Catalyzer and electrochemical cell device

Abstract

The invention relates to a catalyzer (100) for oxidizing methane and / or hydrogen, in particular for use in electrochemical cell devices (10), preferably fuel cell devices (10), wherein the catalyzer (100) has a catalytically active material (108) and a protective material (110) which is provided for binding chromium, and the catalytically active material (108) and the protective material (110) are provided on a main part (102). According to the invention, the catalyzer (100) has between 30 g and 200 g of protective material (110) per liter of catalyzer volume, preferably between 40 g and 150 g per liter of catalyzer volume, particularly between 50 g and 100 g per liter of catalyzer volume.

Description

[0001] Description

[0002] title

[0003] catalyst, electrochemical cell device

[0004] The invention relates to a catalyst according to the preamble of the independent claim. The invention further relates to an electrochemical cell device comprising such a catalyst.

[0005] State of the art

[0006] The oxidation of methane and / or hydrogen using a catalyst is known in the art. Hot, humid gas streams containing methane and / or hydrogen often also contain chromium or chromium compounds. Chromium and chromium compounds, especially chromium(VI) oxide, can accumulate in the catalyst, negatively impacting the catalytic performance of the catalyst and leading to catalyst degradation.

[0007] Disclosure of the invention

[0008] Advantages

[0009] The present invention describes a catalyst for the oxidation of methane and / or hydrogen, in particular for use in electrochemical cell devices, preferably fuel cell devices, wherein the catalyst comprises an active catalytic material and a protective material intended to bind chromium, wherein the catalytic material and the protective material are arranged on a base body. According to the invention, the catalyst comprises between 30 g and 200 g of protective material per liter of catalyst volume, preferably between 40 g and 150 g per liter of catalyst volume, particularly preferably between 50 g and 100 g per liter of catalyst volume. In this way, the accumulation of chromium or chromium compounds, in particular chromium(VI) oxide, in the catalyst can be prevented, so that the oxidation rate of methane and / or hydrogen does not decrease as rapidly as in a catalyst without the chromium protection according to the invention.In particular, this can extend the operating time of the catalyst until replacement due to chromium accumulation is necessary, or prevent such replacement altogether. A further advantage is that using a catalyst according to the invention results in less chromium or chromium compounds being released into the environment.

[0010] Chromium protection is achieved by the protective material reacting with volatile chromium compounds under the operating conditions typical for catalysts for the oxidation of methane and / or hydrogen to form fairly stable chromium compounds. The chromium is fixed by its bond to the protective materials and is thus prevented from negatively interacting with the catalytic material and an optional support material of the catalyst. Typical operating conditions for catalysts for the oxidation of hydrogen typically have average temperatures inside the catalyst between 300 °C and 850 °C, preferably between 350 °C and 800 °C, particularly preferably between 400 °C and 600 °C. Typical operating conditions for catalysts for the oxidation of methane typically have average temperatures inside the catalyst between 600 °C and 850 °C, preferably between 620 °C and 750 °C, particularly preferably between 630 °C and 650 °C.

[0011] The catalyst, particularly with regard to the amount of protective material, should be designed to accommodate the expected amount of chromium over its entire operating life. For this design, it is particularly conceivable to use simulations of the stability of the chromium-containing compounds formed, which can be based in particular on experimental data on chromium deposition.

[0012] In the prior art, when designing the catalyst for the chosen application, particularly when used in an electrochemical cell device, the degradation or declining performance due to the effect or incorporation of chromium would have to be taken into account. In particular, the catalyst would have to be designed with a higher catalytic performance than necessary, which may be significantly higher than the desired catalytic performance, so that the catalyst can still deliver the required or desired catalytic performance even after its degradation by chromium at the end of the desired service life. The catalyst according to the invention, in contrast, has significantly reduced degradation, so that after a longer period of operation, the catalytic performance decreases less than with prior art catalysts or—depending on the design—remains almost constant.This makes it possible to design the catalyst according to the invention with a lower initial catalytic performance than a prior art catalyst. In particular, the catalyst according to the invention can thus contain significantly less catalytic material than a prior art catalyst for the same application.

[0013] Such a catalyst can be used, in particular, to remove methane and / or hydrogen from a fluid or gas, for example, because it is undesirable in a subsequent process or should not be released into the environment. The fluid or gas converted in the catalyst is also referred to below as the process gas.

[0014] The oxygen required for oxidation can already be present in the process gas, whereby the oxygen can be present in the form of O2 and / or other oxygen-containing compounds, such as water or ozone. It is also conceivable for the oxygen to be supplied to the process gas upstream of the catalyst. Advantageously, a line for an oxidizing agent can be arranged upstream of the catalyst in terms of flow technology, in particular a line for air and / or a second, oxygen-containing process gas. The second, oxygen-containing process gas can, for example, be produced in a sub-process of the same overall process. Examples of process gas are product gas from electrolysis, product gas from the reforming of water and / or methane, as well as fluids or gases inside fuel cell devices, for example fuel, anode exhaust gas, cathode exhaust gas, reformed gas and / or recirculate.The oxidation of the hydrogen and / or methane flowing through the catalyst heats the catalyst. Process gases can typically contain other components that are advantageously oxidized for subsequent processes or to protect the environment, particularly harmful gases. Examples of harmful gases include ammonia, hydrogen, carbon monoxide, soot particles, and organic compounds, such as hydrocarbons, e.g., formaldehyde. The catalyst is advantageously designed to also oxidize harmful gases, particularly by using catalytic materials designed for this purpose or by using ratios of catalytic material compositions adapted for this purpose, for example, an increased platinum content.

[0015] In particular, the catalyst according to the invention also reduces the partial oxidation of harmful gases caused by chromium. The partial oxidation of harmful gases caused by chromium is frequently observed after a certain period of operation in prior art catalysts for the oxidation of methane and / or hydrogen. Such partial oxidations of hydrocarbons form, for example, carbon monoxide, aldehydes, ketones, furans, and acids. A typical example of a hydrocarbon is methane. In this context, hydrocarbons also include other compounds containing carbon and hydrogen, such as formaldehyde, formic acid, thiophene, or hydrogen cyanide.

[0016] By accumulating chromium on a prior art catalyst, methane and possibly also harmful gases can be oxidized or partially oxidized to a greater extent, which can be undesirable in downstream processes or for the environment. The catalyst according to the invention largely suppresses, for example, the partial oxidation of a large number of organic compounds—especially methane—to carbon monoxide, as well as the oxidation of nitrogen monoxide to nitrogen dioxide and other nitrogen compounds in nitrogen oxidation states greater than two.

[0017] Gaseous nitrogen N2 is not considered a harmful gas in this context. Under typical operating conditions of the catalyst, the catalyst according to the invention largely suppresses the oxidation of gaseous nitrogen. Appropriate operating parameters for completely or largely completely suppressing these reactions can be advantageously selected for the catalyst according to the invention.

[0018] A key effect of the inventive solution using a catalyst according to the invention is that less unwanted chromium enters downstream processes—advantageously, no chromium or almost no chromium. Such downstream processes include, for example, the treatment of fluids in fuel cell devices and in other energy generation processes that utilize hydrogen and / or methane, for example, in their cyclic flow processes; the treatment of process gases and exhaust air from the chemical industry, the steel industry, and other areas of hydrogen production, hydrogen processing, and hydrogen utilization. Of particular note is the protection of the environment, into which particularly little chromium enters due to the catalyst according to the invention.

[0019] An active catalytic material or active materials is understood to be a substance or mixture of substances that increases the reaction rate by lowering the activation energy of a chemical reaction without itself being consumed in the process. In this case, the active catalytic material is, in particular, a substance that increases the reaction rate for the oxidation of methane and / or hydrogen. Examples of active catalytic materials for such oxidation reactions are precious metals, non-ferrous metals, and / or ferrous metals, such as iron, nickel, manganese, cobalt, and others. The active catalytic material can comprise a mixture of precious metals, non-ferrous metals, and / or ferrous metals. Platinoid metals, for example platinum and / or palladium, have proven particularly suitable as noble metals. Palladium or a combination of palladium and platinum, optionally with the use of other active materials, is particularly advantageous.

[0020] In this case, the catalytic material is arranged on a base body. The base body advantageously has a large surface area; for example, the base body can be a honeycomb body, a porous body—such as a solid foam or foam structure—an arrangement of plates, in particular a structured plate bundle arranged along the gas flow direction, or the like. The base body is preferably formed in one piece; however, it is also possible for the base body to be constructed from several sub-bodies, wherein the sub-bodies can be connected and / or spatially separated. Typically, the base body is made of a ceramic, metallic ceramic—for example, cordierite—and / or a metal, in particular a special steel—for example, steel DIN / EN 1.4767.

[0021] It is conceivable that the catalytic material is arranged on a support material, with the base body being coated with the support material. It is also conceivable that the catalytic material is mixed with a support material, and the base body is coated with the mixture of catalytic material and support material. The support material is also referred to as a catalytic support material.

[0022] Typically, the support material comprises one or more metal oxides. The catalytic support material can contain, for example, titanium oxide, silicon oxide, aluminum oxide, and / or zirconium oxide, advantageously highly porous. It is also possible for the support material to comprise neodymium oxide, cerium oxide, praseodymium oxide, hafnium oxide, yttrium oxide, and / or rare earth elements, and mixtures and mixed oxides thereof. It is also conceivable for the support material to comprise molecular sieves such as zeolites.

[0023] The catalytic material is typically applied to the support material, advantageously in the form of nanoparticles. In particular, the catalytic material is applied to a support material already arranged on the base body. For example, the catalytic material can be applied by impregnation, in particular by dry impregnation and / or wet impregnation. The goal is to arrange a desired amount of the catalytic material at specific locations within the internal pore network of the support material and to fix it there in one or more subsequent steps. Fixing can be achieved, for example, by changing process parameters, by additives—in particular for changing pH values, by changing the oxidation state and / or the process temperature; drying, calcination, and / or reduction processes are particularly conceivable.For example, the support material can be an aqueous powder suspension of metal oxides, which is applied to the substrate. Such a powder suspension is also referred to as a washcoat. This powder suspension is then dried. The catalytic material, particularly metals in their aqueous acid solutions or salt solutions, can then be impregnated onto the support material and subsequently activated by calcination.

[0024] Furthermore, the catalyst can contain oxides of lanthanides and actinides as promoters and / or stabilizers, as well as oxides of alkaline earth metals and, for example, tin oxides and, in certain applications, alkali metal oxides.

[0025] The catalyst according to the invention can be a catalyst designed or configured for the oxidation of methane and / or hydrogen and optionally pollutants. However, it is also conceivable that the functions of oxidizing methane and / or hydrogen and optionally pollutants are fulfilled by a system of two or more catalysts for the oxidation of hydrogen and / or methane and optionally pollutant gases, wherein the catalysts of the system are each designed or configured for the oxidation of identical and / or different substances.

[0026] In addition to the catalyst according to the invention for the oxidation of methane and / or hydrogen, the system can, for example, contain further catalysts for the oxidation of pollutants. These further catalysts can also comprise the protective material. These further catalysts can, for example, also oxidize hydrogen and / or methane, at least temporarily and / or in small amounts.

[0027] Protective materials are understood to mean, in particular, substances or mixtures of substances designed to react with chromium and / or chromium compounds to form stable compounds. The protective material may, in particular, comprise alkaline earth metals—in particular magnesium, barium, and / or strontium—and / or alkaline earth metal compounds, in particular their oxides, and / or alkali metals and / or alkali metal compounds, in particular their oxides. The protective material may also comprise non-ferrous metals and / or non-ferrous metal compounds—in particular nickel oxides. Mixtures and / or mixed oxides of alkaline earth metals, alkaline earth metal compounds, non-ferrous metals, non-ferrous metal compounds, alkali metals, and / or alkali metal compounds are particularly conceivable.

[0028] The protective material can be applied to the catalyst, just like the catalytic material and optionally the support material, using the usual catalyst manufacturing processes familiar to experts. Processes for applying slurries to three-dimensional components with surfaces have proven particularly effective.

[0029] An electrochemical cell device or cell apparatus is understood to mean, in particular, a device designed for the electrochemical conversion of at least two fluids. The cell device comprises an electrochemical cell unit that electrochemically converts the two fluids, as well as components that electrically supply the cell unit, i.e., dissipate and / or supply electrical energy, and components that supply the cell unit with the two fluids. The supply can be active—for example, via supply lines, pumps, fluid reservoirs, etc.—or passive—for example, using ambient air as the fluid—without active transport. Advantageously, the cell device also comprises components for the removal and / or recycling of the converted fluids.Advantageously, the cell device also includes components for heat transport, in particular for temperature control of the cell unit, for example, for the utilization of waste heat. Examples of cell devices include fuel cell devices or electrolysis devices.

[0030] The catalyst according to the invention can be used at different fluid flow positions in the electrochemical cell device. The catalyst can be arranged upstream of the electrochemical cell unit. This has the advantage that the electrochemical cell unit can be protected from chromium or chromium compounds. For example, the catalyst can be used to pretreat the fluids before they are fed to the electrochemical cell unit. It is also possible for the catalyst to be arranged downstream of the electrochemical cell unit, allowing the fluids converted in the electrochemical cell to be post-treated and any chromium present there to be removed.

[0031] In this context, an electrochemical cell unit should be understood in particular as a unit with a plurality of electrochemical cells. An electrochemical cell unit is also referred to as an electrochemical stack or stack for short. Typically, the electrochemical cells are stacked on top of one another in a stack. Advantageously, a cell can have a plate-shaped carrier on which the functional layers, in particular electrolyte layers, are arranged, as well as a plate-shaped interconnector which has the elevations, wherein the interconnector is arranged between the carrier of the cell and another carrier of the adjacent cell. The interconnector establishes electrical contact between the adjacent cells. Furthermore, the interconnector creates a distance and thus a space through which flow can occur between the carrier of the cell and another carrier of the adjacent cell.This enables the supply of fluids to the supports or the functional layers arranged on them. Advantageously, the cells are electrically connected in series. It is also conceivable for the cells to be electrically connected in parallel. The cells can advantageously be arranged in a stack on a common chassis or support, or in a common housing. Examples of electrochemical cell units are fuel cell units or electrolysis cell units.

[0032] An electrochemical cell is understood in particular to be an arrangement which provides usable electrical energy through chemical reactions or is intended for the chemical extraction or conversion of substances by applying a voltage. An electrochemical cell has at least two or more functional layers. The functional layers comprise at least two electrode layers and a separating layer or electrolyte layer. The electrode layers each function as an electron conductor and are conductively connected to the separating layer or electrolyte layer. Also important for the electrode layers are ion transport and catalytic activity or oxygen exchange capacity between the electrode layer and the gas phase. The separating layer or electrolyte layer has in particular the function of an ion conductor. Furthermore, the separating layer orElectrolyte layer intended for the separation of the two gas spaces, for example the separation between air and fuel gas in a fuel cell.

[0033] In particular, a cell or electrochemical cell should be understood as a fuel cell or an electrolysis cell. In this context, a fuel cell or an electrolysis cell should be understood as at least one part, in particular a subassembly, of a fuel cell system, in particular a solid oxide fuel cell system, and / or an electrolysis cell device, in particular a high-temperature electrolyzer. In particular, the electrochemical cell can also comprise the entire fuel cell, in particular the entire solid oxide fuel cell, the entire electrolyzer, in particular the entire high-temperature electrolyzer, a stack of fuel cells and / or electrolysis cells, and / or a composite of several stacks of fuel cells and / or electrolysis cells.The electrochemical cell is preferably designed to convert a fuel into electrical energy by adding an oxidant in an electrochemical combustion process. Alternatively or additionally, the electrochemical cell is designed to divide a fluid into at least two components in a separation process by adding electrical energy. "Intended" is understood to mean, in particular, specially configured, specially designed, and / or specially equipped. The fact that an object is intended for a specific function is understood to mean, in particular, that the object fulfills and / or performs this specific function in at least one application and / or operating state.

[0034] The cell or electrochemical cell can in particular be an electrolysis cell, in particular a solid oxide electrolysis cell or solid oxide electrolysis cell (SOEC). Alternatively, the electrolysis cell can also be designed as a proton conductor electrolysis cell or protonic ceramic electrolysis cell (PCEC) based on a proton-conducting oxide or a proton-conducting oxide (PCO). The electrochemical cell can also be a fuel cell, for example a solid oxide fuel cell or solid oxide fuel cell (SOFC). It is also conceivable for the fuel cell to be designed in the manner of a proton conductor or proton-conducting oxide or a proton-conducting oxide (PCO). Such fuel cells are also referred to as protonic ceramic fuel cells (PCFC).A fuel cell is provided in particular for converting at least one chemical reaction energy of at least one, in particular continuously supplied, fuel gas, in particular hydrogen, and at least one oxidizing agent, in particular oxygen, in particular into electrical energy.

[0035] A fuel cell device is understood to mean, in particular, a device that forms a component, in particular a functional component, in particular a structural and / or functional component, of a fuel cell system or the entire fuel cell system. In this context, a fuel cell system is understood to mean, in particular, a system for stationary and / or mobile generation, in particular of electrical and / or thermal energy, using at least one fuel cell unit.

[0036] A fuel cell system comprises one or a plurality of fuel cell units. Typically, a fuel cell system comprises components and lines designed to supply fuel and air as fluids to the fuel cell unit. Furthermore, a fuel cell system comprises components and lines designed to discharge exhaust gases from the fuel cell units as fluids. Advantageously, a fuel cell system comprises a recirculation circuit comprising components and lines designed to return unconverted fuel and / or unconverted air to the fuel cell unit. Overall, a fuel cell system comprises at least one or a plurality of fans designed to convey a fluid, in particular a gaseous fluid. The fluid can in particular be a fuel, air, an exhaust gas, or a combination of the aforementioned.The fans can, in particular, be fans for an air supply, a fuel supply, a fan for an exhaust gas discharge, and / or a fan for a recirculation circuit. The fuel cell system advantageously has one or more heat exchangers, in particular to recirculate heat from the exhaust gas, or in particular from the anode exhaust gas and cathode exhaust gas, to the fuel cell unit, in particular to supply it to the fluids supplied to the fuel cell unit—in particular air, fuel, and / or recirculated fluid. The terms heat exchanger and heat transfer device are used synonymously herein.

[0037] In particular, SOFC fuel cell devices, i.e., fuel cell devices with a fuel cell unit containing SOFC fuel cells, are adversely affected by chromium; their performance decreases significantly due to the influence of chromium. This is sometimes referred to as chromium poisoning. Therefore, fuel cell devices in particular benefit from the catalyst according to the invention, especially when it is fluidically connected upstream of the fuel cell unit. For example, the catalyst can be used for reforming—in particular steam reforming—the fuel; it is also conceivable for the catalyst to be fluidically connected upstream and / or downstream of the reformer.It is also conceivable for the catalyst to be arranged downstream of the fuel cell unit in terms of flow and to be used, in particular, to treat the exhaust gases, so that chromium is removed from the anode exhaust gases, cathode exhaust gases, and / or the recirculated product. For example, the catalyst can be designed as an afterburner for the exhaust gases or can be arranged upstream and / or downstream of the afterburner in terms of flow.

[0038] The features listed in the subclaims enable advantageous further developments of the catalyst.

[0039] It is advantageous if the protective material contains at least one non-ferrous metal and / or a non-ferrous metal compound, in particular a nickel oxide. This enables particularly easy bonding of chromium or chromium compounds. It is further advantageous if the protective material contains at least one alkaline earth metal and / or an alkali metal or an alkaline earth metal compound and / or an alkali metal compound, in particular barium or a barium compound. This enables particularly efficient and reliable bonding of chromium or chromium compounds.

[0040] The catalyst is further improved if the catalyst has between 10 g and 250 g of active catalytic material per cubic foot of catalyst volume, preferably between 20 g and 150 g per cubic foot of catalyst volume, particularly preferably between 70 g and 100 g per cubic foot of catalyst volume. Chromium protection is determined by specific ratios between the active catalytic material and the protective material. Particularly good chromium protection can be achieved with the parameter ranges for the catalytic material specified here. The specification of grams (g) per cubic foot is historically determined and has become established for the quantification of catalyst material; it is therefore also used here for the catalytic material. One cubic foot corresponds to approximately 28.3 liters. For protective material, however, the SI unit gram (g) per liter is used.

[0041] In advantageous variants, the protective material is distributed largely homogeneously throughout the catalyst. In particular, the catalytic material can also be distributed homogeneously throughout the catalyst. This enables good chromium protection and simple catalyst production.

[0042] In variants, the protective material is arranged in an inflow section of the catalyst in an increased concentration; in particular, a majority of the protective material can be arranged in the inflow section. In particular, a lower concentration of active catalytic material can be arranged at the inflow section. This has the advantage that an inflowing fluid initially flows over a section with a high concentration of the protective material, so that a large amount of chromium can initially be removed from the fluid. In this way, the catalytic material arranged outside the inflow section or further away from the inflow section is more effectively protected from chromium. An inflow section is to be understood in particular as a section of the catalyst which is arranged at a connection or opening provided for the introduction of a fluid.Preferably, the inflow section has an extension which is less than 30% of a main extension of the catalyst or a maximum diameter of a catalyst volume through which flow can occur, preferably less than 20%, particularly preferably less than 10%.

[0043] A main amount is understood to mean an amount of the protective material which corresponds to at least 30% of the total amount of the protective material in the catalyst, preferably at least 40%, particularly preferably at least 50%.

[0044] In variants, different amounts of the protective material can be arranged at different positions in the catalyst. In particular, increased concentrations of the protective material can be present along intended main flow directions of the fluid.

[0045] In further embodiments, the catalytic material is concentrated in specific areas or sections; such areas or sections are also referred to as catalytically active centers or, in short, active centers. In variants, the protective material is arranged at the catalytically active centers. For example, it is conceivable for active centers and areas with protective material—in particular with high concentrations of protective material—to be arranged next to one another; it is advantageous for active centers arranged on a surface section to be surrounded by protective material on this surface. It is also conceivable for the protective material to be arranged on sections of the base body adjacent to the active centers, for example on mutually aligned surface sections of adjacent plates, channels, or honeycombs. Catalytically active centers can also be arranged on the protective materials.

[0046] Advantageously, the catalyst exclusively comprises surfaces that comprise a catalytic material and / or a protective material. It is advantageous if active centers with active catalytic material are arranged on the protective material. This enables particularly good chromium protection of the catalytic material. It is conceivable that the catalytic material is mixed with the protective material. It is conceivable that the catalytic material is arranged on and / or in a support material, and the protective material is arranged on and / or in this support material. In particular, it is conceivable that a mixture of the catalytic material and the protective material is arranged in and / or on the support material.

[0047] In further advantageous variants, the catalyst has a catalytic layer comprising catalytic material and optionally a carrier material, wherein a protective layer comprising protective material is arranged at least in sections on the catalytic layer. In this way, the catalytic layer is efficiently protected from chromium. It is conceivable that the catalytic layer is formed from catalytic material, or that the catalytic layer has a carrier material with the catalytic material. It is possible for the protective layer to be formed from the protective material; it is also possible for the protective layer to have a carrier material with the protective material. It is conceivable for the catalytic layer to have the same carrier material as the protective layer; it is also conceivable for the catalytic layer and the protective layer to each have different carrier materials.

[0048] The protective layer can be formed as one layer or several layers in the diffusion direction and / or flow direction of the fluid or process gas.

[0049] In advantageous variants, the catalyst has a catalytic layer comprising catalytic material and optionally a carrier material, wherein and below the catalytic layer at least in sections a protective layer comprising protective material is arranged. This has the advantage if chromium can diffuse from the base body, for example because the latter is made of stainless steel or comprises stainless steel. The fact that the protective layer is arranged below the catalytic layer should be understood in particular to mean that the protective layer is arranged between the base body and the catalytic layer. In particular, variants are also conceivable in which a protective layer is arranged below and above a catalytic layer. Alternating layer systems are also conceivable in which catalytic layers and protective layers alternate.

[0050] A catalyst with a plurality of plates extending along a flow direction of the catalyst and comprising at least some sections of the catalytic material and / or the protective material is advantageous. This allows for the provision of the largest possible surface area per catalyst volume.

[0051] In particular, the base body can comprise the plates. It is also possible for the plates to form the base body. The plates can be coated with at least one carrier material and / or with the catalytic material—in particular a catalytic layer—and / or with the protective material—in particular a protective layer.

[0052] In further variants, the catalyst comprises a honeycomb body, wherein the honeycomb body has a plurality of channels which extend along a flow direction of the catalyst and which at least partially comprise the catalytic material and / or the protective material. In this way, too, a large surface area can be provided, thus enabling a high catalytic performance per catalyst volume. In particular, the base body can comprise the honeycomb body. It is also possible for the honeycomb body to form the base body. The plates can be coated with at least one carrier material and / or with the catalytic material—in particular a catalytic layer—and / or with the protective material—in particular a protective layer.

[0053] It is advantageous if the catalyst comprises a hydrogen oxidation catalyst. In this way, the hydrogen can be oxidized particularly well. The fact that the catalyst comprises a hydrogen oxidation catalyst should be understood in particular to mean that the catalyst comprises a catalytic material that is suitable or intended for hydrogen oxidation. A hydrogen oxidation catalyst is advantageously designed to specifically oxidize hydrogen to a high degree—preferably almost completely. The hydrogen oxidation catalyst is typically not designed to oxidize significant amounts of methane. It is possible that other fluids, such as carbon monoxide, are also oxidized to a certain extent in the hydrogen oxidation catalyst, possibly up to almost complete conversion.For example, a hydrogen oxidation catalyst can be operated at temperatures between 550 °C and 680 °C, preferably between 620 °C and 650 °C.

[0054] It is also advantageous if the catalyst comprises a methane oxidation catalyst (MOC). A methane oxidation catalyst is also referred to as methane oxidation catalyst, or MOC for short. In this way, the methane can be oxidized particularly well. The fact that the catalyst comprises an MOC should be understood in particular that the catalyst comprises a catalytic material that is suitable or intended for methane oxidation. An MOC is advantageously designed to specifically oxidize methane to a high degree – advantageously almost completely. The MOC is typically not designed to completely oxidize carbon monoxide. In particular, carbon monoxide can be produced during the oxidation of methane. An MOC can, for example, be operated at temperatures between 550°C and 780°C, preferably between 600°C and 650°C.

[0055] The catalyst advantageously has a catalytic afterburner. This enables particularly good oxidation of hydrogen and methane as well as carbon monoxide and / or hydrocarbons. A catalytic afterburner, or afterburner for short, is also referred to as a (catalytic) tail gas burner (TGB). A catalytic afterburner can, in particular, oxidize a variety of substances. It is conceivable for the afterburner to have different spatial areas for the oxidation of different substances; in particular, the different areas can have different types, compositions, and / or concentrations of catalytic material. An afterburner is typically operated at temperatures between 150°C and 600°C, preferably between 180°C and 350°C, particularly preferably between 230°C and 250°C.Another advantage is an electrochemical cell device, in particular a fuel cell device, comprising an electrochemical cell unit and at least one catalyst according to one of the preceding claims. This has the advantage that the electrochemical cell device can be operated with very low chromium emissions, advantageously with virtually no chromium emissions. Furthermore, such an electrochemical cell device can be operated for long periods of time without a drop in efficiency or performance. Compared to prior art electrochemical cell devices, operation is more reliable, and replacement of the catalyst or the electrochemical cell unit is significantly less frequent or even unnecessary.

[0056] A system comprising at least two catalysts is also advantageous, in particular for use in electrochemical cell devices, preferably fuel cell devices, wherein the at least two catalysts are connected in series in terms of flow technology, wherein the at least two catalysts each have an active catalytic material which is each arranged on a base body and wherein at least one first catalyst arranged first in the flow direction has a protective material which is intended to bind chromium and is arranged on the base body, wherein the first catalyst is intended for the oxidation of hydrogen and a second catalyst arranged downstream of the first catalyst in the flow direction is intended for the oxidation of methane.This has the advantage that by using at least two catalysts, one can be designed for the oxidation of hydrogen and the other for the oxidation of methane, allowing these substances to be oxidized particularly efficiently. The second catalyst is protected from chromium by the protective material of the first catalyst. It is also conceivable for the second catalyst and optionally additional catalysts to contain the protective material or a different protective material.

[0057] The first catalyst can, for example, comprise a hydrogen oxidation catalyst or be designed as a hydrogen oxidation catalyst. Advantageously, the first catalyst is designed to specifically oxidize hydrogen to a high degree—preferably almost completely. For this purpose, the first catalyst comprises catalytic material intended for this purpose. The first catalyst is typically not designed to oxidize methane or large amounts of methane. It is possible that other fluids, such as carbon monoxide, are also oxidized to a certain extent in the first catalyst, possibly to almost complete conversion. The first catalyst can, for example, be operated at temperatures between 550°C and 680°C, preferably between 620°C and 650°C.

[0058] The second catalyst can comprise a MOC or be designed as an MOC. An MOC is advantageously designed to specifically oxidize methane to a high degree—advantageously almost completely. For this purpose, the second catalyst comprises catalytic material intended for this purpose. The second catalyst is typically not designed to completely oxidize carbon monoxide. In particular, carbon monoxide can be formed during the oxidation of methane. The second catalyst can be operated, for example, at temperatures between 550°C and 780°C, preferably between 600°C and 650°C.

[0059] For example, it is possible that due to unfavorable concentration ratios of process gas, oxygen and / or harmful gases or corresponding mass flows and / or flow velocities of these fluids, in particular due to an unfavorable distribution of these fluids across the cross-section of the catalyst, an amount of heat is released as the hydrogen oxidizes as it flows through the catalyst, which heats the catalyst to such an extent that the resulting temperature inside the catalyst during continuous operation has a negative effect on one or more reactions for the oxidation of methane and / or one or more harmful gases to be oxidized, so that methane and / or these harmful gases are not oxidized to the desired extent. Such a decreasing activity of a reaction to be catalyzed with increasing operating time of the catalyst is also referred to as degradation.

[0060] With the present system comprising at least two catalysts, such degradation can be reduced or prevented, since the catalysis of hydrogen and methane is distributed among the at least two catalysts, and in particular, the transfer of heat generated during each catalysis to the other catalyst is easier to prevent. The different catalysis processes for hydrogen and methane, and optionally for other substances, can be decoupled from one another in this way. Advantageously, the at least two catalysts are operated at specifically designed, different inlet temperatures.

[0061] To mitigate the disadvantages of such a multi-stage process, particularly its space requirements and the resulting gas backpressure, the catalysts can optionally be combined in a single component, in which case thermal decoupling measures should advantageously be applied. In such catalysts, the respective catalytic materials can be arranged in as homogeneous a distribution as possible or—particularly for thermal decoupling—in a deliberately uneven distribution in the direction of fluid flow.

[0062] The system is further improved by a third catalyst, which is connected in series with the first catalyst and second catalyst in terms of flow and is arranged downstream of the second catalyst in the direction of flow, whereby the third catalyst is intended for the oxidation of carbon monoxide, or carbon monoxide for short. This further decouples the different catalytic processes, and the efficiency and durability or resistance to degradation of the system is further increased. The third catalyst can advantageously comprise protective material. The at least three catalysts are advantageously operated at specifically designed, each different inlet temperatures. The third catalyst can, for example, be a catalytic afterburner or the third catalyst can comprise a catalytic afterburner.

[0063] It is further advantageous if a cooling device is arranged between at least two catalysts, fluidically connecting the two catalysts and providing cooling for the fluid flowing from one catalyst into the other. This allows for more precise adjustment of the temperature required or preferred for the respective catalytic process. Furthermore, thermal decoupling can be further increased in this way. This makes the system even more efficient and durable, and degradation is further prevented. Preferably, a cooling device is arranged fluidically between the first catalyst and the second catalyst, and a further cooling device is arranged between the second catalyst and the third catalyst.

[0064] A cooling device is provided, in particular, to lower the inlet temperature of the gas flowing downstream of the catalyst in the flow direction. The cooling device can, in particular, comprise a heat exchanger, but other types of fluid temperature change are also conceivable, for example, gas cooling and / or the addition or admixture of another, cooler gas. Other active cooling methods are also conceivable, for example, thermoelectric cooling with a Peltier element.

[0065] It is further advantageous if at least two of the catalysts, preferably three catalysts, are arranged spatially separated from each other. This allows for particularly simple and efficient thermal decoupling, and passive cooling measures for the individual catalysts are also very easy to implement. This further minimizes degradation.

[0066] It is conceivable that the separate catalysts are arranged or formed on a base body and are each arranged in separate regions with different concentrations and / or amounts of catalytic material—particularly in the form of active centers. In variants, these regions can also interlock, merge, and / or partially overlap. This has the advantage of providing a compact system.

[0067] To minimize degradation, it is advantageous if the separate catalysts are arranged on several separate base bodies. The separate catalysts advantageously have their own housings and are structurally connected to one another, preferably only by lines that fluidically connect the catalysts. This has the additional advantage that different base bodies allow for different features or properties, such as different inflow surfaces, for example, due to different shapes or diameters. Different materials, a different cell structure of the base body - especially a honeycomb body - and / or wall thicknesses are also conceivable. This enables optimization of the inflow in the sense of the most targeted, usually evenly distributed inflow.Furthermore, this method makes it possible to influence the backpressure of the fluid flowing through the respective catalyst. This advantageously allows for the lowest possible resulting total backpressure of the system. However, optimization is also possible with regard to the thermomechanical stability of the base body due to the different energies released by oxidation.

[0068] It is further advantageous if at least one of the catalysts has at least two parallel fluid flows. In this way, the total gas backpressure or total flow resistance through the system can be optimized or reduced for a given catalyst volume.

[0069] It is conceivable for a catalyst to have at least two parallel fluid flows internally. However, it is also conceivable for the catalyst to be constructed in multiple parts, in particular having separate base bodies and / or housings that are fluidically connected in parallel via lines.

[0070] If at least the first catalyst has between 30 g and 200 g of protective material per liter of catalyst volume, preferably between 40 g and 150 g per liter of catalyst volume, particularly preferably between 50 g and 100 g per liter of catalyst volume, this has the advantage that the accumulation of chromium or chromium compounds, in particular chromium(VI) oxide, in the catalyst can be prevented in this way, so that the oxidation rate of methane and / or hydrogen does not drop as quickly as in a catalyst without the chromium protection according to the invention. In particular, the operating time of the catalyst until a replacement due to chromium accumulation can be extended in this way, or such a replacement can be prevented entirely. The protective material in the first catalyst also protects the catalysts fluidically arranged downstream of the first catalyst, in particular the second catalyst and the optional third catalyst.Advantageously, the second catalyst and / or the third catalyst also comprise protective material.

[0071] It is further advantageous if the protective material contains at least one non-ferrous metal and / or a non-ferrous metal compound, in particular nickel oxide. This enables particularly easy bonding of chromium or chromium compounds.

[0072] It is advantageous if the protective material contains at least one alkaline earth metal and / or one alkali metal or alkaline earth metal compound and / or alkali metal compound, in particular barium or a barium compound. This enables particularly efficient and reliable binding of chromium or chromium compounds.

[0073] The system is further improved if at least one of the catalysts contains between 10 g and 250 g of active catalytic material per cubic foot of catalyst volume, preferably between 20 g and 150 g per cubic foot of catalyst volume, more preferably between 70 g and 100 g per cubic foot of catalyst volume. Chromium protection is determined by specific ratios between the active catalytic material and the protective material. Particularly good chromium protection can be achieved with the parameter ranges for the catalytic material specified here.

[0074] Also advantageous is an electrochemical cell device, in particular a fuel cell device, comprising an electrochemical cell unit and at least one system according to the present invention. In addition to the described advantages of the catalyst according to the present invention, the use of the system offers the additional advantage of achieving extreme degradation resistance of the catalysts. This makes the system extremely durable and reliable, and maintenance and replacement of the catalysts can sometimes even be avoided entirely. Drawings

[0075] The drawings show exemplary embodiments of the catalyst and an electrochemical cell device and are explained in more detail in the following description.

[0076] Figure 1 is a schematic representation of the fluidic circuitry of an electrochemical cell device,

[0077] Figures 2 to 4 are schematic representations of variants of the catalyst and

[0078] Figure 5 shows a system of three catalysts.

[0079] Description

[0080] In the different versions, identical parts have the same reference numbers.

[0081] Figure 1 shows a schematic circuit diagram of an electrochemical cell device 10. By way of example, the electrochemical cell device 10 is a fuel cell device 10. In the illustrated embodiment, the fuel cell device 10 is designed as a fuel cell device 10 for dual-fuel operation, which can be operated with hydrogen, natural gas, or a mixture of both. It has two fuel sources 14, one for hydrogen and one for natural gas, which can be used alone or in combination. The fuel cell device 10 comprises a fuel cell unit 12, which is designed, by way of example, as an SOFC fuel cell stack.

[0082] A first fuel, in the case shown hydrogen, is supplied from a first fuel source 14a via a first fuel supply line 16a to the fuel cell unit 12 or its anode side 12b. More precisely, the first fuel is supplied to an anode side 12b of the fuel cell unit 12. For example, the first fuel source 14a is a gas connection for an external fuel supply line which provides hydrogen. For example, a first mass flow controller 46a for the first fuel is connected directly downstream of the first fuel source 14a in the flow direction of the first fuel in the first fuel supply line 16a. In this way, the fuel flow required for the operation of the fuel cell unit 12 can be adjusted.

[0083] In addition, the fuel cell device has a second fuel source 14b. A second fuel, in the illustrated case natural gas, is supplied from the second fuel source 14b via a second fuel supply line 16b to the fuel cell unit 12 or its anode side 12b. More precisely, the second fuel is supplied to an anode side 12b of the fuel cell unit 12. For example, the second fuel source 14b is a gas connection for an external fuel supply line, which provides natural gas. For example, a second mass flow controller 46b for the second fuel is connected directly downstream of the second fuel source 14b in the flow direction of the second fuel in the second fuel supply line 16b. In this way, the fuel flow required for the operation of the fuel cell unit 12 can be adjusted.By making the appropriate adjustments to the first mass flow controller 46a and the second mass flow controller 46b, the mixture of first fuel and second fuel supplied to the fuel cell unit 12 can be adjusted.

[0084] The first fuel supply line 16a and the second fuel supply line 16b are fluidly connected at a first mixing section 40a. The first fuel and the second fuel mix at the first mixing section 40a. From the first mixing section 40a onward, the first fuel supply line 16a and the second fuel supply line 16b combine to form a common fuel supply line 16, which carries the mixture of the two fuels to the fuel cell unit 12. The first mixing section 40a is arranged in the recirculation circuit 36. The exact position of the first mixing section 40a relative to the other components is shown below.

[0085] A reformer 64 is arranged on the fuel supply line 16. The reformer 64 is provided for reforming the fuel, in particular the second fuel, in particular the natural gas. In this way, the fuel—in particular the second fuel, preferably the natural gas—is converted in the reformer 64 into an at least partially reformed fuel. The reformer 64 is required in particular in operating states in which natural gas or predominantly natural gas is fed to the fuel cell unit 12 as the fuel. In the exemplary embodiment, the reformer 64 is arranged in the common fuel supply line 16, in terms of flow, directly upstream of the fuel cell unit 12.

[0086] Air is supplied to the fuel cell unit 12 from an air source 18 via an air supply line 20. More precisely, the air is supplied to a cathode side 12a of the fuel cell unit 12. For example, an air blower 48 is arranged on the air supply line 20, fluidically between the air source 18 and the fuel cell unit 12. The air blower 48 is intended to supply air to the fuel cell unit 12 or its cathode side 12a. Advantageously, the air blower 48 is controllable or adjustable in terms of air flow strength. In this way, the air flow required for the operation of the fuel cell unit 12 can be adjusted. In the exemplary embodiment, the air source 18 is designed as an opening for outside air, which has an air filter. The air filter is intended to filter out pollutants and / or impurities from the air.

[0087] In the fuel cell unit 12, the fuel or reformed fuel is electrochemically converted with the aid of oxygen from the air, generating electrical energy and heat. The electrical energy is absorbed and converted, for example, by power electronics 22 connected to the fuel cell unit 12. For example, the direct current of the fuel cell unit 12 can be converted into an alternating voltage for external use. The power electronics 22 is not shown in Figure 1 for clarity.

[0088] After the electrochemical conversion in the fuel cell unit 12, the exhaust gas or cathode exhaust gas generated on the cathode side 12a is discharged from the fuel cell unit 12 via a cathode exhaust line 24a. The exhaust gas or anode exhaust gas generated on the anode side 12b is discharged from the fuel cell unit 12 via an anode exhaust line 24b.

[0089] The anode exhaust gas may contain unreacted fuel as well as unreformed fuel.

[0090] The cathode exhaust gas is conducted from the fuel cell unit 12 to an afterburner 26 via the cathode exhaust gas line 24a. A portion of the anode exhaust gas is conducted from the fuel cell unit 12 to the afterburner 26 via the anode exhaust gas line 24b. The anode exhaust gas line 24b has a flow splitter 34, which divides the portion of the anode exhaust gas line 24b fluidically connected to the fuel cell unit 12 into a second portion of the anode exhaust gas line 24b and a recirculation line 36. The anode exhaust gas flowing from the anode side 12b is divided at the flow divider 34 into a first partial flow, which is fed to the afterburner 26 via the anode exhaust gas line 24b, and a second partial flow, which is fed to a recirculation circuit 38 via the recirculation line 36.

[0091] By means of the afterburner 26, the anode exhaust gas or any unreacted and / or unreformed fuel contained therein is converted with the admixture of the cathode exhaust gas or the oxygen in the air contained therein, whereby additional heat can be generated. The afterburner 26 is a catalyst 100 for the oxidation of methane and hydrogen. By way of example, the catalyst 100 is designed as a catalytic afterburner 26. The catalyst has a protective material 110 (see Figure 2), which is intended to bind the chromium from the anode exhaust gas and cathode exhaust gas. The exhaust gases from the afterburner 26 are conducted via an exhaust line 28 into an exhaust outlet 30. The exhaust gases are conducted out of the fuel cell device 10 through the exhaust outlet 30.

[0092] Advantageously, the waste heat from the exhaust gases of the fuel cell unit 12, in particular the cathode exhaust gas and the anode exhaust gas or the exhaust gas from the afterburner, is returned to the fuel cell unit 12. In the exemplary embodiment, the fuel cell device 10 has a cathode heat exchanger 32a. The cathode heat exchanger 32a is provided to transfer heat from the exhaust gases flowing from the fuel cell unit 12 or the afterburner 26 to the air, which is supplied to the fuel cell unit 12 or its cathode side 12a via the air supply line 20. In this way, the efficiency of the fuel cell device 10 can be increased. In the exemplary embodiment, the cathode heat exchanger 32a is arranged upstream of the fuel cell unit 12 on the air supply line 20, relative to the direction of air flow.Advantageously, the cathode heat exchanger 32a is arranged downstream of the air blower 48 on the air supply line 20, relative to the direction of air flow. In the exemplary embodiment, the cathode heat exchanger 32a is arranged downstream of the afterburner 26 on the exhaust line 28, relative to the direction of exhaust gas flow.

[0093] In particular, the afterburner 26 is fluidly connected to the cathode heat exchanger 32a via the exhaust line 28. For example, in the exemplary embodiment shown in Figure 1, a controllable air bypass line 66 is arranged on the air line 20, which is intended to direct an adjustable portion of the air flow past the cathode heat exchanger 32a. In this way, in particular, the temperature of the air arriving at the fuel cell unit 12 can be adjusted.

[0094] In the exemplary embodiment, the fuel cell device 10 has an anode heat exchanger 32b. The anode heat exchanger 32b is provided to transfer heat from the anode exhaust gases flowing from the fuel cell unit 12 or its anode side 12b to the fuel, which is supplied to the fuel cell unit 12 or its anode side 12b via the fuel supply line 16. In this way, the efficiency of the fuel cell device 10 can be further increased. In the exemplary embodiment, the anode heat exchanger 32b is arranged upstream of the fuel cell unit 12 on the fuel supply line 16, relative to the flow direction of the fuel. In the exemplary embodiment, the anode heat exchanger 32b is arranged downstream of the fuel cell unit 12 and downstream of the flow divider 34, relative to the flow direction of the anode exhaust gas, on the recirculation line 36.In particular, the flow divider 34 is fluidly connected to the anode heat exchanger 32b via the recirculation line 36.

[0095] In the present exemplary embodiment, the fuel cell device has a secondary anode heat exchanger 32c. The secondary anode heat exchanger 32c is provided to transfer heat from the cathode exhaust gases flowing from the fuel cell unit 12 or its cathode side 12b, or the exhaust gases of the afterburner 26, to the fuel, which is supplied to the fuel cell unit 12 or its anode side 12b via the fuel supply line 16. In this way, the efficiency of the fuel cell device 10 can be further increased. In the exemplary embodiment, the secondary anode heat exchanger 32c is arranged fluidically upstream of the fuel cell unit 12 and downstream of the (primary) anode heat exchanger 32b, with respect to the flow direction of the fuel on the fuel supply line 16.In the exemplary embodiment, the anode heat exchanger 32b is arranged fluidically downstream of the afterburner 26 and upstream of the cathode heat exchanger 32a in relation to the flow direction of the exhaust gas of the afterburner on the exhaust line 28.

[0096] In the exemplary embodiment, the recirculation circuit 38 is provided to recirculate a portion of the anode exhaust gases from the anode side 12b of the fuel cell unit 12. The recirculation circuit 38 has a second mixing section 40b, in which the recirculate is fed into the second fuel supply line 16b, where the recirculate is mixed with fresh second fuel. At the second mixing section 40b, the second fuel supply line 16b and the recirculation line 36 are fluidically connected to one another. In the exemplary embodiment shown in Figure 1, the second mixing section 40b is arranged with respect to the flow direction of the second fuel orThe second fuel mixed with the recirculate is arranged on the second fuel supply line 16b fluidically downstream of the second fuel source 14b and upstream of the fuel cell unit 12, for example upstream of the first mixing section 40a, at which the first fuel supply line 16a is fluidically connected to the second fuel supply line 16b. The first mixing section 40a is fluidically arranged directly upstream of the (primary) anode heat exchanger 32a with respect to the flow direction of the second fuel or a mixture of first fuel, second fuel, and recirculate.

[0097] In the exemplary embodiment shown in Figure 1, the recirculation fan 42 is arranged on the second fuel supply line 16b. With respect to the flow direction of the second fuel or the second fuel mixed with the recirculated material in the second fuel supply line 16b, the recirculation fan 42 is arranged, for example, downstream of the second mixing section 40b and upstream of the first mixing section 40a.

[0098] By way of example, the condenser heat exchanger 50 is arranged on the second fuel supply line 16b. In the exemplary embodiment, the condenser heat exchanger 50 is arranged downstream of the recirculation fan 42 and upstream of the first mixing section 40a with respect to the flow direction of the second fuel or the second fuel mixed with the recirculate. In this way, during operation, the recirculate mixed with the second fuel first flows through the condenser heat exchanger 50, where the water vapor is at least partially condensed. The recirculate then flows through the first mixing section 40a, where a fresh first fuel—in this case, hydrogen—is added to the mixture of recirculate and second fuel—in this case, natural gas.In the exemplary embodiment shown in Figure 1, it is provided that the recirculate in the condenser heat exchanger 50 is cooled by air which is provided by a secondary air supply which is independent of the primary air supply via the air source 18. By way of example, the fuel cell device 10 has a secondary air source 18b. The secondary air source 18b is fluidically connected to the condenser heat exchanger 50 via a secondary air supply line 20b. The secondary air source 18b is designed, for example, as an opening for outside air which has an air filter. The air is led out of the condenser heat exchanger 50 and out of the fuel cell device 10 via an air discharge line 68. A secondary

[0099] Air blower 48b is arranged. In terms of flow, the secondary air blower 48b is arranged between the secondary air source 18b and the

[0100] Condenser heat exchanger 50 is arranged. Advantageously, the secondary air blower 48b is controllable or adjustable in air flow intensity.

[0101] The adjustable secondary air blower 48b allows, in particular, the air flow through the condenser heat exchanger 50 to be adjusted, so that, in particular, the cooling capacity or the heat extracted from the recirculated material can be adjusted. In particular, a condensation temperature can be adjusted in this way using the secondary air blower.

[0102] In the exemplary embodiment shown in Figure 1, a condensate drain 58 is connected to the condenser heat exchanger 50, which is intended to drain the condensate from the condenser heat exchanger 50. For example, the condensate drain 58 fluidically connects the condenser heat exchanger 50 to a condensate drain 60.

[0103] Figure 2 shows a schematic side view of the catalyst 100. For example, the catalyst has a plurality of plates 104 as the base body 102, which extend along a flow direction of the catalyst 100. In Figure 2, the flow direction runs from left to right.

[0104] Between each two adjacent plates 104 there is a flow chamber 106 through which a fluid or process gas flows during operation. The plates 104 are each coated on both sides with a catalytic material 108 and a protective material 110. In this way, a gas flowing through the flow chamber 106 comes into contact with the catalytic material 108 and the protective material 110. By way of example, the catalyst 110 has twenty parallel, coated plates 104; in other further embodiments, the catalyst has between 50 and 500 plates 110, preferably between 100 and 400 plates 110, particularly preferably between 200 and 300 plates 110. In variants, the base body 102 can have a honeycomb structure or honeycomb body made up of channels aligned parallel to the gas flow direction. For example, the honeycomb structure can have 40 to 800 cells orHoneycombs per square inch of frontal area, preferably between 100 and 600 cells per square inch of frontal area, particularly preferably between 300 and 400 cells per square inch of frontal area.

[0105] Figure 3 shows a detailed view of one side of a plate with a coating. A catalytic layer 112, which comprises a carrier material 114 and the catalytic material 108, is arranged on the surface of the plate 104. A protective layer 116, which comprises the protective material 110, is arranged on the catalytic layer 112. For example, the catalytic layer 112 comprises a ceramic carrier material 114. The catalytic material 108 is arranged in active centers and consists, for example, of bimetallic noble metal nanoparticles, in the exemplary embodiment, of core-shell-shaped platinum particles and palladium particles. The catalytic layer 112 comprises, for example, 120 g of catalytic material per cubic foot of catalyst volume; in variants, 180 or 200 g of catalytic material per cubic foot of catalyst volume are also conceivable.

[0106] In advantageous variants of the catalytic material 108, the palladium content predominates over the platinum content, exceeding it by, for example, fivefold, eightfold, twelvefold, or twentyfold. A catalytic material 108 with almost pure palladium and only a few dozen or a few hundred ppm of platinum is also conceivable. If the total amount of precious metal or the catalytic material 108 is reduced below a threshold of 70 g of catalytic material 108 per cubic foot of catalyst volume, the catalyst volume of the catalyst 100 according to the invention can be increased. This results in an application-specific optimum between catalytic performance at the end of the desired operating time, the available space for accommodating the catalyst 100, the desired gas backpressure, and the overall effort required to construct and operate the catalyst.

[0107] The protective material 110 comprises non-ferrous metals and alkaline earth metals, for example nickel, strontium and barium. In the exemplary embodiment, the catalyst 100 comprises, for example, 120 g of protective material 110 per liter of catalyst volume. The protective material 110 is advantageously arranged in an inflow section with an increased concentration. The concentration of catalytic material 108 in the inflow section is advantageously reduced, for example 1 to 15 g per cubic foot of catalyst volume, preferably between 2 and 10 g per cubic foot of catalyst volume, particularly preferably between 3 and 5 g per cubic foot of catalyst volume. Overall, the catalyst comprises, for example, A catalyst typically has 50 g to 225 g of total coating per liter of catalyst volume, wherein the total coating comprises the catalytic material 108, the protective material 110 and the support material 114.

[0108] For example, the process gas can contain between 50 ppm and 500 ppm, preferably between 100 ppm and 250 ppm of methane, as well as water vapor, nitrogen, CO2 and other harmful gases, between 0.1% and 2.0% hydrogen, between 0.001% and 0.500% CO and 5% to 20% O2, as well as traces of chromium(VI) oxide, whereby the % data refers to the amount of substance. Before entering the catalyst 100, the process gas has a temperature between 550 °C and 750 °C, preferably between 620 °C and 650 °C. As it flows through the catalyst 100, the methane is oxidized with the oxygen to water vapor and carbon dioxide, or in the balance one molecule of CH4 and two molecules of O2 are converted into two molecules of H2O and one molecule of CO2. The harmful gases are also oxidized and the chromium(VI) oxide is bound to the protective material 110.From the catalyst 100, in particular in a catalytic afterburner 26, flows a product stream with at most less than 100 ppm of hydrogen, carbon monoxide and methane, advantageously less than 10 ppm and particularly advantageously less than 5 ppm.

[0109] Figure 4 shows a variant in which the plate 104 of the base body 102 is coated with a ceramic carrier material 114 which comprises the catalytic material 108 and the protective material 110, wherein the catalytic material 108 and the protective material 110 are mixed and evenly distributed in the carrier material 114.

[0110] Figure 5 shows a schematic representation of a system 120 comprising three catalysts 110. The three catalysts 100 are connected in series in terms of flow. A first catalyst 100a is followed in the flow direction by a second catalyst 100b, followed by a third catalyst 100c.

[0111] The first catalyst 100a is intended in particular for the oxidation of hydrogen, the second catalyst 100b is intended in particular for the oxidation of methane and the third catalyst 100c is intended in particular for the oxidation of carbon monoxide.

[0112] The first catalyst 100a comprises, for example, a honeycomb body as a base body 102 with channels formed by cells or honeycombs aligned along the gas flow direction. The honeycomb body contains, for example, 40 to 400 cells or honeycombs per square inch of front area. The first catalyst 100a comprises catalytic material 108 arranged in active centers, for example, between 10 and 20 g of palladium nanoparticles per cubic foot of catalyst volume on 150 to 200 g of support material 114 per liter of catalyst volume. The support material 114 of the first catalyst 100a is, for example, Al2O3 and / or SiO2. Furthermore, the first catalyst 100a comprises, for example, 50 g of protective material 110 per liter of catalyst volume, wherein the protective material 110 contains nickel, stroma, and / or barium.For example, the temperature of the gas mixture before entering the first catalyst 100a is up to 680 °C, but usually not less than 550 °C and not more than 650 °C, in particular 620 °C. The gas mixture flows through the first catalyst 100a at a space velocity of up to 550,000 per hour, for example at 250,000 per hour.

[0113] The second catalyst 100b has, as its base body 102, a honeycomb structure composed of 300 to 400 honeycombs or cells per square inch. The honeycombs form channels extending along the gas flow direction. The catalytic material 108 coating the honeycomb structure has active centers formed, for example, by 150 to 250 g of palladium nanoparticles per cubic foot of catalyst volume on 150 to 200 g of support material 114 per liter of catalyst volume. The support material 114 of the second catalyst 100b is, for example, Al2O3 and / or La2O3. For example, the second catalyst 100b is flowed through at a space velocity of 10,000 to 250,000 per hour, preferably at no more than 100,000 per hour, for example, 60,000 per hour. The inlet temperature is at least 550 °C, preferably between 600 °C and 650 °C, but not more than 780 °C.Advantageously, a first cooling device 118a is arranged fluidically between the first catalyst 100a and the second catalyst 100b, which cooling device is intended to cool the fluid flowing from the first catalyst 100a into the second catalyst 100b.

[0114] The third catalyst 100c comprises, for example, a honeycomb body as the base body 102 with channels formed by cells or honeycombs aligned along the gas flow direction. The honeycomb body contains, for example, 80 to 400 cells or honeycombs per square inch of front surface of the base body 102. The third catalyst 100c comprises catalytic material 108 arranged in active centers, for example, between 20 and 60 g of platinum per cubic foot of catalyst volume on 150 to 200 g of support material 114 per liter of catalyst volume. The support material 114 of the third catalyst 100c is, for example, Al2O3 and / or SnO2. Furthermore, the third catalyst 100c comprises, for example, 40 g of protective material 110 per liter of catalyst volume, wherein the protective material 110 contains alkaline earth metals and / or alkali metals and / or a zeolite. The gas mixture flows through the third catalyst 100c at a space velocity of 100,000 to 550, for example.000 per hour, preferably no more than 200,000 per hour, for example 120,000 per hour. The third catalyst 100c is, for example, a catalytic afterburner 24 and is operated at an inlet temperature of 180°C to 350°C, preferably no less than 250°C, for example at 230°C. Therefore, in the present exemplary embodiment of the system 120, it is absolutely necessary to significantly cool the fluid flowing out of the second catalyst 100b before it is fed into the third catalyst 100c. Therefore, a second cooling device 118b is advantageously arranged fluidically between the second catalyst 100b and the third catalyst 100c, which second cooling device is intended to cool the fluid flowing from the second catalyst 100b into the third catalyst 100c.

Claims

Claims 1 . Catalyst (100) for the oxidation of methane and / or hydrogen, in particular for use in electrochemical cell devices (10), preferably fuel cell devices (10), wherein the catalyst (100) comprises an active catalytic material (108) and a protective material (110) which is provided for binding chromium, wherein the catalytic material (108) and the protective material (110) are arranged on a base body (102), characterized in that the catalyst (100) has between 30 g and 200 g of protective material (110) per liter of catalyst volume, preferably between 40 g and 150 g per liter of catalyst volume, particularly preferably between 50 g and 100 g per liter of catalyst volume.

2. Catalyst (100) according to claim 1, characterized in that the protective material (110) comprises at least one non-ferrous metal and / or one non-ferrous metal compound, in particular a nickel oxide.

3. Catalyst (100) according to one of the preceding claims, characterized in that the protective material (110) comprises at least one alkaline earth metal and / or an alkali metal or an alkaline earth metal compound and / or alkali metal compound, in particular barium or a barium compound.

4. Catalyst (100) according to one of the preceding claims, characterized in that the catalyst (100) has between 10 g and 250 g of active catalytic material (108) per cubic foot of catalyst volume, preferably between 20 g and 150 g per cubic foot of catalyst volume, particularly preferably between 70 g and 100 g per cubic foot of catalyst volume.

5. Catalyst (100) according to one of the preceding claims, characterized in that the protective material (110) is distributed largely homogeneously in the catalyst (100).

6. Catalyst (100) according to one of claims 1 to 4, characterized in that the protective material (110) is arranged in an inflow section of the catalyst (100) in an increased concentration, in particular that a major amount of the protective material (110) is arranged in the inflow section.

7. Catalyst (100) according to one of the preceding claims, characterized in that active centers with active catalytic material (108) are arranged on the protective material (110).

8. Catalyst (100) according to one of the preceding claims, characterized in that the catalyst (100) has a catalytic layer (112) comprising catalytic material (108) and optionally a carrier material (114), and a protective layer (116) comprising protective material (110) is arranged at least in sections on the catalytic layer (112).

9. Catalyst (100) according to one of the preceding claims, characterized in that the catalyst (100) has a catalytic layer (112) comprising catalytic material (108) and optionally a carrier material (114) and a protective layer (116) comprising protective material (110) is arranged at least in sections under the catalytic layer (112).

10. Catalyst (100) according to one of the preceding claims, characterized by a plurality of plates (104) which extend along a flow direction of the catalyst (100) and which at least partially comprise the catalytic material (108) and / or the protective material (110).

11. Catalyst (100) according to one of the preceding claims, characterized by a honeycomb body, wherein the honeycomb body has a plurality of channels which extend along a flow direction of the catalyst (100) and which at least partially have the catalytic material (108) and / or the protective material (110).

12. Catalyst (100) according to one of the preceding claims, characterized in that the catalyst (100) comprises a hydrogen oxidation catalyst.

13. Catalyst (100) according to one of the preceding claims, characterized in that the catalyst (100) comprises a methane oxidation catalyst (MOC).

14. Catalyst (100) according to one of the preceding claims, characterized in that the catalyst (100) has a catalytic afterburner (24).

15. Electrochemical cell devices (10), in particular fuel cell devices (10), comprising an electrochemical cell unit (12) and at least one catalyst (100) according to one of the preceding Claims.

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