Low pressure diffusion controlled hydrogen storage

Abstract

The use of a hydrogen storage material for passive pressure regulation in a gas transport system for hydrogen-containing gas or for hydrogen storage and passive pressure regulation in a gas storage system for hydrogen is described, wherein the hydrogen storage material is formed from hydrogen-storing metal hydride embedded in a hydrogen-permeable polymer matrix.

Description

[0001] The invention relates to the use of a hydrogen storage material based on metal hydride for passive pressure regulation in a gas transport system for hydrogen-containing gas or for hydrogen storage and passive pressure regulation in a gas storage system for hydrogen.

[0002] Hydrogen is typically stored in tanks at pressures up to 700 bar. For home use, hydrogen storage systems exist that can absorb hydrogen produced, for example, through electrolysis, and release it later, such as during the winter. However, current hydrogen storage systems are very maintenance-intensive because the hydrogen is compressed and stored at high pressures of up to 300 bar in gas cylinders. The technology of compression and storage in gas cylinders also makes such systems very expensive.

[0003] Solid-state storage systems have also been used for hydrogen storage for some time now, for which metal hydrides are particularly suitable, as they can reversibly absorb and release hydrogen depending on the prevailing pressure. More recently, so-called reactive hydride composites (RHCs) have been developed that are well suited as hydrogen storage materials. Such RHCs are described, for example, in C. Abetz et al., Adv. Mater. Technol., Reactive Hydride Composite Confined in a Polymer Matrix: New Insights into the Desorption and Absorption of Hydrogen in a Storage Material with High Cycling Stability, 2101584, 2022, DOI: 10.1002 / admt.202101584.

[0004] Suitable solid storage systems are constructed from rigid plates or foam structures, which are usually based on metal, thermosets or thermoplastics with low elongation at break and possess low flexibility.

[0005] The transport of gases over long distances is accomplished via pipeline networks, known as gas transport systems, particularly for natural gas. Compressor stations ensure a constant flow of gas in long-distance pipelines. These stations maintain the gas pressure every 80 to 160 kilometers in long-distance gas pipelines, which can reach up to 200 bar in steel pipelines. When natural gas is distributed to regional distribution networks, the gas pressure typically ranges between 1 and 70 bar. The gas pressure in local gas pipelines at the municipal level is generally below 1 bar.

[0006] Extensive pipeline networks exist for natural gas, for example, but pipeline networks for hydrogen are also being developed. The conversion of natural gas networks for hydrogen transport is also being examined. Some natural gas pipeline networks are already in operation, in which hydrogen is blended with the natural gas. The proportion of hydrogen in such natural gas-hydrogen mixtures can be up to 20%.

[0007] Particularly in the current natural gas / hydrogen network, which operates between 1 and 70 bar, pressure spikes can occur due to compressor operation or expansion processes. Such pressure spikes are highly undesirable, as they can damage the pipeline system. Therefore, pressure dampers with overpressure valves are typically installed in the pipeline system. However, these mechanical systems are themselves prone to damage and often react too slowly to very short-term pressure surges. Similar problems with pressure spikes also exist in hydrogen gas storage systems.

[0008] The object of the present invention is to overcome the disadvantages of the prior art described above. In particular, the object of the invention was to provide a means for avoiding or reducing pressure peaks in gas transport systems for hydrogen-containing gases and also in gas storage systems for hydrogen, whereby the use of mechanical systems such as pressure relief valves is to be at least partially avoided. Furthermore, the object was to provide a system for hydrogen storage at low pressures. In particular, a flexible design of the geometric shape of the hydrogen storage device should be enabled.

[0009] It was found that this could be solved by using a hydrogen storage material formed from metal hydride embedded in a hydrogen-permeable polymer matrix.

[0010] The invention thus relates to the use of a hydrogen storage material for passive pressure regulation in a gas transport system for hydrogen-containing gas or for hydrogen storage and passive pressure regulation in a gas storage system for hydrogen, wherein the hydrogen storage material is formed from metal hydride embedded in a hydrogen-permeable polymer matrix.

[0011] The hydrogen storage material used in gas transport systems can provide short-term hydrogen storage, enabling passive pressure adjustment that avoids or at least reduces pressure spikes. When pressure spikes occur, the appropriately configured hydrogen storage material is automatically charged with hydrogen from the gas stream, reducing the pressure in the gas transport system. Once the pressure in the gas transport system has normalized, the hydrogen storage material releases the hydrogen and is available for recharging. The same principle applies to hydrogen gas storage systems.

[0012] Particularly in the current natural gas / hydrogen network, which operates between 1 and 70 bar, the use of the hydrogen storage material according to the invention can compensate for pressure peaks resulting from compressor start-ups or expansion processes. Furthermore, hydrogen can be selectively stored and separated, while other gases such as hydrocarbons cannot be stored.

[0013] Furthermore, the hydrogen storage material according to the invention can be used in a gas storage system for hydrogen, making it possible to store hydrogen at low pressure and then for extended periods, with the hydrogen storage material simultaneously acting as a passive pressure regulator. The lower pressure thus also reduces the energy consumption required for compression. The hydrogen storage material used according to the invention can be produced in various geometric shapes and is not necessarily bound to a gas pressure vessel.

[0014] The following is a summary of some advantages of the use of the hydrogen storage material according to the invention: Decentralized, customized hydrogen storage systems; passive pressure regulation (energy saving); recyclable design; gas separation possible; increased operational safety

[0015] The hydrogen storage material used according to the invention can be employed in gas transport systems for hydrogen-containing gas or gas storage systems for hydrogen, e.g., in the mobility sector, in vehicles, particularly automobiles, in turbo pump hoses, or for industrial applications. The hydrogen storage material's design allows for a compact construction. It also offers further advantages, such as passive pressure regulation, sustainability through passive pumping processes, and the provision of a safety-relevant technology. Furthermore, damage to the hydrogen storage material does not result in explosive decompression, but rather in a controlled (diffusion-driven) release of the hydrogen, which significantly increases the safety of the systems.

[0016] The invention is explained in detail below.

[0017] The hydrogen storage material used according to the invention is suitable as a diffusion-controlled hydrogen storage system. It can be used as a short-term storage medium for hydrogen for passive pressure regulation in gas transport systems or as a low-pressure long-term storage medium for hydrogen with passive pressure regulation in gas storage systems.

[0018] The gas transport system can be a pipeline system for hydrogen-containing gases. The gas transport system and the gas storage system can include a pipe, a plastic hose, or another pressurized gas container, such as a pressure-resistant vessel like a compressed gas cylinder. Gases can be stored or transported under pressure within this pressurized gas container. In addition to the pressurized gas container, the gas transport system and the gas storage system can include supply and return lines for hydrogen or hydrogen-containing gases, a compressor unit, and, if necessary, a heating device. The gas transport or gas storage system may also include a heating device. Pure plastic hoses are generally not suitable for higher pressures and may need to be reinforced with a strengthening layer.

[0019] The hydrogen-containing gas can be hydrogen or a mixture of hydrogen and at least one other gas. Such a mixture is preferably a mixture of natural gas and hydrogen. In a mixture of hydrogen and at least one other gas, the proportion of hydrogen can be, for example, at least 1% by volume, preferably at least 3% by volume. The proportion of hydrogen in the natural gas / hydrogen mixture can be, for example, 1 to 30% by volume, preferably 3 to 20% by volume.

[0020] According to the invention, a hydrogen storage material is used for passive pressure regulation in a gas transport system for hydrogen-containing gas, or for hydrogen storage and passive pressure regulation in a gas storage system for hydrogen. It is understood that the hydrogen storage material is arranged within the gas transport system so that it can come into contact with the hydrogen-containing gas. It is further understood that the hydrogen storage material is arranged within the gas storage system so that it can come into contact with the hydrogen. Through passive pressure regulation, pressure spikes in the system can be avoided or reduced by the hydrogen storage material automatically absorbing hydrogen or more hydrogen when pressure spikes occur, thereby reducing the pressure. Since the pressure regulation is passive, the pressure is regulated virtually instantaneously.Mechanical systems for pressure equalization can be avoided or reduced.

[0021] The hydrogen storage material consists of a metal hydride embedded in a hydrogen-permeable polymer matrix. Conventional metal hydrides can be used, which can reversibly absorb and release hydrogen depending on the hydrogen partial pressure. Hydrogen is absorbed above a certain partial pressure, while below this partial pressure, the hydrogen is released from the storage material, a process that can be accelerated by heating. In this way, reversible hydrogen charging and discharging cycles can be initiated by changing the hydrogen partial pressure.

[0022] When gaseous hydrogen is absorbed into the hydrogen storage material, a chemical reaction usually takes place, forming metal-hydride bonds, which are broken again when the hydrogen is released, resulting in the regeneration of gaseous hydrogen.

[0023] The specific hydrogen partial pressure at which the hydrogen storage material can absorb hydrogen depends primarily on the type of metal hydride. The kinetics of hydrogen exchange also depend on the type of polymer in the polymer matrix. Therefore, by selecting the appropriate metal hydride and / or polymer, the resulting hydrogen partial pressure at which hydrogen is stored can be tailored to the specific requirements of the hydrogen storage material.

[0024] The metal hydride can be stoichiometric or non-stoichiometric. It can be selected from simple metal hydrides, complex metal hydrides, or reactive hydride composites (RHCs). The metal hydride used significantly influences the partial pressure at which hydrogen is absorbed or released. The choice of polymer for the polymer matrix can be used to control the rate of hydrogen absorption.

[0025] Suitable simple metal hydrides include alkali metal hydrides and alkaline earth metal hydrides. Good examples are magnesium hydride (MgH₂) (melting point approx. 280 °C) and lithium hydride (LiH₂).

[0026] Complex metal hydrides are salts in which the anions contain hydrides. The metal is preferably an alkali metal or an alkaline earth metal, such as Li, Na, Mg, or Ca. However, other metals, such as Al, Ti, or Zr, are also conceivable. The anion is preferably a boranate (BH₄) or alanate (AlH₄), particularly a boranate. Boranates in compounds are also simply referred to as borohydride. Alanates in compounds are also simply referred to as aluminum hydride.

[0027] The complex metal hydride is preferably selected from metal boranates or metal borohydrides or metal alanates or metal aluminum hydrides, wherein the metal is advantageously an alkali metal or an alkaline earth metal, such as Li, Na, Mg, or Ca. Specific examples of suitable complex metal hydrides are lithium borohydride, sodium borohydride, magnesium borohydride, or sodium aluminum hydride.

[0028] In a particularly preferred embodiment, reactive hydride composites are used as the metal hydride. Reactive hydride composites (RHCs) have recently been developed and investigated as hydrogen storage materials. RHCs are typically composites of two or more metal hydrides, for example, a combination of a simple metal hydride and a complex metal hydride. Amide-based metal hydride systems, which are composites of at least one metal amide and at least one metal hydride, are also generally referred to as RHCs, as is the case in the present application.

[0029] RHCs also preferably contain an alkali metal or an alkaline earth metal, such as Li, Na, Mg or Ca.

[0030] Metal hydrides, particularly RHCs based on at least two metal hydrides or on at least one metal amide and at least one metal hydride, are used. Preferred specific RHC systems are those based on Mg(NH₂)₂-LiH, Mg(NH₂)₂-LiH-LiBH₄, LiBH₄-MgH₂, or Ca(BH₄)₂-MgH₂, with Mg(NH₂)₂-LiH-LiBH₄ being particularly preferred.

[0031] The RHC system based on magnesium amide and lithium hydride (Mg(NH₂)₂-LiH) can have the following stoichiometry: 2 Mg(NH₂)₂ + 4 LiH. The three-component RHC system based on magnesium amide, lithium hydride, and lithium boranate (Mg(NH₂)₂-LiH-LiBH₄) can have a variable proportion of lithium boranate, e.g., 6 Mg(NH₂)₂ + 9 LiH + x LiBH₄. This allows the system's properties to be tailored, e.g., with regard to kinetic and thermodynamic properties or hydrogen storage function. For example, a Mg(NH₂)₂-LiH-LiBH₄ system can constantly absorb hydrogen at a pressure above 50 bar and release it again at a lower pressure.

[0032] The metal hydride used should be stable at temperatures up to at least 150°C. Other systems commonly used as metal hydride storage materials are ammonium borane and lithium aluminum hydride. However, the use of ammonium borane and lithium aluminum hydride is generally avoided because these compounds have a decomposition point below 150°C and would therefore become partially inactive when embedded in the polymer matrix.

[0033] Since most metal hydrides have a melting point above 300 °C, these compounds should be in powder form. Therefore, the metal hydride is preferably used in particulate form. The particulate metal hydride preferably has a particle size of 0.1 to 500 µm, more preferably 0.1 to 250 µm, and more preferably 0.1 to 50 µm. The particle size can be determined, for example, according to DIN 53206, D90, mass distribution, or diameter according to ISO 13320:2020.

[0034] The metal hydride, in particular the particulate metal hydride, is embedded in a hydrogen-permeable polymer matrix in the hydrogen storage material used according to the invention. The polymer matrix is ​​hydrogen-permeable, meaning that it is sufficiently permeable to molecular gaseous hydrogen to allow the hydrogen to diffuse through the matrix to the embedded metal hydride. Conversely, the hydrogen released by the metal hydride can diffuse out through the matrix. For a hydrogen-permeable polymer matrix, polymers with sufficient hydrogen permeability are used. The rate of hydrogen uptake can be controlled by selecting the polymer for the polymer matrix and thus the permeability of the matrix to hydrogen.

[0035] The polymer for the polymer matrix can be, for example, an elastomer, a thermoplastic, or a thermoplastic elastomer (TPE). The polymer for the polymer matrix can be a single polymer, which may be a homopolymer or a copolymer, or a blend of two or more polymers. The polymer(s) preferably exhibit low density, a high amorphous content, and a low glass transition temperature.

[0036] The polymer matrix preferably has a hydrogen gas permeability coefficient of at least 1 × 10⁻⁹ mol H₂ / (m·s·MPa), measured according to ISO 151051:2017 at 30°C. Unless otherwise specified, hydrogen gas permeability coefficient values ​​refer to this measurement method. Such polymers are known from the prior art. The polymer matrix preferably has a hydrogen gas permeability coefficient of at least 4 × 10⁻⁹ mol H₂ / (m·s·MPa), measured according to ISO 151051:2017 at 30°C.

[0037] Preferred examples of suitable polymers for the polymer matrix are selected from polypropylene (PP), low-density polyethylene (LDPE), perfluoroalkoxy polymer (PFA), polystyrene (PS), acrylonitrile butadiene styrene copolymer (ABS), styrene butadiene styrene copolymer (SBS), styrene ethylene butylene styrene block copolymer (SEBS), styrene block copolymer (SBC), chlorosulfonated polyethylene (CSM), chloroprene, silicones, fluororubber (FPM or FKM), ethylene propylene diene monomer (EPDM), or a combination thereof. PP and SEBS are particularly suitable polymers due to their combination of low solubility and high hydrogen diffusion. Among fluoropolymers, fluoroelastomers generally do not exhibit good barrier properties against hydrogen, while fluorothermoplastics do.

[0038] The following table lists values ​​for the permeability coefficient and (for thermoplastics) melting points of some suitable polymers. For practical reasons, the melting point of the polymer used should preferably be below 315 °C, ideally below 300 °C. polymer H₂ permeability coefficient (30°C) [mol H₂ / (m·s·MPa)] Melting point PP 14*10 -9< 160°C ... 180°C LDPE 3,3*10 -9< 120°C PFA 4,6*10 -9< 305°C PS 7,6*10 -9< 240°C ... 270°C ABS 110°C SBS 150°C ... 205°C SEBS* 22*10 -9< SBC 150°C ... 210°C CSM 3,7*10 -9< Chloropren 2*10 -9< * Kraton ®< FG of Kraton

[0039] The polymer of the polymer matrix preferably has an amorphous phase content of at least 40%, preferably at least 80%. This improves the permeability to hydrogen.

[0040] The weight ratio of polymer of the polymer matrix to metal hydride (P:M) in the hydrogen storage material can vary widely and is, for example, in the range of 1:4 to 49:1, preferably 1:3 to 9:1, more preferably 1:3 to 1:1.

[0041] In particular, the incorporation of metal hydride into the polymer matrix allows these storage compounds to be stabilized within the matrix. The hydrogen storage material is preferably in the form of a flexible component. The hydrogen storage material according to the invention can be produced in various geometric shapes and is not necessarily bound to a pressurized gas body.

[0042] In addition to the metal hydride, the polymer matrix may also contain one or more common additives, such as fillers, reinforcing agents, antioxidants, plasticizers, impact modifiers, adhesion promoters, stabilizers, flame retardants, and / or colorants. Plasticizers and / or impact modifiers are advantageous because these additives can also improve the permeability of the polymer matrix to hydrogen.

[0043] In one embodiment, the hydrogen storage material can contain zeolites as hydrogen absorbers in the polymer matrix, in addition to the metal hydride. In this way, molecular hydrogen molecules, as well as hydrides, can be stored in the hydrogen storage material.

[0044] The hydrogen storage material can be in the form of, for example, a coating, a film, at least one layer in a multilayer composite, a molded part or part of a molded part, wherein the hydrogen storage material is preferably a flexible component or part thereof.

[0045] The molded part is preferably manufactured by injection molding, extrusion (including co-extrusion), or blow molding, including extrusion blow molding. Accordingly, the molded part is preferably an injection-molded part, an extruded part, or a blow-molded part. Extrusion and blow molding are particularly suitable for manufacturing hollow bodies, such as pipes and containers, which can be flexible. However, corresponding hollow bodies can also be manufactured by injection molding. The molded part, in particular an injection-molded part, an extruded part, or a blow-molded part, e.g., in the form of a hollow body, can be multi-layered or single-layered. Another manufacturing process is coating. In this process, the hydrogen storage material is deposited, in particular, from a solution, especially a non-aqueous solution.

[0046] The hydrogen storage material is arranged within the gas transport or gas storage system, preferably within a pressurized gas body thereof, or can be an integral part of a portion of the gas transport or gas storage system, preferably the pressurized gas body. The hydrogen storage material can be arranged within the gas transport or gas storage system as a coating on an inner wall, by being attached to an inner wall, or by being fixed within the system using a holding device.

[0047] The hydrogen storage material can be applied, for example, as a coating to the inner wall or part thereof of the gas transport or storage system, e.g., by co-extrusion or a coating process. The entire inner wall, or preferably a portion thereof, can be coated. This could be the inner wall of a pipe, a plastic hose, or another pressurized gas container.

[0048] In a particularly preferred embodiment, the hydrogen storage material is in the form of a film or, more specifically, in the form of at least one layer in a multilayer composite. The film is a single-layer film made of the hydrogen storage material. The multilayer composite can be a multilayer film.

[0049] The hydrogen storage material, in the form of a film or at least one layer in a multilayer composite, is particularly flexible. This flexibility allows the film or multilayer composite to be arranged in a compact form.

[0050] For example, the film or multilayer composite can be wound or folded using spacers. This allows for compact shapes with a small footprint, whereby the metal hydride-coated films or layers in the multilayer composite are spaced apart, enabling the flow of hydrogen or hydrogen-containing gas and thus ensuring good contact.

[0051] The film, or in particular the multilayer composite, can be provided with a textile carrier. The textile carrier allows for a rapid and homogeneous flow of hydrogen through the film, whereby the film or multilayer composite can store the hydrogen in the hydrogen storage material via appropriate diffusion processes.

[0052] The multilayer composite comprises at least one layer of the hydrogen storage material, but it can also consist of two or more layers, or even all layers, made of the hydrogen storage material. In this way, preferred layered hydrogen storage systems in the form of multilayer composites will be obtained, which, for example, have 2 to 10 layers or even more than 10 layers. Multilayer composites with up to 10 layers can be produced, for example, by coextrusion and blow molding.

[0053] By using a multilayer composite, a graded behavior with regard to properties such as hydrogen storage capacity is possible. For example, an innermost layer, which is in direct contact with the hydrogen or hydrogen-containing gas, can be a hydrogen storage material with a high concentration of metal hydride, while an outer layer or layers can have a hydrogen storage material with a lower concentration of metal hydride. Alternatively or additionally, different polymers can be used for the various layers of hydrogen storage material to, for example, vary the kinetics of hydrogen uptake or release.

[0054] In one embodiment, the multilayer composite can, in addition to the at least one layer of hydrogen storage material, also include plastic layers without embedded metal hydride, e.g., made of a polymer that is practically impermeable to hydrogen. Such plastic layers form a barrier layer for hydrogen.

[0055] In this way, multilayer composites can be manufactured that additionally feature barrier layers for hydrogen. It is understood that such a multilayer composite must be designed so that, when installed in the gas transport or gas storage system, one or more layers of the hydrogen storage material face the hydrogen or hydrogen-containing gas in the system, and the barrier layers are arranged on the opposite side. Such a multilayer composite can, for example, be in the form of a hose, pipe, or container that serves as a pressurized gas body for the gas transport or gas storage system, in which the hydrogen storage material is directly integrated.

[0056] Examples of polymers that are practically non-permeable to hydrogen and suitable for use as a hydrogen barrier layer include ethylene-vinyl alcohol copolymer (EVOH), polyamides (PA), such as polyamide 9T, polyvinylidene fluoride (PVDF), elastomeric polyurethanes, thermoplastic polyurethanes (TPU), polyoxymethylene (POM), high-density polyethylene (HDPE), and polyketones. The polymer for such a barrier layer preferably has a hydrogen gas permeability coefficient of less than 0.5 × 10⁻⁹ mol H₂ / (m·s·MPa), measured according to ISO 151051:2017 at 30°C.

[0057] The hydrogen storage material, in the form of a film or a multilayer composite, is installed in the gas transport system or gas storage system, for example, by being adhered to an inner wall. The entire inner wall, or preferably a portion thereof, can be coated. This inner wall can be that of a pipe, a plastic hose, or another pressurized gas body. Alternatively, the hydrogen storage material, in the form of a film or a multilayer composite, is positioned within the gas transport system or gas storage system, for example, using a suitable holding device. As described above, the multilayer composite itself can form the pressurized gas body or a portion thereof.

[0058] The hydrogen storage material can furthermore be in the form of a molded part, in particular an injection-molded part, extruded part, or blow-molded part, or a part of a molded part, in particular an injection-molded part, extruded part, or blow-molded part. The molded part, in particular an injection-molded part, extruded part, or blow-molded part, can be, for example, in the form of a film, a hollow body such as a pipe, hose, or container, or a molded part with a complex geometry, wherein the molded part can be single-layered or multi-layered. Such molded parts can be rigid or, preferably, flexible.

[0059] The molded part, in particular an injection-molded part, extruded part, or blow-molded part, can be made entirely from the hydrogen storage material. Alternatively, the molded part, in particular an injection-molded part, extruded part, or blow-molded part, can be made partly from the hydrogen storage material and partly from a polymer without any metal hydride, e.g., a polymer that is practically impermeable to hydrogen. This part of the molded part then forms a barrier to the hydrogen.

[0060] It is understood that such a molded part, in particular an injection-molded part, extruded part, or blow-molded part, must be designed so that, when installed in the gas transport or gas storage system, the part made of the hydrogen storage material faces the hydrogen or hydrogen-containing gas in the system, and the part with the barrier function is located on the opposite side. Such a molded or injection-molded part can, for example, serve as a pressurized gas body for the gas transport or gas storage system, in which the hydrogen storage material is integrated. Examples of polymers that are practically non-permeable to hydrogen have been described above, to which reference is made.

[0061] The hydrogen storage material, in the form of a molded part, particularly an injection-molded, extruded, or blow-molded part, is installed in the gas transport or gas storage system, for example, by bonding it to an inner wall of the system. Alternatively, the hydrogen storage material, in the form of a molded part, particularly an injection-molded, extruded, or blow-molded part, is positioned in the gas transport or gas storage system, for example, using a suitable holding device. As described above, the molded part, particularly an injection-molded, extruded, or blow-molded part, can itself form the pressurized gas body or a part thereof.

[0062] In a preferred embodiment, the hydrogen storage material is provided with a textured surface, particularly when the hydrogen storage material is in the form of a film or a multilayer composite. The ratio of textured surface area to the geometric area of ​​the textured surface is preferably in the range of 1:1 to 10:1.

[0063] The textured surface allows the hydrogen storage material's absorption capacity to be individually adjusted, as it increases the surface area. Smooth textures have a smaller surface area for hydrogen absorption than textured textures. The surface area to area ratio is crucial. This ratio can vary from texture to texture, but a ratio between 1 and 10 is considered acceptable. Additionally, the texture prevents the hydrogen storage material, whether in the form of a film or a multilayer composite, from "sticking" to itself. The resulting spacing allows for hydrogen flow through the storage material and enables its geometric adaptation and displacement.

[0064] The texture can be applied in conventional ways, for example using a steel roller, a texture strip, a silicone roller, or vacuum matrix technology. Furthermore, vacuum matrix technology offers the possibility of incorporating undercuts into the hydrogen storage material.

[0065] For the use according to the invention, a hydrogen storage material is preferably suitable that can absorb hydrogen at a hydrogen partial pressure of 100 bar or less, preferably 60 bar or less, and preferably at a hydrogen partial pressure in the range of 50 to 1 bar. As explained, the desired hydrogen partial pressure can be set, in particular, by selecting a suitable metal hydride, e.g., in the temperature range of -50°C to 120°C.

[0066] In a particularly preferred embodiment, the hydrogen storage material is a multilayer composite or hydrogen layered storage system made of flexible components for passive pressure regulation.

[0067] Conventional mixing and forming processes can be used to produce the hydrogen storage material, although it should be noted that the metal hydrides are generally sensitive to reactions and can react spontaneously in the presence of moisture and / or oxygen.

[0068] Metal hydrides, preferably powdered metal hydrides, should therefore usually be incorporated into the polymer matrix under a protective gas atmosphere, such as argon. This can be achieved through appropriate extrusion processes under protective gas, in which the metal hydride is added to the polymer melt. Alternatively, the polymer for the matrix can be mixed with the metal hydride by a sintering process or a kneading process (e.g., if the polymer is a rubber or an elastomer), which should also be carried out under a protective gas atmosphere. When using chloropolymers, care must be taken to ensure that these compounds do not come into direct contact with the metal hydrides. Chloropolymers can, however, also be used in sandwich composites.

[0069] When using elastomers as the polymer, the mixing of the polymer and metal hydride can be carried out, for example, in an internal mixer. When using thermoplastics as the polymer, the mixing of the polymer and metal hydride can be carried out, for example, by compounding in a screw extruder.

[0070] The hydrogen storage material according to the invention can be recycled after use. A possible recycling step after use is, for example, to remelt the hydrogen storage material containing the polymer and metal hydride and to produce new structures or composite films, for example, using calender or extruder systems.

[0071] In the use according to the invention, the gas transport system for hydrogen-containing gas is preferably a pipeline system for hydrogen or a mixture of hydrogen and at least one other gas, preferably a natural gas / hydrogen mixture. The proportion of hydrogen in the natural gas / hydrogen mixture is not specified and can assume any value, e.g., in the range of 1 to 90 vol.%, such as 1 to 30 vol.%. The pressure in the gas transport system is preferably 100 bar or less, more preferably 60 bar or less, e.g., in the range of 50 bar to 1 bar.

[0072] The gas storage system for hydrogen storage comprises a pressurized gas body, wherein the hydrogen storage material is arranged within the pressurized gas body or is an integral part of the pressurized gas body. The hydrogen storage material preferably absorbs the hydrogen at a hydrogen partial pressure of 100 bar or less, more preferably 60 bar or less, and more preferably at a hydrogen partial pressure in the range of 50 to 1 bar.

[0073] The hydrogen storage material used in a gas storage system according to the invention makes it possible to store hydrogen at low pressure and then for longer periods. The lower pressure required for storage, compared to conventional storage in gas cylinders at high pressures up to 300 bar, also reduces the energy consumption necessary for compression.

[0074] Such a gas storage system is suitable, for example, for storing hydrogen for home applications, which is produced, for example, by electrolysis. Another application is decentralized local hydrogen storage, for example in combination with photovoltaic systems.

[0075] In the use of the hydrogen storage material in a gas storage system as hydrogen storage according to the invention, the hydrogen storage material is also used for passive pressure regulation in the gas storage system.

[0076] The invention also relates to a gas transport system for hydrogen-containing gas and a gas storage system for hydrogen storage, wherein the gas transport system or the gas storage system comprises a hydrogen storage material formed from metal hydride embedded in a hydrogen-permeable polymer matrix.

[0077] It is understood that the hydrogen storage material is arranged within the gas transport system so that it can come into contact with the hydrogen-containing gas. It is further understood that the hydrogen storage material is arranged within the gas storage system so that it can come into contact with the hydrogen.

[0078] All the above information regarding the use according to the invention naturally also applies accordingly to the gas transport or gas storage system according to the invention, in particular with regard to the hydrogen storage material and / or the design of the gas transport system and the gas storage system, so reference is made to it.

[0079] The invention is explained in more detail below using exemplary embodiments and the accompanying drawings. The drawings show: Fig. 1 a schematic cross-sectional view of a gas storage system according to the invention, Fig. 2 a schematic cross-sectional view of a section of a gas transport system according to the invention.

[0080] Figure 1 Figure 1 schematically shows a gas storage system according to the invention in the form of a buffer tank 2. The buffer tank is replaceable. The buffer tank comprises a tank shell or pressure vessel 3. The hydrogen storage material 4 used according to the invention, made of metal hydride and embedded in a polymer matrix, is contained within the buffer tank. The buffer tank is connected to a gas line 1 for hydrogen. The pressure in the gas storage system is, for example, in the range of 50 bar to 1 bar. Hydrogen, which was produced, for example, by electrolysis, can be stored in the gas storage system and released again as needed. The hydrogen storage material also provides passive pressure regulation in the gas storage system.

[0081] Figure 2 Figure 1 shows a schematic cross-sectional view of a section of a gas transport system according to the invention. It comprises a gas line 1, in particular in the form of a pipe within a pipe assembly. Hydrogen storage material 4, made of metal hydride and embedded in a polymer matrix, is arranged at various positions in the gas line according to the invention and serves for passive pressure regulation in the gas transport system. For example, hydrogen or a mixture of hydrogen and natural gas can be transported in the gas line. Reference symbol list

[0082] 1 Gas line 2 Expansion tank 3 Tank shell / pressure vessel 4 Storage medium made of polymer matrix and metal hydride

Claims

1. Use of a hydrogen storage material for passive pressure regulation in a gas transport system for hydrogen-containing gas or for hydrogen storage and passive pressure regulation in a gas storage system for hydrogen, wherein the hydrogen storage material is formed from metal hydride embedded in a hydrogen-permeable polymer matrix.

2. Use according to claim 1, wherein the metal hydride is selected from magnesium hydride, lithium hydride, complex metal hydride, preferably metal boranate or metal alanate, or reactive hydride composite (RHC), preferably RHC based on at least two metal hydrides or based on at least one metal amide and at least one metal hydride, wherein advantageous examples of the metal hydride are MgH2, LiH, lithium borohydride, sodium borohydride, magnesium borohydride, sodium aluminum hydride and RHC systems based on Mg(NH2)2-LiH, Mg(NH2)2-LiH-LiBH4, LiBH4-MgH2 or Ca(BH4)2-MgH2.

3. Use according to claim 1, wherein the metal hydride is a particulate metal hydride, preferably with a grain size of 0.1 to 500 µm, more preferably 0.1 to 250 µm and more preferably 0.1 to 50 µm.

4. Use according to any one of the preceding claims, wherein the polymer of the polymer matrix has a hydrogen gas permeability coefficient of at least 4 × 10 -9 mol H2 / (m·s·MPa), measured according to ISO 151051:2017 at 30°C.

5. Use according to any one of the preceding claims, wherein the polymer of the polymer matrix is ​​selected from polypropylene (PP), low-density polyethylene (LD-PE), perfluoroalkoxy polymer (PFA), polystyrene (PS), acrylonitrile butadiene styrene copolymer (ABS), styrene butadiene styrene copolymer (SBS), styrene ethylene butylene styrene block copolymer (SEBS), styrene block copolymer (SBC), chlorosulfate polyethylene or chlorosulfonated polyethylene (CSM), chloroprene, silicones, fluororubber (FPM or FKM), ethylene propylene diene monomer rubber (EPDM) or a combination thereof.

6. Use according to any of the preceding claims, wherein the proportion of amorphous phase in the polymer of the polymer matrix is ​​at least 40%, preferably at least 80%.

7. Use according to any of the preceding claims, wherein the weight ratio of polymer of the polymer matrix to metal hydride (P:M) is in the range of 1 : 4 to 49 : 1, preferably 1 : 3 to 9 : 1, more preferably 1 : 3 to 1 :

1.

8. Use according to any of the preceding claims, wherein the hydrogen storage material is in the form of a coating, a film, at least one layer in a multilayer composite, a molded part, in particular an injection molded part, an extrusion part or a blow molded part, or a part of a molded part, in particular an injection molded part, an extrusion part or a blow molded part, wherein the hydrogen storage material is preferably a flexible component or a part thereof.

9. Use according to any of the preceding claims, wherein the hydrogen storage material is provided with a texture on the surface, wherein the ratio of textured surface to the geometric area of ​​the textured surface is preferably in the range of 1 to 1 to 10 to 1.

10. Use according to any of the preceding claims, wherein the hydrogen storage material can absorb hydrogen at a hydrogen partial pressure of 100 bar or less, preferably 60 bar or less, preferably at a hydrogen partial pressure in the range of 50 to 1 bar.

11. Use according to any of the preceding claims, wherein the gas transport system for hydrogen-containing gas is a pipeline system for hydrogen or a mixture of hydrogen and at least one other gas, preferably a natural gas / hydrogen mixture, wherein the pressure in the gas transport system is preferably in the range of 50 bar to 1 bar.

12. Use according to any of the preceding claims, wherein the gas storage system for hydrogen storage comprises a pressure gas body, wherein the hydrogen storage material is arranged in the pressure gas body or is an integral part of the pressure gas body, wherein the hydrogen storage material can absorb hydrogen at a hydrogen partial pressure of 100 bar or less, preferably 60 bar or less, preferably at a hydrogen partial pressure in the range of 50 bar to 1 bar.

13. Gas transport system for hydrogen-containing gas or gas storage system for hydrogen storage, comprising a hydrogen storage material formed from metal hydride embedded in a hydrogen-permeable polymer matrix.

14. Gas transport or gas storage system according to claim 13, wherein the hydrogen storage material is defined as in any one of claims 1 to 10 and / or wherein the gas transport system or the gas storage system is defined as in claim 12 or 13.

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