Nanopore membrane and its use for gas separation

Abstract

The present invention relates to a process for producing a nanopore carbon membrane, the membranes obtainable by this process, a process for gas separation using these membranes, and the use of membranes of this kind.

Description

[0001] Nanoporous membrane and its use for gas separation

[0002] Description

[0003] The present invention relates to a process for producing a nanoporous carbon membrane, the membranes obtainable by this process, a process for gas separation using these membranes and the use of such membranes.

[0004] BACKGROUND OF THE INVENTION

[0005] The separation of gas mixtures is becoming increasingly important for the efficient use of gas streams from existing processes, as well as for the development of new resources. A particular challenge is the selective separation of individual components from gas mixtures containing light hydrocarbons and / or hydrogen, and possibly other light gases such as carbon monoxide. Currently, the separation of such gas mixtures is often still carried out using low-temperature distillation, a process that is highly energy-intensive and requires a high level of equipment complexity.

[0006] Firstly, in view of the energy transition, there is a need to utilize hydrocarbon streams, such as methane, from sources that contain significant amounts of impurities from other gases, such as carbon dioxide or nitrogen. To utilize biogas or natural gas from sources with higher proportions of other gases, purification is generally required to meet technical requirements, e.g., for feeding into a gas supply network. Special demands are placed on the purity of methane-containing gas streams for liquefaction and transport via pipelines or by ship.

[0007] Second, as part of the transition to low-carbon energy systems, there is a high demand for hydrogen, ideally from renewable sources, existing large-scale processes, or carbon-containing waste, especially plastic waste. Hydrogen is a highly efficient and clean energy carrier whose conversion to energy produces only water as a by-product. It is suitable for a variety of storage methods and is considered an important component in the development of solutions to global climate change. Currently, large-scale hydrogen production is typically achieved through steam methane reforming (SMR), coal gasification, or partial oxidation of hydrocarbons. These hydrogen production processes produce hydrogen-rich streams (such as syngas / oxogas) containing other gas components such as CO, CO2, N2, and / or lower hydrocarbons such as CH4, C2H6, C3H8, C4Hw, etc.

[0008] Steam reforming is a process in which a carbon-containing fuel, such as natural gas (whose main component is methane), reacts with steam. Partial oxidation of the fuel occurs, producing hydrogen, as in the conversion of methane: CH4 + H2O — ► CO + 3 H2. The hydrogen yield increases further when the carbon monoxide (CO) is further oxidized to carbon dioxide (CO2): CO + H2O —> CO2 + H2. This reaction is called a water-gas shift reaction.

[0009] Syngas refers to gases that contain hydrogen and carbon monoxide and can be used for various chemical syntheses. The classic method for producing syngas is the gasification of coal with the addition of steam and oxygen. In this process, oxygen is removed from the water (H2O), which, together with the directly introduced oxygen, oxidizes the coal to carbon monoxide and, in some cases, carbon dioxide. The result is a mixture of hydrogen (H2), carbon monoxide (CO), carbon dioxide (CO2), and various impurities (e.g., sulfur compounds due to the sulfur content of the coal). Gas purification is often carried out before further processing to remove soot and metals, to dry the gas (remove unconverted steam), to capture CO2, and / or to remove sulfur compounds. Crude oil fractions and natural gas can also be used to produce syngas.In addition, the recycling of carbon-containing waste, such as plastic waste (e.g. from the "yellow bag" waste collection), into syngas and further into basic chemicals such as methanol, is gaining importance recently, as this addresses both the waste problem and the desired circular economy.

[0010] The separation and concentration of gases using a gas separation membrane is a process that offers several advantages over other methods such as distillation or high-pressure adsorption, including greater flexibility and safety, generally lower equipment costs, and good energy efficiency. Membrane processes have long been used to separate gases based on their size and / or affinity.

[0011] The use of nanoporous carbon membranes for the separation of hydrogen and hydrocarbon mixtures is known. In the Journal of Membrane Science 110 (1996), pp. 109-118, M.B. Rao and S. Sircar describe the use of a nanoporous carbon membrane capable of selectively adsorbing hydrocarbons from mixtures with hydrogen on the high-pressure side, with the adsorbed gas molecules then diffusing through the pores of the membrane to the low-pressure side. To produce the membrane, layers of a polyvinylidene chloride latex are deposited on an aluminum oxide support and carbonized in an inert atmosphere at 600 to 1000°C. A corresponding product from Air Products and Chemicals, called the "SSF membrane," proved economically unviable and never found widespread use.

[0012] US 2022 / 040644 A1 describes a membrane for purifying or separating hydrogen from a multi-component gas stream, such as synthesis gas. It is a multi-stage hybrid membrane comprising a sieve-shaped support material and two layers thereon, both of which contain carbon fibers, a transition metal compound, a fluorine-containing polymer, and activated or small-pore carbon. The activated carbon used in the membrane layers has nanopores with a diameter of less than 3 nm. No information is provided in this document regarding the pore size of the hybrid membrane layers. Therefore, US 2022 / 040644 A1 explicitly does not describe a membrane device for selective gas separation that has a nanoporous carbon-containing layer with an average pore size in the range of 0.3 to 2.0 nm and a pore size distribution in the range of 0.1 to 5.0 nm.

[0013] US Pat. No. 9,694,344 B2 describes a multilayer polymer membrane containing a sorting material and a plurality of connecting pores, as well as a one-step coextrusion process for its production. Sorbent materials include carbonaceous materials. The membrane can have up to approximately 100 layers, each of which can differ in its pore structure. A general average diameter in the range of approximately 0.01 nm to approximately 50 pm is specified for the connecting pores.

[0014] The known membranes do not yet have a suitable property profile for all separation tasks. In particular, the known manufacturing processes are very complex and do not allow the membrane properties to be varied to adapt them to the specific separation task. There is a need for a membrane device for selective gas separation, especially for the separation of gas mixtures containing hydrocarbons and hydrogen. This should eliminate the need for complex manufacturing processes, such as the layer-by-layer coating of a porous support material, e.g., aluminum oxide, followed by carbonization. The manufacturing process should enable the simplest possible adaptation of the separation characteristics to different separation problems.In particular, the invention is based on the object of providing a permselective membrane for the separation of hydrocarbons, especially Ci to Cu hydrocarbons, more especially Ci to C8 hydrocarbons, even more especially Ci to C4 hydrocarbons, from hydrogen-containing gas mixtures.

[0015] Surprisingly, it was found that this object is achieved by a membrane device and a method for its production, wherein a porous support material is coated with a nanoporous carbon-containing layer of defined pore size and pore size distribution.

[0016] SUMMARY OF THE INVENTION

[0017] A first subject matter of the invention is a membrane device for selective gas separation, comprising a) a flat, gas-permeable support material and b) a nanoporous carbon-containing layer on at least one of the surfaces of the support material, wherein the nanoporous layer comprises at least one carbon component in a polymeric binder, wherein the nanoporous carbon-containing layer preferably has an average pore size in the range of 0.3 to 2.0 nm and a pore size distribution in the range of 0.1 to 5.0 nm.

[0018] The invention further provides a membrane device for selective gas separation, comprising a) a flat, gas-permeable support material a) a microporous layer on at least one of the surfaces of the support material, b) a nanoporous carbonaceous layer on the microporous layer a) wherein the nanoporous layer comprises at least one carbon component in a polymeric binder, and wherein the nanoporous carbonaceous layer has an average pore size in the range of 0.3 to 2.0 nm and a pore size distribution in the range of 0.1 to 5.0 nm. The average pore size and the pore size distribution of the nanoporous layer are determined specifically by means of permeporosimetry.

[0019] The invention further relates to a method for producing a membrane device, comprising i) providing a flat, gas-permeable support material a), ii) coating the support material provided in step i) with a coating agent to form a nanoporous carbon-containing layer, wherein the pores have an average pore size in the range of 0.3 to 2 nm and a pore size distribution of 0.1 to 5.0 nm. The average pore size and the pore size distribution are determined specifically by means of permeporosimetry.

[0020] The invention further relates to a method for producing a membrane device, in which i) a flat gas-permeable support material a) is provided, ii-a) the support material provided in step i) is coated with a coating agent to form a microporous layer, ii-b) the coated support material obtained in step ii-a) is coated with a coating agent to form a nanoporous carbon-containing layer, wherein the pores have an average pore size in the range of 0.3 to 2 nm and a pore size distribution of 0.1 to 5.0 nm.

[0021] Preferably, step i) of the two aforementioned processes comprises

[0022] 11) provides a fiber composition comprising carbon fibers and / or precursors of carbon fibers as a flat, gas-permeable carrier material,

[0023] 12) subjecting the fibre composition provided in step i1) to a process for producing a nonwoven fabric,

[0024] 13) if the fiber composition used in step i1) comprises precursors of carbon fibers, subjecting the nonwoven fabric to pyrolysis at a temperature of at least 1000 °C. A preferred embodiment is a process in which

[0025] 11) provides a fiber composition comprising carbon fibers and / or precursors of carbon fibers as a flat, gas-permeable carrier material,

[0026] 12) subjecting the fibre composition provided in step i1) to a process for producing a nonwoven fabric,

[0027] 13) if the fiber composition used in step i1) comprises precursors of carbon fibers, subjecting the nonwoven fabric to pyrolysis at a temperature of at least 1000 °C, ii) coating the nonwoven fabric obtained in step i2) or i3) with a nanoporous layer.

[0028] Another object of the invention is a membrane device obtainable by a process as defined above and below.

[0029] The invention further provides a process for the at least partial separation of at least one gas component from a gas mixture, in which a starting gas mixture is subjected to a separation into at least one retentate stream and at least one permeate stream in at least one membrane separation stage, wherein the membrane separation stage comprises at least one membrane device as defined above and below or obtainable by a process as defined above and below.

[0030] A further subject of the invention is the use of a membrane device as defined above and below, or obtainable by a process as defined above and below, for selective gas separation, preferably for selective separation of a gas mixture from large-scale hydrogen production, in particular for selective separation of a gas mixture comprising hydrogen and at least one Ci-Cu hydrocarbon, preferably at least one Ci-C e -hydrocarbon, contains.

[0031] DESCRIPTION OF THE INVENTION

[0032] The membrane devices according to the invention for selective gas separation and their production by coating a support material with a nanoporous carbonaceous layer have the following advantages: Compared to conventional processes such as rectification at low temperatures, physical or chemical absorption, and adsorption, e.g., on activated carbon or zeolites, the membrane devices according to the invention have the advantage of a simple, flexible, and possibly mobile plant design with a small footprint, which is also generally characterized by low investment costs and low energy consumption. Furthermore, gas separation can be designed as a continuous process with only one stage.

[0033] Production can be achieved using established techniques for coating flat substrates, especially flat fiber materials, with porous carbon-containing layers. The complex, sometimes multi-stage coating of inert solid inorganic substrates and subsequent adjustment of selectivity via carbonization can be dispensed with.

[0034] Without being bound to any theory, it is assumed that the mechanism of gas separation by the membrane device according to the invention occurs partially or completely via capillary condensation. Specifically, gas separation by means of the nanoporous carbon-containing layer occurs via capillary condensation. This is a transport process that typically occurs in small-pore membranes when a gaseous component can condense in the pores of the membrane. The membrane devices according to the invention are particularly suitable for the separation of hydrocarbons from gas mixtures containing at least one light gas selected from hydrogen, carbon monoxide, carbon dioxide, nitrogen, and mixtures thereof. Very high selectivities can be achieved with respect to the component permeating through the membrane (usually the hydrocarbons).

[0035] The membrane devices are characterized by high temperature and pressure resistance.

[0036] The permeance refers to the flow in standard cubic meters of gas per m 2 Membrane area, time, and pressure, where pressure is the partial pressure difference between the feed / retentate and the permeate of the respective gas. Permselectivity results from the ratio of the determined permeances of the individual components of the gas mixture to be separated.

[0037] Advantageously, the membrane device according to the invention has a permeance for hydrocarbons of such a magnitude that it is possible to separate hydrocarbons from gas mixtures which comprise at least one light gas selected from hydrogen, carbon monoxide, carbon dioxide, nitrogen and mixtures thereof.

[0038] The pore size and pore size distribution of the nanoporous carbonaceous layer can be determined using permporosimetry. The principle of permporosimetry is based on the controlled, step-by-step blocking of pores by capillary condensation of a condensable component of a gas mixture with simultaneous measurement of the gas flow through the membrane. The principle is described, for example, by FC Cuperus et al. in J. Membrane Sci. 71 (1992), 57-67. Commercial devices are available from Porometer, APTCO TECHNOLOGIES NV, Belgium. Olga Solcova et al. describe in Liquid Expulsion Permporometry - a Tool for Obtaining the Distribution of Flow-Through Pores, Part. Part. Syst. Charact. 23 (2006) 1-8, DOI: 10.1002 / ppsc.200601014, the application of permporometry to porous materials of greater thickness and broad pore size distribution.

[0039] The nanoporous carbonaceous layer has an average pore size in the range of 0.3 to 2.0 nm, preferably from 0.4 to 1.5 nm, particularly preferably from 0.5 to 1.3 nm, determined by permporosimetry.

[0040] The nanoporous carbonaceous layer has a pore size distribution in the range of 0.1 to 5.0 nm, determined by permporosimetry.

[0041] The nanoporous carbon-containing layer preferably has a layer thickness in the range of 0.5 to 500 pm, particularly preferably from 1.0 to 10 pm.

[0042] The nanoporous carbonaceous layer preferably has a porosity, determined as the ratio of the volume fraction of the pores to the total volume of the nanoporous carbonaceous layer, in the range of 20 to 80%, particularly preferably 60 to 70%. The pore volume fraction can be determined using permporosimetry.

[0043] Flat carrier material a)

[0044] The membrane device according to the invention for selective gas separation comprises at least one flat gas-permeable carrier material a).

[0045] Preferably, the sheet-like gas-permeable carrier material a) is selected from fiber materials, porous metallic carriers, porous ceramic and non-ceramic carriers, monolithic carriers, gas-permeable polymeric carriers and combinations thereof.

[0046] Suitable fiber materials include organic fibers, inorganic fibers, and combinations thereof. Preferably, the fiber material comprises fibers of synthetic polymers, fibers of natural polymers, carbon fibers, metal fibers, ceramic fibers, glass fibers, basalt fibers, silica fibers, mineral fibers, and combinations thereof. In a preferred embodiment, the carrier material a) comprises at least one sheet-like fiber material or the carrier material a) consists of at least one sheet-like fiber material, wherein the carrier material is preferably selected from nonwovens, woven fabrics, knitted fabrics, papers, and combinations thereof.

[0047] For the purposes of the invention, a nonwoven generally refers to a sheet-like structure consisting primarily of individual fibers whose cohesion is essentially achieved solely by their inherent adhesion. The conversion of a nonwoven into a nonwoven fabric by creating a stronger bond between the fibers than that present in the nonwoven is achieved by nonwoven bonding processes, which are usually divided into mechanical, chemical, and thermal processes. Nonwovens, nonwoven fabrics, and processes for their production are described in H. Fuchs and W. Albrecht, Vliesstoffe (Vlieses), 2nd edition, Wiley-VCH, Weinheim, Germany.

[0048] Suitable porous metallic supports include porous metals such as aluminum or metal mesh.

[0049] Suitable inorganic supports include porous ceramic and non-ceramic supports. Suitable support materials include clay minerals, aluminum oxides, silicon oxides, aluminosilicates, especially zeolites, zirconium dioxide, titanium dioxide, yttrium oxide, other metal oxides, glass, silicon nitride, silicon carbide, Si-CO, Si-CNO, Si-BNC, etc., and combinations thereof.

[0050] Other suitable supports include monolithic supports. Such supports and methods for their production are known to those skilled in the art.

[0051] Suitable supports also include gas-permeable polymeric supports. The polymer is selected, for example, from polyamides, polyimides, polypyrrolones, polyesters, polysulfones, polymeric organosilicones, fluorine-containing polymers, polyolefins, and copolymers, and blends thereof.

[0052] The membrane device and / or the carrier material a) can, in principle, have any shape suitable for the intended application. The shape of the base area of ​​the membrane device and / or the carrier material can, for example, be polygonal (n-sided with n > 3, e.g., triangular, square, pentagonal, hexagonal, etc.), circular, circular segment-shaped (e.g., semicircular), elliptical, or elliptical segment-shaped. The base area is preferably rectangular or circular. The membrane device can, for example, be designed as a substantially flat disc (plate shape), tubular, honeycomb, or polygonal prism shape. Furthermore, the membrane device can have a support device or be self-supporting. The carrier material can consist of one or more layers, e.g., 2, 3, 4, 5, or more than 5 layers.The layers can each consist of different carrier materials or of identical carrier materials that differ in their composition and / or another physicochemical property, such as porosity or pore size distribution. The individual layers can also be designed as a composite material. Such a composite material can, for example, comprise at least one porous substrate and at least one porous or non-porous carrier material (e.g., a fiber material or a polymeric carrier), as well as optionally at least one binder. Suitable porous substrates include, for example, porous metals, porous ceramic and non-ceramic materials, porous glasses, etc.

[0053] The carrier material can have an asymmetric, especially gradient-shaped, layer structure. For example, the nanoporous carbon-containing layer b) can be arranged on a carrier material consisting of at least two layers that have different porosities. In a gradient-shaped layer structure, for example, the porosity can decrease continuously toward the nanoporous carbon-containing layer.

[0054] Optionally, the support material can comprise at least one inorganic layer. The inorganic layer can, for example, be arranged between the nanoporous carbon-containing layer b) and at least one further support layer. The inorganic layer can, for example, comprise a plurality of discrete particles. These particles preferably have a particle size of at most 1 micrometer, in particular at most 500 nm. The particles in the inorganic layer are selected, for example, from alkaline earth metal oxide particles, transition metal oxide particles, lanthanide metal oxide particles, Group (IVA) metal oxide particles, transition metal particles, metal alloy particles, silicate particles, aluminosilicate particles, zeolite particles, clay mineral particles, and combinations thereof. Particle size analysis can be carried out by laser diffraction according to ISO 13320:2020-01.

[0055] The membrane device according to the invention preferably comprises at least one sheet-like fiber material as component a). In particular, component a) comprises a fiber material selected from nonwovens, woven fabrics, knitted fabrics, papers, and combinations thereof. Suitable fibers for fiber material a) are, in principle, carbon fibers, glass fibers, fibers of organic polymers such as polyolefin, polyester, polyamide, and mixtures thereof. The fibers contained in fiber material a) preferably comprise or consist of carbon fibers (carbon fibers, carbon fibers). Such fiber materials particularly advantageously fulfill the requirements for gas diffusivity, thermal conductivity, etc. The carrier material a) is preferably selected from carbon fiber woven fabrics, carbon fiber papers, and carbon fiber nonwovens.In a particularly preferred embodiment, the carrier material a) comprises at least one carbon fiber nonwoven fabric or the carrier material a) consists of a carbon fiber nonwoven fabric.

[0056] The carbon fibers can be produced in the usual way, with polyacrylonitrile fibers (PAN fibers) preferably being used as the starting material.

[0057] In carbon fiber fabrics, the flat fiber material is produced by interlacing two thread systems: warp and weft. As with textiles, fiber bundles are flexibly but inextricably linked. Oxidized, but not yet carbonized or graphitized PAN fibers are preferably used to produce carbon fiber fabrics. Carbonization or graphitization, to impart electrical conductivity to the flat fiber material, occurs after weaving.

[0058] Oxidized PAN fibers are preferably used to produce carbon fiber paper. These are shredded into fiber fragments in a conventional manner, slurried, and, analogous to papermaking, a fiber web is produced by sieving (decking) and dried. In a preferred embodiment, at least one binder is additionally incorporated into the paper. Suitable binders include, for example, phenolic, furan, polyimide resins, etc. To incorporate the binder, the paper can be impregnated with it, and the binder can then be cured if necessary. After impregnation and curing, the carbon fiber paper is subjected to another carbonization / graphitization process to convert the binder into compounds with improved electrical conductivity. In another suitable embodiment, a filled carbon fiber paper is used to provide the carrier material a).The initial production process is as described above, but instead of introducing a binder and carbonization / graphitization, a filler consisting of a carbon material in a polymer binder is introduced into the still-moist paper. Specifically, a carbon-PTFE filler is used for this purpose.

[0059] This filling increases the thermal and electrical conductivity to such an extent that carbonization / graphitization is no longer necessary.

[0060] Non-oxidized or oxidized PAN fibers can be used to produce carbon fiber nonwovens. In a first preferred embodiment, the fibers are first dry-laid (carded) to form a pile and then consolidated into a nonwoven. This can be done, for example, by hydroentangling, whereby the carbon fibers are oriented, entangled, and thus mechanically stabilized. If necessary, the thickness of the consolidated nonwoven can be calibrated to a desired value. Nonwovens based on non-oxidized PAN fibers are first subjected to oxidation at elevated temperature and in an oxygen atmosphere after web laying and consolidation, followed by carbonization / graphitization in an inert gas atmosphere. Nonwovens based on oxidized PAN fibers are only subjected to carbonization / graphitization after web laying and consolidation.

[0061] In a first specific embodiment, a mechanically bonded fiber material is used as the carrier material a). In another specific embodiment, a nonwoven fabric is used as the fiber material a) into which at least one binder has been incorporated, which is optionally subsequently cured. Suitable binders include phenolic, furan, polyimide resins, etc.

[0062] In a specific embodiment, a nonwoven fabric is used as the carrier material a) into which at least one fluorine-free, high-temperature-resistant polymer has been incorporated as fiber material and / or as binder. The fluorine-free, high-temperature-resistant polymer is then selected from polyaryletherketones, polyphenylene sulfides, polysulfones, polyethersulfones, semi-aromatic (co)polyamides, polyimides, polyamideimides, polyetherimides, and mixtures thereof. The fluorine-free, high-temperature-resistant polymer can be used as a component of the fiber material in addition to or alternatively to at least one carbon fiber material. The fluorine-free, high-temperature-resistant polymer can also be used as a binder. The introduction of the binder can, for example, follow carbonization / graphitization, and the resulting impregnated nonwoven fabric can then be thermally treated again (for drying and / or sintering).

[0063] The flat carrier material a) is preferably a fiber composite material comprising a fiber material that is preferably selected from carbon fiber nonwovens, carbon fiber wovens and mixtures thereof.

[0064] Specifically, the fiber composite material comprises at least one fiber material and, applied thereto and / or incorporated therein, at least one polymeric additive a1) and optionally at least one further additive a2).

[0065] The polymeric additive a1) is preferably selected from fluorine-containing polymers a11), fluorine-free high-temperature-resistant polymers a12), polymers different therefrom a13) and mixtures thereof.

[0066] The mass fraction of the polymeric additive a1) is preferably 0.5 to 50%, preferably 1 to 40%, based on the mass of the fiber material used as carrier material a). In a specific embodiment, the polymeric additive a1) comprises at least one fluorine-containing polymer a11). The mass fraction of the fluorine-containing polymer a11) is then preferably 0.5 to 40%, preferably 1 to 30%, based on the mass of the fiber material used as carrier material a). By adding at least one fluorine-containing polymer a11), the hydrophobicity of the fiber material used as carrier material a) can be increased. This can have a beneficial effect on the transport processes through the membrane device. In principle, the fluorine-containing polymers b1) used as polymeric binders of the nanoporous layer are suitable as fluorine-containing polymers a11).The fluorine-containing polymer a11) is preferably selected from polytetrafluoroethylene (PTFE), tetrafluoroethylene-hexafluoropropylene copolymers (FEP), perfluoroalkoxy polymers (PFA), and mixtures thereof. Perfluoroalkoxy polymers are, for example, copolymers of tetrafluoroethylene (TFE) and perfluoroalkoxyvinyl ethers, such as perfluorovinylpropyl ether. Polytetrafluoroethylene is preferably used as polymer a11). The fiber material can be impregnated with the fluorine-containing polymer a11) using conventional impregnation processes. For this purpose, for example, a PTFE dispersion can be applied in an immersion bath, the solvent evaporated, and the treated fiber material sintered at elevated temperatures of generally at least 300°C.

[0067] In a further specific embodiment, the polymeric additive a1) comprises at least one fluorine-free, high-temperature-resistant polymer a12). The fluorine-free, high-temperature-resistant polymer a12) is then preferably selected from polyaryletherketones, polyphenylene sulfides, polysulfones, polyethersulfones, partially aromatic (co)polyamides, polyimides, polyamideimides, polyetherimides, and mixtures thereof. The mass fraction of the fluorine-containing polymer a12) is then preferably 0.5 to 40%, preferably 1 to 30%, based on the mass of the fiber material used as carrier material a).

[0068] In a specific embodiment, the polymeric additive a1) comprises a mixture of at least one fluorine-containing polymer a11) and at least one fluorine-free, high-temperature-resistant polymer a12). The total mass fraction of the polymers a11) and a12) is then preferably 0.5 to 40%, preferably 1 to 30%, based on the mass of the fiber material used as carrier material a).

[0069] The polymeric additive a1) can comprise at least one further polymer a13) different from a11) and a12). Suitable polymers a13) are, for example, selected from phenolic resins, furan resins, polyimide resins, and mixtures thereof. Specifically, the polymeric additive a1) contains further polymers a13) different from the fluorine-containing polymers a11) and the polymers a12) in a weight fraction of at most 5%, preferably of at most 1%, particularly preferably of at most 0.5%, in particular of at most 0.1%, based on the total weight of the fiber material A), applied thereto and / or incorporated therein. Even more specifically, the fiber material a) contains no additions of further polymers a13) different from the fluorine-containing polymers a11) and the polymers a12).

[0070] The fiber material used as carrier material a) can additionally contain at least one additive a2). Suitable additives include fillers and reinforcing materials, surface-active compounds, adhesion promoters, etc. The additive a2) is preferably selected from metal particles, carbon black, graphite, graphene, carbon nanotubes (CNTs), carbon nanofibers, and mixtures thereof. A specific embodiment of the carbon nanofibers is graphitic carbon nanofibers (GCNFs). The additive a2) particularly preferably comprises carbon black or consists of carbon black. The treatment of the fiber material a) with at least one additive a2) can, for example, be carried out together with the polymeric additive a1).

[0071] The mass fraction of additive a2) is preferably 0 to 80%, particularly preferably 0 to 50%, based on the mass of the fiber material used as carrier material a). In a specific embodiment, additive a2) comprises carbon black or consists of carbon black. In this case, the mass fraction is preferably 0.5 to 45%, particularly preferably 1 to 25%, based on the mass of the fiber material used as carrier material a).

[0072] The fiber material a) preferably has a thickness in the range of 50 to 500 pm, particularly preferably 100 to 400 pm. This thickness refers to the untreated, uncompressed state of the fiber material a), ie, prior to incorporation into a membrane device.

[0073] The fiber material used as carrier material a) can be treated with components a1) and / or a2) using conventional methods. An aqueous dispersion is preferably used to treat the fiber material. Suitable coating and impregnation processes are described in more detail below.

[0074] In a specific embodiment, the fiber material treated with components a1) and / or a2) is subjected to a thermal treatment (drying and / or sintering). The thermal treatment of the fiber material is preferably carried out at a temperature of at least 250°C, particularly preferably at least 300°C, in particular in a range from 300 to 450°C. The thermal treatment can also be carried out after the application of the nanoporous carbon-containing layer b), as described in more detail below.

[0075] Nanoporous carbon-containing layer b) The membrane device according to the invention comprises a two- or multi-layer composite based on a flat, gas-permeable carrier material a) and a nanoporous carbon-containing layer b) on at least one of the surfaces of the carrier material a).

[0076] In particular, the nanoporous layer b) comprises at least one carbon component in a polymeric binder. In addition, at least one additive can be used to produce the nanoporous layer. Suitable additives include, for example, pore formers.

[0077] The carbon component is preferably selected from carbon black, graphite, graphene, carbon nanotubes (CNTs), carbon nanofibers, especially graphitic carbon nanofibers (GCNFs), carbon-containing products from the production of the nanoporous carbon-containing layer b), and mixtures thereof. Carbon black, graphite, or a mixture thereof is preferably used.

[0078] In particular, the polymeric binder contains at least one fluorine-containing polymer b1), preferably selected from polytetrafluoroethylenes, tetrafluoroethylene-hexafluoropropylene copolymers, perfluoroalkoxy polymers, and mixtures thereof. Polytetrafluoroethylene is preferably used as polymer b1).

[0079] Alternatively or additionally, the polymeric binder contains at least one fluorine-free, high-temperature-resistant polymer b2), which is preferably selected from polyaryletherketones, polyphenylene sulfides, polysulfones, polyethersulfones, partially aromatic (co)polyamides, polyimides, polyamideimides, polyetherimides and mixtures thereof.

[0080] In a specific embodiment, the polymeric binder contains at least one polymer b1) and at least one polymer b2), wherein b1) comprises or consists of polytetrafluoroethylene (PTFE) and b2) comprises or consists of a polyetheretherketone (PEEK).

[0081] The polymer b2) is specifically selected from so-called high-performance plastics, which are characterized by properties such as a high glass transition temperature, a high melting temperature, good temperature resistance, good chemical resistance, and good mechanical properties. Preferably, the polymers b2) have a continuous operating temperature (continuous use temperature) of at least 150°C. In particular, the polymers b2) are thermoplastics.

[0082] Preferred polymers b2) are partially aromatic and aromatic polymers. The polymers b2) are preferably selected from polyaryletherketones (PAEK), polyphenylene sulfides (PPS), polysulfones (PSU), polyethersulfones (PES), partially aromatic (co)polyamides (high-temperature polyamides, HTPA), polyimides (PI), polyamideimides (PAI), polyetherimides (PEI), and blends thereof.

[0083] Suitable polymers b2) are also (semi-)aromatic polyesters, such as PET or PBT, polycarbonates (PC) and temperature-resistant melamines, such as melamine foams filled with nanoporous SiO2 aerogels.

[0084] In a preferred embodiment, polymer component b2) comprises at least one polyaryl ether ketone. Specifically, polymer component b2) consists of at least one polyaryl ether ketone. Polyaryl ether ketones (PAEK) are semi-crystalline thermoplastics that have an alternating structure in which each aryl group is followed by a keto group (carbonyl group) or ether group. The proportions of keto and ether groups are variable and can differ in the substitution pattern on the aryl rings. Suitable polyaryl ether ketones b2) are polyether ketones (PEK), polyether ether ketones (PEEK), polyether ketone ketones (PEKK), etc. Preferably, polymer component b2) comprises at least one polyether ether ketone or consists of at least one polyether ether ketone.

[0085] Suitable partially aromatic (co)polyamides b2) are the polymers known as high-temperature polyamides (HTPAs). These are semi-crystalline or amorphous, thermoplastic, partially aromatic polyamides. These preferably contain at least one aromatic dicarboxylic acid as polymerized units, in particular selected from terephthalic acid, isophthalic acid, and mixtures of terephthalic acid and isophthalic acid. Preferred partially aromatic (co)polyamides b2) are selected from PA 6.T, PA 10.T, PA 12.T, PA 6.1, PA 10.1, PA 12.1, PA 6.T / 6.I, PA 6.T / 6, PA 6.T / 10T, PA 10.T / 6.T, PA 6.T / 12.T, PA12.T / 6.T, and mixtures thereof. Another specific embodiment of the polyamides b2) is polyphthalamide (PPA).

[0086] Suitable polyimides b2) are polysuccinimide (PSI), polybismaleimide (PBMI), polyimidesulfone (PISO) and polymethacrylimide (PMI).

[0087] In particular, the polymeric binder contains at least one fluorine-free, high-temperature-resistant polymer b2) and at least one fluorine-containing polymer b1) different therefrom. Preferably, at least one polyetheretherketone is used as polymer b2) and a polytetrafluoroethylene is used as polymer b1).

[0088] To produce the nanoporous layer b), the polymeric binder is preferably used in a weight amount of 0.5 to 50 wt.%, particularly preferably 1.0 to 40 wt.%, in particular 10 to 25 wt.%, based on the total weight of polymeric binders and carbon component.

[0089] The nanoporous carbon-containing layers according to the invention have an advantageous pore structure. It has been found that the use of the polymeric binders described above as component b2) makes it possible to create a proportion of larger pores in the nanoporous layer. The pore size and pore size distribution can also be influenced by the choice of fillers and reinforcing materials. For example, the use of graphite, especially coarse-grained graphite or expandable graphite, generally produces larger pores than the use of carbon black. Furthermore, the total pore volume, the number of pores, and their size distribution can be influenced by the use of pore-forming agents. Suitable pore-forming agents include, for example, commercially available plastic particles, e.g., made of polymethyl methacrylate (PMMA).

[0090] The nanoporous layer preferably has a thickness in the uncompressed state of 5 to 100 micrometers, preferably 10 to 50 micrometers. This thickness refers to the uncompressed state of the nanoporous layer b), ie, before incorporation into a complex gas separation device.

[0091] The membrane device according to the invention preferably has a thickness (total thickness of support material a) and nanoporous layer b)) in the range from 50 to 1000 pm, particularly preferably from 75 to 500 pm. This thickness refers to the uncompressed state of the membrane device, ie, before its installation in a complex gas separation device.

[0092] The determination of the thickness of the flat gas-permeable carrier materials a), the nanoporous carbon-containing layers b) and the membrane device can be carried out according to DIN 53855-1:1993-08 "Determination of the thickness of textile fabrics".

[0093] The determination of the mass per unit area (also called basis weight) in g / m 2 can be carried out according to EN 29073-1 :1992.

[0094] Microporous layer a / b)

[0095] In a specific embodiment, the membrane device according to the invention comprises a three- or multi-layer composite based on a flat, gas-permeable carrier material a), a microporous layer a / b) on at least one of the surfaces of the carrier material a), and a nanoporous carbon-containing layer b) on the microporous layer a / b). In particular, the microporous layer a / b) comprises conductive particles in a matrix of a polymeric binder. The conductive particles are preferably selected from conductive carbon particles, in particular carbon black, graphite, graphene, carbon nanotubes (CNTs), carbon nanofibers, and mixtures thereof. Preference is given to using carbon black, graphite, or a mixture thereof.

[0096] Preferably, the polymeric binder of the microporous layer a / b) comprises at least one polymer selected from fluorine-containing polymers, fluorine-free, high-temperature-resistant polymers, polymers different therefrom, and mixtures thereof.

[0097] In particular, the polymeric binder of the microporous layer a / b) contains at least one fluorine-containing polymer. Suitable fluorine-containing polymers are the fluorine-containing polymers b1) previously described for forming the nanoporous layer b), to which reference is made here in their entirety. In particular, the polymeric binder of the microporous layer a / b) contains at least one fluorine-containing polymer b1), preferably selected from polytetrafluoroethylenes, tetrafluoroethylene-hexafluoropropylene copolymers, perfluoroalkoxy polymers, and mixtures thereof. Polytetrafluoroethylene is preferably used as the polymeric binder of the microporous layer a / b).

[0098] Alternatively or additionally, the polymeric binder of the microporous layer a / b) contains at least one fluorine-free, high-temperature-resistant polymer. Suitable fluorine-free, high-temperature-resistant polymers are the polymers b2) previously described for forming the nanoporous layer b), which are incorporated herein by reference. In particular, the polymeric binder of the microporous layer a / b) contains at least one fluorine-containing polymer b2), which is preferably selected from polyaryletherketones, polyphenylene sulfides, polysulfones, polyethersulfones, partially aromatic (co)polyamides, polyimides, polyamideimides, polyetherimides, and mixtures thereof.

[0099] In a specific embodiment, the polymeric binder of the microporous layer a / b) contains at least one polymer b1) and at least one polymer b2), wherein b1) comprises or consists of polytetrafluoroethylene (PTFE) and b2) comprises or consists of a polyetheretherketone (PEEK).

[0100] To produce the microporous layer b), the polymeric binder is preferably used in a weight amount of 0.5 to 50 wt. %, particularly preferably 1.0 to 40 wt. %, in particular 10 to 25 wt. %, based on the total weight of polymeric binders and conductive particles. The microporous layer a / b) can be applied to the carrier material a) in various ways. While spraying, screen printing or Meyer rod processes are often used in discontinuous production, doctor blade, slot die and gravure roll processes are preferably used for continuous coating. Finally, a thermal treatment can take place, e.g. in a drying and sintering furnace. This can initially involve drying at a temperature of 100 to 200°C, followed optionally by sintering at a temperature of 300 to 500°C.

[0101] In contrast to the macroporous fiber material a) and the nanoporous layer b), the MPL a / b) is microporous. The average pore diameter of the microporous layer a / b) is preferably in a range from 5 nm to 10 pm, particularly preferably in a range from 7 nm to 1 pm, in particular in a range from 10 nm to 900 nm.

[0102] The determination of porosity and pore size distribution of the microporous layer a / b) can be carried out using mercury porosimetry, as described in DIN ISO 15901-1:2019-03 and ISO 15901-1:2016- Part 1: Mercury porosimetry.

[0103] In a special embodiment, the microporous layer a / b) is free of added transition metal compounds.

[0104] In a special embodiment, the microporous layer a / b) is free of added fibers, in particular free of added carbon fibers.

[0105] The microporous layer (a / b) preferably has a thickness in the range of 5 to 150 pm, particularly preferably 10 to 100 pm. This thickness refers to the uncompressed state of the microporous layer (a / b), ie, prior to incorporation into a membrane device.

[0106] Manufacturing process

[0107] Another object of the invention is a method for producing a membrane device, in which i) a flat gas-permeable support material a) is provided, ii) the support material provided in step i) is coated with a coating agent to form a nanoporous carbon-containing layer, wherein the pores have an average pore size in the range of 0.3 to 2 nm and a pore size distribution of 0.1 to 5.0 nm, both preferably determined by means of permporosimetry.The invention further provides a process for producing a membrane device, in which i) a flat gas-permeable support material a) is provided, ii-a) the support material provided in step i) is coated with a coating agent to form a microporous layer, ii-b) the coated support material obtained in step ii-a) is coated with a coating agent to form a nanoporous carbon-containing layer, wherein the pores have an average pore size in the range of 0.3 to 2 nm and a pore size distribution of 0.1 to 5.0 nm.

[0108] The sheet-like, gas-permeable carrier material a) provided in step i) of the previously described method can have one or more layers. Reference is made in this regard to the above statements regarding suitable carrier materials. In a preferred embodiment, the carrier material a) comprises at least one sheet-like fiber material. In a specific embodiment, the nanoporous carbon-containing layer b) is applied to a sheet-like fiber material, even in the case of a multilayer structure of the carrier material a). The sheet-like fiber material is preferably selected from nonwovens, woven fabrics, knitted fabrics, papers, and combinations thereof. With regard to suitable and preferred fiber materials, reference is made in full to the above statements. The fiber materials can be treated with conventional binders and / or additives before use in step ii), as also described above.Conventional impregnation processes can be used for this purpose. The optionally treated fiber material can be subjected to thermal treatment (drying and / or sintering) before use in step ii).

[0109] The carrier material a), specifically a fiber material, provided in step i), can optionally be coated with a coating agent in steps a / b) to form a microporous layer. The possible procedure for applying the microporous layer a / b) to the carrier material a) has already been described above.

[0110] In a first embodiment, the carrier material a) provided in step i), specifically a fiber material, is coated in step ii) with a coating agent to form a nanoporous layer b). Preferably, the carrier material is coated and / or impregnated with an aqueous composition containing at least one carbon component, a polymeric binder, and optionally further additives. All components for forming the nanoporous layer can be used in a single composition for coating the carrier material a). It is also possible to coat the carrier material a) with two or more coating agents, each containing one or more components. With regard to suitable and preferred polymers b1) and b2), reference is made in full to the above statements.

[0111] In a second embodiment, the carrier material a), specifically a fiber material, provided in step i) is coated in step ii-a) with a coating agent to form a microporous layer and subsequently coated in step ii-b) with a coating agent to form a nanoporous layer b).

[0112] The nanoporous layer can be applied in step ii) or in steps ii-b) in various ways. While spraying, screen printing, or Meyer rod processes are often used in discontinuous production, doctor blade, slot die, and gravure roller processes are preferred for continuous coating. The layer thickness of the nanoporous layer and the penetration depth of the coating agent into the substrate can be influenced by the coating process parameters and the viscosity of the coating agent.

[0113] Finally, a thermal treatment can be carried out, e.g., in a drying and sintering furnace. For example, drying can first be carried out at a temperature of 100 to 200°C, followed by sintering at a temperature of 300 to 500°C. The thermal treatment in step ii) preferably takes place at a temperature at which the polymeric binder is partially or completely molten.

[0114] A preferred embodiment is a method in which

[0115] 11) provides a fiber composition comprising carbon fibers and / or precursors of carbon fibers as a flat, gas-permeable carrier material,

[0116] 12) subjecting the fibre composition provided in step i1) to a process for producing a nonwoven fabric,

[0117] 13) if the fiber composition used in step i1) comprises carbon fiber precursors, subjecting the nonwoven fabric to pyrolysis at a temperature of at least 1000 °C, ii) coating the nonwoven fabric obtained in step i2) or i3) with a nanoporous layer. Separation of gas mixtures

[0118] For separation, a starting gas mixture can be passed through one or more membrane devices. Multiple membrane devices can be arranged in series or parallel with respect to the gas flow direction. Combinations of series and parallel membrane devices are also possible. Furthermore, gas streams can be partially or completely recycled to an upstream membrane device in the sense of a recirculation circuit. The series connection of two or more membrane devices preferably serves to increase selectivity. A parallel connection preferably serves to increase throughput and enables easier maintenance and / or the replacement of membrane devices during operation.

[0119] The membrane device(s) used for gas separation comprise a device for supplying a starting gas mixture and a device for removing at least one gas stream obtained during the gas separation.

[0120] The invention further relates to a membrane device as defined above or obtainable by a process as defined above. In this context, the term membrane device also encompasses an arrangement of two or more individual membrane devices used for gas separation.

[0121] The invention further provides a process for the at least partial separation of at least one gas component from a gas mixture, in which a starting gas mixture is subjected to a separation into at least one retentate stream and at least one permeate stream in at least one membrane separation stage, wherein the membrane separation stage comprises at least one membrane device as defined above or obtainable by a process as defined above.

[0122] A further object of the invention is the use of a membrane device as defined above or obtainable by a process as defined above for selective gas separation, preferably for selective separation of a gas mixture from large-scale hydrogen production, in particular for selective separation of a gas mixture containing hydrogen and at least one Ci-Cu hydrocarbon, preferably at least one Ci-Ce hydrocarbon.

[0123] The following examples are intended to illustrate the invention without limiting it thereto.

[0124] Example 1: Production of a membrane device from a carbon fiber nonwoven as a carrier material and a nanoporous carbon-containing layer

[0125] To produce a base nonwoven, a dry-laid fiber web made of 100% oxidized polyacrylonitrile fibers was laid down on a carding machine. The fiber web was fed to a bonding unit, where the fibers were swirled and entangled on both sides using high-energy water jets at pressures of approximately 100 bar in the first stage and approximately 200 bar in a second stage. The nonwoven was then subjected to a thickness calibration, reducing the thickness of the hydroentangled nonwoven to 0.25 mm. The nonwoven was then fed to a carbonization unit, where carbonization took place under a nitrogen atmosphere at approximately 1000 to 1400°C. The result was a nonwoven made of 100% carbon fibers with a basis weight of 65 g / m². 2To finish the nonwoven fabric, an aqueous impregnation composition was mixed containing 70% carbon black and 30% polytetrafluoroethylene (PTFE) based on the solids. The finishing was carried out by padding with the aqueous dispersion at 15% finish weight based on the mass of the nonwoven substrate (corresponding to 10 g / m 2 ). This was followed by drying for 5 minutes at 160°C and sintering for 10 minutes at 400°C. A coating was then applied to the resulting substrate to produce the flat nanoporous layer. The composition of the coating agent for producing the nanoporous layer consisted of 2% PTFE, 2% PEEK, 0.11% surface-active additives, and 11% nanoporous carbon. The fiber material was then dried at 160°C and sintered at 400°C. The resulting loading of the nanoporous layer was 35 g / m 2 .

[0126] The achieved permeabilities and selectivities of the material from Example 1 are shown in Table 1.

[0127] Table 1

[0128] Example 2: Fabrication of a membrane device from a carbon fiber nonwoven fabric as a carrier material, a microporous layer and a nanoporous carbonaceous layer

[0129] To produce a base nonwoven, a dry-laid fiber web made of 100% oxidized polyacrylonitrile fibers was laid down on a carding machine. The fiber web was fed to a bonding unit, where the fibers were swirled and entangled on both sides using high-energy water jets at pressures of approximately 100 bar in the first stage and approximately 200 bar in a second stage. The nonwoven was then subjected to a thickness calibration, reducing the thickness of the hydroentangled nonwoven to 0.25 mm. The nonwoven was then fed to a carbonization unit, where carbonization took place under a nitrogen atmosphere at approximately 1000 to 1400°C. The result was a nonwoven made of 100% carbon fibers with a basis weight of 65 g / m². 2To finish the nonwoven fabric, an aqueous impregnation composition was mixed containing 70% carbon black and 30% polytetrafluoroethylene (PTFE) based on the solids. The finishing was carried out by padding with the aqueous dispersion at 15% finish weight based on the mass of the nonwoven substrate (corresponding to 10 g / m 2 ). This was followed by drying for 5 minutes at 160°C and sintering for 10 minutes at 400°C. A coating was then applied to the resulting substrate to produce the flat microporous layer. The composition of the coating agent for producing the microporous layer consisted of 10% PTFE, 10% PEEK, and 80% carbon black. The fiber material was then dried at 160°C and sintered at 400°C. The resulting loading of the microporous layer was 23 g / m². 2A coating was then applied to the microporous layer to create the nanoporous layer. The composition of the coating agent for the nanoporous layer consisted of 2% PTFE, 2% PEEK, 11% nanoporous carbon, and 0.08% surface-active additives in distilled water. The substrate was then dried at 160°C and sintered at 400°C. The resulting loading of the nanoporous layer was 15 g / m². 2 .

[0130] The achieved permeabilities and selectivities of the material from Example 2 are shown in Table 2.

[0131] Table 2

Claims

Patent claims 1 . A membrane device for selective gas separation, comprising a) a flat, gas-permeable support material and b) a nanoporous carbonaceous layer on at least one of the surfaces of the support material, wherein the nanoporous layer comprises at least one carbon component in a polymeric binder and wherein the nanoporous carbonaceous layer has an average pore size in the range of 0.3 to 2.0 nm and a pore size distribution in the range of 0.1 to 5.0 nm.

2. A membrane device for selective gas separation, comprising a) a flat gas-permeable support material, a / b) a microporous layer on at least one of the surfaces of the support material, b) a nanoporous carbon-containing layer on the microporous layer a / b), wherein the nanoporous layer comprises at least one carbon component in a polymeric binder and wherein the nanoporous carbon-containing layer has an average pore size in the range of 0.3 to 2.0 nm and a pore size distribution in the range of 0.1 to 5.0 nm.

3. Membrane device according to claim 1 or 2, wherein the nanoporous carbon-containing layer b) has an average pore size in the range of 0.4 to 1.5 nm, preferably 0.5 to 1.3 nm.

4. Membrane device according to claim 1 or 2 or 3, wherein the nanoporous carbon-containing layer b) has a layer thickness in the range of 0.5 to 500 pm, preferably from 1.0 to 10 pm.

5. Membrane device according to one of the preceding claims, wherein the nanoporous carbonaceous layer b) has a porosity, determined as the ratio of the volume fraction of the pores to the total volume of the nanoporous carbonaceous layer, in the range from 20 to 80%, preferably from 60 to 70%.

6. Membrane device according to one of the preceding claims, wherein the sheet-like gas-permeable support material a) is selected from fiber materials, porous metallic supports, porous ceramic and non-ceramic supports, monolithic supports, gas-permeable polymeric supports and combinations thereof.

7. Membrane device according to one of the preceding claims, wherein the carrier material a) comprises at least one sheet-like fiber material or consists of at least one sheet-like fiber material, wherein the carrier material is preferably selected from nonwovens, wovens, knitted fabrics, papers and combinations thereof.

8. Membrane device according to claim 7, wherein the sheet-like fiber material a) is selected from carbon fiber nonwovens, carbon fiber wovens, carbon fiber papers and combinations thereof.

9. Membrane device according to one of the preceding claims, wherein the nanoporous carbonaceous layer b) comprises at least one carbon component selected from carbon black, graphite, graphene, carbon nanotubes (CNT), carbon nanofibers, especially graphitic carbon nanofibers (GCNF), carbonaceous products from the production of the nanoporous carbonaceous layer b) and mixtures thereof.

10. Membrane device according to one of the preceding claims, wherein the nanoporous carbonaceous layer b) comprises a polymeric binder containing at least one fluorine-containing polymer b1) and / or at least one fluorine-free, high-temperature-resistant polymer b2).

11. Membrane device according to claim 10, wherein the nanoporous carbonaceous layer b) comprises a polymeric binder containing at least one fluorine-containing polymer b1) selected from polytetrafluoroethylene, tetrafluoroethylene-hexafluoropropylene copolymers, perfluoroalkoxy polymers, and mixtures thereof.

12. Membrane device according to claim 10 or 11, wherein the nanoporous carbonaceous layer b) comprises a polymeric binder containing at least one fluorine-free, high-temperature-resistant polymer b2) selected from polyaryletherketones, polyphenylene sulfides, polysulfones, polyethersulfones, partially aromatic (co)polyamides, polyimides, polyamideimides, polyetherimides and mixtures thereof.

13. Membrane device according to one of the preceding claims, which comprises a microporous layer a / b), wherein the average pore diameter of the microporous layer a / b) is in a range from 5 nm to 10 pm, preferably in a range from 7 nm to 1 pm, in particular in a range from 10 nm to 900 nm.

14. Membrane device according to one of the preceding claims, which comprises a microporous layer a / b), wherein the microporous layer a / b) is free of added transition metal compounds.

15. Membrane device according to one of the preceding claims, which comprises a microporous layer a / b), wherein the microporous layer a / b) is free of added fibers, in particular free of added carbon fibers.

16. Membrane device according to one of the preceding claims, comprising a device for supplying a starting gas mixture and a device for removing at least one gas stream obtained during the gas separation.

17. A process for producing a membrane device, comprising i) providing a flat, gas-permeable support material a), ii) coating the support material provided in step i) with a coating agent to form a nanoporous carbon-containing layer, wherein the pores have an average pore size in the range of 0.3 to 2 nm and a pore size distribution of 0.1 to 5.0 nm.

18. A process for producing a membrane device, comprising the steps of: i) providing a flat, gas-permeable support material a), ii-a) coating the support material provided in step i) with a coating agent to form a microporous layer, ii-b) coating the coated support material obtained in step ii-a) with a coating agent to form a nanoporous carbon-containing layer, the pores having an average pore size in the range from 0.3 to 2 nm and a pore size distribution of 0.1 to 5.0 nm.

19. The method according to claim 17, wherein 11) provides a fiber composition comprising carbon fibers and / or precursors of carbon fibers as a flat, gas-permeable carrier material, 12) subjecting the fibre composition provided in step i1) to a process for producing a nonwoven fabric, 13) if the fiber composition used in step i1) comprises precursors of carbon fibers, subjecting the nonwoven fabric to pyrolysis at a temperature of at least 1000 °C, ii) coating the nonwoven fabric obtained in step i2) or i3) with a nanoporous layer.

20. A membrane device obtainable by a process as defined in any one of claims 17 to 19.

21. A process for the at least partial separation of at least one gas component from a gas mixture, in which a starting gas mixture is subjected to a separation into at least one retentate stream and at least one permeate stream in at least one membrane separation stage, wherein the membrane separation stage comprises at least one membrane device as defined in any one of claims 1 to 16 or obtainable by a process as defined in any one of claims 17 to 19.

22. The process according to claim 21, wherein the starting gas mixture used is a gas mixture from large-scale hydrogen production, preferably from hydrogen production by methane steam reforming (SMR), from the water gas shift reaction, a synthesis gas from coal gasification, from petroleum, from carbon-containing waste or from biomass, or a gas mixture from the partial oxidation of hydrocarbons.

23. The process according to claim 21 or 22, wherein the starting gas mixture comprises hydrogen and at least one Ci-Cu hydrocarbon, preferably at least one Ci-C e -hydrocarbon, in particular selected from CH4, C2H e , C3H8 and C4H10.

24. The process according to claim 23, wherein the starting gas mixture additionally contains at least one further gas component, preferably selected from CO, CO2, N2 and mixtures thereof.

25. Use of a membrane device as defined in any one of claims 1 to 16, or obtainable by a process as defined in any one of claims 17 to 19, for selective gas separation, preferably for selectively separating a gas mixture from large-scale hydrogen production, in particular for selectively separating a gas mixture comprising hydrogen and at least one Ci-Cu hydrocarbon, preferably at least one Ci-C e -hydrocarbon, contains.

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