WO2015169750A1 - Granules of a hydrogenable material - Google Patents

Abstract

The present invention concerns granules of a hydrogenable material, a method for producing a hydrogen store, and a hydrogen store.

Description

 Granules of a hydrogenatable material

The present invention relates to granules of a hydrogenatable material, a process for producing a hydrogen storage, and a hydrogen storage.

Hydrogen can not be readily stored in a hydrogen storage and then recovered again, since hydrogen has the smallest molecules of all gases and diffuses through the hydrogen storage walls. It does not matter if the hydrogen storage walls are made of metal or plastic. The storage capacity of hydrogen storage is also limited: at a correspondingly high pressure, the diffusion through the hydrogen storage walls becomes too strong. As an alternative, it has already been proposed to store hydrogen in metal foams. Here, however, the problem is that the hydrogen storage becomes too heavy.

The object of the invention is to provide a hydrogen storage, the production and properties is improved. This object is achieved with granules with the features of claim 1, with a method for producing a hydrogen storage with the features of claim 9 and with a hydrogen storage with the features of claim 10. Advantageous features, refinements and developments will become apparent from the following description, The figures as well as from the claims, wherein individual features of a design are not limited to these. Rather, one or more features of one embodiment can be linked to one or more features of another embodiment to form further embodiments. In particular, the respective independent claims can also be combined with each other. Also, the wording of the independent claims should not be construed as limiting the claimed subject matter. One or more features of the claims may therefore be interchanged as well as omitted, as well as additionally supplemented. Also, the features cited with reference to a specific embodiment can also be generalized or used in other embodiments, in particular applications as well. The invention relates to granules of a hydrogenatable material, in particular of a metal alloy, wherein the granules are intended for use in one in a hydrogen storage, preferably at least partially disposed in the hydrogen storage and provide a hydrogen storage capacity available.

The term granules here describes a granular surface, which is composed of individual elements (particles). The granules may be composed of two or more particles and obtained, for example, by pressing. Furthermore, the granules may be composed as an agglomerate with the aid of a binder (binder) of at least two particles. Furthermore, it is preferred that the granules in the binder are in particular homogeneously distributed. As a result, a uniform linear shrinkage can be made possible in the production of granules, so that no voids occur. For the purposes of the present application, granules therefore not only describe effects on the surface but also on the particles from which the surface is formed. Granules can also form multiple layers or layers, so that in this case not only the surface-forming layer is meant, but all layers / layers. Layers or layers do not have to be clearly separated from each other, but can merge into one another. A clear separation of individual layers or layers of granules is not necessarily possible.

In particular, the granules can occur as an agglomerate. The term agglomerate here describes a more or less solidified accumulation of previously loose components into a solid composite, which can be produced by technical processes. The agglomerate can have a uniform granule or grain size. However, it is also possible that it has different granule or particle sizes. In the manufacture, a distinction is generally made between press and build-up agglomeration processes. Examples of the press agglomeration are all methods for tablet production. In contrast, there is the Aufbauagglomeration, for example, in the production of exploding paint balls for bangers. In metallurgy, the production of ceramics or the processing of plastics, agglomerates of metallic, mineral or plastic powders are prepared by drying in a mold or the application of pressing pressure and joined by heating below the melting point. In a preferred embodiment, the particles of a granule can either be the same size or have different sizes, for example For example, a particle may be surrounded by several smaller particles. For example, one particle has a size of 250 μm and the several smaller particles have a size of 50 μm. The particles can be bonded together with the aid of a binder, such as an adhesive, for example a polymer. The adhesive may be open to diffusion, preferably open to diffusion for hydrogen, but especially not for oxygen or air, to allow transmission of the hydrogen through the adhesive to the particles, but preferably also to form a protection against oxidation. The binder preferably comprises at least one polymer. The term polymer describes a chemical compound of chain or branched molecules, so-called macromolecules, which in turn consist of identical or similar units, the so-called constitutional repeating units or repeating units. Synthetic polymers are usually plastics.

By using at least one polymer, good optical, mechanical, thermal and / or chemical properties can be assigned to the material by the binder. For example, the hydrogen storage by the polymer may have good temperature resistance, resistance to the surrounding medium (oxidation resistance, corrosion resistance), good conductivity, good hydrogen uptake and storage ability, or other properties such as mechanical strength, which otherwise without the polymer would not be possible. For example, polymers may be used which allow high elongation, such as polyamide or polyvinyl acetates.

In the invention, the polymer may be a homopolymer or a copolymer. Copolymers are polymers which are composed of two or more different monomer units. Copolymers consisting of three different monomers are called terpolymers. For example, according to the invention, the polymer may also comprise a terpolymer.

The polymer (homopolymer) preferably has a monomer unit which, in addition to carbon and hydrogen, furthermore preferably has at least one heteroatom selected from among sulfur, oxygen, nitrogen and phosphorus, so that the polymer obtained in the For example, polyethylene is not completely non-polar. The polymer is preferably a copolymer and / or a terpolymer in which at least one monomer unit in addition to carbon and hydrogen further comprises at least one hetero atom selected from sulfur, oxygen, nitrogen and phosphorus. It is possible that two or more monomer units have a corresponding heteroatom.

The polymer preferably has adhesive properties with respect to the hydrogen storage material. This means that it will adhere well to the hydrogen storage material even under loads as they occur during hydrogen storage.

The adhesive properties of the polymer allow stable incorporation of the material into a hydrogen storage and positioning of the material at a defined location in the hydrogen storage over as long a period as possible, ie, over several cycles of hydrogen storage and hydrogen release. One cycle describes the process of a single hydrogenation and subsequent dehydration. The hydrogen storage material should preferably be stable over at least 500 cycles, in particular over at least 1000 cycles in order to be able to use the material economically. Stable in the sense of the present invention means that the amount of hydrogen that can be stored and the rate at which the hydrogen is stored, even after 500 or 1000 cycles, substantially corresponds to the values at the beginning of the use of the hydrogen storage. In particular, stable means that the hydrogenatable material is held at the position within the hydrogen storage where it was originally placed in the store.

The hydrogenatable material of the present invention in a preferred embodiment is a low temperature hydrogen storage material. In hydrogen storage, which is an exothermic process, temperatures of up to 150 ° C occur. A polymer which is used for the matrix of a corresponding hydrogen storage material must be stable at these temperatures. Therefore, a preferred polymer does not decompose up to a temperature of 180 ° C, in particular up to a temperature of 165 ° C, in particular up to 145 ° C. In particular, the polymer is a polymer having a melting point of 100 ° C or more, especially 105 ° C or more, but less than 150 ° C, especially less than 140 ° C, especially 135 ° C or less. Preferably, the density of the polymer, determined according to ISO 1 183 at 20 ° C, 0.7 g / cm ³ or more, in particular 0.8 g / cm ³ or more, preferably 0.9 g / cm ³ or more however, not more than 1.3 g / cm ³ , preferably not more than 1.25 g / cm ³ , in particular 1.20 g / cm ³ or less. The tensile strength according to ISO 527 is preferably in the range from 10 MPa to 100 MPa, in particular in the range from 15 MPa to 90 MPa, particularly preferably in the range from 15 MPa to 80 MPa. The tensile modulus according to ISO 527 is preferably in the range from 50 MPa to 5000 MPa, in particular in the range from 55 MPa to 4500 MPa, particularly preferably in the range from 60 MPa to 4000 MPa. Surprisingly, it has been found that polymers with these mechanical properties are particularly stable and easy to process. In particular, they allow stable cohesion between the matrix and the hydrogenatable material embedded therein so that the hydrogenatable material remains in the same position within the hydrogen storage for many cycles for a long time. This allows a long life of the hydrogen storage.

For the purposes of the present invention, the polymer is selected from EVA, PMMA, EEAMA and mixtures of these polymers.

EVA (ethyl vinyl acetate) refers to a group of copolymers of ethylene and vinyl acetate which have a vinyl acetate content in the range of 2% to 50% by weight. Lower levels of vinyl acetate result in the formation of hard films, while higher levels result in greater polymer adhesiveness. Typical EVA are solid at room temperature and have a tensile elongation of up to 750%. In addition, EVA are stress cracking resistant. EVA has the following general formula (I):

(Formel (I)). EVA im Sinne der vorliegenden Erfindung weist bevorzugt eine Dichte von 0,9 g/cm³ bis 1 ,0 g/cm³ (nach ISO 1 183) auf. Die Streckspannung nach ISO 527 liegt insbesondere bei 4 bis 12 MPa, bevorzugt im Bereich von 5 MPa bis 10 MPa, besonders von 5 bis 8 MPa. Insbesondere geeignet sind solche EVA, welche eine Zugfestigkeit (nach ISO 527) von mehr als 12 MPa, insbesondere mehr als 15 MPa, und weniger als 50 MPa, insbesondere weniger als 40 MPa, besonders von 25 MPa oder weniger aufweisen. Die Reißdehnung (nach ISO 527) liegt insbesondere bei >30% oder >35%, besonders bei >40% oder 45%, bevorzugt bei >50%. Dabei liegt der Zug-E-Modul bevorzugt im Bereich von 35 MPa bis 120 MPA, besonders von 40 MPa bis 100 MPa, bevorzugt von 45 MPa bis 90 MPa, insbesondere von 50 MPa bis 80 MPa. Geeignete EVA werden beispielsweise von der Firma Axalta Coating Systems LLC unter dem Handelsnamen Coathylene^® CB 3547 vertrieben.

(Formula (I)). For the purposes of the present invention, EVA preferably has a density of 0.9 g / cm ³ to 1.0 g / cm ³ (according to ISO 1 183). The yield stress according to ISO 527 is in particular from 4 to 12 MPa, preferably from 5 MPa to 10 MPa, especially from 5 to 8 MPa. Particularly suitable are those EVA which have a tensile strength (according to ISO 527) of more than 12 MPa, in particular more than 15 MPa, and less than 50 MPa, in particular less than 40 MPa, in particular of 25 MPa or less. The elongation at break (according to ISO 527) is in particular> 30% or> 35%, especially> 40% or 45%, preferably> 50%. In this case, the tensile modulus of elasticity is preferably in the range from 35 MPa to 120 MPA, especially from 40 MPa to 100 MPa, preferably from 45 MPa to 90 MPa, in particular from 50 MPa to 80 MPa. Suitable EVA are sold for example by the company axalta Coating Systems LLC under the trade name Coathylene ^® CB 3547th

Polymethyl methacrylate (PMMA) is a synthetic, transparent, thermoplastic material having the following general structural formula (II):

(Formel (II))

(Formula (II))

The glass transition temperature is dependent on the molecular weight at about 45 ° C to 130 ° C. The softening temperature is preferably 80 ° C to 120 ° C, especially 90 ° C to 1 10 ° C. The thermoplastic copolymer is characterized by its resistance to weathering, light and UV radiation.

For the purposes of the present invention, PMMA preferably has a density of 0.9 to 1.5 g / cm ³ (according to ISO 1 183), in particular from 1.0 g / cm ³ to 1.25 g / cm ³ . Particularly suitable are those PMMA which have a tensile strength (according to ISO 527) of more than 30 MPa, preferably of more than 40 MPa, in particular more than 50 MPa, and less than 90 MPa, in particular less than 85 MPa, especially of 80 MPa or have less. The elongation at break (according to ISO 527) is in particular <10%, especially <8%, preferably <5%. The tensile modulus of elasticity is preferably in the range from 900 MPa to 5000 MPa, preferably from 1200 to 4500 MPa, in particular from 2000 MPa to 4000 MPa. Suitable PMMA are offered for example by the company Ter Hell Plastics GmbH, Bochum, Germany, under the trade name 7M Plexiglas ^® granules.

EEAMA is a terpolymer of ethylene, acrylic ester and maleic anhydride monomer units. EEAMA has a melting point of about 102 ° C, depending on the molecular weight. It preferably has a relative density at 20 ° C. (DIN 53217 / ISO 281 1) of 1.0 g / cm ³ or less and 0.85 g / cm ³ or more. Suitable EEAMA be marketed under the trade name Coathylene ^® TB3580 by the company axalta Coating Systems LLC.

Preferably, the composite material essentially comprises the hydrogen storage material and the matrix. The weight fraction of the matrix based on the total weight of the composite material is preferably 10% by weight or less, in particular 8% by weight or less, more preferably 5% by weight or less, and is preferably at least 1% by weight and in particular at least 2 wt .-% to 3 wt .-%. It is desirable to keep the proportion by weight of the matrix as low as possible. Even though the matrix is capable of storing hydrogen, the hydrogen storage capacity is nevertheless not as pronounced as that of the hydrogen storage material itself. However, the matrix is necessary in order to minimize or completely avoid any possible oxidation of the hydrogen storage material and to ensure a cohesion between the particles of the material.

It is preferable that the matrix has a polymer having a low crystallinity. Due to the crystallinity of the polymer, the properties of a material can change considerably. The properties of a semi-crystalline material are determined by both the crystalline and the amorphous regions of the polymer. This shows a certain correlation with composite materials, which are also made up of several substances. For example, as the density increases, the extensibility of the matrix decreases.

The matrix can also be in the form of prepregs. Prepreg is the English short form for preimpregnated fibers (in English: "pre-impregnated fibers") Prepregs are pre-impregnated semi-finished products which are cured under temperature and pressure to produce components Polymers are those with a high-viscosity, each but not polymerized thermosetting plastic matrix. The preferred polymers according to the present invention may also be in the form of a prepreg.

The fibers contained in the prepreg can be in the form of a pure unidirectional layer, as a fabric or a scrim. The prepregs according to the invention can also be comminuted and processed as flakes or chips together with the hydrogenatable material to form a composite material.

The term hydrogen storage describes a reservoir in which hydrogen can be stored. In this case, conventional methods for storing and storing hydrogen can be used, for example compressed gas storage, such as storage in pressure vessels by compression with compressors or liquefied natural gas storage, such as storage in liquefied form by cooling and compression. Other alternative forms of storage of hydrogen are based on solids or liquids, such as metal hydride storage, such as storage as a chemical bond between hydrogen and a metal or alloy, or adsorption storage, such as adsorbed storage of hydrogen in highly porous materials. Furthermore, hydrogen storage is also possible for storage and transport of hydrogen, which temporarily bind the hydrogen to organic substances, whereby liquid, pressure-less storable compounds arise, so-called "chemically bonded hydrogen".

Hydrogen storage may include, for example, metals or metal alloys which react with hydrogen to form hydrides (metal hydrides). This process of hydrogen storage is also referred to as hydrogenation and takes place with the release of heat. It is therefore an exothermic reaction. The hydrogen stored in the hydrogenation can be released again during the dehydrogenation. Here, the supply of heat is necessary because the dehydration is an endothermic reaction. A corresponding hydrogen storage can thus have two extreme states: 1) the hydrogen storage material is completely loaded with hydrogen. The material is completely in the form of its hydride; and 2) the hydrogen storage material storage is not hydrogen, so that the material is present as metal or metal alloy. The granules may be compressed and arranged as a composite material, in a matrix or in layers in the hydrogen storage. The term composite material here describes that in the hydrogen storage various types of components are used to arrange the hydrogenatable material. The composite material is formed from individual components, such as the matrix and the individual layers. Material properties and geometry of the components are important for the properties of the composite material. The composite material is compacted.

The term matrix describes a composite of two or more bonded materials. In this case, one material preferably takes on another. The matrix can be porous as well as closed. Preferably, the matrix is porous, in particular so porous that a fluid can flow through. By the inclusion of one material by the other material, for example, material properties can complement each other, which otherwise only has the single component. Material properties and geometry of the components are important for the properties of the composites. In particular, size effects often play a role. The connection takes place, for example, by material or positive connection or a combination of both. In this way, for example, a fixed positioning of the hydrogenatable material can be made possible in the matrix. Other components of the matrix may be, for example, materials for heat conduction and / or gas feedthrough.

The term layers describes that preferably one material, but also two or more materials are arranged in one layer and this can be delimited as a layer from a direct environment. For example, different materials can be poured one after another loosely one over the other so that adjacent layers are in direct contact. In a preferred embodiment, the hydrogenatable layer may be disposed immediately adjacent to a thermally conductive layer, so that the resulting heat in the hydrogen uptake and / or hydrogen release from the hydrogenatable material can be delivered directly to the adjacent layer.

At least one of the following functions of primary hydrogen storage, primary heat conduction and / or primary gas feedthrough is to be understood as meaning that the respective layer perceives at least one of these as a main task in the second region of the composite material. So it is possible that a layer is used primarily for hydrogen storage, but at the same time in the Able to provide at least some thermal conductivity. However, it is provided that at least one other layer is present, which primarily assumes a heat conduction, that is, over which the largest amount of heat is derived from the compressed material composite. In this case, in turn, the primary gas-carrying layer can be used, through which, for example, the hydrogen is introduced into the composite of materials but is also conducted out, for example. In this case, however, heat can also be taken along via the fluid flowing through.

The hydrogenatable material can take up the hydrogen and release it again if necessary. In a preferred embodiment, the material comprises particulate materials in any 3-dimensional configuration, such as particles, granules, fibers, preferably cut fibers, flakes and / or other geometries. In particular, the material may also be formed plate-shaped or powdery. It is not necessary that the material has a uniform configuration. Rather, the design may be regular or irregular. Particles in the sense of the present invention are, for example, approximately spherical particles as well as particles with an irregular and / or angular outer shape. The surface may be smooth, but it is also possible that the surface of the material is rough and / or has bumps and / or depressions and / or elevations. According to the invention, a hydrogen storage device may have the material in only one specific 3-dimensional configuration, so that all particles of the material have the same spatial extent. However, it is also possible that a hydrogen storage comprises the material in different configurations / geometries. By a variety of different geometries or configurations of the material, the material can be used in a variety of different hydrogen storage.

Preferably, the material comprises hollow bodies, for example particles with one or more cavities and / or with a hollow mold, for example a hollow fiber or an extrusion body with a hollow channel. The term hollow fiber describes a cylindrical fiber which has one or more continuous cavities in cross-section. By using a hollow fiber, several hollow fibers can be combined to form a hollow fiber membrane, whereby absorption and / or release of the hydrogen from the material can be facilitated due to the high porosity. The hydrogenatable material preferably has a bimodal size distribution. This allows a higher bulk density and thus a higher density of the hydrogenatable material be made possible in the hydrogen storage, whereby the hydrogen storage capacity, that is, the amount of hydrogen that can be stored in the memory is increased.

According to the invention, the hydrogenatable material may comprise at least one hydrogenatable metal and / or at least one hydrogenatable metal alloy, preferably consisting thereof.

As hydrogenatable materials can also be used:

 Alkaline earth metal and alkali metal alanates,

 - alkaline earth metal and alkali metal borohydrides,

 Metal-Organic-Frameworks (MOF's) / Metal-Organic Frameworks, and / or Clathrates,

as well as of course respective combinations of the respective materials. The material according to the invention may also comprise non-hydrogenatable metals or metal alloys.

The hydrogenatable material according to the invention may comprise a low-temperature hydride and / or a high-temperature hydride. The term hydride refers to the hydrogenatable material, regardless of whether it is present in the hydrogenated form or the non-hydrogenated form. Low-temperature hydrides preferably store hydrogen in a temperature range between -55 ° C to 180 ° C, in particular between -20 ° C and 150 ° C, especially between 0 ° C and 140 ° C. High-temperature hydrides preferably store hydrogen in a temperature range from 280 ° C and more, in particular from 300 ° C and more. At the temperatures mentioned, the hydrides can not only store hydrogen but also give off, so they are functional in these temperature ranges. According to the invention, the granule can comprise both low-temperature hydrides and high-temperature hydrides. Preferably, a granule has either only one or more high temperature hydrides or one or more low temperature hydrides.

If "hydrides" are described in this context, this is to be understood as meaning the hydrogenatable material in its hydrogenated form as well as in its non-hydrogenated form. Hydrogenatable materials in their hydrogenated or nonhydrogenated form can be used according to the invention in the production of hydrogen storages. The hydrogen storage (hydrogenation) can take place at room temperature. The hydrogenation is an exothermic reaction. The resulting heat of reaction can be dissipated. In contrast, energy must be supplied to the hydride in the form of heat for dehydration. Dehydration is an endothermic reaction ..

Preferably, the hydrogenatable material comprises a metal selected from magnesium, titanium, iron, nickel, manganese, nickel, lanthanum, zirconium, vanadium, chromium, or a mixture of two or more of these metals. The hydrogenatable material may also comprise a metal alloy comprising at least one of said metals.

Particularly preferably, the hydrogenatable material (hydrogen storage material) comprises at least one metal alloy capable of at a temperature of 150 ° C or less, in particular in a temperature range of - 20 ° C to 140 ° C, in particular from 0 ° C to 100 ° C. is to store and release hydrogen. The at least one metal alloy is preferably selected from an alloy of the AB ₅ type, the AB type and / or the AB ₂ type. In this case, A and B denote each other different metals, wherein A and / or B are especially selected from the group comprising magnesium, titanium, iron, nickel, manganese, nickel, lanthanum, zirconium, vanadium and chromium .. The indices represent the stoichiometric ratio of the metals in the respective alloy. The alloys according to the invention may be doped with foreign atoms. The degree of doping can according to the invention up to atom%, in particular up to 40 atomic% or up to 35 atomic%, preferably up to 30 atomic% or up to 25 atomic%, especially up to 20 atomic% or up to 15 At%, preferably up to 10 at% or up to 5 at% of A and / or B. The doping can be carried out, for example, with magnesium, titanium, iron, nickel, manganese, nickel, lanthanum or other lanthanides, zirconium, vanadium and / or chromium. The doping can take place with one or more different foreign atoms. Alloys of the AB ₅ type are easily activated, that is, the conditions that are necessary for activation, similar to those in the operation of the hydrogen storage. They also have a higher ductility than alloys of the AB or AB ₂ type. By contrast, alloys of the AB ₂ or the AB type have a higher mechanical stability and hardness compared to alloys of the AB ₅ type. By way of example, mention may be made here of FeTi as the AB-type alloy, TiMn ₂ as the AB ₂ -type alloy, and LaNi ₅ as the AB ₅ -type alloy. Particularly preferably, the hydrogenatable material (hydrogen storage material) comprises a mixture of at least two hydrogenatable alloys, wherein at least one AB ₅ -type alloy and the second alloy is an AB-type and / or AB ₂ -type alloy. The proportion of the alloy of the AB ₅ type is in particular 1 wt .-% to 50 wt .-%, in particular 2 wt .-% to 40 wt .-%, particularly preferably 5 wt .-% to 30 wt .-% and in particular 5% by weight to 20% by weight, based on the total weight of the hydrogenatable material.

The hydrogenatable material (hydrogen storage material) is preferably present in particulate form (particles, particles).

The particles have, in particular, a particle size x _{50 of} from 20 μm to 700 μm, preferably from 25 μm to 500 μm, especially from 30 μm to 400 μm, in particular from 50 μm to 300 μm. Here, x ₅₀ means that 50% of the particles have an average particle size that is equal to or less than the stated value. The particle size was determined by laser diffraction, but can also be done for example by sieve analysis. The mean particle size here is the weight-based particle size, wherein the volume-based particle size is the same here. Indicated here is the particle size of the hydrogenatable material before it is subjected to hydrogenation for the first time. During hydrogen storage, stresses in the material occur, which can result in a reduction in the x ₅₀ particle size over several cycles.

Surprisingly, it has been found that materials of this size show particularly good properties in hydrogen storage. Storage and release of hydrogen results in expansion (during hydrogenation) or shrinkage (during dehydration) of the material. This volume change can be up to 30%. As a result, mechanical stresses occur on the particles of the hydrogenatable material, ie on the hydrogen storage material. Repeated loading and unloading (hydrogenation and dehydrogenation) with hydrogen has been shown to break the particles. If the hydrogenatable material now has in particular a particle size of less than 25 μm, in particular of less than 30 μm and in particular of less than 50 μm, a fine powder is formed during use which can no longer effectively store hydrogen change the distribution of the material in the hydrogen storage itself, and the bulk material that has particles of very small diameters of a few nanometers can penetrate deepest Collect point of hydrogen storage. At a loading with hydrogen (hydrogenation) occur at this point due to the expansion of the hydrogen storage material high mechanical loads on the walls of the hydrogen storage on. By choosing suitable particle sizes for the material, this can be at least partially avoided. On the other hand, a smaller particle size results in a larger number of points of contact at which the particles interact with the matrix and adhere to it, resulting in an improved stability, which is the case for particles with a size of more than 700 μηη, in particular of more than 500 μηη can not be achieved.

The terms "material", "hydrogenatable material" and "hydrogen storage material" are used synonymously in the present application, unless otherwise defined.

With respect to hydrides and their properties, reference is made to Tables 1 to 4 in B. Sakietuna et al., International Journal of Energy, 32 (2007), p.1121-1,140, within the scope of the disclosure.

The particles of the granules can be mixed by means of a flow aid before they are joined together. Furthermore, the particles and the granules can be pressed together. The pressing can be done by means of an upper and a lower punch by pressure. Furthermore, the pressing can be done via an isostatic pressing. The isostatic pressing method is based on the physical law that the pressure in liquids and gases propagates uniformly on all sides and generates forces on the applied surfaces that are directly proportional to these surfaces. The first and second regions can be brought, for example, in a rubber mold into the pressure vessel of a press plant. The pressure, which acts on the rubber mold on all sides via the fluid in the pressure vessel, compresses the enclosed first regions and second regions uniformly. By producing a compact, a better packing density can be obtained, so that a larger number of granules can be arranged in the hydrogen storage. Furthermore, the granules can be extruded or slaked after pressing, for example. Depending on the forces acting, granules can no longer be present after pressing or extrusion since they have dissolved. Thus, the granule particles can be sheared off or otherwise separated. For example, complete separation of the particles or at least at least a predominant separation of the granules are present in their particles. Preference is given to a possible high amount of separated particles, preferably more than 75%, in particular more than 90%. If, for example, only gently pressed, the granule can be preserved.

The term extruded here describes that the granules are fed to an extrusion process. In the extrusion, preferably an extrusion, preferably solid to viscous, in particular curable compositions are pressed out under pressure continuously from a shaping opening. This creates bodies with the cross section of the opening in theoretically any length. According to one embodiment, the material to be extruded can be heated, for example in order to process it better. Another embodiment provides, however, that a heating of the extruder is necessary and the material to be extruded, for example, substantially at room temperature, which means without external heat supply can be extruded.

The Bergriff described here describes that the granules are fed to a slip casting. The slip casting can be used, for example, for a mold casting process, also for a plaster mold casting process, for casting green bodies, blanks, green bodies or other castings. For example, these forms may be suitable for firing to perform drying. Drying can also be done by squeezing out the liquid or other means. The slip casting can also be cast in other forms, for example forms for the production of filters. The slip casting can also be filled into a mold which specifies the component geometry for the hydrogen storage.

The compacts can also be fed to a sintering process.

It is preferred that the granules are mixed with an additional heat-conducting material in the hydrogen storage are arranged. In this way it can be ensured that the granules can dissipate the resulting heat during the hydrogenation and / or dehydrogenation faster. It can also be provided that a granule has at least one heat-conducting particle (heat-conducting particulate material) and one hydrogenatable particle. Preferably, two or more thermally conductive particles can also be attached to a hydrogenatable particle and together form a granule. Preferably, a thermally conductive particle is a graphite particle. A thermally conductive particulate material according to the invention may comprise at least one thermally conductive metal and / or graphite. The thermally conductive material should have a good thermal conductivity on the one hand, on the other hand, but also the lowest possible weight in order to keep the total weight of the hydrogen storage as low as possible. The metal preferably has a thermal conductivity λ of 100 W / (mK) or more, in particular of 120 W / (mK) or more, preferably of 180 W / (mK) or more, especially of 200 or more. The heat-conducting metal according to the invention may also be a metal alloy or a mixture of different metals. Preferably, the thermally conductive metal is selected from silver, copper, gold, aluminum and mixtures of these metals or alloys comprising these metals. Particularly preferred is silver, as this has a very high thermal conductivity of over 400 W / (mK). Aluminum is also preferred since, in addition to the high heat conductivity of 236 W / (mK), it has a low density and thus a low weight.

Graphite according to the invention comprises both expanded and unexpanded graphite. Preferably, expanded graphite is used. Alternatively, carbon nanotubes (single-walled, double-walled or multi-walled) can also be used, since these also have a very high thermal conductivity. Due to the high cost of the nanotubes, it is preferable to use expanded graphite or blends of expanded graphite and unexpanded graphite. If mixtures are present, more unexpanded graphite is used by weight than expanded graphite.

Natural graphite in ground form (non-expanded graphite) does not adhere well to the composite material and is difficult to process into a durable, stable composite. Therefore, in metal hydride-based hydrogen storage, graphite grades based on expanded graphite are preferably used. This is produced in particular from natural graphite and has a significantly lower density than unexpanded graphite, but adheres well in the composite, so that a stable composite material can be obtained. If, however, only expanded graphite were used, the volume of the hydrogen storage medium would be too large to operate economically. Therefore, mixtures of expanded and unexpanded graphite are preferably used. If the hydrogen storage is compacted by means of pressing, expanded graphite results in an oriented layer which can conduct heat particularly well. The Gra- Phite layers (hexagonal planes) in expanded graphite are shifted by the pressure during pressing against each other, so that lamellae or layers form. These hexagonal planes of the graphite are then transverse (approximately perpendicular to the compression direction during an axial pressing operation), so that the hydrogen can then be easily introduced into the composite material and the heat can be well in or out. As a result, not only a heat conduction but also a gas passage or a fluid passage can be made possible. Alternatively, the expanded graphite can be processed, for example, by means of calendar rolls into films. These films will then be ground again. The flakes or flakes thus obtained can then be used as a heat-conducting material. Due to the rolling, a preferred direction in the carbon grid also results here, whereby a particularly good heat and fluid transfer is made possible.

Preferably, graphite is used as the heat-conducting material when a high-temperature hydride is contained as a hydrogenatable material in the composite material. In the case of low-temperature hydrides, a heat-conducting metal, in particular aluminum, is preferred.

Incidentally, a lubricant can also be added to the granules, for example if it is to be introduced into a cavity, in order then to produce a hydrogen storage device therefrom. For example, a wax can be used as a lubricant. Preferably, about 0.4% by weight to about 2% by weight, in particular about 0.4% by weight to 0.8% by weight, based on the total material, is added. The arrangement in the hydrogen storage is hydrogen permeable and in particular porous. In this way it can be ensured that the arrangement of the granules in the hydrogen storage by means of the hydrogenatable material are able to absorb and / or release hydrogen. By a porous and hydrogen-permeable arrangement can be ensured that the hydrogen can reach the hydrogenatable material of the granules. Furthermore, volumetric expansion can take place in the granules due to the uptake and / or release of the hydrogen, for example an expansion of the granules occurs when the hydrogen is taken up, so that the volume expansion is positive, and a contraction of the granules can take place when hydrogen is released, so that the volume expansion is negative and the volume of the granules decreases. In a preferred embodiment, the granules may additionally be provided with a coating.

The term coating in the present application describes the layer applied to the material itself and optionally a process for applying a firmly adhering layer of shapeless material to a surface of a workpiece, in the present case granules. The application of the coating material is referred to as coating. A coating can be a thin layer or a thick layer, as well as several cohesive layers. Coating processes basically differ by the type of layer application in chemical, mechanical, thermal and thermomechanical processes.

Through the coating, the granules can be assigned further properties, such as an oxidation protection layer or a gas guide. For example, the coating is a polymer. Furthermore, the coating on the granules may be only partial and may not cover the entire surface of a granule. The coating may have an extensibility, so as not to be damaged by a change in volume of the granules. Not only the granules as a whole but also the particles which form the granules can be coated.

The granules can take up hydrogen and release it again when needed. By coating the granules or the particles which form the granules, it can be ensured that the hydrogen is stored in the granules, at the same time preventing or at least reducing weakening of the material of the granules, for example by oxidation. An oxidation of the granules would lead to the formation of a layer on the surface through which hydrogen can no longer or only very poorly diffuse through. Thus, the rate at which hydrogenation and dehydrogenation take place is significantly reduced. However, this speed should be as high as possible to enable economical use. In addition, the regions of the granules which are oxidized are no longer available for hydrogen storage, so that the amount of hydrogen that can be stored by the material, ie the hydrogen storage capacity, is reduced. However, just the hydrogen storage capacity should be as large as possible in order to enable economical use. The oxidation-protective layer resulting from the coating now allows the granules to be used over a large number of cycles without significantly affecting the storage capacity of the granules, thereby allowing a long lifetime of the hydrogen storage.

The coating preferably has at least one polymer. The coating may therefore comprise a polymer or mixtures of two or more polymers. Preferably, the coating comprises only one polymer. In particular, the coating itself may be hydrogen-storing. For example, ethylene (polyethylene, PE) can be used. Preferably, a titanium-ethylene compound is used. This can, according to a preferred embodiment, store up to 14% by weight of hydrogen.

By using at least one polymer, the coating can give the granules good optical, mechanical, thermal and / or chemical properties. For example, the granules by the polymer may have good temperature resistance, resistance to the surrounding medium (oxidation resistance, corrosion resistance), good conductivity, good hydrogen uptake and storage ability, or other properties such as mechanical strength, which would otherwise be absent Polymer would not be possible. It is also possible to use polymers which, for example, do not allow the storage of hydrogen but allow a high elongation, such as, for example, polyamide or polyvinyl acetates.

The polymer with which the granules are coated may be the same as the polymer used as binder. It is also possible to use different polymers for coating and as binders.

The coating may be applied to the granules, and in particular to the particles forming the granules, in a manner known to those skilled in the art. Preferably, the polymer is melted and spray applied to the particles or granules. However, it is also conceivable that particles or granules are immersed in a melt of the polymer wholly or partially (dip coating), so that a complete or partial coating is obtained. For coating, it is also possible to dissolve the at least one polymer in a suitable solvent and to bring the polymer solution thus obtained into contact with the hydrogenatable material. This can be done for example by spray application or dip coating. Preferably, the hydrogen storage essentially comprises the hydrogen storage material and the coating. The proportion by weight of the coating based on the total weight of the coated material is preferably 10% by weight or less, in particular 8% by weight or less, more preferably 5% by weight or less, and is preferably at least 1% by weight, and in particular at least 2% to 3% by weight. It is desirable to keep the proportion by weight of the coating as low as possible. Even though the coating is capable of storing hydrogen, the hydrogen storage capacity is nevertheless not as pronounced as that of the hydrogen storage material itself. However, the coating is necessary in order to minimize or completely avoid any possible oxidation of the hydrogen storage material and to ensure a cohesion between the particles of the material.

Furthermore, the granules can be subdivided into their individual particles even under the action of, for example, a shearing force. For example, after an extrusion or a compression, the bonds between the particles of the granules can be released. In particular, a binder can then be further, for example, at least substantially only on one of the particles, in particular if this binder has previously been applied as a coating on only one particle, preferably the hydrogenatable powder particle. For example, for the preparation of the granules, the hydrogenatable material can be mixed in fine powder form together with a solvent and a binder, then, for example, in a countercurrent process, the drying takes place, so that a coating, preferably this binder coating, forms on each particle of the hydrogenatable material. Subsequently, for example, this coated particle can then be connected to at least one other particle via the binder coating and form the granule. The coating is preferably a polymer, in particular hydrogen-permeable. Above all, the tethered particle can have a high thermal conductivity, for example a graphite particle.

Advantageously, several pellets are arranged on granules one above the other and arranged separately from each other by means of an intermediate layer in the hydrogen storage. With the help of the intermediate layers, the granules can be spatially separated from each other. Thereby, a fixed positioning of the granules in the hydrogen storage can be made possible. This can for example prevent segregation of the granules. be changed so that a deterioration of the efficiency can be counteracted.

It is preferred that the intermediate layer comprises a thermally conductive material, for example a carbon material such as graphite, unexpanded and / or expanded graphite, preferably a fabric such as a carbon fabric or a nonwoven. Also other material can be used. In this way, both a fixed positioning of the granules can be made possible, as well as an improved heat conduction. As a thermally conductive material in the intermediate layer and aluminum can be used. It is possible to use aluminum in the form of particles. The particles preferably have a small particle size x ₅₀ , as the particles which form the granules. It can also be a foil or plate made of aluminum as a heat conductor to be used. In a hydrogen storage, for example, a layer of aluminum (either particles or as a foil or plate or tissue) can be introduced. On these then the granules can be applied. Alternately, further heat-conducting layers and layers comprising the granules can then be arranged in the heat accumulator. A corresponding layer structure is of course also possible with graphite particles or films comprising graphite. It is further encompassed by the present invention if both graphite and aluminum are contained as heat-conducting material in one of the forms described in the hydrogen storage.

As heat-conducting material, the already mentioned thermally conductive particulate metals and the graphite modifications explained in this regard can be used.

In a preferred embodiment, the granules and / or particles of granules are portioned in a sheath, preferably in bags, wherein the sheaths are arranged in the hydrogen storage. By means of an enclosure, the granules and / or particles of granules can be arranged in the hydrogen storage at a fixed position. Furthermore, a simple exchange can be made possible by an enclosure, preferably in solid or flexible containers, in particular a bag. It is no longer necessary to replace the entire granules and / or particles of granules, but only the bag can be replaced, in which the granules or particles of granules have a lower efficiency and / or wear and tear. A corresponding container is preferably made a hydrogen permeable material. However, it is also possible for a container to have gas passages to allow for hydrogen exchange.

Preferably, the granules and / or particles of granules remain separated within the wrapping by means of one or more intermediate layers. In this way, an escape of the granules within the enclosure can be avoided.

It is preferred that the granules have a further material in addition to the hydrogenatable material. For example, the further material may be a polymer. The further material can be used to assign additional properties to the granules. For example, the further may have improved gas conduction or improved thermal conductivity. In particular, a granule may have, in addition to the hydrogenatable material, a first further material on a first part and a second further material on a second part, wherein the first material and the second material have different properties, so that the granule may have different properties. For example, the first further material can provide a good gas flow, the hydrogenatable material a hydrogen absorption and the second further material a good thermal conductivity. The invention further relates to a process for the preparation of a hydrogen storage, wherein pourable granules are used, which are made of a hydrogenatable metal. By the method, a hydrogen storage with good properties can be provided. Furthermore, the invention relates to a hydrogen storage comprising the granules described above. Thereby, a hydrogen storage with good properties can be provided.

It is preferred that at least the hydrogen storage material is recyclable. In this way the environment can be spared. For example, the granules can be removed from the hydrogen storage for recycling. Subsequently, the hydrogenatable material can be separated from the other components of the granules. The hydrogenatable material can be recycled to make new granules.

Further advantageous embodiments as well as features will become apparent from the following figures and the associated description. The figures from the figures and the Writing resulting individual features are exemplary only and are not limited to the particular embodiment. Rather, from one or more figures one or more features may be combined with other features from other figures as well as from the above description to further embodiments. Therefore, the features are not limiting but exemplified. Show it:

Fig. 1 is a granule with two equal particles Fig. 2 is a granule with two different sized particles

Fig. 3 shows a granule with a large particle surrounded by a plurality of small particles, furthermore, the granule is surrounded by a protective layer

Fig. 4 shows a detail of a sectional view of a hydrogen storage in which the granules are arranged.

Fig. 1 shows a Granule 10 of a hydrogenatable material 12, in particular a metal alloy, preferably FeTi and / or Mg, and another material 14, in this embodiment, a thermally conductive material. It can be seen that the hydrogenatable material 12 and the further material 14 represent particles which have the same size. The granule 10 is an agglomerate, which consists with the aid of a binder and by pressing from the hydrogenatable material 12 and the further material 14. Furthermore, the further material 14 is permeable to hydrogen, so that the hydrogen can pass through the further material 14 into the hydrogenatable material 12, or can be released from the hydrogenatable material 12 via the further material 14.

Fig. 2 shows a Granule 10, with a hydrogenatable material 12 and another material 16. The hydrogenatable material 12 in this embodiment has a size of 10 μηη and the other material 16 has a size of 100 μηη.

FIG. 3 shows a granule 10 with a hydrogenatable material 12. The hydrogenatable material 12 is surrounded by a multiplicity of further materials 18. In addition, the hydrogenatable material 12 and the other materials 18 are surrounded by a coating 20. The coating 20 can provide the granule with further properties, such as protection against oxidation or improved gas conduction. 4 shows a section of a hydrogen reservoir 22. The hydrogen reservoir 22 comprises two outer walls 24 and 26. Between the outer walls 24 and 26 a plurality of granules 28 is arranged. The granules 28 are pressed together and are arranged one above the other as compacts. The granules 28 are arranged by a plurality of intermediate layers 30, 32, in particular by intermediate layers of a carbon fabric in the hydrogen storage 22. By means of the intermediate layers 30, 32, a positioning of the granules 28 in the hydrogen storage 22 is fixed, furthermore it prevents a separation of the granules 28 from taking place in the hydrogen storage 22. Furthermore, the granules 28 are portioned in a sheath 34, preferably in bags, and arranged in the hydrogen storage. It can be seen that a plurality of envelopes 34 are arranged in the hydrogen storage 22, wherein in the sheaths 34 also have one or more intermediate layers. Furthermore, the granules 28 can be recycled in the hydrogen storage 22. Preferably, the granules are used in a hydrogen storage, as can be seen from DE 10 2014 006 377, wherein the scope of the disclosure of the invention fully incorporated by reference.

The present invention therefore relates to granules of a hydrogenatable material, in particular a metal alloy, preferably FeTi and / or Mg, wherein the granules are intended for use in a hydrogen storage, preferably are arranged partly in the hydrogen storage and provide a hydrogen storage capacity available. Preferably, the granules are mixed with an additional heat-conducting material for use in the hydrogen storage are determined, preferably at least partially disposed in the hydrogen storage. In particular, the arrangement of granules as well as particles of granules in the hydrogen storage is porous and permeable to hydrogen.

Preferably, several pellets of granules are arranged one above the other and arranged separately from one another by means of an intermediate layer in the hydrogen storage. The intermediate layer may comprise a carbonaceous material.

In particular, the granules and / or particles of granules originating in a order hüllung, preferably in fixed or flexible containers, in particular bags portio niert, wherein the sheaths are arranged in the hydrogen storage. Preferably, the granules and / or particles of granules originating within the sheath remain separated by means of one or more intermediate layers. The granules may have, in addition to the hydrogenatable metal, a further material, in particular a heat-conducting material.

In a further embodiment, the present invention relates to a process for producing a hydrogen storage using free-flowing granules made from a hydrogenatable material. In yet another embodiment, the present invention relates to a hydrogen storage produced with granules according to the present invention. Preferably, a granule in the hydrogen storage particles, which are connected to a binder. In particular, the hydrogen storage medium comprises particles of granules, preferably thermally conductive particles and hydrogenatable particles. Preferably, at least the hydrogen-storing material is recyclable.

Claims

claims: 1 . Granules of at least one metal and / or at least one metal alloy as a hydrogenatable material, wherein the granules are intended for use in a hydrogen storage and provide a hydrogen storage capacity. 2. Granules according to claim 1, characterized in that the granules are mixed with an additional heat-conducting material intended for use in the hydrogen storage. 3. Granules according to claim 1 or 2, characterized in that the metal alloy is an alloy of the AB ₅ , the AB and / or the AB ₂ type. 4. Granules according to one of claims 1 to 3, characterized in that the particles which form the granules and / or the granules themselves have a coating. 5. Granules according to claim 4, characterized in that the coating comprises at least one polymer, in particular a copolymer and / or a terpolymer. 6. Granules according to claim 4 or 5, characterized in that the coating comprises EVA and / or PMMA and / or EEAMA. 7. granules according to one of claims 1 to 6, characterized in that the granules in addition to the hydrogenatable metal another material, in particular a heat-conducting material having. 8. hydrogen storage comprising granules according to one of claims 1 to 7. 9. hydrogen storage according to claim 8, characterized in that the granules and / or particles of granules in a sheath, preferably in solid or flexible Containers are portioned, wherein the sheaths are arranged in the hydrogen storage. 10. hydrogen storage according to claim 8 or 9, characterized in that the granules and / or particles of granules originating within the enclosure remain separated by means of one or more intermediate layers. 1 1. Hydrogen storage device according to claim 8, 9 or 10, characterized in that the arrangement of granules as well as particles of granules in the hydrogen storage is porous and permeable to hydrogen. 12. hydrogen storage according to one of claims 8 to 1 1, characterized in that several pellets of granules are arranged one above the other and are arranged separately from each other by means of an intermediate layer in the hydrogen storage. 13. hydrogen storage according to one of claims 8 to 10, wherein at least the hydrogen storage material is recyclable.