline for Fossil Energy Plants Volume 1 : Bituminous Coal and Natural Gas to Electricity, Revision 4a, National Energy Technology Laboratory, Pittsburgh, October 14, 2022,

[0183] The methods of the appended claims are not limited in scope by the specific methods described herein, which are intended as illustrations of a few aspects of the claims and any methods that are functionally equivalent are intended to fall within the scope of the claims. Various modifications of the methods in addition to those shown and described herein are intended to fall within the scope of the appended claims. Further, while only certain representative materials and method steps disclosed herein are specifically described, other combinations of the materials and method steps also are intended to fall within the scope of the appended claims, even if not specifically recited. Thus, a combination of steps, elements, components, or constituents may be explicitly mentioned herein; however, other combinations of steps, elements, components, and constituents are included, even though not explicitly stated. The term “comprising” and variations thereof as used herein is used synonymously with the term “including” and variations thereof and are open, non-limiting terms. Although the terms “comprising” and “including” have been used herein to describe various embodiments, the terms “consisting essentially of’ and “consisting of’ can be used in place of “comprising” and “including” to provide for more specific embodiments and are also disclosed. As used in this disclosure and in the appended claims, the singular forms “a”, “an”, “the”, include plural referents unless the context clearly dictates otherwise.

Claims

ATTORNEY DOCKET NO. 103362-093WO1OSU Tech ID T2025-160 What is claimed is:

1. A process for separating carbon dioxide from a feed gas stream, the method comprising:passing the feed gas stream through a first selectively permeable membrane having a retentate side and an opposing permeate side to separate the feed gas stream into a first retentate stream and a first permeate stream;passing the first permeate stream through a second selectively permeable membrane having a retentate side and an opposing permeate side to separate the first permeate stream into a second retentate stream and a second permeate stream;passing the first retentate stream through a third selectively permeable membrane having a retentate side and an opposing permeate side to separate the first retentate stream into a third retentate stream and a third permeate stream;combining the third permeate stream with the first permeate stream prior to passing the first permeate stream through a second selectively permeable membrane;combining the second retentate stream with the feed gas stream prior to passing the feed gas stream through a first selectively permeable membrane;withdrawing the second permeate stream, wherein the second permeate stream has a greater concentration of carbon dioxide than the feed gas stream; andwithdrawing the third retentate stream, wherein the third retentate stream has a lower concentration of carbon dioxide than the feed gas stream.

2. The process of claim 1, wherein the feed gas stream comprises a combustion gas.

3. The process of claim 1 or 2, wherein the feed gas stream comprises from 2% to 50%, by volume, carbon dioxide.

4. The process of any one of claims 1-3, wherein the feed gas stream comprises from 5% to 25%, by volume, carbon dioxide.

5. The process of any one of claims 1-4, wherein the second permeate stream comprises at least 80%, by volume, carbon dioxide, such as at least 90%, by volume, carbon dioxide or at least 95%, by volume, carbon dioxide.ATTORNEY DOCKET NO. 103362-093WO1OSU Tech ID T2025-160 6. The process of any one of claims 1-5, wherein the third retentate stream comprises less than 1.5%, by volume, carbon dioxide, such as less than 1%, by volume, carbon dioxide or less than 0.5%, by volume, carbon dioxide.

7. The process of any one of claims 1-6, wherein the process achieves a carbon dioxide capture, measured as a percentage of carbon dioxide present in the feed gas that is collected in the second permeate stream, of greater than 90%, such as 95% or greater, 98% or greater, or 99% or greater.

8. The process of any one of claims 1-7, wherein the process further comprises passing the feed gas stream through a SO2 and NO2 polishing unit prior to passing the feed gas stream through the first selectively permeable membrane.

9. The process of claim 8, wherein the feed gas stream is contacted with caustic that reacts with and reduces the concentration of SO2 in the feed gas.

10. The process of any one of claims 1-9, wherein the feed gas stream is cooled to a temperature of from 25 °C to 100°C, such as a temperature of from 40°C to 100°C, from 50°C to 100°C, from 60°C to 100°C, from 60°C to 90°C, or from 70°C to 80°C prior to passing the feed gas stream through the first selectively permeable membrane.

11. The process of claim 10, wherein the feed gas stream is cooled via direct contact cooling.

12. The process of any one of claims 1-11, wherein the feed gas stream is compressed to a pressure of at least 1.5 atm prior to passing the feed gas stream through the first selectively permeable membrane.

13. The process of claim 12, wherein the feed gas stream is compressed to a pressure of from 2 to 5 atm prior to passing the feed gas stream through the first selectively permeable membrane.ATTORNEY DOCKET NO. 103362-093WO1OSU Tech ID T2025-160 14. The process of any one of claims 1-13, further comprising passing a sweep gas comprising a portion of the first retentate stream across the permeate side of the first selectively permeable membrane.

15. The process of any one of claims 1-14, wherein the first permeate stream is compressed prior to passing the first permeate stream through the second selectively permeable membrane.

16. The process of claim 15, wherein the first permeate stream is compressed to a pressure of at least 1.5 atm prior to passing the first permeate stream through the second selectively permeable membrane.

17. The process of claim 15 or 16, wherein the first permeate stream is compressed to a pressure of from 2.5 to 5 atm prior to passing the first permeate stream through the second selectively permeable membrane.

18. The process of any one of claims 1-17, further comprising applying a vacuum to the permeate side of the second selectively permeable membrane.

19. The process of claim 18, wherein the vacuum is applied to generate a pressure of from 0.1 to 0.9 atm on the permeate side of the second selectively permeable membrane.

20. The process of any one of claims 1-19, wherein the first retentate stream is compressed prior to passing the first retentate stream through the third selectively permeable membrane.

21. The process of claim 20, wherein the first retentate stream is compressed to a pressure of at least 1.5 atm prior to passing the first retentate stream through the third selectively permeable membrane.

22. The process of claim 20 or 21, wherein the first retentate stream is compressed to a pressure of from 2.5 to 5 atm prior to passing the first retentate stream through the third selectively permeable membrane.ATTORNEY DOCKET NO. 103362-093WO1OSU Tech ID T2025-160 23. The process of any one of claims 1-22, further comprising applying a vacuum to the permeate side of the third selectively permeable membrane.

24. The process of claim 23, wherein the vacuum is applied to generate a pressure of from 0.1 to 0.5 atm on the permeate side of the third selectively permeable membrane.

25. The process of any one of claims 1-24, further comprising compressing the second permeate stream, such as compressing the second permeate stream to a pressure of at least 50 atm, at least 100 atm, or at least 150 atm.

26. The process of any one of claims 1-25, wherein compressing the second permeate stream comprises a multistage compression and dehydration process.

27. The process of any one of claims 1-26, wherein the first selectively permeable membrane exhibits a carbon dioxide permeance of at least 500 gas permeance units (GPU) at 57°C and 1 atm feed pressure.

28. The process of any one of claims 1-27, wherein the first selectively permeable membrane exhibits a carbon dioxide permeance of from 500 to 3000 GPU at 57°C and 1 atm feed pressure.

29. The process of any one of claims 1-28, wherein the first selectively permeable membrane exhibits a carbon dioxide permeance of from 1000 to 1500 GPU at 57°C and 1 atm feed pressure.

30. The process of any one of claims 1-29, wherein the first selectively permeable membrane exhibits a carbon di oxi de: nitrogen selectivity of from 10 to 1000 at 57°C and 1 atm feed pressure31. The process of any one of claims 1-30, wherein the first selectively permeable membrane exhibits a carbon di oxi de: nitrogen selectivity of from 50 to 1000 at 57°C and 1 atm feed pressure.ATTORNEY DOCKET NO. 103362-093WO1OSU Tech ID T2025-160 32. The process of any one of claims 1-31, wherein the first selectively permeable membrane exhibits a carbon di oxi de: nitrogen selectivity of from 100 to 500 at 57°C and 1 atm feed pressure.

33. The process of any one of claims 1-32, wherein the first selectively permeable membrane exhibits a carbon dioxide permeance of from 1000 to 1500 GPU at 57°C and 1 atm feed pressure and a carbon di oxi de: nitrogen selectivity of from 100 to 500 at 57°C and 1 atm feed pressure.

34. The process of any one of claims 1-33, wherein the first selectively permeable membrane comprises a selective polymer layer comprising an amine-containing polymer chosen from polyvinylamine, polyallylamine, polyethyleneimine, poly-A-isopropylallylamine, poly-7V-tert-butylallylamine, poly-7V-l,2-dimethylpropylallylamine, poly-7V-methylallylamine, poly-7V,7V-dimethylallylamine, poly-2 -vinylpiperidine, poly-4-vinylpiperidine, polyaminostyrene, chitosan, copolymers, and blends thereof.

35. The process of claim 34, wherein the amine-containing polymer comprises polyvinylamine.

36. The process of claim 34 or 35, wherein the selective polymer layer further comprises an aminoacid salt dispersed within the amine-containing polymer.

37. The process of any one of claims 1-36, wherein the second selectively permeable membrane exhibits a carbon dioxide permeance of at least 500 gas permeance units (GPU) at 57°C and 1 atm feed pressure.

38. The process of any one of claims 1-37, wherein the second selectively permeable membrane has a carbon dioxide permeance of from 500 to 3000 GPU at 57°C and 1 atm feed pressure.

39. The process of any one of claims 1-38, wherein the second selectively permeable membrane has a carbon dioxide permeance of from 1000 to 1500 GPU at 57°C and 1 atm feed pressure.ATTORNEY DOCKET NO. 103362-093WO1OSU Tech ID T2025-160 40. The process of any one of claims 1-39, wherein the second selectively permeable membrane exhibits a carbon di oxi de: nitrogen selectivity of from 10 to 1000 at 57°C and 1 atm feed pressure41. The process of any one of claims 1-40, wherein the second selectively permeable membrane exhibits a carbon di oxi de: nitrogen selectivity of from 50 to 1000 at 57°C and 1 atm feed pressure.

42. The process of any one of claims 1-41, wherein the second selectively permeable membrane exhibits a carbon di oxi de: nitrogen selectivity of from 100 to 500 at 57°C and 1 atm feed pressure.

43. The process of any one of claims 1-42, wherein the second selectively permeable membrane has a carbon dioxide permeance of from 1000 to 1500 GPU at 57°C and 1 atm feed pressure and a carbon di oxi de: nitrogen selectivity of from 100 to 500 at 57°C and latm feed pressure.

44. The process of any one of claims 1-43, wherein the second selectively permeable membrane comprises a selective polymer layer comprising an amine-containing polymer chosen from polyvinylamine, polyallylamine, polyethyleneimine, poly-A-isopropylallylamine, poly-7V-tert-butylallylamine, poly-7V-l,2-dimethylpropylallylamine, poly-7V-methylallylamine, poly-7V,7V-dimethylallylamine, poly-2 -vinylpiperidine, poly-4-vinylpiperidine, polyaminostyrene, chitosan, copolymers, and blends thereof.

45. The process of claim 44, wherein the amine-containing polymer comprises polyvinylamine.

46. The process of claim 44 or 45, wherein the selective polymer layer further comprises an aminoacid salt dispersed within the amine-containing polymer.

47. The process of any one of claims 1-46, wherein the third selectively permeable membrane exhibits a carbon dioxide permeance of at least 500 gas permeance units (GPU) at 57°C and 1 atm feed pressure.ATTORNEY DOCKET NO. 103362-093WO1OSU Tech ID T2025-160 48. The process of any one of claims 1-47, wherein the third selectively permeable membrane has a carbon dioxide permeance of from 500 to 3000 GPU at 57°C and 1 atm feed pressure.

49. The process of any one of claims 1-48, wherein the third selectively permeable membrane has a carbon dioxide permeance of from 1000 to 1500 GPU at 57°C and 1 atm feed pressure.

50. The process of any one of claims 1-49, wherein the third selectively permeable membrane exhibits a carbon di oxi de: nitrogen selectivity of from 10 to 1000 at 57°C and 1 atm feed pressure51. The process of any one of claims 1-50, wherein the third selectively permeable membrane exhibits a carbon di oxi de: nitrogen selectivity of from 50 to 1000 at 57°C and 1 atm feed pressure.

52. The process of any one of claims 1-51, wherein the third selectively permeable membrane exhibits a carbon di oxi de: nitrogen selectivity of from 100 to 500 at 57°C and 1 atm feed pressure.

53. The process of any one of claims 1-52, wherein the third selectively permeable membrane has a carbon dioxide permeance of from 1000 to 1500 GPU at 57°C and 1 atm feed pressure and a carbon di oxi de: nitrogen selectivity of from 100 to 500 at 57°C and latm feed pressure.

54. The process of any one of claims 1-53, wherein the third selectively permeable membrane comprises a selective polymer layer comprising an amine-containing polymer chosen from polyvinylamine, polyallylamine, polyethyleneimine, poly-7V-isopropylallylamine, poly-7V-tert-butylallylamine, poly-7V-l,2-dimethylpropylallylamine, poly-7V-methylallylamine, poly-7V,7V-dimethylallylamine, poly-2 -vinylpiperidine, poly-4-vinylpiperidine, polyaminostyrene, chitosan, copolymers, and blends thereof.ATTORNEY DOCKET NO. 103362-093WO1OSU Tech ID T2025-160 55. The process of claim 54, wherein the amine-containing polymer comprises polyvinylamine.

56. The process of claim 54 or 55, wherein the selective polymer layer further comprises an aminoacid salt dispersed within the amine-containing polymer.

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