Process for producing hydrogen with a ruthenium-containing supported catalyst

Abstract

The present invention relates to a process for producing hydrogen from an ammonia-containing gas with a supported catalyst in the form of a ruthenium-endowed support body, and to the use of such a ruthenium-containing supported catalyst in a process for producing hydrogen. The process comprises the providing of a supported catalyst in the form of a ruthenium-endowed support body, wherein the support body comprises a refractory oxide as support material, is cylindrical and has at least three mutually spaced-apart channels that extend fully through the support body, where one of the channels extends along a central longitudinal axis.

Description

[0001] Process for producing hydrogen using a ruthenium-containing catalyst

[0002] The present invention relates to a process for producing hydrogen from an ammonia-containing gas using a supported catalyst in the form of a ruthenium-containing support body, as well as the use of such a ruthenium-containing supported catalyst in a process for producing hydrogen.

[0003] The generation of energy from "green" sources has gained increasing importance in recent years. In particular, the production and use of hydrogen as a clean energy source to replace fossil fuels is the subject of intensive research.

[0004] Hydrogen can be obtained, for example, by the decomposition of ammonia:

[0005] 2 NH3 -> 3 H2 + N2

[0006] This reaction does not produce any environmentally harmful byproducts, unlike production methods based on fossil fuels.

[0007] Thanks to advantages such as high energy density, simple and established production and transport, and long-term storage capacity, ammonia is considered a promising hydrogen carrier. Precious metal catalysts (usually ruthenium and / or platinum-based) or non-precious metal catalysts (usually iron and / or nickel-based) can be used for the catalytic decomposition of ammonia to produce hydrogen.

[0008] Since ammonia decomposition is an endothermic reaction, it is favored at high temperatures. With today's commercially available catalysts, typically nickel-based, temperatures of 700–900 °C may be required. From a process engineering perspective, it is advantageous to keep the temperature as low as possible to reduce the energy required for heat generation and minimize the thermal load on the reactor systems.

[0009] The suitability of ruthenium as a catalytically active component for this reaction has long been known; for example, Amano and Taylor described the suitability of ruthenium supported on Al2O3 for this reaction as early as 1954 (J. Am. Chem. Soc. 1954, 76, 16, 4201-4204). However, the catalytic performance depends on the support material and the shape of the catalyst, as well as the preparation process, particularly the ruthenium precursor compound used. Known catalysts have a relatively high metal loading and require a high process temperature. Since ruthenium is an expensive noble metal, a high metal loading is undesirable.

[0010] Typically, ruthenium chloride is used as the ruthenium precursor compound to produce ruthenium-containing supported catalysts. JP H1085601 A describes in this context that catalysts prepared in this way must be thoroughly washed to reduce the halogen content to a level compatible with the reactor system.

[0011] The use of catalysts in the form of ruthenium-coated support bodies is also known, for example, from WO 2019188219 A1. However, particularly suitable support bodies are not disclosed. As recognized in the present invention, however, the geometry of the support bodies used has a significant influence on the efficiency of the process.

[0012] A technical problem to be solved by the present invention is to provide a process for producing hydrogen from an ammonia-containing gas which can be carried out at low operating temperatures in the range of 450°C to 650°C.

[0013] In addition, the task was to provide a supported catalyst that is particularly suitable for such a process, which causes the lowest possible pressure loss and is therefore suitable for use in large-scale processes.

[0014] Another objective was to provide a supported catalyst with increased stability under the process conditions. Stability in this context refers to both the thermal and chemical stability of the catalytically active component, as well as the physical and thermomechanical stability of the support and the entire supported catalyst. In particular, the supported catalyst should exhibit high mechanical stability and low abrasion behavior.

[0015] The objects are at least partially achieved by a process for producing hydrogen from an ammonia-containing gas, comprising the following steps: i) providing a supported catalyst in the form of a ruthenium-equipped support body, wherein the support body comprises a refractory oxide as support material, is cylindrical and has at least three spaced-apart channels which extend completely through the support body, wherein one of the channels extends along a central longitudinal axis, ii) contacting the supported catalyst with the ammonia-containing gas.

[0016] In the context of the present invention, it was surprisingly found that the use of a ruthenium-containing supported catalyst provided in the form of a support body with a specific geometry completely or partially solves at least some of the problems identified in the prior art.

[0017] It is assumed that the geometry of the support body has a beneficial influence on ammonia decomposition. Ammonia decomposition is a volume-increasing reaction (the number of particles doubles: 2 ammonia molecules are converted into a total of 4 molecules – 3 hydrogen, 1 nitrogen). It is conceivable that the beneficial effect of the supported catalyst used according to the invention could be due to an increase in the available geometric cavity of the catalyst body.

[0018] In particular, the supported catalyst used according to the invention is particularly suitable because it causes advantageous radial mass transport in the process and a low pressure loss in the reactor.

[0019] Furthermore, a supported catalyst for ammonia decomposition according to the present invention has advantageous abrasion behavior and increased mechanical stability.

[0020] In addition, the process according to the invention has a good ammonia conversion rate and thus has improved performance in hydrogen production.

[0021] The process according to the invention relates to the production of hydrogen from an ammonia-containing gas.

[0022] An ammonia-containing gas is understood to be a gas or gas mixture that contains 50 to 100 vol.% ammonia. The ammonia-containing gas can contain other components that do not influence the decomposition reaction, for example inert gases such as nitrogen, helium or argon. The ammonia-containing gas can, for example, consist of 50 to 100 vol.% ammonia, 0 to 50 vol.% helium, 0 to 50 vol.% argon, 0 to 5 vol.% water, 0 to 20 vol.% oxygen, 0 to 50 vol.% nitrogen, 0 to 50 vol.% hydrogen and 0 to 5 vol.% impurities other than ammonia, helium, argon, water, oxygen, nitrogen and hydrogen, where the sum of the vol.% is 100 vol.%.

[0023] Advantageously, the ammonia-containing gas contains at least 70 vol.% ammonia, in particular at least 80 vol.%, particularly preferably at least 90 vol.%.

[0024] Advantageously, the ammonia-containing gas contains no more than 3 vol.% water, in particular no more than 2 vol.%, particularly preferably no more than 0.2 vol.%. Particularly preferably, the ammonia-containing gas can also be anhydrous.

[0025] Advantageously, the ammonia-containing gas contains no more than 15 vol% oxygen, in particular no more than 10 vol%, particularly preferably no more than 5 vol%. In particular, the ammonia-containing gas can also be oxygen-free.

[0026] The ammonia-containing gas may already contain nitrogen; preferably, the nitrogen content is not more than 40 vol.%, in particular not more than 20 vol.%, particularly preferably not more than 10 vol.%, and most preferably not more than 5 vol. The presence of nitrogen can be particularly advantageous during the start-up phase of the process. The ammonia-containing gas may also be nitrogen-free.

[0027] The ammonia-containing gas may already contain hydrogen; preferably, the hydrogen content is not more than 40 vol.%, in particular not more than 30 vol.%, and particularly preferably not more than 10 vol.%. The ammonia-containing gas may also be hydrogen-free.

[0028] Furthermore, the ammonia-containing gas may, as mentioned above, contain impurities, for example CO, CO2, hydrocarbons, heavy metals, halogens, phosphorus-containing compounds, and / or sulfur-containing compounds. The proportion of such impurities is preferably less than 3 vol.%, in particular less than 1 vol.%. It has proven particularly advantageous if the proportion of sulfur-containing compounds is less than 100 ppm, in particular less than 10 ppm, especially if the ammonia-containing gas is free of sulfur-containing compounds. The composition of the ammonia-containing gas can be varied during the process; for example, it may be advantageous to initially use an ammonia-containing gas with a nitrogen content of more than 3 vol.% and subsequently reduce the nitrogen content.

[0029] In the process according to the invention, a supported catalyst is provided. The process is therefore carried out in the presence of a supported catalyst. A "catalyst" is understood to be a catalytically active material for a corresponding application. Supported catalysts are generally understood to be catalysts that contain a support material whose surface is provided with a catalytically active component. The support material should provide a stable platform for the catalytically active material and be stable under the selected reaction conditions. Typically, the support material itself exhibits no catalytic activity.

[0030] The supported catalyst is a ruthenium-coated support body. In other words, the supported catalyst is provided in the form of a ruthenium-coated catalyst body. The terms "ruthenium-coated support body" and "ruthenium-containing supported catalyst" are used synonymously in this application. Such supported catalysts are also referred to as bulk catalysts. Bulk catalysts are provided in reactors for heterogeneously catalyzed reactions as a loose bed. The bed must be designed such that, on the one hand, a large surface area is provided as the contact area between the solid catalyst and the fluid reactants, but, on the other hand, the pressure drop across the reactor is not excessive.Bulk catalysts have the advantage over powder catalysts that they can be used in continuous processes, for example in fixed-bed reactors.

[0031] The carrier body is cylindrical. The geometry of the carrier body can thus be described by its length along a central axis and its outer diameter. This central axis is also referred to as the longitudinal axis in this application.

[0032] In preferred embodiments, the carrier body has a length and / or a

[0033] Outer diameter in the range of 0.5 to 50 mm, preferably 1 to 30 mm, in particular 2 to 20 mm. It has proven advantageous if the ratio of length to outer diameter is between 1.1 and 1.5, in particular between 1.1 and 1.3.

[0034] For the purposes of this application, a cylindrical carrier body is understood to mean both carrier bodies that have a flat peripheral surface and those that have notches or grooves extending along the peripheral surface. The notches or grooves can be arranged at any angle relative to the direction of the longitudinal axis of the carrier body. For example, the notches or grooves can run helically along the peripheral surface of the carrier body. However, the notches or grooves preferably run parallel to the longitudinal axis of the carrier body.

[0035] The support body has at least three spaced-apart channels that extend completely through the support body. In other words, the channels extend from a top side to a bottom side of the support body. The top and bottom sides of the support body are also referred to as end faces. Channels are understood to be tubular cavities that are particularly gas-permeable, i.e., allow the flow of gases. Such channels have proven particularly advantageous because, on the one hand, they counteract the pressure loss in the catalyst bed and, on the other hand, they increase the available catalytically active surface area.

[0036] The carrier body can, for example, have 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, or 15 channels. It has proven advantageous for the carrier body to have between 3 and 10 channels, in particular between 5 and 8 channels.

[0037] One of the channels extends along the central longitudinal axis of the carrier body. In other words, the central longitudinal axis lies in the middle of said channel.

[0038] Preferably, all channels extend parallel to the central longitudinal axis.

[0039] Preferably, the channels that do not extend along the central longitudinal axis of the support body are evenly spaced and arranged symmetrically about the central longitudinal axis of the support body in order to maximize the resulting strength of the catalyst.

[0040] The shape of the channels is not further restricted; they can, for example, have a round, oval, teardrop-shaped, or polygonal cross-section. The cross-sectional area of ​​the channels is preferably in the range of 0.3 mm 2 up to 15 mm 2 , especially in a range of 1.0 mm 2 up to 10 mm 2The at least three channels can all have the same cross-sectional area. It may be advantageous if the one channel extending along the central longitudinal axis of the support body has a larger cross-sectional area than the at least two other channels.

[0041] Advantageously, the proportion of the channel cross-sectional areas in the total cross-sectional area of ​​the carrier body is at least 10%, in particular at least 15%, particularly advantageously at least 20%.

[0042] If the channels have a round cross-sectional area, the diameter of the channels is preferably in a range from 0.1 mm to 4 mm, preferably in the range from 0.5 mm to 3 mm, in particular in the range from 1.0 mm to 2 mm. The at least three channels can all have the same diameter. It can be advantageous if the one channel extending along the central longitudinal axis of the carrier body has a larger diameter than the at least two other channels.

[0043] Advantageously, the volume fraction of the channels in the total volume enclosed by the support body is at least 20%, in particular at least 25%, and particularly advantageously at least 30%. A high volume fraction of the channels has a beneficial effect on the volume expansion of the reaction gases during ammonia decomposition. Furthermore, the proportion of the geometric surface area of ​​the support bodies is increased, which in turn can have a positive effect on the available catalyst surface area.

[0044] The support body can have flat or curved end faces. In advantageous embodiments, the support body has at least one curved end face; particularly advantageously, both end faces are curved. It has been shown that such curved end faces increase the geometric surface area of ​​the support body and have a positive effect on the pressure drop in the reactor.

[0045] To achieve the longest possible service life of the carrier bodies, they must have sufficiently high strength. This can be achieved both through the geometry of the carrier body and through the strength of the material from which the carrier body is made. Advantageously, the carrier body has a lateral fracture hardness of more than 30 N, preferably more than 50 N. The lateral fracture hardness can be determined according to the method described below.

[0046] Advantageously, the carrier body has an abrasion resistance of less than 30%, more preferably less than 20%. The abrasion resistance can be determined using the method described below.

[0047] The thermal expansion coefficient of the carrier body is advantageously less than 10*10 -6 K' 1 , especially less than 8*10 -6 K' 1 .

[0048] The supported catalyst contains ruthenium, meaning that the support material of the support body contains at least ruthenium. The ruthenium thus forms at least part of the catalytically active component of the supported catalyst.

[0049] The term "ruthenium" used here does not imply any statement about the oxidation state of the ruthenium. In other words, it does not refer to the presence of the elemental state with oxidation state 0. The ruthenium can be present on and / or at the support material in elemental form, i.e., in oxidation state (0) and / or in a higher oxidation state. The term "oxidation state" used herein, which is familiar to those skilled in the art, refers to the formal charge of an atom within a compound or the actual charge of monatomic ions. Atoms in the elemental state, by definition, have oxidation state 0.

[0050] The term "equipment of the carrier material with ruthenium" means that the ruthenium is supported on the carrier material of the carrier body, i.e., that the ruthenium is present on, in, and / or on the carrier material, for example, in the form of particles and / or a layer. The terms "equipped" and "supported" are used synonymously and interchangeably within the scope of this application. The equipment of the carrier material can be present both on the surface and inside the carrier material. The term "surface" encompasses both the outer and inner surfaces; in other words, it also includes the internal surface formed by pores.

[0051] Typically, the support body is provided with 0.01 wt% to 20 wt% ruthenium, based on the total amount of the supported catalyst, preferably with 0.1 wt% to 15 wt%, more preferably with 0.5 wt% to 10 wt%, particularly preferably with 1.0 wt% to 5 wt%.

[0052] For the purposes of this application, the area boundaries are deemed to be included if areas are mentioned.

[0053] The supported catalyst preferably contains no more than 20 wt.% ruthenium, particularly preferably no more than 15 wt.%, in particular no more than 10 wt.%.

[0054] For example, the supported catalyst contains 20 wt% ruthenium, 15 wt% ruthenium, 12 wt% ruthenium, 10 wt% ruthenium, 9 wt% ruthenium, 8 wt% ruthenium, 7 wt% ruthenium, 6 wt% ruthenium, 5 wt% ruthenium, 4 wt% ruthenium, 3 wt% ruthenium, 2 wt% ruthenium, 1 wt% ruthenium, 0.5 wt% ruthenium, 0.1 wt% ruthenium, 0.05 wt% ruthenium, 0.01 wt% ruthenium or intermediates thereof.

[0055] The support material of the supported catalyst contains at least ruthenium as the catalytically active component. However, the support material can also contain other components, for example, at least one other noble metal or promoters such as a transition metal, an alkali metal, or an alkaline earth metal.

[0056] In the following, the catalytically active component of the supported catalyst is referred to as a noble metal species, regardless of whether it comprises only ruthenium or ruthenium and at least one other noble metal. The terms "noble metal" or "noble metal species" used here do not imply any statement about the oxidation state of the noble metal. In other words, they do not necessarily refer to the presence of the elemental state with oxidation state 0. The noble metal species can be present in and / or on the supported catalyst in elemental form, i.e., in oxidation state (0) and / or in a higher oxidation state.

[0057] In one embodiment, the supported catalyst comprises only one further noble metal as a catalytically active component. In further embodiments, the supported catalyst comprises two or more further noble metals. The at least one further noble metal with which the supported catalyst is provided is preferably selected from Group 8, Group 9, Group 10, or Group 11 of the Periodic Table. Particularly preferably, the at least one further noble metal is selected from the group consisting of rhodium (Rh), palladium (Pd), silver (Ag), platinum (Pt), gold (Au), iridium (Ir), and combinations thereof. Platinum (Pt), palladium (Pd), rhodium (Rh), and iridium (Ir), or combinations thereof, are particularly preferred; even more preferred are platinum (Pt), iridium (Ir), and combinations thereof.

[0058] In particular, it has proven advantageous if the support material is provided with a combination of ruthenium and platinum, ruthenium and palladium, ruthenium, platinum and iridium, ruthenium, palladium and iridium, or ruthenium, palladium and platinum. In particularly preferred embodiments, the support material is provided with ruthenium and iridium or ruthenium, platinum, and iridium.

[0059] If the support material is provided with at least one further noble metal, ruthenium and the at least one further noble metal are preferably present in a molar ratio in the range from 1:20 to 20:1, in particular in a ratio of 1:10 to 10:1.

[0060] The supported catalyst can contain the noble metal species in the range of 0.01–20 wt.%, based on the total weight of the supported catalyst. This refers to the proportion of all noble metal species present, i.e., the sum of all weight percentages of ruthenium and the optionally present other noble metals. In preferred embodiments, the weight fraction of the noble metal species is 0.05–15 wt.%, particularly preferably 0.1–12 wt.%, and most preferably 0.1–10 wt.%.

[0061] The supported catalyst can have a CO surface area in the range of 0.1 to 200 m 2 / g. The CO surface area is a measure of the surface area of ​​the precious metal species. The CO surface area can be determined using the CO adsorption method described later. The supported catalyst can have a CO surface area in the range of 1 to 150 m 2 / g, more preferably in the range of 5 to 100 m 2 / g. It may be preferred that the CO surface area of ​​the supported catalyst is at least 0.1 m 2 / g, preferably at least 1 m 2 / g, more preferably at least 5 m 2 / g. The precious metal species can be present in particulate form, meaning that the particles can be present on and / or in the carrier material. "Presence in the carrier material" here means that the precious metal species can be present in pores of the carrier material.

[0062] In principle, it is advantageous if the particles of the noble metal species are as small as possible, since the particles then have a high degree of dispersion. The degree of dispersion is understood to be the ratio of the number of noble metal atoms that form the surface of the noble metal particles to the total number of noble metal atoms in the noble metal particles. According to a preferred embodiment, the average particle size of the noble metal species is in the range from 0.1 to 15 nm, more preferably in the range from 1 to 10 nm, and particularly preferably in the range from 2 to 8 nm. It may be preferred for the particles of the noble metal species to have an average size of less than 15 nm, more preferably less than 10 nm. The average particle size of the noble metal species can be determined by means of transmission electron microscopy (TEM), as described later.

[0063] Preferably, the particles of the noble metal species are uniformly distributed on and / or within the support material; i.e., the distance between the particles is similar. Preferably, the average distance between the particles of the noble metal species on the support material, determined by TEM, is at least 50% of the average particle size, more preferably at least 75%.

[0064] The supported catalyst can also be provided with a further non-noble metal component, advantageously with an alkali metal or alkaline earth metal component, for example sodium, potassium, rubidium, cesium, magnesium, calcium, strontium, barium, or mixtures thereof. The terms "alkali metal" or "alkali earth metal" used here do not imply any statement about the oxidation state of the non-noble metal component. In other words, they do not refer to the presence of the elemental state with oxidation state 0. The non-noble metal component can be present in and / or on the supported catalyst in elemental form, i.e., in oxidation state (0) and / or in a higher oxidation state. The proportion of this further non-noble metal component in the supported catalyst is advantageously 1 wt.% to 25 wt.% based on the total weight of the supported catalyst, in particular 5 wt.% to 20 wt.%, very particularly 10 wt.% to 15 wt.%.

[0065] If the support material is provided with a non-noble metal component, ruthenium and the non-noble metal component are preferably present in a molar ratio in the range of 1:1 to 1:15, in particular in a ratio of 1:1 to 1:10, particularly preferably in a ratio of 1:2 to 1:5.

[0066] Particularly advantageously, the supported catalyst is provided with at least one alkali metal component or alkaline earth metal component, for example with 1 wt.% to 25 wt.%, based on the total weight of the supported catalyst, preferably with 2 wt.% to 20 wt.%, more preferably with 3 wt.% to 15 wt.%. If the support material is provided with an alkali metal component or alkaline earth metal component, ruthenium and the alkali metal component or alkaline earth metal component are preferably present in a molar ratio in the range of 1:1 to 1:15, in particular in a ratio of 1:1 to 1:10, particularly preferably in a ratio of 1:2 to 1:5. The provision of an alkali metal component or alkaline earth metal component has proven particularly advantageous for the activity of the supported catalyst.

[0067] In particular, the addition of barium has proven particularly advantageous for the activity of the supported catalyst. Advantageously, the support material is provided with 1 wt.% to 25 wt.% barium, based on the total weight of the supported catalyst, preferably with 2 wt.% to 20 wt.%, more preferably with 3 wt.% to 15 wt.%. It has proven particularly advantageous if the supported catalyst is provided with barium and the molar ratio of ruthenium to barium is in the range of 1:1 to 1:15, in particular in a ratio of 1:1 to 1:10, particularly preferably in a ratio of 1:2 to 1:5.

[0068] The supported catalyst preferably has a halogen content of less than 1000 ppm by weight, in particular less than 500 ppm by weight, and particularly preferably less than 100 ppm by weight. A low halogen content has a beneficial effect on the corrosion resistance of the supported catalyst itself and on the reactor system in which the supported catalyst is used. A catalyst with a minimal halogen content has proven particularly advantageous when converting ammonia-containing gases, as it prevents the formation of ammonia- and / or ammonium-containing halide salts, which in turn are harmful to the reactor system.

[0069] The supported catalyst can have a BET surface area in the range of 1 to 1500 m 2 / g, preferably in the range of 10 to 1000 m 2 / g, particularly preferably in the range of 50 to 500 m 2 / g. The BET surface area is also called the specific surface area and can be determined according to ISO 9277:2010 using nitrogen as the adsorbate. In a preferred embodiment, the supported catalyst has a BET surface area of ​​less than 1500 m 2 / g, preferably less than 1000 m 2 / g, particularly preferably less than 500 m 2 / G.

[0070] The supported catalyst can be porous, i.e., the supported catalyst can have micropores and / or mesopores and / or macropores. For the purposes of the present invention, micropores are understood to mean pores with a pore size in the range of less than 2 nm, mesopores are understood to mean pores with a pore size in the range of 2 to 50 nm, and macropores are understood to mean pores with a pore size in the range of 50 nm to 5 pm. Pore size is understood to mean the average size of the pores. Accordingly, pore volume is understood to mean the sum of the volumes of such pores. The pore size distribution and the pore volume can be determined using mercury porosimetry according to ISO 15901-1:2016.

[0071] It may be preferred that the supported catalyst exhibits hierarchical porosity, i.e., that the supported catalyst has pores in various size ranges. The supported catalyst preferably has macropores and mesopores.

[0072] The supported catalyst preferably has macropores with a diameter greater than 100 nm, more preferably greater than 300 nm, even more preferably greater than 500 nm. Preferably, the diameters of the macropores of the supported catalyst are homogeneous, ie at least 75%, more preferably at least 85% of the macropores have a diameter which is in the range of 40% of the mean diameter.

[0073] The supported catalyst preferably has mesopores with a diameter greater than 5 nm, more preferably greater than 15 nm, even more preferably greater than 25 nm. Preferably, the diameters of the mesopores of the supported catalyst are homogeneous, ie at least 75%, more preferably at least 85% of the macropores have a diameter which is in the range of 40% of the mean diameter.

[0074] The total pore volume is preferably in the range of 0.3 cm 3 / g up to 2.5 cm 3 / g, especially in the range of 0.5 cm 3 / g to 1.5 cm 3 / G.

[0075] The carrier body of the present invention comprises a refractory oxide as carrier material.

[0076] The term "refractory oxide" used here refers to a metal-containing oxide that is chemically and physically stable at high temperatures, particularly at the operating temperatures and conditions prevailing in reactors. Refractory oxides are also often referred to as heat-resistant oxides.

[0077] The refractory oxide may be an oxide of a transition metal or a main group metal, for example an oxide of a Group 3 metal, an oxide of a Group 13 metal, an oxide of a Group 4 metal, an oxide of a Group 14 metal, an oxide of a Group 5 metal, or a combination of two or more of the above-mentioned metal oxides. The refractory oxide can be selected from the group consisting of titanium oxides (e.g. TiO2), zirconium oxides (e.g. ZrO2), niobium oxides (e.g. Nb2O5), tantalum oxides (e.g. Ta2O5), cerium oxides (e.g. CeO2), aluminum oxides (e.g. a- or Y-Al2O3), SiO2, BeO, MgO, CaO, SrO, BaO, ZnO, Y2O3, La2O5, SnO2, CdO, PbO, As2O3, Bi2O5, Sb2O5, V2O5, Cr2O5, MoO5, WO3 and a mixture of two or more of the aforementioned metal oxides.

[0078] The refractory oxide preferably comprises an aluminum oxide, magnesium oxide, silicon oxide, molybdenum oxide, tungsten oxide, titanium oxide, zirconium oxide, a mixed oxide or composite oxide of two or more thereof, particularly preferably an aluminum oxide or a mixed oxide or composite oxide of aluminum oxide, preferably α- or γ-Al2O3. The term "mixed oxide" as used here refers, on the one hand, to a mixture of oxides in a single phase, as is commonly known in the relevant art. It thus refers to "solid solutions" with a uniform crystal lattice in which the individual metal oxides can no longer be distinguished. It is also used herein for physical mixtures of oxides that comprise metal oxide agglomerates without a uniform crystal lattice and in which phases of the individual metal oxides can be distinguished.The term “composite oxide” as used herein generally refers to a composition of oxides having more than one phase, as is commonly known in the relevant art.

[0079] Suitably, the supported catalyst comprises the refractory oxide to at least 60 wt.%, based on the total weight of the supported catalyst, more preferably to at least 70 wt.%, even more preferably to at least 80 wt.%, most preferably to at least 85 wt.%, most preferably to at least 90 wt.%.

[0080] The refractory oxide may be doped, in other words, the refractory oxide may comprise a dopant. Support materials doped with a dopant are available using methods known in the art. Doping may improve the heat resistance of the support material, suppress the aggregation of the catalytically active component, and / or increase the activity and stability of the supported catalyst.

[0081] Suitable dopants can be selected from the group consisting of rare earth metals, transition metals, alkali metals, alkaline earth metals, and mixtures thereof. In particular, the dopant can comprise at least one element selected from the group consisting of sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), magnesium (Mg), calcium (Ca), cerium (Ce), zirconium (Zr), titanium (Ti), silicon (Si), manganese (Mn), yttrium (Y), lanthanum (La), barium (Ba), praseodymium (Pr), gadolinium (Gd), samarium (Sm), neodymium (Nd), scandium (Sc), tantalum (Ta), their oxides, and mixtures of two or more of the above. The dopant preferably comprises barium, calcium, and / or potassium.

[0082] Particularly preferably, the doped refractory oxide is an aluminum oxide doped with barium, barium oxide, calcium, calcium oxide, potassium and / or potassium oxide, a mixed oxide of aluminum oxide doped with barium, barium oxide, calcium, calcium oxide, potassium and / or potassium oxide, or a composite oxide of aluminum oxide doped with barium, barium oxide, calcium, calcium oxide, potassium and / or potassium oxide.

[0083] In preferred embodiments, the refractory oxide comprises an alkali metal and / or an alkaline earth metal. The alkali metal or alkaline earth metal can be present as a component with which the refractory oxide is provided and / or as a dopant of the refractory oxide. In particular, the support material comprises barium, calcium, and / or potassium.

[0084] The supported catalyst can comprise Al2O3 as the refractory oxide, at least ruthenium as the catalytically active component, and platinum (Pt), palladium (Pd), rhodium (Rh), iridium (Ir), magnesium (Mg), calcium (Ca), strontium (Sr), and / or barium (Ba) as a further component. Examples of preferred embodiments of the supported catalyst are RU / Al2O3, Ru+Pt / AhOs, Ru+Pd / AhOs, Ru+Rh / AhOs, Ru+Ir / AhOs, Ru+Mg / AhOs, Ru+Ca / AhOs, Ru+Sr / AhOs, or Ru+Ba / AhOs.

[0085] In a particularly preferred embodiment, the supported catalyst comprises an aluminum oxide, in particular Y-Al2O3, as refractory oxide, and 0.01-20 wt.% ruthenium. In these cases, it may be preferred that the supported catalyst has a BET surface area in the range of 10 m 2 / g up to 400 m 2 / g, preferably in the range of 20 m 2 / g up to 300 m 2 / g. In a preferred embodiment, the supported catalyst has a BET surface area of ​​less than 400 m when using alumina as the support material. 2 / g, preferably less than 300 m 2 / g, particularly preferably less than 200 m 2 / G.

[0086] In a further particularly preferred embodiment, the supported catalyst comprises, as refractory oxide, an aluminum oxide, in particular Y-Al2O3, 0.01-20 wt.% ruthenium, and 1.0-10.0 wt.% barium. In these cases, it may be preferred that the supported catalyst has a BET surface area in the range of 10 m 2 / g up to 400 m 2 / g, preferably in the range of 20 m 2 / g up to 300 m 2 / g. In a preferred embodiment, the supported catalyst has a BET surface area of ​​less than 400 m when using alumina as the support material. 2 / g, preferably less than 300 m 2 / g, particularly preferably less than 200 m 2 / G.

[0087] Processes for producing ruthenium-coated support bodies are known to those skilled in the art. Typically, a composition containing at least the refractory oxide is provided, which is then formed into the desired shape, for example, by extrusion, pressing, granulation, or casting. In addition to the refractory oxide, the composition may also contain other components such as solvents or binders.

[0088] In such processes, the refractory oxide is preferably provided in powder form. Suitable processes for producing ruthenium-coated support bodies may include further steps, for example, heating the shaped powdered refractory oxide.

[0089] If the refractory oxide is already coated with at least ruthenium during the forming process, a support body with a homogeneous coating of ruthenium is obtained. A homogeneous coating means that the ruthenium is present largely evenly in the inner and outer regions of the support body.

[0090] If the refractory oxide is not coated with ruthenium during the forming process, a ruthenium-free support body is initially obtained, which is then coated with at least ruthenium in a subsequent step. In such a manufacturing process, the ruthenium is not homogeneously distributed throughout the support body. It has proven advantageous if the ruthenium is not homogeneously distributed throughout the support body. In other words, it is advantageous if the supported catalyst is a coated catalyst, in which the ruthenium is primarily present in the peripheral region of the support body. Such coated catalysts enable the most efficient use of the precious metal.

[0091] Advantageously, the thickness of the edge region is less than 1000 pm, preferably less than 700 pm, in particular less than 500 pm. The thickness of the edge region can be determined by SEM in combination with EDX measurement as described below. For the purposes of the present invention, the edge region of the supported catalyst is understood to mean both the edge region of the peripheral surface and edge regions within the channels.

[0092] Preferably, at least 60 wt.% of the ruthenium, based on the total amount of ruthenium, is present in the outer 40 ol.% of the supported catalyst, in particular at least 70 wt.%.

[0093] The carrier material can be coated with ruthenium using methods known to those skilled in the art, such as impregnation, precipitation, chemical vapor deposition (CVD), coating, or spraying. The coating can be carried out in one or more steps.

[0094] The preparation typically involves combining the support material with a ruthenium precursor compound, which is usually provided in a composition comprising at least one solvent. Following the combination, the ruthenium precursor compound can be precipitated and / or reduced, as well as a drying and / or calcination step. The supported catalyst is preferably obtained by impregnating the support material with the composition and subsequent reduction. Optionally, a thermal treatment can be performed before or after the reduction.

[0095] The support material can be impregnated prior to shaping or when the support material is already present as a shaped body. In the first case, for example, a powdered support material can initially be impregnated and then shaped, for example by extrusion or pressing. In such cases, the ruthenium is homogeneously distributed throughout the shaped body. Various impregnation processes are known to those skilled in the art, for example capillary-controlled impregnation (so-called "incipient wetness" methods) and diffusion-controlled impregnation (so-called adsorption-controlled methods). In principle, both approaches are suitable for producing suitable supported catalysts for the present invention. Impregnation is generally understood to mean the contact of a support material with a compound and the resulting adsorption of the compound on the surface of the support material.In the case of a porous carrier material, this is in particular also an inner surface, i.e. one located within the pores.

[0096] The combination is achieved, for example, by adding the composition to a suspension of the carrier material in a solvent and mixing this mixture. However, it is also possible to spray such a composition onto the carrier material or to add the carrier material to such a composition and then mix the mixture thoroughly. Methods for mixing such systems, such as stirring, are known to those skilled in the art; forced mixers, free-fall mixers, stirrers, flow mixers, or mixing pumps can be used.

[0097] The supported catalyst can be prepared, for example, by a process comprising

[0098] I) impregnating the support material with a composition containing a ruthenium precursor compound and a solvent;

[0099] II) a reduction step.

[0100] The result of impregnation step I) is an impregnated support material (i.e., one loaded with the ruthenium precursor compound). Preferably, a homogeneous or uniform coating of the support material with this ruthenium precursor compound is achieved.

[0101] A "solvent" herein means that the solvent comprises at least one liquid substance in which the ruthenium precursor compound is soluble. The at least one solvent may contain several chemical substances, i.e., the solvent may also be a solvent mixture. The at least one solvent may be selected from the group consisting of water and organic solvents. The organic solvent may be selected from a variety of common organic solvents. Conveniently, the organic solvent is essentially volatile under the processing conditions of the composition. Organic solvents may be, for example, alcohols such as methanol or ethanol. Preferably, the solvent consists of at least 60 vol.% water, more preferably at least 70 vol.%, in particular at least 80 vol.%. It may be advantageous for the solvent to consist entirely of water.

[0102] In a preferred embodiment, the composition comprises the solvent in an amount of 20 to 99.5 wt.%, based on the total weight of the composition, preferably 30 to 95 wt.%. Advantageously, the composition comprises the solvent in an amount of at least 50 wt.%, particularly preferably at least 80 wt.%, and most preferably at least 90 wt.%.

[0103] The amount of ruthenium in the composition can vary over a wide range and is determined by the intended loading of the support material with ruthenium. The “amount of ruthenium” refers to the ruthenium content in the composition; in other words, it does not refer to the amount of the total ruthenium precursor compound. The composition preferably comprises 0.5 to 75 wt.% ruthenium, based on the total weight of the composition comprising the at least one solvent and the ruthenium compound. In one embodiment, the composition comprises 1 to 60 wt.% ruthenium, preferably 5 to 50 wt.%. Particularly good results are obtained when the composition contains ruthenium in an amount of at least 0.5 wt.%, in particular at least 1 wt.%, preferably at least 5 wt.%, more preferably at least 10 wt.%.

[0104] Ruthenium precursor compounds are those compounds of ruthenium that can be converted to the elemental state by thermal decomposition or wet chemical reduction. Suitable compounds include salts, complexes, or organometallic compounds of ruthenium. Examples of suitable ruthenium compounds include ruthenium nitrate, ruthenium acetate, ruthenium pentacarbonyl, ruthenium acetylacetonate, ruthenium oxalate, ruthenium nitrosyl oxalate, ruthenocene, and ruthenium nitrosyl nitrate. The composition can contain only one ruthenium precursor compound or several ruthenium precursor compounds.

[0105] The ruthenium precursor compound is preferably a halogen-free ruthenium compound, in particular a chloride-free ruthenium compound. Halogen-free, in particular chloride-free, ruthenium compounds are understood to be ruthenium compounds that contain no halogen or chloride components, apart from unavoidable impurities, for example, residues resulting from the manufacturing process. The production of supported catalysts using halogen- or chloride-containing precursor compounds requires washing of the produced material, which makes production expensive and complex.

[0106] It has proven advantageous if the supported catalyst used in the process according to the invention has been prepared using an oxalate-containing ruthenium precursor compound, or in other words, if the catalytically active ruthenium component supported on the support material has been prepared at least partially from such a precursor compound. It has been found that such supported catalysts exhibit high long-term stability and, at the same time, require a short run-in phase to achieve full activity. Furthermore, they are particularly advantageous in production because complex washing steps can be eliminated and no harmful decomposition products are formed.

[0107] Preferably, the ruthenium in the oxalate-containing ruthenium precursor compound can be converted to the elemental state via thermal decomposition or wet-chemical reduction. In particular, the ruthenium in the oxalate-containing ruthenium precursor compound can be converted to the elemental state via thermal decomposition under inert or reducing conditions; in other words, other oxidation states can also be obtained under non-reducing or non-inert conditions. It is advantageous that such ruthenium precursor compounds, in addition to forming the catalytically active ruthenium component, can be decomposed with virtually no residue. Compared to, for example, carbonyl complexes of ruthenium, they also have the advantage of being less volatile and, as well as the corresponding decomposition products, less toxic or even non-toxic.The oxalate-containing ruthenium precursor compound is advantageously decomposable at a temperature below 500 °C, in particular below 400 °C, particularly preferably below 300 °C.

[0108] Oxalate-containing ruthenium precursor compounds are compounds that contain ruthenium in any oxidation state and at least one oxalate unit. The ruthenium can be present in a single or multiple oxidation states within the compound. The term "oxalate unit" refers to a C2O4 that acts as a non-complexing or ligand, i.e., complexing. 2- Dianion. The ruthenium precursor compound can contain one or more ruthenium centers.

[0109] The oxalate-containing ruthenium precursor compound can be ruthenium-containing salts or ruthenium complex compounds which, in addition to at least one oxalate ligand (Ox), also contain at least one or more other ligands, for example hydroxy ligands (OH), carbonate ligands (CO3), nitrosyl ligands (NO), ammonia ligands (NH3) or hydrate ligands (H2O) as well as other ligands which decompose without residue.

[0110] Examples of suitable ruthenium precursor compounds include ruthenium oxalates, ruthenium nitrosyl oxalates, ruthenium carbonate oxalates, and their respective ammonium salts, hydrates, and acids.

[0111] The preparation of oxalate-containing ruthenium precursor compounds and their solutions is described, for example, in DE 102007014914 A1 and DE 1533088 A1. In suitable preparation processes, isolated ruthenium precursor compounds can be used, as can their solutions.

[0112] In a preferred embodiment, the carrier material is suspended in the composition during the impregnation step. A suspension, within the meaning of the present invention, is a mixture of a solid and a liquid, wherein the solid is uniformly distributed in the form of finely dispersed solids in the liquid.

[0113] In an alternative embodiment, the carrier material and the composition are in the form of an impregnated powder during the impregnation step. This means that the solution is added only to the extent that the carrier material is wetted.

[0114] In a further embodiment, the carrier material is already in the form of the carrier body and the composition is added to such an extent that the pores of the carrier body are completely filled.

[0115] The impregnation step can be carried out at room temperature. However, the impregnation step can also be carried out at a lower or higher temperature than room temperature. During the impregnation step, the temperature of the mixture containing support material and the composition can be, for example, 10°C to 90°C, more preferably 20°C to 80°C. The duration of the impregnation step is selected so that the ruthenium precursor compound can be deposited on the support material in sufficient quantity. A person skilled in the art can determine a suitable time period based on routine experiments.

[0116] Preferably, the ruthenium precursor compound completely separates from the solution onto the support material. After the impregnation step, the solvent is therefore free of the ruthenium precursor compound.

[0117] If the support material is to be provided with multiple components, it may be preferable to provide the relevant compounds together in one composition. However, it may also be preferable to provide the relevant compounds in separate compositions. Both variants are suitable for providing the support material simultaneously with, for example, ruthenium and iridium or with ruthenium and barium.

[0118] In further embodiments, it may be advantageous to equip the support material sequentially with the different components, i.e. first with ruthenium and subsequently with the further component or vice versa, wherein the reduction step at the end can be carried out for both species jointly or as an intermediate step.

[0119] For example, an aluminum oxide can be coated first with ruthenium and then with barium. The barium is preferably applied to the aluminum oxide in a composition comprising barium acetate. However, it can also be advantageous to coat an aluminum oxide first with barium and then with ruthenium. The barium can also be applied to the aluminum oxide in this order, preferably in a composition comprising barium acetate.

[0120] The amount of support material used during production depends on the desired amount of ruthenium to be deposited on the support material and thus also on the concentration of ruthenium in the composition of the ruthenium precursor compound used.

[0121] The carrier material is present during the impregnation step, for example, in a range of 5 wt% to 95 wt%, based on the total amount of composition and carrier material, more preferably in a range of 10 wt% to 90 wt%.

[0122] The composition may also contain other components, such as acids.

[0123] Optionally, the process may also comprise drying or thermal treatment of the impregnated carrier material after step I) and before step II).

[0124] Preferably, at least 90% of the solvent is removed before the reduction step; the impregnated support material can also be completely dried to constant weight.

[0125] Such a thermal treatment is also known to those skilled in the art as calcination. The term "calcination" refers to a thermal treatment that preferably involves the fixation of a metallic component to a carrier material.

[0126] In a preferred embodiment, the thermal treatment of the impregnated support material leads to the decomposition of the ruthenium precursor compound. The thermal treatment is preferably carried out in the presence of oxygen. The thermal treatment can take place at a temperature of less than 1000°C, 900°C, 800°C, 700°C, 600°C, 500°C, 400°C, or less than 300°C. In one embodiment, the impregnated support material is thermally treated at a temperature of 350°C to 500°C. The thermal treatment is preferably carried out for a period of 0.5 h to 24 h, more preferably for a period of 2 h to 18 h. Calcination can take place under atmospheric conditions or under inert gas conditions.

[0127] Drying and calcining can also be carried out in one step.

[0128] In step II) of the process for producing the supported catalyst, a reduction takes place. This means that the ruthenium precursor compound present on the support material after impregnation is at least partially converted to a lower oxidation state.

[0129] Methods for reduction and suitable reducing agents are known in principle to those skilled in the art. The reduction step can be carried out, for example, under a reducing atmosphere or by wet-chemical means. In particular, the reduction step can be carried out under a forming gas atmosphere, with reducing acids, their salts, or reducing boron compounds. The term forming gas is understood by those skilled in the art to mean a gas mixture containing nitrogen and hydrogen, for example, 95 vol.% nitrogen and 5 vol.% hydrogen. In the case of wet-chemical reduction, formic acid or a formic acid salt, for example, sodium formate, is preferably used as the reducing agent.

[0130] In the case of wet chemical reduction, the reduction step can be carried out directly in the impregnation solution, i.e., the impregnated support material obtained after step I) is not separated from the solvent. In other words, it may be preferable to add the reducing agent directly after step I).

[0131] The reduction step is carried out, for example, at a temperature below 700°C, more preferably below 600°C, particularly preferably below 400°C. In the case of wet-chemical reduction, it may be preferable to carry out the reduction at a temperature below 100°C. The reduction step is preferably carried out for a period of 0.5 h to 24 h, preferably for a period of 2 h to 15 h.

[0132] It may be preferable to subject the material obtained in step II) to a further process step. In a preferred embodiment, the material obtained in step II) is filtered off and dried. Drying is carried out, for example, at a temperature below 250°C, more preferably below 200°C, even more preferably below 150°C. In particular, drying can be carried out under reduced pressure, preferably at a pressure of below 300 mbar. Drying is preferably carried out in the absence of oxygen. Drying is preferably carried out for a period of 0.5 h to 30 h, preferably for a period of 2 h to 24 h.

[0133] After equipping a powdered carrier material, it undergoes a further process step to obtain a ruthenium-coated carrier body, for example, pressing or extrusion. Such processes for shaping powdered carrier materials are known to those skilled in the art.

[0134] The process according to the invention comprises contacting the supported catalyst with the ammonia-containing gas.

[0135] Contacting is preferably carried out at a pressure in the range of 1 to 300 bar, more preferably in the range of 10 to 200 bar.

[0136] Advantageously, the gas hourly space velocity (GHSV) is in the range of 1,000 to 100,000 h' 1 , especially in the range from 1,500 to 50,000 h' 1 , particularly preferably in the range of 2,000 to 10,000 h' 1It may be advantageous to increase the residence time of the ammonia-containing gas in the catalyst bed by reducing the NH3 flow rate.

[0137] Since the reaction is endothermic, it may be advantageous to carry out the reaction at elevated temperature. The temperature is preferably between 300°C and 800°C, in particular between 400°C and 700°C. In particular, it may be advantageous to heat the supported catalyst or supported catalyst bed to this temperature.

[0138] The supported catalyst used allows the process to be carried out even at lower temperatures, advantageously below 600 °C, especially below 500 °C, and most advantageously below 400 °C. The ammonia-containing gas can be preheated before the contacting step. In preferred embodiments, the ammonia-containing gas is preheated to at least 200 °C, more preferably to at least 400 °C.

[0139] The process according to the invention is preferably carried out in a reactor which consists at least partly of a corrosion-resistant material, for example stainless steel.

[0140] The reactor may be a closed loop reaction system, a flow reaction system, or a batch reaction system, with the flow reaction system being most preferred from a practical point of view.

[0141] The invention further relates to the use of a ruthenium-containing supported catalyst in a process for producing hydrogen from an ammonia-containing gas by contacting the supported catalyst with the ammonia-containing gas, wherein the supported catalyst is provided in the form of a ruthenium-equipped support body, wherein the support body

[0142] - comprises a refractory oxide as a carrier material,

[0143] - is cylindrical and

[0144] - has at least three spaced-apart channels extending completely through the catalyst support, one of the channels extending along the central longitudinal axis.

[0145] All statements made for the process for producing hydrogen from an ammonia-containing gas also apply to the use of the ruthenium-containing supported catalyst for this application.

[0146] The invention is explained in more detail below with reference to figures. However, it is not limited to these embodiments.

[0147] Figure 1 shows cross-sections of carrier bodies with a different number of channels that are particularly suitable for the process according to the invention. The carrier bodies have an outer diameter DA; the channels are characterized by their inner diameter DK. The carrier body in Fig. 1A has three channels, the one in Fig. 1B has four, and the one in Fig. 1C has five channels, each with the same inner diameter. The carrier body in Fig. 1D has eight channels, with the inner diameter DKI of the central channel being larger than the inner diameter DK2 of the seven non-central channels.

[0148] Figure 2 shows side views of carrier bodies with a length L and an outer diameter DA. The dashed line indicates the position of the central longitudinal axis. The carrier body in Fig. 2 A has straight end faces. The carrier body in Fig. 2 B has curved end faces.

[0149] The measurement methods used in the present invention are listed below. If no test method is specified, the corresponding ISO method was used to determine the respective parameter, as valid at the time of filing this application. If no specific measurement conditions are specified, the measurement was performed at room temperature (298.15 K) and atmospheric pressure (100 kPa).

[0150] Measurement methods

[0151] Specific BET surface area

[0152] The BET specific surface area was determined using nitrogen as adsorbate at 77 K according to BET theory (multi-point method, ISO 9277:2010).

[0153] CO adsorption

[0154] The precious metal surface area of ​​the catalysts was determined via CO adsorption. For this purpose, a catalyst was first reduced for 20 minutes at 400 °C under forming gas consisting of 95% argon and 5% hydrogen in a closed container. Subsequently, carbon monoxide (CO, with helium as the carrier gas) was pulsed into the container containing the catalyst. This continued until constant CO peaks were detected behind the catalyst. The amount of CO absorbed by the catalyst was determined by determining the peak area of ​​the added CO and by determining the peak area of ​​the converted CO. For this purpose, the integral of the area of ​​the converted CO was subtracted from the integral of the area of ​​the added CO. From the resulting amount of absorbed CO, the amount of CO stored for each amount of catalytically active composition used was calculated.By means of conversions, the surface area of ​​the active precious metal centers (often referred to as CO surface or precious metal surface) could be determined from the measured amount of CO stored at the active centers.

[0155] Pore ​​volume and pore diameter distribution

[0156] The pore volume and pore diameter distribution were determined using mercury porosimetry according to ISO 15901-1:2016.

[0157] Determination of precious metal content via ICP-OES

[0158] The precious metal content was determined using inductively coupled plasma optical emission spectrometry (ICP-OES). First, 500 mg of the sample was dissolved in 25 mL of HF+HCl. The solution was then made up to 250 mL with water.

[0159] SEM-EDX characterization

[0160] The distribution of ruthenium in the support was characterized using SEM images (scanning electron microscopy) coupled with EDX spectroscopy (energy dispersive X-ray spectroscopy). For sample preparation, coated supports were embedded in resin, sectioned, and polished. The analyses were performed using a Jeol JSM-IT100 scanning electron microscope equipped with an integrated energy dispersive X-ray analysis system, using a 20 keV electron beam.

[0161] pressure loss

[0162] The pressure drop of various catalyst beds was determined using a PTB-100 (Bastra Engineering). The system was first calibrated in an empty state. A tubular sample holder (150 mm diameter) was then loaded with the catalyst bodies (filling height 50 mm). A pressure sensor was used to determine the pressure difference at gradually increased flow velocity. The results were evaluated using the device's own software.

[0163] Side fracture hardness of the catalyst carrier bodies

[0164] To determine the side-break hardness, specimens were loaded between two parallel plates with increasing force until fracture occurred. The force recorded at fracture corresponds to the side-break hardness. Samples were prepared by drying overnight at 150 °C under vacuum and then cooling. The determination was performed using a tablet hardness tester (type ERWEKA TBH 325). The determination was carried out under a constant force increase of 20 N / s.

[0165] Abrasion resistance

[0166] Abrasion resistance was determined by mechanical loading in a rotating steel cylinder in the presence of additional steel balls. Sample preparation was performed by pre-sieving the material, drying it overnight at 120 °C under a nitrogen atmosphere, and finally cooling it. The prepared material was weighed into a steel cylinder, which was then rotated around its axis for 30 minutes at 80 rpm. The resulting abrasion debris was sieved and weighed (A). The abrasion debris is expressed as a percentage of the original weight (Mo) of the material:

[0167] Abrasion [%] = A * M o ' 1 * 100.

[0168] Test of catalytic activity

[0169] The prepared catalysts were tested in a fixed-bed test rig consisting of a reactor with a heatable quartz glass tube.

[0170] Before the reaction, the catalyst supports were installed in the test rig and activated under hydrogen at 550 °C. After activation, the catalyst material was heated to the respective reaction temperature in a nitrogen stream (100 mL / min). After a 10-minute heating phase, a gas mixture (NH3-N2 mixture in a ratio of 9:1) was passed over the catalyst material. Gas samples were taken at the reactor outlet using a gas-tight syringe, and the nitrogen-to-hydrogen ratio was determined by gas chromatography.

[0171] The following examples illustrate the invention in more detail. However, these examples are not to be construed as limiting.

[0172] For the comparative example (VB), Y-AI2O3 spheres with a diameter of 2.5 mm, a BET surface area of ​​215 m 2 / g and a pore volume of 0.8 mL / g were used. The spheres were first pretreated with a NaOH solution and then dried. For the inventive examples (EB), y-Al2O3 cylinders with an outer diameter of 12 mm and seven channels with an inner diameter of 2 mm each were used, which were also pretreated with NaOH. The BET surface area of ​​the supports was 105 m 2 / g and the pore volume 0.6 mL / g.

[0173] The ruthenium loading was 1.5 wt% in all examples.

[0174] VB - (Ru / AI2O3 with RuCh)

[0175] The pretreated Al2O3 spheres were impregnated with a Ru chloride (RuCh) solution and dried (30 min at 70 °C). For calcination, the dried material was treated in an oven at 450 °C for 4 h. The Ru-coated Al2O3 was washed under flowing water for 4 days. Finally, the material was dried and finally reduced under forming gas in an oven at 250 °C for 16 h.

[0176] EB1 (Ru / AI2O3 with RuCh)

[0177] The pretreated AhO3 cylinders were coated with ruthenium analogously to VB.

[0178] EB2 (Ru / AhOa with Ru-nitrosyl oxalate)

[0179] The pretreated AhO3 cylinders were impregnated with a solution of Ru nitrosyl oxalate and dried (30 min at 70 °C). For calcination, the previously dried material was treated in an oven at 450 °C for 4 h. Finally, the material was reduced under forming gas in an oven at 250 °C for 16 h.

[0180] EB3 (Ru / AhOa with Ru oxalate)

[0181] The pretreated AhO3 cylinders were impregnated with a Ru oxalate solution and dried (30 min at 70 °C). Calcination and reduction were carried out analogously to EB2.

[0182] Figure 3 shows the pressure drop of catalyst beds with carrier bodies with channels (EB1) compared to carrier bodies without channels (VB). Spherical solid spheres cause a significantly higher pressure drop than carrier bodies with a central channel and six additional channels arranged around it, which negatively impacts the efficiency of a reactor with such a catalyst bed.

Claims

CLAIMS:

1. A process for producing hydrogen from an ammonia-containing gas, comprising the following steps: i) providing a supported catalyst in the form of a ruthenium-equipped support body, wherein the support body comprises a refractory oxide as support material, is cylindrical and has at least three spaced-apart channels extending completely through the support body, wherein one of the channels extends along a central longitudinal axis, ii) contacting the supported catalyst with the ammonia-containing gas.

2. A process according to claim 1, wherein the ammonia-containing gas contains at least 70 vol.% Contains ammonia.

3. The method according to claim 1 or 2, wherein the carrier body has 3 to 10 channels.

4. Method according to one of the preceding claims, wherein the carrier body has a length and / or an outer diameter in the range of 0.5 mm to 50 mm.

5. A method according to any one of the preceding claims, wherein the cross-sectional area of ​​the channels is in a range of 0.3 mm 2 up to 15 mm 2 lies.

6. Method according to one of the preceding claims, wherein the proportion of Channel cross-sectional areas of the total cross-sectional area of ​​the carrier body is at least 10%.

7. Method according to one of the preceding claims, wherein the carrier body has at least one curved end face.

8. A process according to any one of the preceding claims, wherein the supported catalyst contains not more than 20 wt% ruthenium.

9. Process according to one of the preceding claims, wherein the supported catalyst is provided with at least one alkali metal or alkaline earth metal.

10. The process according to claim 9, wherein ruthenium and the alkali metal or alkaline earth metal are present in a molar ratio in the range of 1:1 to 1:

15.

11. A process according to any one of the preceding claims, wherein the refractory oxide is selected from the group consisting of aluminum oxide, magnesium oxide, silicon oxide, molybdenum oxide, tungsten oxide, titanium oxide, zirconium oxide, combinations, mixed oxides and composite oxides of two or more of the aforementioned metal oxides.

12. Method according to one of the preceding claims, wherein the The supported catalyst is a shell catalyst.

13. The process according to claim 12, wherein the coated catalyst comprises an edge region having a thickness of less than 1000 pm.

14. A process according to any one of the preceding claims, wherein the contacting is carried out at a pressure in the range of 1 to 300 bar.

15. Use of a ruthenium-containing supported catalyst in a process for Production of hydrogen from an ammonia-containing gas by contacting the supported catalyst with the ammonia-containing gas, wherein the supported catalyst is provided in the form of a ruthenium-equipped support body, wherein the support body comprises a refractory oxide as support material, is cylindrical and has at least three spaced-apart channels extending completely through the catalyst support, wherein one of the channels extends along the central longitudinal axis.

Images