Decomposition of ammonia on nickel-based catalysts

Abstract

The invention relates to a method for producing H2 from NH3. This includes introducing NH3 into a fixed bed reactor at a gas temperature in the range of 550-850 DEG C in which NH3 is partially decomposed into H2 and N2 over an NH3 decomposition catalyst. The gas mixture thus obtained is discharged from the fixed bed reactor at a gas temperature in the range of 300-700 DEG C, heated to a temperature in the range of 550-700 DEG C and then introduced into a tubular reactor in which NH3 is further decomposed into H2 and N2 on a nickel-based NH3 decomposition catalyst. The gas mixture obtained in this way is discharged from the tubular reactor at a gas temperature in the range of 550-750 DEG C.

Description

[0001] Priority is claimed to Luxembourg patent application No. LU 103169, filed July 13, 2023. TECHNICAL FIELD

[0002] The present invention relates to a process for the production of H2 from NH3. This comprises introducing NH3 into a fixed bed reactor at a gas temperature in the range of 550 to 850 °C, in which the NH3 is partially decomposed to H2 and N2 over a NH3 decomposition catalyst. The gas mixture thus obtained is discharged from the fixed bed reactor at a gas temperature in the range of 300 to 700 °C, is heated to a temperature in the range of 550 to 700 °C and is then introduced into a tubular reactor, in which the NH3 is further decomposed to H2 and N2 over a nickel-based NH3 decomposition catalyst. The gas mixture thus obtained is discharged from the tubular reactor at a gas temperature in the range of 550 to 750 °C. BACKGROUND

[0003] H2 can be obtained from H2O by renewable energy, which is then converted to NH3 with N2. NH3 can be stored and transported more safely than H2. NH3 can then be decomposed again to H2 and N2. After separation of H2 from N2, H2 finds a wide range of industrial applications.

[0004] The decomposition of NH3 to N2 and H2 is an endothermic reaction (AH°= 45.9 kJ mol -1 ), in which the molar mass is doubled (2 NH3 -> N2 + 3 H2), so that the reaction is fundamentally promoted by high temperatures and low pressures. A variety of materials have been proposed as catalysts for the decomposition, which are active at different temperatures (see, for example, the review by Il. Lucentini et al., Ammonia Decomposition to Generate Hydrogen, Ind. Eng. Chem. Res. 2021, 60, 18560-18611).

[0005] The catalytic decomposition of NH3 produces a product gas containing H2, which is mixed with N2 and other possible gaseous components, such as unconverted NH3. However, many industrial applications require H2 of high purity, so that the product gas needs to be purified before the H2 is delivered to the industrial application. While in principle H2 can be cleaned by various methods, such as cryogenic or membrane processes, cleaning by pressure swing adsorption is particularly economically viable on an industrial scale.

[0006] US 4 704 267 A relates to the production of high purity hydrogen from liquid anhydrous ammonia. The ammonia is evaporated and then decomposed into its constituent elements. The resulting dissociated gas stream is fed to an adiabatic metal hydride cleaning unit to absorb the hydrogen present in the stream. The adsorbed hydrogen is then recovered as a high purity product.

[0007] US 2020 / 0123006 A1 relates to a process for the production of a nitrogen and hydrogen containing product gas from ammonia comprising the steps of non-catalytic partial oxidation of ammonia with an oxygen containing gas to obtain a process gas containing nitrogen, water, an amount of nitrogen oxides and a residual amount of ammonia; cleaving at least a part of the residual amount of ammonia in the process gas to hydrogen and nitrogen by contact with a nickel containing catalyst and simultaneously reducing the amount of nitrogen oxides to nitrogen and water by reaction with a part of the hydrogen formed during cleaving of the process gas by contact of the process gas with the nickel containing catalyst; and withdrawing a hydrogen and nitrogen containing product gas.

[0008] FR 1 469 045 A relates to a device consisting of a preheater fed with ammonia, a bundle of tubes surrounding a catalyst for the cleavage of ammonia and optionally a cell for the cleaning of hydrogen by diffusion, which are connected to each other and which are present in a single housing containing heating means.

[0009] CN 111 957 270 A relates to an ammonia decomposition device, which comprises an ammonia decomposition unit and a combustion unit acting on the ammonia decomposition unit. Ammonia enters the ammonia decomposition unit via a first inlet for purifying gas to carry out an ammonia decomposition reaction. The generated mixed gas is discharged via a second outlet for purifying gas, and then enters the combustion unit via a second inlet for purifying gas. The mixed gas contains nitrogen, hydrogen and undecomposed ammonia. The mixed gas enters the combustion unit to provide heat for the ammonia decomposition reaction in the ammonia decomposition unit, so as to achieve self-sufficiency in the hydrogen production system by ammonia decomposition. No additional fuel is needed to supply energy, and the cost of the hydrogen production system by ammonia decomposition is reduced.

[0010] CN 112 742 310 A relates to an ammonia decomposition reaction device and an ammonia decomposition method. The device comprises a heater or a preliminary reactor and a reactor, and the reactor is a chamber and contains an arrangement of a first separation plate, a plurality of pipes, a gas distributor and a second separation plate. The arrangement of the preliminary reactor allows the catalytic combustion reaction to start at room temperature, the temperature of the reactor is raised to 350-600°C and the ammonia decomposition reaction is carried out; or the reactor is heated by using the heater, the catalytic combustion reaction starts after the temperature of the reactor reaches 200-350°C, the heater is turned off, and the temperature of the reactor is further raised to 350-600°C by using the heater. The catalytic combustion reaction releases heat, and the ammonia decomposition reaction is carried out.

[0011] CN 113 896 168 A relates to a method for preparing hydrogen or reducing gas by cracking ammonia through a two-stage process, comprising the following steps: the liquid ammonia of raw material is completely gasified and heated by a heat exchange gasification system, then enters a first-stage heat exchange ammonia cracking reaction system to produce a partial ammonia cracking reaction, and the reaction gas from the first-stage heat exchange ammonia cracking reaction system enters a second-stage high-temperature ammonia cracking reaction system to carry out a residual ammonia cracking reaction. The high-temperature ammonia cracking reaction gas from the second stage enters the heat exchange ammonia cracking reaction system from the first stage and the heat exchange gasification system in turn, so as to gradually recover heat, thereby obtaining the reducing gas.

[0012] JP 2023 073692 A relates to a method for obtaining hydrogen by ammonia decomposition. In an ammonia decomposition step by combustion gas, heating is performed, including a step of contacting a catalyst containing Ru with ammonia at a temperature of 400°C and above and 550°C and below while heating to decompose ammonia into nitrogen and hydrogen, wherein ammonia is connected to a heat exchanger reactor 3 at a pressure of 1.5 MPa and above and 7 MPa and below; a step of separating hydrogen by contacting a gas obtained in the previous step with a hydrogen-permeable membrane at a temperature of 300°C and above and 550°C and below; a step of reducing the gas containing unconverted ammonia to 0.3 MPa and below after removing hydrogen; a step of performing ammonia decomposition by adding an oxygen-containing gas to the decomposed gas to contact it with a catalyst containing at least one metal selected from the group consisting of Ru, Rh, and Pd; and a combustion step by adding an oxygen-containing gas to the gas obtained in the previous step.

[0013] WO 2011 / 107279 A1 relates to an ammonia-based hydrogen production reactor comprising an ammonia cracking chamber with an ammonia cracking catalyst, an internal combustion chamber with a combustion or oxidation catalyst in thermal contact with the ammonia cracking chamber, an ammonia gas preheating chamber, and a shell ring for recovering heat from combustion products leaving the combustion chamber, wherein the cracking chamber, the internal combustion chamber, the preheating chamber, and the heat recovery shell ring are in a concentric arrangement.

[0014] WO 2012 / 090739 A1 relates to a hydrogen generator comprising a decomposition device that decomposes a compound containing hydrogen atoms and nitrogen atoms and generates hydrogen; a compound supply device that supplies the compound to the decomposition device; and an oxygen supply device that supplies oxygen to the decomposition device.

[0015] WO 2020 / 095467 A relates to an apparatus for producing hydrogen, comprising: an evaporator which heats liquid ammonia to produce ammonia gas; a pyrolysis main apparatus which causes combustion of a fuel gas, whereby the ammonia gas produced by the evaporator is heated and decomposed into nitrogen and hydrogen; a cooler which cools a gas produced from a decomposed product, the decomposed product containing nitrogen and hydrogen produced by the main apparatus for thermal decomposition; and a separator (8) which separates hydrogen from the cooled gas produced by the decomposition.

[0016] WO 2021 / 257944 A1 relates to the recovery of hydrogen from an ammonia cracking process, wherein the cracked gas is cleaned in a PSA apparatus. The use of a membrane separator to separate the PSA tail gas improves the recovery rate.

[0017] WO 2022 / 096529 A1 relates to a cracking method of ammonia, a production method of hydrogen, and a generation method of electric current, which includes electrolyzing water in supplied ammonia, evaporating, preheating, and cracking the ammonia at a low temperature using an ammonia synthesis catalyst.

[0018] WO 2022 / 189560 A1 relates to a process and system for producing a hydrogen product from ammonia, comprising: optionally at least one preliminary cracking reactor, such as an adiabatic preliminary cracking reactor, arranged to receive an ammonia feed stream and produce therefrom a partially converted ammonia feed stream ammonia, hydrogen, and nitrogen; and an ammonia cracking reactor, such as an electrically heated reactor. The reactor is arranged to receive the partially converted ammonia feed stream or the ammonia feed stream to produce a tail gas stream comprising hydrogen and nitrogen and optionally unconverted ammonia; and a hydrogen recovery unit arranged to receive the tail gas stream to produce the hydrogen product and a tail gas stream comprising hydrogen, nitrogen, and optionally unconverted ammonia.

[0019] WO 2022 / 243410 A1 relates to a method for synthesizing hydrogen by catalytic cracking of ammonia; wherein an ammonia-containing stream is subjected to a catalytic cracking step in the presence of heat to obtain a combustion gas and a hot cracked stream containing nitrogen, hydrogen and possibly residual ammonia, with or without water; wherein the hot cracked stream is subjected to a hydrogen recovery step to obtain a high-purity hydrogen stream.

[0020] WO 2022 / 265647 A1 relates to the recovery of a renewable hydrogen product from an ammonia cracking process, wherein the cracked gas is cleaned in a first PSA apparatus and at least a portion of the first PSA tail gas is recycled for use as a fuel in order to reduce the carbon intensity of the renewable hydrogen product.

[0021] WO 2022 / 265648 A1 relates to the removal of NOx impurities from flue gas produced in an ammonia cracking process using selective catalytic reduction (SCR), the ammonia cracking process using a hydrated ammonia solution produced by cooling compressed tail gas from a hydrogen PSA apparatus used to clean the cracked gas.

[0022] WO 2022 / 265649 A1 relates to reducing the water content of ammonia used in an ammonia cracking process, which enables the use of cracking catalysts that are not compatible with water. The water removal process can also be used to recover and recycle ammonia from the cracked gas.

[0023] WO 2022 / 265650 A1 relates to an ammonia cracking process in which the cracked gas is purified in a PSA system. Residual ammonia in the first cracked gas is converted into more hydrogen and nitrogen by supplying the PSA tail gas or a gas derived therefrom to a secondary cracking reactor and further processing the second cracked gas.

[0024] WO 2022 / 265651 A1 relates to a process in which residual ammonia in a hydrogen PSA system is removed from the ammonia cracked gas using a non-zeolitic adsorbent such as activated carbon, activated alumina or silica gel.

[0025] The methods known from the prior art for obtaining H2 from NH3 are unsatisfactory in all respects and there is a need for improved methods that can be implemented economically on an industrial scale. There is a need to develop suitable reactor concepts suitable for producing H2 from NH3. An ignited tubular reactor similar to a steam reformer is one option that is in principle suitable for endothermic or quasi-isothermal high-temperature reactions. However, there are various obstacles to applying the steam reforming industry to the catalytic decomposition of NH3. SUMMARY

[0026] It is an object of the present invention to provide an improved method for producing H2 from NH3. The method should be economically viable in terms of energy balance and yield and should be implementable on an industrial scale. It should be possible to use a NH3 decomposition catalyst with a sufficient service life at given reaction conditions and at an acceptable cost.

[0027] This object is achieved by the subject matter of the claims.

[0028] It has been found that cleaning the product gas by pressure swing adsorption requires a pressure of the product gas of at least 10 bara, preferably at least 20 bar a, in order to work economically. However, such a pressure is itself disadvantageous for the catalytic decomposition of NH3. It would be uneconomical to carry out the catalytic decomposition at a lower pressure and to compress the product gas before the pressure swing adsorption.

[0029] It has now surprisingly been found that there is a possible reaction mechanism that first achieves a good yield of the decomposition reaction, but secondly also proceeds at a sufficiently high pressure, so that subsequently cleaning can be carried out in an economically viable manner and without prior compression of the product gas by pressure swing adsorption.

[0030] It has been found that the reaction mechanism in the two reactors connected in series is advantageous, in particular when the first reactor is a fixed bed reactor operated substantially adiabatically without external heat supply and the second reactor is designed as a fired tube reactor similar to a primary reformer (steam reformer). Thus, the size of the fired tube reactor can be reduced. As a result, the amount of heat present in the combustion air, i.e. the heat present in the tail gas of the combustion system for the tube reactor, can then also be limited and must be returned to the process for an economically viable process mechanism in order not to be released unused into the environment.

[0031] It has been found here that the temperature at the inlet (T1) and the temperature at the outlet (T2) of the first reactor, the temperature at the inlet (T3) and the temperature at the outlet (T4) of the second reactor, the degree of partial conversion in the first reactor and the configuration of the second reactor interact with one another and can influence in such a way that the economic viability of the process can be optimized.

[0032] For the upstream fixed bed reactor, the inlet temperature (T1) and the outlet temperature (T2) are limited in the upward direction by the permissible preheating and in the downward direction by the activity of the catalyst. Depending on the catalyst or the type of catalyst, the operating window is preferably between about 650°C and about 350°C.

[0033] For the downstream fired tube reactor, the parabolic profile of the energy supply through the tube wall preferably results in significantly less catalyst requirement compared to a linear profile of the energy supply. It has been found that roof combustion with a relatively short flame is the best solution for the energy supply. Preferably, the downstream fired tube reactor is designed for an inlet temperature in the range of about 550°C to 700°C. At higher temperatures, the reaction consumes more energy than can be supplemented by the tube wall through combustion. In addition, special materials with a shortened service life would be required for the equipment, and the volume of catalyst would only be reduced slightly. Preferably, the downstream fired tube reactor is designed such that its outlet temperature is higher than its inlet temperature. In this way, an approach to equilibrium conversion can be achieved. A lower outlet temperature would result in a lower conversion rate, resulting in a higher gas load and an increased reactor volume required.

[0034] In particular, it has been found that the reaction conditions under which a conversion of 98% or more of H2can be achieved, as a result of which the residual amount of unconverted NH3in the product gas is sufficiently low that H2can be separated by pressure swing adsorption without further measures.

[0035] The first aspect of the present invention relates to a process for the preparation of H2from NH3, comprising the following steps: (a) providing a reactant gas comprising or consisting essentially of NH3; (b) heating the reactant gas to a gas temperature T1 in the range of 550-850 °C at a pressure pi of at least 10 bar a; (c) introducing the heated reactant gas at the gas temperature T1 and the pressure pi into at least one fixed bed reactor containing at least one catalyst bed comprising or essentially consisting of an NH3 decomposition catalyst; (d) partially decomposing the NH3 on the at least one catalyst bed in the at least one fixed bed reactor to obtain an intermediate product gas comprising or essentially consisting of H2, N2 and undecomposed NH3; and (e) withdrawing the intermediate product gas from the at least one fixed bed reactor at a gas temperature T2 in the range of 300-700 °C and a pressure p2 of at least 10 bar a; (f) heating the intermediate product gas to a gas temperature T3 in the range of 550-700 °C at a pressure p3 of at least 10 bar a; (g) introducing the heated intermediate product gas at the gas temperature T3 and the pressure p3 into at least one tubular reactor comprising a plurality of parallel tubes, each tube containing at least one catalyst bed, the catalyst bed being heated by combustion of a combustion gas and comprising or essentially consisting of a nickel-based NH3 decomposition catalyst; (h) decomposing the NH3 on the catalyst bed in the at least one tubular reactor to obtain a product gas comprising or essentially consisting of H2, N2 and optionally undecomposed NH3; and (i) withdrawing the product gas from the at least one tubular reactor at a gas temperature T4 in the range of 550-750 °C and a pressure p4 of at least 10 bar a.

[0036] In step (a) of the process of the present application, a reactant gas comprising or essentially consisting of NH3 is provided.

[0037] In a preferred embodiment, the NH3 is stored in a cryogenic liquid state, thus being essentially pure, and therefore the reactant gas preferably essentially consists of NH3.

[0038] The NH3 is preferably synthetic NH3 which has been prepared from N2 and H2, the H2 preferably being obtained by electrolysis of water, and the electricity used for the electrolysis preferably being from renewable energy sources, preferably solar (in particular photovoltaic) and / or wind energy.

[0039] In step (b) of the process of the present application, the reactant gas provided in advance in step (a) is heated to a gas temperature T1 in the range of 550-850 °C at a pressure pi of at least 10 bara.

[0040] T1 is preferably in the range of 550-700 °C.

[0041] Preferably, T1 is at least 595 °C, preferably at least 600 °C, more preferably at least 605 °C, even more preferably at least 610 °C, most preferably at least 615 °C, and in particular at least 620 °C. Preferably, T1 is at least 625 °C, preferably at least 630 °C, more preferably at least 635 °C, even more preferably at least 640 °C, most preferably at least 645 °C, and in particular at least 650 °C.

[0042] Preferably, T1 is at most 710 °C, preferably at most 705 °C, more preferably at most 700 °C, even more preferably at most 695 °C, most preferably at most 690 °C, and in particular at most 685 °C. Preferably, T1 is at most 680 °C, preferably at most 675 °C, more preferably at most 670 °C, even more preferably at most 665 °C, most preferably at most 660 °C, and in particular at most 655 °C.

[0043] Preferably, p1 is at least 12 bar a, preferably at least 14 bar a, more preferably at least 16 bar a, even more preferably at least 18 bar a, most preferably at least 20 bar a, and in particular at least 22 bar a.

[0044] Preferably, p1 is at most 80 bar a, preferably at most 70 bar a, more preferably at most 60 bar a, even more preferably at most 50 bar a, most preferably at most 40 bar a, and in particular at most 30 bar a.

[0045] In step (c) of the process of the present application, the reactant gas, which was previously heated in step (b), is introduced into at least one fixed bed reactor at a gas temperature T1 and a pressure p1, which contains at least one catalyst bed comprising or essentially consisting of an NH3 decomposition catalyst.

[0046] The at least one catalyst bed of the fixed bed reactor is preferably not heated.

[0047] Preferably, the at least one fixed bed reactor is operated adiabatically.

[0048] The NH3 decomposition catalyst of the at least one catalyst bed of the fixed bed reactor is nickel-based, preferably supported nickel.

[0049] Preferably, the nickel-based NH3 decomposition catalyst for NH3 decomposition of the at least one catalyst bed of the fixed bed reactor has an (apparent) activation energy of not more than 240 kJ·mol -1 ; preferably not more than 230 kJ·mol -1 , more preferably not more than 220 kJ·mol -1 , even more preferably not more than 210 kJ·mol -1most preferably not more than 200 kJ mol -1 , and in particular not more than 190 kJ mol -1 .

[0050] Preferably, the nickel-based NH3 decomposition catalyst of at least one catalyst bed of the fixed bed reactor for NH3 decomposition has an (apparent) activation energy of not more than 180 kJ mol -1 ; preferably not more than 170 kJ mol -1 , more preferably not more than 160 kJ mol -1 , even more preferably not more than 150 kJ mol -1 , most preferably not more than 140 kJ mol -1 , and in particular not more than 130 kJ mol -1 .

[0051] In preferred embodiments, the at least one fixed bed reactor comprises a first catalyst bed and a second catalyst bed, wherein the first catalyst bed comprises a first NH3 decomposition catalyst and the second catalyst bed comprises a second NH3 decomposition catalyst, wherein the second catalyst bed is arranged downstream of the first catalyst bed in the flow direction of the reactant gas or the intermediate product gas.

[0052] In preferred embodiments, the first NH3 decomposition catalyst and the second NH3 decomposition catalyst are the same.

[0053] In other preferred embodiments, the first NH3 decomposition catalyst and the second NH3 decomposition catalyst are different.

[0054] Preferably, the second NH3 decomposition catalyst has a higher (apparent) activation energy for NH3 decomposition than the first NH3 decomposition catalyst.

[0055] In preferred embodiments, at least one catalyst bed of the fixed bed reactor is essentially cylindrical, through which the reactant gas or the intermediate product gas flows in axial direction.

[0056] In other preferred embodiments, at least one catalyst bed of the fixed bed reactor is essentially hollow-cylindrical, through which the reactant gas or the intermediate product gas flows in radial direction.

[0057] Preferably, at least one catalyst bed of the fixed bed reactor has an essentially circular cross-section with a diameter of at least 80 cm, preferably at least 100 cm, preferably at least 120 cm, more preferably at least 140 cm, preferably at least 160 cm, and in particular at least 180 cm.

[0058] Preferably, the at least one catalyst bed of the fixed bed reactor has a length of at least 80 cm, preferably at least 100 cm, preferably at least 120 cm, more preferably at least 140 cm, most preferably at least 160 cm, and in particular at least 180 cm in the flow direction of the reactant gas or of the intermediate product gas.

[0059] Preferably, the at least one catalyst bed of the fixed bed reactor has a space velocity of 5000 to 25000 h -1 , preferably 10000 to 20000 h -1 , more preferably 12500 to 17500 h -1 .

[0060] In step (d) of the process of the present application, NH3 is partially decomposed in the at least one fixed bed reactor on the at least one catalyst bed to obtain an intermediate product gas comprising or essentially consisting of H2, N2 and un-decomposed NH3.

[0061] Preferably, in step (d), the conversion of decomposed NH3 is at least 12.5 %, preferably at least 15 %, more preferably at least 17.5 %, even more preferably at least 20 %, most preferably at least 22.5 %, and in particular at least 25 %, each based on the amount of NH3 originally present in the reactant gas provided in step (a).

[0062] Preferably, in step (d), the conversion of NH3 is not more than 42.5 %, preferably not more than 40 %, more preferably not more than 37.5 %, even more preferably not more than 35 %, most preferably not more than 32.5 %, and in particular not more than 30 %, each based on the amount of NH3 originally present in the reactant gas provided in step (a).

[0063] In step (e) of the process of the present application, the intermediate product gas previously obtained in step (d) is discharged from the at least one fixed bed reactor at a gas temperature T2 in the range of 300 to 700 °C and a pressure p2 of at least 10 bar a.

[0064] T2 is preferably in the range of 300 to 690 °C.

[0065] Preferably, T2 is at least 300 °C, preferably at least 310 °C, more preferably at least 320 °C, even more preferably at least 330 °C, most preferably at least 340 °C, and in particular at least 350 °C. Preferably, T2 is at least 400 °C, preferably at least 410 °C, more preferably at least 420 °C, even more preferably at least 430 °C, most preferably at least 440 °C, and in particular at least 450 °C.

[0066] Preferably, T2 is at most 510°C, more preferably at most 500°C, more preferably at most 490°C, even more preferably at most 480°C, most preferably at most 470°C, and particularly at most 460°C. Preferably, T2 is at most 410°C, more preferably at most 400°C, more preferably at most 390°C, even more preferably at most 380°C, most preferably at most 370°C, and particularly at most 360°C.

[0067] Preferably, p2 is at least 12 bar a, more preferably at least 14 bar a, more preferably at least 16 bar a, even more preferably at least 18 bar a, most preferably at least 20 bar a, and particularly at least 22 bar a.

[0068] Preferably, p2 is at most 80 bar a, more preferably at most 70 bar a, more preferably at most 60 bar a, even more preferably at most 50 bar a, most preferably at most 40 bar a, and particularly at most 30 bar a.

[0069] Preferably, T1 > T2.

[0070] Preferably, the relative temperature difference |T1-T2| is at least 50°C, more preferably at least 75°C, even more preferably at least 100°C, most preferably at least 125°C, and particularly at least 150°C. Preferably, the relative temperature difference |T1-T2| is at least 175°C, more preferably at least 200°C, even more preferably at least 225°C, most preferably at least 250°C, and particularly at least 275°C.

[0071] In a preferred embodiment, -T1 is within the range of 650±50℃, preferably 650±40℃, more preferably 650±30℃, even more preferably 650±20℃, and most preferably 650±10℃; and -T2 is in the range of 450±50℃, preferably 450±40℃, more preferably 450±30℃, even more preferably 450±20℃, and most preferably 450±10℃.

[0072] In other preferred embodiments, -T1 is within the range of 650±50℃, preferably 650±40℃, more preferably 650±30℃, even more preferably 650±20℃, and most preferably 650±10℃; and -T2 is in the range of 350±50℃, preferably 350±40℃, more preferably 350±30℃, even more preferably 350±20℃, and most preferably 350±10℃.

[0073] Preferably, p1 > p2.

[0074] Preferably, the relative pressure difference has a magnitude |p3-p2| of at most 6 bar, preferably of at most 5 bar, more preferably of at most 4 bar, even more preferably of at most 3 bar, most preferably of at most 2 bar, and in particular of at most 1 bar.

[0075] Preferably, T3 > T2.

[0076] Preferably, the relative temperature difference has a magnitude |T3-T2| of at least 20°C, more preferably of at least 40°C, even more preferably of at least 60°C, most preferably of at least 80°C, and in particular of at least 100°C.

[0077] Preferably, the relative temperature difference has a magnitude |T3-T2| of at least 110°C, more preferably of at least 120°C, even more preferably of at least 130°C, most preferably of at least 140°C, and in particular of at least 150°C.

[0078] In preferred embodiments, - T2 is in the range of 450 ± 50°C, preferably of 450 ± 40°C, more preferably of 450 ± 30°C, even more preferably of 450 ± 20°C, most preferably of 450 ± 10°C; and - T3 is in the range of 620 ± 50°C, preferably of 620 ± 40°C, more preferably of 620 ± 30°C, even more preferably of 620 ± 20°C, most preferably of 620 ± 10°C; In other preferred embodiments, - T2 is in the range of 350 ± 50°C, preferably of 350 ± 40°C, more preferably of 350 ± 30°C, even more preferably of 350 ± 20°C, most preferably of 350 ± 10°C; and - T3 is in the range of 620 ± 50°C, preferably of 620 ± 40°C, more preferably of 620 ± 30°C, even more preferably of 620 ± 20°C, most preferably of 620 ± 10°C.

[0079] Preferably, p3 > p2.

[0080] Preferably, the relative pressure difference has a magnitude |p3-p2| of at most 6 bar, preferably of at most 5 bar, more preferably of at most 4 bar, even more preferably of at most 3 bar, most preferably of at most 2 bar, and in particular of at most 1 bar.

[0081] In preferred embodiments, T3 > T1.

[0082] In other preferred embodiments, T3 < T1.

[0083] Preferably, the magnitude of the relative temperature difference | T1-T3 | is at least 5°C, more preferably at least 10°C, even more preferably at least 15°C, most preferably at least 20°C, and in particular at least 25°C. Preferably, the magnitude of the relative temperature difference | T1-T3 | is at least 30°C, more preferably at least 35°C, even more preferably at least 40°C, most preferably at least 45°C, and in particular at least 50°C.

[0084] Preferably, the magnitude of the relative temperature difference | T1-T3 | is at most 50°C, more preferably at most 45°C, even more preferably at most 40°C, most preferably at most 35°C, and in particular at most 30°C. Preferably, the magnitude of the relative temperature difference | T1-T3 | is at most 25°C, more preferably at most 20°C, even more preferably at most 15°C, most preferably at most 10°C, and in particular at most 5°C.

[0085] In a preferred embodiment, - T1 is in the range of 650 ± 50°C, preferably 650 ± 40°C, more preferably 650 ± 30°C, even more preferably 650 ± 20°C, most preferably 650 ± 10°C; and - T3 is in the range of 620 ± 50°C, preferably 620 ± 40°C, more preferably 620 ± 30°C, even more preferably 620 ± 20°C, most preferably 620 ± 10°C.

[0086] Preferably, p3 < p1.

[0087] Preferably, the magnitude of the relative pressure difference | p3-p1 | is at most 6 bar, preferably at most 5 bar, more preferably at most 4 bar, even more preferably at most 3 bar, most preferably at most 2 bar, and in particular at most 1 bar.

[0088] Preferably, the nickel-based NH3 decomposition catalyst of the respective at least one catalyst bed of the plurality of tubes of the tubular reactor is a supported nickel.

[0089] Preferably, the nickel-based NH3 decomposition catalyst of the respective at least one catalyst bed of the plurality of tubes of the tubular reactor for NH3 decomposition has an (apparent) activation energy of at most 240 kJ· mol -1 ; preferably not more than 230 kJ· mol -1 , more preferably not more than 220 kJ· mol -1 , even more preferably not more than 210 kJ· mol -1 , most preferably not more than 200 kJ· mol -1 , and in particular not more than 190 kJ· mol -1 .

[0090] Preferably, the nickel-based NH3 decomposition catalyst of the at least one catalyst bed of the respective one of the plurality of tubes of the tubular reactor for NH3 decomposition has an (apparent) activation energy of at most 180 kJ mol -1 ; preferably not more than 170 kJ mol -1 , more preferably not more than 160 kJ mol -1 , even more preferably not more than 150 kJ mol -1 , most preferably not more than 140 kJ mol -1 , and in particular not more than 130 kJ mol -1 .

[0091] The preferred support material is selected from the group consisting of AI2O3, MgO, SiO2, mesoporous SiO2(e.g. MCF-17, MCM-41, SBA-15), zeolites (e.g. HY, H-ZSM-5), BaMnO3, BaTiO3, BaZrO3, CaMnO3, CaTiO3, CaZrO3, CeO2, Gd2O3, GdAlO3, KNbO3, La2O3, LaAlO3, MnO2, NaNbO3, Nb2O5, Sm2O3, SmAlO3, SrMnO3, SrTiO3, SrZrO3, TiO2, Y2O3, ZrO2, carbon (e.g. CNT, SWCNT, AX-21, MSC-30, MESO-C, GNP, activated carbon, graphene, graphene oxide), attapulgite, bayerite, sepiolite and mixtures thereof.

[0092] In step (f) of the process of the present application, the intermediate product gas is heated to a gas temperature T3 in the range of 550 °C to 700 °C at a pressure p3 of at least 10 bar a.

[0093] Preferably, T3 is in the range of 560 °C to 700 °C.

[0094] Preferably, T3 is at least 590 °C, preferably at least 595 °C, more preferably at least 600 °C, even more preferably at least 605 °C, most preferably at least 610 °C, and in particular at least 615 °C.

[0095] Preferably, T3 is at most 650 °C, preferably at most 645 °C, more preferably at most 640 °C, even more preferably at most 635 °C, most preferably at most 630 °C, and in particular at most 625 °C.

[0096] Preferably, p3 is at least 12 bar a, preferably at least 14 bar a, more preferably at least 16 bar a, even more preferably at least 18 bar a, most preferably at least 20 bar a, and in particular at least 22 bar a.

[0097] Preferably, p3 is at most 80 bar a, preferably at most 70 bar a, more preferably at most 60 bar a, even more preferably at most 50 bar a, most preferably at most 40 bar a, and in particular at most 30 bar a.

[0098] In step (g) of the process of the present application, the intermediate product gas, which was previously heated in step (f), is introduced into at least one tubular reactor at a gas temperature T3 and a pressure p3, which tubular reactor comprises a plurality of parallel tubes, each parallel tube comprising at least one catalyst bed, which catalyst bed is heated by combustion of a combustion gas and comprises or essentially consists of a nickel-based NH3 decomposition catalyst.

[0099] Preferably, the number of parallel tubes in the tubular reactor is at least 50, preferably at least 100, more preferably at least 150, even more preferably at least 200, most preferably at least 250, and in particular at least 300.

[0100] Preferably, the plurality of parallel tubes of the tubular reactor each has a length L in the flow direction of the intermediate product gas or product gas R of at least 5.5 m, preferably at least 6.0 m, more preferably at least 6.5 m, even more preferably at least 8 m, most preferably at least 7.0 m, and in particular at least 7.5 m.

[0101] Preferably, the plurality of parallel tubes of the tubular reactor has a substantially circular cross-section in the flow direction of the intermediate product gas or product gas, which cross-section has an inner diameter of at least 5.0 cm, preferably at least 5.5 cm, more preferably at least 6.0 cm, even more preferably at least 6.5 cm, most preferably at least 7.0 cm, and in particular at least 7.5 cm.

[0102] Preferably, the plurality of parallel tubes of the tubular reactor has a substantially circular cross-section in the flow direction of the intermediate product gas or product gas, which cross-section has an inner diameter of at most 12 cm, preferably at most 11 cm, more preferably at most 10 cm, even more preferably at most 9.5 cm, preferably at most 9.0 cm, and in particular at most 8.5 cm.

[0103] Preferably, the catalyst bed of the tubular reactor has a total space velocity of 500 to 15000 h -1 , preferably 1000 to 10000 h -1 , more preferably 2500 to 7500 h -1 .

[0104] Preferably, the at least one catalyst bed of the fixed bed reactor has a greater space velocity than the total of the catalyst beds of the tubular reactor.

[0105] In step (h) of the process of the present application, the NH3 is decomposed in the at least one tubular reactor over a catalyst bed to obtain a product gas comprising or essentially consisting of H2, N2 and optionally un-decomposed NH3.

[0106] Preferably, in step (h), the conversion of decomposed NH3 is at least 90%, preferably at least 92.5%, more preferably at least 95%, even more preferably at least 96%, most preferably at least 97%, and in particular at least 98%, based on the amount of NH3 originally present in the reactant gas provided in step (a).

[0107] In step (i) of the process of the present application, the product gas obtained in step (h) beforehand is discharged from the at least one tubular reactor at a gas temperature T4 in the range of 550 °C to 750 °C and a pressure p4 of at least 10 bar a.

[0108] Preferably, T4 is in the range of 560 °C to 750 °C.

[0109] Preferably, T4 is at least 650 °C, preferably at least 655 °C, more preferably at least 660 °C, even more preferably at least 665 °C, most preferably at least 670 °C, and in particular at least 675 °C.

[0110] Preferably, T4 is at most 710 °C, preferably at most 705 °C, more preferably at most 700 °C, even more preferably at most 695 °C, most preferably at most 690 °C, and in particular at most 685 °C.

[0111] Preferably, p4 is at least 12 bar a, preferably at least 14 bar a, more preferably at least 16 bar a, even more preferably at least 18 bar a, most preferably at least 20 bar a, and in particular at least 22 bar a.

[0112] Preferably, p4 is at most 80 bar a, preferably at most 70 bar a, more preferably at most 60 bar a, even more preferably at most 50 bar a, most preferably at most 40 bar a, and in particular at most 30 bar a.

[0113] Preferably, T4 > T3.

[0114] Preferably, the magnitude of the relative temperature difference |T3-T4| is at least 10 °C, more preferably at least 15 °C, even more preferably at least 20 °C, most preferably at least 25 °C, and in particular at least 30 °C.

[0115] Preferably, the magnitude of the relative temperature difference | T3 - T4 | is at least 35°C, more preferably at least 40°C, even more preferably at least 45°C, most preferably at least 50°C, and in particular at least 55°C.

[0116] Preferably, the magnitude of the relative temperature difference | T3 - T4 | is at most 55°C, more preferably at most 50°C, even more preferably at most 45°C, most preferably at most 40°C, and in particular at most 35°C.

[0117] Preferably, the magnitude of the relative temperature difference | T3 - T4 | is at most 30°C, more preferably at most 25°C, even more preferably at most 20°C, most preferably at most 15°C, and in particular at most 10°C.

[0118] In a preferred embodiment, T3 is in the range of 620 ± 50°C, preferably 620 ± 40°C, more preferably 620 ± 30°C, even more preferably 620 ± 20°C, most preferably 620 ± 10°C; and T4 is in the range of 650 ± 50°C, preferably 650 ± 40°C, more preferably 650 ± 30°C, even more preferably 650 ± 20°C, most preferably 650 ± 10°C.

[0119] Preferably, p4 > p3.

[0120] Preferably, the magnitude of the relative pressure difference | p3 - p4 | is at most 6 bar, preferably at most 5 bar, more preferably at most 4 bar, even more preferably at most 3 bar, most preferably at most 2 bar, and in particular at most 1 bar.

[0121] Preferably, the combustion gas is combusted with at least one burner, resulting in at least one flame through which the thermal energy is introduced into the tube, wherein the thermal energy flow Q w over the length L R of the tube has a non-constant progression.

[0122] Preferably, the thermal energy flow Q w over the length L R of the tube has a maximum.

[0123] Preferably, the tube can conceptually be divided into two equal halves over the length L R of the tube, wherein the intermediate product gas or product gas first flows through the first half and then through the second half, wherein a maximum of the thermal energy flow Q w is reached in the first half.

[0124] Preferably, the tube can conceptually be divided into two equal halves over the length L REach section is divided into four equal segments. The intermediate product gas or product gas first flows through the first segment, then through the second segment, and finally through the third segment, followed by the fourth segment. The heat energy flow Q is reached in the second segment. w The maximum value.

[0125] The combustion gases are preferably burned by at least one burner to produce at least one flame of length L. F Basically parallel to the length L of the tube R It extends in the direction of the flow of the combustion gases.

[0126] Preferably, the combustion gases flow substantially in the same direction as the intermediate or product gases (roof combustion).

[0127] Preferably, L R >L F .

[0128] Preferably, the length ratio L R :L F Within the range of 10:1 to 1.1:1, preferably 7:1 to 1.5:1, and more preferably 4:1 to 2:1.

[0129] Preferably, when the intermediate product gas or product gas flows through the tube in step (h), the amount of heat consumed by the endothermic decomposition of NH3 is initially greater than the amount of heat energy Q. w The amount of heat introduced into the tube by the combustion of the combustion gases is such that the intermediate product gas or product gas is initially cooled to a minimum gas temperature T during its flow through the tube. min (T min <T3)。

[0130] Preferably, the relative temperature difference is |T3-T min The temperature is at least 10°C, more preferably at least 20°C, even more preferably at least 30°C, most preferably at least 30°C, and particularly at least 40°C.

[0131] Preferably, T min The temperature range is 560 to 600°C, preferably 570 to 590°C.

[0132] Preferably, when the minimum gas temperature T is reached min At that time, the amount of heat consumed in the endothermic decomposition of NH3 is subsequently less than the heat energy flow Q. w The amount of heat introduced into the tube by the combustion of the combustion gases causes the intermediate product gas or product gas to be subsequently heated (T) as it flows through the tube. min <T4)。

[0133] Preferably, the relative temperature difference is |T4-T min| is at least 50°C, more preferably at least 55°C, even more preferably at least 60°C, most preferably at least 65°C, and in particular at least 70°C.

[0134] Preferably, the tube can be conceptually divided in the length L of the tube into two equal halves, wherein the intermediate product gas or product gas first flows through the first half and then through the second half, wherein the minimum gas temperature T R m .

[0135] Preferably, the tube can be conceptually divided in the length L of the tube into four equal segments, wherein the intermediate product gas or product gas first flows through the first segment, then the second segment, then the third segment and subsequently the fourth segment, with the minimum gas temperature T R m .

[0136] In preferred embodiments, - T1 is in the range of 650 ± 50°C, preferably 650 ± 40°C, more preferably 650 ± 30°C, even more preferably 650 ± 20°C, most preferably 650 ± 10°C; - T2 is in the range of 450 ± 50°C, preferably 450 ± 40°C, more preferably 450 ± 30°C, even more preferably 450 ± 20°C, most preferably 450 ± 10°C; - T3 is in the range of 620 ± 50°C, preferably 620 ± 40°C, more preferably 620 ± 30°C, even more preferably 620 ± 20°C, most preferably 620 ± 10°C; and - T4 is in the range of 650 ± 50°C, preferably 650 ± 40°C, more preferably 650 ± 30°C, even more preferably 650 ± 20°C, most preferably 650 ± 10°C.

[0137] In other preferred embodiments, - T1 is in the range of 650 ± 50°C, preferably 650 ± 40°C, more preferably 650 ± 30°C, even more preferably 650 ± 20°C, most preferably 650 ± 10°C; - T2 is in the range of 350 ± 50°C, preferably 350 ± 40°C, more preferably 350 ± 30°C, even more preferably 350 ± 20°C, most preferably 350 ± 10°C; - T3 is in the range of 620 ± 50°C, preferably 620 ± 40°C, more preferably 620 ± 30°C, even more preferably 620 ± 20°C, most preferably 620 ± 10°C; and - T4 is in the range of 650 ± 50°C, preferably 650 ± 40°C, more preferably 650 ± 30°C, even more preferably 650 ± 20°C, most preferably 650 ± 10°C.​​

[0138] Preferably, the combustion gas comprises NH3; preferably, the reactant gas provided in step (a) is divided into (i) a first portion which is fed to step (b), and (ii) a second portion which is used as combustion gas.

[0139] Preferably, the second portion is not more than 8.0 mol%, preferably not more than 7.5 mol%, more preferably not more than 7.0 mol%, most preferably not more than 6.5 mol%, and in particular not more than 5 mol% of the reactant gas provided in step (a).

[0140] The method preferably comprises the further step of: (j) adsorptive cleaning of the product gas by pressure swing to obtain an H2-rich product gas and an H2-lean tail gas; preferably wherein the H2-lean tail gas is recycled and introduced into the combustion gas.

[0141] Another aspect of the present application relates to an apparatus for carrying out the above-mentioned method of the present application.

[0142] Preferred embodiments of the present application are summarized below as items 1 to 103: Item 1 : A method for the production of H2 from NH3, comprising the steps of: (a) providing a reactant gas comprising or consisting essentially of NH3; (b) heating the reactant gas to a gas temperature T1 in the range of 550-850 °C at a pressure p1 of at least 10 bar a; (c) introducing the heated reactant gas at the gas temperature T1 and the pressure p1 into at least one fixed bed reactor, said fixed bed reactor containing at least one catalyst bed, said catalyst bed comprising or consisting essentially of a NH3 decomposition catalyst; (d) partially decomposing the NH3 on the at least one catalyst bed in the at least one fixed bed reactor to obtain an intermediate product gas comprising or consisting essentially of H2, N2 and un-decomposed NH3; (e) withdrawing the intermediate product gas from the at least one fixed bed reactor at a gas temperature T2 in the range of 300-700 °C and a pressure p2 of at least 10 bar a; (f) heating the intermediate product gas to a gas temperature T3 in the range of 550-700 °C at a pressure p3 of at least 10 bar a; (g) introducing the heated intermediate product gas at the gas temperature T3 and the pressure p3 into at least one tubular reactor, said tubular reactor comprising a plurality of parallel tubes, each tube containing at least one catalyst bed, said catalyst bed being heated by combustion of a combustion gas and comprising or consisting essentially of a nickel-based NH3 decomposition catalyst; (h) decomposing the NH3 on the catalyst bed in the at least one tubular reactor to obtain a product gas comprising or consisting essentially of H2, N2 and optionally un-decomposed NH3; and (i) withdrawing the product gas from the at least one tubular reactor at a gas temperature T4 in the range of 550-750 °C and a pressure p4 of at least 10 bar a.

[0143] Item 2: The method according to item 1, wherein at least one catalyst bed of the fixed bed reactor is not heated.

[0144] Item 3: The method according to item 1 or 2, wherein at least one fixed bed reactor is operated adiabatically.

[0145] Item 4: The method according to any one of the preceding items, wherein the NH3 decomposition catalyst in at least one catalyst bed of the fixed bed reactor is nickel-based, preferably supported nickel.

[0146] Item 5: The method according to any one of the preceding items, wherein the nickel-based NH3 decomposition catalyst for NH3 decomposition of at least one catalyst bed of the fixed bed reactor has an (apparent) activation energy of not more than 240 kJ-mol -1 ; preferably not more than 230 kJ-mol -1 , more preferably not more than 220 kJ-mol -1 , even more preferably not more than 210 kJ-mol -1 , most preferably not more than 200 kJ-mol -1 , and in particular not more than 190 kJ-mol -1 .

[0147] Item 6: The method according to any one of the preceding items, wherein the nickel-based NH3 decomposition catalyst for NH3 decomposition of at least one catalyst bed of the fixed bed reactor has an (apparent) activation energy of not more than 180 kJ-mol -1 ; preferably not more than 170 kJ-mol -1 , more preferably not more than 160 kJ-mol -1 , even more preferably not more than 150 kJ-mol -1 , most preferably not more than 140 kJ-mol -1 , and in particular not more than 130 kJ-mol -1 .

[0148] Item 7: The method according to any one of the preceding items, wherein the at least one fixed bed reactor comprises a first catalyst bed comprising a first NH3 decomposition catalyst and a second catalyst bed comprising a second NH3 decomposition catalyst, wherein the second catalyst bed is arranged downstream of the first catalyst bed in the flow direction of the reactant gas or intermediate product gas.

[0149] Item 8: The method according to item 7, wherein the first NH3 decomposition catalyst and the second NH3 decomposition catalyst are identical.

[0150] Item 9: The method according to item 7, wherein the first and the second NH3 decomposition catalysts are different.

[0151] Item 10: The method according to item 9, wherein the second NH3 decomposition catalyst has a higher apparent activation energy (for NH3 decomposition) than the first NH3 decomposition catalyst.

[0152] Item 11 : The method according to any one of the preceding items, wherein the at least one catalyst bed of the fixed bed reactor is essentially cylindrical, with the reactant gas or intermediate product gas flowing axially through the cylinder.

[0153] Item 12: The method according to any one of the preceding items, wherein the at least one catalyst bed of the fixed bed reactor is essentially hollow-cylindrical, with the reactant gas or intermediate product gas flowing radially through the hollow cylinder.

[0154] Item 13: The method according to any one of the preceding items, wherein the at least one catalyst bed of the fixed bed reactor has an essentially circular cross-section with a diameter of at least 80 cm, preferably at least 100 cm, more preferably at least 120 cm, more preferably at least 140 cm, most preferably at least 160 cm, and in particular at least 180 cm.

[0155] Item 14: The method according to any one of the preceding items, wherein the at least one catalyst bed of the fixed bed reactor has a length in the flow direction of the reactant gas or intermediate product gas of at least 80 cm, preferably at least 100 cm, more preferably at least 120 cm, more preferably at least 140 cm, most preferably at least 160 cm, and in particular at least 180 cm.

[0156] Item 15: The method according to any one of the preceding items, wherein the at least one catalyst bed of the fixed bed reactor has a space velocity of 5000-25000 h -1 , preferably 10000-20000 h -1 , more preferably 12500-17500 h -1

[0157] Item 16: The method according to any one of the preceding items, wherein T1 is in the range of 550-700 °C.

[0158] Item 17: The method according to any one of the preceding items, wherein T1 is at least 595 °C, preferably at least 600 °C, more preferably at least 605 °C, even more preferably at least 610 °C, most preferably at least 615 °C, and in particular at least 620 °C.

[0159] ​Item 18: The method according to any of the preceding items, wherein T1 is at least 625 °C, preferably at least 630 °C, more preferably at least 635 °C, even more preferably at least 640 °C, most preferably at least 645 °C, and in particular at least 650 °C.

[0160] Item 19: The method according to any of the preceding items, wherein T1 is at most 710 °C, preferably at most 705 °C, more preferably at most 700 °C, even more preferably at most 695 °C, most preferably at most 690 °C, and in particular at most 685 °C.

[0161] Item 20: The method according to any of the preceding items, wherein T1 is at most 680 °C, preferably at most 675 °C, more preferably at most 670 °C, even more preferably at most 665 °C, most preferably at most 660 °C, and in particular at most 655 °C.

[0162] Item 21 : The method according to any of the preceding items, wherein p1 is at least 12 bar a, preferably at least 14 bara, more preferably at least 16 bar a, even more preferably at least 18 bar a, most preferably at least 20 bar a, and in particular at least 22 bar a.

[0163] Item 22: The method according to any of the preceding items, wherein p1 is at most 80 bar a, preferably at most 70 bara, more preferably at most 60 bar a, even more preferably at most 50 bar a, most preferably at most 40 bar a, and in particular at most 30 bar a.

[0164] Item 23: The method according to any of the preceding items, wherein T2 is in the range of 300-690 °C.

[0165] Item 24: The method according to any of the preceding items, wherein T2 is at least 300 °C, preferably at least 310 °C, more preferably at least 320 °C, even more preferably at least 330 °C, most preferably at least 340 °C, and in particular at least 350 °C.

[0166] Item 25: The method according to any of the preceding items, wherein T2 is at least 400 °C, preferably at least 410 °C, more preferably at least 420 °C, even more preferably at least 430 °C, most preferably at least 440 °C, and in particular at least 450 °C.

[0167] Item 26: The method according to any of the preceding items, wherein T2 is at most 510 °C, preferably at most 500 °C, more preferably at most 490 °C, even more preferably at most 480 °C, most preferably at most 470 °C, and in particular at most 460 °C.

[0168] Item 27: The method according to any of the preceding items, wherein T2 is at most 410 °C, preferably at most 400 °C, more preferably at most 390 °C, even more preferably at most 380 °C, most preferably at most 370 °C, and in particular at most 360 °C.

[0169] Item 28: The method according to any of the preceding items, wherein p2 is at least 12 bar a, preferably at least 14 bara, more preferably at least 16 bar a, even more preferably at least 18 bar a, most preferably at least 20 bar a, and in particular at least 22 bar a.

[0170] Item 29: The method according to any of the preceding items, wherein p2 is at most 80 bar a, preferably at most 70 bara, more preferably at most 60 bar a, even more preferably at most 50 bar a, most preferably at most 40 bar a, and in particular at most 30 bar a.

[0171] Item 30: The method according to any of the preceding items, wherein T1 > T2.

[0172] Item 31 : The method according to any of the preceding items, wherein the magnitude of the relative temperature difference |T1 - T2| is at least 50 °C, more preferably at least 75 °C, even more preferably at least 100 °C, most preferably at least 125 °C, and in particular at least 150 °C.

[0173] Item 32: The method according to any of the preceding items, wherein the magnitude of the relative temperature difference |T1 - T2| is at least 175 °C, more preferably at least 200 °C, even more preferably at least 225 °C, most preferably at least 250 °C, and in particular at least 275 °C.

[0174] Item 33: The method according to any of the preceding items, wherein - T1 is in the range of 650 ± 50 °C, preferably 650 ± 40 °C, more preferably 650 ± 30 °C, even more preferably 650 ± 20 °C, most preferably 650 ± 10 °C; and - T2 is in the range of 450 ± 50 °C, preferably 450 ± 40 °C, more preferably 450 ± 30 °C, even more preferably 450 ± 20 °C, most preferably 450 ± 10 °C.

[0175] Item 34: The method according to any of items 1 to 32, wherein - T1 is in the range of 650 ± 50 °C, preferably 650 ± 40 °C, more preferably 650 ± 30 °C, even more preferably 650 ± 20 °C, most preferably 650 ± 10 °C; and - T2 is in the range of 350 ± 50 °C, preferably 350 ± 40 °C, more preferably 350 ± 30 °C, even more preferably 350 ± 20 °C, most preferably 350 ± 10 °C.

[0176] Item 35: The method according to any of the preceding items, wherein pi > p2.

[0177] Item 36: The method according to any of the preceding items, wherein the magnitude of the relative pressure difference | pi - p2 | is at most 6 bar, preferably at most 5 bar, more preferably at most 4 bar, even more preferably at most 3 bar, most preferably at most 2 bar, and in particular at most 1 bar.

[0178] Item 37: The method according to any of the preceding items, wherein the conversion of NH3 decomposed in step (d) is at least 12.5 %, preferably at least 15 %, more preferably at least 17.5 %, even more preferably at least 20 %, most preferably at least 22.5 %, and in particular at least 25 %, each based on the amount of NH3 originally present in the reactant gas provided in step (a).

[0179] Item 38: The method according to any of the preceding items, wherein the conversion of NH3 in step (d) is at most 42.5 %, preferably at most 40 %, more preferably at most 37.5 %, even more preferably at most 35 %, most preferably at most 32.5 %, and in particular at most 30 %, each based on the amount of NH3 originally present in the reactant gas provided in step (a).

[0180] Item 39: The method according to any of the preceding items, wherein T3 > T2.

[0181] Item 40: The method according to any of the preceding items, wherein the magnitude of the relative temperature difference | T3 - T2 | is at least 20 °C, more preferably at least 40 °C, even more preferably at least 60 °C, most preferably at least 80 °C, and in particular at least 100 °C.

[0182] Item 41 : The method according to any of the preceding items, wherein the magnitude of the relative temperature difference | T3 - T2 | is at least 110 °C, more preferably at least 120 °C, even more preferably at least 130 °C, most preferably at least 140 °C, and in particular at least 150 °C.

[0183] Item 42: The method according to any of the preceding items, wherein - T2 is in the range of 450 ± 50 °C, preferably 450 ± 40 °C, more preferably 450 ± 30 °C, even more preferably 450 ± 20 °C, most preferably 450 ± 10 °C; and - T3 is in the range of 620 ± 50 °C, preferably 620 ± 40 °C, more preferably 620 ± 30 °C, even more preferably 620 ± 20 °C, most preferably 620 ± 10 °C.

[0184] Item 43: The method according to any of the preceding items, wherein - T2 is in the range of 350 ± 50 °C, preferably 350 ± 40 °C, more preferably 350 ± 30 °C, even more preferably 350 ± 20 °C, most preferably 350 ± 10 °C; and - T3 is in the range of 620 ± 50 °C, preferably 620 ± 40 °C, more preferably 620 ± 30 °C, even more preferably 620 ± 20 °C, most preferably 620 ± 10 °C.

[0185] Item 44: The method according to any of the preceding items, wherein p3 > p2.

[0186] Item 45: The method according to any of the preceding items, wherein the magnitude of the relative pressure difference | p3 - p2 | is at most 6 bar, preferably at most 5 bar, more preferably at most 4 bar, even more preferably at most 3 bar, most preferably at most 2 bar, and in particular at most 1 bar.

[0187] Item 46: The method according to any of the preceding items, wherein T3 > T1.

[0188] Item 47: The method according to any of the preceding items, wherein T3 < T1.

[0189] Item 48: The method according to any of the preceding items, wherein the magnitude of the relative temperature difference | T1 - T3 | is at least 5 °C, more preferably at least 10 °C, even more preferably at least 15 °C, most preferably at least 20 °C, and in particular at least 25 °C.

[0190] Item 49: The method according to any of the preceding items, wherein the magnitude of the relative temperature difference | T1 - T3 | is at least 30 °C, more preferably at least 35 °C, even more preferably at least 40 °C, most preferably at least 45 °C, and in particular at least 50 °C.

[0191] Item 50: The method according to any of the preceding items, wherein the magnitude of the relative temperature difference | T1 - T3 | is at most 50 °C, more preferably at most 45 °C, even more preferably at most 40 °C, most preferably at most 35 °C, and in particular at most 30 °C.

[0192] Item 51 : The method according to any of the preceding items, wherein the magnitude of the relative temperature difference | T1 - T3 | is at most 25 °C, more preferably at most 20 °C, even more preferably at most 15 °C, most preferably at most 10 °C, and in particular at most 5 °C.

[0193] Item 52: The method according to any of the preceding items, wherein - T1 is in the range of 650 ± 50 °C, preferably 650 ± 40 °C, more preferably 650 ± 30 °C, even more preferably 650 ± 20 °C, most preferably 650 ± 10 °C; and - T3 is in the range of 620 ± 50 °C, preferably 620 ± 40 °C, more preferably 620 ± 30 °C, even more preferably 620 ± 20 °C, most preferably 620 ± 10 °C.

[0194] Item 53: The method according to any of the preceding items, wherein p3 < pi.

[0195] Item 54: The method according to any of the preceding items, wherein the magnitude of the relative pressure difference | p3 - pi | is at most 6 bar, preferably at most 5 bar, more preferably at most 4 bar, even more preferably at most 3 bar, most preferably at most 2 bar, and in particular at most 1 bar.

[0196] Item 55: The method according to any of the preceding items, wherein the nickel-based NH3 decomposition catalyst in the at least one catalyst bed of the plurality of tubes of the tubular reactor is a supported nickel.

[0197] Item 56: The method according to any of the preceding items, wherein the nickel-based NH3 decomposition catalyst of the respective at least one catalyst bed of the plurality of tubes of the tubular reactor for NH3 decomposition has an (apparent) activation energy of not more than 240 kJ·mol -1 ; preferably not more than 230 kJ·mol -1 , more preferably not more than 220 kJ·mol -1 , even more preferably not more than 210 kJ·mol -1 , most preferably not more than 200 kJ·mol -1 , and in particular not more than 190 kJ·mol -1 .

[0198] Item 57: The method according to any of the preceding items, wherein the nickel-based NH3 decomposition catalyst of the respective at least one catalyst bed of the plurality of tubes of the tubular reactor for NH3 decomposition has an (apparent) activation energy of not more than 180 kJ·mol -1 ; preferably not more than 170 kJ·mol -1 , more preferably not more than 160 kJ·mol -1 , even more preferably not more than 150 kJ·mol -1 , most preferably not more than 140 kJ·mol -1 , and in particular not more than 130 kJ·mol -1 .

[0199] Item 58: The process according to any of the preceding items, wherein the number of parallel tubes in the tube reactor is at least 50, preferably at least 100, more preferably at least 150, even more preferably at least 200, most preferably at least 250, and in particular at least 300.

[0200] Item 59: The process according to any of the preceding items, wherein the parallel tubes of the tube reactor each have a length L in the flow direction of the intermediate product gas or product gas of at least 5.5 m, preferably at least 6.0 m, more preferably at least 6.5 m, even more preferably at least 8 m, most preferably at least 7.0 m, and in particular at least 7.5 m. R .

[0201] Item 60: The process according to any of the preceding items, wherein the parallel tubes of the tube reactor have a substantially circular cross-section in the flow direction of the intermediate product gas or product gas, which cross-section has an inner diameter of at least 5.0 cm, preferably at least 5.5 cm, more preferably at least 6.0 cm, even more preferably at least 6.5 cm, preferably at least 7.0 cm, and in particular at least 7.5 cm.

[0202] Item 61 : The process according to any of the preceding items, wherein the parallel tubes of the tube reactor have a substantially circular cross-section in the flow direction of the intermediate product gas or product gas, which cross-section has an inner diameter of at most 12 cm, preferably at most 11 cm, more preferably at most 10 cm, even more preferably at most 9.5 cm, most preferably at most 9.0 cm, and in particular at most 8.5 cm.

[0203] Item 62: The process according to any of the preceding items, wherein the catalyst beds of the tube reactor have a space velocity of 500 - 15000 h -1 , preferably 1000 - 10000 h -1 , more preferably 2500 - 7500 h -1 .

[0204] Item 63: The process according to any of the preceding items, wherein at least one catalyst bed of the fixed bed reactor has a space velocity which is generally greater than the space velocity of the catalyst beds of the tube reactor.

[0205] Item 64: The process according to any of the preceding items, wherein T3 is in the range of 560 - 700 °C.

[0206] Item 65: The process according to any of the preceding items, wherein T3 is at least 590 °C, preferably at least 595 °C, more preferably at least 600 °C, even more preferably at least 605 °C, most preferably at least 610 °C, and in particular at least 615 °C.

[0207] Item 66: The method according to any of the preceding items, wherein T3 is at most 650°C, preferably at most 645°C, more preferably at most 640°C, even more preferably at most 635°C, most preferably at most 630°C, and in particular at most 625°C.

[0208] Item 67: The method according to any of the preceding items, wherein p3 is at least 12 bar a, preferably at least 14 bar a, more preferably at least 16 bar a, even more preferably at least 18 bar a, most preferably at least 20 bar a, and in particular at least 22 bar a.

[0209] Item 68: The method according to any of the preceding items, wherein p3 is at most 80 bar a, preferably at most 70 bar a, more preferably at most 60 bar a, even more preferably at most 50 bar a, most preferably at most 40 bar a, and in particular at most 30 bar a.

[0210] Item 69: The method according to any of the preceding items, wherein T4 is in the range of 560-750°C.

[0211] Item 70: The method according to any of the preceding items, wherein T4 is at least 650°C, preferably at least 655°C, more preferably at least 660°C, even more preferably at least 665°C, most preferably at least 670°C, and in particular at least 675°C.

[0212] Item 71 : The method according to any of the preceding items, wherein T4 is at most 710°C, preferably at most 705°C, more preferably at most 700°C, even more preferably at most 695°C, most preferably at most 690°C, and in particular at most 685°C.

[0213] Item 72: The method according to any of the preceding items, wherein p4 is at least 12 bar a, preferably at least 14 bar a, more preferably at least 16 bar a, even more preferably at least 18 bar a, most preferably at least 20 bar a, and in particular at least 22 bar a.

[0214] Item 73: The method according to any of the preceding items, wherein p4 is at most 80 bar a, preferably at most 70 bar a, more preferably at most 60 bar a, even more preferably at most 50 bar a, most preferably at most 40 bar a, and in particular at most 30 bar a.

[0215] Item 74: The method according to any of the preceding items, wherein T4 > T3.

[0216] Item 75: The method according to any of the preceding items, wherein the magnitude of the relative temperature difference |T3-T4| is at least 10°C, more preferably at least 15°C, even more preferably at least 20°C, most preferably at least 25°C, and in particular at least 30°C.

[0217] Item 76: The method according to any of the preceding items, wherein the magnitude of the relative temperature difference |T3-T4| is at least 35°C, more preferably at least 40°C, even more preferably at least 45°C, most preferably at least 50°C, and in particular at least 55°C.

[0218] Item 77: The method according to any of the preceding items, wherein the magnitude of the relative temperature difference |T3-T4| is at most 55°C, more preferably at most 50°C, even more preferably at most 45°C, most preferably at most 40°C, and in particular at most 35°C.

[0219] Item 78: The method according to any of the preceding items, wherein the magnitude of the relative temperature difference |T3-T4| is at most 30°C, more preferably at most 25°C, even more preferably at most 20°C, most preferably at most 15°C, and in particular at most 10°C.

[0220] Item 79: The method according to any of the preceding items, wherein -T3 is in the range of 620 ± 50°C, preferably 620 ± 40°C, more preferably 620 ± 30°C, even more preferably 620 ± 20°C, most preferably 620 ± 10°C; and -T4 is in the range of 650 ± 50°C, preferably 650 ± 40°C, more preferably 650 ± 30°C, even more preferably 650 ± 20°C, most preferably 650 ± 10°C.

[0221] Item 80: The method according to any of the preceding items, wherein p4 > p3.

[0222] Item 81 : The method according to any of the preceding items, wherein the magnitude of the relative pressure difference |p3-p4| is at most 6 bar, preferably at most 5 bar, more preferably at most 4 bar, even more preferably at most 3 bar, most preferably at most 2 bar, and in particular at most 1 bar.

[0223] Item 82: The method according to any of the preceding items, wherein the conversion of NH3 decomposed in step (h) is at least 90%, preferably at least 92.5%, more preferably at least 95%, even more preferably at least 96%, most preferably at least 97%, and in particular at least 98%, based on the amount of NH3 originally present in the reactant gas provided in step (a).

[0224] Item 83: The method according to any of the preceding items, wherein the combustion gas is combusted with at least one burner, resulting in at least one flame through which heat energy is introduced into the tube, wherein the heat energy flow Q introduced into the tubew has a non-constant progression over the length L R of the tube.

[0225] Item 84: The method according to item 83, wherein the heat energy flow Q w has a maximum over the length L R of the tube.

[0226] Item 85: The method according to item 84, wherein the tube can conceptually be divided into two equal halves over its length L R , wherein the intermediate product gas or product gas first flows through the first half and then through the second half, wherein the heat energy flow Q w reaches a maximum in the first half.

[0227] Item 86: The method according to item 83 or 84, wherein the tube can conceptually be divided into four equal segments over its length L R , wherein the intermediate product gas or product gas first flows through the first segment, then through the second segment, and finally through the third segment, followed by the fourth segment, wherein the heat energy flow Q w reaches a maximum in the second segment.

[0228] Item 87: The method according to any of the preceding items, wherein the combustion gas is combusted with at least one burner to produce at least one flame, the length L F of which extends essentially parallel to the length L R of the tube in the flow direction of the combusted combustion gas.

[0229] Item 88: The method according to any of the preceding items, wherein the combusted combustion gas flows essentially in the same direction as the intermediate product gas or product gas (roof combustion).

[0230] Item 89: The method according to item 87 or 88, wherein L R > L F .

[0231] Item 90: The method according to any of items 87 to 89, wherein the length ratio L R : L F is in the range of 10:1 to 1.1 :1, preferably 7:1 to 1.5:1, more preferably 4:1 to 2:1.

[0232] Item 91 : The method according to any of the preceding items, wherein the amount of heat consumed by the endothermic decomposition of NH3 is initially greater than the heat energy flow Q wThe amount of heat introduced into the tube by the combustion of the combustion gas such that the intermediate product gas or product gas is initially cooled to a minimum gas temperature T min (T min (T3), during flow through the tube.

[0233] Item 92: The method according to item 91, wherein the magnitude of the relative temperature difference │T3 - T min │ is at least 10 °C, more preferably at least 20 °C, even more preferably at least 30 °C, most preferably at least 30 °C, and particularly at least 40 °C.

[0234] Item 93: The method according to item 91 or 92, wherein T min is in the range of 560 to 600 °C, preferably 570 to 590 °C.

[0235] Item 94: The method according to any one of items 91 to 93, wherein upon reaching the minimum gas temperature T min the amount of heat consumed by the endothermic decomposition of NH3 is subsequently less than the amount of heat introduced into the tube by the combustion of the combustion gas as the heat energy flow Q w such that the intermediate product gas or product gas is subsequently heated (T min (T4) upon flow through the tube.

[0236] Item 95: The method according to item 94, wherein the magnitude of the relative temperature difference │T4 - T min │ is at least 50 °C, more preferably at least 55 °C, even more preferably at least 60 °C, most preferably at least 65 °C, and particularly at least 70 °C.

[0237] Item 96: The method according to any one of items 91 to 95, wherein the tube can conceptually be divided into two equal halves along the length L R of the tube, wherein the intermediate product gas or product gas first flows through the first half and then through the second half, reaching the minimum gas temperature T m .

[0238] Item 97: The method according to any one of items 91 to 96, wherein the tube can conceptually be divided into four equal segments along the length L R of the tube, wherein the intermediate product gas or product gas first flows through the first segment, then through the second segment, finally through the third segment and subsequently through the fourth segment, reaching the minimum gas temperature T m .

[0239] Item 98: The method according to any of the preceding items, wherein - T1 is in the range of 650 ± 50 °C, preferably 650 ± 40 °C, more preferably 650 ± 30 °C, even more preferably 650 ± 20 °C, most preferably 650 ± 10 °C; - T2 is in the range of 450 ± 50 °C, preferably 450 ± 40 °C, more preferably 450 ± 30 °C, even more preferably 450 ± 20 °C, most preferably 450 ± 10 °C; - T3 is in the range of 620 ± 50 °C, preferably 620 ± 40 °C, more preferably 620 ± 30 °C, even more preferably 620 ± 20 °C, most preferably 620 ± 10 °C; and - T4 is in the range of 650 ± 50 °C, preferably 650 ± 40 °C, more preferably 650 ± 30 °C, even more preferably 650 ± 20 °C, most preferably 650 ± 10 °C.

[0240] Item 99: The method according to any of items 1 to 97, wherein - T1 is in the range of 650 ± 50 °C, preferably 650 ± 40 °C, more preferably 650 ± 30 °C, even more preferably 650 ± 20 °C, most preferably 650 ± 10 °C; - T2 is in the range of 350 ± 50 °C, preferably 350 ± 40 °C, more preferably 350 ± 30 °C, even more preferably 350 ± 20 °C, most preferably 350 ± 10 °C; - T3 is in the range of 620 ± 50 °C, preferably 620 ± 40 °C, more preferably 620 ± 30 °C, even more preferably 620 ± 20 °C, most preferably 620 ± 10 °C; and - T4 is in the range of 650 ± 50 °C, preferably 650 ± 40 °C, more preferably 650 ± 30 °C, even more preferably 650 ± 20 °C, most preferably 650 ± 10 °C.

[0241] Item 100: The method according to any of the preceding items, wherein the combustion gas comprises NH3; preferably wherein the reactant gas provided in step (a) is split into (i) a first portion that is fed to step (b), and (ii) a second portion that is used as the combustion gas.

[0242] Item 101 : The method according to item 96, wherein the second portion is no more than 8.0 mol%, more preferably no more than 7.5 mol%, even more preferably no more than 7.0 mol%, most preferably no more than 6.5 mol%, and in particular no more than 5 mol% of the reactant gas provided in step (a).

[0243] Item 102: The method according to any of the preceding items, comprising an additional step (j) of cleaning the product gas by pressure swing adsorption to obtain a H2-enriched product gas and a H2-depleted tail gas; preferably wherein the H2-depleted tail gas is recycled and introduced into the combustion gas.

[0244] Item 103: An apparatus for carrying out the method according to any of the preceding items.

[0245] A preferred embodiment of the method of the present invention is as follows: Figures 1 to 3 illustrate. Attached Figure Description

[0246] Figure 1 A schematic diagram of a preferred embodiment is shown, wherein the intermediate product gas 2 is introduced from top to bottom into a tubular reactor 1. The tubular reactor 1 contains a nickel-based NH3 decomposition catalyst 3. The combustion gas 4 is introduced into combustion chambers 5a and 5b and combusted therein, generating flames 6a and 6b in the direction of the combustion gas flow. The tubular reactor 1 has a length L. R Flames 6a and 6b each have a length L F The heat generated during the combustion of combustion gas 4 heats tubular reactor 1. The product gas 7 obtained through catalytic decomposition is discharged from tubular reactor 1. The combustion exhaust gas 8 obtained from the combustion of combustion gas 7 is discharged from combustion chambers 5a and 5b.

[0247] Figure 2 The diagram illustrates the temperature changes of the intermediate product gas during the chemical reaction of an intermediate product gas over a nickel-based NH3 decomposition catalyst to produce the product gas. Two reaction mechanisms, A (dashed line) and B (solid line), are distinguished, differing in their initial gas temperature T3 upon introduction into the reactor, i.e., when they first come into contact with the NH3 decomposition catalyst. In reaction mechanism A, the gas temperature T... 3A The temperature is relatively high. Since the decomposition of NH3 is endothermic, the reaction is accelerated and proceeds rapidly at relatively high temperatures. This causes the gas temperature to initially decrease significantly due to the amount of heat consumed, and then rise again downstream due to the heating of the reactor. Ultimately, the product gas is produced at its maximum decomposition yield at a gas temperature T. 4A The gas exits the reactor. The gas temperature passes through a minimum along the distance within the reactor, which also means the decomposition reaction rate passes through a minimum. In this reaction mechanism, the decomposition reaction rate is initially very fast (to the left of the minimum), but also relatively slow due to the significant drop in associated temperature (to the right of the minimum). Under such a reaction mechanism, a relatively large amount of nickel-based NH3 decomposition catalyst is required to achieve a high yield. In reaction mechanism B, the gas temperature T... 3B The temperature is relatively low. In this case, although the decomposition reaction rate is not initially very fast, the gas temperature does not drop as much either. In this reaction mechanism, the downstream gas temperature can rise again to a higher gas temperature earlier due to the heating of the reactor.

[0248] Figure 3 The length L of the tubular reactor is shown. Rthe change in gas temperature of the intermediate product gas in the chemical reaction of the intermediate product gas on the nickel-based NH3 decomposition catalyst to produce the product gas. In reaction mechanism A, the length L of the tube reactor is relatively short, and the product gas exits the tube reactor at a relatively low gas temperature T RA and a relatively low conversion of decomposed NH3. In reaction mechanism B, the length L of the tube reactor is relatively long, and the product gas exits the tube reactor at a relatively high gas temperature T 4A and a relatively high conversion of decomposed NH3. RB 4B

[0249] List of reference signs: 1 tube reactor 2 intermediate product gas 3 nickel-based NH3 decomposition catalyst 4 combustion gas 5a / 5b combustion chamber 6a / 6b flame 7 product gas 8 combustion exhaust gas​​

Claims

1. A method for preparing H2 from NH3, comprising the following steps: (a) Provide reactant gases that contain NH3 or are substantially composed of NH3; (b) The reactant gas is heated to a gas temperature T1 in the range of 550-850°C at a pressure p1 of at least 10 bar a; (c) Introducing a heated reactant gas at a temperature of T1 and a pressure of p1 into at least one fixed-bed reactor, the fixed-bed reactor comprising at least one catalyst bed, the catalyst bed comprising or consisting substantially of an NH3 decomposition catalyst. (d) Partially decompose NH3 on at least one catalyst bed in at least one fixed-bed reactor to obtain an intermediate product gas consisting of H2, N2 and undecomposed NH3 or substantially consisting of H2, N2 and undecomposed NH3; (e) The intermediate product gas is discharged from at least one fixed-bed reactor at a gas temperature T2 in the range of 300-700°C and a pressure p2 of at least 10 bar a. (f) Heating the intermediate product gas to a gas temperature T3 in the range of 550-700°C at a pressure p3 of at least 10 bar a; (g) Introducing the heated intermediate product gas at a gas temperature of T3 and a pressure of p3 into at least one tubular reactor, the tubular reactor comprising a plurality of parallel tubes, each parallel tube comprising at least one catalyst bed, the catalyst bed being heated by combustion of the combustion gas and comprising or substantially consisting of a nickel-based NH3 decomposition catalyst. (h) Decompose NH3 on a catalyst bed in at least one tubular reactor to obtain a product gas consisting of H2, N2 and optional undecomposed NH3 or substantially consisting of H2, N2 and optional undecomposed NH3. as well as (i) Product gas is discharged from at least one tubular reactor at a gas temperature T4 in the range of 550-750°C and a pressure p4 of at least 10 bar a.

2. The method according to claim 1, wherein T4 > T3.

3. The method according to any one of the preceding claims, wherein at least one fixed-bed reactor is operated in adiabatic conditions.

4. The method according to any one of the preceding claims, wherein the NH3 decomposition catalyst of at least one catalyst bed in the fixed-bed reactor is nickel-based, preferably nickel-supported.

5. The method according to any one of the preceding claims, wherein -T1 is in the range of 650±50℃, preferably 650±40℃, more preferably 650±30℃, even more preferably 650±20℃, and most preferably 650±10℃; and -T2 is in the range of 450±50℃, preferably 450±40℃, more preferably 450±30℃, even more preferably 450±20℃, and most preferably 450±10℃.

6. The method according to any one of claims 1-4, wherein -T1 is in the range of 650±50℃, preferably 650±40℃, more preferably 650±30℃, even more preferably 650±20℃, and most preferably 650±10℃; and -T2 is in the range of 350±50℃, preferably 350±40℃, more preferably 350±30℃, even more preferably 350±20℃, and most preferably 350±10℃.

7. The method according to any one of the preceding claims, wherein the conversion rate of NH3 decomposed in step (d) is at least 12.5%, preferably at least 15%, more preferably at least 17.5%, even more preferably at least 20%, most preferably at least 22.5%, and particularly at least 25%, all based on the amount of NH3 initially present in the reactant gas provided in step (a).

8. The method according to any one of the preceding claims, wherein each of the plurality of parallel tubes of the tubular reactor has a length L of at least 5.5 m in the direction of flow of the intermediate product gas or the product gas. R Preferably at least 6.0m, more preferably at least 6.5m, even more preferably at least 8m, most preferably at least 7.0m, and particularly at least 7.5m.

9. The method according to any one of the preceding claims, wherein -T3 is in the range of 620±50℃, preferably 620±40℃, more preferably 620±30℃, even more preferably 620±20℃, and most preferably 620±10℃; and -T4 is in the range of 650±50℃, preferably 650±40℃, more preferably 650±30℃, even more preferably 650±20℃, and most preferably 650±10℃.

10. The method according to any one of the preceding claims, wherein the conversion rate of the NH3 decomposed in step (h) is at least 90%, preferably at least 92.5%, more preferably at least 95%, even more preferably at least 96%, most preferably at least 97%, and particularly at least 98%, all based on the amount of NH3 initially present in the reactant gas provided in step (a).

11. The method according to any one of the preceding claims, wherein the combustion gas is burned by at least one burner to produce at least one flame, the flame having a length L F The flow direction of the combustion gases is basically parallel to the length L of the pipe. R extend.

12. The method of claim 11, wherein the length ratio L R :L F Within the range of 10:1 to 1.1:1, preferably 7:1 to 1.5:1, and more preferably 4:1 to 2:

1.

13. The method according to any one of the preceding claims, wherein, When the intermediate product gas or product gas flows through the tube in step (h), the amount of heat consumed by the endothermic decomposition of NH3 is initially greater than the heat energy flow Q from the combustion of the combustion gas. w The amount of heat introduced into the tube is such that the intermediate product gas or product gas is initially cooled to a minimum gas temperature T during its flow through the tube. min (T min <T3)。 14. The method according to claim 13, wherein, When the minimum gas temperature T is reached min Subsequently, the amount of heat consumed by the endothermic decomposition of NH3 is less than the heat energy flow Q obtained through the combustion of the combustion gases. w The amount of heat introduced into the tube so that the intermediate product gas or product gas is subsequently heated during its flow through the tube (T min <T4)。 15. The method according to claim 13 or 14, wherein the tubes may conceptually each extend along their length L. R The mixture is divided into two equal halves. The intermediate product gas or product gas flows through the first half first, and then through the second half. The minimum gas temperature T is reached when the mixture flows through the first half. m .

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