Method and system for providing purified hydrogen gas

Abstract

A method for providing hydrogen, comprising: releasing hydrogen (H2) in a dehydrogenation reactor (2) by catalytic dehydrogenation of at least partially loaded hydrogen carrier medium (Hx-LOHC) to form at least partially unloaded hydrogen carrier medium (H0-LOHC); oxidizing the at least partially unloaded hydrogen carrier medium (H0-LOHC) in an oxidation reactor (5) by catalytic oxidation with an oxidizing agent to form at least partially oxidized hydrogen carrier medium (Ox-LOHC); reducing the at least partially oxidized hydrogen carrier medium (Ox-LOHC) by catalytic hydrogenation in a hydrogenation reactor (21) to form the at least partially loaded hydrogen carrier medium (Hx-LOHC); and removing at least one oxygen-containing impurity from the at least partially loaded hydrogen carrier medium (Hx-LOHC) and / or from the at least partially oxidized hydrogen carrier medium (Ox-LOHC).

Description

[0001] This patent application claims the priority of German patent application DE 10 2021 203 884.0, the content of which is incorporated herein by reference. Technical Field

[0002] The present invention relates to a method and a system for providing hydrogen. Background Art

[0003] It is known that hydrogen can be provided by catalytic dehydrogenation of a hydrogen carrier medium. Summary of the Invention

[0004] It is an object of the present invention to improve the supply of hydrogen, in particular by catalytic dehydrogenation of a hydrogen carrier medium, in particular to increase the economic efficiency of the hydrogen supply and / or the purity of the hydrogen provided.

[0005] According to the invention, this object is achieved by a method having the features of claim 1 and by a system having the features of claim 11 .

[0006] The essence of the present invention is that, after releasing hydrogen from the at least partially unloaded hydrogen carrier medium by catalytic dehydrogenation of the at least partially loaded hydrogen carrier medium, the at least partially unloaded hydrogen carrier medium is oxidized by an oxidant to form an at least partially oxidized hydrogen carrier medium. The exothermic oxidation reaction provides heat for the endothermic dehydrogenation reaction. The additional heat requirement is thus reduced and, in particular, unnecessary. The method is economical. Furthermore, it has been found that oxygen-containing impurities are efficiently removed from the at least partially loaded hydrogen carrier medium and / or from the at least partially oxidized hydrogen carrier medium. In particular, it has been found that the removal of oxygen-containing impurities from the at least partially loaded hydrogen carrier medium and / or from the at least partially oxidized hydrogen carrier medium can be carried out in a less complex and more efficient manner than the removal of oxygen-containing impurities from the released hydrogen. The overall purification effort is reduced. The overall efficiency of providing hydrogen of increased purity is reduced.

[0007] Oxygen-containing impurities are, in particular, oxygen-containing by-products, which can be formed, in particular, during the dehydrogenation process, such as carbon monoxide (CO) and carbon dioxide (CO). Oxygen-containing impurities are also understood to mean oxidative degradation products and / or by-products of the hydrogen carrier medium from the oxidation reaction, as well as the at least partially oxidized hydrogen carrier medium from the oxidation reaction. Water, which can be present in liquid or vaporous form, is also understood to be an oxygen-containing impurity. In particular, water can be formed as a by-product during the reduction of the at least partially oxidized hydrogen carrier medium, i.e., during the hydrogenation process, and / or during the oxidation of the at least partially unloaded hydrogen carrier medium.

[0008] It has been recognized that it is advantageous to minimize the proportion of oxygen-containing impurities before the dehydrogenation reaction. Deactivation of the catalyst material used for the dehydrogenation reaction can be avoided. Undesirable oxygen-containing by-products, which then have to be purified from the gas phase at great expense, can be avoided.

[0009] Before the removal of the at least one oxygen-containing impurity, the water content may be from 1% to 25% by weight, depending on the method used during the hydrogenation and / or oxidation. After the hydrogenation, the proportion of at least partially oxidized hydrogen carrier medium is low and, in particular, is at most 1%. After the removal of the at least one oxygen-containing impurity and, in particular, before the dehydrogenation of the at least partially loaded hydrogen carrier medium in the dehydrogenation reactor, the proportion of the at least one oxygen-containing impurity in the fluid stream relative to the mass of all components is, in total, at most 15%, in particular at most 12%, in particular at most 10%, in particular at most 8%, in particular at most 5%, in particular at most 3%, in particular at most 1%, in particular at most 0.5%, in particular at most 0.1%, in particular at most 0.01%.

[0010] It has proven to be particularly advantageous if oxygen-containing impurities are removed from the at least partially loaded hydrogen carrier medium, in particular after the hydrogen carrier medium has been at least partially loaded in the hydrogenation reactor.

[0011] However, the removal of oxygen-containing impurities can additionally or alternatively be carried out from the at least partially oxidized hydrogen carrier medium, in particular before the subsequent hydrogenation reaction in the hydrogenation reactor.

[0012] In particular, it has been recognized that the overall efficiency of the process is improved if an already purified hydrogen carrier medium is provided for the dehydrogenation reaction. Since oxygen-containing impurities have already been at least partially removed from the liquid hydrogen carrier medium in a previous purification step, the proportion of impurities in the released hydrogen can be effectively reduced (i.e. lowered) right from the outset.

[0013] The hydrogenation is carried out over a hydrogenation catalyst, in particular at a pressure of 5 to 50 barg, in particular 10 to 40 barg, and in particular 15 to 30 barg, and at a reaction temperature of 100 to 350° C., in particular 150 to 300° C., and in particular 200 to 270° C. The materials used for the hydrogenation catalyst are in particular platinum, palladium, ruthenium and / or rhodium. The catalyst material used for the hydrogenation is in particular applied to an inert catalyst support. The inert material used for the catalyst support may be aluminum oxide, silicon oxide, silicon carbide and / or activated carbon.

[0014] In the catalytic hydrogenation reaction, the at least partially oxidized hydrogen carrier medium Ox-LOHC is chemically converted into the at least partially loaded hydrogen carrier medium Hx-LOHC to form a (particularly chemically) reduced and, in particular, oxygen-free compound, wherein water is eliminated. This elimination of water during the hydrogenation reaction represents the removal of oxygen-containing impurities from the at least partially loaded hydrogen carrier medium Hx-LOHC. This represents an integrated purification step for the at least partially loaded hydrogen carrier medium Hx-LOHC.

[0015] Additionally or alternatively, oxygen-containing impurities can be removed from the at least partially oxidized hydrogen carrier medium Ox-LOHC, in particular by using a stripping column and / or by selective adsorption.

[0016] It has been found that the method according to the invention can provide hydrogen of increased purity. In particular, the purity of the released hydrogen, particularly after final gas purification, is at least 99.0%, particularly at least 99.7%, and in particular at least 99.999%. Gas purification is particularly used to remove oxygen-containing impurities, particularly to remove less than 200 ppmV, particularly less than 100 ppmV, in particular less than 10 ppmV, and in particular less than 1 ppmV. The released hydrogen may still contain hydrocarbons as impurities, with the proportion of these hydrocarbons relative to the released hydrogen being less than 1000 ppmV, in particular less than 500 ppmV, and in particular less than 200 ppmV. The released hydrogen can be transferred to a hydrogen consumer, particularly after gas purification. The hydrogen consumer is particularly a fuel cell.

[0017] An oxidation catalyst, particularly arranged in an oxidation reactor, is used to carry out the oxidation reaction. The oxidation catalyst comprises a catalytically active solid comprising one or more metals, particularly vanadium, antimony, cesium, manganese, titanium, iron, cobalt, copper, platinum, palladium, ruthenium, cerium and / or nickel. Oxidation catalysts comprising vanadium and, in particular, antimony and / or cesium have proven to be particularly advantageous. The metal is particularly attached to a catalyst support, which particularly comprises a porous support material. In particular, it has been found that titanium oxide and / or vanadium oxide can be used as an oxidation catalyst. In this case, no separate support material is required. The individual metal oxides can constitute the oxidation catalyst itself. The mass fraction of the catalyst material relative to the catalyst support material is 0.01% to 50%, in particular 0.1% to 10%, in particular 0.3% to 5%. The catalyst support material is in particular a metal oxide or a carbonaceous support material, in particular porous aluminum oxide, silicon oxide, titanium oxide, silicon carbide, cerium oxide or activated carbon. An oxidation catalyst consisting of vanadium (V) oxide, antimony (III) oxide and cesium carbonate on titanium oxide has proven to be advantageous.

[0018] It has been found that the exothermic heat of the catalytic oxidation reaction can be advantageously utilized in the overall process. In particular, the waste heat from the oxidation reaction can be used in other process steps, particularly the dehydrogenation reaction. Chemically bound hydrogen bound to the at least partially unloaded hydrogen carrier medium HO-LOHC can be efficiently oxidized to water via the oxidation reaction. Since the Hx-LOHC is at least partially incompletely dehydrogenated to HO-LOHC in the dehydrogenation reactor, the hydrogen carrier medium is at least partially discharged, i.e., it still contains a certain amount of residual hydrogen. It has been found that this residual hydrogen can be advantageously oxidized and thus used to provide heat for the dehydrogenation reaction. In particular, the relatively inefficient return transport of the at least partially unloaded hydrogen carrier medium HO-LOHC is avoided.

[0019] By using chemically bound residual hydrogen, the overall efficiency of the process is increased.

[0020] Additionally or alternatively, the conversion of at least one alkyl group and / or at least one alkylene group, in particular at least one methyl group and / or at least one methylene group, into a keto group, into an aldehyde group and / or into a carboxylic acid group can be carried out by oxidation in an oxidation reactor.

[0021] Additionally or alternatively, hydrogen can also be oxidized into water in the oxidation reactor. Hydrogen can be present in the fluid stream supplied to the oxidation reactor, in particular in a physically dissolved form. Hydrogen components that have been released and not completely separated from the fluid stream may also be returned to the oxidation reactor due to recycling. These residual components of the released hydrogen can also be oxidized into water in the oxidation reactor. In particular, the proportion of physically dissolved and / or released hydrogen in the fluid stream supplied to the oxidation reactor is at most 0.001%, and the fluid stream in particular exclusively contains at least partially unloaded hydrogen carrier medium and water gas. The weight percentage relative to the mass of the feed fluid stream is in particular at most 0.02 weight %, in particular at most 0.05 weight %, in particular 0.01 weight %.

[0022] The oxidation reaction converts at most 5%, in particular at most 3%, in particular at most 1% of the carbon contained in the at least partially unloaded hydrogen medium HO-LOHC into carbon dioxide (CO 2 ) and / or carbon monoxide (CO).

[0023] The method according to claim 2 is particularly economical. It has been found that the heat generated in the oxidation reactor can provide at least 60% of the heat required for the dehydrogenation reaction. In particular, at least 70%, in particular at least 80%, in particular at least 90%, and in particular at least 95% of the heat required for the dehydrogenation reaction can be provided. In particular, all the heat required for the dehydrogenation reaction can be provided. This reduces and in particular avoids the need for additional heat supply.

[0024] The use of a dehydrogenation catalyst according to claim 3 has proven to be particularly advantageous. In particular, it has been found that a dehydrogenation catalyst comprising at least a portion of sulfur has a particularly selective effect. Surprisingly, it has been found in particular that the choice of the dehydrogenation catalyst has a direct influence on the selectivity of the oxidation reaction and therefore also on the purity of the hydrogen released. As a result, the formation of by-products, in particular by-products that are not too large and / or not too high-boiling, in particular polycyclic hydrocarbon compounds and / or other polymerization and / or condensation products, in particular polyaromatic hydrocarbons, and / or cracking products such as toluene, xylene and / or benzene and / or their various oxides such as benzophenone, benzoic acid, benzaldehyde and / or phthalic anhydride, during the dehydrogenation reaction can be significantly reduced. As a result of the oxidation of the hydrogen carrier medium, high-boiling molecules can be formed additionally or alternatively as by-products, in particular if the alkyl groups are not completely oxidized and cracked to carbon monoxide (CO) and / or carbon dioxide (CO 2) , but it undergoes intermolecular interactions with other hydrogen carrier mediators. The high-boiling point molecules produced by the oxidation of diphenylmethane and biphenyl are particularly fluorenone, xanthone and anthraquinone.

[0025] Selective dehydrogenation enables oxygen-containing impurities to be reduced, i.e., reduced, and in particular, prevented, in the early stages of the process. The dehydrogenation catalyst comprises a metal catalyst material to which sulfur has been added (i.e., sulfided). In particular, it has been found that selective dehydrogenation is improved if the dehydrogenation catalyst has a metal / sulfur atomic ratio of 1:1 to 1:10, in particular 1:1.5 to 1:5, in particular 1:1.5 to 1:2.5, in particular 1:2. The catalyst material is particularly arranged on a catalyst support and is particularly attached thereto. The catalyst support is in particular aluminum oxide, silicon oxide, silicon carbide and / or activated carbon. The material of the catalyst support is in particular inert, i.e., does not participate in the dehydrogenation reaction. The weight proportion of the catalyst material relative to the catalyst support material is in the range of between 0.1% and 10%, in particular between 0.2% and 8%, in particular between 0.5% and 5%.

[0026] In particular, it has been found that the selectivity of the dehydrogenation reaction has a direct impact on the selectivity of the subsequent oxidation reaction of the at least partially unloaded hydrogen carrier medium. Selective dehydrogenation with the aid of the dehydrogenation catalyst used is particularly efficient for the overall process. In particular, it has been found that polycyclic hydrocarbons cannot be selectively oxidized because, in particular, the selectivity for the oxidation of methyl groups is lower than that for the oxidation of methylene groups. Cleavage products, such as toluene and / or xylene, which may be formed from benzyltoluene, increase the total number of methyl groups converted by the cleavage of the methylene groups.

[0027] The method according to claim 4 reduces (i.e., lowers) the amount of undesirable substances by catalytic oxidation. In particular, the formation of carboxylic acid functional groups, aldehyde groups, and / or cyclic high-boiling point by-products can be reduced (i.e., lowered) or avoided. In addition, the formation of undesirable carbon monoxide (CO) and / or carbon dioxide (CO2) is reduced.

[0028] In particular, the total proportion of by-products relative to the mass of all components of the fluid stream is at most 10%, in particular at most 5%, in particular at most 3% and in particular at most 1%. The proportion of carboxylic acid groups and / or aldehyde groups in the fluid stream is at most 5%, in particular at most 3% and in particular at most 1%. The mass fraction of cyclic high-boiling by-products in the fluid stream is at most 5%, in particular at most 3% and in particular at most 1%.

[0029] Oxidative cleavage products are particularly benzoic acid, benzaldehyde, toluic acid and / or tolualdehyde. High-boiling by-products are particularly smaller polycyclic hydrocarbon compounds, such as naphthalene and / or anthracene and / or their oxidized forms, particularly anthraquinone and / or xanthone. However, high-boiling by-products may also have larger hydrocarbon structures and contain up to 12 ring systems. The oxygen functional group is reactive and may contribute to the formation of high-boiling molecular structures, with aldehydes being more reactive than ketones. Carbon monoxide and carbon dioxide may also be formed as products of the complete oxidation of the cleaved methyl groups.

[0030] Such components can be formed, for example, during the oxidation of methyl groups, which are present in particular in toluene and / or xylene. By selective oxidation during the catalytic oxidation reaction, the proportion of oxygen-containing impurities can be reduced overall, i.e., decreased, and can amount to at most 10%, in particular at most 8%, in particular at most 5%, in particular at most 3%, in particular at most 2%, in particular at most 1%, in particular at most 0.5%, in particular at most 0.1%, and in particular at most 0.01%, relative to the mass of all components in the fluid stream. The values ​​mentioned here refer to oxygen-containing impurities excluding water.

[0031] In particular, phenyl and / or its hydrogenated forms, in particular as in benzyltoluene and / or dibenzyltoluene, act as the residue of an alkyl and / or alkylene group. In particular, a methylene group may be arranged in a longer alkyl chain, in particular between two hydrocarbon rings or as a substituent on a hydrocarbon ring.

[0032] The method according to claim 5 enables a targeted oxidation reaction. For example, oxygen and / or air are used as the oxidant. It has been found that liquid compounds, such as hydrogen peroxide, can also act as the oxidant. It is also possible to use an oxidant that is present as a solid, in particular, in a bulk form in the oxidation reactor.

[0033] In a first embodiment, the oxidation reaction is carried out in the presence of an at least partially unloaded hydrogen carrier medium and an oxidant in contact with an oxidation catalyst. In particular, the at least partially unloaded hydrogen carrier medium and the oxidant are fed together and simultaneously to the oxidation reactor.

[0034] In a second embodiment, the addition of the at least partially unloaded hydrogen carrier medium and the addition of the oxidant are separated in time. The oxidation reaction is carried out as follows: in a first reaction step, only the at least partially unloaded hydrogen carrier medium contacts the oxidized catalyst in the reaction unit, and the oxidized form of the catalyst is converted to the reduced form of the catalyst by reaction of oxygen bound to the catalyst with the at least partially unloaded hydrogen carrier medium, wherein at least one hydrogen atom is transferred to the at least partially unloaded hydrogen carrier medium, thereby modifying the catalyst. The catalyst reduced in this manner is then oxidized again in a second reaction step without further addition of the at least partially unloaded hydrogen carrier medium, but rather by addition of an oxidant, in particular air. This second reaction step can be carried out under different or the same temperature and pressure conditions as the first reaction step. In this second embodiment, the first and second reaction steps alternate, in particular at regular intervals. The step changes occur at time intervals of between 2 seconds and 5 hours, in particular between 10 seconds and 1 hour, and in particular between 60 seconds and 30 minutes. The reaction steps can include the same or different time periods.

[0035] Surprisingly, it has been found that in this second embodiment, the temporary separation of the addition of the at least partially unloaded hydrogen carrier medium and the oxidant leads to an increase in the selectivity of the oxidation of the at least partially unloaded hydrogen carrier medium. In particular, under comparable temperature and pressure conditions, the formation of undesirable carbon dioxide is significantly reduced.

[0036] The at least partially unloaded hydrogen carrier medium and the oxidant are conveyed in the oxidation reactor, in particular countercurrently, ie antiparallel to one another. However, in principle, it is also conceivable to operate the oxidation reactor in parallel.

[0037] The oxidant can be added to the oxidation reactor at several oxidant addition points. The oxidant addition points can be arranged spaced apart from one another along the reaction zone in the oxidation reactor. This allows the oxygen concentration along the reaction zone to be selectively adjusted. By adjusting the oxygen concentration in the oxidation reactor, the oxidation reaction is directly influenced, and thus the temperature profile established along the reaction zone, and thus the heat profile available for transport to the dehydrogenation reactor. By adding the oxidant, the temperature profile in the oxidation reactor can be adjusted, in particular adjusted and, in particular, evenly distributed.

[0038] Additionally or alternatively, the reaction dynamics in the oxidation reactor can also be controlled by active cooling in the oxidation reactor, in particular along the reaction zone. This makes it possible, in particular, to adjust the temperature distribution along the reaction zone. In particular, exothermic peaks, i.e., excessive temperatures, can be suppressed. Active cooling can be performed, for example, by metering cold air and / or a less heated oxidant, in particular relative to the reaction temperature in the oxidation reactor. The additionally metered oxidant for active cooling has a maximum temperature of at most 300° C., in particular at most 200° C., in particular at most 150° C., in particular at most 100° C., in particular at most 100° C., in particular at most 50° C., in particular at most 30° C.

[0039] In particular, it is conceivable that the oxygen concentration in the oxidation reactor is detected by at least one sensor, in particular a plurality of sensors, which are arranged spaced apart from one another along the reaction zone, and that the addition of the oxidant at the oxidant addition point is carried out in a controlled manner. For this purpose, a controllable valve can be arranged at the oxidant addition point. The controlled supply of oxidant can also be carried out using only one oxidant addition point.

[0040] Additionally or alternatively, the temperature in the oxidation reactor can also be controlled by returning the at least partially oxidized hydrogen carrier medium from the oxidation reactor to the oxidation reactor in a direct recycle stream via a direct return line, in particular feeding the oxidation reactor together with the at least partially unloaded hydrogen carrier medium HO-LOHC. The ratio of recycled oxidized hydrogen carrier medium Ox-LOHC to at least partially unloaded hydrogen carrier medium HO-LOHC allows the temperature distribution in the oxidation reactor to be adjusted, in particular to be more uniform, since partial conversion occurs in each reaction section. In particular, local and / or temporary exothermic peaks can thus be avoided, which could lead to thermal degradation of the hydrogen carrier medium. The risk of premature degradation of the hydrogen carrier medium can be influenced by the target temperature and reduced, i.e., minimized, in the oxidation reactor by targeted addition of oxidant and / or recycling of at least partially oxidized hydrogen carrier medium Ox-LOHC.

[0041] The method according to claim 6 improves its overall efficiency. In particular, the need for external heat is reduced. In particular, it has been found that the oxidant discharged from the oxidation reactor can be advantageously utilized thermally. To this end, it may be advantageous to separate the oxidant from the mixture discharged from the oxidation reactor prior to thermal utilization.

[0042] The method according to claim 7 ensures that the proportion of by-products, in particular undesirable by-products, is reduced in the circulation of the hydrogen carrier medium. In particular, the proportion of polyaromatics and / or cracking products, such as toluene and / or benzene, after the dehydrogenation is at most 3% by weight, in particular at most 1% by weight, in particular at most 0.3% by weight.

[0043] The use of a hydrogen carrier medium according to claim 8 is advantageous. In particular, the hydrogen carrier medium comprises aromatic hydrocarbons with methylene functional groups. A mixture of diphenylmethane and biphenyl has been found to be particularly suitable. Biphenyl has been found to be useful as a eutectic additive to lower the melting point of the mixture to below 20° C. Furthermore, biphenyl has a relatively high hydrogen storage capacity of 7.2% by weight. Diphenylmethane is particularly suitable for oxidation reactions because only methylene functional groups are present, which react selectively, i.e., selectively oxidize. The degradation of the mixture in the form of oxygen-containing by-products is reduced, i.e., minimized. A mixture of biphenyl and diphenylmethane in a ratio of 40:60, in particular 35:65, and especially 30:70 has proven to be particularly advantageous.

[0044] Additionally or alternatively, the hydrogen carrier medium may comprise benzyltoluene and / or dibenzyltoluene.

[0045] The method according to claim 9 reduces the additional heat requirement of the dehydrogenation reaction. It has been recognized that transferring heat to the dehydrogenation reaction is advantageous when the reaction temperature in the oxidation reactor is at least 10°K higher than the reaction temperature in the dehydrogenation reactor. Heat transfer can be performed, for example, via a hot oil circuit. Additionally or alternatively, it is conceivable to structurally integrate the oxidation reactor within and / or onto the dehydrogenation reactor. This simplifies direct heat transfer. For integrating the oxidation reactor into the dehydrogenation reactor, a large-capacity design is particularly suitable, in particular by using a plurality of oxidation tubes to improve heat transfer.

[0046] The method according to claim 10 can provide hydrogen with improved purity.

[0047] The system according to claim 11 essentially has the advantages of the method according to claim 1 , to which reference is hereby made. In particular, it has been found that the system comprising a dehydrogenation reactor, an oxidation reactor, a hydrogenation reactor and a purification unit enables a particularly efficient release process with improved purity of the released hydrogen.

[0048] The system according to claim 12 has proven to be particularly efficient. The removal of oxygen-containing impurities from the hydrogen carrier material by the adsorption unit is particularly efficient. Additionally or alternatively, a water separator and / or a stripping column can also be used as a purification unit.

[0049] The system according to claim 13 simplifies the targeted feeding of the oxidant into the oxidation reactor. In particular, controllable valves are arranged at at least one oxidant addition point, which valves are signal-connected, in particular bidirectionally signal-connected, to the regulating unit.

[0050] The embodiment of the system according to claim 14 is particularly efficient for heat transfer from the oxidation reactor to the dehydrogenation reactor. This improves direct, in particular immediate, heat transfer to the dehydrogenation reactor. Heat transfer losses are minimized. In particular, the ratio of heat generated in the oxidation reactor to that in the dehydrogenation reactor is at least 80%, in particular at least 90%, in particular at least 95%, in particular at least 98%, and in particular 100%.

[0051] A system in which an oxidation reactor has at least one oxidation tube in which an oxidation reaction takes place, wherein the at least one oxidation tube is particularly completely arranged within a dehydrogenation reactor, the system comprising a large-capacity oxidation reactor. This improves heat transfer. It is particularly advantageous if at least 60%, at least 70%, in particular at least 80%, in particular at least 90%, and in particular completely, the oxidation reactor is arranged within the dehydrogenation reactor. A fully integrated arrangement is to be understood as meaning that at least the portion of the oxidation reactor in which the oxidation reaction takes place is completely arranged within the installation space of the dehydrogenation reactor. The installation space of the dehydrogenation reactor is to be understood as meaning the portion of the dehydrogenation reactor in which the dehydrogenation reaction takes place. This means, in particular, that the oxidation reactor can also be completely integrated into the dehydrogenation reactor if individual components of the reactor (e.g., feed lines and connections) are arranged outside the reaction space of the respective other reactor.

[0052] It is particularly advantageous if at least one oxidation tube is at least partially, in particular completely, surrounded by a dehydrogenation catalyst, wherein the flow direction of the at least partially loaded hydrogen carrier medium through the dehydrogenation reactor is arranged transversely and in particular perpendicularly to the longitudinal axis of the at least one oxidation tube.

[0053] The system according to claim 15 advantageously enables integration of multiple oxidant addition points into the oxidation reactor.

[0054] The features indicated in the patent claims and the features given in the examples of embodiment of the system according to the invention are suitable for further embodiment of the subject matter according to the invention, either individually or in combination with one another. The various combinations of features do not represent any restrictions on further embodiments of the subject matter of the invention but are merely exemplary in nature. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] Further features, advantages and details of the present invention will become apparent from the following description of an embodiment example based on the accompanying drawings, in which:

[0056] Figure 1shows a schematic diagram of a system according to the present invention,

[0057] Figure 2 A schematic diagram showing the oxidation reactor integrated in the dehydrogenation reactor.

[0058] Figure 3 Shows the Figure 1 Schematic diagram of the reactions in the system,

[0059] Figure 4 Shown according to Figure 2 Schematic diagram of the functional relationship of oxygen concentration in the oxidation reactor. DETAILED DESCRIPTION

[0060] Figure 1 The system marked 1 in the figure as a whole is used to provide hydrogen, especially hydrogen with higher purity.

[0061] The system 1 has a dehydrogenation reactor 2 in which a dehydrogenation catalyst 9 is arranged. The dehydrogenation catalyst 9 comprises a sulfided metal catalyst material.

[0062] A first separation device 3 is connected to the dehydrogenation catalyst 2, which serves to separate hydrogen from the hydrogen carrier medium which is discharged from the dehydrogenation reactor 2 in an at least partially unloaded form (HO-LOHC).

[0063] The first separation device 3 is connected to a gas purification unit 6, which can be coupled to a hydrogen utilization unit 7. The hydrogen utilization unit 7 is in particular a fuel cell.

[0064] The first recovery device 4 is connected to the first separation device 3, and the recovery device 4 is connected to the oxidation reactor 5. An oxidation catalyst 8 is arranged in the oxidation reactor 5.

[0065] The oxidation catalyst 8 is arranged along the reaction zone in the oxidation reactor 5. The reaction zone in the oxidation reactor is defined by the flow of the at least partially unloaded hydrogen carrier medium HO-LOHC through the oxidation reactor 5. Figure 1 , the reaction zone is oriented from right to left, ie from the outflow opening to the outflow opening of the at least partially unloaded hydrogen carrier medium HO-LOHC.

[0066] The oxidation reactor 5 has a plurality of oxidant addition points 10 at which oxidants can be added individually and, in particular, independently of one another, to the oxidation reactor 5. The oxidant addition points 10 are arranged at a distance from one another along the reaction zone. In particular, the oxidant addition points are arranged one after another along the flow direction through the reaction zone.

[0067] A dosing unit 11 is connected to the oxidation reactor 5 for dosing the oxidant. The dosing unit 11 has a plurality of feed lines 12, via which the oxidant can be added to the oxidation reactor 5. Each feed line 12 is connected to one oxidant addition point 10. The feed lines 12 may have valves, in particular controllable valves, to ensure controlled addition of the oxidant to the oxidation reactor 5.

[0068] A second recovery unit 13 is connected to the oxidation reactor 5. Heat is recovered from the mixture discharged from the oxidation reactor 5 in the second recovery unit 13. The second recovery unit 13 is connected to a second separation unit 14. The second separation unit 14 is used to separate gaseous and liquid components, particularly water. The second separation unit is connected to an electrolyzer 16 via a water line 15. The electrolyzer 16 can be connected to the hydrogen utilization unit 7.

[0069] The heat utilization unit 18 is connected to the second separation device 14 via a gas line 17. In addition, the gas line 17 has a branch line, via which the second separation device 14 is connected to the dosing unit 11. A recovery device 19 is arranged along this branch line. The third recovery device 19 is used in particular to preheat the oxygen-containing mixture used as the oxidant.

[0070] It is conceivable that the oxygen-containing mixture is directly thermally utilized in the thermal utilization unit 18. Additionally or alternatively, the gas line 17 and the third recovery unit 19 allow the oxygen-containing gas mixture to circulate. By circulating the oxygen-containing gas mixture, the heat requirement for preheating in the third recovery unit 19 is reduced. At most, only a small amount of heating is required, and / or no heating is required. This simplifies the provision of oxidant in the dosing unit 11.

[0071] The electrolyser 16 can be connected to the dosing unit 11 via an oxygen line, in particular via a third recovery device 19 .

[0072] The second separation device 14 is connected to the hydrogenation reactor 21 via a hydrogen carrier medium line 20. The hydrogenation reactor 21 is connected to a purification unit 23 via a fluid line 22. According to the embodiment shown, the purification unit 23 is designed as an adsorption unit. The purification unit 23 is connected to the dehydrogenation reactor 2 via a feed line 24.

[0073] The hydrogenation reactor 21 is connected to a second electrolyzer 25 via an additional water line 15. The hydrogenation reactor 21 can also be connected to the electrolyzer 16. This reduces system costs. The hydrogen produced in the electrolyzer can be supplied to the hydrogen utilization unit 7 and / or the hydrogenation reactor 21. The oxygen produced in the electrolyzer 25 can be conveyed to the environment and / or to the dosing unit 11.

[0074] According to the embodiment shown, the dehydrogenation reactor 2 and the oxidation reactor 5 are combined and in particular integrated into each other. The dehydrogenation reactor 2 and the oxidation reactor 5 form a combined reactor 26, which is Figure 1 The design of the combined reactor 26 improves the heat transfer from the oxidation reactor 5 to the dehydrogenation reactor 2, in particular the heat losses during the heat transfer.

[0075] The heat transfer can be carried out in particular by means of a separate heat transfer unit 27, in particular by means of a thermal oil circuit. Figure 1 The heat transfer is only indicated symbolically by the heat transfer arrows.

[0076] See also Figure 2 , an embodiment of the combined reactor 26 is explained in more detail below. The dehydrogenation reactor 2 has an outer housing 28 in which the dehydrogenation catalyst 9 is arranged. The housing 28 has a longitudinal axis 29 which, according to the embodiment example shown, is oriented vertically. The longitudinal axis 29 can be inclined relative to the vertical direction and, in particular, can also be arranged perpendicular to the vertical direction, i.e. horizontally. Figure 2 , a feed line 24 is connected to the dehydrogenation reactor 2 at the bottom. The feed line 24 is used to feed an at least partially loaded hydrogen carrier medium (Hx-LOHC), which has been hydrogenated in the hydrogenation reactor 21, i.e., loaded with hydrogen. The Hx-LOHC flows upward in the dehydrogenation reactor 2 along the longitudinal axis 29. The longitudinal axis 29 determines the flow direction of the medium in the dehydrogenation reactor 2.

[0077] The plurality of oxidation tubes 30 of the oxidation reactor 5 are arranged transversely and in particular perpendicularly to the longitudinal axis 29 in the housing 28. According to the embodiment example shown, the oxidation tubes 30 are oriented horizontally.

[0078] The oxidation catalyst 8 is provided in the oxidation tube 30 .

[0079] The oxidation tubes 30 are arranged one after another along the direction of fluid flow through the oxidation reactor 5 and are connected to each other by connecting tubes 31. The connecting tubes 31 are designed so that one end of each oxidation tube 30 is connected to the starting end of the subsequent oxidation tube 30. The connecting tubes 31 are U-shaped. The interconnected oxidation tubes 30 form a meandering oxidation line. The oxidant addition points 10 are respectively arranged at the transition between the two oxidation tubes 30 arranged in series, particularly in the area of ​​the connecting tubes 31.

[0080] The oxidation tube 30 is embedded in the housing 28 , in particular in the dehydrogenation catalyst 9 , and in particular is completely embedded, ie is completely circumferentially surrounded by the dehydrogenation catalyst 9 .

[0081] The oxidation tube 30 is completely arranged within the housing 28 of the dehydrogenation reactor 2. The oxidation reactor 5 is formed by the entire oxidation tube 30. This means that the oxidation reactor 5 is integrated into the dehydrogenation reactor 2. In this embodiment, the heat transfer unit 27 is formed by the oxidation reactor 5 (in particular, the oxidation tube 30) and the dehydrogenation reactor 2 (in particular, the dehydrogenation catalyst 9). Separate components for the heat transfer unit 27 are unnecessary. The heat transfer unit 27 is an integrated design. This design is particularly space-saving and compact. This embodiment of the heat transfer unit 27 is uncomplicated and cost-effective.

[0082] At one end of the meandering oxidation pipeline, the second separation device 14 is connected to the oxidation reactor 5 , and the oxidation reactor 5 is connected to the hydrogenation reactor 21 .

[0083] The oxidation tubes 30 can be designed with a start-up section. In the region of the start-up section, the oxidation tubes 30 are arranged, in particular, outside the housing 28 of the dehydrogenation reactor 22 and, in particular, not embedded in the dehydrogenation catalyst 9. This means, in particular, that the oxidation tubes 30 are embedded in the dehydrogenation catalyst 9 in some regions. For example, it is conceivable that the oxidation tubes 30 are only partially embedded in the dehydrogenation catalyst 9 relative to their respective tube length. Additionally or alternatively, at least one oxidation tube 30 may not be embedded, or at least not completely embedded, in the dehydrogenation catalyst 9. However, other oxidation tubes may be completely embedded in the dehydrogenation catalyst 9.

[0084] The initial stage for the oxidation reaction makes it possible, in particular, to use the oxidation heat in the region of the initial stage for heating and to set the temperature level to the temperature level for the dehydrogenation.

[0085] The method of providing hydrogen by the system 1 is explained in more detail below.

[0086] The at least partially loaded hydrogen carrier medium Hx-LOHC, which according to the embodiment shown is formed as a 30:70 mixture of biphenyl and diphenylmethane, is fed to the dehydrogenation reactor 2 and at least partially dehydrogenated therein by contact with the dehydrogenation catalyst 9. For the endothermic dehydrogenation reaction, heat is supplied from the oxidation reactor 5 via the heat transfer unit 27.

[0087] The mixture containing the released hydrogen and HO-LOHC is fed from the dehydrogenation reactor 2 to a first separation unit 3. In this first separation unit, gaseous components are separated, in particular from the liquid HO-LOHC, and fed to a gas purification unit 6. In addition to the released hydrogen H2, the gas stream supplied to the gas purification unit 6 also contains gaseous impurities, in particular hydrocarbons, in amounts of up to 1000 ppmV. Furthermore, the gas stream may contain small amounts of oxygen-containing impurities, in amounts of up to 200 ppmV. The gaseous impurities, i.e., hydrocarbons and oxygen-containing impurities, are separated in the gas purification unit 6. The hydrogen supplied from the gas purification unit 6 to the hydrogen utilization unit 7 has a purity of at least 99%.

[0088] The HO-LOHC separated in the first separation device 3 passes through a first recovery device 4 and is fed to the oxidation reactor 5. The first recovery device 4 can also be arranged upstream of the first separation device 3, that is, between the dehydrogenation reactor 2 and the first separation device 3. It is also conceivable to arrange the first recovery device 4 so as to be integrated in the first separation device 3. In the integrated arrangement, the hot heat flows of hydrogen and / or HO-LOHC can be separated from each other efficiently and, in particular, simultaneously, and the heat can be dissipated to the cooler material flow.

[0089] Due to the selective dehydrogenation occurring in dehydrogenation reactor 2, LOHC cracking products and / or high-boiling by-products that are not readily available for oxidation are reduced, i.e., decreased, in the oxidized material stream fed to oxidation reactor 5. LOHC cracking products and high-boiling by-products reduce heat release and are therefore undesirable. By reducing these products, undesirable oxidation, which can lead to an undesirable increase in oxygen-containing impurities in the material stream, is prevented. By avoiding oxygen-containing impurities in the hydrogen carrier medium, the proportion of oxygen-containing impurities in the released hydrogen is reduced, i.e., decreased. Consequently, downstream purification in gas purification unit 6 can be performed with less effort.

[0090] In the oxidation reactor 5, a selective oxidation of HO-LOHC, in particular alkyl functions and / or alkylene groups, in particular R-CH3 or R1-CH2-R2, is carried out.

[0091] The oxidation reaction in the oxidation reactor 5 requires the supply of an oxidant, in particular oxygen or air, in particular by means of a dosing unit 11. The oxidation reaction is exothermic. The heat generated in the process is at least proportionally, in particular completely, transferred from the oxidation reactor 5 to the dehydrogenation reactor 2. A heat transfer unit 27 is used for heat transfer.

[0092] It has been recognized that the reaction conditions in the oxidation reactor 5, i.e., the oxidation conditions, are improved by the fact that the oxidant can be added at different locations along the reaction zone. Oxidant addition points 10 are used for this purpose. This allows, in particular, targeted regulation of the oxygen concentration along the reaction zone. It has been found that controlling the oxygen concentration is directly related to the conversion rate of HO-LOHC and, in particular, the selectivity of the HO-LOHC oxidation. Studies have shown that a substantially uniform distribution of the oxygen concentration along the reaction zone is advantageous.

[0093] Figure 4 An example of a function of the oxygen concentration c across the reaction zone is shown. The reaction zone begins at z0 and ends at z1, with two oxidant addition points 10 at Figure 4 The oxygen concentration in the reaction zone has a maximum value c at the starting point of the reaction zone z0. max, where the oxygen concentration then decreases exponentially until the first oxidant addition point I1. There, the oxygen concentration increases again to a maximum value c at the oxidant addition point I1. max , then it decreases exponentially again to the second oxidant addition point I2, where it increases again to a maximum value c max This gives the oxygen concentration cm The average value of Figure 4 Thus, a uniform distribution of the concentration profile along the reaction zone is understood to mean that the values ​​of the oxygen concentration are within a tolerance range around the mean value c m Move, where the tolerance range is determined by the maximum value c max and the minimum value c min The uniform distribution of concentration distribution exists when the maximum value c max In the mean value c m between 110% and 150%, in particular between 115% and 140%, and in particular between 120% and 130%; the minimum value c min In the mean value c m between 0.5 and 0.9 times the mean value, in particular between 0.6 and 0.85 times the mean value and in particular between 0.65 and 0.75 times the mean value.

[0094] It has been found that the oxygen concentration c can be decisive for the selectivity of the oxidation reaction and, in particular, for the desired selective conversion of the alkylene functional groups. It is advantageous if the initial oxygen concentration, i.e., at the beginning of the reaction zone, is high. This leads to a high productivity of the oxidation reaction. However, a high productivity also means an increase in the formation of by-products. A lower initial oxygen concentration leads to a higher selectivity. Therefore, selectively metering oxygen along the reaction zone can increase the overall productivity, i.e., the average oxygen concentration c. m , while reducing the initial concentration c max , in particular with an exponential decrease in oxygen concentration across the entire reaction zone compared to a single oxygen addition. In particular, due to the higher average concentration c m , which can improve the productivity of the oxidation reaction. Due to the increased conversion rate in the oxidation reaction, the exotherm of reaction increases, i.e., the heat generation available for the dehydrogenation reaction also increases. In particular, it has been found that the more uniform oxygen concentration provided by the multiple oxidant addition points 10 results in a more uniform release of the heat of reaction along the reaction zone. Furthermore, targeted temperature control can be achieved along the reaction zone.

[0095] The heat released by the oxidation reaction in the oxidation reactor 5 is supplied to the dehydrogenation reactor 2 for dehydrogenation. To this end, the oxidation reactor 5 can be integrated into the dehydrogenation reactor 2, such as Figure 2In an integrated embodiment, a large-capacity oxidation reactor 5 comprising a plurality of oxidation tubes 30 is particularly advantageous, wherein the flow direction through the oxidation reactor 5 is particularly countercurrent relative to the fluid flow direction or as shown. Figure 2 Cross flow is shown through the dehydrogenation reactor 2. Advantageously, the reaction temperature in the oxidation reactor is at least 10°K, in particular at least 20°K, in particular at least 30°K, in particular at least 50°K higher than the reaction temperature in the dehydrogenation reactor.

[0096] After the oxidation reaction in the oxidation reactor 5, the material streams are separated from one another in at least a second separation device 14 and recovered in a second recovery device 13, i.e., heat is recovered, particularly for preheating other material streams. As with the first recovery device 4 and the first separation device 3, the order of the second recovery device 13 and the second separation device 14 can also be selected in various ways. In particular, the second recovery device 13 can be integrated into the second separation device 14. In the second separation device 14, liquid components (particularly water and at least partially oxidized hydrogen carrier medium Ox-LOHC) are separated from gaseous components (particularly air and oxygen). Impurities and by-products may still be present in the separated material streams in amounts of up to 5%, particularly up to 3%, particularly up to 1%, and particularly up to 1000 ppmV. In the oxidation reactor 5, at least equimolar amounts of water are formed as a by-product. It is particularly advantageous if the water is separated from the Ox-LOHC in the second separation device 14, purified, and disposed of.

[0097] The water formed in the oxidation reactor 5 can additionally or alternatively be supplied to the electrolyzer 16 via the water line 15. In the electrolyzer 16, the water is separated into its components, wherein the hydrogen released can be supplied to the hydrogen utilization unit 7. The released oxygen can be recycled to the dosing unit 11. Surprisingly, it has been found that the separated water can be advantageously used for electrolysis. The energy requirements required for the electrolysis can be met at least partially by adding external energy and / or coupling the energy of the exothermic oxidation reaction.

[0098] The gas fraction separated in the second separation device 14, in particular oxygen, in particular air, can be thermally utilized together with the carbon compound fraction in the heat utilization unit 18. The released heat can be supplied, for example, to the dehydrogenation reactor 2. In particular, if toxic carbon compounds, such as benzene, are also purified by a purification unit (not shown separately), the separated gas stream can also be discharged directly to the environment. However, the separated gas stream from the second separation device 14 can also be used for the oxidation reaction in the dosing unit 11.

[0099] The fraction of Ox-LOHC separated from water is fed to a dehydrogenation reactor 21 for hydrogenation. It is advantageous if the hydrogenation reactor 21 and the dehydrogenation reactor 2 are arranged at different, in particular spatially distant locations. The hydrogenation reactor 21 is particularly arranged at an energy-rich location, i.e., where there is an excess of energy and where energy is available, in particular, under relatively favorable conditions. The dehydrogenation reactor 2 is particularly arranged at a low-energy location, i.e., where there is a demand for energy and where energy is available, in particular, under cost-intensive conditions. The transport of the hydrogen carrier medium Hx-LOHC from the high-energy location to the low-energy location and the transport of the oxidized hydrogen carrier medium Ox-LOHC from the low-energy location to the high-energy location can be carried out using suitable transport means, such as tank trucks, ships and / or trains, or via pipelines provided for this purpose.

[0100] In particular, it has been found that the transport of Ox-LOHC can be carried out in a simple manner because the Ox-LOHC is essentially saturated with oxygen-containing impurities, in particular water, oxygen-containing carbon compounds, and / or physically dissolved gases. In particular, it does not need to be transported under safety-related controlled conditions. This simplifies transportation. Further contamination with air, oxygen, or water is unlikely. Specifically, expensive immobilization of the Ox-LOHC, in particular in the form of an inert gas blanketing, in particular with nitrogen, is unnecessary or less relevant for existing impurities, which are to be removed at a later time anyway.

[0101] In particular, it has been discovered that the water formed, in particular during the oxidation of LOHC, can be transported together with the oxidized hydrogen carrier medium Ox-LOHC to an energy-rich location. Transport is typically performed by tanker truck. The same volume of water used to transport the unloaded hydrogen carrier medium HO-LOHC is sufficient for transporting the Ox-LOHC. Consequently, it has been discovered that, despite the formation of water, no additional transport effort is required if the water is transported to an energy-rich location. In other words, in particular, no further use and / or treatment of the water occurs in energy-poor locations. Transporting the water to a high-energy location presents no problems, and in particular, as long as the separation of water and hydrogen carrier medium occurs at the high-energy location, no additional effort is involved, since the water is formed during the reduction of the oxidized hydrogen carrier medium Ox-LOHC.

[0102] Advantageously, after the hydrogenation reaction in the hydrogenation reactor 2 , oxygen contamination of the Hx-LOHC is avoided in order to prevent the introduction of oxygenates into the dehydrogenation reactor 2 .

[0103] Ox-LOHC is added to hydrogenation reactor 21 and chemically reduced with hydrogen gas H2. During this process, Ox-LOHC is converted to Hx-LOHC with the release of heat. Oxygen-containing impurities are also converted with the release of heat. During the chemical reduction of functional oxygen-containing groups, an equimolar amount of water is produced.

[0104] In the purification unit 23, located downstream of the hydrogenation catalyst 21, the Hx-LOHC is conditioned and, in particular, separated from oxygen-containing impurities; in particular, unreacted oxygen-containing carbon compounds, in particular Ox-LOHC, and / or further oxidized carbon compounds and / or water. In particular, dissolved oxygen-containing gas is also separated from the Hx-LOHC in the purification unit 23. Surprisingly, it has been discovered that efficient removal of oxygen-containing impurities from the hydrogenated Hx-LOHC can be achieved, in particular by means of a purification unit in the form of a water impurity separator, a stripping column, and / or an adsorption filter stage. Purification of these impurities can be carried out in a simple manner. The purification effort required is reduced. As a result, the Hx-LOHC is provided for subsequent hydrogenation in the hydrogenation unit 21 at a purity that makes subsequent conditioning of the released hydrogen, in particular with respect to oxygen-containing impurities, simple and, in particular, unimportant.

[0105] In addition to or as an alternative to the purification unit 23, it is also conceivable to provide an additional purification unit for removing oxygen-containing impurities (in particular at a high-energy location), which is arranged upstream of the hydrogenation reactor 21. In the upstream purification unit, the selective removal of oxygen-containing impurities is carried out. In particular, the upstream purification unit allows the hydrogenation catalyst in the hydrogenation reactor 21 to be protected.

[0106] It is also conceivable to provide a purification unit at a low-energy location immediately upstream of the dehydrogenation reactor 2 .

[0107] The water separated by the purification unit 23 may be supplied to the electrolytic tank 25 or the electrolytic tank 16 to be split.

[0108] Figure 3 The material flows formed or converted in the relevant units, namely in the dehydrogenation reactor 2, the oxidation reactor 5 and the purification unit 23 are shown. It can be seen that in the dehydrogenation reactor 2, the at least partially loaded hydrogen carrier medium Hx-LOHC is dehydrogenated by means of the sulphurized dehydrogenation catalyst 9 to form an at least partially unloaded hydrogen carrier medium HO-LOHC and release hydrogen. In addition, the material flow discharged from the dehydrogenation reactor 2 contains hydrocarbons (HC), such as toluene and / or cyclohexane, polyaromatic hydrocarbons (PAH), such as naphthalene and / or anthracene, and carbon oxides (oxos), in particular carbon oxides consisting only of carbon and oxygen, such as carbon monoxide (CO) and carbon dioxide (CO 2), in particular oxygenated hydrocarbons, such as benzaldehyde. In particular, the proportion of oxos is substantially determined by the aforementioned adsorption purification in purification unit 23. Since the proportion of water, oxos, and / or Ox-LOHC is reduced, i.e., decreased, in purification unit 23, the proportion of oxos in the substance mixture discharged from dehydrogenation reactor 2 is also reduced, i.e., decreased.

[0109] During the oxidation reaction in the oxidation reactor 5 with the aid of oxygen dosing, HO-LOHC is converted into Ox-LOHC, in particular forming water and oxos, which are chemically reduced.

Claims

1. A method for providing hydrogen, comprising the following steps: - releasing hydrogen H2 by catalytic dehydrogenation of the at least partially loaded hydrogen carrier medium Hx-LOHC in the dehydrogenation reactor (2) to form an at least partially unloaded hydrogen carrier medium HO-LOHC; - catalytic oxidation of the at least partially unloaded hydrogen carrier medium HO-LOHC by means of an oxidizing agent in an oxidation reactor (5) to form an at least partially oxidized hydrogen carrier medium Ox-LOHC; - reducing the at least partially oxidized hydrogen carrier medium Ox-LOHC by catalytic hydrogenation in a hydrogenation reactor (21) to form the at least partially loaded hydrogen carrier medium Hx-LOHC; - removing at least one oxygen-containing impurity from the at least partially loaded hydrogen carrier medium Hx-LOHC and / or from the at least partially oxidized hydrogen carrier medium Ox-LOHC.

2. The method according to claim 1, characterized in that The heat generated in the oxidation reactor (5) is transferred to the dehydrogenation reactor (2).

3. The method according to claim 1 or 2, characterized in that A dehydrogenation catalyst (9) is used, said dehydrogenation catalyst (9) comprising a metal catalyst material.

4. The method according to claim 3, characterized in that The metal catalyst material is platinum, palladium, nickel, rhodium and / or ruthenium.

5. The method according to claim 4, characterized in that The metal catalyst material is sulfided.

6. The method according to claim 1 or 2, characterized in that The catalytic oxidation comprises the selective oxidation of the alkyl functions R—CH 3 and / or alkylene functions R 1 —CH 2 —R 2 of the at least partially unloaded hydrogen carrier medium HO-LOHC.

7. The method according to claim 1 or 2, characterized in that The quantitative addition of the oxidant is used to adjust the oxygen concentration in a targeted manner along the reaction zone in the oxidation reactor (5).

8. The method according to claim 7, characterized in that The quantitative addition of the oxidant is carried out by targetedly adjusting the oxygen concentration through a plurality of oxidant addition points (10) spaced apart along the reaction zone.

9. The method according to claim 1 or 2, characterized in that The oxidant discharged from the oxidation reactor (5) is thermally utilized in a heat utilization unit (18).

10. The method according to claim 1, characterized in that By-products are high-boiling by-products and / or cracking products having aromatic ring systems with more than three members produced by the polymerization and / or condensation reaction.

11. The method according to claim 10, characterized in that The by-products are toluene, xylene and / or benzene in the HO-LOHC after dehydrogenation.

12. The method according to claim 10 or 11, characterized in that The proportion of the by-products is at most 3%.

13. The method according to claim 10 or 11, characterized in that The proportion of the by-products is at most 1%.

14. The method according to claim 10 or 11, characterized in that The proportion of the by-products is at most 0.3%.

15. The method according to claim 1, wherein The aromatic hydrocarbons act as Hx-LOHC.

16. The method according to claim 15, characterized in that The hydrogenated form of the aromatic hydrocarbon acts as Hx-LOHC.

17. The method according to claim 16, characterized in that Aromatic hydrocarbons with methylene functional groups serve as Hx-LOHCs.

18. The method according to claim 17, characterized in that A mixture of biphenyl and diphenylmethane serves as the Hx-LOHC.

19. The method according to claim 18, characterized in that The mixture of biphenyl and diphenylmethane has a ratio of 40:

60.

20. The method according to claim 18, characterized in that The mixture of biphenyl and diphenylmethane has a ratio of 35:

65.

21. The method according to claim 18, characterized in that The mixture of biphenyl and diphenylmethane has a ratio of 30:

70.

22. The method according to claim 1 or 2, characterized in that The reaction temperature during oxidation, T ox Greater than the reaction temperature T during dehydrogenation de .

23. The method according to claim 22, characterized in that T ox ≥10K+T de 。 24. The method according to claim 22, characterized in that T ox ≥20K+T de 。 25. The method according to claim 22, wherein T ox ≥30K+T de 。 26. The method according to claim 22, characterized in that T ox ≥50K+T de 。 27. The method according to claim 1 or 2, characterized in that The hydrogen released by the dehydrogenation has a content of said at least one oxygen-containing impurity of less than 200 ppmV.

28. The method according to claim 1 or 2, characterized in that The hydrogen released by the dehydrogenation has a content of said at least one oxygen-containing impurity of less than 100 ppmV.

29. The method according to claim 1 or 2, characterized in that The hydrogen released by the dehydrogenation has a content of said at least one oxygen-containing impurity of less than 10 ppmV.

30. The method according to claim 1 or 2, characterized in that The hydrogen released by the dehydrogenation has a content of said at least one oxygen-containing impurity of less than 1 ppmV.

31. A system for providing hydrogen, comprising: a dehydrogenation reactor (2) for catalytically dehydrogenating the at least partially loaded hydrogen carrier medium Hx-LOHC by means of a dehydrogenation catalyst (9) to release hydrogen (H2), so that the at least partially loaded hydrogen carrier medium Hx-LOHC becomes an at least partially unloaded hydrogen carrier medium HO-LOHC, - an oxidation reactor (5) for catalytically oxidizing the at least partially unloaded hydrogen carrier medium HO-LOHC by means of an oxidizing agent to form an at least partially oxidized hydrogen carrier medium Ox-LOHC, a hydrogenation reactor (21) for reducing the at least partially oxidized hydrogen carrier medium Ox-LOHC to the at least partially loaded hydrogen carrier medium Hx-LOHC by catalytic hydrogenation, - a purification unit (23) for removing at least one oxygen-containing impurity from the at least partially loaded hydrogen carrier medium Hx-LOHC and / or from the at least partially oxidized hydrogen carrier medium Ox-LOHC.

32. The system according to claim 31, wherein: The purification unit (23) is designed as an adsorption unit.

33. The system according to claim 31 or 32, characterized in that The oxidation reactor (5) has at least one oxidant addition point (10) spaced along a reaction zone in the oxidation reactor (5) for selectively adjusting the oxygen concentration along the reaction zone.

34. The system according to claim 31, wherein: The oxidation reactor (5) is at least partially integrated in the dehydrogenation reactor (2).

35. The system according to claim 34, wherein: The oxidation reactor (5) has at least one oxidation tube (30) in which an oxidation reaction is performed, wherein the at least one oxidation tube (30) is arranged inside the dehydrogenation reactor (2).

36. The system according to claim 35, wherein: The at least one oxidation tube (30) is arranged completely inside the dehydrogenation reactor (2).

37. The system according to claim 34, wherein: The oxidation reactor (5) comprises a plurality of oxidation tubes (30) arranged in series.

38. The system according to claim 37, wherein: The oxidation reactor (5) comprises a plurality of oxidation tubes (30) arranged in series along a direction of fluid flow through the oxidation reactor (5).

39. The system according to claim 37 or 38, characterized in that The at least one oxidant addition point (10) is arranged at the transition between two oxidation tubes (30) arranged in series.

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