Method and device for the dehydrogenation of hydrogen carriers

Abstract

The present invention relates to a method and a device for dehydrogenating hydrogen carriers, said method and device making it possible to release hydrogen from hydrogenated hydrogen carriers already at low temperatures.

Description

[0001] Process and device for dehydrogenation of hydrogen carriers

[0002] The present invention comprises a method and a device for dehydrogenating hydrogen carriers, which make it possible to release hydrogen from hydrogenated hydrogen carriers even at low temperatures.

[0003] Storing hydrogen using liquid organic hydrogen carriers (LOHC) is a method for transporting and storing hydrogen with high energy density. The transported hydrogen can then be used both as a material and for energy production, regardless of its production location.

[0004] The main technological barriers to the use of liquid organic hydrogen carriers for hydrogen storage and transport are the low hydrogen storage capacity and the elevated temperature required for hydrogen release through endothermic dehydrogenation reactions.

[0005] For the technology, a dehydrated hydrogen carrier (dehyde) is first catalytically hydrogenated in an exothermic chemical reaction with hydrogen at elevated pressures between 30 bar and 50 bar and at temperatures of 150 °C to 200 °C, whereby a hydrogenated hydrogen carrier (hyd) is obtained:

[0006] Dehyd + n H2Hyd — H R

[0007] After the hydrogenated hydrogen carrier (Hyd) has been transported to its destination, the hydrogen is released again through endothermic dehydrogenation. To shift the thermodynamic equilibrium in this process step as far as possible toward the products, this step is carried out in the liquid phase at ambient or elevated pressure and at elevated temperatures between 250 °C and 320 °C. The energy input during dehydrogenation at this high temperature level is a major disadvantage of LOHC technology. To provide this heat, a portion of the hydrogen released during dehydrogenation is burned, which leads to losses of transported hydrogen and thus negatively impacts the overall efficiency of the process.

[0008] Another disadvantage of dehydrogenation in the liquid phase is that the accumulation of the dehydrated hydrogen carrier (dehyde) during the reaction favors the reversible hydrogenation reaction, which leads to a lower conversion of the dehydrogenation reaction.

[0009] Therefore, a process is needed that enables the dehydrogenation of hydrogenated hydrogen carriers in the gas phase at milder temperatures, thus allowing the coupling of alternative heat sources such as low-temperature heat, thus reducing the loss of hydrogen through partial combustion. Furthermore, the process configuration and operating conditions should be designed and optimized to maximize catalytic activity. In particular, sufficient activation energy for the dehydrogenation reaction should be provided while simultaneously preventing the accumulation of the dehydrogenation product in the reaction.

[0010] Therefore, the object of the present invention is to provide a method and a device which enable the dehydrogenation of hydrogen carriers without the above-mentioned disadvantages.

[0011] This object is achieved by a process comprising the steps a) providing a catalyst, b) providing a hydrogen carrier, c) evaporating the hydrogen carrier, d) contacting the catalyst from step a) with the evaporated hydrogen carrier from step c) at a partial pressure of the hydrogen carrier of 0.001 to 1.0 bar, whereby a dehydrogenated hydrogen carrier and hydrogen are obtained as product, and e) separating the dehydrogenated hydrogen carrier obtained in step d) from hydrogen.

[0012] Furthermore, the present invention relates to a device for dehydrogenating hydrogen carriers, comprising a reactor which is equipped with a heat source, a dosing unit and an evaporator downstream of the dosing unit, a device for reducing the partial pressure, a condenser and a separator downstream of the condenser, wherein the reactor contains a catalyst.

[0013] Further embodiments of the present invention emerge from the dependent claims.

[0014] The term “hydrogen carrier” as used herein refers to an organic compound that can absorb and release hydrogen.

[0015] The term “hydrogenated hydrogen carrier” as used herein refers to an organic compound that can release hydrogen.

[0016] The term “dehydrated hydrogen carrier” as used herein refers to an organic compound that has released or can absorb hydrogen.

[0017] As mentioned above, the present invention provides a process for dehydrogenating a hydrogenated hydrogen carrier.

[0018] According to step a) of the process according to the invention, a catalyst is provided. Any catalyst that sufficiently reduces the activation energy for the dehydrogenation of a hydrogen carrier is suitable for this purpose. Suitable catalysts are known to those skilled in the art. The catalyst preferably contains at least one transition metal and / or one transition metal compound and an oxide of a metal from main group 2 of the Periodic Table. The catalyst particularly preferably contains magnesium oxide, palladium, and platinum.

[0019] The catalyst is described in more detail below.

[0020] The hydrogen carrier provided in step b) is preferably an organic compound capable of releasing hydrogen. Thus, said hydrogen carrier is preferably a hydrogenated hydrogen carrier.

[0021] According to an exemplary embodiment of the present invention, a process for dehydrogenating a hydrogen carrier is therefore provided, comprising the steps a1) providing a catalyst, b1) providing a hydrogenated hydrogen carrier, c1) evaporating the hydrogenated hydrogen carrier, d1) contacting the catalyst from step a1) with the evaporated hydrogenated hydrogen carrier from step c1) at a partial pressure of the hydrogenated hydrogen carrier of 0.001 to 1.0 bar, a dehydrogenated hydrogen carrier and hydrogen being obtained as product, and e1) separating the dehydrogenated hydrogen carrier obtained in step d1) from hydrogen.

[0022] The hydrogen carrier provided in step b), preferably the hydrogenated hydrogen carrier, may, depending on the process, contain portions of the dehydrated form of the hydrogen carrier, i.e., the corresponding dehydrated hydrogen carrier as defined above. Accordingly, according to a further exemplary embodiment of the present invention, the hydrogen carrier is a composition comprising at least one hydrogenated hydrogen carrier.

[0023] According to a further exemplary embodiment of the present invention, a process for dehydrogenating a hydrogen carrier is accordingly provided, comprising the steps a2) providing a catalyst, b2) providing a composition comprising at least one hydrogenated hydrogen carrier, c2) evaporating the composition from step b2), d2) contacting the catalyst from step a2) with the evaporated composition from step c2) at a partial pressure of the hydrogenated hydrogen carrier of 0.001 to 1.0 bar, a dehydrogenated hydrogen carrier and hydrogen being obtained as product, and e2) separating the dehydrogenated hydrogen carrier obtained in step d2) from hydrogen.

[0024] The composition from step b2) preferably contains at least 80.0 mol%, more preferably at least 90.0 mol%, particularly preferably at least 98 mol% of the hydrogenated hydrogen carrier, based on the total weight of the composition. Accordingly, the composition preferably contains no more than 20.0 mol% of the dehydrogenated hydrogen carrier, more preferably no more than 10.0 mol%, particularly preferably no more than 2.0 mol%, based on the total weight of the composition.

[0025] Since the process according to the invention is carried out in the gas phase, the hydrogen carrier, preferably the hydrogenated hydrogen carrier, has a boiling point at atmospheric pressure (1.013 bar) of 200°C or less. In particular, it is preferred that the hydrogen carrier, preferably the hydrogenated hydrogen carrier, has a boiling point at atmospheric pressure (1.013 bar) in the range from 80 to 200°C, more preferably from 100 to 150°C, particularly preferably from 110 to 135°C.

[0026] For the process according to the invention, it is also advantageous if the resulting dehydrogenated hydrogen carrier has a boiling point at atmospheric pressure (1.013 bar) of 200°C or less, in order to avoid condensation of the reaction product in the reactor, the feed lines, or in the pores of the catalyst. Thus, it is preferred that the dehydrogenated hydrogen carrier has a boiling point at atmospheric pressure (1.013 bar) in the range of 80 to 200°C, more preferably 100 to 180°C, and particularly preferably 110 to 150°C.

[0027] Preferably, the hydrogen carrier, preferably the hydrogenated hydrogen carrier, is a substituted or unsubstituted linear, cyclic or heterocyclic hydrocarbon.

[0028] Even more preferably, the hydrogen carrier, preferably the hydrogenated hydrogen carrier, is an N-heterocyclic hydrocarbon, particularly preferably a substituted or unsubstituted piperidine.

[0029] Particularly preferably, the hydrogen carrier, preferably the hydrogenated hydrogen carrier, is 2,5-dimethylpiperidine.

[0030] In step c) of the process according to the invention, the hydrogen carrier, preferably the hydrogenated hydrogen carrier, is evaporated. Dehydrogenation in the gas phase reduces mass transport limitations on the catalyst and thus increases the reaction rate and space-time yield in the process.

[0031] The term "evaporation" as used herein refers to the phase transition from a liquid to the gas phase above the liquid's boiling point. According to a preferred embodiment of the present invention, the process takes place entirely in the gas phase.

[0032] Accordingly, in step c) of the process according to the invention, at least 90% by weight, preferably at least 95% by weight, more preferably at least 99% by weight, particularly preferably 100% by weight of the hydrogen carrier is evaporated, based on the total weight of the hydrogen carrier.

[0033] Optionally, the hydrogen carrier, preferably the hydrogenated hydrogen carrier or the

[0034] A carrier gas may be added to the composition from step b2) in step c), c1), or c2) to reduce the partial pressure. The carrier gas is preferably nitrogen, carbon dioxide, hydrogen, water vapor, or mixtures thereof.

[0035] Subsequently, in step d), the vaporized hydrogen carrier, preferably the vaporized hydrogenated hydrogen carrier, is brought into contact with the catalyst, whereby hydrogen and the dehydrogenated form of the hydrogen carrier are obtained.

[0036] The yield of the dehydrogenation reaction can be increased by reducing the pressure, since under these conditions the equilibrium is shifted toward the dehydrogenation product. Therefore, according to the invention, the dehydrogenation according to step d) is carried out at a partial pressure of the hydrogen carrier, preferably the hydrogenated hydrogen carrier, of 0.001 to 1.0 bar, preferably 0.01 to 0.8 bar, more preferably 0.05 to 0.2 bar.

[0037] According to a preferred embodiment of the invention, the dehydrogenation according to step d) is carried out at a temperature of 100 to 400 °C, preferably at a temperature of 120 to 250 °C, more preferably at a temperature of 100 °C to less than 250 °C, particularly preferably at a temperature of 120 to 200 °C. This low temperature level enables the coupling of low-temperature heat and the omission of partial combustion of the hydrogen obtained, whereby a smaller proportion of the hydrogen stored in the hydrogen carrier is lost.

[0038] According to a particularly preferred embodiment of the present invention, the dehydrogenation according to step d) is carried out at a temperature of 100 to 180 °C and an absolute pressure of 0.05 to 1.0 bar.

[0039] In step e) of the process according to the invention, the hydrogen obtained in step d) is separated from the dehydrogenated hydrogen carrier.

[0040] According to a preferred embodiment, the process according to the invention further comprises a step f), wherein the hydrogen obtained in step e) is stored and / or utilized.

[0041] The term "storage" as used herein refers to the reversible storage of hydrogen. Storage according to the present invention is preferably carried out by compressed gas storage, liquefied gas storage, metal hydride storage, absorption, adsorption, and / or chemical bonding of the resulting hydrogen.

[0042] The term “recovery” as used herein refers to the use of

[0043] Hydrogen is used in processes where hydrogen is chemically converted into other compounds. Hydrogen can be used as an energy carrier, for example, as fuel or in fuel cells, in chemical reactions, such as hydrogenation and reduction, in steel production using direct reduction, or in ammonia production.

[0044] The present invention further relates to a device for dehydrogenating hydrogen carriers.

[0045] Figure 1 shows a schematic representation of the device according to the invention. The device consists of a module in which the hydrogenated hydrogen carrier is metered into the process. The medium is then converted into the gas phase in an evaporator. In the reactor with a heat source, dehydrogenation takes place at low pressure, optionally under reduced pressure, preferably over a catalyst that already exhibits high activity for the dehydrogenation reaction at temperatures below 200 °C. The reduced pressure in the reactor is optionally achieved within the framework of a further, optional module for pressure reduction. The dehydrogenated hydrogen carrier is then condensed to enable phase separation of the released hydrogen from the dehydrogenated hydrogen carrier in a separator.

[0046] The device according to the invention comprises a device for reducing the partial pressure. Carrying out the dehydrogenation at reduced pressure has the advantage of shifting the thermodynamic equilibrium toward the dehydrogenated hydrogen carrier. Preferably, said device is a vacuum generator and / or a recycling unit for introducing a carrier gas.

[0047] Figure 2 shows an exemplary embodiment of the device according to the invention, wherein the device for reducing the partial pressure is a vacuum generator (4). Particularly preferably, the vacuum generator (4) is a vacuum unit (4a). According to the invention, any reactor having a heat source capable of generating temperatures in the range from 100 to 400°C can be used as the reactor (1). Suitable reactors are known to those skilled in the art. Preferably, the reactor (1) is a gas-phase reactor or a flow-through reactor. The reactor (1) is equipped with a metering unit (2) that metered the hydrogenated hydrogen carrier into the process. Preferably, the metering unit (2) is a throttle. Before the hydrogenated hydrogen carrier is fed to the reactor, it must be converted into the gas phase. For this purpose, an evaporator (3) is arranged downstream of the metering unit (2), preferably the throttle.The evaporator (3) is located upstream of the reactor (1). The reaction mixture removed from the reactor (1), which contains hydrogen and the dehydrogenated hydrogen carrier, is fed to the vacuum generator (4), preferably the vacuum unit (4a), which is located downstream of the reactor (1), and is then converted into the liquid phase in the condenser (5). As part of the process design, heat integration between the evaporator (3) and condenser (5) can be carried out in order to reduce the heat input into the gas phase. The combination of evaporator (3) and condenser (5) therefore preferably comprises a heat exchanger (7) that thermally connects the stream of hydrogenated hydrogen carrier upstream of the reactor (1) with the stream of dehydrogenated hydrogen carrier from the reactor (1). The hydrogen is then separated from the dehydrogenated hydrogen carrier in a separator (6) located downstream of the condenser (5) or heat exchanger (7).

[0048] According to a preferred embodiment of the present invention, at least one storage unit and / or at least one utilization unit for hydrogen is connected downstream of the separator (6).

[0049] Preferably, the at least one storage unit is a compressed gas storage unit, a liquid gas storage unit, a metal hydride storage unit, an absorption storage unit, an adsorption storage unit or several of these.

[0050] The at least one utilization unit is preferably a reactor for the chemical conversion of hydrogen. The reactor is preferably a fuel cell, a hydrogenation reactor, a smelting reactor, a Haber-Bosch reactor, or several of these.

[0051] In another exemplary embodiment of the invention, a Venturi nozzle (8) is used to generate the negative pressure in the reactor (1). The arrangement is shown in Figure 3. For this purpose, the product of the process is circulated using a compressor (9). A portion of this recycle gas is continuously withdrawn via a control valve (10), fed to the heat exchanger (7) for condensation, and then separated. The advantage of this arrangement lies in the possibility of using a pressure compressor instead of a vacuum pump, which can contribute to increasing process reliability and controllability.

[0052] According to a further exemplary embodiment of the invention, a Venturi nozzle (8) is connected downstream of the reactor (1), which is followed by a compressor (9), the outlet of which is in turn connected to the Venturi nozzle (8), so that a circuit comprising the Venturi nozzle (8) and the compressor (9) is created. A control valve (10) is connected downstream of the circuit, which is connected downstream to a heat exchanger (7). The flow of hydrogenated hydrogen carrier upstream of the reactor (1) is thermally connected via a heat exchanger (7) to the flow of dehydrogenated hydrogen carrier from the reactor (1). A separator (6) is connected downstream of the heat exchanger (7).

[0053] According to a further embodiment of the invention, the partial pressure can also be reduced by introducing a carrier gas into the system. For this purpose, a recycling unit is used instead of the vacuum generator (4) as shown in Figure 4. This preferably comprises a connection between the stream of separated hydrogen and the stream of hydrogenated hydrogen carrier upstream of the reactor (1) via a mixer (11) arranged upstream of the evaporator (3) or the heat exchanger (7). Using a control valve (12), a partial stream of the separated hydrogen can be fed to the stream of hydrogenated hydrogen carrier via the mixer (11), thereby reducing the partial pressure of the hydrogenated hydrogen carrier. Alternatively or additionally, a carrier gas can also be fed via the control valve (12).

[0054] The carrier gas is preferably nitrogen, carbon dioxide, hydrogen, water vapor or mixtures of these.

[0055] According to a preferred embodiment, the recycling unit, as shown in Figures 4a, 5a, and 6a, can comprise a separation unit (13) downstream of the separator (6) for separating the separated hydrogen from the carrier gas. Preferably, the carrier gas according to this embodiment contains no hydrogen. Accordingly, the carrier gas according to this embodiment is selected from nitrogen, carbon dioxide, water vapor, and mixtures thereof. The at least one storage unit and / or at least one utilization unit for hydrogen present according to a preferred embodiment is preferably downstream of the separation unit (13).

[0056] Furthermore, according to a further preferred embodiment of the invention, the reactor comprises a membrane unit. From a reactor with a membrane unit, the hydrogen obtained from the dehydrogenation of the hydrogen carrier can be removed, thereby increasing the equilibrium conversion of the reaction. Suitable membrane units for separating hydrogen are known to those skilled in the art. Also according to this embodiment, the carrier gas preferably contains no hydrogen. Accordingly, the carrier gas, also according to this embodiment, is selected from nitrogen, carbon dioxide, water vapor, and mixtures thereof.

[0057] According to a further embodiment of the invention, as shown in Figures 5 and 6, a combination of a vacuum generator and a recycling unit can also be used to reduce the partial pressure. The device according to this embodiment of the invention comprises, in addition to the above-described recycling unit, the vacuum generator (4) downstream of the reactor. The latter can be a vacuum unit (4a) downstream of the reactor (Figure 5) or the above-described combination of a Venturi nozzle (8) and a compressor (9) (Figure 6).

[0058] As mentioned above, both the process and the apparatus according to the invention comprise a catalyst. The activity of the catalyst is independent of thermal deactivation due to the low reaction temperature. Furthermore, the reduced pressure prevents condensation of the hydrogen carrier in the pore structure of the catalyst, which contributes to an increase in the reaction rate at low temperatures.

[0059] The catalyst preferably contains a support material containing palladium, platinum, and a magnesium compound. The catalyst components are preferably applied to the support material.

[0060] The catalyst particularly preferably comprises i) 75.0 to 95.0 wt.%, preferably 77.0 to 90.0 wt.%, more preferably 78.0 to 88.0 wt.%, even more preferably 79.0 to 86.0 wt.% of at least one support material, based on the total weight of the catalyst, ii) 4.0 to 22.0 wt.%, preferably 7.0 to 20.0 wt.%, more preferably 8.0 to

[0061] 18.0 wt.%, more preferably 9.0 to 16.0 wt.% magnesium oxide, based on the total weight of the catalyst, iii) 1.0 to 5.0 wt.%, preferably 1.5 to 4.0 wt.%, more preferably 2.0 to

[0062] 3.5 wt.%, more preferably 2.2 to 3.2 wt.% of palladium, based on the total weight of the catalyst, and iv) 1.0 to 5.0 wt.%, preferably 1.5 to 4.0 wt.%, more preferably 2.0 to

[0063] 3.5 wt.%, more preferably 2.1 to 3.0 wt.% platinum, based on the total weight of the catalyst, the addition of the percentages of the individual components giving 100.0 wt.%.

[0064] In the catalyst according to the invention, the weight ratio between palladium and platinum Pd:Pt is preferably 3.0:1.0 to 1.0:3.0, more preferably 2.9:1.5 to 1.5:2.9, even more preferably 2.7:2.0 to 2.0:2.7. The weight ratio between palladium and platinum Pd:Pt is particularly preferably 2.72:2.51.

[0065] According to a preferred embodiment, the magnesium compound is magnesium oxide (MgO) and / or the support material is gamma-aluminum oxide (γ-Al2O3). The present invention provides a process and apparatus for dehydrogenation in the gas phase at low pressure or even under reduced pressure. This allows the mass transport limitations in the liquid phase to be circumvented and allows for higher reaction kinetics during dehydrogenation.

[0066] Dehydrogenation in the gas phase also reduces mass transport limitations at the catalyst, thus increasing the reaction rate and space-time yield in the process. Furthermore, the reduced pressure during the synthesis increases the thermodynamic equilibrium in the dehydrogenation reaction. Figure 7 shows the conversion of the dehydrogenation of 2,6-dimethylpiperidine as a function of pressure and temperature, with the conversion of the reaction being highest at low pressures and in the lower temperature range. The reaction can thus be carried out at lower temperatures, allowing the coupling of low-temperature heat into the process, which can be generated, for example, using heat pumps.

[0067] Figure 8 shows the conversion of the dehydrogenation of 2,6-dimethylpiperidine as a function of pressure and temperature. Unlike Figure 7, however, a N2 content of 66.67% in the feed gas was considered in this case. The increased conversion with inert gas demonstrates the positive effect of a carrier gas on the conversion of the dehydrogenation reaction.

[0068] In the following, the implementation of the process according to the invention using the catalysts described above is described using examples.

[0069] Examples

[0070] Production of catalysts

[0071] Materials

[0072] Palladium(II) acetate ([Pd(OAC)2]3, >99.9% trace metals basis, Sigma-Aldrich), tetraammine palladium(II) nitrate solution (Pd(NH3)4(NO3)2, 4.608 wt.% in H2O, 99.99%, Sigma-Aldrich), palladium(II) nitrate hydrate (Pd(NOs)2 x H2O, 99.95%, based on metal, ChemPUR) and platinum(II) nitrate (Pt(NO3)2, 99.95% based on metal, ChemPUR), tetraammine platinum(II) nitrate (Alfa Aesar) and magnesium nitrate hexahydrate (Mg(NOs)2 x 6H2O, ACS 98.0-102.0%, Alfa Aesar) were used for catalyst preparation. Gamma-alumina (Y-Al2O3 Balls 2.5 mm, BET=210 m 2 / g, Sasol) was used to prepare magnesium-containing support materials. Cis-2,6-dimethylpiperidine (C7H15N, >99.0% purity, TCI) and 2,6-lutidine (2,6-dimethylpyridine, C7H9N, >99.0% purity, Sigma-Aldrich) were used as reagents. Ethanol (95 vol%, Fischer Scientific), acetone (>99.7%, Fischer Scientific), and deionized water were used without further purification. Ultrapure (99.999%) nitrogen and hydrogen gas were used for the reactions.

[0073] Carrier materials

[0074] General procedure for the preparation of MgO-modified Y-AI2O3

[0075] 1) 60g Sasol Gamma Alumina (ball size 2.5mm / 210m 2 / g) are placed on a glass plate and then dried at 110 °C for at least 12 hours.

[0076] 2) After drying, the material is transferred to a 1 L flask and the flask is immediately covered with Parafilm.

[0077] 3) The flask is then vacuumed to 20 mbar on a rotary evaporator at 50 rpm and 50 °C for at least 30 minutes.

[0078] 4) A 0.72 molar magnesium nitrate solution is prepared by dissolving 20.2 g of magnesium nitrate hexahydrate in deionized water to achieve a final volume of 1 10 mL of clear solution.

[0079] 5) The magnesium solution is added to the flask connected to the rotary evaporator via a Teflon tube at a higher pressure of approximately 100 mbar. The addition should be carried out in a single step and within a short time.

[0080] 6) Then, the pressure of the rotary evaporator is reduced again to 77 mbar while rotating at 50 rpm and 50 °C. Rotation can be faster (130 rpm) to obtain a smaller amount of carrier and a smaller flask, and to remove particles adhering to the flask wall.

[0081] 7) After one hour, the pressure is slowly reduced to 50 mbar and waited for 30 minutes, then to 20 mbar; the solution will be completely evaporated after 30 minutes or even sooner. 8) The dried catalyst support is then mixed and dried for another 20-30 minutes.

[0082] 9) The dried catalyst support is cooled to room temperature and the pressure is slowly increased to atmospheric pressure.

[0083] 10) The material is transferred to a glass plate and allowed to rest at room temperature for 5-6 hours. It is then dried again at 110 °C for 5-12 hours.

[0084] 1 1) The support materials are then calcined in a calcining furnace at 500 °C for 3 hours. The heating rate is 10 °C / min.

[0085] Example 1

[0086] Magnesium-containing aluminum oxide powder (Mg-AfeOs)

[0087] The magnesium-containing alumina powder was prepared by initial wet impregnation of gamma alumina with an aqueous solution of magnesium nitrate.

[0088] Gamma alumina spheres 2.5 / 210 were crushed and sieved to a particle size of 125-250 μm and dried overnight at 110 °C prior to impregnation. To obtain a support material with a nominal magnesium oxide (MgO) loading of 16 wt.%, a solution of 1.21 g of Mg(NO3)2 x 6 H2O in 6.6 mL of deionized water was prepared for each 1 g of the alumina to be impregnated. The prepared solution was added dropwise to the alumina support with intermittent mixing. The resulting paste was dried at room temperature for 5-6 h and then at 110 °C overnight, followed by calcination for 3 h at 500 °C (10 °C / min heating rate) in static air.

[0089] Analogously, support materials with nominal loadings of 5, 10 and 15 wt% magnesium oxide were prepared using the following aqueous solutions of Mg(NO3)2 x 6 H2O for each 1 g of the alumina to be impregnated:

[0090] Example 2

[0091] Magnesium-containing aluminum oxide spheres

[0092] The magnesium-containing alumina spheres were prepared by slurry impregnation of gamma alumina (2.5 / 210 spheres dried at 110 °C overnight prior to impregnation) with an aqueous solution of magnesium nitrate. 40 g of gamma alumina spheres 2.5 / 210 were used as support material without crushing or sieving. After drying at 110 °C for 12 h, the alumina material was vacuum-evaporated in a rotary evaporator under 20 mbar at 50 °C and 50 rpm for at least 30 min. A magnesium solution (0.72 mol / L) was prepared by dissolving 22.2 g of Mg nitrate hydrate in 115 mL of deionized water to achieve a final volume of 125 mL of clear solution. The metal solution was then added to the flask through a Teflon tube, while the pressure was adjusted to 100 mbar. After the solution was added, the pressure was further reduced to 77 mbar at 50 rpm and 50 °C.After 1 h, the pressure was slowly reduced to 50 mbar and after 30 min further to 20 mbar. The pressure was reduced again under these conditions until the solution completely evaporated. The resulting magnesium-containing support material was left to stand at room temperature for 5-6 h and then dried overnight at 110 °C before being calcined in static air for 3 h at 500 °C at a heating rate of 10 °C / min.

[0093] Catalysts Example 3 Palladium-platinum on magnesium-containing alumina powder, prepared from palladium(II) acetate and platinum(II) nitrate

[0094] A bimetallic palladium-platinum catalyst supported on magnesium-containing alumina (Example 1) was prepared by incipient wet co-impregnation of a single non-aqueous solution of palladium(II) acetate and platinum(II) nitrate. The nominal metal loading was 2.7 wt% Pd and 2.5 wt% Pt, resulting in an approximate Pd:Pt atomic ratio of 2:1 for the bimetallic catalysts. Palladium acetate and platinum nitrate solutions were prepared separately in different solvents to avoid precipitation of Pd and Pt species. Acetone was used as the solvent to dissolve palladium acetate, and platinum nitrate was dissolved in ethanol. To synthesize 2 g of the catalyst, about 0.1122 g of palladium(II) acetate was mixed with about 7 g of acetone using an ultrasonic bath to obtain a solution without visible species or particles.Separately, approximately 0.0797 g of platinum(II) nitrate was dissolved in 1.2 g of ethanol to obtain a solution devoid of visible species. The Pd solution was then added to the Pt solution and thoroughly mixed, resulting in a bimetallic solution with no signs of deposition or precipitation, or the formation of visible species. The resulting bimetallic solution was then added dropwise to approximately 1.898 g of support materials in several steps (approximately 1.5 ml was added to the support material each time to achieve incipient wetness) with intermittent stirring and interval drying at room temperature for several minutes (5-10 min). The synthesized catalysts were dried at room temperature for at least 2 h and then at 110 °C overnight. The materials were then calcined in static air at 400 °C for 2 h at a heating rate of 10 °C / min. Note: Palladium acetate is insoluble in water and very slightly soluble in ethanol.On the other hand, platinum nitrate is soluble in acetone, water, and ethanol, but precipitates with palladium acetate. Therefore, it is very important to prepare the Pd and Pt solutions separately in acetone and ethanol, respectively, and then mix them into a stable solution. Otherwise, they will precipitate even if dissolved separately in acetone and then mixed. Furthermore, this bimetallic solution may not be suitable for slurry impregnation, and especially for impregnation at elevated temperatures, even at 50 °C, or under vacuum. This is because in the presence of ethanol, Pt / Pd species are reduced to metallic states, as indicated by the formation of a black color solution, and most likely form large particles.

[0095] Example 4 Palladium-platinum on magnesium-containing alumina powder catalyst prepared from palladium(II) nitrate hydrate and platinum(II) nitrate:

[0096] Bimetallic palladium-platinum catalyst supported on magnesium-containing alumina (Example 1) was prepared by incipient wet co-impregnation of a single aqueous solution of palladium(II) nitrate hydrate and platinum(II) nitrate in deionized water. The nominal metal loading was 2.7 wt% Pd and 2.5 wt% Pt, resulting in an approximate Pd:Pt atomic ratio of 2:1 for the bimetallic catalysts. To synthesize 1 g of bimetallic catalyst, 0.065 g of palladium(II) nitrate hydrate was mixed with 0.08 g (500 μL) of nitric acid (HNO3, 65%) and 1.2 mL of deionized water at room temperature in an ultrasonic bath to form a cloudy solution. 0.041 g of platinum(II) nitrate was then added to this solution and thoroughly mixed. The resulting bimetallic solution was then added dropwise to about 0.95 g of support material (Example 1) in a single step with intermittent stirring to achieve initial wetness.The resulting paste was dried for at least 2 h at room temperature and then overnight at 110 °C. The materials were then calcined in static air for 2 h at 400 °C and a heating rate of 10 °C / min.

[0097] Note: Palladium(II) nitrate hydrate forms a cloudy solution in water with the aid of dilute nitric acid. Higher concentrations of nitric acid do not improve the low solubility of palladium(II) nitrate hydrate.

[0098] Example 5 Palladium-platinum catalyst on magnesium-containing alumina powder, prepared from aqueous tetraamminepalladium(II) nitrate solution and tetraammineplatinum(II) nitrate:

[0099] Bimetallic palladium-platinum catalyst on magnesium-containing alumina powder (Example 1) (PchPti / Mgie-AhOs) was prepared by initial wet co-impregnation of an aqueous solution of tetraamminepalladium(II) nitrate solution (containing 4.608 wt% Pd) and tetraammineplatinum(II) nitrate. The nominal metal loading is 2.7 wt% Pd and 2.5 wt% Pt, resulting in an approximate Pd:Pt atomic ratio of 2:1 for the bimetallic catalyst. To obtain 1 g of the bimetallic catalyst, approximately 0.0488 g of tetraammineplatinum(II) nitrate was dissolved in 0.5772 g of tetraamminepalladium(II) nitrate solution and 0.6 mL of deionized water. The resulting bimetallic solution was then added dropwise to approximately 0.95 g of support material (Example 1) in a single step with intermittent stirring to achieve initial wetness. The resulting paste was dried at room temperature for at least 2 hours and then at 110 °C overnight.The dried material was then calcined in static air at 400 °C for 2 h at a heating rate of 10 °C / min.

[0100] Example 6

[0101] Palladium-platinum on magnesium-containing alumina spheres. Catalyst prepared from aqueous tetraamminepalladium(II) nitrate solution and tetraammineplatinum(II) nitrate: A bimetallic palladium-platinum catalyst on magnesium-containing alumina spheres (Example 2) was prepared by slurrying an aqueous solution of tetraamminepalladium(II) nitrate solution and tetraammineplatinum(II) nitrate. 4.745 g of Mg-alumina spheres according to Example 2 were used as support material. To achieve the nominal loadings of 2.7 wt% Pd and 2.5 wt% Pt in 5 g of catalyst (resulting in a Pd:Pt atomic ratio of 2:1), 0.244 g of tetraammineplatinum(II) nitrate was dissolved in 2.88 g of tetraamminepalladium(II) nitrate solution in deionized water to achieve a final volume of 12 mL. The metal solution was then added in a single step via a Teflon tube to the flask containing the support material while the pressure was adjusted to 100 mbar.After adding the solution, the pressure was slowly reduced to 77 mbar while the flask rotated at 50 rpm and 50 °C. After 1 h, the pressure was slowly reduced to 50 mbar and after 30 min, further to 20 mbar. The pressure was maintained under these conditions until the solution completely evaporated. The resulting material was allowed to stand for 5-6 hours at room temperature and then dried overnight at 110 °C before being calcined for 2 hours at 400 °C at a heating rate of 10 °C / min in static air.

[0102] Example 7 Palladium-platinum on magnesium-containing alumina spheres Catalyst prepared from aqueous tetraamminepalladium(II) nitrate solution and tetraammineplatinum(II) nitrate with controlled pH:

[0103] Bimetallic palladium-platinum catalyst on magnesium-containing alumina spheres (Example 2) was prepared by slurrying an aqueous solution of tetraamminepalladium(II) nitrate solution and tetraammineplatinum(II) nitrate. To achieve the nominal loadings of 2.66 wt% Pd and 2.5 wt% Pt in 5 g of catalyst (resulting in a Pd:Pt atomic ratio of 2:1), 0.244 g of tetraammineplatinum(II) nitrate was dissolved in 2.88 g of tetraamminepalladium(II) nitrate solution. The pH of the solution was adjusted with 30% ammonium hydroxide solution to achieve a pH of 10.5 at 50 °C while mixing at 200 rpm. 4.745 g of magnesium-containing aluminum oxide spheres according to Example 2 were used as support material without crushing or sieving. The support material was placed in a beaker containing a solution of tetraamminepalladium(II) nitrate and tetraammineplatinum(II) nitrate.The slurry was mixed under the above conditions for one hour at a controlled pH of 10.5 by dropwise addition of 30% ammonium hydroxide solution. After one hour, the slurry was transferred to a rotary evaporator, and the solution was evaporated by gently reducing the pressure to less than 100 mbar, then 50 mbar, and finally 20 mbar. The solution was maintained under these conditions until complete evaporation. The resulting material was left to stand at room temperature for 5-6 hours and then dried overnight at 110 °C before being calcined at 400 °C for 2 hours at a heating rate of 10 °C / min in static air.

[0104] Dehydration

[0105] Example 8

[0106] Gas-phase dehydrogenation of 2,6-dimethylpiperidine:

[0107] The synthesized catalysts were tested in the gas-phase dehydrogenation of 2,6-dimethylpiperidine at reaction temperatures of 150, 175, 200, 225, 250, 275, and 300 °C under atmospheric pressure in a fixed-bed flow reactor. For each experiment, approximately 0.27 g of catalyst (sieved to 150-250 pm) was diluted with 5 g of silicon carbide (120 mesh) and loaded into a stainless steel reactor (L = 55 cm, id = 1 cm) to achieve a catalyst bed length of approximately 7 cm. The axial and radial temperature gradients in the catalyst bed were measured to be negligible. Before each measurement, the catalyst was subjected to a 1-hour in-situ reduction with hydrogen (50 ml / min, 10% H2 in N2) at 350 °C or 250 °C.The reactor was then cooled to the reaction temperature with a N2 flow of 50 ml / min, and then liquid 2,6-dimethylpiperidine was fed into the reactor from below using an HPLC pump at 0.1 ml / min (16.8 ml / min vapor) in a mixture with 50 ml / min N2 as carrier gas to achieve a SV (space velocity) of 15000 tr. 1 The partial pressure of 2,6-dimethylpiperidine was 250 mbar. The reaction products were identified online by gas chromatography coupled with mass spectrometry (GC-MS), as well as with a flame ionization detector (FID), and a thermal conductivity detector (TCD). Additionally, hydrogen production was measured with a calibrated TCD detector.

Claims

Claims 1 . A process for dehydrogenating a hydrogen carrier, comprising the steps of a) providing a catalyst, b) providing a hydrogen carrier, c) evaporating the hydrogen carrier, d) contacting the catalyst from step a) with the evaporated Hydrogen carrier from step c) at a partial pressure of the hydrogen carrier of 0.001 to 1.0 bar, whereby a dehydrogenated hydrogen carrier and hydrogen are obtained as product, and e) separating the dehydrogenated hydrogen carrier obtained in step d) from hydrogen.

2. The method according to claim 1, further comprising step f) storing and / or utilizing the hydrogen obtained in step e).

3. The process according to claim 1 or 2, wherein in step c) at least 90 wt.%, preferably at least 95 wt.%, more preferably at least 99 wt.%, particularly preferably 100 wt.% of the hydrogen carrier is evaporated, based on the total weight of the hydrogen carrier.

4. The process according to any one of claims 1 to 3, wherein a carrier gas is supplied to the vaporized hydrogen carrier in step c).

5. The method according to claim 4, wherein the carrier gas is nitrogen, carbon dioxide, hydrogen, water vapor and mixtures thereof.

6. The process according to any one of claims 1 to 5, wherein step d) is carried out at a temperature of 100 to less than 250 °C.

7. The process according to any one of claims 1 to 5, wherein step d) is carried out at a temperature of 100 to 200 °C.

8. A process according to any one of claims 1 to 4, wherein the hydrogen carrier is a substituted or unsubstituted linear, cyclic or heterocyclic hydrocarbon.

9. A process according to any one of claims 1 to 5, wherein the hydrogen carrier is a substituted or unsubstituted piperidine.

10. A process according to any one of claims 1 to 6, wherein the catalyst comprises a support material, magnesium oxide, palladium and platinum.

11. Apparatus for dehydrogenating hydrogen carriers, comprising a reactor equipped with a heat source, a dosing unit and an evaporator downstream of the dosing unit, a device for reducing the partial pressure, a condenser and a separator downstream of the condenser, the reactor containing a catalyst.

12. Apparatus according to claim 11, wherein the evaporator is arranged upstream of the reactor.

13. Device according to claim 11 or 12, wherein a storage unit and / or a utilization unit for hydrogen is connected downstream of the separator.

14. Device according to one of claims 11 to 13, wherein the device for reducing the partial pressure is a vacuum generator (4) and / or a recycling unit for introducing a carrier gas.

15. Apparatus according to claim 14, wherein the recycling unit comprises a connection between the stream of separated hydrogen with the stream of hydrogenated hydrogen carrier upstream of the reactor (1) via a mixer (11) upstream of the evaporator (3).

16. Device according to claim 14 or 15, wherein the recycling unit comprises a separation unit (13) downstream of the separator (6) for separating the separated hydrogen from the carrier gas.

17. Device according to one of claims 11 to 16, wherein the evaporator (3) and the condenser (5) are a heat exchanger (7) which thermally connects the flow of the hydrogen carrier supplied to the reactor (1) with the flow of the dehydrated hydrogen carrier from the reactor (1).

18. Device according to one of claims 11 to 17, wherein the vacuum generator (4) is a Venturi nozzle (8) followed by a compressor (9), the outlet of which in turn is connected to the Venturi nozzle (8) in connection, so that a circuit comprising the Venturi nozzle (8) and the compressor (9) is created.

19. Apparatus according to any one of claims 11 to 18, wherein the reactor comprises a membrane unit.

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