Reduction of NOx and N2O in the exhaust gases of marine motors operated with NH3

Abstract

The present invention relates to the detection of NO in the exhaust gas of an internal combustion engine operated with NH3. X and reduction of N2O content. Internal combustion engines are installed on ships and are used to propel the ships.

Description

[Technical Field]

[0001] Priority is claimed from European Patent Application No. 22216421.2, filed December 23, 2022, and from European Patent Application No. 23165192.8, filed March 29, 2023.

[0002] The present invention relates to the detection of NO in the off-gas from an NH3-driven internal combustion engine. X and reduction of N2O content. [Background technology]

[0003] The internal combustion engine is installed on a ship and serves to move the ship.

[0004] Ammonia is one of the most widely produced and distributed chemicals worldwide, best known for its use as a fertilizer in agriculture. Recently, interest in its potential use as a high-quality energy source and as a carbon-free fuel for internal combustion engines has grown (H. Kobayashi et al., Proceedings of the Combustion Institute 37 (2019) 109-133; D. Erdemir et al., Int J. Energy Res. 2021, 45, 4827-4834; C. Tornatore et al., Frontiers in Mechanical Engineering 2022, 8, Article 944291). Its use in aircraft has also been discussed (A. Boretti et al., ACS Energy Lett. 2022, 7, 2557-2564).

[0005] Ammonia is carbon-free, has a global transportation and storage infrastructure, can be produced directly from renewable electricity, water, and air, and is therefore currently considered an intelligent energy source and combustion fuel.

[0006] Ammonia has a relatively low calorific value and a low flame propagation speed, which poses the risk of flame quenching and incomplete combustion. Furthermore, the combustion of NH3 poses the risk of increased emissions of nitrogen oxides (especially NO, NO2, and NO), which impacts its suitability as a combustion gas. There have been proposals for gaseous ammonia / hydrogen / air mixtures in which a certain hydrogen content is used as a combustion promoter, which can be produced, for example, by catalytic or thermally assisted NH3 dissociation (Ch. Lhuillier et al., 14th International Conference on Engines & Vehicles, 2019, Capri; S. Mashruk et al., Chemical Engineering Transactions, 89, 2021; S. Mashruk et al., Combustion and Flame 244 (2022) 112299).

[0007] The operating limits of an ammonia-fueled spark-ignition engine have been studied. Here, it was found that NH3 emissions in the off-gas decrease with increasing engine speed, with the highest values ​​being achieved at rich mixtures. NH3 emissions can reach up to 1% by volume. NO X The emissions consist mainly of NO, and the effect of engine speed appears to depend on the equivalence ratio. NH3 does not produce a carbon content in the exhaust, but it can release N2O, one of the most potent greenhouse gases. NO X For both NH3 and NO, the highest emissions were observed on the lean side and decreased with increasing equivalence ratio. Finally, even when pure ammonia was burned under rich conditions, H2 was produced in the off-gas, suggesting local decomposition of ammonia. Off-gas temperature was also monitored, and NH3 and NO were observed at least below 2000 rpm. X To reduce both NO emissions X This appears to be high enough to use catalysts for selective catalytic reduction (SCR) of CO₂ (Ch. Mounaim-Rousselle et al., Energies 2021, 14, 4141).

[0008] YK Park, Chemical Engineering Journal, Volume 461, Issue 141958, Published April 1, 2023, is a review article on the catalytic removal of nitrogen oxides (NO, NO2, N2O) from off-gases formed when ammonia is used as a fuel.

[0009] Japanese Patent Application Laid-Open Publication No. 2023-026798, published on March 1, 2023, relates to an off-gas treatment system for an ammonia engine, which includes an oxidation catalyst including a catalyst layer containing Pt and zeolite as a first catalyst, and a denitrification catalyst including a catalyst layer containing zeolite ion-exchanged with Cu, Co, or Fe ions as a second catalyst.

[0010] WO 2011 / 136034 describes the use of NH3 and NO in the off-gas. X and an off-gas treatment catalyst capable of treating NO in the off-gas flowing into the off-gas treatment catalyst. X and a flow gas control unit capable of controlling the ratio of NH3 to CO2.

[0011] U.S. Patent Application Publication Nos. 2003 / 0143142 and 2017 / 0334722 disclose NOx reduction in tail gas from nitric acid production. X The paper describes methods for reducing NO and N2O concentrations.

[0012] U.S. Patent Application Publication No. 2022 / 0323905 discloses NO in the off-gas stream of an ammonia-powered engine. X In one embodiment, the emissions treatment system includes a selective catalytic reduction catalyst (SCR catalyst) disposed on a substrate in fluid connection with the off-gas stream, a precious metal-containing oxidation catalyst disposed on a substrate upstream or downstream of the SCR catalyst and in fluid connection with the off-gas stream and the SCR catalyst, and optionally one or more sorbent components disposed on a substrate upstream and / or downstream of the SCR catalyst and in fluid connection with the off-gas stream and the SCR catalyst, wherein the sorbent components are capable of absorbing low temperature NO. XThe adsorbent is selected from a low temperature ammonia adsorber (LT-NA), a low temperature ammonia adsorber (LT-AA), a low temperature water vapor adsorber (LT-WA), and combinations thereof.

[0013] CN Patent No. 114412668 relates to an ammonia-fueled engine, in particular an ammonia-hydrogen fusion hybrid energy system and engine.

[0014] Chinese Patent No. 115773169 relates to an ammonia-fueled marine engine system and its exhaust aftertreatment system, which comprises a nitrous oxide reactor, a deoxygenation reactor, an ammonia oxidation catalytic reactor and an exhaust system arranged in series.

[0015] Chinese Patent No. 116877253 relates to an apparatus for treating off-gas from a marine engine with a high ammonia-diesel ratio, and a method for treating off-gas from a marine engine with a high ammonia-diesel ratio.

[0016] The focus of research to date has been on optimizing the combustion of ammonia itself, particularly with regard to energy yield and economic viability, but also with regard to the formation of undesirable nitrogen oxides. However, the NOx reduction in the combustion process X (i.e., NO and NO2) and N2O production cannot be sufficiently suppressed.

[0017] However, NO X Emissions of NO, NO and possibly other components that may be present in combustion gases (e.g. CO, HCN) should be avoided or at least reduced as far as possible in the interest of environmental and climate protection. Many developed countries have therefore imposed corresponding regulations.

[0018] Furthermore, combustion of hydrocarbons (CH4, natural gas, etc.) in the presence of NH3 produces off-gases that can contain hydrogen cyanide (HCN, hydrocyanic acid). Even small amounts of HCN are problematic because they are classified as highly toxic and correspondingly low limits for HCN emissions into the environment must be monitored. HCN-contaminated off-gases can, in principle, be purified by various means. Alkaline scrubbing operations can form and separate cyanides, but these must be disposed of as highly toxic compounds. Using specific oxidation catalysts based on precious metals, HCN can be converted to CO2, HO, N2, and various nitrogen oxides. However, this implies considerable procedural complexity and cost. For example, the formed nitrogen oxides must be decomposed in a further process step, for example, by selective catalytic reduction (SCR). Passage through specific catalysts, for example, based on TiO2, for the hydrolysis of HCN via HCN + HO → CO + NH3 has also been described. Subsequent further oxidation over a corresponding separate oxidation catalyst is also required in this case. Therefore, there is a need for a cleaning process for HCN-contaminated off-gas that is characterized by a simple and inexpensive mode of operation and low equipment costs. Furthermore, HCN should be converted in the process into non-toxic substances that do not require further treatment.

[0019] A further problem is the incomplete combustion of ammonia, which has the effect that the off-gas from an internal combustion engine powered by ammonia as fuel may contain a significant amount of unburned ammonia (so-called NH3 slip, NH3 breakthrough). The permissible limits for ammonia to be released into the atmosphere are relatively strict. In such cases, it is therefore necessary to ensure that the ammonia is oxidized to nitrogen before the off-gas can be released into the atmosphere. For this purpose, so-called ammonia slip catalysts (ASC) have been developed, which are typically based on noble metals from the platinum group (i.e., Ru, Rh, Pd, Os, Ir, Pt). Such catalysts are not only expensive but also have low selectivity (i.e., they only convert NH3 to NO Xor N2O), are susceptible to chlorine and chlorine compounds, which are almost unavoidable, especially in transport. For example, the air drawn in for combustion always contains some amount of sea salt, which is present in the atmosphere as an aerosol.

[0020] It is or may be present in the off-gas of an NH3-powered internal combustion engine for combustion-related reasons so that the off-gas can be discharged into the ambient air in compliance with all environmental regulations; - Nitrogen oxides (especially NO and NO X (i.e., NO and NO2) -excess NH3, and Other environmentally harmful components of the off-gas (e.g. CO or HCN), There is a need for suitable means to at least partially eliminate

[0021] The internal combustion engine, preferably a reciprocating piston engine, should be usable as a marine engine and therefore should be adapted to the special conditions of transport.

[0022] A special situation to be considered here is that resulting from the maximum efficiency of the combustion of NH3 to drive an internal combustion engine. Important parameters are not only the different compositions of the off-gas, but also in particular the pressure and temperature of the off-gas. These parameters affect the NO X and N2O removal strategies have been developed so far that may differ significantly from other off-gas parameters.

[0023] For example, in the industrial production of nitric acid (NH3), NO is reacted with water in an absorption tower to obtain nitric acid from it. X The oxidation is carried out intentionally up to NO. Special catalysts made from noble metals are used for the oxidation, and the reaction is often carried out at high pressure. The purpose of the combustion of NH3 here is to produce NO X The goal is to achieve a maximum yield of 1000 kJ / kg, and the typical water content in the off-gas ranges from about 1% to 3% by volume.

[0024] In contrast, in the case of combustion to power an internal combustion engine, NH3 is preferably oxidized only to the level of N2, so that a catalyst is typically not required; for example, if the internal combustion engine is a reciprocating piston engine, this reaction usually proceeds at relatively high pressures; in the case of a reciprocating piston engine based on the compression ignition principle, maximum internal cylinder pressures in the range of 20 to 100 bar are typically achieved before or during the combustion process. The purpose of combustion is to produce NO X and achieving a minimum yield of NO. Typical water contents in the off-gas are well above 3% by volume. For example, the combustion of pure NH in air with a residual oxygen content of 3 mol% results in more than 28 mol% water. The main purpose of the combustion of NH here is the generation of energy. Low levels of nitrogen oxides in the off-gas formed in the combustion are advantageous in this case because they reduce the level of nitrogen oxides in the flue gas and therefore require relatively small off-gas treatment systems to meet regulatory requirements regarding allowable emissions, or because sufficiently low residual concentrations can be achieved using known methods for nitrogen oxide reduction.

[0025] In contrast to conventional off-gas treatment systems, which are used, for example, in the case of off-gas from plants for the production of HNO3, the inventive combustion of NH3, preferably in a mixture with H2, offers special features accompanied by special measures.

[0026] On the one hand, a relatively low pressure of the off-gas stream, typically below 5 bar, and on the other hand a very high water content are essential. By "low pressure" we mean that the pressure drop may be too high when using conventional catalyst beds, such as those based on beds of particulate matter. Especially in the case of zeolitic materials, a high water content at high temperatures can lead to a gradual deactivation of the catalyst due to the hydrothermal load on the catalyst in the off-gas treatment system. Therefore, the maximum temperature should be limited. Apart from degradation, NO X The chemical reduction of N2O is little impaired by high water content, but the decomposition of N2O by decomposition and / or chemical reduction is severely impaired by high water content.

[0027] A further difference in the off-gas treated according to the present invention compared to the production of HNO3 is the relatively high NO2 content, which can be several thousand ppmv. X Content. NO X The content depends on the conditions in the combustion of NH3, in particular the NH3 content, any additional combustible gases present (H2 and / or CH4 (natural gas)) and the air ratio λ. Due to the high temperatures in the combustion up to 1000 °C and above, NO X also initially exists almost exclusively as NO, i.e., a very high proportion of NO and a very low proportion of NO2. Even as a result of favorable cooling, a small proportion of NO is converted to NO2 due to the slow rate of NO2 formation at high temperatures. This means that when the off-gas enters the off-gas treatment system, NO X The degree of oxidation (β), i.e., the total NO X This means that the molar fraction of NO in the catalyst (β = n(NO) / (n(NO) + n(NO)) is small, typically less than 5% by volume. This is because the desired selective catalytic NO X This means that reduction may proceed very poorly or slowly, in accordance with normal SCR, which in practice occurs at a slow rate.

[0028] These are the NO and NO absorbers that are released after leaving the "cold" state. X This is a fundamental difference from established off-gas cleaning in HNO3 systems, where the tail gas containing the gas is gradually heated under positive pressure, typically between 4 and 10 bar (thermodynamic NO X (The equilibrium is practically entirely on the side of NO2.) For example, the NO2 tail gas in HNO3 production before entering the corresponding off-gas treatment system X Oxidation levels are typically between 30% and 70% by volume, i.e., NO in very fast SCR. X This is close to the ideal stoichiometric ratio for reduction.

[0029] Therefore, high NO X Very low NO content XThe oxidation level and high water content coupled with the simultaneous low operating pressure (close to atmospheric pressure) pose particular challenges in this case to the effectiveness of the off-gas treatment system of the present invention. Additionally, there is the challenge or need to remove N2O, which is also present in the off-gas and cannot be reduced by conventional SCR processes based on V2O5 / TiO2 catalysts.

[0030] Therefore, the goals and resulting reaction products in the combustion of NH3 can be very different from one another.

[0031] In conventional plants for producing nitric acid, the off-gas is frequently, at relatively high pressure, -Relatively low content of NO X , -Relatively high percentage of NO2, - relatively high content of N2O, a relatively low content of water, and -In some cases, 0% of unburned NH3 (NH3 slip) It has.

[0032] In contrast, in an internal combustion engine, the off-gas is frequently released at relatively low pressures. -Relatively high content of NO X , - a relatively small proportion of NO2, - relatively low content of N2O, - a significantly high content of water, - possibly a non-negligible proportion of unburned NH3 (NH3 slip), -If NH3 is burned together with CH4 (natural gas), a non-negligible proportion of HCN will probably be produced. Includes:

[0033] These special circumstances can cause NO from the off-gassing X and N2O removal, which presents particular challenges.

[0034] NO from off-gas compared to existing industrial plants, so-called stationary plants XFurther challenges in the removal of NO and NO arise from the use of NH3-powered internal combustion engines on ships. Therefore, the systems are mobile rather than being fixedly installed and operated in one location. However, special requirements are imposed on mobile systems, e.g., regarding weight, size, safety, and shock stability. Furthermore, the operating mode of the internal combustion engine may spontaneously change, e.g., when switching from part-load to full-load operation in the case of heavy acceleration or braking. This also leads to the removal of NO from the off-gas. X and constitute a particular challenge in the removal of N2O. [Prior art documents] [Patent documents]

[0035] [Patent Document 1] Japanese Patent Publication No. 2023-026798 [Patent Document 2] International Publication No. 2011 / 136034 [Patent Document 3] US Patent Application Publication No. 2003 / 0143142 [Patent Document 4] US Patent Application Publication No. 2017 / 0334722 [Patent Document 5] US Patent Application Publication No. 2022 / 0323905 [Patent Document 6] Chinese Patent No. 114412668 [Patent Document 7] Chinese Patent No. 115773169 [Patent Document 8] Chinese Patent No. 116877253 [Non-patent literature]

[0036] [Non-Patent Document 1] H.Kobayashi et al., Proceedings of the Combustion Institute 37(2019)109-133;D.Erdemir et al.,Int J.Energy Res.2021,45,4827-4834;C.Tornatore et al.,Frontiers in Mechanical Engineering,2022,8,Article 944291 [Non-patent document 2] A. Boretti et al., ACS Energy Lett.2022,7,2557-2564 [Non-patent document 3] Ch.Lhuillier et al., 14th International Conference on Engines&Vehicles,2019,Capri;S.Mashruk et al.,Chemical Engineering Transactions,89,2021;S.Mashruk et al.,Combustion and Flame 244(2022)112299 [Non-patent document 4] Ch. Mounaim-Rousselle et al., Energies 2021,14,4141 [Non-patent document 5] Y.K. Park, Chemical Engineering Journal, Vol. 461, 141958 Summary of the Invention

[0037] The objective of the present invention is to determine the NO in the off-gas obtained from an NH3-driven internal combustion engine. X The objective of the present invention is to reduce the content of NO (i.e., NO and NO), NO, and, if necessary, NH, CO, and / or HCN. This should be possible in an economically viable manner and allow optimal utilization of NH. Catalysts based on platinum group metals should be avoided as much as possible. Furthermore, the off-gas treatment of the present invention is suitable for a wide range of combustion-fuel-air ratios, i.e., very lean (relatively high NO content, relatively low NO Xcontent, relatively low NH3 slip) to near stoichiometry (relatively low N2O content, relatively high NO X The objective is to achieve the best possible utilization of the fuel in an advantageous manner under a wide range of conditions, including the use of breakthrough fuel.

[0038] This object is achieved by the subject matter of the claims.

[0039] The present invention provides (i) an internal combustion engine configured to be powered by the combustion of NH3, the internal combustion engine being mounted on the marine vessel and configured to propel the marine vessel; (ii) N2, H2O, and NO are produced by combustion of NH3 in an internal combustion engine. X and NO in off-gas containing NO X and an off-gas treatment system configured to reduce the content of N2O, an N2O decomposition catalyst configured to decompose N2O and / or an N2O reduction catalyst configured for chemical reduction of N2O by a reducing agent, and -NO by reducing agents X configured for the chemical reduction of NO X reduction catalyst, an off-gas treatment system including: The present invention relates to an apparatus comprising:

[0040] The present invention also relates to a method for detecting NO in the off-gas of an NH3-driven internal combustion engine installed on a ship and used to propel the ship. X and a method for reducing the content of N2O, the method comprising: (a) burning NH3 (optionally in a mixture with one or more further combustible gases, e.g., H2, CH4) to power said internal combustion engine, and producing N2, HO, NO, with or without HCN; X generating an off-gas exiting the internal combustion engine comprising NO and N2O; (b) transporting off-gas from the internal combustion engine to an off-gas treatment system; (c) The NO content in the off-gas is (c1) decomposing N2O via an N2O decomposition catalyst; and / or (c2) chemically reducing N2O using a reducing agent via an N2O reduction catalyst; and (d)NO X NO by reducing agents via reduction catalysts X NO in the off-gas by chemical reduction of X By reducing the content, reducing the Includes:

[0041] The order of steps (c) and (d) may be as desired, and in accordance with the present invention all options are included, from sequential in time in any order to simultaneous, or a mixture thereof.

[0042] Surprisingly, NO X It has been found that the breakthrough fuel (NH3 slip) can be advantageously used in an off-gas treatment plant as a reducing agent for the chemical reduction of NO, if desired. The amount of NH3 that may need to be oxidized to keep emissions low is thereby advantageously reduced, which increases fuel utilization.

[0043] The off-gas treatment systems of the present invention may be the same or different according to a given functionality or multi-functionality, and may be present in a common or separate reaction zone (catalyst bed); - N2O reduction catalyst and / or N2O decomposition catalyst, and -NO X reduction catalyst, At least includes.

[0044] In a preferred embodiment, the off-gas treatment devices of the present invention may be the same or different, and may be present in a common or separate reaction zone (catalyst bed), according to a given functionality or multifunctionality. -N2O reduction catalyst, -N2O decomposition catalyst, and -NO X reduction catalyst, Includes:

[0045] In a preferred embodiment, the off-gas treatment system of the present invention further comprises at least one additional catalyst, or a catalyst selected from the group consisting of N2O reduction, N2O decomposition, or NO2O decomposition. X One of the reduction catalysts is -NH3 oxidation catalyst, -HCN decomposition catalyst, and -CO oxidation catalyst, The at least one further functionality selected from the following is satisfied:

[0046] The NH3 oxidation catalyst preferably reduces the proportion of unburned NH3 in the off-gas (NH3 slip) to a level that is lower than the NO2 content in the off-gas treatment system. X and / or the demand for NH as a reducing agent for N2O is greater than the demand for NH3, so that the off-gas, after passing through steps (c1) and / or (c2) and (d), still contains residual amounts of NH3 that should not or should not be released to the environment. These residual amounts of NH3 can then be destroyed by oxidation of NH3 using a downstream NH3 oxidation catalyst.

[0047] The HCN decomposition catalyst is preferably used when the fuel contains hydrocarbons (CH, natural gas, etc.) in addition to NH3, and the off-gas formed during combustion contains a certain amount of HCN. The resulting HCN can then be decomposed (removed) using the HCN decomposition catalyst by hydrolysis of HCN and oxidation of the hydrolysis products (hydrolysates) formed during the process, namely NH3 and CO, preferably NO. X and N2O are present in the off-gas.

[0048] Surprisingly, each of them contains more molar amounts of NO than the molar amount of HCN. XIt has been found that HCN in a water-containing off-gas, which simultaneously contains HCN and N2O, can be decomposed to N2, HO and CO2 by passing the off-gas over a package of catalyst pellets containing a transition metal-containing zeolite catalyst, for example, an iron-containing zeolite material of the BEA structure type, at a temperature of 300 to 600°C (preferably 350 to 550°C).

[0049] In contrast to known methods, the complete removal of HCN, i.e., its conversion into non-toxic substances, can thus be achieved in a one-stage process, i.e., in one process step without the use of expensive noble metal catalysts. X and NO to eliminate N2O X and NH3 for the reduction of N2O, and HCN, NO for N2O X It is further possible to add CO or hydrocarbons, such as CH or propane, for reduction to the N2O- and N2O-containing off-gas. In this case, the amount of reducing agent is determined by the ratio of N2O and NO X In each case, the molar starting amount of NO should be reduced by the molar amount of HCN present in the off-gas. If an excess amount of NO is present in the off-gas and is reduced with NH or CO or hydrocarbons, the NO X The content should in any case be reduced to 0 (or close to 0) by NH3. If CO or hydrocarbons are used as additional reductants, CO emissions can be eliminated by using an additional CO oxidation catalyst downstream of the zeolite catalyst.

[0050] A CO oxidation catalyst is preferably used when (i) hydrocarbons (CH, natural gas, etc.) are used as a reductant for NO, and / or (ii) an HCN decomposition catalyst is used to decompose HCN and CO is present in the decomposition products. Any CO obtained in each case can then be decomposed by oxidation to CO using a downstream CO oxidation catalyst.

[0051] If the off-gas treatment system of the present invention includes an NH3 oxidation catalyst, it may be preferred, according to the present invention, to initially condition the off-gas with a temperature controller in the off-gas treatment system to a different temperature than when it enters the off-gas treatment system, so that the NH3 oxidation catalyst can demonstrate its effectiveness in an optimized manner. Thus, in a preferred embodiment, the off-gas treatment system of the present invention further comprises one or more temperature controllers.

[0052] For purposes of explanation, "and / or" means either "or" or "and," e.g., "A and / or B" has three meanings: (i) only A but not B, (ii) only B but not A, and (iii) both A and B.

[0053] For purposes of illustration, "NO X " includes nitric oxide (NO) and nitrogen dioxide (NO2), but does not include nitrous oxide (N2O).

[0054] Catalysts speed up certain chemical reactions by lowering their activation energy.

[0055] The apparatus of the present invention is configured to carry out the method of the present invention. All preferred embodiments of the method of the present invention described by steps (a), (b), (c1), (c2) and (d) are equally applicable to an apparatus configured according to the present invention or parts thereof configured to carry out these steps. Thus, the internal combustion engine of the present invention is configured to carry out step (a), and the off-gas treatment system of the present invention is configured to carry out steps (c1) and / or (c2) and (d). The off-gas treatment plant is configured to treat the off-gas produced in the internal combustion engine, in particular to reduce the NO content in the off-gas and the NO content in the off-gas. X The apparatus of the present invention is further configured to reduce the content of toluene, such that the apparatus is configured to perform step (b), and the internal combustion engine and the off-gas treatment system are particularly configured to be connected to each other so that the off-gas produced in the internal combustion engine is transferred to the off-gas treatment system.

[0056] Unless otherwise stated, all numbers in ppm are by volume, i.e., ppmv. All percentages are by volume, i.e., vol. % with respect to the gas composition, unless otherwise stated. All other percentages are by weight, i.e., wt. % unless otherwise stated.

[0057] Steps (a) and (b) of the method of the present invention are performed consecutively in alphabetical order, followed by steps (c) and (d) in essentially any order, and the apparatus of the present invention is accordingly configured. Thus, step (c) can be performed before or after step (d), or simultaneously with step (d). A partially simultaneous mixed form is also possible. This is particularly relevant when one and the same catalytic material can catalyze multiple reactions. Such an embodiment is particularly preferred according to the present invention. According to the present invention, these reactions may occur simultaneously, but the kinetics of each reaction may vary, so that a first reaction may finish earlier or reach a higher conversion rate than a second reaction proceeding in parallel. Thus, the NO decomposition catalyst and / or the NO reduction catalyst may be configured to separate NO from the NO in the off-gas flow direction. X It can be located upstream or downstream of the reduction catalyst, but a mixed regime can be achieved in that one and the same catalytically active material catalyzes two or more of these reactions simultaneously.

[0058] Step (c1), i.e., decomposition of N2O via an N2O decomposition catalyst, and step (c2), i.e., chemical reduction of N2O by a reducing agent via an N2O reduction catalyst, are considered separately for purposes of explanation, but both serve the common purpose of reducing the N2O content in the off-gas.

[0059] Steps (c1), (c2) and (d) may likewise be performed in any order, although partial simultaneity and hybridization are also possible in this regard.

[0060] In a preferred embodiment, the method of the present invention comprises steps (a), (b), (c1) and (d), steps (a), (b), (c2) and (d), or steps (a), (b), (c1), (c2) and (d), or the apparatus of the present invention is configured accordingly.

[0061] In a preferred embodiment, the off-gas passes through the steps of the method of the present invention, or through correspondingly configured parts of an apparatus constructed according to the present invention, in one of the following sequences:

[0062] (i)(a) →(b) →(c1) →(d); (ii) (a) → (b) → (d) → (c2); (iii)(a)→(b)→(d)→(c2)→(c1); (iv)(a)→(b)→(d)→(c1+c2); or (v)(a)→(b)→(d)→(c1). By (c1+c2) it is meant that both step (c1) and step (c2) are performed, but the execution of these two steps (c1) and (c2) is at least partially simultaneous, i.e. both steps proceed in parallel or the apparatus of the present invention is configured accordingly.

[0063] Between these steps there may be further steps not explicitly specified.

[0064] Surprisingly, it has been found that NH3-powered internal combustion engines can be advantageously operated with a relatively small degree of NH3 slip from the engine into the off-gas (NH3 breakthrough). This can be achieved by increasing the air ratio λ, which typically involves increasing the amount of NO in the off-gas. X and / or increased concentrations of NO. When pure ammonia is used as fuel, NO X The formation is expected to have a maximum in the lean range (at an equivalence ratio of about 1 / 1 = 0.8), depending on the air ratio λ. When λ is relatively low, the oxygen supply contributes to the NO X When λ is relatively high, the combustion temperature limits the formation of NOX This limits the formation of NO, and instead the N2O content may increase. As the air ratio increases, NH3 slip still occurs, but it is no longer as significant. In the case of such operation of an internal combustion engine, the excess NH3 can be effectively oxidized by the use of an NH3 oxidation catalyst, preferably an oxidation-active zeolite catalyst. It is therefore possible to eliminate the need for precious metal-containing NH3 oxidation catalysts, especially those containing platinum group metals (i.e., Ru, Rh, Pd, Os, Ir, Pt), which is particularly advantageous in ships. This is because such NH3 oxidation catalysts are expensive and can be used when the NH3 concentration is high (i.e., the oxidation of NH3 also produces secondary NO). X and N2O and also forms N2O and N2), and is susceptible to poisoning by chlorine from marine air.

[0065] For purposes of this description, what is meant by "platinum group metal-free" is the essential absence of platinum group metals (i.e., Ru, Rh, Pd, Os, Ir, Pt), although analytically detectable minimal trace amounts of platinum group metals are possible.

[0066] For purposes of this description, what is meant by "noble metal-free" is essentially the absence of precious metals, although analytically detectable trace amounts of precious metals are possible.

[0067] The present invention's use of NH3 as a fuel for internal combustion engines is better when the air-fuel mixture burns much leaner (or secondary air is supplied), and NH3 slip is lower, which is related to the lower N2O and NO X associated with higher formation of

[0068] The solution of the present invention makes it possible to operate (dual fuel) internal combustion engines on ships in such a way that NH3 slip (in the quasi-steady state operating mode of the ship) can be minimized by using lean burn characteristics or secondary air.

[0069] If excess NH3 oxidation is required, it is possible to use, for this purpose, preferably iron- or copper-containing zeolite catalysts with sufficiently high NH3 oxidation activity according to the present invention. Therefore, the use of noble metal-containing NH3 oxidation catalysts, in particular NH3 oxidation catalysts containing platinum-based metals, is not required and can be omitted.

[0070] Furthermore, it has surprisingly been found that the catalytic decomposition of NO in the off-gas of an NH3-powered internal combustion engine can be advantageously utilized, particularly when the off-gas treatment system has two reaction zones arranged in series, each of which independently contains an iron- or copper-containing zeolite catalyst, and the two reaction zones are preferably separated from each other by at least one metering / injection system for at least one reducing agent. X It has been found that the first reaction zone in a rich environment performs a distinct function as an N2O decomposition catalyst when the NH3 slip of the internal combustion engine is low. In contrast, when the NH3 slip is high, the first reaction zone functions as a catalyst for decomposing N2O and NO X gives additional catalyst volume for the chemical reduction of and oxidation of NH3.

[0071] In step (a) of the method of the invention, NH3 is combusted to drive an internal combustion engine, or the device of the invention is correspondingly configured, which generates heat by a combustion process. The combustion of the fuel generates heat with further driving of machinery. This expression includes engines for propulsion of ships. In the internal combustion engine, NH3 is oxidized with O2 (preferably from air) with the aim of producing, inter alia, N2 and HO as main products.

[0072] For example, in the production of nitric acid, X A system in which NH3 is oxidized with O2 to produce nitrogen compounds having the formula (I) as the main product is not an internal combustion engine in the context of this invention.

[0073] Combustion of NH3 means the oxidation of NH3 with O2; according to the present invention, this reaction does not have to be complete, so that the off-gas may contain residual unburned (unoxidized, unconverted) NH3 (NH3 slip, NH3 breakthrough), or the device of the present invention may be configured accordingly. The same applies if NH3 is not burned in pure form but together with further combustible gases, in particular H2 and / or CH4 (natural gas). The O2 used for combustion can be used in the form of combustion air, which may be enriched with O2.

[0074] Higher amounts of NH3 slip are undesirable, since according to the invention this requires special measures to prevent NH3 leakage above the maximum permissible limit, in particular the use of an NH3 oxidation catalyst (ammonia slip catalyst, ASC) intended to oxidize the NH3 destroyed by O2 to give H2O and N2.

[0075] Preferably, according to the present invention, NH3 is combusted in step (a) or the internal combustion engine is configured so that the off-gas has an NH3 content of at most 35000 ppmv, preferably at most 30000 ppmv, more preferably at most 25000 ppmv, even more preferably at most 20000 ppmv, most preferably at most 15000 ppmv, especially at most 10000 ppmv.

[0076] Preferably, according to the present invention, NH3 is combusted in step (a) or the internal combustion engine is configured so that the off-gas has an NH3 content of at most 9000 ppmv, preferably at most 8000 ppmv, more preferably at most 7000 ppmv, even more preferably at most 6000 ppmv, most preferably at most 5000 ppmv, especially at most 4000 ppmv.

[0077] Preferably, according to the present invention, NH3 is combusted in step (a) or the internal combustion engine is configured so that the off-gas has an NH3 content of at most 3500 ppmv, preferably at most 3000 ppmv, more preferably at most 2500 ppmv, even more preferably at most 2000 ppmv, most preferably at most 1500 ppmv, especially at most 1000 ppmv.

[0078] Suitable methods for reducing NH3 slip in an internal combustion engine are known to those skilled in the art. In particular, NH3 slip can be achieved by increasing the air ratio λ. Such an increase in the air ratio λ reduces the NO2 content in the off-gas of the internal combustion engine. X and / or N2O content, which may be accompanied by an increase in the NH3 vs. NO X Given the favorable ratio of NO and possibly N2O, the destroyed NH3 is NO X , and if necessary, act as a reducing agent for the chemical reduction of N2O. Therefore, all these gases can be simultaneously decomposed in the off-gas treatment system, and the gas leaving the off-gas treatment system will contain only very small amounts of harmless NH3, NO X , and N2O, and are therefore acceptable in accordance with the present invention.

[0079] The internal combustion engine preferably has an off-gas NH3:NO of at most 5.0, preferably at most 4.5, more preferably at most 4.0, even more preferably at most 3.5, most preferably at most 3.0, especially at most 2.5. X The molar ratio of

[0080] The internal combustion engine preferably has an off-gas NH3:NO of at most 2.3, preferably at most 2.1, more preferably at most 1.9, even more preferably at most 1.7, most preferably at most 1.5, especially at most 1.3. X The molar ratio of

[0081] According to the invention, NH3 is preferably combusted in a mixture with H2 or a fossil fuel, such as CH4, or the device of the invention is configured accordingly.

[0082] In step (a) of the method of the present invention, NH3 is combusted to drive an internal combustion engine, or the device of the present invention is configured accordingly.

[0083] An "internal combustion engine" (heat engine) within the context of the present invention is in particular a combustion engine, preferably a piston heat engine having an internal combustion engine such as a reciprocating piston engine or a rotary piston engine.

[0084] The internal combustion engine preferably comprises or is a reciprocating piston engine, in either case preferably with compression ignition.

[0085] Step (b) In step (b) of the method of the present invention, the off-gas is transferred to an off-gas treatment system, i.e., from an internal combustion engine, or the device of the present invention is correspondingly configured. In the off-gas treatment system of the present invention, steps (c) and (d) of the method of the present invention are performed, or the device of the present invention is correspondingly configured. For this purpose, the off-gas treatment system comprises an N2O decomposition catalyst for decomposing N2O in step (c1) and / or an N2O reduction catalyst for chemically reducing N2O with a reducing agent in step (c2), and a N2O reduction catalyst for chemically reducing N2O with a reducing agent in step (d). X for the chemical reduction of NO X It is equipped with a reduction catalyst.

[0086] The off-gas treatment system of the present invention may further comprise at least one additional catalyst, or may be used to treat N2O reduction, N2O decomposition, or NO X If one of the reduction catalysts fulfills at least one further functionality, at least one of the following steps (e1) to (e4) is preferably further carried out in the off-gas treatment system of the present invention.

[0087] (e1) adjusting the off-gas temperature in at least one temperature control device preferably located in the off-gas treatment system, preferably located upstream of the NH3 oxidation catalyst in the flow direction of the off-gas; (e2) reducing the NH content in the off-gas by oxidation with an oxidizing agent via an NH oxidation catalyst, the oxidizing agent preferably comprising O; (e3) reducing the HCN content in the off-gas by hydrolysis and oxidation of the hydrolysate with an oxidizing agent via an HCN decomposition catalyst, wherein the oxidizing agent is preferably NO X and / or N2O, and (e4) Reducing the CO content in the off-gas by chemical oxidation with an oxidant via a CO oxidation catalyst, the oxidant preferably comprising O2.

[0088] Step (c) In step (c) of the method of the present invention, the NO content in the off-gas is reduced, or the apparatus of the present invention is configured accordingly, which can be achieved by decomposition of NO via an NO decomposition catalyst in step (c1) and / or chemical reduction of NO with a reducing agent via an NO reduction catalyst according to (c2).

[0089] The decomposition of N2O forms N2 and O2 according to the following empirical reaction:

[0090] 2 N2O → 2 N2 + 1 O2. Therefore, decomposition of N2O means decomposition into N2 and O2. An "N2O decomposition catalyst" in the context of the present invention catalyzes the decomposition of N2O. The achievable decomposition of N2O by catalytic decomposition depends not only on the type of N2O decomposition catalyst, i.e., its chemical nature and physical composition, and the existing pressure and temperature conditions, but also, in particular, on the selected space velocity, i.e., the ratio of the off-gas volumetric flow rate to the catalyst volume. However, the catalytic activity of an N2O decomposition catalyst need not be limited to this reaction only. For example, according to the present invention, an N2O decomposition catalyst may be used for, for example, the chemical reduction of N2O and / or the decomposition of NO2O. XIt is quite possible, and indeed preferred, that further reactions, such as the chemical reduction of , can also be catalyzed. Whether such further reactions actually occur depends on the conditions of the individual case, in particular the type of catalyst, and the kinetics of any parallel processes, such as the presence or amount of reducing agent and the presence or amount of other co-reactants.

[0091] Chemical reduction of N2O by reducing agents forms different reaction products depending on the reducing agent.

[0092] In the case of the NH3 reducing agent preferred according to the invention, the chemical reduction of N2O forms, inter alia, N2 and H2O, for example as follows:

[0093] 3 N2O + 2 NH3 → 4 N2 + 3 H2O or 4 N2O + 4 NH3 + O2 → 6 N2 + 6 H2O or co-reduction with NO to 2 NO + N2O + 2 NH3 → 3 N2 + 3 H2O. In the case of hydrocarbons, which are likewise preferred as reducing agents according to the invention, the chemical reduction of N2O forms, inter alia, CO and H2O, for example as follows:

[0094] (2n+1)N2O+C n H 2n+2 →(2n+1)N2+n CO+(n+1)H2O or CO2 and H2O as follows 4n NO+C n H 2n+2 → 4n N2 + n CO2 + 2n H2O. CO is also preferred as a reducing agent according to the invention, which can further react with N2O to give CO2, for example according to the following:

[0095] N2O+CO→N2+CO2.

[0096] An "N2O reduction catalyst" in the context of the present invention catalyzes the chemical reduction of N2O by a reducing agent. However, the catalytic activity of an N2O reduction catalyst need not be limited to this reaction alone. For example, according to the present invention, an N2O reduction catalyst may be used to, for example, decompose N2O and / or reduce NO X It is quite possible, and indeed preferred, that further reactions, such as the chemical reduction of , can also be catalyzed. Whether such further reactions actually occur depends on the conditions of the individual case, in particular the type of catalyst, and the kinetics of any parallel processes, such as the presence or amount of reducing agent and the presence or amount of other co-reactants.

[0097] Step (d) In step (d) of the method of the present invention, NO in the off-gas X The content is NO X NO by reducing agents via reduction catalysts X or the device of the present invention is configured accordingly.

[0098] Here, nitrogen oxides present in the off-gas, especially NO X Selective catalytic reduction (SCR) of NO X A reduction catalyst is preferred, which is NO X The reduction catalyst mainly X This means that the catalyst catalyzes the oxidation of NH3 by the free oxygen (O2) present in the off-gas, but does not catalyze, or secondarily catalyze, the oxidation of NH3 by the free oxygen (O2) present in the off-gas.

[0099] NO by reducing agents X The chemical reduction of forms different reaction products depending on the reducing agent. In the case of NH3 reducing agent preferred according to the present invention, NO X The chemical reduction of, in particular, NO X Depending on the type of reduction catalyst and the ratio of NO to NO2, N2 and H2O are formed, for example:

[0100] 4 NH3+2 NO+2 NO2→4 N2+6 H2O (high speed SCR) 4 NH3+4 NO+O2→4 N2+6 H2O (normal SCR) 8 NH3+6 NO2→7 N2+12 H2O(NO2SCR).

[0101] A typical selective catalytic reduction is called fast SCR and is much faster than regular SCR or NO2 SCR.

[0102] In the context of the present invention, "NO X "Reduction catalyst" is a reducing agent that reduces NO X However, NO X The catalytic activity of the reduction catalyst is not necessarily limited to this reaction. For example, according to the present invention, NO X The reduction catalyst may be, for example, a catalyst for decomposing NO, chemically reducing NO, and / or reducing NO. X It is quite possible, and indeed preferred, that further reactions can be further catalyzed, such as the establishment of an equilibrium or the selective oxidation of excess NH by free O. Whether such further reactions actually occur depends on the conditions of the individual case and the kinetics of any parallel processes, such as the presence or amount of reducing agent and the presence or amount of other co-reactants.

[0103] catalyst N2O decomposition catalysts are known per se and a wide variety of substance classes can be used. For decomposing N2O into N2 and O2, N2O decomposition catalysts with high catalytic activity in the temperature range of, for example, 350 to 600°C are preferred.

[0104] According to the present invention, preferred examples of NO decomposition catalysts are metal-containing zeolite catalysts, such as copper or cobalt, or especially iron-containing zeolite catalysts, noble metal catalysts, or transition metal oxide catalysts, such as cobalt oxide-containing catalysts. Examples of suitable catalysts are described, inter alia, by Kapteijn et al. in Appl. Cat. B: Environmental 9 (1996), 25-64, in US-A-5,171,553, in Actes du 2ieme Congres International sur la Catalyse, Technip, Paris 1961, 1937-1953, and in WO-A-01 / 58,570. When an iron-containing zeolite catalyst is used in the first catalyst bed, NO still present in the gas is decomposed. X As expected, Kogel et al. in Catal. Comm. 2 (2001) 273-276 reported that the N2O / NO X The ratio described accelerates the desired NO decomposition through an activation effect (co-catalytic effect).

[0105] Further examples of N2O decomposition catalysts preferred according to the present invention are X Such an N2O decomposition catalyst is referred to for the purposes of this description as "NO X These catalysts contain one or more catalytically active compounds of elements selected from groups 5 to 11 of the Periodic Table of the Elements (PTE). Compounds of elements from groups 9 to 11 of the PTE are particularly preferred. Among these, compounds of the elements Co, Pt, Pd, Ir, Rh, Ni and / or Cu are preferred, preferably Co, Rh, Ni and / or Cu, and here especially Co or Rh. Preference is given to catalysts for the decomposition of NO which are based on noble metals, preferably supported on refractory oxides, or on mixtures of transition metal oxides, in particular mixed oxides or simple transition metal oxides, in both cases in supported form or, preferably, as unsupported catalysts.

[0106] The catalytically active compounds themselves may be metal and / or oxide compounds, the latter either in the form of a single oxide or in the form of binary, ternary, or multi-component mixed oxides of different structural types, such as perovskites or spinels. These are described, for example, in Catalysis Letters 35 (1995) 372-382, Applied Catalysis 73 (1991) 165-171, Catal. Rev.-Sci. Eng.; 34 (4), 409-425 (1992) or Actes du 2ieme Congres International sur la Catalyse 97 (1961) 1937-1953. Mixtures of different catalytically active compounds may also be used. Particularly preferred examples of catalytically active compounds are metallic rhodium, rhodium oxides such as RhO2 or Rh2O3, CoO, Co2O3, Co-containing spinels such as Co3O4, CuCo, etc. 3-x O4, or Co-containing perovskites such as LaCoO3 or Co-containing perovskites substituted at the A and B sites.

[0107] The catalytically active compounds may be present in the catalyst in pure form or may be applied to or mixed with a suitable support material, in the former case these compounds are so-called unsupported catalysts which may contain, in addition to the active compounds, binders or other production-related additives known to those skilled in the art, such as plasticizers, pore formers, fiber reinforcing agents or compaction aids.

[0108] Methods for producing such catalysts are known to those skilled in the art. In the case of "supported catalysts," the catalytically active compound is applied to a support material. As a result, the catalytically active compound is dispersed and stabilized against both mechanical and thermal stresses. Methods for producing such catalysts are also known to those skilled in the art. The support material is preferably a refractory oxide such as SiO, TiO, ZrO, or AlO, or a mixture of two or more of these, or a material that itself has a certain catalytic activity for N2O decomposition, such as MgO, zeolite, hydrotalcite, or a mixture of two or more of these. It is preferable to use a catalyst that is essentially free of zeolite, preferably containing less than 15% (by weight) of zeolite, especially less than 5% (by weight) of zeolite, if any.

[0109] Preferred support materials for Rh-containing compounds are ZrO2, TiO2, Al2O3, hydrotalcite, or zeolites, such as those of the MFI structure type. These are described, for example, in Chemical Engineering and Technology 24 (2001) 281-285 or Catalysis Today 35 (1997) 113-120. Particularly preferred supports for Rh-containing compounds are ZrO2, TiO2, and hydrotalcite. The Rh content of these catalysts is preferably 0.1% to 10% by weight, more preferably 0.5% to 5% by weight. In addition to Rh, the Rh-containing catalyst more preferably also contains CeO2. The proportion of CeO2 is preferably 5% to 50% by weight, particularly 10% to 30% by weight.

[0110] A preferred support for the Co-containing compound is a zeolite, or a preferred support comprises magnesium oxide. In the case of zeolites, Si-rich structural types such as MFI, BEA, FER, MEL, or MOR are particularly preferred. The preparation of such Co-doped zeolites is known to those skilled in the art. The magnesium oxide support can be pure MgO or an MgO-containing compound, such as hydrotalcite. Such catalysts are described, for example, in Appl. Catal. B: Environmental 7 (1996) 397-406 or Appl. Catal. B: Environmental 13 (1997) 69-79.

[0111] Particularly preferred are catalysts consisting essentially of at least one magnesium oxide compound and at least one cobalt oxide compound, where the content of the cobalt oxide compound is in the range of 0.1% to 50% by weight, and the content of the magnesium oxide compound is in the range of 50% to 99.9% by weight, in each case based on the total mass of the catalyst, and at least 30% of the Co atoms present in the catalyst are chemically trivalent. Such catalysts and their preparation are described in EP 1 257 347. Also particularly preferred when an oxidic Co compound is used as the active component are catalysts having a support consisting of at least 50% (by weight) MgO or a mixed oxide consisting of at least 50% by weight MgO, to which a cerium oxide functional layer is applied. Such catalysts and their preparation are described in DE 10 2007 038 711 A1.

[0112] The NO decomposition catalysts can be in the form of shaped bodies of any size and geometry, preferably with a high surface area to volume ratio, which traverses them to generate a minimum pressure drop. All geometries known in catalysis are typical, such as cylinders, hollow cylinders, perforated cylinders, rings, crushed granules, trilobes, or honeycomb structures.

[0113] NO reduction catalyst and NO XReduction catalysts are likewise known per se and a wide variety of substance classes can likewise be used, examples of which are metal-containing zeolite catalysts, such as copper- or cobalt-containing zeolite catalysts, or in particular iron-containing zeolite catalysts, or noble metal catalysts, or catalysts used in the known SCR (selective catalytic reduction) processes.

[0114] In a particularly preferred embodiment according to the invention, the off-gas comprises NH3 and the off-gas treatment system is configured to reduce the NH3 content in the off-gas. To this end, the off-gas treatment system preferably comprises an NH3 oxidation catalyst configured for the chemical oxidation of NH3 by O2, preferably configured for the chemical oxidation of NH3 by O2 to obtain N2 and HO.

[0115] Preferably, an N2O decomposition catalyst and / or an N2O reduction catalyst and / or an NO X The reduction catalyst and / or the NH3 oxidation catalyst independently comprise a zeolitic material, preferably a zeolite comprising a transition metal (including a lanthanide), particularly iron, cobalt, or copper, more preferably an iron- or copper-containing zeolite, even more preferably an iron- or copper-containing zeolite, independently of the MFI, BEA, FER, MOR, FAU, AEI, and / or MEL structural type.

[0116] Preferably, an N2O decomposition catalyst and / or an N2O reduction catalyst and an NO X Both of the reduction catalysts independently comprise a zeolitic material, preferably a zeolite containing a transition metal (including a lanthanide), particularly iron, cobalt, or copper, more preferably an iron- or copper-containing zeolite, even more preferably an iron- or copper-containing zeolite, independently of the MFI, BEA, FER, MOR, FAU, AEI, and / or MEL structural type.

[0117] These may be different catalysts or the same catalyst. The iron-containing zeolite catalyst particularly preferably used according to the present invention essentially contains one or more iron-containing zeolites, preferably more than 50 wt.%, in particular more than 70 wt.%. For example, in addition to Fe-ZSM-5 zeolite, further iron-containing zeolites, such as iron-containing zeolites of the FER type, may be present in the catalyst used according to the present invention.

[0118] Furthermore, the catalysts used according to the invention may contain further additives known to those skilled in the art, such as binders.

[0119] The iron content of the zeolites preferably used can be up to 25% based on the mass of the zeolite, but is preferably between 0.1% and 10%.

[0120] The method of the present invention also includes the use of zeolites in which the lattice aluminum is partially isomorphously substituted by one or more elements, for example, one or more elements selected from B, Be, Ga, Fe, Cu, Cr, V, As, Sb, and Bi. Zeolites in which the lattice silicon is isomorphously substituted by one or more elements, for example, one or more elements selected from Ge, Ti, Zr, and Hf. The precise details of the formation or structure of the zeolites preferably used according to the present invention are described in Atlas of Zeolite Structure Types, Elsevier, 4th revised edition 1996, which is expressly incorporated herein by reference.

[0121] In the process of the present invention, it is very particularly preferred to use zeolite catalysts treated with steam ("steam catalysts"). Such treatment dealuminates the zeolite lattice and is known to those skilled in the art. These hydrothermally treated zeolite catalysts are notable for their particularly high activity in the process of the present invention. It is preferred to use hydrothermally treated zeolite catalysts which are supported with iron and have an extra-lattice aluminum to lattice aluminum ratio of at least 1:2, preferably between 1:2 and 20:1.

[0122] NO and NO X Preferred catalyst for the decomposition of

[0123] The N2O decomposition catalyst, N2O reduction catalyst, and NO X The reduction catalyst preferably contains a zeolitic material ("zeolite") that independently comprises at least one transition metal (atomic numbers 21-30, 39-48, 57-80, 89-112) and / or at least one lanthanoid (atomic numbers 57-71, also referred to as "lanthanides"). For purposes of description, transition metals and lanthanoids are collectively referred to as "transition metals" for simplicity. Preferred transition metals are iron ("Fe zeolites"), copper ("Cu zeolites"), and cobalt ("Co zeolites"). Iron-containing zeolitic materials (i.e., Fe zeolites) are particularly preferred and may contain, or include, not only iron, but also other transition metals, such as manganese, vanadium, chromium, nickel, or mixtures thereof.

[0124] The zeolitic material of the present invention preferably has high hydrothermal stability. SiO2-rich zeolites, known as "high silica zeolites," are particularly preferred, which have a high ratio of [SiO2] to [AlO2 - ] units and thus a molar Si / Al ratio of at least 8, preferably at least 9, more preferably at least 10, even more preferably at least 11, most preferably at least 12, especially at least 13.

[0125] The zeolitic materials preferred according to the present invention essentially have a zeolitic structure of the BEA, MFI, MOR, MEL or FER structure type, more preferably the MFI and BEA structure type, more preferably the BEA structure type. In the case of the MFI structure type, the ZSM-5 type is particularly preferred. Further details of the structure types of zeolitic materials and their structural nomenclature can be found in Atlas of Zeolite Structure Types, Elsevier, 4th revised edition 1996.

[0126] Particularly preferred N2O decomposition catalysts, N2O reduction catalysts or NOX The reduction catalyst independently contains at least 50 wt. % Fe zeolite, preferably at least 70 wt. % Fe zeolite, based on the total weight of the zeolitic material, and a single structure type or several structure types may be present. In a preferred embodiment, in addition to the Fe-BEA zeolite, another Fe zeolite of a different structure type, preferably an Fe-MOR zeolite, is present.

[0127] The loading (doping) of the zeolite material with a transition metal / lanthanide can be carried out by related methods for loading or doping zeolites with transition metals / lanthanides known to those skilled in the art. The loading preferably proceeds from commercially available zeolite material in H form or, preferably, NH form, by ion exchange, aqueous phase, or solid-state reaction with a suitable transition metal salt. The supported zeolite material thus obtained is then calcined, preferably in air, in a furnace at a temperature ranging from 400 to 650°C. After calcination, the supported zeolite material is vigorously washed with distilled water, filtered, and then dried. A suitable binder, such as an aluminosilicate, boehmite, or silica sol, and optionally an auxiliary agent for plasticization or slip production, are preferably added to and mixed with the hydrous zeolite material thus obtained. In a preferred embodiment, the mixture thus obtained is extruded into a catalyst body (unsupported catalyst) and finally calcined. In another preferred embodiment, the mixture thus obtained is applied to a catalyst support (supported catalyst) and finally calcined. These methods are also well known to those skilled in the art and are established in many technical applications.

[0128] The present invention's N2O decomposition, N2O reduction, and NO XThe reduction, NH3 oxidation, HCN decomposition, and CO oxidation catalysts can independently take the form of shaped bodies of any size and geometry, preferably with a large surface-to-volume ratio and a geometry that generates minimal pressure drop when the stream flows through them. Typical geometries are all those known in catalysis, such as cylinders, hollow cylinders, multi-hole cylinders, rings, trilobes, or star-shaped extrudates. Monolithic catalyst elements, for example, permeated by parallel channels, are particularly preferred. For example, monolithic honeycombs, known as "catalytic honeycombs," are known from the purification or detoxification of power plant off-gases or automobile exhaust gases.

[0129] Catalyst honeycomb, honeycomb body, and honeycomb body module The off-gas treatment system of the present invention or the catalyst bed contained therein preferably comprises a catalytic honeycomb, preferably a plurality of catalytic honeycombs, arranged parallel to one another with the honeycomb channels in the off-gas duct [SMD1] aligned longitudinally in the flow direction of the off-gas. The shape of the cross-sectional area of ​​the catalytic honeycomb (perpendicular to the flow direction of the off-gas) can in principle be freely selected. The catalytic honeycomb preferably has a rectangular or, in particular, square cross-sectional area, although other cross-sectional areas are also possible, in particular hexagonal, triangular, trapezoidal, etc. Suitable shapes are known to those skilled in the art. Therefore, the term "honeycomb" according to the present invention is not limited to rectangular or square cross-sectional areas.

[0130] When the inventive off-gas treatment system comprises a first reaction zone (first catalyst bed) and a second reaction zone (second catalyst bed) downstream in the flow direction of the off-gas, which is preferred according to the invention, the first and second reaction zones (first and second catalyst beds) preferably have several catalytic honeycombs arranged parallel to one another in honeycomb channels in an off-gas duct that are aligned longitudinally with respect to the flow direction of the off-gas.

[0131] In a preferred embodiment, several catalytic honeycombs, i.e. several monolithic honeycombs, are combined to form a honeycomb body module, preferably by means of a metal frame open in the off-gas flow direction. Preferably, two, four or six honeycomb bodies, preferably monolithic honeycomb bodies, are combined in each case to form a honeycomb body module. This modular structure allows for good utilization of the available cross-sectional area of ​​the off-gas duct and for easy replacement of defective or deactivated honeycomb bodies.

[0132] The honeycomb body preferably has a rectangular cross section. The rectangular cross section preferably has a first edge length (perpendicular to the off-gas flow direction) in the range of 5 to 20 cm, preferably 10 to 15 cm, and a second edge length (also perpendicular to the off-gas flow direction) in the range of 5 to 20 cm, preferably 10 to 15 cm. The height of the honeycomb body (in the off-gas flow direction) is preferably in the range of 5 to 25 cm, preferably 7.5 to 15 cm.

[0133] The so-called cell density, i.e. the density of the honeycomb channels, is preferably from 150 to 500 cpsi, preferably from 180 to 450 cpsi (cells per square inch). 100 cpsi, i.e. 100 cells or honeycomb channels per square inch.

[0134] Preferably, the individual honeycomb body modules are stacked one on top of the other in the flow direction and fixed by suitable mounting devices to achieve maximum utilization of the inlet area, i.e., the cross-sectional area of ​​the off-gas duct. Bypass flows between the individual honeycomb body modules or in the peripheral area between the outer edge of the honeycomb body module and the inner wall of the off-gas duct should be avoided. For this purpose, suitable seals are preferably applied between the individual honeycomb body modules and between the outer honeycomb body module and the inner wall. In the case of larger wall separations, cover plates are used that are attached to the inner wall of the off-gas duct in the flow direction in front of and / or behind the packing of the honeycomb body modules. The cover plates are preferably covered with seals at their contact points with the honeycomb body modules. The honeycomb body modules are preferably arranged and selected in terms of size so that the usable inlet area of ​​the catalyst is preferably at least 60%, more preferably at least 70%, and even more preferably at least 80% of the internal cross-sectional area of ​​the off-gas duct.

[0135] In the case of a circular off-gas duct or off-gas pipeline, gaps occurring in the edge regions of the packing of the honeycomb body modules are preferably not filled with specially adjusted honeycomb bodies but are closed by blind plates, unless they can be easily occupied by rectangular honeycomb body modules, which has the advantage that when replacing used honeycomb bodies, only standardized honeycomb body modules need to be replaced and no special adjustments are required.

[0136] When using an off-gas pipeline, it is also possible to use individual larger honeycomb bodies, preferably adapted to a pipe cross-section with a circular inlet cross-section, several of which may also be arranged successively in the flow direction in a preferred configuration, in which case it is not necessary to arrange several honeycomb bodies parallel to one another.

[0137] In a preferred embodiment, the honeycomb bodies or honeycomb body modules are arranged in several layers offset along their longitudinal axes in the flow direction of the off-gas. The honeycomb bodies or honeycomb body modules are preferably arranged in 2 to 5 layers, more preferably in 2 to 3 layers. Between the layers, i.e., between the end faces of the honeycomb bodies or honeycomb body modules, a margin of preferably 3 to 30 mm, more preferably 4 to 20 mm, is preferably provided. The margin allows for intermediate, especially radial, mixing of the gas flow leaving the first layer of honeycomb bodies or honeycomb body modules. Furthermore, any possible slippage of unreacted reducing agent and / or its reaction products that have not yet been fully oxidized can be prevented from propagating from the first layer of honeycomb bodies to the subsequent second layer of honeycomb bodies.

[0138] NO X and optionally a reducing agent for NO, is preferably supplied and distributed via a manifold pipeline system having multiple openings or nozzles arranged in the off-gas duct or off-gas conduit upstream of each catalyst bed in the flow direction, preferably upstream of a packing of catalyst honeycombs as a honeycomb body or honeycomb body module.

[0139] The distributor is preferably designed in the form of a grid or in the form of concentrically connected circles which extends as far as possible over the cross section of the off-gas duct or the inlet area of ​​the catalyst bed.

[0140] The specific design and dimensions of these distributors, including appropriate outlet nozzles, are part of the expertise of catalytic off-gas scrubbing technology and are widely used, for example, in coal-fired power plant off-gas treatment.

[0141] NH3 oxidation catalyst NH3 oxidation catalysts are known to those skilled in the art.

[0142] The NH3 oxidation catalyst is preferably free of platinum group metals, and preferably free of precious metals.

[0143] For purposes of description, what is meant by "platinum group metal-free" is the essential absence of platinum group (i.e., Ru, Rh, Pd, Os, Ir, Pt) metals, although analytically detectable trace amounts of platinum group metals are possible. For purposes of description, what is meant by "noble metal-free" is the essential absence of noble metals, although analytically detectable trace amounts of noble metals are possible.

[0144] The NH3 oxidation catalyst is preferably an iron or copper containing zeolite, preferably an iron or copper containing zeolite of MFI, BEA, FER, MOR, FAU, AEI and / or MEL structure type (hereinafter referred to as NH3 oxidation active iron or copper containing zeolite catalyst).

[0145] Preferred platinum group metal-free NH3 oxidation catalysts are selected from transition metal oxides (e.g., Fe, Mn, Cu, Cr, Co, Ni...), metal-containing zeolites, as described, for example, in Handbook of Heterogeneous Catalysis, Wiley-VCH, edited by Ertl, Knotzinger, Schuth, Weitkamp, ​​2nd Ed. 2008, Volume 5, Chapter 11.5 "Solid Catalysts for the Oxidation of Volatile Organic Compounds".

[0146] Preferred NH3 oxidation catalysts include: Cobalt catalysts, in particular Co3O4; Co3O4-derived mixed oxides (Co), which preferably crystallize as Co3O4 in a spinel structure, where M is preferably selected from Zn, Cu, Fe, Mn and V. 3-y M y O4); cobalt-containing zeolites preferably of the MFI, BEA, FER, MOR, FAU, CHA or AFI structural type; -Manganese catalyst; especially MnO with x=1-2 X MnO, where M is preferably selected from Zn, Cu, Fe and Mn; X Derived mixed oxide (Mn x-yM y O x ); manganese-containing zeolites, preferably of the MFI, BEA, FER, MOR, FAU, CHA or AFI structural type; - Copper catalyst; especially CuO with x=0.5-1 X CuO, where M is preferably selected from Zn, Co, Fe and Mn; X Derived mixed oxide (Cu x-y M y O x ); copper-containing zeolites, preferably of the MFI, BEA, FER, MOR, FAU, CHA, AFI structural type; silver catalysts, especially in supported form, preferably supported on Al2O3, TiO2 or SiO2; more preferably, for example, X% Ag / TiO2, X% Ag / Al2O3 or X% Ag / SiO2, where X=1 to 10 in each case; Examples include:

[0147] In a preferred embodiment, the device of the present invention does not contain any additional NH3 oxidation catalyst other than the iron or copper containing zeolite.

[0148] In a preferred embodiment, the NH3 oxidation catalyst, preferably the NH3 oxidation active iron-containing zeolite catalyst, has an iron to zeolite aluminum molar ratio n(Fe) / n(Al) of less than 0.50 and greater than 0.05, preferably less than 0.40 and greater than 0.05, more preferably less than 0.25 and greater than 0.05, and even more preferably less than 0.15 and greater than 0.05.

[0149] In a preferred embodiment, the NH3 oxidation catalyst, preferably the NH3 oxidation active copper-containing zeolite catalyst, has a copper to zeolite aluminum molar ratio n(Cu) / n(Al) of less than 1.00 to greater than 0.10, preferably less than 0.80 to greater than 0.10, more preferably less than 0.50 to greater than 0.10, and even more preferably less than 0.30 to greater than 0.10.

[0150] Surprisingly, it has been found that iron- or copper-containing zeolites in which only a portion of the potentially available cation sites are occupied by Fe or Cu ions, such that the remaining cation sites are essentially filled by protons, have significantly increased activity for the oxidation of NH3 with free oxygen.

[0151] The ratio of iron or copper to zeolite aluminum can be adjusted by selecting the Al content in the synthesis of the zeolitic material, particularly via the proportions of Si and Al starting materials selected, and by subsequent loading with iron or copper ions.

[0152] In the synthesis of zeolites, selected Si and Al starting materials are typically heated in alkaline solution, often under high pressure, to induce crystallization and produce three-dimensionally categorised AlO2. - and SiO2 units, a microporous aluminosilicate, zeolite, is obtained. By controlled selection of synthesis conditions, for example by adding structure-directing agents, such as organic cations, it is possible to specifically adjust or control not only the Si / Al ratio and thus the Al content, but also the structure type of the zeolite. The synthesis method is industrially established. Zeolites of different structure types with different Si / Al ratios and containing different cations, for example in the form of Na or NH4, are commercially available.

[0153] Suitable methods known to those skilled in the art, such as liquid-phase or solid-state ion exchange, allow the targeted exchange of cations present in zeolites, such as NH4+, with other cations, such as iron or copper ions (J. Weitkamp, ​​L. Puppe, Catalysis and Zeolites - Fundamental and Applications, Springer-Verlag Berlin Heidelberg New York, 1999 or Kucherov, A.V. Slinkin, AA: Solid state reactions as a method of introducing transition metal cations into high-silica zeolites, Russ. Chem. Rev. 1992, vol. 61, no. 9, pp. 925-943). The so-called exchange level is 100% when all negative charges generated by the AlO2 units are compensated by cations.

[0154] The exact Al content of the zeolitic material of the invention or of the shaped catalyst bodies produced therefrom, and the equally well-known Fe content, can be determined by X-ray fluorescence analysis (XRF), suitably in accordance with DIN EN 169-2 (section 5), after measuring the loss on ignition and after lithium tetraborate digestion.

[0155] If it is intended to determine the Al content of the parent zeolitic material subsequent to the finished compact, it should be noted that the compact may also contain Al-based binder components that are indistinguishable from zeolitic Al by XRF, e.g., allowing for the distinction between Al bound to the zeolitic structure and extra-lattice Al. 27Further investigation of compacts by Al solid-state NMR is required. Those skilled in the art are familiar with the details of the basis, conduct, and evaluation of such studies (J. Weitkamp, ​​L. Puppe, Catalysis and Zeolites—Fundamental and Applications, Springer-Verlag Berlin Heidelberg New York, 1999, Chapter 4.2 (NMR Spectroscopy; especially sections 4.2.4.1 ( 29 Si MAS NMR Spectroscopy of SiO4Tetrahedra in the Zeolite Framework)and 4.3.4.2( 27 Al NMR Spectroscopy of Framework and Non-Framework Aluminum in Zeolites)).

[0156] The NH3 oxidation catalyst, preferably the NH3 oxidation active iron-containing zeolite catalyst, preferably has a total iron content (reported as mass content of Fe2O3) of less than 10.0 wt% to more than 2.0 wt%, preferably less than 7.0 wt% to more than 2.0 wt%, more preferably less than 5.0 wt% to more than 2.0 wt%, and even more preferably less than 4.0 wt% to more than 2.0 wt%.

[0157] The NH3 oxidation catalyst, preferably the NH3 oxidation active copper-containing zeolite catalyst, preferably has a total copper content (reported as the mass content of Cu2O) of less than 9.0 wt% to more than 1.5 wt%, preferably less than 6.5 wt% to more than 1.5 wt%, more preferably less than 4.5 wt% to more than 1.5 wt%, and even more preferably less than 3.5 wt% to more than 1.5 wt%.

[0158] In a preferred embodiment, the NH3 oxidation catalyst, preferably an NH3 oxidation active iron- or copper-containing zeolite catalyst, configured to selectively oxidize NH3 with O2 to N2 and HO, is introduced in the form of a particulate bed, the particles having an equivalent diameter, defined as the diameter of a spherical particle of equivalent volume, of 3.5 to 5.5 mm, and the ratio of the geometrically detectable outer surface area of ​​the particles to the volume of the particulate bed is 10,000±500 h -1 The reactor was operated isothermally in an axial flow tubular reactor with an internal diameter of 20 ± 3 mm, in which a volume of 8.0 ± 0.5 ml was added to 1000 m3 of the reactor, which was contacted with a volumetric flow of a gas mixture consisting of 500 ± 50 ppmv NH3, 2.5 ± 0.1 vol.% O2, and 0.30 ± 0.05 vol.% H2O in N2 at a space velocity based on standard conditions (0 °C; 1.01325 bara). 2 / m 3 1500m from 2 / m 3 and a total pressure of 6±1500 bara and a temperature of 380° C.±5 K results in an NH conversion of at least 50%, preferably at least 60%, more preferably at least 70%, even more preferably at least 80%, especially at least 90%.

[0159] In a preferred embodiment, an N2O decomposition catalyst and / or an N2O reduction catalyst and / or an NO X The reduction catalyst and / or the NH3 oxidation catalyst independently have a honeycomb monolithic structure.

[0160] In a preferred embodiment, an N2O decomposition catalyst and / or an N2O reduction catalyst and / or an NO X The reduction catalyst and / or the NH3 oxidation catalyst independently have a honeycomb monolithic structure.

[0161] N2O decomposition catalyst and / or N2O reduction catalyst and NO X The reduction catalysts preferably each independently comprise a transition metal-containing zeolite, preferably each an iron-containing zeolite (Fe-zeolite), even more preferably each iron-containing zeolite having the same structural type, and most preferably the same external shape (e.g., honeycomb or pellet).

[0162] In a preferred embodiment, the N2O decomposition catalyst and the N2O reduction catalyst are formed from the same material.

[0163] In a preferred embodiment, the NO decomposition catalyst and NO X The reduction catalyst is formed from the same material.

[0164] In a preferred embodiment, an N2O reduction catalyst and an NO X The reduction catalyst is formed from the same material.

[0165] In a preferred embodiment, an N2O decomposition catalyst, an N2O reduction catalyst, and an NO X The reduction catalyst is formed from the same material.

[0166] In a preferred embodiment, the NH3 oxidation catalyst and the N2O decomposition catalyst are formed from the same material.

[0167] In a preferred embodiment, the NH3 oxidation catalyst and the N2O reduction catalyst are formed from the same material.

[0168] In a preferred embodiment, an NH3 oxidation catalyst and NO X The reduction catalyst is formed from the same material.

[0169] In a preferred embodiment, the catalyst is an NH3 oxidation catalyst, NO X The reduction catalyst and the N2O decomposition catalyst are formed from the same material.

[0170] In step (a) of the method of the present invention, NH3 is combusted to drive an internal combustion engine, or the device of the present invention is configured accordingly. The combustion produces N2, HO, NO X and N2O, preferably further NH3. The off-gas leaves the internal combustion engine and is fed to step (b) of the method of the invention, or the device of the invention is configured accordingly.

[0171] The internal combustion engine, which is preferably a reciprocating piston engine, is preferably equipped with a compression ignition system.

[0172] Preferably, the internal combustion engine comprises a turbocharger comprising a turbocompressor and an off-gas turbine. Preferably, all components of the off-gas treatment system are arranged upstream of the off-gas turbine in the flow direction of the off-gas.

[0173] Preferably, the internal combustion engine is equipped with a system for exhaust gas recirculation (EGR).

[0174] In step (a) or in an internal combustion engine constructed according to the present invention, the combustion of NH, i.e., the oxidation of NH with O (or a mixture of NH with a further combustible gas, e.g., H, CH, etc.), is preferably not carried out via a catalyst, i.e., the combustion is not carried out in the presence of a heterogeneous catalyst.

[0175] In a preferred embodiment, the internal combustion engine is an ammonia dual fuel engine.

[0176] In a preferred embodiment, in step (a) or in an internal combustion engine configured according to the present invention, NH is combusted in a mixture with one or more further combustible gases, meaning that both NH and the at least one further combustible gas are oxidized with O.

[0177] In a preferred embodiment, the further combustible gas is a fossil fuel.

[0178] In a preferred embodiment, the further combustible gas is selected from hydrocarbons and hydrocarbon mixtures, preferably methane, ethane, propane, butane, natural gas, gasoline and / or diesel.

[0179] In a preferred embodiment, the further combustible gas is selected from alcohols, preferably methanol and / or ethanol.

[0180] In another preferred embodiment, the further combustible gas is H2.

[0181] More preferably, the further combustible gas is H formed by thermal and / or catalytic cracking of NH. Preferably, it is the combined combustion of NH and O that provides the energy for the cracking. Preferably, in step (a) or in an internal combustion engine configured according to the present invention, the combustion of NH is therefore integrated into the process for the thermal and / or catalytic decomposition of NH to N and H.

[0182] Preferably, the apparatus of the present invention comprises a cracking device for thermal and / or catalytic cracking of NH3. Preferably, the cracking device and the internal combustion engine are configured such that combustion of NH3 in the internal combustion engine provides energy for cracking of NH3 in the cracking device. Preferably, the cracking device and the internal combustion engine are configured such that cracking of NH3 in the cracking device provides further combustible gases for combustion in mixture with NH3 in the internal combustion engine.

[0183] Preferably, the cracking device is located downstream of the NH3 reservoir in the flow direction of the NH3 and upstream of the NH3 injection for the internal combustion engine.

[0184] In particularly preferred embodiments, step (a) of the method of the present invention comprises the following component steps, or the internal combustion engine of the present invention is configured to: (a1) thermally and / or catalytically cracking NH3 to produce a cracked gas comprising N2, H2, and optionally residual NH3; (a2) optionally mixing the cracking gas with additional NH3 to produce a mixture comprising H2 and NH3; (a3) burning the cracking gas or mixture;

[0185] Suitable methods for the thermal and / or catalytic cracking of NH to N and H are known to those skilled in the art. Suitable catalysts for cracking NH to N and H are, for example, Ru supported on AlO or SiO, Fe, Co, Ni, Cu or Ru supported on MgAlO, or CoMoN (A. Boisen et al., Journal of Catalysis 230 (2005) 309-312; I. Lucentini et al., Ind. Eng. Chem. Res. 2021, 60, 18560-18611; HJ Lee et al., Catalysts 2022, 12, 1203).

[0186] If the cracking in component step (a1) does not proceed to completion, the cracked gas (i.e., the cracking product) will contain residual unconverted NH3 as well as N2 and H2. In this way, a mixture of NH3 and H2 is already obtained, which can be directly combusted as is or first enriched with additional NH3 in optional component step (a2).

[0187] If the cracking in component step (a1) goes to completion, the required amount of NH3 must still be added to the cracking gas in step (a2).

[0188] Preferably, component step (a1) and optionally component step (a2) establish an optimized NH3 and H2 mixture ratio for subsequent combustion. The H2 proportion is preferably at most 80 mol%, more preferably at most 70 mol%, even more preferably at most 60 mol%, most preferably at most 50 mol%, in particular at most 40 mol%. The H2 proportion is preferably at least 10 mol%, more preferably at least 20 mol%, even more preferably at least 30 mol%, most preferably at least 40 mol%, in particular at least 50 mol%, or the device of the present invention is configured accordingly.

[0189] In a particularly preferred embodiment, the molar ratio of H2:NH3 in the mixture is in the range of 45:55 to 90:10, preferably 50:50 to 85:15, more preferably 55:45 to 80:20, even more preferably 60:40 to 75:25, and most preferably 65:35 to 70:30, or the apparatus of the present invention is configured accordingly.

[0190] In component step (a3), the mixture is typically combusted with air. In a preferred embodiment, the air ratio λ for the combustion in component step (a3) ​​is in the range of 0.9 to 1.7, preferably 1.05 to 1.7, more preferably 1.0 to 1.6, even more preferably 1.1 to 1.5, and most preferably 1.2 to 1.4, or the apparatus of the present invention is configured accordingly.

[0191] Preferably, the internal combustion engine is configured so that the air ratio λ during combustion is at least 1.05, preferably at least 1.10, more preferably at least 1.15, even more preferably at least 1.20, most preferably at least 1.25, especially at least 1.20.

[0192] Preferably, the internal combustion engine is configured so that the air ratio λ during combustion is at least 1.25, preferably at least 1.30, more preferably at least 1.35, even more preferably at least 1.40, most preferably at least 1.45, especially at least 1.50.

[0193] The air ratio λ (i.e., combustion air ratio) indicates the mass ratio of air to fuel relative to the stoichiometrically ideal ratio for a theoretically complete combustion process. It is defined as the ratio of air to fuel containing a sufficient mass of oxygen to achieve complete combustion of a given mass of fuel (see, e.g., K. Soman, Thermal Engineering, PHI, 2011, page 224, no. 5.4.2). In principle, the ratio can be expressed in mass or molar amounts (see, e.g., P. Majumdar, Design of Thermal Energy Systems, Wiley 2021, page 66, no. 2.13.5.2). For purposes of explanation, the ratio is based on mass. If another oxygen-containing gas is used in the combustion operation instead of air, "air" should, strictly speaking, be replaced by "oxygen carrier." However, the λ parameter is still used in the above definition.

[0194] In a preferred embodiment, the equivalence ratio NH3 / H2 (Φ) (not to be confused with the reciprocal of the air ratio 1 / λ) is in the range of 0.55 to 1.40, more preferably 1.05 to 1.20, or the apparatus of the present invention is configured accordingly.

[0195] In another preferred embodiment, in step (a) or in an internal combustion engine constructed according to the present invention, NH3 is combusted alone, i.e., NH3 is the only combustible gas combusted.

[0196] Preferably, the internal combustion engine is configured so that combustion of NH3 accounts for at least 90%, preferably at least 95%, more preferably at least 96%, even more preferably at least 97%, most preferably at least 98%, especially at least 99% of the total energy available.

[0197] The internal combustion engine is installed on a ship and serves to move the ship.

[0198] In a preferred embodiment, the off-gas has a NO content greater than N2O content. XThe device of the present invention has a content of NO. X The content is preferably at least 2 times, more preferably at least 3 times, even more preferably at least 4 times, most preferably at least 7 times, especially at least 10 times the NO content, or the device of the invention is configured accordingly. X The molar ratio of N2O to N2O is preferably greater than 10:1, more preferably at least 20:1, even more preferably at least 30:1, most preferably at least 40:1, especially at least 50:1.

[0199] In a preferred embodiment, the off-gas has, or the apparatus of the present invention is configured accordingly, a NO content greater than the NO content, with the NO content being preferably at least 2 times, more preferably at least 3 times, even more preferably at least 4 times, most preferably at least 7 times, and especially at least 10 times the NO content.

[0200] In a preferred embodiment, the off-gas has, or the apparatus of the present invention is configured accordingly, a NO content that is higher than the N2O content, with the NO content being preferably at least 2 times, more preferably at least 3 times, even more preferably at least 4 times, most preferably at least 7 times, especially at least 10 times the N2O content.

[0201] Preferably, the off-gas contains at least 10 ppmv, preferably at least 20 ppmv, more preferably at least 30 ppmv, even more preferably at least 40 ppmv, especially at least 50 ppmv NO X The device of the present invention has a corresponding content.

[0202] Preferably, the off-gas contains at least 75 ppmv, preferably at least 100 ppmv, more preferably at least 150 ppmv, even more preferably at least 200 ppmv, especially at least 250 ppmv NOX The device of the present invention has a corresponding content.

[0203] Preferably, the off-gas contains at least 500 ppmv, preferably at least 1000 ppmv, more preferably at least 2000 ppmv, even more preferably at least 3000 ppmv, especially at least 3500 ppmv NO X The device of the present invention has a corresponding content.

[0204] Preferably, the off-gas has an N2O content of at least 10 ppmv, preferably at least 20 ppmv, more preferably at least 30 ppmv, even more preferably at least 40 ppmv, especially at least 50 ppmv, or the apparatus of the present invention is configured accordingly.

[0205] Preferably, the off-gas has an N2O content of at least 75 ppmv, preferably at least 100 ppmv, more preferably at least 150 ppmv, even more preferably at least 200 ppmv, especially at least 250 ppmv, or the apparatus of the present invention is configured accordingly.

[0206] The preferred off-gas is NO in the range of 1500 to 3000 ppmv, preferably 2000 to 3000 ppmv. X content, and an N2O content in the range of 20 to 100 ppmv, or the device of the present invention is configured accordingly.

[0207] In a preferred embodiment, the off-gas has an HO content of more than 4.0 vol.%, preferably at least 5.0 vol.%, more preferably at least 6.0 vol.%, even more preferably at least 7.0 vol.%, most preferably at least 8.0 vol.%, especially at least 9.0 vol.%, or the apparatus of the invention is configured accordingly.

[0208] In a further preferred embodiment, the off-gas has an HO content of at least 10% by volume, preferably at least 12% by volume, more preferably at least 14% by volume, even more preferably at least 16% by volume, most preferably at least 18% by volume, especially at least 20% by volume, or the apparatus of the invention is configured accordingly.

[0209] In a preferred embodiment, the off-gas has an HO content in the range of 10±8% by volume, preferably in the range of 10±7% by volume, more preferably in the range of 10±6% by volume, even more preferably in the range of 10±5% by volume, most preferably in the range of 10±4% by volume and especially in the range of 10±3% by volume, or the apparatus of the invention is configured accordingly.

[0210] In a preferred embodiment, the off-gas has an HO content in the range of 15±8% by volume, preferably in the range of 15±7% by volume, more preferably in the range of 15±6% by volume, even more preferably in the range of 15±5% by volume, most preferably in the range of 15±4% by volume and especially in the range of 15±3% by volume, or the apparatus of the invention is configured accordingly.

[0211] In a preferred embodiment, the off-gas has an HO content in the range of 20±8% by volume, preferably in the range of 20±7% by volume, more preferably in the range of 20±6% by volume, even more preferably in the range of 20±5% by volume, most preferably in the range of 20±4% by volume, especially in the range of 20±3% by volume, or the apparatus of the invention is configured accordingly.

[0212] In a preferred embodiment, the off-gas has an HO content in the range of 25±8% by volume, preferably in the range of 25±7% by volume, more preferably in the range of 25±6% by volume, even more preferably in the range of 25±5% by volume, most preferably in the range of 25±4% by volume and especially in the range of 25±3% by volume, or the apparatus of the invention is configured accordingly.

[0213] In a preferred embodiment, the off-gas has an HO content in the range of 30±8% by volume, preferably in the range of 30±7% by volume, more preferably in the range of 30±6% by volume, even more preferably in the range of 30±5% by volume, most preferably in the range of 30±4% by volume and especially in the range of 30±3% by volume, or the apparatus of the invention is configured accordingly.

[0214] Preferably, the off-gas has an N content of at most 95% by volume, preferably at most 90% by volume, more preferably at most 85% by volume, even more preferably at most 80% by volume, most preferably at most 75% by volume, especially at most 70% by volume, or the apparatus of the present invention is configured accordingly.

[0215] Preferably, the off-gas has an N content of at least 40% by volume, preferably at least 50% by volume, more preferably at least 60% by volume, even more preferably at least 70% by volume, most preferably at least 80% by volume, especially at least 90% by volume, or the apparatus of the present invention is configured accordingly.

[0216] Preferably, the off-gas comprises further gaseous components, preferably selected from the group consisting of O2, CO, CO2, NH3, CH4 and mixtures thereof, or the device of the present invention is configured accordingly.

[0217] Preferably, the off-gas comprises NH3 or the apparatus of the present invention is configured accordingly.

[0218] Preferably, the off-gas leaving the internal combustion engine is at a temperature in the range of 250 to 450°C, or the device of the present invention is configured accordingly.

[0219] Preferably, the off-gas is cooled over the course of the method of the present invention after leaving the internal combustion engine, although steps (c1) and / or (c2) and / or (d) may introduce new heat, or the apparatus of the present invention is configured accordingly.

[0220] Preferred variant of the combination of steps (c) and (d): In a preferred embodiment, steps (c1) and / or (c2) and / or (d) of the method of the invention are carried out at different temperatures, i.e. at different temperature levels, the steps carried out before or upstream in the flow direction of the off-gas preferably proceeding at a higher temperature than the steps carried out after or downstream in the flow direction of the off-gas, or the apparatus of the invention is configured accordingly.

[0221] Preferably, the off-gas leaving the internal combustion engine is at a pressure of up to 5.0 bar, preferably 2.5 to 4.0 bar, or the device of the invention is configured accordingly.

[0222] Preferably, the off-gas from the internal combustion engine contains at least 10%, more preferably at least 20%, even more preferably at least 30%, most preferably at least 40%, especially at least 50% NO X or the device of the present invention is configured accordingly.

[0223] Preferably, the off-gas from the internal combustion engine contains at most 90%, preferably at most 80%, more preferably at most 70%, preferably at most 60%, especially at most 50% NO X or the device of the present invention is configured accordingly.

[0224] Preferably, the off-gas leaving the internal combustion engine has an O2 content of less than 2.0% by volume, or the device of the present invention is configured accordingly.

[0225] Preferably, the off-gas leaving the internal combustion engine has an O2 content of more than 4.0% by volume, or the device of the present invention is configured accordingly.

[0226] In step (b) of the method of the present invention, the off-gas leaving the internal combustion engine is transferred to an off-gas treatment system, or the apparatus of the present invention is correspondingly configured therefor.

[0227] This can be done, for example, by a pipeline connecting the outlet of the internal combustion engine to the inlet of the off-gas treatment system. Since the method of the invention is preferably carried out at atmospheric pressure or the apparatus of the invention is configured accordingly, such pipelines are generally not subject to special requirements regarding possible compressive stresses.

[0228] However, the pipeline must withstand the temperatures of the off-gas exiting the internal combustion engine or entering the off-gas treatment system.

[0229] In a preferred embodiment, the off-gas temperature is measured at the outlet of the internal combustion engine and optionally modified with a suitable device, or the device of the present invention is correspondingly configured, so that the off-gas entering the off-gas treatment system has an optimized temperature under given conditions for carrying out steps (c) and (d) of the method of the present invention in the off-gas treatment system. The optimized temperature is in particular determined by the temperature of the NO decomposition catalyst and / or the NO reduction catalyst and the NO X The optimized temperature depends on the type of catalytic material used in the reduction catalyst. The optimized temperature depends on the selected configuration of steps (c) and (d), i.e., NO reduction and NO X The type and sequence of the individual process steps for reduction, in particular the N2O decomposition catalyst and / or N2O reduction catalyst and the NO X This is guided by the type of catalytic material used in the reduction catalyst.

[0230] Suitable devices for modifying the off-gas temperature are known to those skilled in the art and include in particular heat exchangers which may be configured, for example, as plate or tube heat exchangers.

[0231] In order to avoid heat losses, according to the invention it may be preferable to choose the distance from the outlet of the internal combustion engine to the inlet to the off-gas treatment system as short as possible, thus achieving a compact design.

[0232] However, depending on the nature of the catalyst used, the steps may not be completely separable from one another locally or in time. If the catalyst used is simultaneously suitable for catalyzing two or more of steps (c1), (c2) and (d), these steps may proceed simultaneously and / or sequentially. In the flow direction of the off-gas, it is possible to consider individual segments of one and the same catalyst through which the off-gas flows successively and in which different reactions may prevail. Which reaction prevails in which section depends, inter alia, on the respective reaction kinetics, the local temperature, the local concentrations of the reactants, which may include the concentration of the reducing agent and / or the concentration of the cocatalytic active species.

[0233] The off-gas treatment system of the present invention is particularly useful for carrying out steps (c) and (d) of the method of the present invention, or the apparatus of the present invention is correspondingly configured therefor. However, in addition to steps (c) and (d), further steps and chemical reactions can also be carried out in the off-gas treatment system, or the apparatus of the present invention is correspondingly configured therefor.

[0234] This preferably relates to the installation of a catalyst bed arranged downstream in the flow direction of the off-gas for the oxidation of the incompletely converted reducing agent or its still incompletely oxidized reaction products, i.e., for example, the oxidation of NH (NH oxidation catalyst) or CO (CO oxidation catalyst; if hydrocarbons are used as reducing agents). In such an embodiment, the off-gas is preferably cooled before being introduced into the downstream catalyst bed, i.e., the oxidation of NH and / or CO is preferably carried out at a lower temperature than in steps (c) and (d).

[0235] In carrying out steps (c) and (d) of the process of the invention, there are, according to the invention, different preferred variants of the process regime which may differ from one another with regard to the order of reactions proceeding, the catalyst used, the reducing agent used, the space velocity and other reaction conditions.

[0236] In a preferred embodiment, these reactions take place in a common reaction zone (catalyst bed) with an upstream device for metering a reducing agent into the off-gas.

[0237] In another preferred embodiment, these reactions are carried out in two separate reaction zones (catalyst beds) arranged in series, of which preferably at least one reaction zone, and preferably both reaction zones, is independently equipped upstream with a device for metering a reducing agent into the off-gas, in which case the off-gas flows first through the first reaction zone and subsequently through the second reaction zone.

[0238] Particularly preferred variants / embodiments are: [a] (c2) chemical reduction of N2O with NH3 and (d) NO with NH3, preferably together in one reaction zone X Chemical reduction of; [b] (c2) chemical reduction of N2O with hydrocarbons (CH4, natural gas, etc.) and (d) NO with NH3, preferably together in one reaction zone X Chemical reduction of; [c] (c1) decomposition of NO with NH3 and (d) decomposition of NO, preferably together in one reaction zone X Chemical reduction of; [d] (c1) decomposition of N2O and (c2) chemical reduction of N2O with NH3 and (d) NO with NH3, preferably together in one reaction zone. X Chemical reduction of; [e] (c1) decomposition of N2O and (c2) chemical reduction of N2O with hydrocarbons (CH4, natural gas, etc.) and (d) decomposition of NO with NH3, preferably together in one reaction zone. X Chemical reduction of; [f] (c1) decomposition of N2O, preferably in a first reaction zone; then (d) decomposition of NO with NH3, preferably in a second reaction zone. X Chemical reduction of; [g] (c1) preferably incomplete decomposition of N2O in a first reaction zone; then (c2) chemical reduction of residual N2O with NH3 and (d) preferably decomposition of NO2O with NH3 in a second reaction zone. X Chemical reduction of; [h] (c1) preferably incomplete decomposition of N2O in a first reaction zone; then (c2) chemical reduction of the residual N2O with hydrocarbons (CH4, natural gas, etc.) and (d) preferably decomposition of NO with NH3 in a second reaction zone. X Chemical reduction of; [i] (c1) preferably incomplete decomposition of N2O in the first reaction zone; then (c1*) decomposition of the residual N2O and (d) preferably decomposition of NO with NH3 in the second reaction zone. X Chemical reduction of; [j] (c1) preferably incomplete decomposition of N2O in a first reaction zone; then (c1*) decomposition of residual N2O, and (c2) chemical reduction of residual N2O with NH3 and (d) preferably decomposition of NO in a second reaction zone. X Chemical reduction of with NH3; [k] (c1) preferably incomplete decomposition of N2O in a first reaction zone; then (c1*) decomposition of residual N2O, and (c2) chemical reduction of residual N2O with hydrocarbons (CH4, natural gas, etc.), and (d) preferably reduction of NO2O with NH3 in a second reaction zone. X Chemical reduction of.

[0239] [l](d) Preferably, NO in the first reaction zone X incomplete chemical reduction of NO; ​​then (c1) decomposition of NO and (d*) preferably residual NO with NH in a second reaction zone. X Chemical reduction of; [m](d) preferably NO in the first reaction zone X incomplete chemical reduction of NO; ​​then (c1) decomposition of NO, and (c2) chemical reduction of NO with NH, and (d*) decomposition of residual NO preferably with NH in a second reaction zone. X chemical reduction of; or [n](d) preferably NO in the first reaction zoneX then (c1) decomposition of NO, and (c2) chemical reduction of NO with hydrocarbons (CH, natural gas, etc.), and (d*) decomposition of residual NO with NH, preferably in a second reaction zone. X Chemical reduction of.

[0240] However, this does not mean that the explicitly mentioned reactions must be the only reactions occurring in the respective reaction zones. Depending on the catalyst used, further reactions, not explicitly mentioned but which may proceed in parallel, may also preferably occur simultaneously according to the present invention. The explicitly mentioned reactions are therefore the only reactions which at least occur in each variant / embodiment.

[0241] NO X , N2O and NH3 are present in the mixture, and the catalyst used is the conversion of NO by NH3 X and the chemical reduction of N2O by NH3, X The chemical reduction of NO is typically much faster than the chemical reduction of NO by NH. If the catalyst used also catalyzes the decomposition of NO, the decomposition of NO typically overlaps with the chemical reduction of NO by NH, and the extent of chemical reduction of NO can be increased by increasing the amount of NH metered in.

[0242] For purposes of illustration, an "*" indicates a component method step that has previously been performed only partially in the same type of component method step; the component method step identified by the "*" then continues the previously performed component method step only partially, but possibly in a different reaction zone or a different catalyst bed. As with all other method steps, unless otherwise specified, the results achieved at the end of all component method steps are not quantified. For example, in the first component method step (d), NO X If NO is chemically incompletely reduced, the fact that component method step (d*) is subsequently performed means that at the end of component method step (d*), NOX This does not necessarily mean that the total amount of NO must be completely chemically reduced, i.e., to 0.0 ppmv. Instead, at the end of component method step (d*), X It is entirely possible that residual amounts of

[0243] The off-gas treatment system comprises at least one injection site for the reducing agent. The off-gas treatment system may comprise several injection sites for the reducing agent.

[0244] The mode of introduction of the reducing agent into the off-gas stream to be treated can be freely configured according to the invention, provided that it is not introduced into the N2O reduction catalyst or the NO2O reduction catalyst in the flow direction. X It is carried out upstream of the reduction catalyst. The reducing agent can be introduced in the form of a gas that evaporates in the off-gas stream to be treated, or in the form of a liquid or aqueous solution. The supply is carried out by a suitable device, for example a suitable pressure valve or a suitably designed nozzle, leading to a mixer for the off-gas stream to be treated and the supply of reducing agent. NO X If different reducing agents for N2O and N2O are used, the feed and introduction into the off-gas can be done separately or together.

[0245] In the case of a catalyst bed configuration as a packing of a catalyst honeycomb or honeycomb body module, NO is introduced into one or more reaction zones (catalyst beds). X The supply and distribution of the reducing agent, and optionally NO, is preferably via a manifold pipeline system having multiple openings or nozzles located upstream of each reaction zone (catalyst bed) in the off-gas flow direction, i.e., upstream of the packing of the catalyst honeycomb or honeycomb body module.

[0246] The distributor is preferably designed in the form of a grid or concentrically connected circles extending as far as possible over the cross-sectional area of ​​the off-gas duct or the inlet area of ​​the reaction zone (catalyst bed).

[0247] The specific design and dimensions of these distributors, including appropriate outlet nozzles, are part of the expertise of catalytic off-gas scrubbing technology and are widely used, for example, in coal-fired power plant off-gas treatment.

[0248] The off-gas treatment system of the present invention may include a single reaction zone, in which case the catalyst used in the single reaction zone may serve as an N2O decomposition catalyst and / or an N2O reduction catalyst, and as a NO X In this case, steps (c) and (d) of the method of the present invention are carried out essentially simultaneously in this reaction zone, or the apparatus of the present invention is configured accordingly. However, it should be noted that the reaction rates of the individual conversions may vary considerably. For example, the conversion of NO with NH3 as a reducing agent may be significantly different depending on the catalyst material used. X The chemical reduction of NO by NH3 can proceed much more rapidly than the chemical reduction of NO by NH3. X When NO and N2O are in the mixture and NH3 is supplied as a reducing agent, a different reaction occurs in the front section of a single reaction zone than in the rear section of a single reaction zone. In the front section, NO is reacted more efficiently due to faster kinetics. X The chemical reduction of NO proceeds mainly in the posterior section. X Once most of the N2O is decomposed, the chemical reduction of N2O proceeds.

[0249] Alternatively, the off-gas treatment system may comprise several reaction zones, which is preferred according to the invention. When several reaction zones are included, the zones are preferably consecutive, so that the off-gas flows through them one after the other, first through the first reaction zone, then through the second reaction zone and, if necessary, through the third reaction zone, or the apparatus of the invention is configured accordingly.

[0250] In a preferred embodiment, the reaction zones are each spatially separated catalyst beds.

[0251] In a preferred embodiment, the off-gas undergoes the steps of the method of the invention in one of the following orders, or the apparatus of the invention is correspondingly configured.

[0252] (i) (a) → (b) → (c1) → (d); step (c1) preferably proceeds in a first reaction zone; step (d) proceeds in a second reaction zone; (ii) (a) → (b) → (d) → (c2); step (d) preferably proceeds in the first reaction zone; step (c2) proceeds in the second reaction zone; (iii) (a) → (b) → (d) → (c2) → (c1); step (d) preferably proceeds in the first reaction zone; step (c2) proceeds in the second reaction zone; step (c1) proceeds in the third reaction zone; (iv) (a) → (b) → (d) → (c1) + (c2); step (d) preferably proceeds in a first reaction zone; step (c1) and step (c2) proceed in a second reaction zone; (v) (a) → (b) → (d) → (c1); step (d) preferably proceeds in the first reaction zone; step (c1) proceeds in the second reaction zone; (vi) (a) → (b) → (c1) + (d) → (d*); preferably, step (c1) and step (d) proceed incompletely in the first reaction zone, and the remainder of step (d*) proceeds in the second reaction zone; (vii) (a) → (b) → (c1) + (d) → (d*) + (c2); step (c1) and step (d) preferably proceed incompletely in the first reaction zone, and step (c2) and the remainder of step (d*) proceed in the second reaction zone; (viii) (a) → (b) → (c1) + (c2) + (d) → (c1*) + (c2*) + (d*); step (c1) preferably proceeds partially, step (c2) preferably proceeds partially and step (d) preferably in a first reaction zone that does not contain a zeolitic material as a catalyst, and the remainder of step (c1*), the remainder of step (c2*) and the remainder of step (d*) preferably proceed in a second reaction zone that contains a zeolitic material as a catalyst; (ix) (a) → (b) → (c1) + (c2) + (d) → (c1*) + (c2*) + (d*); step (c1) preferably proceeds incompletely, step (c2) preferably incompletely, and step (d) preferably incompletely in a first reaction zone containing a zeolitic material as catalyst, and the remainder of step (c1*), the remainder of step (c2*), and the remainder of step (d*) preferably proceeds in a first reaction zone containing NO as catalyst. X proceeds in a second reaction zone containing a sensitive N2O decomposition catalyst; (x) (a) → (b) → (c1) → (c1*) + (c2) + (d); step (c1) preferably proceeds incompletely in a first reaction zone, preferably comprising a zeolitic material as a catalyst, and steps (c1*) and (c2) and the remainder of step (d) preferably proceed in a second reaction zone, preferably comprising a zeolitic material as a catalyst; (xi) (a) → (b) → (c1) → (c1*) + (c2) + (d); step (c1) preferably comprises NO as a catalyst. X Preferably, the reaction proceeds partially in a first reaction zone containing a sensitive NO decomposition catalyst, with steps (c1*) and (c2) and the remainder of step (d) proceeding in a second reaction zone preferably containing a zeolitic material as catalyst.

[0253] If for engine-related reasons it is necessary to use an NH3 oxidation catalyst which cannot be made of the same material as the catalyst in steps (c) and / or (d), this may be located in a dedicated additional reaction zone in which NH3 is oxidized by O2.

[0254] In a preferred embodiment, this is done upstream of the respective reaction zones in steps (d) and (c) in the flow direction of the off-gas.

[0255] In a preferred embodiment, this is done downstream of the reaction zone in steps (d) and (c) in the flow direction of the off-gas.

[0256] According to the invention, it is also possible to implement such substantially different NH3 oxidation catalysts in one or more reaction zones in step (c) and / or step (d), especially when the reaction zones are configured as honeycomb bodies. The NH3 oxidation catalyst is then preferably in a layered configuration, in which case a layer of catalyst in step (c) and / or step (d) preferably covers a layer of NH3 oxidation catalyst.

[0257] However, it is also possible to implement two or more reaction zones in a single catalyst bed. Two reaction zones within a shared catalyst bed can be formed, or the inventive device is configured accordingly, by supplying a reducing agent, especially in the center of the catalyst bed (or at another location along its longitudinal extent). In this case, since there is no reducing agent upstream of the feed point, steps (c2) and (d) of the inventive method cannot be carried out due to the absence of a reducing agent, or the inventive device is configured accordingly. Then, what takes place upstream is essentially the decomposition of N2O according to step (c1) (first reaction zone), or the inventive device is configured accordingly. Since there is a reducing agent downstream of the feed point, steps (c2) and (d) of the inventive method, which may overlap with step (c1) (second reaction zone), can be carried out, or the inventive device is configured accordingly. Again, due to different reaction rates, different reactions may occur in the sections before each reaction zone than in the sections after each reaction zone. However, in both cases, the first and second reaction zones are chemically reduced to NO in the first reaction zone due to the absence of a reducing agent. X They differ from each other in that no chemical reduction of the compound takes place, or the device of the present invention is configured accordingly.

[0258] In a particularly preferred embodiment, the off-gas treatment system comprises a first reaction zone and a second reaction zone. Additional reaction zones may be present.

[0259] In a preferred embodiment, the first and second reaction zones are spatially separated from one another. In this case, they are preferably separate catalyst beds. In the case of spatial separation of catalyst beds, the temperature of the second catalyst bed or the gas stream entering it can be adjusted by removing or adding heat so that it is lower or higher than the temperature of the first catalyst bed. The temperature of a single catalyst bed can be suitably determined as the arithmetic mean of the temperatures of the gas streams at the inlet and outlet from the catalyst bed.

[0260] In a preferred embodiment, the temperature in the first reaction zone (in the first catalyst bed) is higher than the temperature in the second reaction zone (in the second catalyst bed), or the apparatus of the present invention is configured accordingly.

[0261] Preferably, the temperature of the off-gas entering the first reaction zone is in the range of 280 to 400° C., depending in each case on the load and characteristics of the internal combustion engine.

[0262] Preferably, the temperature in the first reaction zone (in the first catalyst bed) is at least 450°C, preferably at least 500°C, more preferably at least 550°C, most preferably at least 600°C, especially at least 650°C, or the apparatus of the invention is configured accordingly.

[0263] Preferably, the off-gas temperature entering the second reaction zone is in the range of 280 to 400° C., depending in each case on the load and characteristics of the internal combustion engine.

[0264] Preferably, the temperature in the second reaction zone (in the second catalyst bed) is at most 600°C, more preferably at most 550°C, even more preferably at most 500°C, most preferably at most 450°C, especially at most 400°C, or the apparatus of the invention is configured accordingly.

[0265] Preferably, the temperature in the first reaction zone (within the first catalyst bed) is at least 20°C, more preferably at least 40°C, even more preferably at least 60°C, most preferably at least 80°C, especially at least 100°C higher relative to the temperature in the second reaction zone (within the second catalyst bed), or the apparatus of the present invention is configured accordingly.

[0266] Preferably, the temperature in the first reaction zone (in the first catalyst bed) is at least 120°C, more preferably at least 140°C, even more preferably at least 160°C, most preferably at least 180°C, especially at least 200°C higher relative to the temperature in the second reaction zone (in the second catalyst bed), or the apparatus of the present invention is configured accordingly.

[0267] Preferably, the temperature of the off-gas entering the first reaction zone (first catalyst bed) is at least 400°C, more preferably at least 425°C, even more preferably at least 450°C, and most preferably at least 500°C, or the apparatus of the present invention is configured accordingly.

[0268] Preferably, the temperature of the off-gas leaving the second reaction zone (from the second catalyst bed) is at most 600°C, more preferably at most 550°C, even more preferably at most 500°C, or the apparatus of the present invention is configured accordingly.

[0269] In a preferred embodiment, the temperature of the off-gas entering the first reaction zone (to the first catalyst bed) is, relative to the temperature of the off-gas entering the second reaction zone (to the second catalyst bed), at least 20 K, more preferably at least 40 K, even more preferably at least 60 K, most preferably at least 80 K, especially at least 100 K higher, or the apparatus of the invention is configured accordingly.

[0270] In a preferred embodiment, the temperature of the off-gas entering the second reaction zone (second catalyst bed) is, relative to the temperature of the off-gas entering the first reaction zone (first catalyst bed), at least 10 K, more preferably at least 20 K, even more preferably at least 30 K, most preferably at least 40 K, especially at least 50 K higher, or the apparatus of the present invention is configured accordingly.

[0271] In a preferred embodiment, the temperature of the first reaction zone (within the first catalyst bed) is, relative to the temperature of the second reaction zone (within the first catalyst bed), at least 120 K, more preferably at least 140 K, even more preferably at least 160 K, most preferably at least 180 K, especially at least 200 K higher, or the apparatus of the present invention is configured accordingly.

[0272] In a preferred embodiment, the temperature of the second reaction zone (of the second catalyst bed) is, relative to the temperature of the first reaction zone (of the first catalyst bed), at least 120 K, more preferably at least 140 K, even more preferably at least 160 K, most preferably at least 180 K, especially at least 200 K higher, or the apparatus of the present invention is configured accordingly.

[0273] In another preferred embodiment, the first and second reaction zones are spatially connected to one another, in which case the catalyst bed is preferably a shared catalyst bed and external influences result in a division into reaction zones, in particular by the injection site of the reducing agent, so that the reducing agent is not uniformly present throughout the catalyst bed, or the device of the present invention is configured accordingly.

[0274] Preferably, the first reaction zone and the second reaction zone are located within a common vessel.

[0275] Preferably, the off-gas temperatures of the first reaction zone and the second reaction zone are in each case independently up to 500°C, preferably in each case independently in the range from 350 to 450°C, or the apparatus of the invention is configured accordingly.

[0276] In a preferred embodiment, the space velocity in the first reaction zone is greater than the space velocity in the second reaction zone, or the apparatus of the present invention is configured accordingly. Preferably, the space velocity in the first reaction zone is at least 1.2 times, more preferably at least 1.4 times, even more preferably at least 1.6 times, most preferably at least 1.8 times, and especially at least 2.0 times greater than the space velocity in the second reaction zone.

[0277] In another preferred embodiment, the space velocity in the second reaction zone is greater than the space velocity in the first reaction zone, or the apparatus of the present invention is configured accordingly. Preferably, the space velocity in the second reaction zone is at least 1.5 times, more preferably at least 2.0 times, even more preferably at least 3.0 times, most preferably at least 5.0 times, and especially at least 10.0 times greater than the space velocity in the first reaction zone.

[0278] In the context of the present invention, "space velocity" refers to the quotient of the volumetric flow rates of a gas mixture conducted through a catalyst bed based on the volume of the catalyst or catalyst bed (measured at 0°C and 1.014 bara, typically standard m 3 h -1 The space velocity can therefore be adjusted by the volumetric flow rate of the gas and / or the amount of catalyst.

[0279] Preferably, the off-gas entering the off-gas treatment system is at a temperature of at least 300°C, more preferably at least 350°C, even more preferably at least 400°C, most preferably at least 425°C, especially at least 450°C, or the apparatus of the present invention is configured accordingly.

[0280] Preferably, the off-gas entering the off-gas treatment system is at a temperature of at least 500°C, more preferably at least 550°C, even more preferably at least 600°C, most preferably at least 625°C, especially at least 650°C.

[0281] Preferably, the off-gas entering the off-gas treatment system is at a temperature of at least 500°C, more preferably at least 550°C, even more preferably at least 600°C, most preferably at least 625°C, especially at least 650°C, or the apparatus of the present invention is configured accordingly.

[0282] Preferably, the off-gas entering the off-gas treatment system is at a temperature of at most 825°C, more preferably at most 800°C, even more preferably at most 775°C, most preferably at most 750°C, especially at most 725°C, or the apparatus of the invention is configured accordingly.

[0283] Preferably, the off-gas entering the off-gas treatment system is at a temperature of at most 700°C, more preferably at most 650°C, even more preferably at most 600°C, most preferably at most 550°C, especially at most 500°C, or the apparatus of the invention is configured accordingly.

[0284] Preferably, the off-gas is at a temperature in the range of 320 to 600°C, preferably 350 to 600°C, upon entering the off-gas treatment system.

[0285] Preferably, the off-gas entering the off-gas treatment system is at a relatively lower temperature than the temperature of the off-gas leaving the internal combustion engine, or the apparatus of the invention is configured accordingly, which is at least 20°C, preferably at least 40°C, more preferably at least 60°C, even more preferably at least 80°C, most preferably at least 100°C, especially at least 120°C lower.

[0286] Preferably, the off-gas entering the off-gas treatment system is at a pressure of at most 5 bara, preferably at most 4 bara, or the device of the invention is configured accordingly.

[0287] Preferably, the off-gas entering the off-gas treatment system contains at least 10%, more preferably at least 20%, even more preferably at least 30%, most preferably at least 40%, especially at least 50% NO Xor the device of the present invention is configured accordingly.

[0288] Preferably, the off-gas entering the off-gas treatment system contains up to 90%, preferably up to 80%, even more preferably up to 70%, most preferably up to 60%, especially up to 50% NO X or the device of the present invention is configured accordingly.

[0289] Depending on the combustion temperature, the degree of oxidation may also be significantly lower, with the degree of oxidation decreasing with increasing combustion temperature. Preferably, the off-gas entering the off-gas treatment system contains at most 15%, more preferably at most 12.5%, even more preferably at most 10%, most preferably at most 7.5%, especially at most 5.0% NO X has an oxidation degree of

[0290] Preferably, the off-gas entering the off-gas treatment system has an O2 content of less than 2.0% by volume, or the apparatus of the present invention is configured accordingly.

[0291] Preferably, the off-gas entering the off-gas treatment system has an O content of at least 3.0% by volume, preferably at least 3.1% by volume, more preferably at least 3.2% by volume, even more preferably at least 3.3% by volume, most preferably at least 3.4% by volume, especially at least 3.5% by volume, or the apparatus of the present invention is configured accordingly.

[0292] Preferably, the off-gas entering the off-gas treatment system has an O2 content of more than 4.0% by volume, or the apparatus of the present invention is configured accordingly.

[0293] In step (c) of the method of the present invention, the NO content in the off-gas is reduced, or the apparatus of the present invention is configured accordingly. This can be achieved in various ways, namely (c1) by decomposition of NO via an NO decomposition catalyst and / or (c2) by chemical reduction of NO with a reducing agent via an NO reduction catalyst. Step (c) of the method of the present invention is carried out in an off-gas treatment system, or the apparatus of the present invention is configured accordingly.

[0294] In a preferred embodiment, step (c) comprises (c1) reducing the N2O content in the off-gas by decomposition of N2O via an N2O decomposition catalyst, or the device of the invention is configured accordingly.

[0295] In a preferred embodiment, the NO decomposition catalyst comprises a zeolitic material, preferably a zeolite containing a transition metal (including lanthanides), in particular iron, cobalt or copper, more preferably an iron- or copper-containing zeolite, even more preferably an iron- or copper-containing zeolite of the MFI, BEA, FER, MOR, FAU, AEI and / or MEL structural type.

[0296] In another preferred embodiment, the NO decomposition catalyst is a catalyst for decomposing NO within the context of the present invention. X The catalyst is a sensitive NO decomposition catalyst, which has already been described in detail above. In this case, the off-gas preferably first passes through step (d), i.e., the NO in the off-gas X The content is followed by off-gas NO X Preferably quantitatively, NO is decomposed before contact with a sensitive NO decomposition catalyst. X NO by reducing agents via reduction catalysts X is first reduced by chemical reduction of the compound or the device of the present invention is configured accordingly.

[0297] Preferably, the N2O decomposition catalyst is arranged in a radial basket through which the flow passes axially, or the device of the present invention is correspondingly configured.

[0298] The N2O decomposition catalyst is preferably in particulate form and comprises at least 50 particles.

[0299] In a preferred embodiment, step (c) comprises (c2) reducing the NO content in the off-gas by chemical reduction of NO with a reducing agent via an NO reduction catalyst, preferably the NO reduction catalyst comprises a zeolitic material, preferably a zeolite containing a transition metal (including lanthanides), in particular iron, cobalt or copper, more preferably an iron- or copper-containing zeolite, even more preferably an iron- or copper-containing zeolite of the MFI, BEA, FER, MOR, FAU, AEI and / or MEL structural type, or the apparatus of the invention is configured accordingly.

[0300] Preferably, the N2O reduction catalyst is arranged in a radial basket through which the flow passes axially, or the device of the present invention is correspondingly configured.

[0301] The N2O reduction catalyst is preferably in particulate form and comprises at least 50 particles.

[0302] In a preferred embodiment, step (c) comprises: - (c1) decomposition of N2O via an N2O decomposition catalyst, preferably the N2O decomposition catalyst is a zeolitic material, preferably a zeolite containing a transition metal (including lanthanides), in particular iron, cobalt or copper, more preferably an iron-containing zeolite, even more preferably an iron-containing zeolite of the MFI, BEA, FER, MOR, FAU, AEI and / or MEL structural type, or the device of the invention is correspondingly configured therefor, - (c2) chemical reduction of N2O with a reducing agent via an N2O reduction catalyst, preferably wherein the N2O reduction catalyst comprises a zeolitic material, preferably a zeolite containing a transition metal (including lanthanides), in particular iron, cobalt or copper, more preferably an iron- or copper-containing zeolite, even more preferably an iron- or copper-containing zeolite of the MFI, BEA, FER, MOR, FAU, AEI and / or MEL structural type, or wherein the device of the invention is correspondingly configured, This includes reducing the N2O content in the off-gas by both

[0303] Preferably, the reducing agent in step (c2) is selected from NH3, hydrocarbons, CO, H2 and mixtures thereof, preferably NH3, or the apparatus of the present invention is configured accordingly.

[0304] In a preferred embodiment, the reducing agent in step (c2) is NH, preferably used in an amount of 0.5 to 2.0 molar parts, more preferably 0.8 to 1.8 molar parts, based on the molar fraction of NO to be chemically reduced, i.e., based on the amount of NO at the inlet to the catalyst bed of the NO reduction catalyst, or the apparatus of the present invention is configured accordingly.

[0305] In a preferred embodiment, the reducing agent in step (c2) is NH3, preferably used in an amount of 0.5 to 2.0 molar parts, more preferably 0.8 to 1.8 molar parts, based on the molar amount of NO in the off-gas at the inlet to the catalyst bed of the NO reduction catalyst. If step (d) also proceeds with a catalyst bed of the NO reduction catalyst, this amount is X Any necessary amount of NH3 is added for reduction.

[0306] In another preferred embodiment, the reducing agent is a hydrocarbon or a mixture of two or more hydrocarbons, preferably used in an amount of 0.2 to 1.0 molar part, more preferably 0.2 to 0.7 molar part, based on the molar amount of NO in the off-gas at the inlet to the catalyst bed of the NO reduction catalyst. If step (d) also proceeds with a catalyst bed of the NO reduction catalyst, or if the device of the present invention is configured accordingly, this amount is X Any necessary amount of NH3 for reduction is added as well.

[0307] The reducing agent may also already be present in the off-gas, for example in the form of residual fuel and / or its oxidation products. In that case, the method of the present invention can be used to reduce nitrogen oxides (NO Xand N2O), but also the content of these impurities (residual fuel and / or its oxidation products, in particular NH3 slip), or the device of the invention is configured accordingly.

[0308] In step (d) of the method of the present invention, NO in the off-gas X (i.e., NO and NO2) content is reduced, or the device of the present invention is configured accordingly. X NO by reducing agents via reduction catalysts X Step (d) of the method of the present invention may also be carried out in an off-gas treatment system, or the apparatus of the present invention may be configured accordingly.

[0309] NO X The reduction catalyst preferably comprises a zeolitic material, preferably a zeolite containing a transition metal (including lanthanides), in particular iron, cobalt or copper, more preferably an iron-containing zeolite, even more preferably an iron-containing zeolite of the MFI, BEA, FER, MOR, FAU, AEI and / or MEL structural type.

[0310] Preferably, NO X The reduction catalyst is arranged in a radial basket through which the flow passes axially, or the device of the invention is correspondingly configured.

[0311] Preferably, NO X The reduction catalyst is in particulate form and comprises at least 50 particles.

[0312] Preferably, the reducing agent in step (d) is selected from NH3, hydrocarbons, CO, H2 and mixtures thereof, preferably NH3, or the apparatus of the present invention is configured accordingly.

[0313] Preferably, the reducing agent in step (d) is chemically reduced NO Xor the apparatus of the present invention is configured accordingly.

[0314] In a preferred embodiment, the reducing agent in step (c2) is the same as the reducing agent in step (d), preferably NH3, or the apparatus of the present invention is configured accordingly.

[0315] In addition to NH3, other nitrogen-containing reducing agents, such as hydrogen compounds of nitrogen, such as azanes, hydroxyl derivatives of azanes, and amines, oximes, carbamates, urea, or urea derivatives, are also suitable in principle for use in steps (c2) and / or (d) of the method of the present invention, or the apparatus of the present invention is configured accordingly. Examples of azanes include hydrazine and, very particularly, ammonia. Examples of hydroxyl derivatives of azanes include hydroxylamine. Examples of amines include primary aliphatic amines such as methylamine. An example of a carbamate is ammonium carbamate. Examples of urea derivatives include N,N'-substituted ureas such as N,N'-dimethylurea. Urea and urea derivatives are preferably used in the form of an aqueous solution. Ammonia or substances that release ammonia upon introduction, such as urea or ammonium carbamate, are particularly preferred.

[0316] Particularly preferred process regimes of the invention or corresponding configurations of the inventive apparatus are described in detail below.

[0317] Single Reaction Zone In a preferred embodiment, the off-gas treatment system comprises: as an N2O decomposition catalyst and / or N2O reduction catalyst, and As -NH3 reduction catalysts, zeolitic materials, preferably zeolites containing a transition metal (including lanthanides), in particular iron, cobalt or copper, more preferably iron- or copper-containing zeolites; even more preferably iron- or copper-containing zeolites of the MFI, BEA, FER, MOR, FAU, AEI and / or MEL structural type. (optionally apart from a further reaction zone comprising an NH3 oxidation catalyst, preferably an NH3 oxidation active iron or copper containing zeolite catalyst, see below), N2O and / or NO to off-gas X A device for the metered addition of a reducing agent for is arranged upstream of the single reaction zone in the flow direction of the off-gas.

[0318] Preferably, the device for the metering of a reducing agent is a device for the metering of NH3.

[0319] In a preferred embodiment, NO and / or NO X A further device for metering a reducing agent into the off-gas is arranged upstream of the single reaction zone in the flow direction of the off-gas. Preferably, the further device for metering a reducing agent is a device for metering natural gas.

[0320] In a preferred embodiment, a further reaction zone comprising an NH3 oxidation catalyst, preferably a platinum group metal-free, more preferably a noble metal-free NH3 oxidation catalyst, more preferably an NH3 oxidation active iron or copper containing zeolite catalyst, even more preferably a layered NH3 oxidation catalyst, is located upstream of the single reaction zone in the off-gas flow direction.

[0321] For purposes of this description, "zone configuration" means that the catalyst is in the form of honeycomb bodies, which are optionally combined to form honeycomb body modules, and several honeycomb bodies or honeycomb body modules may be arranged in series in the off-gas flow direction. The upstream honeycomb body or honeycomb body module then forms a first "zone" that functions as a first reaction zone. The downstream honeycomb body or honeycomb body module then forms a second "zone" that functions as a second reaction zone. In this manner, two, three, four, or more zones can be arranged in series to form the zone configuration of the present invention.

[0322] For purposes of explanation, in defining and adding zone configurations, what is meant by "layer configuration" is that the catalytically active material is in the form of a bifunctional two-layer catalyst (bifunctional dual layer catalyst), with the NH3 oxidation catalyst of the present invention preferably being present in the lower of the two layers (lower washcoat) and providing the NO decomposition, NO reduction and / or NO reduction of the present invention. X The reduction catalyst is present on the upper side of the two layers. The bifunctional, two-layer catalyst is preferably in the form of a honeycomb body or honeycomb body module.

[0323] When steps (c) and (d) of the method of the present invention are carried out in downstream first and second reaction zones (zone configuration), the aforementioned layer configuration of the NH3 oxidation catalyst is possible in both reaction zones. In a preferred embodiment, the layer configuration of the NH3 oxidation catalyst is present only in the first reaction zone. In another preferred embodiment, the layer configuration of the NH3 oxidation catalyst is present only in the second reaction zone. In a further preferred embodiment, the layer configuration of the NH3 oxidation catalyst is present in both the first and second reaction zones.

[0324] In a preferred embodiment, the apparatus has a controllable bypass around the NH3 oxidation catalyst, which is preferably platinum group metal-free, more preferably noble metal-free, and more preferably an NH3 oxidation-active iron or copper-containing zeolite catalyst. Preferably, the apparatus is used to separate NH3, NO, and NH3 from the NH3 oxidation catalyst using a device located upstream of a single reaction zone in the off-gas flow direction. X or N2O, preferably NH3 and NO X The concentrations of N2O and N2O in the off-gas are measured, and the opening of the bypass can be controlled by open-loop or closed-loop control.

[0325] In a preferred embodiment, a further reaction zone comprising an NH3 oxidation catalyst, preferably a platinum group metal-free, more preferably a noble metal-free NH3 oxidation catalyst, more preferably an NH3 oxidation active iron or copper containing zeolite catalyst, even more preferably a layered NH3 oxidation catalyst, is located downstream of the single reaction zone in the off-gas flow direction.

[0326] In a preferred embodiment, the NH3 oxidation catalyst, preferably free of platinum group metals, more preferably free of precious metals, more preferably an NH3 oxidation active iron or copper containing zeolite catalyst, is arranged upstream of the off-gas turbine in the flow direction of the off-gas. In another preferred embodiment, the NH3 oxidation catalyst, preferably free of platinum group metals, more preferably free of precious metals, more preferably an NH3 oxidation active iron or copper containing zeolite catalyst, is arranged downstream of the off-gas turbine in the flow direction of the off-gas. Preferably, only one reaction zone is arranged upstream of the off-gas turbine in the flow direction of the off-gas.

[0327] At least two reaction zones arranged in series In a preferred embodiment, the off-gas treatment system comprises a first reaction zone and a second reaction zone arranged downstream in a flow direction of the off-gas, the zones being configured so that the off-gas passes through them in succession; the first reaction zone and the second reaction zone each independently comprise, as an N2O decomposition catalyst and / or an N2O reduction catalyst and / or an NH3 reduction catalyst, a zeolitic material, preferably a zeolite containing a transition metal (including a lanthanide), in particular iron, cobalt or copper, more preferably an iron- or copper-containing zeolite, even more preferably an iron- or copper-containing zeolite of the MFI, BEA, FER, MOR, FAU, AEI and / or MEL structural type; and N2O and / or NO to off-gas X A device for the metered addition of a reducing agent for is arranged downstream of the first reaction zone and upstream of the second reaction zone in the flow direction of the off-gas.

[0328] Preferably, the device for the metering of a reducing agent is a device for the metering of NH3.

[0329] In a preferred embodiment, NO and / or NO XA further device for metering a reducing agent into the off-gas is arranged upstream of the single reaction zone in the flow direction of the off-gas. Preferably, the further device for metering a reducing agent is a device for metering natural gas.

[0330] In a preferred embodiment, NO and / or NO X An additional device for metering a reducing agent into the off-gas is arranged upstream of the first reaction zone in the flow direction of the off-gas. Preferably, the additional device for metering a reducing agent is a device for metering NH3.

[0331] In a preferred embodiment, the first reaction zone comprises a copper-containing zeolite, preferably a copper-containing zeolite of the MFI, BEA, FER, MOR, FAU, AEI and / or MEL structural type, and the second reaction zone comprises an iron-containing zeolite, preferably of the MFI, BEA, FER, MOR, FAU, AEI and / or MEL structural type;

[0332] In a preferred embodiment, a device located downstream of the first reaction zone and upstream of the second reaction zone in the off-gas flow direction is used to separate NH3, NO X or N2O, preferably NH3 and NO X Preferably, at least one device selected from the device for metering addition of a reducing agent, the optional further device for metering addition of a reducing agent, and the optional further device for metering addition of a reducing agent is configured to measure the concentrations of NH3, NO, and N2O in the off-gas. X or N2O, preferably NH3 and NO X and N2O can be controlled by open-loop or closed-loop control, preferably by feed-forward control, depending on the measured concentration in the off-gas.

[0333] In a preferred embodiment, a device located upstream of the first reaction zone in the off-gas flow direction is used to separate NH3, NO Xor N2O, preferably NH3 and NO X Preferably, at least one device selected from the device for metering addition of a reducing agent, the optional further device for metering addition of a reducing agent, and the optional further device for metering addition of a reducing agent is configured to measure the concentrations of NH3, NO, and N2O in the off-gas. X or N2O, preferably NH3 and NO X and N2O can be controlled by open-loop or closed-loop control, preferably by feed-forward control, depending on the measured concentration in the off-gas.

[0334] In a preferred embodiment, a further reaction zone comprising an NH3 oxidation catalyst, preferably a platinum group metal-free, more preferably a noble metal-free NH3 oxidation catalyst, more preferably an NH3 oxidation active iron or copper containing zeolite catalyst; even more preferably a layered NH3 oxidation catalyst, is located downstream of the first reaction zone and upstream of the second reaction zone in the off-gas flow direction.

[0335] In a preferred embodiment, a further reaction zone comprising an NH3 oxidation catalyst, preferably a platinum group metal-free, more preferably a noble metal-free NH3 oxidation catalyst, more preferably an NH3 oxidation active iron or copper containing zeolite catalyst, even more preferably a layered NH3 oxidation catalyst, is arranged downstream of the first reaction zone and upstream of the second reaction zone and upstream of the device for metering addition of a reducing agent and any further device for metering the reducing agent flow-wise to the off-gas.

[0336] In a preferred embodiment, a further reaction zone comprising an NH3 oxidation catalyst, preferably a platinum group metal-free, more preferably a noble metal-free NH3 oxidation catalyst, more preferably an NH3 oxidation active iron or copper containing zeolite catalyst, even more preferably a layered NH3 oxidation catalyst, is located downstream of the second reaction zone in the off-gas flow direction.

[0337] In a preferred embodiment, the apparatus has a controllable bypass around the NH3 oxidation catalyst, which is preferably platinum group metal-free, more preferably noble metal-free, and more preferably an NH3 oxidation-active iron or copper-containing zeolite catalyst. Preferably, the apparatus is configured to generate NH3, NO, and NH4 using a device located upstream of the first reaction zone or upstream of the second reaction zone in the off-gas flow direction. X or N2O, preferably NH3 and NO X The concentrations of N2O and N2O in the off-gas are measured, and the opening of the bypass can be controlled by open-loop or closed-loop control.

[0338] In a preferred embodiment, the NH3 oxidation catalyst, preferably free of platinum group metals, more preferably free of precious metals, more preferably an NH3 oxidation-active iron- or copper-containing zeolite catalyst, is arranged upstream of the off-gas turbine in the flow direction of the off-gas. In another preferred embodiment, the NH3 oxidation catalyst, preferably free of platinum group metals, more preferably free of precious metals, more preferably an NH3 oxidation-active iron- or copper-containing zeolite catalyst, is arranged downstream of the off-gas turbine in the flow direction of the off-gas. Preferably, the first reaction zone is arranged upstream of the off-gas turbine in the flow direction of the off-gas. Preferably, the second reaction zone is arranged upstream of the off-gas turbine in the flow direction of the off-gas.

[0339] In a preferred embodiment, the off-gas treatment system includes a diesel oxidation catalyst, a lean NO X Trap catalyst, NO X It includes at least one additional component selected from an absorption component, a non-catalytic particulate filter, and a catalytic particulate filter, preferably all additional components being located upstream of the second reaction zone in the flow direction of the off-gas.

[0340] Get rid of NO X -N2O removal-Variation 1 In a preferred embodiment, the off-gas treatment system comprises a first reaction zone and a second reaction zone, and the off-gas is passed through the first reaction zone and the second reaction zone in succession over the first reaction zone and the second reaction zone; a reducing agent is added to the off-gas upstream of the first reaction zone; In the first reaction zone, NO in the off-gas X The content is first, NO X NO by reducing agents via reduction catalysts X (step (d)) (de-NO X step (c1), the N2O content in the off-gas may be further reduced by decomposition of N2O via an N2O decomposition catalyst (step (c1)) and / or chemical reduction of N2O with a reducing agent via an N2O reduction catalyst (step (c2)); Additional reducing agent may be added to the off-gas upstream of the second reaction zone; and Then, in the second reaction zone, the N2O content in the off-gas is reduced by decomposition of N2O via an N2O decomposition catalyst (step (c1)) and / or chemical reduction of N2O with a reducing agent via an N2O reduction catalyst (step (c2)) (N2O removal stage), and the NO in the off-gas is X The content is NO X NO via reduction catalyst X may be further reduced by chemical reduction of (step (d)), or the device of the invention is configured accordingly.

[0341] Preferably, the NO in the first reaction zone X The reduction catalyst comprises a conventional, preferably non-zeolitic SCR catalyst, for example based on V2O5-WO3- / TiO2.

[0342] Preferably, the temperature of the off-gas entering the first reaction zone is at most 400°C, preferably at most 350°C, or the apparatus of the invention is configured accordingly.

[0343] Preferably, the NO decomposition catalyst in the second reaction zone comprises a zeolitic material, preferably a zeolite containing a transition metal (including lanthanides), in particular iron, cobalt or copper, more preferably an iron- or copper-containing zeolite, even more preferably an iron- or copper-containing zeolite of the MFI, BEA, FER, MOR, FAU, AEI and / or MEL structural type.

[0344] Preferably, the temperature of the off-gas entering the second reaction zone is in the range of from 300 to 550°C, preferably from 350 to 500°C, or the apparatus of the invention is configured accordingly.

[0345] Preferably, the off-gas after leaving the first reaction zone and before entering the second reaction zone has a NO concentration in the range of 0 to 200 ppmv, preferably 1 to 200 ppmv. X content, and an N2O content in the range of 200 to 2000 ppmv, or the device of the present invention is configured accordingly.

[0346] DeNO X -deN2O- Variation 2 In another preferred embodiment, the off-gas treatment system also comprises a first reaction zone and a second reaction zone, over which the off-gas passes successively through the first reaction zone and the second reaction zone; a reducing agent is added to the off-gas upstream of the first reaction zone; In the first reaction zone, NO in the off-gas X The content is first, NO X NO by reducing agents via reduction catalysts X (step (d)) (de-NO X step (c1), the N2O content in the off-gas may be further reduced by decomposition of N2O via an N2O decomposition catalyst (step (c1)) and / or chemical reduction of N2O with a reducing agent via an N2O reduction catalyst (step (c2)); Additional reducing agent may be added to the off-gas upstream of the second reaction zone; and Then, in the second reaction zone, the N2O content in the off-gas is reduced by decomposition of N2O via an N2O decomposition catalyst (step (c1)) and / or chemical reduction of N2O with a reducing agent via an N2O reduction catalyst (step (c2)) (N2O removal stage), and the NO in the off-gas is X The content is NO X NO via reduction catalyst Xmay be further reduced by chemical reduction of (step (d)), or the device of the invention is configured accordingly.

[0347] Preferably, the NO in the first reaction zone X The reduction catalyst comprises a zeolitic material, preferably a zeolite containing a transition metal (including lanthanides), in particular iron, cobalt or copper, more preferably an iron- or copper-containing zeolite, even more preferably an iron- or copper-containing zeolite of the MFI, BEA, FER, MOR, FAU, AEI and / or MEL structural type.

[0348] Preferably, the temperature of the off-gas entering the first reaction zone is at least 300° C., more preferably at least 350° C., even more preferably at least 400° C. Preferably, the temperature of the off-gas entering the first reaction zone is at most 600° C., more preferably at most 550° C., or the apparatus of the present invention is configured accordingly.

[0349] Preferably, the N2O decomposition catalyst in the second reaction zone is a catalyst for decomposing N2O within the context of the present invention. X The catalyst comprises a sensitive N2O decomposition catalyst, which has already been described in detail above.

[0350] Preferably, the temperature of the off-gas entering the second reaction zone is at least 300° C., more preferably at least 350° C., even more preferably at least 400° C. Preferably, the temperature of the off-gas entering the second reaction zone is at most 600° C., more preferably at most 550° C., or the apparatus of the present invention is configured accordingly.

[0351] Preferably, the off-gas after leaving the first reaction zone and before entering the second reaction zone contains at most 20 ppmv, more preferably at most 10 ppmv, and even more preferably at most 5 ppmv NO. X content, and an N2O content in the range of 200 to 2000 ppmv, or the device of the present invention is configured accordingly.

[0352] Particularly preferred embodiments of deNOX -deN2O- Variation 2 In a particularly preferred embodiment, the off-gas treatment system of the present invention comprises a first catalyst bed and a spatially separated second catalyst bed, the first catalyst bed being arranged upstream of the second catalyst bed in the flow direction of the off-gas, a first device with a first control valve for metered addition of NH to the off-gas being arranged optionally and preferably upstream of the first catalyst bed, and a second device with a second control valve for metered addition of NH to the off-gas being arranged downstream of the first catalyst bed and upstream of the second catalyst bed, whereby further NH is metered into the off-gas, both the first catalyst bed and the second catalyst bed each comprising an iron-containing zeolite catalyst, and (i) in the first catalyst bed (c1), NO is decomposed, and (d) NO is decomposed. X is incompletely chemically reduced with NH, at least a portion of which may preferably originate from the incomplete combustion of NH in step (a) (NH slip), and (ii) in a second catalyst bed (c2), residual N2O is chemically reduced with NH, (c1*) residual N2O may be decomposed, and (d*) residual NO X is chemically reduced with NH3.

[0353] Preferably, the catalytic decomposition of NO in the first catalyst bed is carried out by decomposing NO present in the off-gas. X Co-catalyzed by

[0354] Preferably, NO with NH in the first catalyst bed X The incomplete chemical reduction of NO in the first catalyst bed results in a given residual NO sufficient to provide a co-catalytic effect on the decomposition of NO in the first catalyst bed. X The NO content is obtained by NH3 in the first catalyst bed. X The chemical reduction of NO typically proceeds much more rapidly than the chemical reduction of NO with NH, and the NO chemically reduced in the first catalyst bed X Since the amount of N2O in the first catalyst bed is not total, the extent of any concurrent chemical reduction of N2O by NH3 in the first catalyst bed is typically negligible.

[0355] Preferably, NO XAdditional NH3 for reduction is metered into the off-gas by the first device, preferably under feedback control, i.e., NO3 leaving the first catalyst bed. X A specific value of the concentration of NO is defined as the target value (setpoint), and the NO X The actual concentration of NO is measured (actual value), and if there is a difference between the setpoint and the actual value (control difference), the output of the first control valve is changed to minimize the difference. Preferably, the NO leaving the first catalyst bed X The setpoint concentration of NO, and therefore the amount of additional NH3, is determined by the NO leaving the first catalyst bed. X Preferably, the NO 2 concentration leaving the first catalyst bed is selected to be at most 1000 ppmv, preferably at most 500 ppmv, more preferably at most 100 ppmv. X The setpoint concentration of NO, and therefore the amount of additional NH3, is determined by the NO leaving the first catalyst bed. X The residual concentration of NO in the first catalyst bed is selected to be at least 10 ppmv, preferably at least 20 ppmv, and more preferably at least 40 ppmv. X The expected specific consumption of NH for the chemical reduction of reduced NO is typically X is in the range of 0.9 to 1.1 moles of NH3 per mole and is therefore significantly less than the expected specific consumption of NH3 (mol / mol) in the second catalyst bed.

[0356] Preferably, the temperature of the off-gas leaving the first catalyst bed is in the range of 400 to 550°C.

[0357] Preferably, the off-gas leaving the first catalyst bed is at a pressure above atmospheric pressure, ie ≧1.0 bara, but up to 1.2 bara, more preferably up to 1.1 bara.

[0358] Preferably, the off-gas leaving the first catalyst bed contains at least 5.0%, preferably at least 7.5%, more preferably at least 10%, even more preferably at least 12.5%, most preferably at least 15%, especially at least 17.5% NO Xhas an oxidation degree of

[0359] In a preferred embodiment, the off-gas exiting the first catalyst bed contains NO in the range of 30% to 50%. X has an oxidation degree of

[0360] In another preferred embodiment, the off-gas leaving the first catalyst bed contains NO in the range of 15% to 35%, preferably 15% to 30%. X has an oxidation degree of

[0361] In a more preferred embodiment, the off-gas from the first catalyst bed contains NO in the range of 10% to 20%. X has an oxidation degree of

[0362] In another preferred embodiment, the off-gas exiting the first catalyst bed contains NO in the range of 5% to 15%. X has an oxidation degree of

[0363] Preferably, the residual N2O is decomposed in the second catalyst bed to a residual concentration of N2O exiting the second catalyst bed of at most 20 ppmv, more preferably at most 10 ppmv, even more preferably at most 5 ppmv, and most preferably at most 2 ppmv.

[0364] Preferably, residual NO X is a NO 3 leaving the second catalyst bed of at most 20 ppmv, more preferably at most 10 ppmv, even more preferably at most 5 ppmv, and most preferably at most 2 ppmv. X The toluene is decomposed in the second catalyst bed to a residual concentration of 0.1%.

[0365] Preferably, the additional NH3 is metered by a second device under feedforward control, i.e., NO X The concentrations of N2O and optionally and preferably NH3 are measured upon exiting the first catalyst bed or optionally upon entering the second catalyst bed, respectively, and the amount of off-gas entering the second catalyst bed is determined by the NH3 / NO Xand optionally and preferably using a stored molar ratio (mol / mol) of NH3 / N2O or a coefficient derived therefrom, NO X The amount of NH3 required for reduction, optionally and preferably NO X The total amount required for NH3 reduction and N2O reduction is taken into account, and the calculated result (manipulated variable) is used to change the output of the second control valve to meter the required amount of NH3.

[0366] Preferably, according to the invention, the molar NH3 concentration [NH3] of the off-gas entering the second catalyst bed is 0.7x[N2O] and 1.0x[NO X ] from the sum of 4.0x[N2O] and 2.0x[NO X ], more preferably in the range of 1.0x[NO] and 1.1x[NO X ] from the sum of 3.0x[N2O] and 1.6x[NO X ], and even more preferably in the range of 1.5x[NO] and 1.2x[NO X ] to the sum of 2.5x[N2O] and 1.4x[NO X ], where [NO] is the molar concentration of NO and [NO X ] is the respective NO in the off-gas entering the second catalyst bed X is the molar concentration of

[0367] Preferably, NO X For feed-forward control of the metered addition of NH3 to the second catalyst bed for reduction, a NH3 / NO ratio in the range of 1.0 to 2.0, preferably 1.1 to 1.6, more preferably 1.2 to 1.4 is used. X The molar ratio is selected as follows:

[0368] Preferably, for feed-forward control of the metered addition of NH3 to the second catalyst bed for N2O reduction, a molar ratio of NH3 / N2O in the range of 0.7 to 4.0, preferably 1.0 to 3.0, more preferably 1.5 to 2.5 is selected.

[0369] Preferably, the additional NH3 is used to remove NO in the second catalyst bed.X Since NO is the largest chemical reduction, it cannot be metered by a second device under feedback control, which would limit the usefulness of the results as a control variable. X and only zero or very small residual concentrations of N2O.

[0370] Preferably, the amount of catalyst, i.e., the space velocity (= ratio of off-gas volumetric flow rate to catalyst volume under standard conditions), is selected so that the decomposition of NO in the first catalyst bed is at least 50%, more preferably at least 70%, even more preferably at least 80%, based on the concentration of NO entering the first catalyst bed.

[0371] Preferably, the amount of catalyst and the amount of additional NH3 are such that NO X / N2O molar ratio is selected to be at least 5, more preferably at least 10, even more preferably at least 20.

[0372] The space velocity of the first catalyst bed is preferably 5000 h -1 ~100000h -1 , more preferably 10,000h -1 ~50,000h -1 , and even more preferably 15,000h -1 ~45000h -1 The range is.

[0373] NO leaving the first catalyst bed X When the molar ratio of NH3 / N2O is at least 10, the metered addition of NH3 to the second catalyst bed via the second device X Preferably, this can be done only with respect to the amount of

[0374] Preferably, the temperature of the off-gas entering the first catalyst bed is at least 400° C., more preferably at least 425° C., even more preferably at least 450° C. Preferably, the temperature of the off-gas entering the first catalyst bed is no more than 550° C., more preferably no more than 525° C., even more preferably no more than 500° C. The temperature can be adjusted by means known to those skilled in the art, in particular the design of the heat exchanger and the combustion conditions of NH3.

[0375] Depending on the exothermicity of the chemical reactions taking place in the first and second catalyst beds, the inlet temperature of the off-gas to the first catalyst bed is preferably selected so that the temperature of the off-gas leaving the second catalyst bed is at most 600°C, more preferably at most 550°C, even more preferably at most 520°C.

[0376] The space velocity of the second catalyst bed is preferably 5000 h -1 ~100000h -1 , more preferably 10,000h -1 ~50,000h -1 , and even more preferably 15,000h -1 ~45000h -1 The range is.

[0377] Preferably, the catalyst volume V2 of the second catalyst bed cat Catalyst volume V1 of the first catalyst bed cat catalyst volume ratio (V1 cat / V2 cat ) is in the range of 1 / 2 to 20 / 1, more preferably 1 / 2 to 10 / 1, and even more preferably 1 / 1 to 4 / 1.

[0378] The following conditions are met: the pressure of the off-gas entering the first catalyst bed is at most 5 bara, preferably at most 4 bara; the HO content in the off-gas entering the first catalyst bed is at least 5% by volume, preferably at least 10% by volume, more preferably at least 15% by volume, most preferably at least 20% by volume, in particular at least 25% by volume; NO in the off-gas entering the first catalyst bed Xthe content is at least 500 ppmv, more preferably at least 1000 ppmv, even more preferably at least 1500 ppmv, most preferably at least 2000 ppmv, in particular at least 2500 ppmv; the N2O content in the off-gas entering the first catalyst bed is less than maximum 500 ppmv, more preferably maximum 200 ppmv, even more preferably maximum 100 ppmv, but is at least 5 ppmv, preferably at least 10 ppmv, more preferably at least 50 ppmv; - the off-gas entering the first catalyst bed contains unburned residues of NH3 from the combustion of NH3; - the N2O decomposition catalyst and / or the N2O reduction catalyst is in the form of a honeycomb body; -NO X The reduction catalyst takes the form of a honeycomb body; - the first catalyst bed comprises an Fe zeolite; - the second catalyst bed comprises an Fe zeolite; - the off-gas passes through a temperature control device in which its temperature is regulated before entering the first catalyst bed; - NO leaving the first catalyst bed X the content of which is at most 1000 ppmv, preferably at most 500 ppmv, more preferably at most 300 ppmv, most preferably at most 100 ppmv, but preferably at least 10 ppmv, more preferably at least 20 ppmv, more preferably at least 40 ppmv, most preferably at least 100 ppmv, in particular at least 250 ppmv; the content of NO leaving the first catalyst bed is at most 20 ppmv, more preferably at most 15 ppmv, even more preferably at most 10 ppmv, most preferably at most 5 ppmv, in particular at most 2 ppmv; - there is no intermediate cooling of the off-gas between leaving the first catalyst bed and entering the second catalyst bed; -NO:NO upon entering the first catalyst bed X is at most 0.5, more preferably at most 0.2, even more preferably at most 0.1; -NO:NO upon exiting the first catalyst bed Xis at most 0.20, more preferably at most 0.1, even more preferably at most 0.05; - NH3 supply to the off-gas upstream of the first catalyst bed in the flow direction of the off-gas is optional, if there is a supply, it preferably does not contain NO entering the first catalyst bed X is substoichiometric with respect to the content of; - the supply of NH3 to the off-gas downstream of the first catalyst bed and upstream of the second catalyst bed in the flow direction of the off-gas is sufficient to reduce the NO entering the second catalyst bed X and N2O content is essential and preferably superstoichiometric with respect to the total content, At least one, more than one, or all of the following are satisfied:

[0379] The above method, which uses Fe zeolite catalyst in two catalyst beds, is different from the conventional deNOx method, which uses V2O5 / TiO2 catalyst. X Compared to the law, -Large amounts of NO without the risk of NH3 slip X and - Allows simultaneous complete or substantially complete decomposition of N2O at a relatively low catalyst volume, i.e., at a relatively high space velocity.

[0380] Apart from the operating method of the present invention, this is achieved by the oxidation properties of the Fe zeolite catalyst used according to the present invention. Therefore, in the first catalyst bed, the molar ratio of NO to NO2 is brought as close as possible to the thermodynamic equilibrium position according to the present invention. For example, before entering the first catalyst bed, the NO X The degree of oxidation (molar ratio of NO2 / (NO+NO2)) of NO2 is less than 5%, as expected, due to the combustion of upstream NH3 at very high temperatures and only slow establishment of equilibrium in the gas phase as the off-gas cools, and is therefore far below the thermodynamic equilibrium applicable to the inlet temperature to the first catalyst bed. However, this results in a significant increase in the NO2 present in the off-gas. X Only a small portion of the NO can be decomposed by fast SCR. Xor NO because most of the remaining NO must be destroyed by conventional SCR, which is significantly slower. X This is highly unfavorable for the efficient chemical reduction of

[0381] The selected operating mode of limited metering of NH3 in the first catalyst bed and the ability of the Fe zeolite catalyst to oxidize NO or catalytically accelerate the establishment of equilibrium results in a significantly faster, i.e., more efficient NO oxidation in the first catalyst bed. X reduction and at the same time the remaining NO X NO in X This results in the establishment of the maximum possible degree of oxidation of NO in the second catalyst bed from the very beginning. X can be chemically reduced.

[0382] Therefore, similar to water, high concentrations of NO X The large amount of NH3 required for the complete chemical reduction of NO over an Fe zeolite catalyst X It was found to inhibit the establishment of equilibrium.

[0383] Furthermore, NO X The chemical reduction of NO is also inhibited by NH3 itself at correspondingly high doses of NH3. As a result, the temperature, catalyst amount, and NO X Depending on the content of NH3, even if the amount of NH3 is increased from a fixed amount, the amount of NO X Further increase in decomposition does not occur. If NH3 addition is further increased, under some circumstances, NO X A decrease in degradation may even be observed.

[0384] First, NO in the first catalyst bed X The chemical reduction of NO in the second catalyst bed X This significantly reduces the amount of NH3 required for the chemical reduction of

[0385] In this way, NO XWith the above-mentioned establishment or permanent readjustment of the balance, even the superstoichiometric metering of NH3 according to the invention does not result in NO in the second catalyst bed. X A highly efficient chemical reduction of

[0386] The fact that this is further achieved in accordance with the present invention with zero or little NH3 slip, preferably 10 ppmv or less, more preferably 5 ppmv or less, even more preferably 3 ppmv or less, is similarly due to the oxidation properties of the Fe-zeolite catalyst used in accordance with the present invention. If the inlet temperature of the off-gas to the second catalyst bed is preferably at least 400°C, more preferably at least 425°C, even more preferably at least 450°C, then excess NH3 metered within the scope of the present invention will be selectively oxidized to N2 and HO by the residual oxygen content of the off-gas present.

[0387] All of these benefits cannot be achieved in single or multi-stage configurations when using conventional V2O5 / TiO2-based SCR catalysts, which are also typically used to detoxify off-gases from natural gas-fired reformers. For stability reasons, these conventional SCR catalysts typically cannot operate at temperatures above 400°C, which limits the achievable rate of the decomposition reaction. Also, conventional SCR catalysts have very limited oxidation activity, resulting in a high NO X The establishment or permanent readjustment of the equilibrium is not possible, and these catalysts do not allow for an efficient and N2-selective oxidation of over-metered NH3, instead there is even a risk of the undesired formation of N2O.

[0388] In a variant of the aforementioned embodiment preferred according to the present invention, the first catalyst bed and the second catalyst bed contain the same catalyst. In a preferred embodiment, the second device with a second control valve for metering NH3 into the off-gas is omitted, but it is preferred to omit the spatial separation of the first catalyst bed from the second catalyst bed, in which case there is actually only a single shared catalyst bed, and the first device with a first control valve for metering NH3 into the off-gas is preferably located upstream of this shared catalyst bed. Additional NH3 is preferably metered into the off-gas via the first device, preferably under feed-forward control, i.e., the NO in the off-gas upstream of the shared catalyst bed is preferably metered into the off-gas via the first device. X The concentrations of NO and NH are measured, the amount of off-gas entering the shared catalyst bed is taken into account to calculate the additional amount of NH still required, and the calculated result (manipulated variable) is used to change the setting of the first control valve to meter the amount of additional NH still required. Preferably, in such an embodiment, an NH oxidation catalyst is placed downstream of the shared catalyst bed to reduce possible NH slip.

[0389] Co-firing of NH3 and CH4 - reducing hydrogen cyanide content In a preferred embodiment, in step (a), a mixture of CH4 and NH3 with air and / or oxygen is combusted to produce CO2, CO and HCN, and NO X and produces an off-gas that further contains N2O.

[0390] In these cases, the first catalyst bed preferably performs the additional function of catalytic cracking of HCN by hydrolysis with water present in the off-gas to give CO and NH3 products as follows: HCN + HO ⇔ CO + NH3. The CO and NH3 products formed are then preferably converted into NO in the first catalyst bed, as for NH3. X For reduction, and with respect to CO, preferably for N2O reduction in the second catalyst bed, N2O and NO in the off-gas X It can be used as a reducing agent for the removal of

[0391] The content of HCN in the off-gas as a pollutant and greenhouse gas must be limited or eliminated due to its toxicity and longevity in the atmosphere and its absorption in infrared light. When HCN is decomposed in accordance with the present invention over a zeolite catalyst in the first catalyst bed containing CO and NH3, NO in the second catalyst bed is decomposed. X The fact that cracking products are formed that are suitable as reducing agents for further off-gas post-treatment of NO and NO completes the uniqueness of the inventive off-gas treatment on a zeolite catalyst. Conventional SCR catalysts based on vanadium oxide are virtually inactive for HCN hydrolysis and are therefore not suitable for HCN removal from off-gas. In this case, a downstream oxidation catalyst must be used.

[0392] De-N2O-de-NO X. In a further preferred embodiment, the off-gas treatment system comprises a first reaction zone and a second reaction zone, and the off-gas passes through the first reaction zone and the second reaction zone in succession over the first reaction zone and the second reaction zone; a reducing agent is added to the off-gas between the first reaction zone and the second reaction zone; In the first reaction zone, the N2O content in the off-gas is first reduced by decomposition of N2O via an N2O decomposition catalyst (step (c1)) (N2O removal stage); and Then, in the second reaction zone, NO in the off-gas X The content is NO X NO by reducing agents via reduction catalysts X (step (d)) (de-NO X After the decomposition of N2O via an N2O decomposition catalyst (step (c1)), the N2O content in the off-gas may be further reduced by further decomposition of N2O via an N2O decomposition catalyst (step (c1)) and / or chemical reduction of N2O with a reducing agent via an N2O reduction catalyst (step (c2)), or the apparatus of the present invention is configured accordingly.

[0393] Preferably, no reducing agent is added to the off-gas upstream of the first reaction zone, or the apparatus of the present invention is configured accordingly.

[0394] Such a process regime is particularly preferred according to the present invention, as it allows the initial production of NO without consuming a reducing agent. X This allows for the adjustment of the relative content of NO and NO in the first reaction zone. X The NO content in the off-gas is selectively reduced by decomposition, while the NO content remains substantially unchanged. X and to the extent necessary to establish the desired relative content of N2O. For economic reasons, it is preferred that the selected amount of N2O decomposition catalyst is not so large as to achieve a quantitatively complete reduction (0 ppmv) of the N2O content in the off-gas by decomposition; instead, a compromise is found between the rate of decomposition and the size of the N2O decomposition catalyst.

[0395] In a preferred embodiment, the NO decomposition catalyst in the first reaction zone comprises a zeolitic material, preferably a zeolite containing a transition metal (including lanthanides), in particular iron, cobalt or copper, more preferably an iron- or copper-containing zeolite, even more preferably an iron- or copper-containing zeolite of the MFI, BEA, FER, MOR, FAU, AEI and / or MEL structural type.

[0396] In another preferred embodiment, the NO decomposition catalyst in the first reaction zone is a NO decomposition catalyst within the context of the present invention already described above. X Contains a sensitive N2O decomposition catalyst.

[0397] In a preferred embodiment, NO in the second reaction zone X The reduction catalyst comprises a zeolitic material, preferably a zeolite containing a transition metal (including lanthanides), in particular iron, cobalt or copper, more preferably an iron- or copper-containing zeolite, even more preferably an iron- or copper-containing zeolite of the MFI, BEA, FER, MOR, FAU, AEI and / or MEL structural type.

[0398] Preferably, the first reaction zone and the second reaction zone are operated at different temperature levels, or the apparatus of the present invention is configured accordingly.

[0399] Preferably, The NO decomposition catalyst in the first reaction zone X the off-gas temperature of the first reaction zone is preferably at least 450°C, more preferably at least 500°C, even more preferably at least 550°C, and most preferably at least 600°C, or the apparatus of the present invention is configured accordingly; and -NO in the second reaction zone X The reduction catalyst is a zeolite material, preferably a zeolite containing a transition metal (including lanthanides), in particular iron, cobalt or copper, more preferably an iron- or copper-containing zeolite, even more preferably an iron- or copper-containing zeolite of the MFI, BEA, FER, MOR, FAU, AEI and / or MEL structural type, the off-gas temperature of the second reaction zone is preferably 550°C or less, more preferably 500°C or less, even more preferably 450°C or less, most preferably 400°C or less, and NO X In addition to the chemical reduction of NO, the (residual) NO content is preferably further reduced in a second reaction zone by decomposition and / or chemical reduction, or the device of the present invention is configured accordingly.

[0400] Preferably, in the first reaction zone, the space velocity is set, or the apparatus of the present invention is configured accordingly, such that the NO content in the off-gas is reduced in the first reaction zone by at most 95%, preferably at most 90%, more preferably at most 85%, based on the NO content in the off-gas entering the first reaction zone.

[0401] In a preferred embodiment, the NO content in the off-gas after leaving the first reaction zone and before entering the second reaction zone is at least 20 ppmv, more preferably at least 40 ppmv, even more preferably at least 60 ppmv, most preferably at least 80 ppmv, especially at least 100 ppmv, or the apparatus of the invention is configured accordingly.

[0402] In a preferred embodiment, the NO content in the off-gas after leaving the first reaction zone and before entering the second reaction zone is at most 400 ppmv, more preferably at most 300 ppmv, even more preferably at most 200 ppmv, most preferably at most 100 ppmv, especially at most 50 ppmv, or the apparatus of the invention is configured accordingly.

[0403] Preferably, in the second reaction zone, the space velocity is set, or the apparatus of the present invention is configured accordingly, such that the NO content in the off-gas is further reduced in the second reaction zone by at least 30%, preferably at least 40%, more preferably at least 50%, based on the NO content in the off-gas entering the second reaction zone. Since a reducing agent is present in the second reaction zone, further reduction of the NO content in the second reaction zone can be achieved by both decomposition by an NO decomposition catalyst (step (c1)) and chemical reduction by a reducing agent via an NO reduction catalyst (step (c2)), or the apparatus of the present invention is configured accordingly.

[0404] Preferably, in the second reaction zone, the N2O content in the off-gas is further reduced by chemical reduction of N2O with a reducing agent via an N2O reduction catalyst (step (c2)), or the apparatus of the present invention is configured accordingly.

[0405] Furthermore, NO X The content is determined by the following equation: XIt is reduced by chemical reduction with a reducing agent over a reduction catalyst, or the device of the present invention is configured accordingly, which reduction typically has fast kinetics and preferably proceeds substantially quantitatively in accordance with the present invention.

[0406] Closed-Loop Control Regardless of the respective process regime, the method of the present invention is preferably under closed-loop control, or the apparatus of the present invention is configured accordingly.

[0407] In a preferred embodiment, depending on the operating mode of the internal combustion engine, the first measurement variable used in the closed-loop control of the method of the invention is at least one parameter characteristic of the current operating state of the internal combustion engine, or the device of the invention is configured accordingly. Preferably, this first measurement variable or parameter is selected from the group consisting of combustion temperature, NH3 consumption, rotational speed, and noise emitted by the internal combustion engine.

[0408] The characteristics of off-gases leaving an internal combustion engine, in particular NO in off-gas X content, -NO in off-gas X degree of oxidation, - N2O content in the off-gas, the content of other components in the off-gas, such as H2O, O2, and N2; -offgas temperature, -offgas pressure, and -offgas volume flow rate, Depending on the process conditions, the NO in the off-gas X and N2O content can be optimized or the device of the present invention can be configured accordingly to achieve an efficient and economically viable reduction in the content of N2O.

[0409] Thus, in a preferred embodiment, the second measurement variable measured for the closed-loop control of the method of the invention is at least one parameter characteristic of the current state of the off-gas before it enters the off-gas treatment system, and is measured in addition to or instead of the first measurement variable upon exit from the internal combustion engine and / or upon entry into the off-gas treatment system, or the device of the invention is configured accordingly. Preferably, this second measurement variable or parameter is the NO 2 in the off-gas. X Content, NO in off-gas X the degree of oxidation of the off-gas, the NO content in the off-gas, the content of other components in the off-gas, such as H0, O, and N, the off-gas temperature, the off-gas pressure, and the volumetric flow rate of the off-gas, or the device of the present invention is configured accordingly.

[0410] In a preferred embodiment, the third measurement variable measured for the closed-loop control of the method of the invention is, in addition to or instead of the first measurement variable, and in addition to or instead of the second measurement variable, at least one parameter characteristic of the current state of the off-gas at the outlet of the off-gas treatment system, measured at the outlet of the off-gas treatment system, or the device of the invention is configured accordingly. Preferably, this third measurement variable or parameter is NO 2 in the off-gas. X Content, NO in off-gas X the degree of oxidation of the off-gas, the NO content in the off-gas, the content of other components in the off-gas, such as HO, O, and N, the off-gas temperature, the off-gas pressure, and the volumetric flow rate of the off-gas, or the device of the present invention is configured accordingly.

[0411] In a preferred embodiment, particularly when the off-gas treatment system comprises a first reaction zone and a second reaction zone through which the off-gas passes successively and a reducing agent is supplied between the first and second reaction zones, for closed-loop control of the method of the invention, at least one parameter characteristic of the current state of the off-gas after it leaves the first reaction zone and before it enters the second reaction zone is measured as a fourth measurement variable at the outlet from the first reaction zone and before it enters the second reaction zone in addition to or instead of the first measurement variable, in addition to or instead of the second measurement variable, in addition to or instead of the third measurement variable, or the device of the invention is configured accordingly. Preferably, this fourth measurement variable or parameter is NO in the off-gas. X Content, NO in off-gas X the degree of oxidation of the off-gas, the NO content in the off-gas, the content of other components in the off-gas, such as HO, O, and N, the off-gas temperature, the off-gas pressure, and the volumetric flow rate of the off-gas, or the device of the present invention is configured accordingly.

[0412] Depending on the first and / or second and / or third and / or fourth measured variable, at least one manipulated variable is preferably changed for open-loop or closed-loop control of the method according to the invention, or the device according to the invention is configured accordingly. Preferably, the open-loop or closed-loop control of the method is therefore based on, or the device according to the invention is configured accordingly, on, the first and / or second and / or third and / or fourth measured variables by controlled change of the manipulated variables (control variables), preferably by controlled change of the amount of reducing agent metered.

[0413] Regarding the preferred instrumental variables, -Conditions that can be changed in the short term only with relatively high equipment complexity, if at all; conditions that can be changed quickly and are therefore more suitable for closed-loop control; A distinction needs to be made between

[0414] Preferably, according to the present invention, - the dimensions of the off-gas treatment device, the nature, amount and flow direction of the N2O decomposition catalyst and / or N2O reduction catalyst, -NO X the nature, amount and flow direction of the reduction catalyst; - type of reducing agent, -offgas pressure, The location of the reducing agent supply, and the relative arrangement of the first and second reaction zones; are not manipulated variables, i.e., these parameters preferably remain constant during the execution of the method of the present invention, or the apparatus of the present invention is configured accordingly.

[0415] However, these parameters can be selected or adjusted in the planning and design of the off-gas treatment system so that they can be controlled within wide ranges, and in this way it is also possible to react to short-term changes, for example, with respect to the off-gas being treated. X and an efficient and economically viable reduction of the N2O content is ensured without undesired breakthrough of the reducing agent (called slip).

[0416] The preferred manipulated variables (control variables) according to the present invention are as follows:

[0417] - amount of reducing agent; - Off-gas temperature, if appropriate; and - Catalyst temperature, if appropriate.

[0418] Preferably, the off-gas leaving the off-gas treatment system has a residual NO of at most 20 ppmv, preferably at most 15 ppmv, more preferably at most 10 ppmv, even more preferably at most 7.5 ppmv, most preferably at most 5.0 ppmv, especially at most 2.5 ppmv. X The device of the present invention may be configured accordingly.

[0419] Preferably, the off-gas leaving the off-gas treatment system has a residual NO content of at most 20 ppmv, preferably at most 15 ppmv, more preferably at most 10 ppmv, even more preferably at most 7.5 ppmv, most preferably at most 5.0 ppmv, especially at most 2.5 ppmv, or the apparatus of the present invention is configured accordingly. [Brief explanation of the drawings]

[0420] [Figure 1] A particularly preferred DeN2O-DeNOx variant is shown having two catalyst beds without an additional NH3 oxidation catalyst. [Figure 2] A particularly preferred DeN2O-DeNOx variant is shown having two catalyst beds, an additional NH3 oxidation catalyst in a separate upstream third reaction zone, and a bypass around the upstream oxidation catalyst. [Figure 3] A particularly preferred DeN2O-DeNOx variant is shown having two catalyst beds and an additional NH3 oxidation catalyst in a layered configuration, incorporated in the second zone (second catalyst bed) of the DeN2O-DeNOx system. [Figure 4] 1 shows a variation having a catalyst bed that does not contain an NH3 oxidation catalyst. [Figure 5] A variation is shown having a catalyst bed containing an additional NH3 oxidation catalyst that is free of Pt group metals, preferably no precious metals. DETAILED DESCRIPTION OF THE INVENTION

[0421] A preferred embodiment of the present invention is shown schematically in FIGS.

[0422] FIG. 1 shows a particularly preferred de-NO-de-NO catalyst system having two catalyst beds without an additional NH oxidation catalyst. XA variant is shown. The internal combustion engine comprises, for example, in the illustrated embodiment, a turbocharged reciprocating piston engine operating solely on ammonia as fuel (single fuel). Combustion air is supplied to the intake side of the turbocompressor (2) via an air manifold (1). The compressed air is directed to the cylinders of the reciprocating piston engine (8) via an air charge cooler (3) and an accumulator (4). Similarly, fuel from an ammonia tank (7) is supplied to the engine via an accumulator (6). The ammonia is burned in the engine compartment, and the off-gas flows into an off-gas duct to the exhaust gas aftertreatment system, essentially at increased pressure by an off-gas turbine (14).

[0423] The off-gas treatment system preferably comprises two spatially separated catalyst beds (12 and 13), each containing an Fe-zeolite catalyst.

[0424] In the first catalyst bed (12) (upstream of the second catalyst bed), NO X is reduced, NO is catalytically decomposed, and the (residual) NO present in the off-gas is X Co-catalyzed by content.

[0425] NO X is reduced by NH3 present in the off-gas (due to incomplete combustion of NH3 in the calcination system or combustion device), and optionally, additional NH3 added via a metering device (10) is added to the off-gas to provide a defined residual NO X value (enough to provide a co-catalytic effect on the decomposition of NO, which also occurs in the first bed). X The addition of NH3 to the reduction is now under closed-loop control by the so-called feedback control method (11a). X A specific value of the outlet concentration is defined as the target value (set point), and NO XThis means that the actual outlet concentration of NH3 is measured downstream of the first bed (actual value). If there is a difference between the setpoint and the actual value (control difference), the degree of actuation of the appropriate NH3 metering valve (actuator) is adjusted to minimize the difference. Due to incomplete combustion of a relatively high residual ammonia concentration in the off-gas exiting the reciprocating piston engine (8) towards the first catalyst bed (12), the off-gas metering device (10) can be completely closed. In borderline cases of engine design (corresponding degrees of incomplete combustion at all relevant engine operating points), it becomes obsolete and may even be omitted thereafter.

[0426] In the second catalyst bed (13) (downstream of the first catalyst bed), (i) residual NO (originating from the first catalyst bed) X A further, preferably substantially complete, reduction in concentration is achieved by further addition of NH3 (metering device (9)) and NO X is preferably decomposed to a residual concentration of <20 ppmv, preferably <10 ppmv, more preferably <5 ppmv, even more preferably <2 ppmv. Furthermore, also preferably, substantially complete decomposition of N2O is carried out in a second catalyst bed by chemical reduction of N2O with NH3 (which is carried out in parallel, or preferably in combination with NO X After the complete reduction of N2O, N2O is preferably decomposed to a residual concentration of <20 ppmv, preferably <10 ppmv, more preferably <5 ppmv, and even more preferably <2 ppmv.

[0427] Preferably, the additional NH3 is metered by a second device under feedforward control, i.e., NO X The concentrations of N2O and optionally and preferably NH3 are measured upon exiting the first catalyst bed or optionally upon entering the second catalyst bed, respectively, and the amount of off-gas entering the second catalyst bed is determined by the NH3 / NO X and optionally and preferably using a stored molar ratio (mol / mol) of NH3 / N2O or a coefficient derived therefrom, NO X The amount of NH3 required for reduction, optionally and preferably NO XThe total amount required for NH3 reduction and N2O reduction is taken into account, and the calculated result (manipulated variable) is used to change the output of the second control valve to meter the required amount of NH3.

[0428] Preferably, according to the invention, the molar NH3 concentration [NH3] of the off-gas entering the second catalyst bed is 0.7x[N2O] and 1.0x[NO X ] from the sum of 4.0x[N2O] and 2.0x[NO X ], more preferably in the range of 1.0x[NO] and 1.1x[NO X ] from the sum of 3.0x[N2O] and 1.6x[NO X ], and even more preferably in the range of 1.5x[NO] and 1.2x[NO X ] to the sum of 2.5x[N2O] and 1.4x[NO X ], where [NO] is the molar concentration of NO and [NO X ] is the respective NO in the off-gas entering the second catalyst bed X is the molar concentration of

[0429] Preferably, NO X For feed-forward control of the metered addition of NH3 to the second catalyst bed for reduction, a NH3 / NO ratio in the range of 1.0 to 2.0, preferably 1.1 to 1.6, more preferably 1.2 to 1.4 is used. X The molar ratio is selected as follows:

[0430] Preferably, for feed-forward control of the metered addition of NH3 to the second catalyst bed for N2O reduction, a molar ratio of NH3 / N2O in the range of 0.7 to 4.0, preferably 1.0 to 3.0, more preferably 1.5 to 2.5 is selected.

[0431] Conventional feedback control of NH3 addition, as in the first catalyst bed, is, according to the present invention, performed when the objective is complete NO addition in the second catalyst bed. X reduction, so the results are very small or zero NO Xand residual concentrations of N2O, which are not preferred in the second catalyst bed because their usefulness as reference variables for closed-loop control purposes is very limited.

[0432] The amount of NH3 added to the first catalyst bed is preferably adjusted to account for the NO at the outlet of the first catalyst bed. X According to the invention, the concentration is selected to be <1000 ppmv, preferably <500 ppmv, in particular <100 ppmv. According to the invention, the minimum NO concentration at the outlet of the first catalyst bed is X The concentration should preferably be >10 ppmv, preferably >20 ppmv, more preferably >40 ppmv. NO in the first catalyst bed in the operating mode of the present invention X The expected NH consumption rate for the reduction is X 0.9-1.1 moles of NH3 per mole of NH3, and is therefore significantly less than the expected NH3 consumption rate in the second catalyst bed.

[0433] In the preferred form of the invention shown here, no further NH3 oxidation catalyst is used, except for the oxidation-active Fe(Cu) zeolite catalyst. Thus, the operating mode of the internal combustion engine (8), which is preferably a reciprocating piston engine for marine propulsion, is such that the off-gas leaving the internal combustion engine (8) is a mixture of NH3 / NO X and configured at the main operating point to have a maximum residual NH concentration such that the aforementioned molar ratio of NH / N can be established. In addition to the preferred lean operating mode of combustion, further internal combustion engine measures are conceivable for this purpose, such as advantageous closed-loop control of the charge air cooling (3).

[0434] The amount of catalyst, i.e. the space velocity (= ratio of off-gas volumetric flow rate to catalyst volume under standard conditions) of the first catalyst bed is preferably selected to give a NO decomposition of more than 50%, more preferably more than 70%, most preferably more than 80%.

[0435] In particular, the space velocity of the first catalyst bed and the amount of NH3 added are such that at the outlet of the first catalyst bed, NO is >5, preferably >10, in particular >20. X / N2O molar ratio.

[0436] Preferably, the space velocity of the first catalyst bed is 5000 h -1 ~100000h -1 , especially 10000h -1 ~50,000h -1 , most preferably 15000h -1 ~45000h -1 is.

[0437] NO at the outlet of the first catalyst bed X When the ratio of NH3 to NO2 is >10, in a preferred embodiment, the complete addition of NH3 to the second catalyst bed is X This can only be done with respect to the amount of

[0438] According to the invention, the temperature of the off-gas entering the first catalyst bed (via the operating mode of the internal combustion engine and / or additional cooling / heating means) is preferably reduced to a value above 300°C, preferably above 400°C, in particular above 450°C, and at the same time below 550°C, preferably below 525°C, in particular below 500°C.

[0439] Depending on the exothermicity of the chemical reactions taking place in the catalyst beds, the inlet temperature of the off-gas to the first catalyst bed is selected so that the temperature of the off-gas leaving the second catalyst bed does not exceed a value of 600°C, preferably 550°C, in particular 520°C.

[0440] The space velocity of the second catalyst bed is preferably 5000 h -1 ~100000h -1 , especially 10000h -1 ~50,000h -1 , most preferably 15000h -1 ~45000h -1 is.

[0441] The ratio of the catalyst volume from the first catalyst bed to the second catalyst bed (V cat / V2 cat ) is preferably 1 / 2 to 20 / 1, more preferably 1 / 2 to 10 / 1, and most preferably 1 / 1 to 4 / 1.

[0442] The above method using an Fe zeolite catalyst is different from the conventional method using a V2O5 / TiO2 catalyst for NO removal. X Compared to the law, Large amounts of NO without the risk of NH3 slip X to completely or almost completely decompose Allows simultaneous, complete, or nearly complete decomposition of the NO present in the off-gas, or this can be done within the limits specified by the minimum possible supply of additional ammonia, i.e., the rate of the NO decomposition reaction can also be maximized; All of the above can be done with a relatively low catalyst volume, i.e., a relatively high space velocity.

[0443] Apart from the above-mentioned operating method of the present invention, this is achieved by the oxidation properties of the Fe zeolite catalyst used according to the present invention. Therefore, in the first catalyst bed, the molar ratio of NO to NO2 is as close as possible to the thermodynamic equilibrium position according to the present invention. For example, before entering the first catalyst bed, X The degree of oxidation (molar ratio of NO2 / (NO+NO2)) of NH3 (due to the very high temperature upstream combustion and only slow establishment of equilibrium in the gas phase as the off-gas cools) is <5%, as expected, and therefore far below the thermodynamic equilibrium applicable to the inlet temperature to the first catalyst bed. However, this results in a significant increase in the NO2 present in the off-gas. X Only a small fraction of NO can proceed through fast SCR. X Since most of the NO or most of the remaining NO must proceed through normal SCR, which is obviously slow, X This is very detrimental to the efficiency of the reduction.

[0444] The selected operating mode of limited metering of NH3 in the first catalyst bed and the ability of the Fe zeolite catalyst to oxidize NO or catalytically accelerate the establishment of equilibrium results in a significantly faster, i.e., more efficient NO oxidation in the first catalyst bed. X reduction and at the same time the remaining NOX NO in X This results in the establishment of the maximum possible degree of oxidation of NO in the second catalyst bed from the very beginning. X Refund becomes possible.

[0445] Therefore, similar to water, high concentrations of NO X The large amount of NH3 required for the complete reduction of NO over the Fe zeolite catalyst X It was found to inhibit the establishment of equilibrium.

[0446] Furthermore, NO X The reduction of NO is also inhibited by NH3 itself at correspondingly high doses of NH3. As a result, the temperature, amount of catalyst, and NO X Depending on the content, NO increases with the addition of NH3 from a constant amount of NH3 X Further increase in decomposition does not occur. If NH3 addition is further increased, under some circumstances, NO X A decrease in degradation may even be observed.

[0447] NO in the first catalyst bed X Pre-reduction of NO in the second bed X The amount of NH3 required for reduction is significantly reduced.

[0448] In this way, NO X With the above-mentioned establishment or permanent readjustment of the equilibrium, even the superstoichiometric metered addition of NH3 according to the invention results in a very efficient NO X Reduction is also possible in the second bed.

[0449] FIG. 2 shows a particularly preferred De-N2O-De-NO2 system having two catalyst beds, an additional NH3 oxidation catalyst in a separate upstream third reaction zone, and a bypass around the upstream oxidation catalyst. X A modified example is shown.

[0450] In the preferred form of the invention shown here, in addition to the oxidation-active Fe(Cu) zeolite catalyst, a further ammonia oxidation catalyst (16) is used that is free of Pt group metals, more preferably free of precious metals. Such a variant is useful when the operating mode of the internal combustion engine (8), preferably a reciprocating piston engine for marine propulsion, is such that the NH3 / NO X And it is preferred if it is not configurable so that the above advantageous molar ratio of NH3 / N2O can be established.

[0451] Conversely, a higher stoichiometric ammonia excess is already emerging from the internal combustion engine at the relevant operating conditions, and the first de-NO-de-NO at the relevant operating conditions X If the inhibitory effect on the reaction zone cannot be eliminated, an upstream oxidation catalyst (16) can be used that is free of Pt group metals, more preferably free of precious metals, and optionally has a bypass (17) that can be controlled by closed loop control.

[0452] FIG. 3 shows a system with two catalyst beds and an additional NH3 oxidation catalyst in a layered configuration, X Particularly preferred is a deNO-deNO catalyst incorporated in the second zone (second catalyst bed) of the system. X A modified example is shown.

[0453] Such a variant is such that the operating mode of the internal combustion engine (8), preferably a reciprocating piston engine for marine propulsion, is such that the NH3 / NO X and NH3 / N2O NO X It is preferable if the above advantageous molar ratio of NO to NO is not configurable, but the first de-NO and de-NO are de-NO under the relevant operating conditions. X The inhibitory effect resulting from high ammonia concentrations in the reaction zone can be eliminated or is negligibly low.

[0454] The integration of a Pt-group metal-free, and more preferably noble metal-free, NH3 oxidation catalyst ultimately reduces the NH3 / NO3 ratio upon entering the second catalyst bed. X and has the effect of broadening the preferred ratio of NH3 / N2O.

[0455] When a Pt-group metal-free, more preferably noble metal-free, NH3 oxidation catalyst constitutes or is incorporated into the final reaction zone (second catalyst bed) for the purpose of better ammonia utilization, the oxidation of excess ammonia to nitrogen (NO X Implementation in a layered configuration is preferred because it is possible to achieve better overall selectivity in CO (and not N2O).

[0456] FIG. 4 shows a variation with a catalyst bed that does not contain an NH3 oxidation catalyst.

[0457] The internal combustion engine includes, for example, in the illustrated embodiment, a turbocharged reciprocating piston engine operating solely on ammonia as fuel (single fuel).

[0458] Combustion air is supplied to the intake side of the turbo compressor (2) via an air manifold (1). The compressed air is directed to the cylinders of a reciprocating piston engine (8) via an air charge cooler (3) and an accumulator (4). Similarly, fuel from an ammonia tank (7) is supplied to the engine via an accumulator (6). The ammonia is burned in the engine compartment, and the off-gas flows into an off-gas duct to the exhaust gas aftertreatment system at pressure built up by an off-gas turbine (14).

[0459] The off-gas treatment system preferably comprises a single catalyst bed (12) containing an Fe-zeolite catalyst.

[0460] FIG. 5 shows a variation with a catalyst bed containing an additional NH3 oxidation catalyst that is free of Pt group metals, preferably no precious metals.

[0461] The internal combustion engine, for example, in the illustrated embodiment, includes a turbocharged reciprocating piston engine that runs solely on ammonia as fuel (single fuel). Combustion air is supplied to the intake side of the turbocompressor (2) via an air manifold (1). The compressed air is directed to the cylinders of the reciprocating piston engine (8) via an air charge cooler (3) and an accumulator (4). Similarly, fuel from an ammonia tank (7) is supplied to the engine via an accumulator (6). The ammonia is burned within the engine compartment, and the off-gas flows into an off-gas duct to the exhaust gas aftertreatment system at pressure built up by an off-gas turbine (14).

[0462] The off-gas treatment system preferably includes a single catalyst bed (12) containing an Fe zeolite catalyst and a Pt metal-free NH3 oxidation catalyst arranged in a layered configuration, preferably forming a flow path for deNO X -N2O removal catalyst.

[0463] A particularly preferred embodiment of the present invention is summarized in the following sentence:

[0464] Sentence 1: NO in the off-gas of an NH3-powered internal combustion engine X and N2O, comprising: (a) burning NH3 to power an internal combustion engine to produce N2, HO, NO X (b) transferring the off-gas to an off-gas treatment system; (c) reducing the N2O content in the off-gas by (c1) decomposing N2O via an N2O decomposition catalyst and / or (c2) chemically reducing N2O with a reducing agent via an N2O reduction catalyst; and (d) removing N2O from the off-gas. X NO by reducing agent through reduction catalyst X By chemically reducing NO in the off-gas X and reducing the content.

[0465] Sentence 2: N2O decomposition catalyst and / or N2O reduction catalyst and / or NOX The method of sentence 1, wherein the reduction catalysts independently comprise a zeolite material, preferably a zeolite containing a transition metal (including a lanthanide), in particular iron, cobalt or copper, more preferably an iron- or copper-containing zeolite, and even more preferably an iron- or copper-containing zeolite independently of the MFI, BEA, FER, MOR, FAU, AEI and / or MEL structural type.

[0466] Sentence 3: The method of sentence 1 or 2, wherein the N2O decomposition catalyst and the N2O reduction catalyst are formed from the same material.

[0467] Sentence 4: N2O decomposition catalyst and NO X The method of any of the preceding sentences, wherein the reduction catalysts are formed from the same material.

[0468] Sentence 5: NO reduction catalyst and NO X The method of any of the preceding sentences, wherein the reduction catalysts are formed from the same material.

[0469] Sentence 6: N2O decomposition catalyst, N2O reduction catalyst, and NO X The method of any of the preceding sentences, wherein the reduction catalysts are formed from the same material.

[0470] Sentence 7: The method of any of the preceding sentences, wherein the combustion of NH3 in step (a) is not carried out via a catalyst.

[0471] Sentence 8: The method of any of the preceding sentences, wherein NH3 is combusted in step (a) in a mixture with a further combustible gas, preferably the further combustible gas being selected from (i) H2, (ii) fossil fuels, preferably hydrocarbons and hydrocarbon mixtures, more preferably methane, ethane, propane, butane, natural gas, gasoline and / or diesel, (iii) alcohols, preferably methanol and / or ethanol, and mixtures thereof. Sentence 9: A method according to any of the preceding sentences, wherein NH3 is burned in a mixture with H2 in step (a).

[0472] Sentence 10: The method of sentence 9, wherein step (a) comprises the component steps of (a1) thermally and / or catalytically cracking NH3 to produce a cracked gas comprising N2, H2, and optionally residual NH3, (a2) optionally mixing the cracked gas with additional NH3 to produce a mixture comprising H2 and NH3, and (a3) ​​combusting the cracked gas or mixture. Sentence 11: The method according to sentence 9 or 10, wherein the proportion of H2 in the mixture with NH3 is at most 80 mol%, more preferably at most 70 mol%, even more preferably at most 60 mol%, most preferably at most 50 mol%, in particular at most 40 mol%.

[0473] Sentence 12: A method according to any of sentences 9 to 11, wherein the proportion of H2 in the mixture with NH3 is at least 10 mol%, more preferably at least 20 mol%, even more preferably at least 30 mol%, most preferably at least 40 mol%, in particular at least 50 mol%.

[0474] Sentence 13: The method of any of sentences 9 to 12, wherein the molar ratio of H2:NH3 in the mixture ranges from 45:55 to 90:10, preferably from 50:50 to 85:15, more preferably from 55:45 to 80:20, even more preferably from 60:40 to 75:25, and most preferably from 65:35 to 70:30.

[0475] Sentence 14: The method of any of sentences 9 to 13, wherein the air ratio λ is in the range of 0.9 to 1.7, more preferably 1.0 to 1.6, even more preferably 1.1 to 1.5, and most preferably 1.2 to 1.4.

[0476] Sentence 15: The method of any of sentences 1 to 7, wherein in step (a) only NH3 is combusted, and thus NH3 is the only combustible gas combusted.

[0477] Sentence 16: A method as recited in any of the preceding sentences, wherein the internal combustion engine is mounted on a vehicle and used to propel the vehicle.

[0478] Sentence 17: The method of sentence 16, wherein the vehicle is a watercraft.

[0479] Sentence 18: Offgas contains more NO than N2O X content, preferably NO X The content is at least 2 times, more preferably at least 3 times, even more preferably at least 4 times, most preferably at least 7 times, especially at least 10 times higher than the NO content, preferably at least 2 times, more preferably at least 3 times, even more preferably at least 4 times, most preferably at least 7 times, especially at least 10 times higher than the NO content. X :N2O molar ratio is greater than 10:1, more preferably at least 20:1, even more preferably at least 30:1, most preferably at least 40:1, especially at least 50:1.

[0480] Sentence 19: The method of any of the preceding sentences, wherein the off-gas has a NO content that is greater than the NO content, preferably the NO content is at least 2 times, more preferably at least 3 times, even more preferably at least 4 times, most preferably at least 7 times, and especially at least 10 times higher than the NO content.

[0481] Sentence 20: A method according to any of the preceding sentences, wherein the off-gas has a NO2 content that is greater than the N2O content, preferably the NO2 content being at least 2 times, more preferably at least 3 times, even more preferably at least 4 times, most preferably at least 7 times, especially at least 10 times higher than the N2O content.

[0482] Sentence 21: No off-gassing XThe NO content is preferably greater than the NO content. X The method according to any of the preceding sentences, wherein the amount of the compound is at least 2 times, more preferably at least 3 times, even more preferably at least 4 times, most preferably at least 7 times, especially at least 10 times higher than the amount of the compound.

[0483] Sentence 22: The method of any of the preceding sentences, wherein the off-gas has an NO content that is greater than the NO content, preferably the NO content is at least 2 times, more preferably at least 3 times, even more preferably at least 4 times, most preferably at least 7 times, especially at least 10 times higher than the NO content.

[0484] Sentence 23: The method of any of the preceding sentences, wherein the off-gas has an N2O content that is greater than the NO2 content, preferably the N2O content is at least 2 times, more preferably at least 3 times, even more preferably at least 4 times, most preferably at least 7 times, and especially at least 10 times higher than the NO2 content.

[0485] Sentence 24: The off-gas contains at least 10 ppmv, preferably at least 20 ppmv, more preferably at least 30 ppmv, even more preferably at least 40 ppmv, especially at least 50 ppmv NO X A method according to any of the preceding sentences having the content.

[0486] Sentence 25: The off-gas contains at least 75 ppmv, preferably at least 100 ppmv, more preferably at least 150 ppmv, even more preferably at least 200 ppmv, especially at least 250 ppmv NO X A method according to any of the preceding sentences having the content.

[0487] Sentence 26: The off-gas contains at least 500 ppmv, preferably at least 1000 ppmv, more preferably at least 2000 ppmv, even more preferably at least 3000 ppmv, especially at least 3500 ppmv NO X A method according to any of the preceding sentences having the content.

[0488] Sentence 27: The method of any of the preceding sentences, wherein the off-gas has an N2O content of at least 10 ppmv, preferably at least 20 ppmv, more preferably at least 30 ppmv, even more preferably at least 40 ppmv, especially at least 50 ppmv.

[0489] Sentence 28: The method of any of the preceding sentences, wherein the off-gas has an N2O content of at least 75 ppmv, preferably at least 100 ppmv, more preferably at least 150 ppmv, even more preferably at least 200 ppmv, especially at least 250 ppmv.

[0490] Sentence 29: The method of any of the preceding sentences, wherein the off-gas has an N2O content of at least 500 ppmv, preferably at least 1000 ppmv, more preferably at least 2000 ppmv, even more preferably at least 3000 ppmv, especially at least 3500 ppmv.

[0491] Sentence 30: The method of any of the preceding sentences, wherein the off-gas has an H2O content of less than 2.0% by volume.

[0492] Sentence 31: The method of any of the preceding sentences, wherein the off-gas has an HO content of more than 4.0 vol.%, preferably at least 5.0 vol.%, more preferably at least 6.0 vol.%, even more preferably at least 7.0 vol.%, most preferably at least 8.0 vol.%, especially at least 9.0 vol.%.

[0493] Sentence 32: The method of any of the preceding sentences, wherein the off-gas has an HO content of at least 10% by volume, preferably at least 12% by volume, more preferably at least 14% by volume, even more preferably at least 16% by volume, most preferably at least 18% by volume, in particular at least 20% by volume.

[0494] Sentence 33: The method of any of the preceding sentences, wherein the off-gas has an HO content within the range of 10±8% by volume, preferably within the range of 10±7% by volume, more preferably within the range of 10±6% by volume, even more preferably within the range of 10±5% by volume, most preferably within the range of 10±4% by volume, and in particular within the range of 10±3% by volume.

[0495] Sentence 34: The method of any of the preceding sentences, wherein the off-gas has an HO content within the range of 15±8% by volume, preferably within the range of 15±7% by volume, more preferably within the range of 15±6% by volume, even more preferably within the range of 15±5% by volume, most preferably within the range of 15±4% by volume, and especially within the range of 15±3% by volume.

[0496] Sentence 35: The method of any of the preceding sentences, wherein the off-gas has an HO content within the range of 20±8% by volume, preferably within the range of 20±7% by volume, more preferably within the range of 20±6% by volume, even more preferably within the range of 20±5% by volume, most preferably within the range of 20±4% by volume, and in particular within the range of 20±3% by volume.

[0497] Sentence 36: The method of any of the preceding sentences, wherein the off-gas has an HO content within the range of 25±8% by volume, preferably within the range of 25±7% by volume, more preferably within the range of 25±6% by volume, even more preferably within the range of 25±5% by volume, most preferably within the range of 25±4% by volume, and especially within the range of 25±3% by volume.

[0498] Sentence 37: The method of any of the preceding sentences, wherein the off-gas has an HO content in the range of 30±8% by volume, preferably in the range of 30±7% by volume, more preferably in the range of 30±6% by volume, even more preferably in the range of 30±5% by volume, most preferably in the range of 30±4% by volume, and especially in the range of 30±3% by volume.

[0499] Sentence 38: The method of any of the preceding sentences, wherein the off-gas has an N2 content of at most 95% by volume, preferably at most 90% by volume, more preferably at most 85% by volume, even more preferably at most 80% by volume, most preferably at most 75% by volume, in particular at most 70% by volume.

[0500] Sentence 39: The method of any of the preceding sentences, wherein the off-gas has an N2 content of at least 40% by volume, preferably at least 50% by volume, more preferably at least 60% by volume, even more preferably at least 70% by volume, most preferably at least 80% by volume, in particular at least 90% by volume.

[0501] Sentence 40: The method of any of the preceding sentences, wherein the off-gas preferably comprises further gaseous components selected from the group consisting of O2, CO, CO2, NH3, CH4 and mixtures thereof.

[0502] Sentence 41: A method according to any of the preceding sentences, wherein the off-gas when leaving the internal combustion engine has a temperature of at least 500°C, more preferably at least 600°C, even more preferably at least 700°C, most preferably at least 800°C, especially at least 900°C.

[0503] Sentence 42: A method according to any of the preceding sentences, wherein the off-gases when leaving the internal combustion engine have a temperature of at most 1100°C, more preferably at most 1000°C, even more preferably at most 900°C, most preferably at most 800°C, in particular at most 700°C.

[0504] Sentence 43: A method according to any of the preceding sentences, wherein the off-gas when leaving the internal combustion engine is at a pressure of up to 1.5 bar, preferably atmospheric pressure.

[0505] Sentence 44: The off-gas as it leaves the internal combustion engine is at least 10%, more preferably at least 20%, even more preferably at least 30%, most preferably at least 40%, especially at least 50% NO X The method of any of the preceding sentences, wherein the oxidation degree is

[0506] Sentence 45: The off-gas when leaving an internal combustion engine is at most 90%, more preferably at most 80%, even more preferably at most 70%, most preferably at most 60%, especially at most 50% NO X The method of any of the preceding sentences, wherein the oxidation degree is

[0507] Sentence 46: A method according to any of the preceding sentences, wherein the off-gas when exiting the internal combustion engine has an O2 content of less than 2.0% by volume.

[0508] Sentence 47: A method according to any of sentences 1 to 28, wherein the off-gas when leaving the internal combustion engine has an O2 content of more than 4.0% by volume.

[0509] Sentence 48: The method of any of the preceding sentences, wherein the off-gas entering the off-gas treatment system is at a temperature of at least 300°C, more preferably at least 350°C, even more preferably at least 400°C, most preferably at least 425°C, especially at least 450°C.

[0510] Sentence 49: A method according to any of the preceding sentences, wherein the off-gas entering the off-gas treatment system is at a temperature of at least 500°C, more preferably at least 550°C, even more preferably at least 600°C, most preferably at least 625°C, especially at least 650°C.

[0511] Sentence 50: A method according to any of the preceding sentences, wherein the off-gas entering the off-gas treatment system is at a temperature of at most 825°C, more preferably at most 800°C, even more preferably at most 775°C, most preferably at most 750°C, especially at most 725°C.

[0512] Sentence 51: A method according to any of the preceding sentences, wherein the off-gas entering the off-gas treatment system is at a temperature of at most 700°C, more preferably at most 650°C, even more preferably at most 600°C, most preferably at most 550°C, especially at most 500°C.

[0513] Sentence 52: A method according to any of the preceding sentences, wherein the off-gas entering the off-gas treatment system is at a temperature that is relatively at least 20°C, preferably at least 40°C, more preferably at least 60°C, even more preferably at least 80°C, most preferably at least 100°C, and especially at least 120°C lower than the temperature of the off-gas exiting the internal combustion engine.

[0514] Sentence 53: A method according to any of the preceding sentences, wherein the off-gas entering the off-gas treatment system has a pressure of at most 1.4 bara, preferably at most 1.3 bara, more preferably at most 1.2 bara.

[0515] Sentence 54: The off-gas entering the off-gas treatment system is at least 10%, more preferably at least 20%, even more preferably at least 30%, most preferably at least 40%, especially at least 50% NO X The method according to any of the preceding sentences, having an oxidation degree of

[0516] Sentence 55: The off-gas entering the off-gas treatment system is at most 90%, more preferably at most 80%, even more preferably at most 70%, most preferably at most 60%, especially at most 50% NO X The method according to any of the preceding sentences, having an oxidation degree of

[0517] Sentence 56: A method according to any of the preceding sentences, wherein the off-gas entering the off-gas treatment system has an O2 content of less than 2.0% by volume.

[0518] Sentence 57: A method according to any of sentences 1 to 36, wherein the off-gas entering the off-gas treatment system has an O2 content greater than 4.0% by volume.

[0519] Sentence 58: A method according to any of the preceding sentences, wherein step (c) comprises (c1) reducing the N2O content in the off-gas by decomposition of N2O via an N2O decomposition catalyst, preferably wherein the N2O decomposition catalyst comprises a zeolitic material, preferably a zeolite comprising a transition metal (including lanthanides), in particular iron, cobalt or copper, more preferably an iron- or copper-containing zeolite, even more preferably an iron- or copper-containing zeolite of the MFI, BEA, FER, MOR, FAU, AEI and / or MEL structural type.

[0520] Sentence 59: A method according to any of the preceding sentences, wherein step (c) comprises (c2) reducing the NO content in the off-gas by chemical reduction of NO with a reducing agent via an NO reduction catalyst, preferably the NO reduction catalyst comprises a zeolitic material, preferably a zeolite comprising a transition metal (including lanthanides), in particular iron, cobalt or copper, more preferably an iron- or copper-containing zeolite, even more preferably an iron- or copper-containing zeolite of the MFI, BEA, FER, MOR, FAU, AEI and / or MEL structural type.

[0521] Sentence 60: A method according to any of the preceding sentences, wherein the reducing agent in step (c2) is selected from NH3, a hydrocarbon, CO, H2 and mixtures thereof, preferably NH3.

[0522] Sentence 61: A method according to any of the preceding sentences, wherein the reducing agent in step (c2) is NH3 used in an amount of 0.5 to 2.0 molar parts, preferably 0.8 to 1.8 molar parts, based on the molar ratio of N2O to be chemically reduced.

[0523] Sentence 62: A method according to any of the preceding sentences, wherein the reducing agent in step (c2) is a hydrocarbon or a mixture of several hydrocarbons, preferably used in an amount of 0.2 to 1.0 molar parts, more preferably 0.2 to 0.7 molar parts, based on the molar ratio of the N2O to be decomposed.

[0524] Sentence 63: NO X The method of any of the preceding sentences, wherein the reduction catalyst comprises a zeolitic material, preferably a zeolite comprising a transition metal (including lanthanides), in particular iron, cobalt or copper, more preferably an iron- or copper-containing zeolite, even more preferably an iron- or copper-containing zeolite of the MFI, BEA, FER, MOR, FAU, AEI and / or MEL structural type.

[0525] Sentence 64: The method of any of the preceding sentences, wherein the reducing agent in step (d) is selected from NH3, a hydrocarbon, CO, H2, and mixtures thereof, and is preferably NH3.

[0526] Sentence 65: The reducing agent in step (d) is NO to be chemically reduced. X. The method of any of the preceding sentences, wherein NH3 is used in an amount of 0.9 to 2.5 molar parts, preferably 1.0 to 1.4 molar parts, preferably 1.0 to 1.2 molar parts, based on the molar ratio of

[0527] Sentence 66: The method of any of the preceding sentences, wherein the reducing agent in step (c2) is the same as the reducing agent in step (d), preferably NH3.

[0528] Sentence 67: The off-gas treatment system comprises a first reaction zone and a second reaction zone, the off-gas passing continuously through the second reaction zone beyond the second reaction zone, a reducing agent being added to the off-gas upstream of the first reaction zone, and NO in the off-gas being reduced in the first reaction zone. X The content is first, NO X NO by reducing agent through reduction catalyst X (step (d)), the N2O content in the off-gas is optionally further reduced by decomposition of N2O via an N2O decomposition catalyst (step (c1)) and / or by chemical reduction of N2O with a reducing agent via an N2O reduction catalyst (step (c2)), and a further reducing agent is optionally added to the off-gas upstream of the second reaction zone, and then in the second reaction zone, the N2O content in the off-gas is reduced by decomposition of N2O via an N2O decomposition catalyst (step (c1)) and / or by chemical reduction of N2O with a reducing agent via an N2O reduction catalyst (step (c2)), and the N2O content in the off-gas is X The content may optionally be NO X NO via reduction catalyst X The method of any of the preceding sentences, wherein the compound is further reduced by chemical reduction of (step (d)).

[0529] Sentence 68: NO in the first reaction zone X Sentence 68. The method of claim 67, wherein the reduction catalyst comprises a conventional SCR catalyst, preferably based on V2O5-WO3- / TiO2.

[0530] Sentence 69: The method of sentence 67 or 68, wherein the temperature of the off-gas entering the first reaction zone is 400°C or less, preferably 350°C or less.

[0531] Sentence 70: NO X69. The method of any of sentences 67 to 69, wherein the reduction catalyst comprises a zeolite material, preferably a zeolite containing a transition metal (including lanthanides), in particular iron, cobalt or copper, more preferably an iron- or copper-containing zeolite, even more preferably an iron- or copper-containing zeolite of the MFI, BEA, FER, MOR, FAU, AEI and / or MEL structural type.

[0532] Sentence 71: The method of any of sentences 73 to 76, wherein the temperature of the off-gas entering the second reaction zone is in the range of 300 to 550°C, preferably 350 to 500°C.

[0533] Sentence 72: NO in the first reaction zone X 72. The method of any of sentences 67 to 71, wherein the reduction catalyst comprises a zeolite material, preferably a zeolite containing a transition metal (including lanthanides), in particular iron, cobalt or copper, more preferably an iron- or copper-containing zeolite, even more preferably an iron- or copper-containing zeolite of the MFI, BEA, FER, MOR, FAU, AEI and / or MEL structural type.

[0534] Sentence 73: The method of any of sentences 67 to 72, wherein the temperature of the off-gas entering the first reaction zone is at least 300°C, more preferably at least 350°C, and even more preferably at least 400°C.

[0535] Sentence 74: The method of any of sentences 67 to 73, wherein the temperature of the off-gas entering the first reaction zone is 600°C or less, more preferably 550°C or less.

[0536] Sentence 75: The N2O decomposition catalyst in the second reaction zone X 75. The method of any of sentences 67 to 74, comprising a sensitive N2O decomposition catalyst.

[0537] Sentence 76: The method of any of sentences 67 to 75, wherein the temperature of the off-gas entering the second reaction zone is at least 300°C, more preferably at least 350°C, and even more preferably at least 400°C.

[0538] Sentence 77: The method of any of sentences 67 to 76, wherein the temperature of the off-gas entering the second reaction zone is 600°C or less, preferably 550°C or less.

[0539] Sentence 78: The off-gas after leaving the first reaction zone and before entering the second reaction zone has a NO concentration in the range of 0 to 200 ppmv, preferably 1 to 200 ppmv. X 78. The method of any of sentences 67 to 77, having a N2O content in the range of 200 to 2000 ppmv.

[0540] Sentence 79: The off-gas after leaving the first reaction zone and before entering the second reaction zone has a NO content of 20 ppmv or less, more preferably 10 ppmv or less, and even more preferably 5 ppmv or less. X 79. The method of any of sentences 67 to 78, having a N2O content in the range of 200 to 2000 ppmv.

[0541] Sentence 80: The off-gas treatment system comprises a first reaction zone and a second reaction zone, the off-gas is continuously passed through the second reaction zone beyond the second reaction zone, a reducing agent is added to the off-gas between the first reaction zone and the second reaction zone, in the first reaction zone, the N2O content in the off-gas is first reduced by decomposition of N2O via an N2O decomposition catalyst (step (c1)), and then in the second reaction zone, the N2O content in the off-gas is reduced by decomposition of N2O via an N2O decomposition catalyst (step (c1)). X The content is NO X NO by reducing agents via reduction catalysts X(step (d)), and the N2O content in the off-gas is optionally further reduced by further decomposition of N2O via an N2O decomposition catalyst (step (c1)) and / or by chemical reduction of N2O with a reducing agent via an N2O reduction catalyst (step (c2)).

[0542] Sentence 81: The method of sentence 80, wherein no reducing agent is added to the off-gas upstream of the first reaction zone.

[0543] Sentence 82: The method of sentence 80 or 81, wherein the NO decomposition catalyst in the first reaction zone comprises a zeolite material, preferably a zeolite containing a transition metal (including a lanthanide), in particular iron, cobalt or copper, more preferably an iron- or copper-containing zeolite, even more preferably an iron- or copper-containing zeolite of the MFI, BEA, FER, MOR, FAU, AEI and / or MEL structural type.

[0544] Sentence 83: The N2O decomposition catalyst in the first reaction zone X 83. The method of any of sentences 80 to 82, comprising a sensitive N2O decomposition catalyst.

[0545] Sentence 84: NO X 84. The method of any of sentences 80 to 83, wherein the reduction catalyst comprises a zeolite material, preferably a zeolite containing a transition metal (including lanthanides), in particular iron, cobalt or copper, more preferably an iron- or copper-containing zeolite, even more preferably an iron- or copper-containing zeolite of the MFI, BEA, FER, MOR, FAU, AEI and / or MEL structural type.

[0546] Sentence 85: A method according to any of sentences 80 to 84, wherein in the first reaction zone and the second reaction zone, the space velocity is set so that the N2O content in the off-gas is reduced by up to 95%, preferably up to 90%, in the first reaction zone, based on the N2O content in the off-gas entering the first reaction zone.

[0547] Sentence 86: The method of any of sentences 80 to 85, wherein in the second reaction zone, the N2O content in the off-gas is further reduced by at least 30%, preferably at least 40%, and more preferably at least 50%, based on the N2O content in the off-gas entering the second reaction zone.

[0548] Sentence 87: A method according to any of sentences 80 to 86, wherein in a second reaction zone, the N2O content in the off-gas is further reduced by chemical reduction of N2O with a reducing agent via an N2O reduction catalyst (step (c2)).

[0549] Sentence 88: The method of any of sentences 67 to 87, wherein the first reaction zone and the second reaction zone are spatially separated.

[0550] Sentence 89: The method of any of sentences 67 to 88, wherein the first reaction zone and the second reaction zone are spatially connected.

[0551] Sentence 90: The method of any of sentences 67 to 89, wherein the first reaction zone and the second reaction zone are disposed within a shared vessel.

[0552] Sentence 91: The method of any of sentences 67 to 90, wherein the off-gas temperature in the first reaction zone and the second reaction zone is 500°C or less, preferably in the range of 350 to 450°C.

[0553] Sentence 92: The method of any of sentences 67 to 91, wherein the space velocity in the first reaction zone is preferably at least 1.2 times, more preferably at least 1.4 times, even more preferably at least 1.6 times, most preferably at least 1.8 times, and especially at least 2.0 times greater than the space velocity in the second reaction zone.

[0554] Sentence 93: The method of any of sentences 67 to 92, wherein the space velocity in the first reaction zone is preferably at least 1.5 times, more preferably at least 2.0 times, even more preferably at least 3.0 times, most preferably at least 5.0 times, and especially at least 10.0 times less than the space velocity in the second reaction zone.

[0555] Sentence 94: The method of any of sentences 67 to 93, wherein the temperature in the first reaction zone is at least 450°C, more preferably at least 500°C, even more preferably at least 550°C, most preferably at least 600°C, and especially at least 650°C.

[0556] Sentence 95: A method according to any of sentences 67 to 94, wherein the temperature in the second reaction zone is at most 600°C, more preferably at most 550°C, even more preferably at most 500°C, most preferably at most 450°C, especially at most 400°C.

[0557] Sentence 96: The method of any of sentences 67 to 95, wherein the temperature in the first reaction zone is relatively higher than the temperature in the second reaction zone by at least 20°C, more preferably by at least 40°C, even more preferably by at least 60°C, most preferably by at least 80°C, and especially by at least 100°C.

[0558] Sentence 97: The method of any of sentences 67 to 96, wherein the temperature in the first reaction zone is relatively higher than the temperature in the second reaction zone by at least 120°C, more preferably at least 140°C, even more preferably at least 160°C, most preferably at least 180°C, and especially at least 200°C.

[0559] Sentence 98: The off-gas exits the off-gas treatment system and contains a residual NO of at most 20 ppmv, preferably at most 15 ppmv, more preferably at most 10 ppmv, even more preferably at most 7.5 ppmv, most preferably at most 5.0 ppmv, especially at most 2.5 ppmv. XA method according to any of the preceding sentences having the content.

[0560] Sentence 99: The method of any of the preceding sentences, wherein the off-gas exits the off-gas treatment system and has a residual N2O content of at most 20 ppmv, preferably at most 15 ppmv, more preferably at most 10 ppmv, even more preferably at most 7.5 ppmv, and most preferably at most 5.0 ppmv, especially at most 2.5 ppmv.

[0561] Sentence 100: A method according to any of the preceding sentences, wherein the N2O decomposition catalyst is disposed in a radial basket through which the flow passes axially.

[0562] Sentence 101: The method of any of the preceding sentences, wherein the N2O decomposition catalyst is in particulate form and comprises at least 50 particles.

[0563] Sentence 102: The method of any of the preceding sentences, wherein the N2O reduction catalyst is disposed in a radial basket through which the flow passes axially.

[0564] Sentence 103: The method of any of the preceding sentences, wherein the N2O reduction catalyst is in particulate form and comprises at least 50 particles.

[0565] Sentence 104: NO X The method of any of the preceding sentences, wherein the reduction catalyst is disposed in a radial basket through which the flow passes axially.

[0566] Sentence 105: NO X The method of any of the preceding sentences, wherein the reduction catalyst is in particulate form and comprises at least 50 particles.

[0567] Sentence 106: A method according to any of the preceding sentences, wherein at least one parameter characteristic of a current operating state of the internal combustion engine is measured in the internal combustion engine as the first measurement variable.

[0568] Sentence 107: The method of sentence 106, wherein the first measurement variable is selected from the group consisting of combustion temperature, NH3 consumption, rotational speed, and noise emitted by the internal combustion engine.

[0569] Sentence 108: A method as recited in any of the preceding sentences, wherein at least one parameter characteristic of the current state of the off-gas before entering the off-gas treatment system is measured as a second measurement variable before entering the off-gas treatment system.

[0570] Sentence 109: The second measured variable is NO in the off-gas X Content, NO in off-gas X the degree of oxidation of the off-gas, the N2O content in the off-gas, the content of other components in the off-gas, such as H2O, O2, and N2, the off-gas temperature, the off-gas pressure, and the volumetric flow rate of the off-gas.

[0571] Sentence 110: A method as in any of the preceding sentences, wherein at least one parameter characteristic of the current state of the off-gas at the outlet of the off-gas treatment system is measured as a third measurement parameter at the outlet of the off-gas treatment system.

[0572] Sentence 111: The third measured variable is NO in the off-gas X Content, NO in off-gas X the degree of oxidation of the off-gas, the N2O content in the off-gas, the content of other components in the off-gas, such as H2O, O2, and N2, the off-gas temperature, the off-gas pressure, and the volumetric flow rate of the off-gas.

[0573] Sentence 112: A method according to any of the preceding sentences, wherein the off-gas treatment system comprises a first reaction zone and a second reaction zone, the off-gas continuously flows through the second reaction zone, a reducing agent is supplied between the first reaction zone and the second reaction zone, and at least one parameter characteristic of a current state of the off-gas after exiting the first reaction zone and before entering the second reaction zone is measured as the fourth measurement variable.

[0574] Sentence 113: The fourth measured variable is NO in the off-gas X Content, NO in off-gas X the degree of oxidation of the off-gas, the N2O content in the off-gas, the content of other components in the off-gas, such as H2O, O2, and N2, the off-gas temperature, the off-gas pressure, and the volumetric flow rate of the off-gas.

[0575] Sentence 114: A method according to any of sentences 106 to 113, wherein control of the method is based on a first measured variable and / or a second measured variable and / or a third measured variable and / or a fourth measured variable by controlled changes in the manipulated variables.

[0576] Sentence 115: The method of sentence 114, wherein the manipulated variable is the amount of metered reducing agent.

[0577] Sentence 116: An apparatus comprising: (i) an NH3-powered internal combustion engine; and (ii) an off-gas treatment system, the device configured to perform a method according to any of the preceding sentences.

Claims

1. (i) NH ３ an internal combustion engine configured to be powered by combustion of a fuel; and configured to be mounted on a marine vessel to propel said marine vessel; (ii) NH ３ produced by combustion of ２ , H ２ O, NO Ｘ and N ２ NO in O-containing off-gas Ｘ and N ２ an off-gas treatment system configured to reduce the content of O; Equipped with The off-gas treatment system comprises: -N ２ N configured to decompose O ２ N decomposition by O decomposition catalyst and / or reducing agent ２ N configured for chemical reduction of O ２ an O reduction catalyst; -NO by reducing agents Ｘ configured for the chemical reduction of NO Ｘ A reduction catalyst; An apparatus comprising:

2. The off-gas is NH ３ the off-gas treatment system includes: ３ The device of claim 1 configured to reduce content.

3. The off-gas treatment system ２ by NH ３ For the chemical oxidation of ３ O ２ Chemically oxidized to N ２ and H ２ NH configured to give O ３ 3. The apparatus of claim 1 or 2, comprising an oxidation catalyst.

4. The N ２ O decomposition catalyst and / or the N ２ O reduction catalyst and / or the NO Ｘ Reduction catalyst and / or NH ３ 4. The apparatus of any one of claims 1 to 3, wherein the oxidation catalysts independently comprise zeolitic materials, preferably zeolites containing a transition metal (including lanthanides), in particular iron, cobalt or copper, more preferably iron- or copper-containing zeolites, even more preferably iron- or copper-containing zeolites of the MFI, BEA, FER, MOR, FAU, AEI and / or MEL structural types.

5. Said NH ３ 5. An apparatus according to claim 3 or 4, wherein the oxidation catalyst is an iron- or copper-containing zeolite, preferably an iron- or copper-containing zeolite of the MFI, BEA, FER, MOR, FAU, AEI and / or MEL structural type.

6. In addition to the iron- or copper-containing zeolite, further NH ３ 6. The device of claim 5, which does not include an oxidation catalyst.

7. Said NH ３ 7. Apparatus according to claim 5 or 6, wherein the oxidation catalyst is an iron-containing zeolite catalyst having a molar ratio of iron to zeolite aluminium n(Fe) / n(Al) of from less than 0.50 to more than 0.05, preferably from less than 0.40 to more than 0.05, more preferably from less than 0.25 to more than 0.05, and even more preferably from less than 0.15 to more than 0.

05.

8. Said NH ３ 8. Apparatus according to any one of claims 5 to 7, wherein the oxidation catalyst is a copper-containing zeolite catalyst having a molar ratio of copper to zeolite aluminium n(Cu) / n(Al) of from less than 1.00 to more than 0.10, preferably from less than 0.80 to more than 0.10, more preferably from less than 0.50 to more than 0.10, and even more preferably from less than 0.30 to more than 0.

10.

9. Said NH ３ The oxidation catalyst is O ２ By NH ３ Selectively oxidize to N ２ and H ２ 0 and introduced as a particle bed, the particles having an equivalent diameter, defined as the diameter of a spherical particle of equivalent volume, of 3.5 to 5.5 mm, and the ratio of the geometrically detectable outer surface area of ​​the particles to the volume of the particle bed is 10,000±500 h －１ At a space velocity based on standard conditions (0°C; 1.01325 bara), 500±50 ppmv of NH ３ , 2.5±0.1 vol% O ２、 and 0.30±0.05% by volume of H ２ The axial flow is contacted with a volumetric flow rate of a gas mixture consisting of O in an amount of 8.0±0.5 ml in an isothermal tubular reactor having an inner diameter of 20±3 mm. ２ / m ３ 1500m from ２ / m ３ and a total pressure of 6±0.5 bara and a temperature of 380°C±5K provides a NH ３ 9. The apparatus of claim 3, wherein the conversion is

10. The N ２ O decomposition catalyst and / or the N ２ O reduction catalyst and / or the NO Ｘ Reduction catalyst and / or the NH ３ 10. The device according to claim 1, wherein the oxidation catalyst has a free-standing honeycomb monolithic structure.

11. The N ２ O decomposition catalyst and / or the N ２ O reduction catalyst and / or the NO Ｘ Reduction catalyst and / or the NH ３ 11. An apparatus according to any one of claims 1 to 10, wherein the oxidation catalyst is independently in the form of pellets, preferably in the form of extruded pellets.

12. The N ２ O decomposition catalyst and the N ２ 12. The apparatus of claim 1, wherein the O reduction catalysts are formed from the same material.

13. The N ２ O decomposition catalyst and the NO Ｘ 13. The device of claim 1, wherein the reduction catalysts are formed from the same material.

14. The N ２ O reduction catalyst and the NO Ｘ 14. The device of any one of claims 1 to 13, wherein the reduction catalysts are formed from the same material.

15. The N ２ O decomposition catalyst, ２ O reduction catalyst, and the NO Ｘ 15. The device of any one of claims 1 to 14, wherein the reduction catalysts are formed from the same material.

16. Said NH ３ The oxidation catalyst and the N ２ 16. The apparatus of claim 3, wherein the O decomposition catalysts are formed from the same material.

17. Said NH ３ The oxidation catalyst and the N ２ 17. The apparatus of any one of claims 3 to 16, wherein the O reduction catalysts are formed from the same material.

18. Said NH ３ Oxidation catalyst and the NO Ｘ 18. The apparatus of any one of claims 3 to 17, wherein the reduction catalysts are formed from the same material.

19. Said NH ３ Oxidation catalyst, the NO Ｘ A reduction catalyst, and the N ２ 19. The apparatus of any one of claims 3 to 18, wherein the O decomposition catalysts are formed from the same material.

20. The N ２ O decomposition catalyst and / or N ２ O reduction catalyst and the NO Ｘ In addition to the reduction catalyst, NH ３ 20. The apparatus of any one of claims 1 to 19, comprising an oxidation catalyst.

21. Said NH ３ 21. The apparatus of claim 20, wherein the oxidation catalyst is selected from precious metal catalysts, said precious metals preferably being selected from the platinum group of metals.

22. Said NH ３ The oxidation catalyst is platinum group metal-free, preferably noble metal-free, preferably NH ３ 22. An apparatus according to claim 20 or 21, wherein the catalyst is an oxidation-active iron-containing or copper-containing zeolite catalyst.

23. Said NH ３ The oxidation catalyst is - Cobalt catalyst, especially Co ３ O ４ Co, where M is preferably selected from Zn, Cu, Fe, Mn and V; ３ O ４ Derived mixed oxide (Co ３－ｙ M ｙ O ４ ); cobalt-containing zeolites preferably of MFI, BEA, FER, MOR, FAU, CHA or AFI structural type, Manganese catalysts, especially MnO with x=1-2 Ｘ MnO, where M is preferably selected from Zn, Cu, Fe and Mn; Ｘ Derived mixed oxide (Mn ｘ－ｙ M ｙ O ｘ ); manganese-containing zeolites preferably of the MFI, BEA, FER, MOR, FAU, CHA or AFI structural type, copper catalysts, in particular CuO with x=0.5 to 1 Ｘ CuO, where M is preferably selected from Zn, Co, Fe and Mn; Ｘ Derived mixed oxide (Cu ｘ－ｙ M ｙ O ｘ ); copper-containing zeolites preferably of the MFI, BEA, FER, MOR, FAU, CHA, AFI structural type; - preferably Al, especially in supported form ２ O ３ , TiO ２ or SiO ２ a silver catalyst supported on 23. The device according to any one of claims 20 to 22, selected from:

24. NH ３ 24. The apparatus of claim 1, wherein the combustion of is not catalytic.

25. 25. Apparatus according to any one of the preceding claims, wherein the internal combustion engine constitutes a reciprocating piston engine, preferably a reciprocating piston engine with compression ignition.

26. 26. Apparatus according to any one of the preceding claims, wherein the internal combustion engine constitutes a reciprocating piston engine, preferably a reciprocating piston engine with a turbocharger comprising a turbo compressor and an off-gas turbine.

27. 27. The apparatus of claim 26, wherein all components of the off-gas treatment system are located upstream of the off-gas turbine in a flow direction of the off-gas.

28. 28. Apparatus according to any one of claims 1 to 27, wherein the internal combustion engine is an ammonia dual fuel engine.

29. 29. Apparatus according to any one of claims 1 to 28, wherein the internal combustion engine is equipped with a system for exhaust gas recirculation.

30. The internal combustion engine is configured to burn NH3 in a mixture with further combustible gases. ３ and preferably the further combustible gas is (i)H ２ 、 (ii) fossil fuels, preferably hydrocarbons and hydrocarbon mixtures, more preferably methane, ethane, propane, butane, natural gas, gasoline and / or diesel; (iii) alcohol, preferably methanol and / or ethanol; and mixtures thereof, 30. The device of any one of claims 1 to 29, selected from:

31. The internal combustion engine is ２ and / or NH in a mixture with natural gas ３ Combustion of H ２ In a mixture with NH ３ 31. The apparatus of claim 1, configured to combust

32. Said NH ３ H in said mixture with ２ 32. The device according to claim 30 or 31, wherein the proportion of is at most 80 mol%, more preferably at most 70 mol%, even more preferably at most 60 mol%, most preferably at most 50 mol%, in particular at most 40 mol%.

33. Said NH ３ H in said mixture with ２ is at least 10 mol%, more preferably at least 20 mol%, even more preferably at least 30 mol%, most preferably at least 40 mol%, in particular at least 50 mol%.

34. H in the mixture ２ :NH ３ 34. The apparatus according to any one of claims 30 to 33, wherein the molar ratio of is in the range from 45:55 to 90:10, preferably from 50:50 to 85:15, more preferably from 55:45 to 80:20, even more preferably from 60:40 to 75:25, and most preferably from 65:35 to 70:

30.

35. NH ３ 35. Apparatus according to any one of claims 30 to 34, comprising a cracking device for thermal and / or catalytic cracking of

36. The cracking device and the internal combustion engine are ３ The combustion of NH ３ 36. The apparatus of claim 35, configured to provide energy for cracking of

37. The cracking device and the internal combustion engine are ３ The cracking of NH ３ 37. Apparatus according to claim 35 or 36, configured to provide further combustible gas for combustion in mixture with

38. The cracking device is ３ In the flow direction of NH ３ Downstream of the reservoir and the NH of the internal combustion engine ３ 38. Apparatus according to any one of claims 35 to 37, arranged upstream of the jet.

39. NH ３ is burned alone, and therefore NH ３ 30. An apparatus according to any one of claims 1 to 29, wherein is the only combustible gas combusted.

40. The internal combustion engine derives at least 90%, preferably at least 95%, more preferably at least 96%, even more preferably at least 97%, most preferably at least 98%, especially at least 99% of the total energy obtained from NH ３ 40. The apparatus of any one of claims 1 to 39, configured so that combustion of

41. 41. Apparatus according to any one of claims 1 to 40, wherein the internal combustion engine is configured to have an air ratio λ during combustion in the range of 0.9 to 1.7, preferably 1.05 to 1.7, more preferably 1.0 to 1.6, even more preferably 1.1 to 1.5, and most preferably 1.2 to 1.

4.

42. 42. Apparatus according to any one of claims 1 to 41, wherein the internal combustion engine is configured such that the air ratio λ during combustion is at least 1.05, preferably at least 1.10, more preferably at least 1.15, even more preferably at least 1.20, most preferably at least 1.25, in particular at least 1.

20.

43. 43. Apparatus according to any one of claims 1 to 42, wherein the internal combustion engine is configured such that the air ratio λ during combustion is at least 1.25, preferably at least 1.30, more preferably at least 1.35, even more preferably at least 1.40, most preferably at least 1.45, in particular at least 1.

50.

44. In the internal combustion engine, the off-gas is preferably O ２ , CO, CO ２ , N.H. ３ , C.H. ４ 44. The apparatus of any one of claims 1 to 43, configured to contain a further gaseous component selected from the group consisting of: and mixtures thereof.

45. The internal combustion engine is configured such that the off-gas is NH ３ 45. The apparatus of any one of claims 1 to 44, configured to include:

46. The internal combustion engine is configured such that the off-gas has an NH ３ : NO Ｘ 46. ​​The apparatus of claim 1, configured to have a molar ratio of:

47. The internal combustion engine is configured such that the off-gas has an NH ３ : NO Ｘ 47. The apparatus of any one of claims 1 to 46, configured to have a molar ratio of:

48. The internal combustion engine is configured such that the off-gas is ２ NO content greater than O content Ｘ Preferably, the NO Ｘ The content is the above-mentioned N ２ O content is at least 2 times, more preferably at least 3 times, even more preferably at least 4 times, most preferably at least 7 times, especially at least 10 times higher, preferably at least 2 times, more preferably at least 3 times, even more preferably at least 4 times, most preferably at least 7 times, especially at least 10 times higher than NO content. Ｘ :N ２ 48. Apparatus according to any one of claims 1 to 47, wherein the molar ratio of O to HCl is greater than 10:1, preferably at least 20:1, more preferably at least 30:1, most preferably at least 40:1, especially at least 50:

1.

49. The internal combustion engine is configured such that the off-gas is ２ The NO content is preferably greater than the N content. ２ 49. An apparatus according to any one of claims 1 to 48, wherein the O content is at least 2 times higher, more preferably at least 3 times higher, even more preferably at least 4 times higher, most preferably at least 7 times higher, especially at least 10 times higher.

50. The internal combustion engine is configured such that the off-gas is ２ NO content greater than O content ２ Preferably, the NO ２ The content is the above-mentioned N ２ 50. An apparatus according to any one of claims 1 to 49, wherein the O content is at least 2 times higher, more preferably at least 3 times higher, even more preferably at least 4 times higher, most preferably at least 7 times higher, especially at least 10 times higher.

51. The internal combustion engine is configured such that the off-gas contains at least 10 ppmv, preferably at least 20 ppmv, more preferably at least 30 ppmv, even more preferably at least 40 ppmv, especially at least 50 ppmv NO Ｘ 51. The device of any one of claims 1 to 50, configured to have the following content:

52. The internal combustion engine is configured such that the off-gas contains at least 75 ppmv, preferably at least 100 ppmv, more preferably at least 150 ppmv, even more preferably at least 200 ppmv, especially at least 250 ppmv of NO Ｘ 52. The device of any one of claims 1 to 51, configured to have the following content:

53. The internal combustion engine is configured such that the off-gas contains at least 500 ppmv, preferably at least 1000 ppmv, more preferably at least 2000 ppmv, even more preferably at least 3000 ppmv, especially at least 3500 ppmv of NO Ｘ 53. The device of any one of claims 1 to 52, configured to have the following content:

54. The internal combustion engine is configured such that the off-gas contains at least 10 ppmv, preferably at least 20 ppmv, more preferably at least 30 ppmv, even more preferably at least 40 ppmv, especially at least 50 ppmv of N ２ 54. The device of any one of claims 1 to 53, configured to have an O content.

55. The internal combustion engine is configured such that the off-gas contains at least 75 ppmv, preferably at least 100 ppmv, more preferably at least 150 ppmv, even more preferably at least 200 ppmv, especially at least 250 ppmv of N ２ 55. The device of any one of claims 1 to 54, configured to have an O content.

56. The internal combustion engine is configured such that the off-gas contains at most 35,000 ppmv, preferably at most 30,000 ppmv, more preferably at most 25,000 ppmv, even more preferably at most 20,000 ppmv, most preferably at most 15,000 ppmv, especially at most 10,000 ppmv NH ３ 56. The device of any one of claims 1 to 55, configured to have the following content:

57. The internal combustion engine is configured such that the off-gas contains at most 9000 ppmv, preferably at most 8000 ppmv, more preferably at most 7000 ppmv, even more preferably at most 6000 ppmv, most preferably at most 5000 ppmv, especially at most 4000 ppmv NH ３ 57. The device of any one of claims 1 to 56, configured to have the following content:

58. The internal combustion engine is configured such that the off-gas contains at most 3500 ppmv, preferably at most 3000 ppmv, more preferably at most 2500 ppmv, even more preferably at most 2000 ppmv, most preferably at most 1500 ppmv, especially at most 1000 ppmv NH ３ 58. The device of any one of claims 1 to 57, configured to have the following content:

59. The apparatus is configured such that the off-gas entering the off-gas treatment system is filtered to remove at least 10%, more preferably at least 20%, even more preferably at least 30%, most preferably at least 40%, especially at least 50% NO Ｘ 59. The apparatus of any one of claims 1 to 58, configured to have an oxidation degree of

60. The apparatus may be configured to reduce the amount of NOx entering the off-gas treatment system to at most 90%, more preferably at most 80%, even more preferably at most 70%, most preferably at most 60%, especially at most 50%, preferably at most 15%, more preferably at most 12.5%, even more preferably at most 10%, most preferably at most 7.5%, especially at most 5.0%. Ｘ 60. The apparatus of any one of claims 1 to 59, configured to have an oxidation degree of

61. The apparatus is configured to: ２ 61. The device of any one of claims 1 to 60, configured to have the following content:

62. The apparatus is adapted to ensure that the off-gas entering the off-gas treatment system contains at least 3.0 vol.%, preferably at least 3.1 vol.%, more preferably at least 3.2 vol.%, even more preferably at least 3.3 vol.%, most preferably at least 3.4 vol.%, especially at least 3.5 vol.% O ２ 62. The device of any one of claims 1 to 61 configured to have the following content:

63. The apparatus is configured to: ２ 63. The device of any one of claims 1 to 62, configured to have the following content:

64. N ２ N via O decomposition catalyst ２ The N in the off-gas due to the decomposition of O ２ The reduction of the O content is preferably ２ 64. The apparatus of any one of claims 1 to 63, comprising: the O decomposition catalyst comprising a zeolitic material, preferably a zeolite comprising a transition metal (including lanthanides), in particular iron, cobalt or copper, more preferably an iron- or copper-containing zeolite, even more preferably an iron- or copper-containing zeolite of the MFI, BEA, FER, MOR, FAU, AEI and / or MEL structural type.

65. N ２ N using a reducing agent via an O reduction catalyst ２ The N in the off-gas by chemical reduction of O ２ The reduction of the O content is preferably ２ 65. The apparatus of any one of claims 1 to 64, comprising: the O reduction catalyst comprising a zeolitic material, preferably a zeolite comprising a transition metal (including lanthanides), in particular iron, cobalt or copper, more preferably an iron- or copper-containing zeolite, even more preferably an iron- or copper-containing zeolite of the MFI, BEA, FER, MOR, FAU, AEI and / or MEL structural type.

66. N ２ The reducing agent for O is NH ３ , hydrocarbons, CO, H ２ and mixtures thereof, preferably NH ３ 66. The device of any one of claims 1 to 65, wherein:

67. N ２ The reducing agent for O is N to be chemically reduced. ２ NH used in an amount of 0.5 to 2.0 molar parts, preferably 0.8 to 1.8 molar parts, based on the molar ratio of O ３ 67. The apparatus of any one of claims 1 to 66, wherein:

68. N ２ The reducing agent for O is N to be decomposed. ２ 68. The apparatus according to any one of claims 1 to 67, wherein the hydrocarbon or mixture of several hydrocarbons is preferably used in an amount of 0.2 to 1.0 molar part, more preferably 0.2 to 0.7 molar part, based on the molar ratio of O.

69. The above NO Ｘ 69. An apparatus according to any one of claims 1 to 68, wherein the reduction catalyst comprises a zeolitic material, preferably a zeolite comprising a transition metal (including lanthanides), in particular iron, cobalt or copper, more preferably an iron- or copper-containing zeolite, even more preferably an iron- or copper-containing zeolite of the MFI, BEA, FER, MOR, FAU, AEI and / or MEL structural type.

70. NO Ｘ The reducing agent for ３ , hydrocarbons, CO, H ２ and mixtures thereof, preferably NH ３ 70. The apparatus of any one of claims 1 to 69, wherein:

71. NO Ｘ The reducing agent for NO to be chemically reduced Ｘ NH used in an amount of 0.9 to 2.5 molar parts, preferably 1.0 to 1.4 molar parts, more preferably 1.0 to 1.2 molar parts based on the molar ratio of ３ 71. The apparatus of any one of claims 1 to 70, wherein:

72. N ２ The reducing agent for O is NO Ｘ is the same as the reducing agent for ３ 72. The device of any one of claims 1 to 71, wherein:

73. The off-gas treatment system comprises: -N ２ O decomposition catalyst and / or N ２ as an O reduction catalyst, and -NH ３ as reduction catalysts, zeolitic materials, preferably zeolites containing transition metals (including lanthanides), in particular iron, cobalt or copper, more preferably iron- or copper-containing zeolites, even more preferably iron- or copper-containing zeolites of the MFI, BEA, FER, MOR, FAU, AEI and / or MEL structural type; a single reaction zone comprising N to the off-gas ２ O and / or NO Ｘ a device for metered addition of a reducing agent for the off-gas is arranged upstream of the single reaction zone in the flow direction of the off-gas, 73. Apparatus according to any one of claims 1 to 72.

74. The device for metered addition of reducing agents is ３ 74. The apparatus of claim 73, which is a device for the metered addition of

75. N to the off-gas ２ O and / or NO Ｘ 75. Apparatus according to claim 73 or 74, wherein a further device for the metered addition of a reducing agent for is arranged upstream of the single reaction zone in the flow direction of the off-gas.

76. 76. Apparatus according to claim 75, wherein the further device for the metering addition of a reducing agent is an apparatus for the metering addition of natural gas.

77. NH ３ NH with an oxidation catalyst, preferably free of platinum group metals, preferably free of noble metals ３ An oxidation catalyst, more preferably NH ３ Oxidation-active iron or copper-containing zeolite catalysts, even more preferably layered NH ３ Oxidation catalysts, most preferably NH as defined in any one of claims 3 to 13 ３ 77. The apparatus of any one of claims 73 to 76, wherein a further reaction zone comprising an oxidation catalyst is located upstream of the single reaction zone in the flow direction of the off-gas.

78. The device is preferably free of platinum group metals, more preferably free of precious metals. ３ An oxidation catalyst, more preferably NH ３ 78. The apparatus of claim 77 having a controllable bypass around the oxidation-active iron or copper-containing zeolite catalyst.

79. NH ３ , NO Ｘ or N ２ O, preferably NH ３ and NO Ｘ and N ２ 80. The apparatus of claim 78, wherein a device for measuring the concentration of O in the off-gas is located upstream of the single reaction zone in a flow direction of the off-gas, and wherein the opening of the bypass is controllable by open-loop control or closed-loop control.

80. NH ３ NH containing an oxidation catalyst, preferably free of platinum group metals, more preferably free of noble metals ３ An oxidation catalyst, more preferably NH ３ Oxidation-active iron or copper-containing zeolite catalysts, even more preferably layered NH ３ Oxidation catalyst, most preferably NH according to any one of claims 3 to 13 ３ 80. The apparatus of any one of claims 73 to 79, wherein a further reaction zone comprising an oxidation catalyst is located downstream of the single reaction zone in the flow direction of the off-gas.

81. Preferably, the NH ３ An oxidation catalyst, more preferably NH ３ 81. The apparatus of claim 80, wherein an oxidation-active iron or copper-containing zeolite catalyst is disposed upstream of an off-gas turbine in a flow direction of the off-gas.

82. Preferably, the NH ３ An oxidation catalyst, more preferably NH ３ 81. The apparatus of claim 80, wherein an oxidation-active iron or copper-containing zeolite catalyst is disposed downstream of the off-gas turbine in a flow direction of the off-gas.

83. 83. The apparatus of claim 81 or 82, wherein the single reaction zone is located upstream of the off-gas turbine in a flow direction of the off-gas.

84. the off-gas treatment system comprises a first reaction zone and a second reaction zone disposed downstream in a flow direction of the off-gas, the first reaction zone and the second reaction zone being configured so that the off-gas passes through them successively; The first reaction zone and the second reaction zone each independently contain N ２ O decomposition catalyst and / or N ２ O as a reduction catalyst and / or NH ３ as reduction catalysts, zeolitic materials, preferably zeolites containing transition metals (including lanthanides), in particular iron, cobalt or copper, more preferably iron- or copper-containing zeolites, even more preferably iron- or copper-containing zeolites of the MFI, BEA, FER, MOR, FAU, AEI and / or MEL structural type, N to the off-gas ２ O and / or NO Ｘ a device for metered addition of a reducing agent for the off-gas is located downstream of the first reaction zone and upstream of the second reaction zone in the flow direction of the off-gas, 73. Apparatus according to any one of claims 1 to 72.

85. The device for metering the reducing agent is ３ 85. The apparatus of claim 84, which is a device for the metered addition of

86. N to the off-gas ２ O and / or NO Ｘ 86. The apparatus according to claim 84 or 85, wherein a further device for the metered addition of a reducing agent for is arranged upstream of the single reaction zone in the flow direction of the off-gas.

87. 87. Apparatus according to claim 86, wherein the further device for the metering of a reducing agent is a device for the metering of natural gas.

88. N to the off-gas ２ O and / or NO Ｘ 88. The apparatus of any one of claims 84 to 87, wherein an additional device for metered addition of a reducing agent for is arranged upstream of the first reaction zone in the flow direction of the off-gas.

89. The additional device for the metered addition of reducing agents is NH ３ 89. The apparatus of claim 88, which is a device for the metered addition of

90. - said first reaction zone comprises a copper-containing zeolite, preferably a copper-containing zeolite of MFI, BEA, FER, MOR, FAU, AEI and / or MEL structural type; and said second reaction zone comprises an iron-containing zeolite, preferably an iron-containing zeolite of MFI, BEA, FER, MOR, FAU, AEI and / or MEL structural type; 90. Apparatus according to any one of claims 84 to 89.

91. NH ３ , NO Ｘ or N ２ O, preferably NH ３ and NO Ｘ and N ２ 91. The apparatus of any one of claims 84 to 90, wherein a device for measuring the concentration of O in the off-gas is positioned downstream of the first reaction zone and upstream of the second reaction zone in a flow direction of the off-gas.

92. At least one device selected from the device for metering of a reducing agent, any further device for metering of a reducing agent, and any additional device for metering of a reducing agent is selected from the group consisting of NH ３ , NO Ｘ or N ２ O, preferably NH ３ and NO Ｘ and N ２ 92. Apparatus according to claim 91, controllable by open-loop or closed-loop control, preferably by feed-forward control, in response to a measured concentration in the off-gas of O.

93. NH ３ , NO Ｘ or N ２ O, preferably NH ３ and NO Ｘ and N ２ 93. The apparatus of any one of claims 84 to 92, wherein a device for measuring the concentration of O in the off-gas is positioned upstream of the first reaction zone in a flow direction of the off-gas.

94. At least one device selected from the device for metering of a reducing agent, any further device for metering of a reducing agent, and any additional device for metering of a reducing agent is selected from the group consisting of NH ３ , NO Ｘ or N ２ O, preferably NH ３ and NO Ｘ and N ２ 94. Apparatus according to claim 93, controllable by open-loop or closed-loop control, preferably by feed-forward control, in response to a measured concentration in the off-gas of O.

95. NH ３ NH containing an oxidation catalyst, preferably free of platinum group metals, more preferably free of noble metals ３ An oxidation catalyst, more preferably NH ３ Oxidation-active iron or copper-containing zeolite catalysts, even more preferably layered NH ３ An oxidation catalyst, most preferably NH according to any one of claims 3 to 9 ３ 95. The apparatus of any one of claims 84 to 94, wherein a further reaction zone comprising an oxidation catalyst is located downstream of the first reaction zone and upstream of the second reaction zone in the flow direction of the off-gas.

96. NH ３ NH containing an oxidation catalyst, preferably free of platinum group metals, more preferably free of noble metals ３ An oxidation catalyst, more preferably NH ３ Oxidation-active iron or copper-containing zeolite catalysts, even more preferably layered NH ３ An oxidation catalyst, most preferably NH according to any one of claims 3 to 9 ３ 96. The apparatus of any one of claims 84 to 95, wherein a further reaction zone comprising an oxidation catalyst is arranged downstream of the first reaction zone and upstream of the second reaction zone in the flow direction of the off-gas and upstream of the device for metering addition of a reducing agent and any further device for metering addition of a reducing agent.

97. NH ３ NH containing an oxidation catalyst, preferably free of platinum group metals, more preferably free of noble metals ３ An oxidation catalyst, more preferably NH ３ Oxidation-active iron or copper-containing zeolite catalysts, even more preferably layered NH ３ An oxidation catalyst, most preferably NH according to any one of claims 3 to 9 ３ 97. The apparatus of any one of claims 84 to 96, wherein a further reaction zone comprising an oxidation catalyst is located downstream of the second reaction zone in the flow direction of the off-gas.

98. The device is preferably free of platinum group metals, more preferably free of precious metals. ３ An oxidation catalyst, more preferably NH ３ 98. An apparatus according to any one of claims 95 to 97, having a controllable bypass around the oxidation-active iron or copper-containing zeolite catalyst.

99. NH ３ , NO Ｘ or N ２ O, preferably NH ３ and NO Ｘ and N ２ 99. The apparatus of claim 98, wherein a device for measuring the concentration of O in the off-gas is positioned upstream of the first reaction zone or upstream of the second reaction zone in a flow direction of the off-gas, and wherein the opening of the bypass is controllable by open-loop control or closed-loop control.

100. Preferably, the NH ３ An oxidation catalyst, more preferably NH ３ 100. The apparatus of any one of claims 95 to 99, wherein an oxidation-active iron or copper-containing zeolite catalyst is positioned upstream of an off-gas turbine in a flow direction of the off-gas.

101. Preferably, the NH ３ An oxidation catalyst, more preferably NH ３ 100. An apparatus according to any one of claims 95 to 99, wherein the oxidation-active iron or copper-containing zeolite catalyst is positioned downstream of the off-gas turbine in the flow direction of the off-gas.

102. 102. The apparatus of claim 100 or 101, wherein the first reaction zone is located upstream of the off-gas turbine in a flow direction of the off-gas.

103. 103. The apparatus of any one of claims 100 to 102, wherein the second reaction zone is located upstream of the off-gas turbine in a flow direction of the off-gas.

104. The off-gas treatment system includes a diesel oxidation catalyst, a lean NO Ｘ Trap catalyst, NO Ｘ 104. The apparatus of any one of claims 1 to 103, comprising at least one additional component selected from an absorbent component, a non-catalytic particulate filter, and a catalytic particulate filter, preferably all additional components being positioned upstream of the second reaction zone in the flow direction of the off-gas.

105. The N ２ O decomposition catalyst and / or the N ２ O reduction catalyst and the NO Ｘ Reduction catalyst and optional NH ３ 105. A method according to any one of the preceding claims, wherein the oxidation catalyst is in the form of independent, monolithic catalytic elements permeated with parallel channels, preferably in the form of a monolithic honeycomb body.

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