Fast dynamically responsive ammonia synthesis or cracking for h2 storage utilising structured magnetically-heated catalysts

Abstract

This invention relates to a method for quickly tunable on-demand gas phase reactions of ammonia decomposition to produce hydrogen and nitrogen gas and reversible reaction of ammonia synthesis from hydrogen and nitrogen gas by use of magnetic heating, the corresponding catalyst materials, their preparation procedures and a reactor system designed specifically for gas-phase magnetic catalysis.

Description

[0001] Fast Dynamically Responsive Ammonia Synthesis or Cracking for H2 Storage Utilising Structured Magnetically-heated Catalysts

[0002] FIELD OF INVENTION

[0003] This invention relates to a method for quickly tunable on-demand gas phase reactions of ammonia decomposition to produce hydrogen and nitrogen gas and reversible reaction of ammonia synthesis from hydrogen and nitrogen gas by use of magnetic heating, the corresponding catalyst materials, their preparation procedures and a reactor system designed specifically for gas-phase magnetic catalysis.

[0004] BACKGROUND

[0005] Continuous increase in use of fossil fuels has led to a significant environmental footprint and in recent years, focus has been shifted towards renewable carbon-free energy sources, one of more prominent being hydrogen most notably for use in fuel cells. The issue with hydrogen is its severe volatility and danger of storage under high- pressure conditions. Hence, there is a need for techniques, which bind hydrogen into stable molecules that can be decomposed when so required. One promising possibility is based on ammonia (NH3) as a storage medium featuring a generous hydrogen- bearing capability (17.8 wt.%) while being able to liquefy at a low pressure, 8.6 bar at 20 °C.

[0006] To retrieve stored hydrogen, catalytic decomposition of ammonia takes place on catalytic surfaces, e.g., Ru, at elevated temperatures and atmospheric pressure:

[0007] 2NH3N2+ 3H2

[0008] The synthesis reaction is exothermic however, it proceeds at elevated temperature (300 °C - 600 °C and pressures in the range in between 50 bar and 300 bar), and thus a form of heating of catalyst bed combined with intercooling is required. The decomposition reaction is endothermic, therefore a form of heating is required. Normally, resistance heaters are used due to simplicity and efficiency, however, reaching the desired temperature can take extended periods of time. Induction heating is a form of contactless energy transfer and on-spot heat generation already in use for magnetic treatment of hyperthermia. By passing alternating current (AC) through a coil, a magnetic field is generated within. Electronically speaking, the circuit is a high-power LC oscillator. For this purpose, the operating frequency ranges between approximately 100-300 kHz. When an electrically conductive sample is placed in an oscillating magnetic field, eddy currents are induced. Because of resistance, the material heats up which can be observed in bulk metal samples as is the case with domestic induction cookers. For the purpose of this invention, a ferromagnetic susceptor material, which features distinctive magnetization (M / H) profiles is prepared instead. Heating occurs solely on the account of hysteresis losses (Hojlund et al., “Energy storage employing ammonia dissociation by use of inductive heating and synthesis”, WO2017 / 186614).

[0009] Hysteresis curves are measured using a Vibrating Sample Magnetometer (VSM) and are characterized by several parameters. Depending on its surface and shape, heating capabilities can be estimated. Remnant magnetization (Mr) is the magnetization retained by the material in its magnetically saturated state (Ms) succeeding the removal of external magnetic field (H = 0). The coercive field (He) is the magnetic field required to demagnetize the sample. Mr and Hcare parameters, which describe the shape and surface of the hysteresis loop. Furthermore, its surface is proportional to the amount of heat dissipated during the sample magnetization reversal. A larger area corresponds to a higher energy absorption rate and as a result, greater heat production. In addition to a high magnetization value, a material featuring significant remnant magnetization will allow for better heating. Steep hysteresis curves are preferred.

[0010] Magnetic heating of catalysts was previously demonstrated for liquid-phase batch applications. A two-part magnetic support material comprised of magnetite cores embedded within a high-surface y-alumina matrix was decorated with Ru nanoparticles. Specifically, the composite catalyst was used for hydrogenation of furfural in a pressurized quartz vessel (Gyergyek et al., “A hierarchical Ru-bearing alumina / magnetic iron-oxide composite for the magnetically heated hydrogenation of furfural”, Green Chem., 2020, 22, 5978-5983, DOI 10.1039 / D0GC00966K).

[0011] International patent application WO2020 / 254184 discloses ferromagnetic catalyst support for induction heated catalysis. Most notably, endothermic reactions can be catalyzed by use of ferromagnetic cores encapsulated in an oxide shell. The shielded magnetic particles are mixed with a ceramic material and sintered to serve as a support material (1-100 m2) for catalytic nanoparticles. Various metals (Ni, Co, Ru, Rh, Pt, Pd, Fe, Cu, Sn, Ir, Ga) can be adhered using impregnation to serve various needs such as hydrogen cyanide synthesis, dehydrogenation, methanol cracking, ammonia cracking, steam reforming and the water gas shift reaction.

[0012] Similarly, International patent application WO2017 / 186608 discloses ferromagnetic materials for induction heated catalysis relating to endothermic reactions. A porous ferromagnetic susceptor with a spinel, inverse spinel or perovskite-type structure is used and features a surface area of 5-100 m2combined with a Curie temperature of above 650 °C. Such porous susceptor is impregnated with catalytically active particles or elements. Ni, Ru, Rh, a combination of Ni and Co and a combination of Mn and Zr are proposed. Ni, optionally in combination with Co, is suitable for catalyzing steam and tar reforming reactions, whilst a combination of Mn and Zr is used for catalyzing the reverse water gas shift reaction. The induction coil can be placed within or around the reactor unit while the system is pressurized or at ambient pressure. If the coil is positioned within the reactor, the windings may come into direct contact with the catalyst material. In this case, the catalyst material may be heated directly by resistive heating in addition to induction heating. The reactor unit and, if present, the pressure shell, are typically made of non-ferromagnetic materials.

[0013] In the research underlying the present invention, efforts were made to make NH3 more attractive as a hydrogen storage means by seeking improved ways to promote its synthesis and decomposition. To bypass some of the issues with resistance heating commonly used to support the endothermal reactions, contact-free heating in an alternating magnetic field is utilized. In addition to rapidly achieving the desired temperature, the decomposition reaction can be halted in seconds, which renders magnetic heating suitable for use with sources of renewable electrical power such as solar panels or wind turbines. Here, the supply of electricity may be unexpectedly interrupted and no storage solutions are required due to the responsiveness of magnetic heating.

[0014] To further alleviate issues with temperature control of exothermic reactions the adjustment of Curie temperature achieved by adjusting the composition of the magnetic catalyst limits the upper temperature of the catalyst. Furthermore, by layering the catalyst, where each layer has a unique magnetic composition, a favourable temperature profile to maximise yield and safety can be easily achieved without the need for multiple heaters and controllers.

[0015] Precise and rapid temperature control has the additional advantage that the conversion can be strictly controlled. Thus, the decomposition of ammonia can be controlled if the goal is to bum ammonia (e.g. in an internal combustion engine).

[0016] DESCRIPTION OF THE INVENTION

[0017] The present invention provides a modular process for hydrogen production and storage by catalytic decomposition and synthesis of NH3 in the presence of a catalyst material that can be heated by induction of a magnetic flux.

[0018] Accordingly, the invention relates to the use of a catalyst material comprising a ferromagnetic material, a support material, and catalytically active particles, in the synthesis or decomposition or NH3, wherein the catalyst material and reactants in contact with the catalyst material are heated by inducing magnetic flux in the catalyst material.

[0019] A particular embodiment of the invention relates to a method for synthesizing NH3, comprising: bringing reactants comprising N2 and H2 into contact with a catalyst material in a reactor, said catalyst material comprising a ferromagnetic material, a support material, and catalytically active particles, applying a magnetic field to the reactor, to induce magnetic flux in the catalyst material, thereby heating the catalyst material and reactants in contact with the catalyst material to a predetermined temperature, and reacting N2 and H2 to yield NH3.

[0020] Another embodiment of the invention relates to a method for preparing hydrogen from NH3 by catalytic decomposition, comprising: bringing NH3 into contact with a catalyst material in a reactor, said catalyst material comprising a ferromagnetic material, a support material, and catalytically active particles, applying a magnetic field to the reactor, to induce magnetic flux in the catalyst material, thereby heating the catalyst material and NH3 in contact with the catalyst material to a predetermined temperature, and inducing catalytic decomposition of NH3 to yield H2.

[0021] The predetermined temperature may vary depending on the Curie temperature of the catalyst material, and / or the amount of ferromagnetic material comprised in the catalyst material. In preferred embodiments, the predetermined temperature is in a range of 200-600°C, preferably about 300-400°C, more preferably about 320-360°C.

[0022] The rapid heating and cooling by magnetic heating according to the invention allows NH3 and H2 production on demand, which is well compatible with the transient nature of renewable resources. Electrification of ammonia synthesis / decomposition allows easy coupling with electrolyzer technologies to enhance the use of renewable resources.

[0023] Furthermore, electrified ammonia decomposition enables fast tuning of the output gas composition and opens way for an on-demand and tunable H2-NH3 ratio ranging from 0-100 % hydrogen between approximately 200°C and 400°C, in particular between 280°C and 380°C when a nanocomposite Ru-based magnetic catalyst is applied. Ru is used because of high activity for ammonia cracking as well as synthesis, as previously predicted by theoretical approaches and depicted using the volcano plot (Jacobsen et al., “Catalyst design by interpolation in the periodic table: bimetallic ammonia synthesis catalysts”, J. Am. Chem. Soc., 2001 , 123 (34), 8404-8405, DOI 10.1021 / jaO10963d). However, other materials known to catalyze decomposition of ammonia can be used as well. Further examples are Fe, Co, Ni, Au, Ag, Ir, Pd, Pt, bimetallic and trimetallic alloys of thereof (Wu et al, “Computational Screening of Bimetallic Catalysts: Application to Ammonia Decomposition”, J. Phys. Chem. C, 2022, 126, 192-202, DOI 10.1021 Zacs.jpcc.1 c08091 ). The importance of on-demand ammonia cracking is evident with spark ignition (SI) engines, which can be modified to run on ammonia, which is a promising carbon-free alternative to the existing fuels. Reportedly, performance is peak when the engine feed mixture contains 10 vol.% hydrogen (Morch et al., “Ammonia / hydrogen mixtures in an Sl-engine: Engine performance and analysis of a proposed fuel system”, Fuel, 2011 , 90, 854-864, DOI 10.1016 / j. fuel.2010.09.042). Normally, exhaust gases are routed to provide heat for the decomposition reaction to proceed, however, magnetic heating could be applied to closely vary and provide the exact amount of hydrogen required which is already feasible with temperatures approximately as low as 300 °C.

[0024] In practice, a composite material is used that allows magnetic heating, and also catalyzes the reaction. For this purpose, the catalyst material may comprise the ferromagnetic material embedded in the support material coated with the catalytically active particles. Magnetic heating is possible due to an inclusion of magnetic susceptor cores embedded within a high-surface matrix, which serves as a support for any kind of metallic nanoparticles where the decomposition reaction takes place. Heat is transferred from magnetic particles to the surrounding support and finally, catalytic nanoparticles. In preferred embodiments, the catalyst material comprises the ferromagnetic material in an amount of 5-90 wt.%, preferably 30-60 wt.-% based on the total weight of the catalyst material.

[0025] Alternatively, dual-purpose particles capable of both magnetic heating and catalysis can be deposited on a support, which simplifies the preparation procedure. In this embodiment, the catalytically active particles are composite particles comprising at least one catalytically active material and the ferromagnetic material. Preferably, the composite particles comprise a bimetallic alloy of e.g. Ru and Co or a trimetallic alloy of e.g. Ru, Co and Ni. The composite particles may comprise the catalytically active material in an amount of 5-20 wt. %, preferably 10-15 wt. %, based on the total weight of the composite particles.

[0026] The catalyst material may include composite particles in an amount of 10-90 wt. %, preferably 20-50 wt.%, more preferably about 30-45 wt. %.

[0027] Since the atmosphere within the reactor is strongly reductive, metal particles retain their magnetic properties even over prolonged reaction times. For the purpose of this invention, an alloy of Co and Ni is preferably used. Co features a hard-ferromagnetic behavior that is softened when alloyed with Ni. By tuning their ratios, the material's magnetic properties such as Curie temperature, saturation magnetization and monocrystalline anisotropy can be tweaked to provide improved heating capabilities. Furthermore, pure Co readily oxidizes when exposed to air, which is remedied by an inclusion of Ni. Optimally, a 50 / 50 wt.% to 80 / 20 wt.% CoNi ratio is used and the alloy features a Curie temperature above 1000 °C meaning such temperatures are achievable before a loss of magnetic properties ensues.

[0028] Catalytically active particles and ferromagnetic material are associated with a support material. The support material preferably has a porosity in a range of 10-50%, preferably at least 20%. Porosity can be determined by electron microscopy and X ray or neutron scattering. The surface area of the support material is preferably in a range of about 5m2 / g to about 300 m2 / g, preferably at least 20 m2 / g or at least 50 m2 / g. Surface area can be determined, for example, by BET technique.

[0029] The support material may comprise at least one transition metal oxide, such as titanium oxide and zirconium oxide, rare earth oxide, such as cerium oxide, aluminum oxide, preferably y-alumina, magnesium oxide, mixed oxide, silicon oxide, carbon, N-doped carbon, graphitic carbon nitride, polymeric carbon nitride or combinations thereof.

[0030] In preferred embodiments, alloyed particles are encapsulated in a y-alumina matrix. The amount of magnetic material is varied between 10-80 wt.%, in particular 30-60 wt.%, depending whether improved heating capabilities or a large surface area are prioritized. The alumina matrix immobilizes magnetic nanoparticles while providing ample surface area to accommodate the required catalytic metal nanoparticles. A 1-4 wt.% loading is achieved using precipitation in solution. Upon the addition of a base, the precipitate is washed, dried and reduced resulting in an active catalyst.

[0031] In the case of supported dual-purpose particles, a bimetallic alloy of Ru and Co is capable of magnetic heating and ammonia decomposition. To enable sufficient heating, a 20-50 wt.% RuCo loading is used. The metallic particles contain 5-20 wt.% Ru. If an even softer-ferromagnetic behavior is required, a three-component alloy with Ni is prepared.

[0032] To supply an alternating magnetic field required for energy transfer and consequent heating of the catalyst, an induction heater is required. A quartz reactor tube loaded with the composite material is placed within the coil and the induction heater’s power level is adjusted to achieve the necessary magnetic field amplitude. In this manner, the catalyst layer temperature and thus ammonia conversion rates are regulated. Because heat is generated inside the reactor exactly where required, its transfer distance to catalytic nanoparticles is significantly reduced and temperature gradients across the vessel’s walls are of little concern. To help retain the heat, a layer of insulation is wrapped around the reactor tube. Within the catalyst layer, uniform heating is preferred and attainable when magnetic susceptor particles are homogenously distributed throughout the support.

[0033] The described setup provides an infinitely adjustable ammonia cracking capability ranging from 0-100 % hydrogen output, which is carried out in a sub-300 °C to 400 °C temperature range.

[0034] Another aspect of the invention is a reactor system comprising: a reactor unit comprising a reactor containing a catalyst material as defined above, an inlet for introducing reactants, in particular NH3 or N2 and H2, into the reactor, and an outlet for discharging reaction products, in particular hydrogen or NH3, from the reactor, and an induction coil connected to a power source supplying alternating current, configured to apply a magnetic field to the reactor unit.

[0035] Further, the invention provides a catalyst material for catalyzing decomposition of NH3 to yield hydrogen or synthesis of NH3 from N2 and H2, comprising: a porous support material having a surface area of about 5m2 / g to about 300 m2 / g, catalytically active particles coated on the support material, in particular wherein the catalytically active particles are nanoparticles, comprising a catalytically active material, and a ferromagnetic material, preferably comprising Co, Ni, Fe, or combinations thereof, wherein the ferromagnetic material is embedded in or associated with the support material or included in the catalytically active particles. All aspects described above for the method and use of the invention similarly apply to the reactor system and the catalyst material of the invention. The catalytically active material preferably comprises or consists of Ru.

[0036] In a particularly preferred embodiment, the support material comprises y-alumina, the catalytically active material comprises Ru, and / or the ferromagnetic material comprises Co and Ni in a ratio of 20 / 80 wt.% to 80 / 20 wt.%, preferably 50 / 50 wt.% to 80 / 20 wt.%.

[0037] The invention is further illustrated by the following Figures and Examples.

[0038] FIGURES

[0039] Figure 1 a and b Low magnification TEM images of the three-part composite Ru catalyst. In a), several globular CoNi particles are marked with arrows. The surrounding matrix is a high-surface y-alumina support in the form of nanosheets. c and d Under high magnification, Ru nanoparticles can be observed. In d), several are marked with arrows and measure approximately 1.3 nm in diameter.

[0040] Figure 2 A three-part composite Ru catalyst magnetic hysteresis curve measured using a VSM. The magnetization profile is measured between -10 kOe and +10 kOe.

[0041] Figure 3 A long-term ammonia decomposition stability test to determine the composite Ru-based catalyst deactivation, input gas flow rate is 30 mL / min 10 % ammonia. The conversion rate drops from 42.2 % to 36.0 % in approximately two days.

[0042] Figure 4 Calculated ammonia conversion rates determined from micro GC measurements plotted against the corresponding temperature readings. The input gas flow (30 mL / min) contains 10 % ammonia. Figure 5 a. Real-time on / off pulse testing at Bmax = 35.4 mT. At 300 °C, the conversion (30 mL / min, 10 % ammonia) is not yet complete. Desorption peaks of ammonia and hydrogen can be clearly seen extending above the baseline. As soon as heating is turned on, the temperature ramp-up is evident. b. Real time on / off pulse testing at Bmax = 38.0 mT. Desorption peaks of ammonia and hydrogen can still be observed. c. Real time on / off pulse testing at Bmax = 48.0 mT. Due to a steep temperature ramp, desorption peaks are no longer present.

[0043] Figure 6 shows a reactor system embodiment to carry out the synthesis or decomposition of ammonia using magnetic heating of catalyst.

[0044] The reactor system comprises of a reactor tube 2 fixed in a housing 1 and arranged to accommodate a catalyst 6 susceptible for magnetic heating. Reactants are introduced into the reactor tube 2 via an inlet 4, and reaction products formed on the surface of the catalyst 6 are outlet via an outlet 5. The inlet and outlet 4 a 5 as well as the housing 1 have appropriate gaskets, seals 3 or the like (not shown in figure 6). The reactor system comprises further of induction coil 7, positioned so as to generate alternating magnetic field within the reactor tube and to be powered by power source suppling an alternating electric current (not shown in Figure 6). The catalyst material 6 is heated to a temperature within a given temperature range T relevant for carrying out the ammonia synthesis or decomposition, by means of the alternating magnetic field. The temperature T is measured by a thermocouple 8.

[0045] EXAMPLES

[0046] Example 1 : Preparation procedure of Ru-based magnetic catalyst containing CoNi susceptor cores. CoNi magnetic nanoparticle precursors were prepared by co-precipitation of cobalt (II) and nickel (II) from aqueous solution. During vigorous stirring, a 1 :2 mixture of NaCIO (< 60 g of active chlorine per L, TKI Hrastnik) and NaOH (sodium hydroxide pellets, 98.96 %, Fisher Chemical) was added dropwise to achieve a pH level of 9. The black precipitate was washed and centrifuged.

[0047] The synthesized magnetic precursor nanoparticles were embedded within an alumina matrix by hydrolysis of AIN powder (grade C, H. C. Starck) in aqueous suspension during vigorous stirring and heating under reflux (3 h). The decomposition of AIN saturates the suspension with ammonium and aluminum species. The latter rapidly condense and form nuclei which leads to a growth of microporous, lamellar or nanosheet-like aggregates of boehmite (y-AIOOH) encapsulating the CoNi precursor particles:

[0048] AIN + 2H2O - A100H + NH3

[0049] In the second step, the composite support precursor was reduced in a flow of hydrogen for 1 h at 850 °C (upright tubular furnace). In addition to reducing the alloyed particles, boehmite is transformed to y-alumina:

[0050] 4A100H - 2A12O3+ 2H2O

[0051] The composite support contained 50 wt.% particles and 50 wt.% alumina. The embedded magnetic particles contained 67 wt.% Co and 33 wt.% Ni.

[0052] To deposit Ru nanoparticles, three grams of support were vigorously dispersed in 300 mL of water using an overhead stirrer and an ultrasound bath. The pH level was lowered to 6.5 using diluted nitric acid and afterwards, the appropriate amount of Ru stock solution (ruthenium (III) chloride hydrate, for analysis, EMSURE) was pipetted into the mixture. Using a 1 M sodium hydroxide solution, pH was raised to 10 and the mixture was centrifuged to isolate the catalyst. After washing and freeze-drying, a prereduction step was carried out in an upright tubular furnace at 500 °C for 2 h in a flow of pure hydrogen (50 mL / min) which resulted in a 2 wt.% Ru loading.

[0053] Example 2: Testing procedure for the ammonia decomposition reaction An induction heater’s coil (235 kHz resonant frequency) was positioned around a quartz reactor tube and a recirculating water cooler was used to circulate chilled water through the heater and the copper coil. A layer of glass-fiber insulation was placed between the induction coil and the reactor tube to minimize heat losses. The 2 % Ru- based catalyst (51 mg) was mixed with bare support containing no Ru (104 mg) to further lower the overall Ru loading and achieve catalyst operation within the kinetic regime. The diluted catalyst layer was held in position using quartz wool under and above the packing layer (155 mg in total, 14 mm layer height).

[0054] For safety reasons, the tube resides in a surrounding stainless-steel chamber with front and back sliding doors for easy access. The back doors feature an opening for the induction coil while the rest of the heating unit is placed on a laboratory jack just outside the protective chamber. In this manner, the coil’s height can be precisely adjusted. For optimum heating and repeatability, the catalyst layer is placed in the exact center of the coil where the magnetic field strength is homogenous and strongest.

[0055] A system comprised of stainless-steel lathe-turned parts fitted with the corresponding O-rings allows for test tube changes while preventing gas leaks when the system is pressurized.

[0056] Prior to testing, the catalyst was purged with nitrogen (10 mL / min) for 30 min to remove moisture. The final reduction took place in a 30 % hydrogen in nitrogen mix (total flow 20 mL / min, 20 min) at 350 °C (magnetic field amplitude Bmax = 35.9 mT) using the same setup. The magnetic field was then turned off and the catalyst was left to cool. For decomposition testing, the gas mixture was changed to 10 % ammonia in nitrogen (30 mL / min total flow rate) and remained the same throughout the entire testing procedure. On-line gas chromatography was used to monitor outlet gas composition.

[0057] Example 3: Determining ammonia conversion rates in relation to catalyst layer temperature.

[0058] Before catalytic testing, conversion rates using Ru-free support were determined in relation to layer temperature. Then, the catalyst was loaded and testing could proceed. To confirm operation within the kinetic regime, the heater was turned up until a roughly 40 % conversion was achieved. After relatively stable operation was achieved the flow rate of 10 % NH3 in He was doubled. The conversion rate lowered to approximately 20 %. With this, we assumed operation within the kinetic regime, where mass transfer limitations were minimal. To determine catalyst deactivation over an extended period of time, a stability test was conducted at 320 °C. The test was left to run for approximately two days until the conversion rate stabilized (Figure 3).

[0059] To determine conversion rates in relation to catalyst temperature, the heater’s power output was changed to achieve various rates while taking note of the corresponding temperatures. Based on on-line gas chromatography measurements (mol% of ammonia remaining in the reactor output flow), the conversion rates were calculated (Figure 2)

[0060] Example 4: Real-time on / off ammonia decomposition testing

[0061] Three sets of real-time on / off ammonia decomposition tests (30 mL / min) were performed to determine the output gas compositions in relation to different temperature ramp profiles. A mass spectrometer was used for quick scans of several predetermined mass fragments: H2(2), NH3(16), NH3(17), H2O (18), N2(28) and O2(32). The heater’s power output was varied to achieve different magnetic field amplitudes which remained constant during the course of an individual experiment: 35.4 mT, 38.0 mT and 48.0 mT. After the temperature stabilized, heating was switched off until the catalyst cooled down to room temperature. For each power level, three such pulses were recorded (Figure 3).

[0062] At 35.4 mT and 38.0 mT, the temperature ramp-up is mild and because of rapid fragment detection small amounts of ammonia and hydrogen can be observed at approximately 160-200 °C which would not be feasible with gas chromatography. Since ammonia decomposition ensues at nearly 300 °C, both peaks can be explained with desorption from the catalyst surface which got saturated while cooling down. At 48.0 mT, the temperature increase is substantially faster and the previous desorption peaks are no longer present. Complete conversion, however, is reached within approximately 7 minutes.

Claims

CLAIMS1 . Use of a catalyst material comprising a ferromagnetic material, a support material, and catalytically active particles, in the synthesis or decomposition of NH3, wherein the catalyst material and reactants in contact with the catalyst material are heated by inducing magnetic flux in the catalyst material.

2. A method for synthesizing NH3, comprising: bringing reactants comprising N2 and H2 into contact with a catalyst material in a reactor, said catalyst material comprising a ferromagnetic material, a support material, and catalytically active particles, applying a magnetic field to the reactor, to induce magnetic flux in the catalyst material, thereby heating the catalyst material and reactants in contact with the catalyst material to a predetermined temperature, and reacting N2 and H2 to yield NH3.

3. A method for preparing hydrogen from NH3 by catalytic decomposition, comprising: bringing NH3 into contact with a catalyst material in a reactor, said catalyst material comprising a ferromagnetic material, a support material, and catalytically active particles, applying a magnetic field to the reactor, to induce magnetic flux in the catalyst material, thereby heating the catalyst material and NH3 in contact with the catalyst material to a predetermined temperature, and inducing catalytic decomposition of NH3 to yield H2.

4. The method of claim 2 or 3, wherein the temperature is in a range of 200- 600°C, preferably about 300-400°C, more preferably about 320-360°C.

5. The use of claim 1 or the method of any one of claims 2-4, wherein the catalyst material comprises the ferromagnetic material embedded in the support material coated with the catalytically active particles.

6. The use of claim 1 or the method of any one of claims 2-5, wherein the catalyst material comprises the ferromagnetic material in an amount of 5-90 wt.%, preferably 30-60 wt.-% based on the total weight of the catalyst material.

7. The use of claim 1 or the method of any one of claims 2-6, wherein the ferromagnetic material comprises Co, Ni, Fe, or combinations thereof, in particular a combination of Co and Ni in a ratio of 10 / 90 wt.% to 90 / 10 wt.%, preferably 50 / 50 wt.% to 80 / 20 wt.%.

8. The use of claim 1 or the method of any one of claims 2-7, wherein the catalyst material comprises a catalytically active material in an amount of 0.2- 20 wt.%, preferably 1-4 wt.% based on the total weight of the catalyst material, wherein the catalytically active material preferably comprises or consists of Ru.

9. The use of claim 1 or the method of any one of claims 2-8, wherein the catalytically active particles are composite particles comprising at least one catalytically active material and the ferromagnetic material, preferably wherein the composite particles comprise a bimetallic alloy of e.g. Ru and Co or a trimetallic alloy of e.g. Ru, Co and Ni.

10. The use of claim 1 or the method of claim 9, wherein the composite particles comprise the catalytically active material in an amount of 5-20 wt. %, preferably 10-15 wt. %, based on the total weight of the composite particles, and / or wherein the catalyst material comprises the composite particles in an amount of 10-90 wt. %, preferably 20-50 wt.%, more preferably about 30-45 wt. %.11 . The use of claim 1 or the method of any one of claims 2-10, wherein the support material has a porosity in a range of 10-50%, preferably at least 20%, and / or a surface area of about 5m2 / g to about 300 m2 / g, preferably at least 20 m2 / g or at least 50 m2 / g.

12. The use of claim 1 or the method of any one of claims 2-11 , wherein the support material comprises at least one transition metal oxide, such as titanium oxide and zirconium oxide, rare earth oxide, such as cerium oxide, aluminum oxide, preferably y-alumina, magnesium oxide, mixed oxide, silicon oxide, carbon, N-doped carbon, graphitic carbon nitride, polymeric carbon nitride or combinations thereof.

13. The method of any one of claims 2-12, wherein the magnetic field is generated by supplying an alternating current to the reactor, in particular to a heat station or induction heating power supply associated with the reactor.

14. A reactor system, comprising a reactor unit comprising a reactor containing a catalyst material as defined in any one of claims 2-13, an inlet for introducing reactants, in particular NH3 or N2 and H2, into the reactor, and an outlet for discharging reaction products, in particular hydrogen or NH3, from the reactor, and an induction coil connected to a power source supplying alternating current, configured to apply a magnetic field to the reactor unit.

15. A catalyst material for catalyzing decomposition of NH3 to yield hydrogen or synthesis of NH3 from N2 and H2, comprising: a porous support material having a surface area of about 5m2 / g to about 300 m2 / g, catalytically active particles coated on the support material, in particular wherein the catalytically active particles are nanoparticles, comprising a catalytically active material, and16a ferromagnetic material, preferably comprising Co, Ni, Fe, or combinations thereof, wherein the ferromagnetic material is embedded in or associated with the support material or included in the catalytically active particles, preferably wherein the support material comprises y-alumina, the catalytically active material comprises Ru, and / or the ferromagnetic material comprises Co and Ni in a ratio of 20 / 80 wt.% to 80 / 20 wt.%, preferably 50 / 50 wt.% to 80 / 20 wt.%.

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