EP3140251A1

EP3140251A1 - Hydrogen store comprising a hydrogenable material and a polymer matrix

Info

Publication number: EP3140251A1
Application number: EP15722140.9A
Authority: EP
Inventors: Antonio Casellas; Eberhard Ernst; Thomas Schupp
Original assignee: GKN Sinter Metals Engineering GmbH
Current assignee: GKN Powder Metallurgy Engineering GmbH
Priority date: 2014-05-05
Filing date: 2015-05-04
Publication date: 2017-03-15
Also published as: US20170190866A1; WO2015169753A1; JP2017523105A; CN106660788A; DE102014006377A1

Abstract

The present invention concerns a hydrogen store comprising a hydrogenable material, a method for producing the hydrogen store and a device for producing the hydrogen store.

Description

Hydrogen storage with a hydrogenatable material and a polymeric matrix

The present invention relates to a hydrogen storage comprising a hydrogenatable material and a polymeric matrix, a method for producing the hydrogen storage, and a device for producing the hydrogen storage.

One of the major challenges of the 21st century is the provision of alternative energy sources. The resources of fossil fuels, such as oil or natural gas, are known to be limited. Hydrogen is an interesting alternative here. Hydrogen (H ₂ ) itself is not an energy source, but must first be produced using other sources of energy. However, unlike, for example, electricity generated directly by solar energy, hydrogen can be stored and transported. In addition, hydrogen can be converted into energy in different ways, for example in a fuel cell or by direct combustion. In this case, only waste water is produced as waste product. The disadvantage of handling hydrogen, however, is that it is easily flammable and in mixture with air highly explosive mixtures, the so-called oxyhydrogen, arise.

Safe storage, even for transport or storage, is therefore a great challenge.

Hydrogen can not be readily stored in a hydrogen storage and then recovered, since hydrogen has the smallest molecules of all gases. US 2006/0030483 AI describes hollow microspheres to represent hydrogen storage. US 2012/0077020 AI and US 2013/0136684 AI disclose the use of carbon as Matrix material in hydrogen storage. The storage of hydrogen in an electrode of a battery is explained in DE 60 030 221 T2.

The object of the invention is to provide a hydrogen storage with improved over the prior art properties, in particular with a prolonged life.

It is a hydrogen storage with the features of claim 1, a method for producing a hydrogen storage with the features of claim 12 and an apparatus for producing a hydrogen storage with the features of claim 14 proposed. Advantageous features, embodiments and further developments will become apparent from the following description, the figures as well as from the claims, wherein individual features of an embodiment 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 can therefore be exchanged as well as omitted, but also be supplemented in addition. 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 a hydrogen storage comprising a hydrogenatable material and a matrix in which the hydrogenatable material is embedded, wherein the matrix comprises at least one polymer. Matrix and hydrogenatable material together form a composite. The term hydrogen storage describes a reservoir in which hydrogen can be stored. In this case, conventional methods for storage and storage of hydrogen may be used, for example compressed gas storage, such as storage in pressure vessels by compression with compressors or liquid 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, for example, metal hydride storage, such as storage as a chemical bond between hydrogen and a metal or alloy, or adsorption storage, such as adsorptive storage of hydrogen in highly porous materials. Furthermore, hydrogen storage systems are also possible for the storage and transport of hydrogen, which temporarily bind the hydrogen to organic substances, resulting in liquid, pressureless storable compounds, so-called "chemically bound 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 does not store hydrogen so that the material is metal or metal alloy.

The term 'composite' describes a composite of two or more bonded materials. In this case, a first material in the present case is the hydrogenatable material, embedded in a second material, the matrix. The Matrix can be porous as well as closed. Preferably, the matrix is porous. By embedding one material in the other material, for example, material properties can complement each other, which otherwise only has the individual component. For the properties of the composites, material properties and geometry of the components are important. 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.

In addition to the at least one polymer, the matrix may have one or more further components, such as, for example, materials for the heat conduction and / or the gas feedthrough.

The matrix may comprise one or more polymers according to the invention and is therefore referred to as a polymeric matrix. The matrix may therefore comprise a polymer or mixtures of two or more polymers. Preferably, the matrix comprises only one polymer. In particular, the matrix itself may be hydrogen storage. 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.

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 matrix. For example, the Hydrogen storage by the polymer has a good temperature resistance, a resistance to the surrounding medium (oxidation resistance, corrosion resistance), a good conductivity, a good hydrogen uptake and storage ability or other properties, such as a mechanical strength, which would otherwise not be possible without the polymer , It is also possible to use polymers which, for example, do not allow storage of hydrogen but permit high elongation, such as, for example, polyamide or polyvinyl acetates.

In the invention, the polymer may be a homopolymer or a copolymer. Copolymers are polymers 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.

Preferably, the polymer (homopolymer) comprises a monomer unit which preferably further contains at least one heteroatom selected from sulfur, oxygen, nitrogen and phosphorus in addition to carbon and hydrogen, so that the resulting polymer is not completely non-polar in contrast to, for example, polyethylene. Also, at least one halogen atom selected from chlorine, bromine, fluorine, iodine and astatine may be present. Preferably, the polymer is a copolymer and / or a terpolymer in which at least one monomer unit in addition to carbon and hydrogen further at least one heteroatom selected from sulfur, oxygen, nitrogen and phosphorus and / or at least one halogen atom selected from chlorine, bromine, fluorine , Iodine and astatine, is present. It is possible that two or more monomer units have a corresponding heteroatom and / or halogen atom.

The polymer preferably has adhesive properties with respect to the hydrogen storage material. This means that it is on Hydrogen storage material adheres well even and thus forms a matrix that adhere stably to the hydrogen storage material even under loads as they occur during hydrogen storage.

The adhesive properties of the polymer enable stable incorporation of the material into a hydrogen reservoir and positioning of the material at a defined location in the hydrogen reservoir for 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 maintained at least approximately at the position within the hydrogen storage where it was originally placed in the reservoir. Stable in particular is to be understood that there are no segregation effects during the cycles in which finer particles separate and remove coarser particles.

The hydrogen storage material of the present invention is particularly a low-temperature hydrogen storage material. In the

Hydrogen storage, which is an exothermic process, therefore occur temperatures of up to 150 ° C. 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. The density of the polymer, determined according to ISO 1183 at 20 ° C., is preferably 0.7 g / cm ³ or more, in particular 0.8 g / cm ³ or more, preferably 0.9 g / cm ³ or more but 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.

By EVA (ethyl vinyl acetate) is meant 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):

(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 1183). 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 with the following general structural formula

(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 110 ° 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 1183), 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%. In this case, 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 2811) 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. Although the matrix is capable of storing hydrogen, the hydrogen storage capacity is still not as pronounced as that of the hydrogen storage material itself. However, the matrix is necessary to minimize or completely avoid any oxidation of the hydrogen storage material that may occur and to prevent hydrogen storage To ensure cohesion between the particles of the material.

It is preferable that the matrix is a polymer having a low crystallinity. The crystallinity of the polymer can significantly change the properties of a material. 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"), which means prepregs are pre-impregnated semi-finished products that are cured under temperature and pressure to produce components Suitable polymers are those having a high viscosity 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. According to the invention, the polymer can either be in the form of a liquid which is brought into contact with the hydrogenatable material. Liquid means that either the polymer is melted. However, according to the invention, it is also included that the polymer is dissolved in a suitable solvent, the solvent being removed again after preparation of the composite material, for example by evaporation. However, it is also possible that the polymer is in the form of a granulate which is mixed with the hydrogenatable material. By compacting the composite material, the polymer softens, resulting in the formation of the matrix in which the hydrogenatable material is embedded. If the polymer is used in the form of particles, that is to say as granules, these preferably have an x ₅₀ particle size (volume-based particle size) in the range from 30 μm to 60 μm, in particular from 40 μm to 45 μm. The x ₉₀ particle size is in particular 90 μηι or less, preferably 80 μηι or less.

The hydrogenatable material can take up the hydrogen and release it again when needed. 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 plate-shaped or powder-like. 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, 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 may have the material in only one specific 3-dimensional configuration, so that all particles of the material have the same spatial extent exhibit. 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. In this way, a higher bulk density and thus a higher density of the hydrogenatable material in the hydrogen storage can be made possible, 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 store hydrogen preferably 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.

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.

With regard to hydrides and their properties, reference is made to Tables 1 to 4 in S. Sakietuna et al, International Journal of Energy, 32 (2007), pp. 1121-1140 within the scope of the disclosure.

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. For example, it can be provided that a low-temperature hydride is used together with a high-temperature hydride. Thus, according to one embodiment, it can be provided that, for example, the low-temperature hydride and the high-temperature hydride are mixed in a layer of a second region. These can also be arranged separately from one another in different layers or regions, in particular also in different second regions. For example, it may be provided that a first region is arranged between these second regions. A further embodiment provides that a first region has a mixture of low and high temperature hydride distributed in the matrix. There is also the possibility that different first regions have either a low-temperature hydride or a high-temperature hydride.

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. Here, A and B respectively denote metals different from each other, 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 Be doped to foreign atoms. The degree of doping may according to the invention up to 50 atomic%, 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 until 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).

In particular, the particles have a particle size x _{50 of} from 20 pm to 700 pm, preferably from 25 pm to 500 pm, especially from 30 pm to 400 pm, in particular from 50 pm to 300 pm. X ₅₀ means that 50% of the Particles have an average particle size which is equal to or less than said 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. While the hydrogen storage stresses in the material occurs, which may cause during a plurality of cycles occurs a reduction in the particle size of x _50.

Preferably, the hydrogenatable material is so firmly integrated in the matrix that it comminutes upon storage of hydrogen. Preference is therefore given to using particles as a hydrogenatable material, which breaks up, while the matrix remains at least predominantly undestroyed. This result is surprising, since it was considered that the matrix would tend to rupture when stretched by volume increase of the hydrogenatable material during storage of hydrogen when high elongation due to volume growth occurs. It is currently believed that the external forces acting on the particles from the outside as a result of the attachment in the matrix in the increase in volume together with the tensions within the particles due to the volume increase lead to a breakup. A break-up of the particles could be found particularly clearly when incorporated into polymer material in the matrix. The matrix of polymer material was able to hold the thus broken particles stable stationary.

Incidentally, tests have shown that, when a binder, in particular an adhesive binder, is used in the matrix for fixing these particles, a particularly good stationary positioning within the matrix is made possible. A binder content may preferably be between 2% and 3% by volume of the matrix volume. Preferably, a large particle change occurs due to breakage of the particles by the storage of hydrogen by a factor of 0.6, more preferably by a factor of 0.4, based on the x ₅₀ particle size at the beginning and after 100 times of storage.

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 50 μm, in particular less than 30 μm and in particular less than 25 μm, a finer powder may form during use which may no longer be able to store hydrogen effectively. In addition, the distribution of the material in the hydrogen storage itself may change. Beds containing particles of material of very small diameters of a few nanometers can collect at the lowest point of the 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. 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 and adhere to the matrix, resulting in improved stability, which is found in particles larger than 700 μm in size. especially of more than 500 pm can not be achieved. The terms "material", "hyd rierbares material" and ^"¬ hydrogen storage material" are in ying of present application, unless defined otherwise, are used synonymously.

A further embodiment provides that the hydrogen storage tank has a high temperaturehyd ridbehälter and a low temperature hydride tank. The high-temperature hydrogen can generate temperatures of over 350 ° C, which must be dissipated. This heat is released very quickly and can for example be used to heat up a component that is in communication with the hydrogen storage. As a high-temperature hydride, for example, metal powder based on Mag nesium be used. In contrast, the low-temperature hydroxide preferably has a temperature in a range preferably between -55 ° C. and 155 ° C., more preferably in a temperature range between 80 ° C. and 140 ° C. A low-temperature hydride is, for example, Ti ₀ , 8 Zr ₀ , ₂ Cr Mn or Ti ₀ , 98 Zr _0/02 V _0/43 Cr _0/0 5 M ni, ₂ . One embodiment provides that hydrogen from the high-temperature hydride tank in the Niedertemperaturhyd tank passes over or vice versa, and each stored there. By way of example and within the scope of the disclosure, reference is hereby made to DE 36 39 545 C1.

With regard to hydrides and their properties, reference is made to Tables 1 to 4 in 3. Sakietuna et. al. , International Journal of Energy, 32 (2007), pp. 121-1240, in the context of the disclosure of the invention.

In addition to the at least one polymer, further components may be contained in the matrix. These components gravitationally have at least one of the following functions: primary hydrogen storage, primary heat conduction and / or primary gas feedthrough. By this is meant that the respective component performs at least this function as the main task in the composite. So it is possible that one component is primarily for hydrogen storage is used, but at the same time is also able to provide at least some thermal conductivity available. However, it is provided that at least one other component is present, which primarily assumes a heat conduction, which means that over this the largest amount of heat is derived compared to the other components of the compressed composite material. In this case, in turn, the primary gas-carrying component can be used, through which, for example, hydrogen (fluid) 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 fluid flowing through within the meaning of the present invention is hydrogen or a gas mixture which contains hydrogen in a proportion of 50% by volume or more, preferably 60% by volume or more, in particular 70% by volume or more, preferably 80% by volume or more, especially 90% by volume or 95% by volume or more. Preferably, the hydrogenatable material stores only hydrogen, so that even when using gas mixtures as a fluid substantially only hydrogen is stored.

The hydrogen storage device preferably has at least 2, preferably more than 2 mutually different layers, wherein one layer of the composite material and a layer different therefrom has at least one of the following functions: primary hydrogen storage, primary heat conduction and / or primary 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 arranged immediately adjacent to a thermally conductive layer, so that the resulting heat in the hydrogen absorption and / or Hydrogen delivery 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 is also able to provide a thermal conductivity available. In such a case, it is preferably provided that at least one other layer is present, which primarily assumes a heat conduction, which means that the largest amount of heat is derived from the compressed composite material in this layer over the other layers in the hydrogen storage. In this case, in turn, the primary gas-carrying layer can be used, through which, for example, hydrogen (fluid) 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.

A thermally conductive layer according to the invention may comprise at least one thermally conductive metal and / or graphite. These materials can also be used as a heat-conducting component. 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 on. 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 is a very high Thermal conductivity of over 400 W / (m- K) has. Aluminum is also preferred since, in addition to the high heat conductivity of 236 W / (m-K), it has a low density and thus a low weight.

According to the invention, graphite comprises both expanded and unexpanded graphite. Preferably, expanded or expandable 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) is poorly adherent in the composite material and 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. However, if one were to use exclusively expanded graphite in uncompacted form, the volume of the hydrogen storage medium could become too large to be able to operate it economically. Therefore, mixtures of expanded and unexpanded graphite are preferably used.

If the hydrogen storage material is compacted by means of pressing during production, expanded graphite results in an oriented layer which can conduct heat particularly well. The graphite 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, for example 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. In this case, this combination is particularly preferred when the two layers directly adjoin one another. According to the invention, it is possible, for example, for a first layer, which represents the first area, to adjoin the composite material according to the invention, comprising a high-temperature hydride, directly to a second layer comprising graphite. This second layer can in turn immediately adjoin a third layer, comprising a heat-conducting metal, which in turn adjoins a fourth, graphite-containing layer. A first layer, comprising the composite material, can then be directly connected to this fourth layer. Any layer sequences are possible according to the invention. In the context of the present invention, "comprising" means that not only the said materials but also other constituents can be contained; preferred means comprise but consist of. Graphite and / or aluminum and / or other thermally conductive metals may be in the form of granules, as a powder or as a sheet or foil. In this case, a plate or film may already constitute a layer in the sense of the present invention. However, it is also conceivable that there are 3-dimensional configurations which form a layer which projects at least partially into the layer of the material composite, whereby a better heat dissipation and supply can be made possible. In particular, graphite has not only a thermal conductivity but also a good gas feedthrough. However, aluminum has better heat conductivity than graphite.

For the passage of gas, the hydrogen storage preferably has a porous layer. This may be, for example, a heat conducting layer comprising graphite, as described above. According to the invention, a porous layer can also be a porous region in which the heat-conducting metal or even the hydrogenatable material is not pressed tightly, so that a gas feedthrough (fluid feedthrough) is easily possible.

Furthermore, at least one component of the composite, for example one or more intermediate layers of aluminum, may have been produced in a sintering process. In a sintering process, fine-grained, usually ceramic or metallic materials are heated, but usually the temperatures remain below the melting temperature of the main components, so that the shape of the workpiece is maintained. As a rule, there is no or only a very slight shrinkage of tens of millimeters. Furthermore, it is possible to make a choice of material so that compress the particles of the starting material and pore spaces are filled. In principle, a distinction is made between solid phase sintering and liquid phase sintering, which also results in a melt. By the temperature treatment of the sintering is from a fine or coarse-grained green body, in a previous Process step, for example, was formed by extrusion, a solid workpiece. The sintered product receives its final properties, such as hardness, strength or thermal conductivity, which are required in the respective application only by the temperature treatment. Thus, for example, an open-pored matrix can be created in this way, into which the hydrogenatable material is introduced. It is also possible to create in this way channel structures, which are for example gas-conducting and are used in the hydrogen storage.

It is preferred that the hydrogenatable material preferably has a proportion of greater than 50 to 98% by volume and the matrix preferably has a proportion of at least 2% to 50% by volume of the composite. The proportion of vol .-% of the hydrogenatable material and the matrix can be determined by known test methods and detection methods, for example with the aid of a scanning electron microscope. It is also possible to use a light microscope. Preferably, an image program is used, whereby an evaluation by means of a computer program takes place automatically

The matrix can furthermore have different carbon modifications. By using different carbon modifications, the thermal conductivity of the hydrogen storage can be improved. It can thereby be better derived the resulting heat in the absorption and / or release of hydrogen.

It is preferred that the matrix and / or a layer comprise a mixture of different carbon modifications, including, for example, expanded natural graphite as one of the carbon modifications. It is preferred to use unexpanded graphite together with expanded natural graphite, using more unexpanded graphite by weight than expanded graphite. In particular, the matrix may comprise expanded natural graphite in which, for example, a hydrogenatable material is arranged. Further Carbon modifications include, for example, single-walled, double-walled or multiwalled nanotubes, graphenes as well as fullerenes.

It is preferred that the matrix has expanded natural graphite at a weight fraction of 1 to 20% by weight of the composite.

In a preferred embodiment, the proportion of the respective components varies along the composite. The varying proportion may be in the form of a monotone or non-monotonic gradient or in the form of a jump function. As a result, a gradient or an increase of the hydrogenatable material in the matrix can be realized. In this way, the structure of the matrix, for example, depending on the fluid flowing through the hydrogen storage, be adapted.

Furthermore, the matrix may additionally have carbon modifications in the form of short fibers. In this way, a change in length can be compensated. Furthermore, the use of fibers allows improved stability of the matrix.

Preferably, the composite has a porous matrix. By means of a porous matrix, it can be ensured in one embodiment that the matrix is not damaged by a volume expansion of the hydrogenatable material.

Preferably, the matrix has an expansion property, preferably an elastic property in at least one area. In this way it can be ensured that, for example, when hydrogen is taken up, the hydrogenatable material can expand without damaging or overexposing the composite material. By absorbing the hydrogen, for example, the hydrogenatable material can expand, so that a positive volume change (contraction) takes place. at a hydrogen release, the hydrogenatable material can contract, so that a negative volume expansion or contraction occurs. By an expansion property, preferably elastic property in at least one area, the matrix can at least follow the volume expansion of the hydrogenatable material, so that no damage to the matrix occur.

In a preferred embodiment, the hydrogenatable material has a coating. The coating may additionally allow the hydrogenatable material properties. For example, the coating may be a polymer and the coating can improve the gas conduction and the thermal conductivity of the hydrogenatable material. The coating can have the same polymers that form the matrix. However, it is also possible to use different polymers for coating and matrix. By coating the material, it can be ensured that the hydrogen is stored in the material, at the same time preventing or at least reducing weakening of the material, for example by oxidation. An oxidation of the material 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 areas of the material that are oxidized are no longer available for hydrogen storage, so the amount of hydrogen that can be stored by the material, that is, 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 hydrogen storage material to grow over a large number of cycles can be used without the storage capacity of the material is significantly impaired, whereby a long lifetime of the hydrogen storage can be made possible.

It is preferred that the composite is compacted. The compression can be done for example by pressing. The pressing can be done for example by means of an upper and a lower punch by pressure (axial pressing). 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. Also, a preform containing the first and second regions may be placed in the isostatic press, for example, in a liquid. By imposing high pressures, preferably in a range of 500 to 6000 bar, the composite can be made. The high pressures in isostatic pressing, for example, allow new material properties to be created in the composite.

In a preferred embodiment, the composite is compacted by at least 20% of its maximum compaction to at most 92.36% of its maximum compaction. In this way, a mixed density can be provided.

Preferably, it has areas with different functional center of gravity, comprising at least in each case a gas-permeable region, a heat-conducting region and a hydrogen-storing region. It is preferable that a plurality of hydrogen storages can be connected to each other with small housings. In this way, a good result of water absorption and / or release can be achieved.

The invention further relates to a method for producing a hydrogen storage with a hydrogenatable material and a matrix. The matrix preferably has different carbon modifications in addition to the polymer. The hydrogenatable material is incorporated into this matrix, and then a composite is formed which stores hydrogen.

It is preferred that the hydrogenatable material as well as the respective carbon in each case be supplied in isolated form, in particular as a particle or flake and compressed into a composite material. It is preferred that the matrix comprises a mixture of various carbon modifications, including, for example, expanded natural graphite as one of the carbon modifications. Preference is given to using unexpanded graphite together with expanded natural graphite, using more unexpanded graphite than expanded graphite by weight. In particular, the matrix may comprise expanded natural graphite in which, for example, a hydrogenatable material is arranged. Other carbon modifications include, for example, single-walled, double-walled or multi-walled nanotubes, graphenes as well as fullerenes.

In a preferred embodiment, a targeted arrangement of matrix and hydrogenatable material in a pressing device for the formation of mainly gas-permeable areas, heat-conducting areas and hydrogen storage areas in the hydrogen storage.

Preferably, only a matrix material in the hydrogen storage is used as a hydrogenatable component. According to another embodiment becomes predominantly, d .h. at least 50% by weight of the hydrogenatable components in a hydrogen storage medium uses a matrix material. A further embodiment provides that this proportion is more than 80% by weight, preferably more than 90% by weight, in particular at least approximately 100% by weight. Otherwise, another hydrogenatable component may otherwise be, for example, a layered material.

The invention further relates to a device for producing a hydrogen storage device, preferably a hydrogen storage device as described above, particularly preferably having a method as described above, wherein the device has a cavity into which at least one singulated material of the hydrogen storage device is filled, preferably as a flowable, powdery material, wherein a mixer is provided, by means of which a first and a different second carbon modification are miscible, further comprising a first feed for the first carbon modification and a second feed for the second carbon modification and a feed for the hydrogenatable material.

Further advantageous embodiments as well as features will become apparent from the following figures and the associated description. The resulting from the figures and the description of individual features are exemplary only and 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.

It shows:

Fig. 1 shows a detail of a hydrogen storage. 1 shows a section of a hydrogen storage device 10. The hydrogen storage device 10 comprises two outer walls 12, 14 between which a multiplicity of matrices 16 are arranged. In the matrices 16, the hydrogenatable material is embedded. The matrices 16 form a composite together with the hydrogenatable material. The hydrogenatable material is a metal alloy and has a proportion of the composite of 50% to 98% by volume. The matrix 16 has various carbon modifications, such as expanded natural graphite and unexpanded graphite, and has a composite content of 20 to 50% by volume. The expanded natural graphite of the matrix 16 has a weight fraction of 1 to 20 wt .-% of the composite material. The proportion of each component varies along the composite. In this case, the hydrogenatable material is embedded in the matrix 16. For example, the composite material is compressed to 70% of its maximum compaction by compression.

The following paragraphs 1 to 14 summarize further essential features of the present invention.

A hydrogen storage device comprising a hydrogenatable material and a matrix in which the hydrogenatable material is embedded and forms a composite with the matrix.

2. hydrogen storage according to item 1, wherein the hydrogenatable material preferably has a proportion of greater than 50 to 98 vol .-% and the matrix preferably has a proportion of at least 2 to 50 vol .-% of the composite, wherein the matrix has different carbon modifications.

3. hydrogen storage according to item 1 or 2, characterized in that the matrix has expanded natural graphite.

4. hydrogen storage according to one of the preceding figures, characterized in that the matrix has unexpanded graphite. 5. hydrogen storage according to one of the preceding figures, characterized in that the matrix has expanded natural graphite with a weight fraction of 1 to 20 wt .-% of the composite material.

6. hydrogen storage according to one of the preceding figures, characterized in that the proportion of the respective components varies along the composite.

7. hydrogen storage according to one of the preceding figures, characterized in that the composite material comprises a porous matrix substantially of carbon, in which the hydrogenatable material is embedded.

8. hydrogen storage according to one of the preceding figures, characterized in that the composite is compacted, wherein preferably the composite has a matrix of polymer which is combined with graphite.

9. hydrogen storage according to one of the preceding figures, characterized in that the composite is compacted by at least 20% of its maximum compression up to at most 92.36% of its maximum compression.

10. hydrogen storage according to one of the preceding figures, characterized in that it has areas with different functional center of gravity, comprising at least in each case a gas-permeable region, a heat-conducting region and a hydrogen-storing region.

11. A method for producing a hydrogen storage with a hydrogenatable material and a matrix, wherein the matrix is produced by means of different carbon modifications, and the hydrogenatable material is incorporated into this matrix, and then a composite is formed which stores hydrogen.

12. The method according to item 11, characterized in that the hydrogenatable material as well as the respective carbon is supplied in each case in isolated form, in particular as particles or flake and pressed to the composite material.

13. The method according to item 11 or 12, characterized in that a targeted arrangement of matrix and hydrogenatable material in a pressing device is carried out to form predominantly gas-permeable areas, heat-conducting areas and hydrogen storage areas in the hydrogen storage.

14. An apparatus for producing a hydrogen storage, preferably a hydrogen storage according to any one of the numbers 1 to 10, particularly preferably with a method having the features of the numerals 11 to 13, wherein the device has a cavity, in which at least one isolated material of the hydrogen storage is filled , preferably as a flowable, powdery material, wherein a mixer is provided, by means of which a first and a different second carbon modification are miscible, furthermore a first feed for the first carbon modification and a second feed for the second carbon modification and a feed for the hydrogenatable metal ,

Claims

claims:

A hydrogen storage comprising a hydrogenatable material and a matrix comprising at least one polymer.

2. A hydrogen storage according to claim 1, wherein the hydrogenatable material preferably has a proportion of greater than 50 to 98 vol .-% and the matrix preferably has a proportion of at least 2 to 50 vol .-% of the composite.

3. hydrogen storage according to claim 1 or 2, characterized in that the polymer has a density in the range of 0.7 g / cm ³ to 1.3 g / cm ³ , in particular from 0.8 g / cm ³ to 1.25 g / cm ³ .

4. hydrogen storage according to one of claims 1 to 3, characterized in that the polymer has a tensile strength in the range of 10 MPa to 100 MPa, in particular from 15 MPa to 90 MPa.

5. hydrogen storage according to one of claims 1 to 4, characterized in that the polymer is selected from the group comprising EVA, PMMA and EEAMA and mixtures of these polymers.

6. hydrogen storage according to one of claims 1 to 5, characterized in that the matrix further comprises different carbon modifications, wherein the matrix further comprises expanded natural graphite and / or unexpanded graphite.

7. A hydrogen storage device according to any one of claims 1 to 6, characterized in that the matrix comprises a heat-conductive metallic material for forming a heat-dissipating compound.

8. hydrogen storage according to one of the preceding claims, characterized in that the proportion of the respective components along the composite material comprising the matrix and the hydrogenatable material varies.

9. hydrogen storage according to one of the preceding claims, characterized in that the composite is compacted.

10. hydrogen storage according to one of the preceding claims, characterized in that the composite is compacted by at least 20% of its maximum compression up to at most 92.36% of its maximum compression.

11. Hydrogen storage device according to one of the preceding claims, characterized in that it has areas with different functional center of gravity, comprising at least in each case a gas-permeable region, a heat-conducting region and / or a hydrogen-storing region.

12. A method for producing a hydrogen storage comprising a hydrogenatable material and a matrix, wherein the matrix comprises a polymer and the hydrogenatable material is incorporated into this matrix, and then a composite is formed which stores hydrogen.

13. The method according to claim 12, characterized in that a targeted arrangement of matrix and hydrogenatable material in a pressing device is carried out to form predominantly gas-permeable areas, heat-conducting areas and hydrogen storage areas in the hydrogen storage.

14. The method according to any one of claims 12 or 13, characterized in that the hydrogenatable material has already taken up at least once hydrogen for storage before it is incorporated into the matrix.

15. The method according to any one of the preceding claims, characterized in that the hydrogenatable material, firmly bound in the matrix, crushed when stored hydrogen, in particular break up particles of hydrogenatable material, while the matrix remains at least for the most part undestroyed.

16. A device for producing a hydrogen storage device, preferably a hydrogen storage device according to one of claims 1 to 11, particularly preferably with a method having one of claims 12 to 15, wherein the device has a cavity into which at least a singular material of the hydrogen storage is filled, preferably as a flowable, powdery material, wherein a mixer is provided, by means of which a first and a different second carbon modification are miscible, further comprising a first feed for the first carbon modification and a second feed for the second carbon modification and a feed for the hydrogenatable metal and for a polymer.