Method for removing nh3 from a gas stream

Abstract

The invention relates to a method of producing a fuel gas composition. The method comprises providing a feed gas composition comprising H2 and NH3, monitoring the concentration of NH3 in the feed gas composition; providing an oxidizing gas comprising NO and at least one of O2, NO2, and NO2+O2; mixing the feed gas composition with the oxidizing gas to provide a catalytic gas composition; providing a NOx reduction reactor having a catalytic gas inlet and a fuel outlet, and a selective reduction catalyst between the catalytic gas inlet and the fuel outlet; applying the catalytic gas composition to the catalytic gas inlet and passing the catalytic gas composition through the selective reduction catalyst; obtaining the fuel gas composition at the fuel outlet. The method can remove NH3 to improve H2-based fuels.

Description

TECHNICAL FIELD

[0001] The present invention relates to the removal of ammonia from a gas stream containing hydrogen. In particular, when ammonia is used as a hydrogen carrier, hydrogen can be released from ammonia by cracking of ammonia. The product gas can still contain small amounts of ammonia. The method allows the selective conversion of ammonia into nitrogen and water with little loss of hydrogen. The method is particularly suitable for, but not limited to, applications where hydrogen feed for fuel cells is produced by ammonia cracking. BACKGROUND

[0002] Ammonia (NH3) is an interesting carbon-free compound for energy storage and power generation fuels. For example, NH3 is considered as an alternative fuel for internal combustion engines, especially in maritime applications, but NH3 is also seen as a fuel for fuel cells. In certain types of fuel cells, such as polymer electrolyte membrane (PEM), anion exchange membrane (AEM), alkaline fuel cells, NH3 has to be converted into H2 and N2 before it can be used as a fuel in a fuel cell. The thermal cracking of NH3 into H2 and N2 (reaction 1) occurs spontaneously above 500 °C and is practically completed at 1100 °C. The cracking reaction is usually carried out in the presence of a catalyst, which allows the reaction to proceed more efficiently at lower temperatures. The H2 formed by cracking is then converted into H2O and electrical energy in a fuel cell according to reaction 2.

[0003] Reaction 1 2 NH3 N2 + 3 H2

[0004] Reaction 2 H2 + ½ O2 H2O

[0005] An example of the application of NH3 as a carrier for H2 is described in Fraunhofer Research News, March 1, 2021, pages 1-4. In this example, a high-temperature ammonia power fuel cell for maritime applications is proposed, in which NH3 is first converted into H2 and N2 by cracking of NH3, with 100 ppm of NH3 remaining. The cracking product containing H2 / N2 / NH3 is then sent to a fuel cell, where H2 reacts with O2 to produce electricity. Due to incomplete conversion, the exhaust gas from the fuel cell contains some H2 and some NH3. To avoid unwanted NH3 emissions, the exhaust gas is subsequently sent to a Pt-based oxidation catalyst to oxidize NH3 into nitrogen and water. Because the Pt catalyst also oxidizes H2, this method of reducing NH3 emissions means a substantial loss of H2, and thus also a loss of efficiency of the energy system.

[0006] One approach to reduce NH3 is to remove residual NH3 from the fuel stream directed to the fuel cell. For example, JP2014123468 describes how to use a hydrocarbon gas to provide H2 as fuel for a fuel cell, and catalytic conversion of the hydrocarbon gas can generate ammonia, which is removed by absorption in water before the H2 is directed to the fuel cell.

[0007] There are other examples of converting NH3 to H2 and N2 and directing to the fuel cell, but since the conversion rate is rarely 100%, it is suggested to remove residual NH3. US 2020 / 403258 describes a system having a decomposition reaction device for generating H2 by decomposing NH3 and a hydrogen fuel cell, and the system includes removing residual NH3 by an adsorption method, a complexation method, or a selective catalytic oxidation method. The adsorption method is to adsorb ammonia gas using a zeolite molecular sieve as an adsorbent or using activated carbon; and the complexation method uses MgCl2 or CuCl2 to perform a complexation reaction with ammonia gas to remove the ammonia gas; and the selective catalytic oxidation method uses a transition metal oxide as a catalyst to oxidize the ammonia gas to remove the ammonia gas.

[0008] Tuna et al (Fuel, Vol. 105, 2013, pp. 331-337) relates to selective catalytic oxidation of ammonia with nitrogen oxides in model syngas and discloses a study of selective oxidation of ammonia in a reducing environment, where NO x is removed from the flue gas by reacting with the injected ammonia on a catalyst.

[0009] US5906803 discloses a method for removing ammonia from gasification gas obtained from a fuel by selective oxidation in the presence of a solid catalyst, and is intended to oxidize ammonia substantially without affecting the hydrogen, methane or other oxidizing components of the gasification gas, and by this method, ammonia can be decomposed more completely and / or at significantly lower temperatures than when using previously used catalysts.

[0010] US8337793 relates to a method and apparatus for removing ammonia from an oxygen-containing fluid, such as effluent, flue gas or waste liquid, in which the NH3-containing fluid mixture is conveyed through two functional units, in which the NH3 effluent can be converted with high selectivity into nitrogen, and the NH3 is first decomposed into nitrogen in an oxidation / decomposition unit for NH3, and partially catalytically or thermally converted into nitrogen oxides NO and NO2, all the fluid passes through this unit, or a part of the fluid can bypass this unit through a bypass, in which the fluid streams can be combined after the bypass and allowed to mix together in a mixing space, in which the fluid containing NH3 and nitrogen oxides are mixed with each other sufficiently.

[0011] KR20240010242 discloses a method of producing hydrogen gas from ammonia, which includes a step of producing hydrogen gas and nitrogen gas by decomposing ammonia through an ammonia decomposition reaction, followed by a step of removing unreacted ammonia. The hydrogen production system has an ammonia decomposition reactor containing a catalyst to produce hydrogen gas and nitrogen gas through ammonia decomposition; and an unreacted ammonia removal reactor containing a selective oxidation catalyst for oxidizing and removing unreacted ammonia; and a jet nozzle is installed on the exhaust gas stream between the ammonia decomposition hydrogen production system and the selective ammonia oxidation catalyst reactor.

[0012] KR20230083367 discloses an ammonia decomposition system and method for a ship, the system including a vaporizer that receives liquid ammonia and vaporizes it; a decomposition unit that receives ammonia vaporized in the vaporizer and thermally decomposes it to produce a decomposition gas containing hydrogen gas, nitrogen gas, and un-decomposed ammonia; an un-decomposed ammonia removal unit that collects un-decomposed ammonia from the decomposition gas; a hydrogen gas purifier that receives the decomposition gas that has passed through the un-decomposed ammonia removal unit, removes nitrogen gas, and purifies it into hydrogen gas; and a selective catalytic reduction unit that performs denitrogenation on combustion gas generated by thermal decomposition of ammonia in the decomposition unit.

[0013] There is a need for an improved procedure to remove residual NH3 from a decomposed NH3 stream, and the present invention aims to address this need. SUMMARY

[0014] The present invention relates to a method of producing a fuel gas composition. In its broadest sense, the method comprises the steps of: providing a feed gas composition comprising H2 and NH3, monitoring the concentration of NH3 in the feed gas composition; providing an oxidation gas comprising NO and at least one of: O2, NO2, and NO2 + O2; mixing the feed gas composition with the oxidation gas to provide a catalytic gas composition; providing a NO xA reduction reactor has a catalytic gas inlet and a fuel outlet, and a selective reduction catalyst between the catalytic gas inlet and the fuel outlet; a catalytic gas composition is applied to the catalytic gas inlet and passed through the selective reduction catalyst; a fuel gas composition is obtained at the fuel outlet. This method can be used to remove ammonia from a hydrogen-containing gas stream, where the hydrogen is intended to be used as fuel, and the feed gas composition can be provided by ammonia cracking, or the feed gas composition can be a gas stream from a fuel cell, such as an exhaust gas stream containing unconverted hydrogen from the fuel cell, thus ammonia removal allows the provided fuel gas composition to be recycled back to the fuel cell. Generally, the concentration of NH3 can be up to 10% of the feed gas composition, for example when the feed gas composition is provided by ammonia cracking. The concentration of H2 is typically at least 1% of the feed gas composition. For example, the concentration of H2 in the feed gas composition can range from 1% to 99%, for example, from 2% to 95%.

[0015] In one example, the molar content of H2 in the feed gas composition is at least 50% of the gas feed gas composition, and the ratio of H2 to NH3 is at least 6. For example, when the feed gas composition is a cracked ammonia stream, the feed gas composition should contain at least 50% H2 and the ratio of H2 to NH3 should be at least 6.

[0016] In another example, the molar content of H2 in the feed gas composition is at most 50% of the feed gas composition, and the ratio of H2 to NH3 is at most 10. This example is relevant when the feed gas composition is exhaust gas from a fuel cell, particularly a solid oxide fuel cell (SOFC). In one example, the feed gas composition is exhaust gas from a fuel cell, and the concentration of H2 in the feed gas composition is in the range of 1% to 30%.

[0017] This method provides a catalytic gas composition, particularly by mixing an oxidizing gas and a feed gas composition. The catalytic gas composition may also be referred to as a gas composition for the selective catalytic reduction of NO, an SCR gas composition, or a selective catalytic reduction gas composition.

[0018] This method allows for the removal of ammonia, particularly small amounts, from a hydrogen-containing gas stream. Specifically, when ammonia is used as a hydrogen carrier, hydrogen is released from the ammonia through its cracking. The product gas may still contain a small amount of ammonia. The method of this invention allows for the selective conversion of ammonia into nitrogen and water with minimal hydrogen loss. The application of this invention is particularly suitable for, but not limited to, applications that generate hydrogen feedstock for fuel cells through ammonia cracking.

[0019] The fuel gas composition produced in this method can also be described as NH3 removal. In this context, NH3 removal means that NH3 has been removed from the treated feed gas composition, and "NH3 removal" can, for example, mean that the fuel gas composition contains up to 100 ppm of NH3, but preferably even lower, such as up to 50 ppm or up to 10 ppm. The low level of NH3 in the fuel gas composition allows it to be used as fuel in a fuel cell, regardless of the fuel cell's sensitivity to NH3. For example, the fuel gas composition can be used in polymer electrolyte membranes (PEMs), anion exchange membranes (AEMs), or alkaline fuel cells.

[0020] Selective catalytic reduction (NH3-SCR) is commonly used to remove NO from exhaust gases of lean fuel combustion processes (i.e., combustion processes with excess air, such as in diesel engines, power plants, and chemical plants). x Gas. In this context, the abbreviation "NH3-SCR" generally refers to a process used to remove NO from exhaust gases. x The selective reduction reaction of gases is a separate process, but it may also be relevant in the context of this method. The NH3-SCR technique is based on reactions 3 and 4, which reduce NO to NO via ammonia reduction in the presence of oxygen. x It is converted into nitrogen and water.

[0021] Reaction 3: 4 NO + 4 NH3 + O2 4 N2 + 6 H2O

[0022] Reaction 4: 2 NO + 4 NH3 + 2 NO2 4 N2 + 6 H2O

[0023] This method employs an oxidizing gas containing NO and at least one of the following: O2, NO2, and NO2 + O2. In the context of this invention, NO and NO2 can be collectively referred to as "NO". x Therefore, when this disclosure refers to NO... x At that time, it can be NO, NO2, or a mixture of NO and NO2 in any proportion.

[0024] NH3-SCR technology uses the term "reduction" to refer to and involves the reduction of NO. x It's a gas, but the reaction necessarily involves oxidation, that is, using NO. x The gas oxidizes NH3. However, the inventors have now unexpectedly discovered that it is used to remove NO from exhaust gases produced by the combustion of fossil fuels. xA gaseous NH3-SCR catalyst can be used to remove NH3, i.e., to convert NH3 to N2 and H2O with the aid of NO, O2, and NO2, without over-oxidizing the H2 present in the gas. Therefore, reactions 3 and 4 are also relevant in this method. Thus, the NH3-SCR catalyst can be used to selectively remove NH3 from the feed gas with H2 to provide an H2-based fuel gas. Any NH3-SCR catalyst that can be used to treat exhaust gases plays an equivalent role in this method. In the context of this method, NH3-SCR catalysts are generally referred to as "selective reduction catalysts," but selective reduction catalysts can also be referred to as selective catalytic reduction of NO or selective catalytic reduction of NO. x The selective catalytic reduction of NO involves an active catalyst. Accordingly, reactors with catalysts are typically referred to as NO reactors. x It is a reduction reactor, but it can also be called an SCR reactor.

[0025] In the combustion process of fossil fuels in excess air, the exhaust gas still contains some oxygen, typically ranging from 2% to 15%, depending on the combustion conditions. Ammonia can reduce NO in the presence of oxygen. x This has led to the selection of NH3-SCR technology, which is commonly used to remove NO from exhaust gases from lean fuel combustion processes. x Gases. When the concentration of a gas is provided as a percentage in the context of this invention, it should be understood as a molar content unless otherwise stated. Accordingly, unless otherwise stated, content is based on moles in the context of this invention.

[0026] When used to remove NO from exhaust gas x At that time, the NH3-SCR reaction utilizes the presence of ammonia. Since the waste gas does not contain ammonia, it will be used to convert the NO in the waste gas. x Ammonia is added to the exhaust gas stream. This technique can be performed in different ways. In diesel internal combustion engines in vehicles, NO in the exhaust gas is measured. x The concentration of urea is adjusted, and an appropriate amount of urea is sprayed into the airflow. At sufficiently high temperatures typically present in vehicle exhaust systems, urea decomposes to release ammonia required for the NH3-SCR reaction.

[0027] Another way to implement NH3-SCR technology is to inject an appropriate amount of ammonia in gaseous form into the waste gas stream. This method is commonly used if ammonia is available, and is often the case in chemical plants and power plants. Another way to implement NH3-SCR technology is to inject an appropriate amount of ammonia, thereby decomposing M... a (NH3) n X zThe salts release ammonia, where M represents one or more cations selected from alkaline earth metals and transition metals, and X represents one or more anions (see, for example, US7964163, US9889403). All these methods share the commonality of measuring NO in exhaust gas. x The concentration of NO is determined, and the amount of ammonia injected is determined based on the measured amount of NO.

[0028] Clearly, in the field of internal combustion engines, the term "reduction" refers to the reduction of NO by means of NH3 and a suitable catalyst. x The fact that the gas undergoes reduction, and for the purposes of this invention, the reaction of interest can be described as a selective oxidation reaction in which NH3 is oxidized. However, since the reaction of interest involves both reduction and oxidation, the catalyst used in this method is referred to as a "selective reduction catalyst." In the context of this disclosure, a selective reduction catalyst may also be referred to as a "SCR catalyst," and the two terms are used interchangeably.

[0029] This method employs an oxidizing gas containing NO and at least one of the following: O2, NO2, and NO2 + O2. Generally, NO must be present in the oxidizing gas, and a combination of NO2 and / or O2 is also present. Without being bound by any particular theory, the inventors believe that NO and O2 can react to form NO2. The reaction between the oxidizing gas and NH3 typically proceeds in a combination of reactions 3 and 4. Accordingly, the optimal composition of the oxidizing gas can be based on the stoichiometry of reactions 3 and 4, and the oxidizing gas can be described by the number of atoms in the oxidizing gas molecules relative to the number of atoms in the feed gas composition molecules. In one example, the oxidizing gas contains NO and at least one of the following: O2, NO2, and NO2 + O2, wherein the ratio of oxygen atoms to nitrogen atoms in NH3 is at least 1.5, the ratio of nitrogen atoms to nitrogen atoms in NH3 is in the range of 0.8 to 1.2, and the ratio of oxygen atoms in NO2 to nitrogen atoms in NH3 is at most 1. The oxidizing gas may contain additional atmospheric components, for example, when O2 is provided by ambient air. In the context of this invention, additional atmospheric components may include inert gases such as argon, neon, and helium, CO2, and H2O, but are not limited to these types. Furthermore, when additional atmospheric components are present, their presence is so minimal that the oxygen atoms contained in each additional atmospheric component can be neglected when calculating the ratio of oxygen atoms to nitrogen atoms in the NH3 of the feed gas composition. The ratio of oxygen atoms to nitrogen atoms in NH3 may be at least 1.5, but preferably at most 10. In one example, the ratio of oxygen atoms to nitrogen atoms in NH3 is selected from the stoichiometry of reactions 3 and 4.

[0030] This method uses an oxidizing gas containing NO, and O2 can also be used. The presence of O2 in the oxidizing gas generally does not negatively affect the catalytic removal of NH3, therefore there is no upper limit to the permissible O2 content in the oxidizing gas. Conventional NH3-SCR technologies, as used in the context of fossil fuel combustion, typically involve oxygen concentrations between 2% and 15%, representing the conditions under which the NH3-SCR reaction proceeds effectively. However, the general behavior of NH3-SCR catalysts is that their activity decreases rapidly when the oxygen concentration approaches zero. However, the inventors unexpectedly discovered that in this method, even when the O2 content in the catalytic gas composition is below 2%, conventional NH3-SCR catalysts operate at a sufficient rate to allow the selective oxidation of NH3 to occur. Therefore, in one example, the oxidizing gas contains O2 to provide a maximum O2 concentration of 2% in the catalytic gas composition. Under reasonable conditions, even with oxygen concentrations of approximately 100 ppm to 1000 ppm, the NH3-SCR activity is sufficiently high to effectively remove NH3, making the method of this invention a feasible way to remove ammonia from a hydrogen-containing gas stream. For example, NH3 can be in the range of 0.1% to 2%, such as 0.1% to 1%. Regardless of the O2 concentration in the catalytic gas composition, the ratio of oxygen atoms to nitrogen atoms in the NH3 of the feed gas composition can be in the range of 1.5 to 50, such as 1.5 to 20 or 1.5 to 10.

[0031] When used to remove NO from exhaust gas x In this process, a catalyst is used in the NH3-SCR reaction. Any catalyst known for NH3-SCR treatment of exhaust gases can be used as a selective reduction catalyst in this method. Generally, suitable SCR catalysts include catalytically active compounds supported on a carrier material. Commonly used catalysts are based on vanadium oxide supported on anatase TiO2, Cu zeolite, or Fe zeolite; see, for example, TV Johnson, Review of Selective Catalytic Reduction (SCR) and Related Technologies for Mobile Applications, in: Urea-SCR Technology for deNOx. xAfter Treatment of Diesel Exhausts. E. Tronconi, I. Nova., Springer Science + Business Media, New York, 2014: pp. 3–32, which are incorporated herein by reference. Therefore, the selective reduction catalysts are selected from the list of V-oxides / TiO2, V2O5 / TiO2, Cu-zeolite, and Fe-zeolite, or combinations thereof. Other known types of catalysts consist of: one or more transition metal oxides, such as manganese oxide, tungsten oxide, iron oxide, or rare earth metal oxides, such as cerium oxide; Mn-Fe spinel, Ni-Mn spinel, which can be supported on an oxide support, such as titanium dioxide, vanadium oxide, cerium dioxide, silicon dioxide, manganese oxide, carbon nanotubes, or a material called Santa Barbara Amorphous-15 (SBA-15), as in L. Han et al., Selective Catalytic Reduction of NO x With NH3 by Using Novel Catalysts: State of the Artand Future Prospects, Chem. Rev. 119(2019)10916-10976, which is incorporated herein by reference. Therefore, the selective reduction catalyst can be vanadium oxide supported on anatase TiO2, Cu zeolite, or Fe zeolite; transition metal oxides, such as manganese oxide, tungsten oxide, or iron oxide; rare earth metal oxides, such as cerium oxide; Mn-Fe spinel or Ni-Mn spinel, which can be supported on an oxide support, such as titanium dioxide, vanadium oxide, cerium dioxide, silicon dioxide, manganese oxide, carbon nanotubes, or SBA-15. The selective reduction catalyst can also be a combination of several catalytic compounds or materials.

[0032] Other related selective reduction catalysts are described in WO 2018 / 197176, which discloses a bag filter having one or more fabric filter bags containing an SCR catalyst for reducing NO at relatively low temperatures in the presence of ammonia. x The gas, and WO 2018 / 184921 discloses a system and corresponding method for removing nitrogen oxides, volatile organic compounds and particulate matter from engine exhaust, with a focus on improving NO removal during engine cold start. x Reduction. This method involves forming NO2 in the exhaust gas passage outside the exhaust gas cleaning system and injecting the prepared NO2 into the engine exhaust gas in an amount that promotes a rapid SCR reaction.

[0033] Exemplary selective reduction catalysts are provided in powder form and can be processed into various forms of catalyst products, such as pellets, rings, extrusions (e.g., flow-through or wall-flow monolithic feeds), spheres, hollow spheres, and particles. The sizes of these products typically range from about 1 mm to 5 cm. Such catalyst products may contain cavities (see, for example, Synthesis of Solid Catalysts; de Jong, KP (ed.); Wiley-VCH).

[0034] Weinheim, 2009, Chapter 9 (included herein by reference). The powder support material may be treated prior to the addition of the active component or promoter for the NH3-SCR catalyst. In such cases, the selected active compound or promoter, or both, is deposited on such a pre-formed solid support material by methods known to those skilled in the art (Heterogeneous Catalysis and Solid Catalysts, UllmannEncyclopedia 2009, Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim, page 47 and subsequent pages; Synthesis of Solid Catalysts; de Jong, KP (ed.); Wiley-VCH: Weinheim, 2009, Chapters 3–8, incorporating herein by reference). In the second procedure, after depositing the active compound or promoter using methods known to those skilled in the art, the powder is processed into a catalyst product (Synthesis of Solid Catalysts; de Jong, KP (ed.); Wiley-VCH: Weinheim, 2009, Chapters 3–9, which are incorporated herein by reference). The catalyst powder can also be processed into catalyst products with dimensions ranging from 1 cm to 500 cm, such as ceramic foams, 3D-printed forms, and porous ceramic filters (S. Govender and HB Friedrich, Monoliths: A Review of the Basics, Preparation Methods and Their Relevance to Oxidation, Catalysts (2017), 7, 62, which are incorporated herein by reference). In the third procedure, the procedures mentioned herein are combined such that a solid support material in powder form that is active for NH3-SCR is processed into a catalytic product, and then a second part of the same or different powders having NH3-SCR activity is deposited by methods known to those skilled in the art (Synthesis of Solid Catalysts; de Jong, KP (ed.); Wiley-VCH: Weinheim, 2009, Chapters 3-9, which are incorporated herein by reference).

[0035] In another embodiment, the powder having NH3-SCR activity is processed into a catalytic article by applying it to an accessible surface of a preform, such as a flow-through bulk material, wall-flow filter, or corrugated bulk material, plate, mesh, filament, other preform, glass wool, or metal wool, known from exhaust gas treatment catalysts in automotive applications, by means of, for example, carrier coating, deposition, or any other method designed to fix a solid carrier material to the outer surface of a solid body (Avila et al., Chem. Eng. J. (2005), 109, 11–36, which are incorporated herein by reference). The preform can, in principle, be any solid material, such as metals, oxides, ceramics, glass fibers, or polymers. Such articles are typically based on fibrous or powdered materials, which are pre-formed into solids using appropriate binders, coatings, and adhesives (S. Govender and HB Friedrich, Monoliths: A Review of the Basics, Preparation Methods and Their Relevance to Oxidation, Catalysts (2017), 7, 62, which are incorporated herein by reference).

[0036] Flow-through monolithic substrates have narrow, parallel gas flow paths extending from the inlet to the outlet of the substrate, making the paths open to fluid flow. The paths are essentially straight paths from their fluid inlet to their fluid outlet, defined by walls. A catalyst can be coated as a carrier, allowing the gas flowing through the paths to contact the catalyst. The flow paths of the monolithic substrate are typically thin-walled channels that can have any suitable cross-sectional shape and size, such as trapezoidal, rectangular, square, sinusoidal, hexagonal, elliptical, circular, etc. Such structures can contain approximately 20-900 or more gas inlet openings (e.g., orifices) per square inch of cross-section (3-140 orifices / cm²). 2 The wall thickness, such as the thickness of the walls separating the channels of the substrate from each other, is typically from about 0.005 cm to about 0.3 cm. Flow-through bulk materials typically have a porosity greater than 20%, typically from 20% to 70%, particularly 35% to 65% [measured according to DIN 66133]. The average pore size is typically at least 1 µm, for example from 1.5 µm to 25 µm, preferably greater than 3 µm, particularly 5 µm to 18 µm, for example measured according to DIN 66134.

[0037] Corrugated monolithic materials can consist of alternating layers of flat and corrugated sheets, the corrugated sheets having regular curved folds or grooves. Channels can be formed in the corrugated layers of the article by winding or stacking the combined flat and corrugated sheets into the desired form. In principle, such structures can be made of any material capable of forming, assembling, and maintaining such structures, such as metals, ceramics, paper, polymers, and fiberglass sheets. To stabilize the structure, one or more additional processing steps may be required, such as welding, brazing, gluing, coating, or heating. Such corrugated substrates and their manufacture are disclosed in WO 2010 / 066345, which is incorporated herein by reference, and its teachings can be applied to this invention. Corrugated catalytic articles can be obtained by applying a catalytically active material to the surface of the channels or to the porous structure of these materials.

[0038] A preferred embodiment of the corrugated catalytic article is a corrugated article based on a glass fiber substrate. The glass fiber substrate should have a wall density of at least 50 g / L but not more than 150 g / L and a porosity of at least 50%. The substrate monolith may consist of glass sheets with high silica content or E-glass fiber sheets. The glass sheets with high silica content may optionally contain a metal oxide layer, such as alumina, silica, TiO2, or diatomaceous earth, to stabilize the structure. In this invention, catalyst powder with an NH3-SCR active support can be applied to the surface of the corrugated and flat sheets of the article, for example, by support coating. In another embodiment, catalyst powder with NH3-SCR activity can be applied inside the porous structure of the glass fiber material constituting the corrugated and flat sheets of the article. In yet another embodiment, a compound active for NH3-SCR is applied directly to the corrugated and flat sheets. In a typical method of producing such glass fiber articles, these articles are contacted with, for example, a suitable precursor solution, according to methods known to those skilled in the art (Heterogeneous Catalysis and Solid Catalysts, Ullmann Encyclopedia 2009, Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim, pp. 47 and following; Synthesis of Solid Catalysts; de Jong, KP (ed.); Wiley-VCH: Weinheim, 2009, Chapters 3–8, which are incorporated herein by reference). Through this process, compounds with NH3-SCR activity can be deposited onto the article in the form of small clusters. These clusters can be fixed to the outer surface of the glass fiber wall or within the porous structure of the glass fiber wall by appropriate drying and calcination procedures known to those skilled in the art.

[0039] Preferred selective reduction catalysts contain vanadium oxide on a suitable support material. Particularly preferred reduction catalysts contain vanadium oxide and tungsten oxide on a suitable support material (e.g., transition metal oxides, such as TiO2 or alumina).

[0040] The temperature used when passing the catalytic gas composition through the selective reduction catalyst is freely selectable, but temperature control is preferred. For example, the method may further include a step of controlling the temperature of the catalytic gas composition within the range of 100°C to 600°C when passing it through the selective reduction catalyst. The temperature at which the catalytic gas composition passes through the selective reduction catalyst may also be referred to as the operating temperature. Generally speaking, the higher the temperature, the more efficient the reaction; however, the selective reduction catalyst can be selected based on its optimal operating temperature. For example, the method may further include a step of controlling the temperature of the catalytic gas composition within the range of 150°C to 350°C when passing it through the selective reduction catalyst. In a specific example, the reduction catalyst comprises vanadium oxide or vanadium oxide and tungsten oxide on a suitable support material (e.g., TiO2), and the operating temperature is in the range of 250°C to 350°C.

[0041] This method includes the step of monitoring the concentration of NH3 in the feed gas composition. Generally, any gas can be monitored in this method, and the gas can be monitored at any stage, for example, before or after mixing the relevant gases and / or before or after the catalytic reaction. Any available technique can be used to monitor the gas. For example, an FTIR spectrometer can be used to monitor the concentrations of NO, NO2, NH3, and H2O.

[0042] The feed gas composition can be provided as a gas stream from an NH3 cracking reactor to contain H2 and N2, as well as residual NH3, which is intended to be used as an H2-containing fuel gas. Therefore, the feed gas composition can be provided in the following steps: providing a gaseous NH3 stream; providing an ammonia cracking reactor having an NH3 inlet and a cracked gas outlet, the ammonia cracking reactor containing an NH3 decomposition catalyst between the NH3 inlet and the cracked gas outlet; applying the gaseous NH3 stream at the NH3 inlet and passing the gaseous NH3 stream through the decomposition catalyst to obtain the feed gas composition containing H2, N2, and NH3 at the cracked gas outlet. Generally, any decomposition catalyst can be used in this method.

[0043] Relevant catalysts include commercially available Haber-Bosch catalysts. Exemplary NH3 decomposition catalysts are iron-based NH3 synthesis catalysts. Iron-based NH3 synthesis catalysts are well known to those skilled in the art and are readily available commercially.

[0044] When the feed gas composition originates from an NH3 cracking reactor and contains H2, N2, and NH3, the molar content of H2 in the feed gas composition is typically at least 50% of the gas feed gas composition, and the H2 to NH3 ratio is at least 6. Generally, the NH3 cracking process can be described by a conversion factor x, where x is the fraction of NH3 decomposed. Correspondingly, x can have a value of at most 1. When decomposition occurs at a value of x of 1, no residual NH3 remains in the gas stream exiting the cracking reactor. When the feed gas composition is provided as a gas stream from the NH3 cracking reactor, the value of x should be as high as possible to minimize the NH3 content in the gas stream leaving the cracking reactor. However, while x can be set as needed for the cracking process by appropriately configuring process parameters, obtaining a high x value is technically cumbersome, and cracking processes are rarely designed for complete cracking, i.e., x=1. However, by combining this method with the use of an NH3 cracking reactor to obtain an H2-based fuel gas stream, NH3 can be selectively removed from the fuel gas stream, thus providing a substantially NH3-free H2-based fuel gas even when x in the cracking process is below 1. Therefore, a more efficient method is provided overall. Thus, the present invention solves the problem of obtaining substantially NH3-free H2-based fuel gas by cracking NH3 under imperfect conditions. Generally, the H2 to NH3 ratio can be determined by the value of x during the cracking process. For example, when x = 0.8, the H2 to NH3 ratio is about 6. Therefore, x should be at least 0.8. However, it is preferred that x > 0.8, and the H2 to NH3 ratio can be up to 100. The H2 to NH3 ratio can also be higher than 100. For example, the H2 to NH3 ratio can be in the range of 6 to 100, such as in the range of 8 to 50 or 10 to 20. When the method includes obtaining a feed gas composition as a gas stream from an NH3 cracking reactor, the ammonia cracking reactor can be configured to have an x ​​value in the range of 0.8 to 0.98.

[0045] Alternatively, the feed gas composition can be provided as a gas stream from the fuel cell, containing NH3 and N2, as well as residual H2, and optionally also containing H2O. For example, the feed gas composition can be exhaust gas from the fuel cell or gas containing unreacted H2 from the fuel cell, particularly a SOFC. When the feed gas composition is exhaust gas from the fuel cell, the molar content of H2 is up to 50% of the gas feed gas composition, for example, up to 40%, up to 30%, up to 20%, up to 10%, up to 5%, up to 3%, or up to 2%, and the H2 to NH3 ratio is up to 10. The H2 to NH3 ratio in the gas stream from the fuel cell is generally determined by the efficiency of the fuel cell, for example, in terms of H2 conversion, but when the fuel gas for the fuel cell is provided by NH3 cracking, the value of x must be fully considered. For example, the H2 to NH3 ratio in the feed gas composition can be in the range of 0.05 to 10. Selective removal of NH3 allows the fuel gas thus provided to be recycled back to the fuel cell, so that residual H2 can be combusted in the fuel cell. Therefore, fuel gases, especially those provided by cracking NH3, can be utilized more effectively.

[0046] Oxidizing gases, such as those used in SCR reactions, can be freely provided, for example, by mixing NO with O2 and / or NO2, particularly such that the ratio of oxygen atoms to nitrogen atoms in the NH3 of the feed gas composition is at least 1.5, the ratio of nitrogen atoms to nitrogen atoms in the NH3 of the feed gas composition is in the range of 0.8 to 1.2, and the ratio of oxygen atoms in NO2 to nitrogen atoms in the NH3 of the feed gas composition is at most 1. In one example, the oxidizing gas is provided in the following steps: providing a gaseous NH3 stream; providing an NH3 oxidation reactor having an NH3 inlet, an oxidant inlet, and an outlet, and an NH3 oxidation catalyst between the NH3 inlet and the outlet; and applying the gaseous NH3 stream at the NH3 inlet of the NH3 oxidation reactor and an oxidant stream at the oxidant inlet, and passing the gaseous NH3 stream through the NH3 oxidation catalyst to obtain an oxidizing gas at the outlet of the NH3 oxidation reactor. The oxidant comprises an oxidizing substance, but may also contain other substances. The oxidizing substance is preferably O2, for example, the oxidant may be atmospheric air. Particularly preferred is that the oxidizing agent is O2, and the amount of O2 is selected based on the expected ratio of oxygen atoms to nitrogen atoms in the NH3 of the feed gas composition. It is generally preferred to monitor the composition of the gas at the outlet. For example, the concentrations of NO, NO2, and O2, and optionally H2O, can be monitored using an FTIR spectrometer.

[0047] Particularly preferred is that the gaseous NH3 stream is split into two streams: one directed to the NH3 oxidation reactor and the other to the ammonia cracking reactor. This allows NH3 from the same supply source to be used for both cracking and oxidation, providing the oxidizing gas. The NH3 concentration in the gas stream leaving the ammonia cracking reactor, representing the feed gas composition, can be monitored, and a certain amount of NH3 can be supplied from the gaseous NH3 stream to provide an appropriate amount of oxidizing gas from the NH3 oxidation reactor, matching the method of the present invention.

[0048] Generally, any gas flow at any stage of the method can be monitored to determine the concentration of any component that may be present in the process flow. The process flow can be monitored, for example, using an FTIR spectrometer. This method produces a fuel gas composition, particularly an H2-based fuel gas composition. The fuel gas composition can be intended for any use in which H2 is suitable as fuel. For example, H2 can be burned, or H2 can be converted into H2O and electrical energy in a fuel cell. The method may also include a step of removing at least one of O2, NO2, NO, and H2O at any stage of the method, but particularly from the fuel gas composition. In one example, H2O is removed from the fuel gas composition. H2O can be removed. For example, H2O can be removed using a condenser and / or an adsorbent. When the feed gas composition is exhaust gas from a fuel cell, H2O removal can be used, for example. Typically, exhaust gas from a fuel cell may contain H2O converted from H2, particularly when the fuel cell is an SOFC fuel cell, so removing H2O can prevent H2O accumulation. In another example, an airflow, such as a feed gas composition or a stream of pyrolyzed NH3, is passed through a separator, such as a membrane separator, to remove unwanted components.

[0049] The NH3 oxidation catalyst can be freely selected from suitable catalysts known to those skilled in the art. In one example, the NH3 oxidation catalyst comprises a platinum group metal. NH3 oxidation catalysts are commonly used to prepare nitric acid (HNO3) in a process known as the Ostwald process, and any variant of the Ostwald process, such as any known variant, can be used in this process. In the context of this invention, the platinum group metal can be at least one of Pt, Pd, Rh, Ru, and Ir. The platinum group metal can be supported on a support material, such as an oxide support material. In the context of this invention, the oxide support material can be alumina, silica, titanium dioxide, cerium dioxide, zeolite, silica zeolite, or a combination thereof. In one example, the platinum group metal comprises or is a fibrous material. For example, the platinum group metal can be in fibrous form, or the platinum group metal can be supported on a material in fibrous form. For example, the NH3 oxidation catalyst can comprise a catalytic metal, such as a platinum group metal, in filament form, such as a "catalytic filament" with a diameter in the range of 0.01 mm to 0.1 mm, or the NH3 oxidation catalyst can comprise a supporting metal in wire form, wherein the platinum group metal is supported on the metal wire. In both cases, the metal wire can be referred to as a "catalytic wire." The catalytic wire can have a diameter ranging from 0.1 mm to 1 mm. The catalytic wires can be bundled together in an ordered or random manner. For example, the catalytic wires can be woven together or formed into a structured mesh, or they can be assembled in the form of a catalytic wire mesh. The catalytic wire can be provided in the form of sheets or layers, and the sheets can have any thickness, depending on the situation, for example, in the range of 10 µm to 1 mm, such as 50 µm to 200 µm.

[0050] In one aspect, the present invention relates to a catalytic gas composition. Therefore, the present invention relates to a catalytic gas composition comprising N2, NH3, H2, NO, and at least one of the following: O2, NO2, and NO2 + O2, wherein the molar content of H2 is at least 50% of the catalytic gas composition, and the ratio of H2 to NH3 is at least 6, and wherein the ratio of oxygen atoms to nitrogen atoms in NH3 is at least 1.5, the ratio of nitrogen atoms to nitrogen atoms in NH3 is in the range of 0.8 to 1.2, and the ratio of oxygen atoms in NO2 to nitrogen atoms in NH3 is at most 1. Specifically, the catalytic gas composition can be obtained from the method of the present invention. For example, the feed gas composition can be provided by ammonia cracking, such that the molar content of H2 in the cracked ammonia is at least 50% of the catalytic gas composition, and the ratio of H2 to NH3 is at least 6, for example in the range of 6 to 100, for example in the range of 8 to 50 or 10 to 20.

[0051] This method can be carried out in a system including relevant appropriate unit operations that are fluidly connected. In another aspect, the present invention relates to a system comprising unit operations for performing the steps of the method. The system of the present invention can be configured to perform any instance of this disclosure. Any instance of the system may include an NH3 supply source, and the system may also be configured to provide air containing an oxidant, such as atmospheric air with O2 as the oxidant.

[0052] Related unit operations include

[0053] NO x A reduction reactor having a catalytic gas inlet and a fuel outlet, and a selective reduction catalyst between the catalytic gas inlet and the fuel outlet;

[0054] An ammonia cracking reactor having an ammonia inlet and a cracked gas outlet, the ammonia cracking reactor containing an NH3 decomposition catalyst between the ammonia inlet and the cracked gas outlet; and

[0055] An NH3 oxidation reactor having an NH3 inlet, an oxidant inlet and an outlet, and an NH3 oxidation catalyst between the NH3 inlet and the outlet; and a fuel cell having a fuel cell inlet and a fuel cell outlet.

[0056] In one example, the system includes: an NH3 oxidation reactor having an NH3 inlet, an oxidant inlet and an outlet, and an NH3 oxidation catalyst between the NH3 inlet and the outlet;

[0057] NO x A reduction reactor having a catalytic gas inlet and a fuel outlet, and a selective reduction catalyst between the catalytic gas inlet and the fuel outlet;

[0058] Oxygen inlet;

[0059] The feed gas mixing site is in fluid communication with the outlet, catalytic gas inlet, and oxygen inlet of the NH3 oxidation reactor; and

[0060] An NH3 sensor is used to measure the NH3 concentration of the gas entering the feed gas mixing site.

[0061] This system typically includes a piping network to provide useful connections between unit operations. The pipes in the network can be freely selected based on specific gases, temperatures, and pressures, but generally, pipes made of steel or stainless steel can be used from any pipe within the network. The pipes in the network can be connected to each other and to the relevant unit operations using any type of connection available in the field.

[0062] The system may include mixing sites for mixing different gas streams. Generally, mixing sites can be designated by indicating a specific function (e.g., what gas is being mixed or what gas is being supplied through mixing), and mixing sites may have several functions, particularly a mixing function. For example, the oxidizing gas contains NO and at least one of the following: O2, NO2, and NO2 + O2, and the system may include one or more mixing sites for mixing the components. In a specific example, NO is supplied by oxidizing NH3. x And NO x It can be mixed with O2 to provide an oxidizing gas relevant to the specific implementation scheme.

[0063] The system may include any number of sensors for analyzing the airflow at any step or stage of the method. For example, the system may include sensors for specific components, such as sensors other than the NH3 sensor. The system may also include one or more sensors for temperature, pressure, and / or flow rate.

[0064] Generally, the steps in this method may involve controlling temperature. In the context of this invention, the term "control" may refer to appropriately raising or lowering the temperature to achieve a target temperature, and maintaining the temperature once the target temperature is reached. Furthermore, the pipes of the unit operation and the piping network may include thermal insulation to minimize heat loss from the thermally insulated unit operation or piping. Any unit operation may be integrated with another unit operation or otherwise configured to transfer heat (e.g., heat considered as waste heat) from the heat-generating unit operation to a unit operation capable of utilizing the heat.

[0065] The method of this invention is generally based on a gaseous flow, and the gas pressure in different steps can be freely selected according to the needs of the specific reaction. The method and system may include a compressor or pressure reducer to change the pressure of the gaseous flow to an appropriate value. However, when NH3 decomposes, NH3 can be supplied in liquid NH3 form, for example, from a storage tank. The liquid NH3 is then converted to a gaseous form before decomposition.

[0066] The system may also include an NH3 supply source; and an ammonia cracking reactor having an ammonia inlet and a cracked gas outlet, the ammonia cracking reactor containing an NH3 decomposition catalyst between the ammonia inlet and the cracked gas outlet, wherein the NH3 supply source is in fluid communication with the ammonia inlet and the cracked gas outlet is in fluid communication with a connecting pipe; wherein the NH3 supply source is in fluid communication with both the NH3 inlet and the ammonia inlet.

[0067] In yet another example, the system includes a fuel cell having a fuel cell inlet and a fuel cell outlet, wherein the fuel outlet is in fluid communication with the fuel cell inlet and the fuel cell outlet is in fluid communication with the feed gas mixing site.

[0068] The system may specifically include a heating device configured to heat NO. x The temperature of the reduction reactor is adjusted to a range of 100°C to 600°C. In a specific example, the selective reduction catalyst comprises vanadium oxide on a support material. In another example, the NH3 oxidation catalyst comprises platinum group metals on a support material.

[0069] Any embodiment of the invention can be used in any aspect of the invention, and any advantages of the particular embodiment also apply when the embodiment is used in a particular aspect. Attached Figure Description

[0070] The invention will be explained in more detail below with the aid of examples and with reference to schematic diagrams, wherein

[0071] Figure 1 The system of the present invention is shown;

[0072] Figure 2 The system of the present invention is shown;

[0073] Figure 3 The system of the present invention is shown;

[0074] Figure 4 The effect of temperature on NH3 removal is shown in the method of the present invention;

[0075] Figure 5 The effect of temperature on NH3 removal in the method of the present invention is shown.

[0076] The invention is not limited to the embodiments shown in the accompanying drawings. Therefore, it should be understood that where a feature mentioned in the appended claims is followed by a reference numeral, such reference numerals are included only for the purpose of enhancing the comprehensibility of the claims and in no way limit the scope of the claims.

[0077] As used in this specification and claims, the term "comprising" means "consisting of at least a portion of". When interpreting statements in this specification and claims that include the term "comprising", other features may be present besides those beginning with this term in each statement. Related terms such as "comprise" and "comprised" will be interpreted in a similar manner. Detailed Implementation

[0078] This invention relates to a method for producing a fuel gas composition 1 and a system 100 for carrying out the method. The method involves the selective oxidation of NH3 in a feed gas composition 2 to provide an H2-based fuel gas 1 with NH3 removed. Figure 1An example of system 100 is shown, wherein the feed gas composition 2 is provided by cracking the gaseous NH3 stream 5 in an ammonia cracking reactor 20 before monitoring the NH3 in the feed gas composition 2 using an NH3 sensor 103. The feed gas composition 2 is then mixed with an oxidizing gas 3. Specifically, the oxidizing gas 3 is provided by oxidizing the NH3 stream 5 in an NH3 oxidation reactor 30. The feed gas composition 2 and the oxidizing gas 3 are mixed at the feed gas mixing site 102. Figure 1 As shown, system 100 is equipped with an oxygen inlet 101, allowing additional O2 gas 8 to be added to feed gas composition 4. Additional O2 gas 8 can be added to provide a specific ratio of oxygen atoms to nitrogen atoms of NH3 in feed gas composition 2.

[0079] like Figure 1 As shown, system 100 includes an NH storage tank 24. The NH storage tank 24 provides liquid NH3, which is converted into gaseous NH3 5 and directed to an ammonia cracking reactor 20 to provide feed gas composition 2, and then to an NH3 oxidation reactor 30 to provide oxidizing gas 3. System 100 has an NH3 sensor 103 that monitors the NH3 concentration of the feed gas composition 2 and, based on the recorded NH3 concentration, directs a proportion of the NH3 stream 5 to the NH3 oxidation reactor 30 to match the feed gas composition 2's demand for oxidizing gas 3.

[0080] The ammonia cracking reactor 20 contains an NH3 decomposition catalyst 23 between an ammonia inlet 21 and a cracked gas outlet 22. The NH3 decomposition catalyst 23 is a commercially available Haber-Bosch catalyst. Atmospheric air with O2 as the oxidant 7 is mixed with NH3 from an NH3 storage tank 24 at the oxidant inlet 32, and then the mixture is guided through the NH3 oxidation reactor 30.

[0081] The NH3 oxidation reactor 30 has an NH3 inlet 31, an oxidant inlet 32, and an outlet, with an NH3 oxidation catalyst 34 located between the NH3 inlet 31 and the outlet 33. The NH3 oxidation catalyst 34 comprises platinum on an alumina support. The reaction in the NH3 oxidation reactor 30 is carried out according to the Ostwald process, which can also be considered a standard technology for the production of nitric acid.

[0082] System 100 includes NO x Reduction reactor 10. Feed gas composition 2 is mixed with oxidizing gas 3 to provide catalytic gas composition 4, which is guided through NO via catalytic gas inlet 11. x Reduction reactor 10, to reduce NO x Fuel gas composition 1 is obtained at fuel outlet 12 of reduction reactor 10. xThe reduction reactor 10 contains a selective reduction catalyst 13 between the catalytic gas inlet 11 and the fuel outlet 12. Figure 1 The selective reduction catalyst 13 of system 100 is a V-oxide on a TiO2 support, but the NH3 decomposition catalyst 23 can be any catalytic material suitable for (e.g., known for) SCR treatment of exhaust gases.

[0083] The fuel gas composition 1 can be directed from the fuel outlet 12 to any operation where the H2-containing fuel gas composition 1 can be removed using NH3. This operation can be, in particular, a fuel cell. Since the fuel gas composition 1 is NH3-removed, the fuel cell can be freely selected.

[0084] In another instance, such as Figure 2 As shown, system 100 includes an ammonia cracking reactor 20 containing an NH3 decomposition catalyst 23 between an ammonia inlet 21 and a cracked gas outlet 22. The NH3 decomposition catalyst 23 is a commercially available Haber-Bosch catalyst, and system 100 is configured to produce hydrogen and N2 in a 3:1 ratio. System 100 also includes a solid oxide fuel cell (SOFC) 50, wherein the cracked gas outlet 22 is in fluid communication with the fuel cell inlet 51, thereby allowing cracked NH3 from the cracked gas outlet 22 to be used as fuel for the fuel cell 50. Exhaust gas 6 from the fuel cell outlet 52 is then used as feed gas composition 2, which is mixed with an oxidizing gas 3 and optionally an O2 gas 8 to provide a catalytic gas composition 4. The catalytic gas composition 4 is used to produce NO x The process takes place in a reduction reactor 10, which has a selective reduction catalyst 13, consisting of V-oxides on a TiO2 support, between a catalytic gas inlet 11 and a fuel outlet 12. Then, NO... x The fuel gas composition 1 generated in the reduction reactor 10 is recycled to mix with cracked NH3 from the cracked gas outlet 22. The system 100 includes a condenser 105 after the fuel outlet 12 to remove H2O from the fuel gas composition 1. Therefore, unreacted H2 from the fuel cell 50 can be recycled back to the fuel cell 50, thereby improving the utilization rate of H2.

[0085] In another instance, such as Figure 3 As shown, the flow from the ammonia cracking reactor 20 is directed through the cracked gas outlet 22 to the membrane separator 104 for H2 purification.

[0086] Example

[0087] Several experiments were conducted to illustrate the invention, and two types of SCR catalysts were selected: Cu-exchanged chabazite (or Cu-CHA) catalyst and V-oxide / TiO2 catalyst. Specifically, the Cu-CHA catalyst contained 3.2 wt% Cu and Si / Al = 6.7, and the oxide / TiO2 catalyst was 5.3 wt% V2O5 / 3.5 wt% WO3 / TiO2. The catalysts used in the examples were commercially available catalysts.

[0088] Example 1

[0089] A 50 mg sample of Cu-CHA catalyst (3.2 wt% Cu, Si / Al = 6.7) was placed in a quartz U-tube reactor (6 mm inner diameter). The catalyst was exposed to a gas consisting of 396 ppm NO, 429 ppm NH3, 1% O2, approximately 24% N2, and approximately 75% H2 at a flow rate of 9 N L / h between 180°C and 200°C. An FTIR spectrometer was connected to the reactor system, allowing measurement of the concentrations of NO, NO2, NH3, and H2O at the reactor inlet and outlet. Therefore, the NO to NH3 ratio at the inlet (i.e., in the feed gas) was 0.923, and the O2 to NH3 ratio at the inlet was 23.3.

[0090] The measured concentrations of NH3, NO, and water at the outlet are summarized in Table 1, which also shows the NH3 and NO concentrations at the inlet.

[0091] Table 1

[0092]

[0093] The ammonia concentration at the outlet measured under these conditions corresponds to a 99% conversion rate. The measured H2O concentration was approximately 2000 ppm. When there is a significant excess of 1% O2 in the feed (i.e., an O2 to NH3 ratio of 2:3), complete oxidation of hydrogen would result in a water concentration of 20,000 ppm, and correspondingly, if no H2 is oxidized, the amount of NH3 at the inlet would provide approximately 640 ppm H2O at the outlet. Therefore, the water concentration at the outlet is an order of magnitude lower, indicating that no significant H2 oxidation has occurred.

[0094] Example 2

[0095] This example investigated the effect of low oxygen concentrations on NH3 removal. A 50 mg sample of Cu-CHA catalyst (3.2 wt% Cu, Si / Al = 6.7) was placed in a quartz U-tube reactor (6 mm inner diameter). The catalyst was exposed to a gas consisting of 416 ppm NO, 484 ppm NH3, 1000 ppm O2, approximately 20% N2, and approximately 80% H2 at a flow rate of 9 N L / h between 180°C and 220°C. An FTIR spectrometer was connected to the reactor system, allowing measurement of the concentrations of NO, NO2, NH3, and H2O at the reactor inlet and outlet. Therefore, the NO to NH3 ratio at the inlet (i.e., in the feed gas) was 0.86, and the O2 to NH3 ratio at the inlet was 2.07.

[0096] The measured concentrations of NH3, NO, and water at the outlet are summarized in Table 2, which also shows the NH3 and NO concentrations at the inlet.

[0097] Table 2

[0098]

[0099] The results showed that ammonia was removed from the hydrogen-containing stream at oxygen concentrations as low as 1000 ppm. This means that ammonia removal remains effective even at such low oxygen concentrations. At low oxygen concentrations, the temperature can be increased to compensate for the inefficient removal of NH3.

[0100] Example 3

[0101] This example examined the effect of O2 concentration and demonstrated the relevance of oxygen to NH3 removal. A 50 mg sample of Cu-CHA catalyst (3.2 wt% Cu, Si / Al = 6.7) was placed in a quartz U-tube reactor (6 mm inner diameter). The catalyst was exposed to a gas consisting of 412 ppm NO, 429 ppm NH3, 1000 ppm O2, approximately 20% N2, and approximately 80% H2 at 180°C and a flow rate of 9 N L / h. An FTIR spectrometer was connected to the reactor system, allowing measurement of the concentrations of NO, NO2, NH3, and H2O at the reactor inlet and outlet. Therefore, the NO to NH3 ratio at the inlet (i.e., in the feed gas) was 0.96, and the O2 to NH3 ratio at the inlet varied between 0.58 and 2.33.

[0102] Table 3

[0103]

[0104] Example 4

[0105] This example demonstrates that H2 oxidation on Cu-CHA requires higher temperatures. A 50 mg sample of Cu-CHA catalyst (3.2 wt% Cu, Si / Al = 6.7) was placed in a quartz U-tube reactor (6 mm inner diameter). The catalyst was exposed to a gas consisting of 1% O2, 20% N2, and 80% H2, with the balance being N2, at a flow rate of 9 N L / h, and heated to 500°C at a rate of 2°C / min. The water concentration was then tracked as a function of temperature. Figure 4 The results show that the increase in H2O concentration at the outlet becomes significant first in the 350°C–500°C range, which is significantly higher than the 180°C–220°C range where NH3 removal occurs in the system of this invention. At 500°C, the measured water concentration is above 1.5%, close to 2%, which is the expected value when all oxygen is used for H2 oxidation. This directly indicates that at approximately 200°C, ammonia removal is selective, without significant oxygen loss due to hydrogen oxidation.

[0106] Example 5

[0107] This example demonstrates that the removal of NH3 at approximately 200°C requires the presence of NO. A 50 mg sample of Cu-CHA catalyst (3.2 wt% Cu, Si / Al = 6.7) was placed in a quartz U-tube reactor (6 mm inner diameter). The catalyst was exposed to a gas free of NO, consisting of 401 ppm NH3, 1% O2, approximately 24% N2, and approximately 75% H2, at a flow rate of 9 N L / h between 180°C and 200°C. An FTIR spectrometer was connected to the reactor system, allowing measurement of the concentrations of NO, NO2, NH3, and H2O at the reactor inlet and outlet.

[0108] The measured concentrations of NH3, NO, and water at the outlet are summarized in Table 4, which also shows the NH3 and NO concentrations at the inlet.

[0109] Table 4

[0110]

[0111] These values ​​indicate that NH3 was not removed in the absence of NO.

[0112] Example 6

[0113] This example demonstrates that vanadium oxide-based catalysts (another known type of SCR catalyst) can also be used to remove NH3 from a hydrogen-containing feed stream. 103 mg of a catalyst sample consisting of 5.3 wt% V2O5 / 3.5 wt% WO3 / TiO2 was placed in a quartz U-tube reactor (6 mm inner diameter). The catalyst was exposed to a gas consisting of 491 ppm NO, 417 ppm NH3, 1% O2, approximately 24% N2, and approximately 75% H2 at a flow rate of 9 N L / h at a temperature between 200°C and 240°C. An FTIR spectrometer was connected to the reactor system, allowing measurement of the concentrations of NO, NO2, NH3, and H2O at the reactor inlet and outlet.

[0114] The measured outlet concentrations of NH3, NO, and water are summarized in the table below.

[0115] Table 5

[0116]

[0117] The low concentrations of NH3 and H2O at the outlet indicate that NH3 was effectively removed from the gas stream without hydrogen oxidation.

[0118] Example 7

[0119] This example demonstrates the performance of a vanadium oxide-based catalyst at very low oxygen concentrations. 103 mg of a catalyst sample consisting of 5.3 wt% V₂O₅ / 3.5 wt% WO₃ / TiO₂ was placed in a quartz U-tube reactor (6 mm inner diameter). The catalyst was exposed to a gaseous mixture of 383 ppm NO, 458 ppm NH₃, 200 ppm O₂, approximately 24% N₂, and approximately 75% H₂ at a flow rate of 9 N L / h at a temperature between 270°C and 300°C. An FTIR spectrometer was connected to the reactor system, allowing measurement of the concentrations of NO, NO₂, NH₃, and H₂O at the reactor inlet and outlet.

[0120] The measured concentrations of NH3, NO, and water at the outlet are summarized in the table below.

[0121] Table 6

[0122]

[0123] The low concentrations of NH3 and H2O indicate that NH3 was effectively removed from the gas stream without hydrogen oxidation. The temperature was increased to 270°C–300°C to compensate for the lower NH3 removal rate due to the low oxygen concentration.

[0124] Example 8

[0125] This example demonstrates that even at high temperatures, the vanadium oxide-based catalyst does not oxidize hydrogen. 103 mg of a catalyst sample consisting of 5.3 wt% V₂O₅ / 3.5 wt% WO₃ / TiO₂ was placed in a quartz U-tube reactor (6 mm inner diameter). The catalyst was exposed to a gas consisting of 1% O₂, 80% H₂, and the balance N₂ at a flow rate of 9 N L / h and heated to 500°C at a rate of 2°C / min. The water concentration was then tracked as a function of temperature. Figure 5 The results showed that the H2O concentration at the reactor outlet remained below 0.1%, indicating that hydrogen oxidation did not occur even at high temperatures.

[0126] Reference Symbol List

[0127] 1. Fuel gas composition

[0128] 2. Feed gas composition

[0129] 3 Oxidizing gases

[0130] 4. Catalytic gas composition

[0131] 5. Gaseous NH3

[0132] 6. Exhaust gas

[0133] 7 Oxidizing agents

[0134] 8. Oxygen (O2)

[0135] 100 System

[0136] 10 NO x reduction reactor

[0137] 11 Catalytic gas inlet

[0138] 12 Fuel Exports

[0139] 13 Selective reduction catalysts

[0140] 20 Ammonia Cracking Reactor

[0141] 21 Ammonia Imports

[0142] 22. Pyrolysis gas outlet

[0143] 23 NH3 decomposition catalyst

[0144] 24 NH3 storage

[0145] 30 NH3 oxidation reactor

[0146] 31 NH3 entrance

[0147] 32 Oxidizing agent inlet

[0148] 33 Exports

[0149] 34 NH3 oxidation catalyst

[0150] 101 Oxygen Inlet

[0151] 102 Feed gas mixing site

[0152] 103 NH3 sensor

[0153] 104 Membrane Separator

[0154] 105 Condenser

[0155] 40 NH3 supply sources

[0156] 50 fuel cells

[0157] 51 Fuel Cell Inlet

[0158] 52 Fuel Cell Exports

[0159] 60 Heating device

Claims

1. A method for producing a fuel gas composition (1), the method comprising the following steps: A feed gas composition containing H2 and NH3 is provided (2); Monitor the concentration of NH3 in the feed gas composition (2); Provide an oxidizing gas containing NO and at least one of the following: (3) O2, NO2 and NO2 + O2; The feed gas composition (2) is mixed with the oxidizing gas (3) to provide a catalytic gas composition (4). Provide NO x A reduction reactor (10) having a catalytic gas inlet (11) and a fuel outlet (12), and a selective reduction catalyst (13) between the catalytic gas inlet (11) and the fuel outlet (12). The catalytic gas composition (4) is applied to the catalytic gas inlet (11) and the catalytic gas composition (4) is passed through the selective reduction catalyst (13). The fuel gas composition (1) is obtained at the fuel outlet (12). Its features The feed gas composition (2) has an H2 molar content of at least 50% of the gas feed gas composition (2) and an H2 to NH3 ratio of at least 6, or has an H2 molar content of at most 50% of the gas feed gas composition (2) and an H2 to NH3 ratio of at most 10.

2. The method for producing the fuel gas composition (1) according to claim 1, wherein the feed gas composition (2) is provided in the following steps: Provide gaseous NH3 flow (5); An ammonia cracking reactor (20) is provided having an ammonia inlet (21) and a cracked gas outlet (22), the ammonia cracking reactor (20) including an NH3 decomposition catalyst (23) between the ammonia inlet (21) and the cracked gas outlet (22); The gaseous NH3 stream (5) is applied at the ammonia inlet (21) and the gaseous NH3 stream (5) is passed through the decomposition catalyst to obtain the feed gas composition (2) at the cracked gas outlet (22), the feed gas composition (2) comprising H2, N2 and NH3.

3. The method for producing a fuel gas composition (1) according to claim 1, wherein the feed gas composition (2) is exhaust gas (6) from a fuel cell.

4. The method for producing a fuel gas composition (1) according to any one of claims 1 to 3, wherein in the oxidizing gas (3), the ratio of oxygen atoms to nitrogen atoms of NH3 in the feed gas composition (2) is at least 1.5, the ratio of nitrogen atoms to nitrogen atoms of NH3 in the feed gas composition (2) is in the range of 0.8 to 1.2, and the ratio of oxygen atoms of NO2 to nitrogen atoms of NH3 in the feed gas composition (2) is at most 1.

5. The method for producing a fuel gas composition (1) according to any one of claims 1 to 4, wherein the catalytic gas composition (4) has an O2 concentration of up to 2%.

6. The method for producing a fuel gas composition (1) according to any one of claims 1 to 5, further comprising the step of controlling the temperature of the catalytic gas composition (4) in the range of 100°C to 600°C while passing the catalytic gas composition (4) through the selective reduction catalyst (13).

7. The method for producing a fuel gas composition (1) according to any one of claims 1 to 6, wherein the oxidizing gas (3) is provided in the following steps: Provide gaseous NH3 flow (5); An NH3 oxidation reactor (30) is provided, the oxidation reactor having an NH3 inlet (31), an oxidant inlet (32), and an outlet (33), and an NH3 oxidation catalyst (34) between the NH3 inlet (31) and the outlet (33); and The gaseous NH3 stream (5) is applied at the NH3 inlet (31) of the NH3 oxidation reactor (30), and the oxidant stream (7) is applied at the oxidant inlet (32), and the gaseous NH3 stream (5) is passed through the NH3 oxidation catalyst (34) to obtain the oxidizing gas (3) at the outlet of the NH3 oxidation reactor (30).

8. A catalytic gas composition (4), said catalytic gas composition comprising N2, NH3, H2, NO and at least one of the following: O2, NO2 and NO2 + O2, characterized in that, The molar content of H2 is at least 50% of the catalytic gas composition (4), and the ratio of H2 to NH3 is at least 6, wherein the ratio of oxygen atoms to nitrogen atoms of NH3 is at least 1.5, the ratio of nitrogen atoms to nitrogen atoms of NH3 is in the range of 0.8 to 1.2, and the ratio of oxygen atoms of NO2 to nitrogen atoms of NH3 is at most 1.

9. A system (100) comprising: An NH3 oxidation reactor (30) having an NH3 inlet (31), an oxidant inlet (32) and an outlet (33), and an NH3 oxidation catalyst (34) between the NH3 inlet (31) and the outlet (33). NO x A reduction reactor (10) having a catalytic gas inlet (11) and a fuel outlet (12) and a selective reduction catalyst (13) between the catalytic gas inlet (11) and the fuel outlet (12). Oxygen inlet (101); A feed gas mixing site (102) is in fluid communication with the outlet (33), the catalytic gas inlet (11), and the oxygen inlet (101) of the NH3 oxidation reactor (30); and NH3 sensor (103). The NH3 sensor (103) is characterized in that it is configured to measure the NH3 concentration of the gas entering the feed gas mixing site (102).

10. The system (100) of claim 9, wherein the system (100) further comprises: NH3 supply source (40); and An ammonia cracking reactor (20) having an ammonia inlet (21) and a cracked gas outlet (22), the ammonia cracking reactor (20) including an NH3 decomposition catalyst (23) between the ammonia inlet (21) and the cracked gas outlet (22), wherein an NH3 supply source (40) is in fluid communication with the ammonia inlet (21) and the cracked gas outlet (22) is in fluid communication with the feed gas mixing site (102); wherein The NH3 supply source (40) is in fluid communication with the NH3 inlet (31) and the ammonia inlet (21).

11. The system (100) according to claim 9 or 10 further includes a fuel cell (50) having a fuel cell inlet (51) and a fuel cell outlet (52), wherein the fuel outlet (52) is in fluid communication with the fuel cell inlet (51) and the fuel cell outlet (52) is in fluid communication with the feed gas mixing site (102).

12. The system (100) according to any one of claims 9 to 11, wherein the system (100) includes a heating device configured to heat the NO x The temperature of the reduction reactor (10) is adjusted to a range of 100°C to 600°C.

13. The system (100) according to any one of claims 9 to 12, wherein the selective reduction catalyst (13) comprises vanadium oxide on a support material.

14. The system (100) according to any one of claims 9 to 13, wherein the NH3 oxidation catalyst (34) comprises a platinum group metal.

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