Method for the targeted aging of a catalyst using a test bench

Abstract

The invention relates to a method for the targeted aging of a catalyst (2) by means of a test rig (1) comprising the catalyst (2) and an internal combustion engine (3), in which the internal combustion engine (3) has at least two combustion chambers (5, 6), namely a first combustion chamber (5) and a second combustion chamber (6). An aging phase is carried out in which the internal combustion engine (3) is operated under fire, whereby the internal combustion engine (3) provides an overall lean exhaust gas, which forms an exhaust gas mass flow that is passed through the catalyst (2).During the first part of the aging phase, the internal combustion engine (3) is operated by firing the first combustion chamber (5) and the second combustion chamber (6), whereby the internal combustion engine (3) provides the overall lean exhaust gas, which forms the exhaust gas mass flow that has a base temperature of less than 900 degrees Celsius during the first part and is passed through the catalyst (2).

Description

[0001] The invention relates to a method for the targeted aging of a catalyst using a test bench.

[0002] CN 1 01 790 624 B discloses a method for verifying the aging state of a catalyst on board a vehicle. DE 10 2018 126 767 B4 discloses a method for monitoring the effectiveness of a three-way catalyst. DE 10 2018 130 990 A1 discloses a method for aging a component of an exhaust aftertreatment system. WO 2010 / 022 747 A1 discloses a method for generating aging gas for aging exhaust aftertreatment components. Furthermore, EP 1 521 903 B1 discloses a method for artificially aging a catalyst device used on a catalyst test bench. KR 10 2005 0 033 718 A also discloses a method for aging a catalyst. DE 10 2022 107 631 A1 discloses a method and systems for introducing secondary air into an internal combustion engine system.DE 10 2017 206 162 A1 discloses a device for controlling a diesel engine and a storage catalyst downstream of the diesel engine. DE 102 32 120 A1 discloses a method and a device for artificially aging a vehicle catalyst. DE 10 2014 105 128 A1 discloses an engine control unit for catalyst regeneration. DE 103 52 265 A1 discloses a method for aging a catalyst. DE 10 2020 127 125 A1 discloses a method for providing a vehicle catalyst and a test bench for providing a vehicle catalyst.

[0003] The object of the present invention is to provide a method by which a catalyst can be aged in a particularly advantageous and targeted manner using a test rig.

[0004] This problem is solved according to the invention by a method having the features of claim 1. Advantageous embodiments of the invention are the subject of the dependent claims.

[0005] The invention relates to a method for the targeted and artificial aging of a catalyst. The method according to the invention is carried out using a stationary and therefore completely immobile test rig, which is a device distinct from a vehicle. In other words, the aging of the catalyst is specifically induced by the method according to the invention. The feature that the catalyst can be aged in a targeted and artificial manner by the method according to the invention means that the aging of the catalyst achievable or effected by the method is brought about by the test rig and does not result from the operation of a vehicle in which the catalyst is installed.The test rig includes the catalyst and an internal combustion engine, also known as a combustion engine or combustion power unit, which, as will be explained in more detail below, provides exhaust gas during the process. The catalyst is designed as a three-way catalyst. The catalyst is designed to treat the exhaust gas, in particular by catalytically supporting and / or inducing at least one chemical reaction in which at least one chemical compound contained in the exhaust gas, also referred to as a starting compound, or in particular several chemical compounds contained in the exhaust gas, also referred to as starting compounds, is converted into a chemical compound different from the respective starting compound, also referred to as a result compound.The starting compound is or comprises, for example, carbon monoxide (CO) and / or unburned hydrocarbons (HC) and / or nitrogen (NOx). In other words, the catalyst is designed to catalytically support and / or effect chemical reactions by which carbon monoxide (CO) contained in the exhaust gas is converted into carbon dioxide (CO2), unburned hydrocarbons (HC) contained in the exhaust gas are converted into carbon dioxide and water (H2O), and nitrogen oxides contained in the exhaust gas, such as nitric oxide (NO), are converted into nitrogen (N2) and carbon dioxide. The conversion of the respective starting compound into the respective result compound is also referred to as "conversion" or "reaction." Thus, the catalyst is designed for a conversion, that is, for the reaction of at least one starting compound into at least one different result compound.As will be explained in more detail below, the process uses the exhaust gas of the internal combustion engine as an aging gas, with which the catalyst is specifically aged.

[0006] In this process, the internal combustion engine has several, and therefore at least or exactly two, combustion chambers, namely a first combustion chamber and a second combustion chamber. For example, each combustion chamber is partially bounded by a respective cylinder of the internal combustion engine and partially by a respective, translationally movable cylinder on the piston of the internal combustion engine, so that, for example, the internal combustion engine is designed as a reciprocating piston engine.

[0007] In the method according to the invention, an aging phase is carried out at least once. During the aging phase, the internal combustion engine is operated under load, thereby producing an overall lean exhaust gas, which forms an exhaust gas mass flow that is passed through the catalyst during the aging phase. This means that during the aging phase, the exhaust gas mass flow, and thus the overall lean exhaust gas of the internal combustion engine that forms the exhaust gas mass flow, is passed through the catalyst. The fact that the exhaust gas of the internal combustion engine is lean overall, and preferably continuously and thus without interruption, during the aging phase means that the exhaust gas, particularly with regard to its residual oxygen content, has a composition that results from lean operation of the internal combustion engine when considering the engine as a whole.In other words, during the aging phase, the internal combustion engine as a whole, that is, considered holistically, and in particular continuously and without interruption, operates in a lean condition. This means that, when considering the engine holistically, it operates with a lean air-fuel ratio, which is greater than 1. Specifically, during the aging phase, the overall air-fuel ratio with which the internal combustion engine is operated is greater than 1.01.

[0008] The aging phase has at least or exactly two parts: a first part and a second part. During the first part of the aging phase, the internal combustion engine is operated by firing the first combustion chamber and the second combustion chamber, in particular all combustion chambers, of the internal combustion engine. This results in the internal combustion engine as a whole, that is, when considering the engine in its entirety, providing a lean exhaust gas. This exhaust gas mass flow, which during the first part of the aging phase, in particular continuously and / or constantly, has a base temperature of less than 900 degrees Celsius and is passed through the catalysts. The base temperature is also referred to as the "first temperature".It is conceivable that during the first part of the aging phase, the exhaust gas mass flow exhibits a consistently lower base temperature compared to 900 degrees Celsius, and thus remains constant. Furthermore, it is conceivable that during the first part of the aging phase, the base temperature is at least substantially constant.

[0009] The characteristic that the respective combustion chamber is fired, that is, operated in a fired process, means that combustion processes take place in the respective combustion chamber, specifically such that a combustion process occurs within each operating cycle of the internal combustion engine. During this combustion process, a fuel-air mixture, also simply referred to as a mixture, is combusted in the respective combustion chamber, specifically ignited and burned, resulting in the exhaust gas of the internal combustion engine. The respective mixture comprises at least air and, for example, a liquid fuel.

[0010] The second part of the aging phase follows, for example, directly from the first part. The fact that the second part of the aging phase preferably follows directly from the first part means that no other, further part of the aging phase lies between the first and second parts. During the second part of the aging phase, the internal combustion engine is operated with combustion, whereby the first combustion chamber is fired and the second combustion chamber is operated without combustion. In each fired combustion chamber, air and fuel are introduced into the respective combustion chamber.The characteristic that the second combustion chamber is operated without fuel, particularly continuously and thus without interruption, during the second part of the aging phase, means that combustion does not occur in the second combustion chamber during this second part of the aging phase. During this unfired operation of the second combustion chamber, fuel is not introduced into the second combustion chamber.In the unfired operation of the second combustion chamber, only the air is passed through it, specifically pumped through it, with respect to the fuel and air. During the second part of the aging phase, the first combustion chamber provides the exhaust gas resulting from the combustion processes taking place there. During this second part of the aging phase, the second combustion chamber provides the air that is passed through it. Thus, during this second part of the aging phase, the internal combustion engine provides the overall lean exhaust gas, which forms the exhaust mass flow that is passed through the catalytic converter.This means that although during the second part of the aging phase the first combustion chamber is fired and the second combustion chamber is unfired, the exhaust gas of the internal combustion engine as a whole, i.e., when considering the engine as a whole, remains lean. This occurs primarily because, viewed individually, the fired operation of the first combustion chamber compensates for the unfired operation of the second combustion chamber, such that during the second part of the aging phase the exhaust gas of the internal combustion engine as a whole, i.e., when considering the engine as a whole, remains consistently lean.For example, during the second part of the aging phase, the first combustion chamber is operated rich, meaning with a rich air-fuel ratio (lambda), thus at least partially compensating for the excess air resulting from the unfired operation of the second combustion chamber. This unfired operation of the second combustion chamber during the second part of the aging phase, while the first combustion chamber is fired, is also referred to as second combustion chamber silencing or cylinder silencing. Particularly when the respective combustion chamber is partially formed by the aforementioned cylinder, the silencing of the second combustion chamber is also called "cylinder silencing." Thus, during the second part of the aging phase, the second combustion chamber is silenced, specifically cylinder silencing, while the first combustion chamber is fired.This allows, for example, unburned hydrocarbons from the first combustion chamber to enter the exhaust gas of the internal combustion engine and thus the catalytic converter, while oxygen from the second combustion chamber enters the exhaust gas and thus the catalytic converter. This means that, for example, during the second part of the aging phase in the catalytic converter, the unburned hydrocarbons can react with the oxygen in the exhaust gas, oxidizing them with the oxygen contained in the exhaust gas, and thus being burned within the catalytic converter. As a result, during the second part of the aging phase, the catalytic converter experiences at least a temporary peak temperature, and in particular at least once, and especially several times, which is higher than the base temperature.The method according to the invention makes it possible to age the catalyst in a particularly simple and targeted manner, thereby bringing the catalyst into a so-called limiting catalyst state, i.e. converting it into a so-called limiting catalyst.

[0011] The invention is based in particular on the following considerations and insights: the catalyst, or rather its catalytically effective volume for conversion, has an extent, also referred to as "length," which runs along a flow direction in which the exhaust gas mass flow can or does flow through the catalyst, or rather its volume, also referred to as the catalyst volume. The catalyst can thus be divided or subdivided, particularly at least conceptually, into two sub-areas: a first sub-area and a second sub-area, which adjoins the first sub-area in the flow direction in which the exhaust gas mass flow passes through the catalyst.Thus, the second section is arranged downstream of the first section in the direction of exhaust gas mass flow through the catalyst, which in turn is arranged upstream of the second section in the direction of exhaust gas mass flow through the catalyst. In principle, it would be conceivable for the catalyst sections to connect directly to one another, so that there is no section between them that is free of the catalyst and therefore free of a coating that is catalytically effective for the conversion described above. It is also conceivable that the sections are formed as a single unit, that is, from a single piece.Furthermore, it would be conceivable that the sub-sections are spaced apart from each other in the direction of the exhaust gas mass flow through the catalyst, particularly completely, such that a longitudinal region is arranged between the sub-sections in the direction of the exhaust gas mass flow, which is completely free of a coating catalytically effective for the aforementioned conversion. Then, for example, the first sub-section forms a first individual catalyst and the second sub-section a second catalyst. In other words, the sub-sections can then be considered, for example, as individual catalysts, and it is conceivable that the individual catalysts are arranged in a common housing.

[0012] The inventive method can advantageously impair, and in particular reduce, both the catalyst's ability to store oxygen contained in the exhaust gas, also referred to as "oxygen storage capacity," and its ability to perform the aforementioned conversion, also referred to as "conversion performance" or "conversion efficiency." Oxygen storage capacity is also referred to as oxygen storage capacity (OSC). Conversion performance or conversion efficiency is also referred to as catalytic efficiency.With regard to oxygen storage capacity and conversion efficiency, the method makes it possible to reduce the oxygen storage capacity of the first sub-section very quickly, in particular to a minimum, without excessively reducing the overall conversion efficiency of the catalyst. For example, it is possible to rapidly reduce the oxygen storage capacity in the first sub-section of the catalyst, in particular to a minimum, without excessively reducing the overall conversion efficiency of the catalyst.While the oxygen storage capacity of at least the first sub-section, and especially of the catalyst as a whole, is already at a very low level, particularly at the aforementioned minimum, the overall conversion efficiency of the catalyst, although reduced compared to a new catalyst, is still at such a high or good level that the catalyst is still capable of performing the conversion at a fairly high conversion rate. Based on this, the conversion efficiency can ultimately be reduced by further processing, particularly until it reaches a target value, which can be predefined or predetermined.The process thus makes it possible to very quickly reduce the oxygen storage capacity in the first part of the catalyst, in particular to the aforementioned minimum and / or to a first target value, without unduly affecting the overall conversion performance of the catalyst. By continuing the process, the conversion performance is further reduced, and thus the conversion performance can also be brought to a second target value, which can be predefined or predetermined. Since the oxygen storage capacity in the first part of the catalyst is already at its minimum when the overall conversion performance of the catalyst is reduced, the conversion performance can be specifically brought to the second target value without undesirably impairing the oxygen storage capacity.The method according to the invention thus makes it possible to easily adjust the oxygen storage capacity to the first target value and the conversion rate to the second target value. For this purpose, the method can simply be carried out for a certain period of time, and in particular until the conversion rate reaches the second target value, because the oxygen storage capacity will already reach the first target value, especially the minimum, before this point. After the target values ​​for oxygen storage capacity and conversion rate have been reached, the method can simply be stopped, and then, for example, the catalyst will be in the limiting catalyst state. Compared to conventional solutions, the catalyst can thus be brought into the limiting catalyst state particularly easily, quickly, and precisely. Influences due to arbitrariness and chance, such as those that occur in conventional methods, can be avoided by the invention.In other words, the inventive method makes it possible to first quickly bring the oxygen storage capacity to a desired level, i.e., for example, to the first target value and, in particular, to the minimum, whereupon the conversion power can be specifically adjusted to the desired second target value. This allows the catalyst to be brought into the limiting catalyst state quickly, precisely, and without arbitrary or random events.

[0013] To age the catalyst particularly advantageously, simply, quickly, and in a controlled manner, it is preferably provided that the exhaust gas mass flow rate during the aging phase is at most 1000 kilograms per hour, and in particular less than 1000 kilograms per hour. More preferably, it is provided that the exhaust gas mass flow rate during the aging phase is at most 400 kilograms per hour, in particular at most 350 kilograms per hour, and most preferably at most 300 kilograms per hour. Preferably, the exhaust gas mass flow rate during the aging phase is at most 300 kilograms per hour.This results in a relatively low exhaust gas mass flow, which rapidly reduces the oxygen storage capacity, particularly of the first section of the catalyst and thus of the catalyst as a whole. This allows it to be brought down to the first target value, specifically to the minimum, without excessively reducing the overall conversion efficiency of the catalyst. By subsequently repeating the process, the overall efficiency of the catalyst can then be further reduced and thus brought down to the second target value.

[0014] Another embodiment is characterized by the fact that a regeneration phase is carried out at least once after the aging phase. During the regeneration phase, the internal combustion engine is operated under load, resulting in a rich exhaust gas mixture. This means that during the regeneration phase, the internal combustion engine is operated in a rich mixture overall, i.e., continuously and without interruption, with a rich, particularly global, combustion ratio. Consequently, the exhaust gas during the regeneration phase has a composition resulting from the fact that the internal combustion engine is operated overall, i.e., continuously and without interruption, with a rich air-fuel ratio that is less than 1, particularly less than 0.99.In this process, the rich exhaust gas forms an exhaust gas mass flow during the regeneration phase, which is passed through the catalyst and, in particular, has a consistently and / or constantly maintained temperature, also referred to as the "second temperature," which is less than 900 degrees Celsius. For example, the second temperature can be lower than the base temperature. Preferably, the second temperature is greater than 600 degrees Celsius. Preferably, the second temperature is 800 degrees Celsius. The regeneration phase counteracts the aging caused by the aging phase, as the regeneration phase regenerates the catalyst, also simply called the catalytic converter. The regeneration phase serves to stabilize the catalyst's properties with regard to oxygen storage capacity (OSC) and conversion or conversion performance through a partial regeneration.This makes the catalytic converter immediately usable in its behavior, without having to deal with an arbitrarily occurring regeneration.

[0015] Preferably, the aging phase is carried out several times in succession, in particular such that the regeneration phase is carried out once between each successive aging phase. In simplified terms, one regeneration phase is performed between each successive aging phase, which advantageously reduces the oxygen storage capacity and the conversion rate, thus allowing the catalyst to be brought to the limiting catalyst state particularly quickly and easily.

[0016] To achieve particularly advantageous aging of the catalyst, a further embodiment of the invention provides that the internal combustion engine is operated under fire during the regeneration phase, specifically by operating the first and second combustion chambers continuously. It is preferably provided that, during the regeneration phase, unfired operation of a combustion chamber of the internal combustion engine, and thus, for example, of a cylinder forming a combustion chamber of the internal combustion engine, is omitted, particularly continuously. Thus, for example, the first and second combustion chambers are each operated with a rich mixture, i.e., with a rich air-fuel ratio, resulting in a rich exhaust gas during the regeneration phase.

[0017] Another embodiment is characterized in that the regeneration phase lasts at least two minutes. Preferably, the regeneration phase lasts less than ten minutes. For example, the regeneration phase lasts ten minutes, and for example, the regeneration phase lasts at most ten minutes. This allows the catalyst to be brought to the limiting catalyst state particularly quickly and easily.

[0018] In a further, particularly advantageous embodiment of the invention, it is provided that the regeneration phase lasts shorter than the aging phase, which allows the catalyst to be brought into the limiting catalyst state particularly quickly.

[0019] In a further, particularly advantageous embodiment of the invention, it is provided that during the regeneration phase, unfired operation of a combustion chamber of the internal combustion engine is omitted, in particular continuously, whereby the oxygen storage capacity and the conversion performance can be brought particularly advantageously and specifically to the respective target values.

[0020] In order to bring the catalyst into the limiting catalyst state particularly quickly and easily, a further embodiment of the invention provides that the aging phase lasts at least 60 minutes.

[0021] During the second part of the aging phase, for example, the second combustion chamber is shut down several times in succession, with the second combustion chamber being operated in the same manner as the first combustion chamber between two shutdowns. During the second part of the aging phase, the second combustion chamber is shut down at least ten times, in particular at least 20 times, with the second combustion chamber being shut down more than ten times, in particular more than 20 times. During the second part of the aging phase, the second combustion chamber is shut down at most 100 times, in particular at most 80 times, and most especially at most 50 times, in particular less than 50 times.This allows the catalyst to be aged particularly advantageously and to be brought into the limiting catalyst state particularly quickly and easily.

[0022] Finally, it has proven particularly advantageous if, during the second part of the aging phase, the peak temperature of the catalyst exceeds 1000 degrees Celsius, at least temporarily and at least once, and in particular several times. Preferably, the peak temperature is at least 1050 degrees Celsius. For example, the peak temperature is greater than 1100 degrees, and in particular greater than 1130 degrees Celsius. In other words, during the second part of the aging phase, the internal combustion engine is operated in such a manner that the exhaust gas mass flow reaches the peak temperature, at least temporarily, and in particular several times in succession.

[0023] The process according to the invention enables targeted and artificial aging of the catalyst, in particular to bring the catalyst, for example designed as a three-way catalyst, to the limiting catalyst state with regard to oxygen storage capacity and conversion performance, i.e., to a level of the, for example, predetermined limiting catalyst. Subsequently, it is possible, for example, to use the catalyst aged by means of the process according to the invention and thus exhibiting the limiting catalyst state, i.e., by carrying out tests on the catalyst aged by means of the process.These tests can provide information and data that, for example, in a vehicle equipped with a catalytic converter system, can precisely determine whether and / or when the system has aged to such an extent due to vehicle operation that it reaches the limit state. In other words, this information and data can be used to program the vehicle's control unit, enabling it to accurately detect whether and / or when the catalytic converter system has reached this condition. Consequently, measures can be taken to ensure low-emission operation of the vehicle.

[0024] Preferably, the exhaust gas mass flow rate during the regeneration phase is at most 1000 kilograms per hour, and in particular less than 1000 kilograms per hour. For example, the exhaust gas mass flow rate during the regeneration phase is less than 800 kilograms per hour.

[0025] It is conceivable that during the aging phase, the exhaust gas and thus the exhaust gas mass flow is passed through the catalyst at a space velocity of at most 555000 1 / h with reference to the first part of the catalyst.

[0026] During the second part of the aging phase, the formation of the second combustion chamber is carried out and the internal combustion engine as a whole, that is, considered holistically, is operated so lean, that is, with such a lean, in particular global, combustion air ratio, that the peak temperature is preferably at least 1000 degrees Celsius.

[0027] Further insights and considerations underlying the invention are that modern motor vehicles use on-board diagnostics (OBD) to monitor emissions during operation. This helps prevent excessive increases in emissions. In particular, it is desirable to recognize that an exhaust aftertreatment system, such as a catalytic converter system for treating the exhaust gas of an internal combustion engine, can reach a state during the vehicle's operation in which exhaust aftertreatment is no longer as effective as desired. This state is, for example, the aforementioned limiting state of the catalytic converter. Using so-called OSC diagnostics, an OSC level can be measured, based on which conclusions can be drawn about the catalytic effectiveness of the catalytic converter system.If the catalytic converter system has aged to the point where it can no longer adequately treat the exhaust gas, then the catalytic converter system is in its limiting state. Ideally, on-board diagnostics should be able to distinguish between different states of such a catalytic converter system with sufficient precision, meaning with sufficient accuracy, one of which is the limiting state. On-board diagnostics are usually subject to tolerances, making it difficult to differentiate between these states. Since chemical components used in a catalytic converter that contribute to oxygen storage are more stable with age than chemical components that contribute to conversion, deliberately bringing a catalytic converter into its limiting state is typically not straightforward.Common methods for the targeted aging of catalysts, in order to bring these catalysts into the limiting catalyst state, reduce both the oxygen storage capacity (OSC) and the catalytic effectiveness, and thus the conversion performance, without any particular differentiation.

[0028] The aforementioned problems and disadvantages can be avoided by the invention. The aging of the catalyst achievable by the inventive method is an artificial limit catalyst aging that advantageously limits the oxygen storage capacity to a threshold value, thus reducing the first target value and resulting in impaired operation with regard to oxygen storage capacity. The method makes it possible to generate data from the aged catalyst in order to detect such impaired operation using appropriate diagnostics. Furthermore, it is possible to achieve high discriminatory power with the selectively aged catalyst using the method, so that, for example, the OBD in a vehicle can differentiate between the aforementioned states.A second state is, for example, a fully broken-in state, and a third state is, for example, an intermediate state in which the catalyst system can treat the exhaust gas better than in the limiting catalyst state, but worse than in the fully broken-in state. The process according to the invention can be carried out in a time- and cost-effective manner and is reproducible, thereby enabling the catalyst to be aged advantageously and in a targeted manner.

[0029] The low base temperature of less than 900 degrees Celsius (°C) ensures minimal aging, which only becomes significant due to the isolation of the first section of the catalyst. This low base temperature of less than 900 degrees Celsius allows for advantageous, increased thermal aging of the entire catalyst. Due to the preferably low exhaust gas mass flow and the preferably short isolation of the second combustion chamber, the first section of the catalyst is primarily, or even predominantly, affected by aging. Because of the low amount of reactants associated with the low exhaust gas mass flow and the isolation of the second combustion chamber, as well as the low space velocity, an exothermic temperature is concentrated in the first section of the catalyst. The peak temperature is, for example, in the range of 1051 degrees Celsius.The second section of the catalyst, however, has the same or a similar base temperature as the first section and only experiences waste heat from the first section without itself experiencing or generating any significant exothermic activity. Subsequent catalysts are thus aged more gently. In other words, the second section of the catalyst ages more gently than the first. Through the targeted thermal aging of the first section of the catalyst with the lean exhaust gas, the oxygen storage capacity and thus the catalytic efficiency, and consequently the conversion performance, are significantly reduced within a short time. The process according to the invention is particularly characterized by the fact that the oxygen storage capacity, at least or especially of the first section of the catalyst, can be reduced within a few hours, particularly to the minimum and / or the first target value.The catalytic efficiency (conversion rate) of the entire catalyst, however, experiences only moderate deterioration up to this point. A subsequent, further execution of the process then serves to precisely adjust the conversion rate, particularly to the second target value, so that the limiting catalyst state can be achieved particularly easily. The underlying reason for this is that the lean exhaust gas causes continuously rapid aging of the catalyst. Certain catalyst technologies can also exhibit accelerated aging with a rich exhaust gas.

[0030] The test bench is an engine test bench comprising the internal combustion engine and the catalytic converter. For example, the internal combustion engine is initially operated at a load point, particularly one that is constant at least at this point. This results in an exhaust gas mass flow and a base temperature of less than 900 degrees Celsius, particularly at least in the first part of the operating range, during the aging phase. If the base temperature is stable, at least in the excessive range, the second combustion chamber, or in particular several combustion chambers of the internal combustion engine, is preferably briefly shut off. This leads to the high peak temperature in the catalytic converter, at least in the first part of the operating range. During the shut-off of the second combustion chamber, only air is passed through it, without introducing fuel into the second combustion chamber and without burning fuel in the second combustion chamber.This results in the second combustion chamber operating with excess air. This excess air is counteracted, and specifically regulated, by enriching the mixture in the operating, first combustion chamber. Enriching the mixture in the operating, first combustion chamber means that it is run rich, i.e., with a rich air-fuel ratio. This allows the exhaust gas to be supplied as a lean mixture overall, even during the second part of the aging phase. Consequently, the internal combustion engine as a whole, i.e., holistically and thus globally considered, can be operated with a lean air-fuel ratio throughout the second part of the aging phase.The enrichment of the first combustion chamber results in excess, i.e., unburned hydrocarbons contained in the exhaust gas, which, resulting from the excess air, are combusted in or on the catalyst, particularly in or on the first part of the catalyst, and thereby, due to the aforementioned exotherms, cause the aforementioned peak temperature in the catalyst, particularly at least in the first part.

[0031] In the event that the aforementioned excess air from the exclusion of the second combustion chamber is insufficient to generate the desired high peak temperature, the following, for example, can be provided: The test bench has, for instance, an exhaust gas tract through which the exhaust gas flows, in which the catalyst is located, so that during the aging phase and preferably also during the regeneration phase, the exhaust gas is routed through the exhaust gas tract and thus through the catalyst. It is possible to introduce air as secondary air into the exhaust gas tract at an inlet point located downstream of the combustion chambers and upstream of the catalyst, bypassing, in particular all, the combustion chambers. The secondary air is supplied, for example, by a compressed air source and / or delivered by means of a pump, which may be electrically operated.Thus, secondary air is introduced into the exhaust system at the inlet point, bypassing the combustion chambers of the internal combustion engine, and consequently into the exhaust gas flowing through the exhaust system. As a result, the oxygen contained in the secondary air can combust with the excess hydrocarbons in the catalyst, achieving a beneficially high peak temperature. Secondary air can be used or introduced into the exhaust system particularly when the excess air resulting from the deactivation of the second combustion chamber is insufficient to generate a sufficiently high peak temperature. In such cases, the mixture in the operating, fired primary combustion chamber should be enriched to ensure that the exhaust gas passing through the catalyst is lean overall.

[0032] Since the formation of the second combustion chamber is carried out at least once, preferably several times, during the second part of the aging phase, this second part constitutes a high-temperature component of the aging phase. In relation to the process as a whole, the aging phase constitutes a high-temperature component because the catalyst is aged advantageously during and through the aging phase, particularly compared to the regeneration phase. In the first part of the aging phase, for example, a target operating point is set such that the exhaust gas mass flow has a base temperature that is stabilized, so that during the first part, the exhaust gas mass flow maintains a base temperature that is essentially constant for at least several seconds. Subsequently, the second part of the aging phase is carried out, during which the deactivation of the second combustion chamber takes place.The deactivation of the second combustion chamber, for example, lasts several seconds. Between two deactivations of the second combustion chamber, there is a waiting period of several seconds, during which the deactivation of the second combustion chamber is completely suspended. This prevents excessively high temperatures of the exhaust gas and the catalyst, thus avoiding undesirable damage to the catalyst. To precisely control the aging of the catalyst and / or to monitor its oxygen storage capacity, a measurement is taken after the aging phase, specifically after each aging phase. This measurement assesses the emissions in the exhaust gas downstream of the catalyst and / or the catalyst's oxygen storage capacity.The measurement can be performed after the aging phase and before the regeneration phase, or after the aging phase and after the regeneration phase. Based on the measurement, the current aging state of the catalyst is determined and evaluated. If, for example, it is determined that the current aging state of the catalyst corresponds to the limiting catalyst state, the process is terminated. If, for example, it is determined that the current aging state of the catalyst does not yet correspond to the limiting catalyst state, the process is continued, specifically until the current aging state of the catalyst corresponds to the limiting catalyst state.

[0033] Further features of the invention will become apparent from the claims, the figure, and the figure description. The features and combinations of features mentioned above in the description, as well as the features and combinations of features mentioned below in the figure description and / or shown in the figure alone, are not only usable in the combinations specified, but also in other combinations or on their own.

[0034] Further details of the invention will become apparent from the following description of a preferred embodiment with the accompanying drawing. The only illustration shown is... Fig. 1. A schematic and cutaway side view of a test rig, by means of which a method for the targeted aging of a catalyst is carried out. Fig. Figure 1 shows a section of a schematic sectional view of a test rig 1 for the targeted aging of a catalyst 2. Based on Fig. In the following, a method for the targeted aging of the catalyst 2 is described, wherein the catalyst 2 is selectively aged using the test rig 1. In this method, the test rig 1 comprises the catalyst 2 and an internal combustion engine 3, also referred to as a combustion engine or internal combustion power unit, which is shown in a particularly schematic representation. The test rig 1 also includes an exhaust system 4 in which the catalyst 2 is arranged.

[0035] In this process, the internal combustion engine 3 has at least or exactly two combustion chambers, namely a first combustion chamber 5 and a second combustion chamber 6. The process involves repeatedly performing an aging phase, specifically by carrying out several successive aging phases. During the aging phase, the internal combustion engine 3 is operated under fire, resulting in an overall lean exhaust gas. For this purpose, during the aging phase, the internal combustion engine 3 is operated with a lean air-fuel ratio overall, and thus globally. The term "global" with regard to the air-fuel ratio means that the internal combustion engine 3 is operated with a lean air-fuel ratio overall, and thus globally.The term "lean exhaust gas" refers to the fact that the exhaust gas has a composition resulting from the fact that the internal combustion engine 3 is operated under lean conditions overall. During the aging phase, the exhaust gas from the internal combustion engine 3 forms a mass flow, also referred to as the first exhaust gas mass flow, which is routed through the exhaust system 4 and thus through the catalyst 2.

[0036] At the in Fig. In the embodiment shown in Figure 1, the catalyst 2 has, in particular, exactly, two sub-sections, namely a first sub-section T1 and a second sub-section T2. ​​It can be seen that, in the direction of flow of the exhaust gas mass flow through the catalyst 2, sub-section T2 is arranged downstream of sub-section T1. In the embodiment shown in Figure 1, the catalyst 2 has two sub-sections, namely a first sub-section T1 and a second sub-section T2. Fig. In the embodiment shown in Figure 1, the sub-sections T1 and T2 are completely spaced apart from each other in the direction of flow of the exhaust gas mass flow through the catalyst 2, such that a length section L is arranged between sub-sections T1 and T2 in the direction of flow of the exhaust gas mass flow through the catalyst 2. This length section is completely free of components that are catalytically active for post-treatment of the exhaust gas. In contrast, the sub-sections T1 and T2 have catalytically active components, in particular a catalytically active coating, wherein the catalytically active components are catalytically active for post-treatment of the exhaust gas.This means that the catalytically active components catalytically induce and / or support chemical reactions by which components contained in the exhaust gas, such as carbon monoxide, unburned hydrocarbons, nitric oxide, and nitrogen dioxide (or nitrogen oxides in general), are converted into carbon dioxide, water, and, in particular, pure nitrogen. This conversion is also referred to as conversion. The capacity or efficiency of catalyst 2 to carry out this conversion is also referred to as conversion efficiency or conversion capability. Furthermore, catalyst 2 has an ability, also known as oxygen storage capacity (OSC), to store any oxygen contained in the exhaust gas. The oxygen storage capacity is achieved, for example, by the aforementioned catalytically active components and / or other components.

[0037] Alternatively, it would be conceivable that sections T1 and T2 connect directly to each other, so that, in the direction of flow of the exhaust gas mass flow through catalyst 2, no length section is arranged between sections T1 and T2 that is completely free of components catalytically active for conversion. However, in the present case, length section L is completely free of components catalytically active for conversion.

[0038] During the aging phase, for example, the exhaust gas mass flow is lower than a limit value, and therefore an advantageously low exhaust gas mass flow. The limit value is, for example, 1000 kilograms per hour.

[0039] During the first part of the aging phase, the internal combustion engine 3 is operated with combustion, specifically by firing the first combustion chamber 5 and the second combustion chamber 6. This results in the engine 3 providing an overall lean exhaust gas mixture. The engine thus operates with a lean air-fuel ratio, and this lean exhaust gas forms the exhaust mass flow, which has a base temperature of less than 900 degrees Celsius during this first part and is passed through the exhaust tract 4 and the catalyst 2. During the second part of the aging phase, which directly follows the first part, the internal combustion engine 3 is operated with combustion, specifically by firing the first combustion chamber 5 and operating the second combustion chamber 6 without combustion. This is also referred to as cylinder 6 silencing or cylinder silencing.Thus, combustion chamber 6 is or will be deactivated during the second part of the aging phase. As a result, during this second part, air is pumped through combustion chamber 6 without any fuel being introduced. This allows the internal combustion engine 3 to provide the overall lean exhaust gas during the second part of the aging phase, which forms the exhaust gas mass flow that is passed through the catalyst 2. The unfired operation of combustion chamber 6 during the second part of the aging phase results in a surplus of air being provided or caused by combustion chamber 6, which is at least partially compensated for by the fact that combustion chamber 5 is run rich, i.e., with a rich air-fuel ratio.The excess air results in oxygen being present in the exhaust gas, and the rich combustion of the combustion chamber 5 results in unburned hydrocarbons being present in the exhaust gas. These unburned hydrocarbons are oxidized, and thus combusted, in the catalyst 2 with the oxygen contained in the exhaust gas, causing a peak temperature in the catalyst 2 that is higher than the base temperature at least once during the second part of the aging phase. The peak temperature is greater than 900 degrees Celsius, and in particular greater than 1000 degrees Celsius. The process rapidly reduces the oxygen storage capacity of the catalyst 2, especially in the first section T1, to an initial target value, specifically to a minimum, without significantly reducing the conversion rate. By continuing the process, the conversion rate is then further reduced.Consequently, by continuing the process, the conversion rate can be specifically adjusted to a second target value. By adjusting the oxygen storage capacity to the first target value and the conversion rate to the second target value, catalyst 2 can be quickly, easily, and precisely brought into a so-called limiting catalyst state.

[0040] Preferably, a regeneration phase, in particular exactly one, is performed between each aging phase. During the regeneration phase, the internal combustion engine 3 is operated under load, thereby producing an overall rich exhaust gas. This means that during the regeneration phase, the internal combustion engine 3 operates with a globally rich air-fuel ratio. During the regeneration phase, the rich exhaust gas, also referred to as a second exhaust gas mass flow, is passed through the catalyst 2, i.e., through the exhaust tract 4 and the catalyst 2, and has a temperature of less than 900 degrees Celsius.

[0041] In Fig. Figure 1 shows an arrow 7 illustrating the direction of flow in which the exhaust gas and thus the respective exhaust gas mass flow is directed through the exhaust tract 4 and thus through the catalyst 2.

[0042] In Fig. Figure 1 also shows diagram 8. Diagram 8 has an abscissa 9, on which a path length, in particular through the catalyst 2, is plotted. On an ordinate 10 of diagram 8, the temperature of the exhaust gas, also referred to as the exhaust gas temperature, is plotted. A curve 11 of diagram 8 shows a temperature profile in the catalyst 2 during the exposure period. It can be seen that the second part of the aging phase is a high-temperature phase, in which the high peak temperature in the catalyst 2 occurs.

[0043] Figure 12 illustrates a temperature profile in catalyst 2 during the saturation phase when the exhaust gas mass flow rate, which is passed through the exhaust tract 4 and thus through catalyst 2, is greater than the limit value. It can be seen that because the exhaust gas mass flow rate is lower than the limit value and therefore advantageously low, a very high temperature can be achieved in the first sub-section T1, particularly during the aging phase, and in this case, a higher temperature in sub-section T1 than in sub-section T2. ​​This allows the oxygen storage capacity, especially in the first sub-section T1, to be rapidly reduced, so that the oxygen storage capacity of catalyst 2, particularly in the first sub-section T1, can be reduced to the first target value very quickly without excessively reducing the overall conversion performance of catalyst 2.The background to this is that the first sub-area, T1, is monitored via OBD, which measures the oxygen storage capacity (OSC). Therefore, the OSC is reduced to a minimum value.

[0044] The overall conversion performance of catalyst 2 can be selectively reduced to the second target value after the oxygen storage capacity has been rapidly reduced to the first target value by simply continuing the process after the oxygen storage capacity has been reduced to the first target value. Test rig 1 also includes a first lambda sensor 13 and a second lambda sensor 14. Using the respective lambda sensors 13 and 14, a specific parameter characterizing the residual oxygen content in the exhaust gas can be measured at a respective measuring point M1 and M2. It can be seen that measuring point M1 is located upstream of catalyst 2 in the direction of exhaust gas mass flow through the catalyst 2, while measuring point M2 is located downstream of subsection T1 and upstream of subsection T2.Thus, subsection T1 is or constitutes a so-called monitored volume of catalyst 2, since the residual oxygen content in the exhaust gas is measured both at measuring point M1 (upstream of subsection T2) and at measuring point M2 (downstream of subsection T2). In contrast, subsection T2 is or constitutes an unmonitored volume of catalyst 2, since the residual oxygen content in the exhaust gas is not measured or cannot be measured downstream of subsection T2. ​​In particular, the oxygen storage capacity can be determined and thus measured by measuring and thus recording the measured quantity, since this quantity, for example, also characterizes the oxygen storage capacity. It is evident that the method enables zoned aging of catalyst 2.Through this process, and especially through the aging phase and, in particular, through the isolation of combustion chamber 6, sub-section T1 can be subjected to high stress and significant aging, while sub-section T2 is protected. This allows the oxygen storage capacity to be rapidly reduced to the first target value, and especially to a minimum, without unduly reducing the conversion performance. Due to this initial protection of the rear, second sub-section T2 compared to the front, first sub-section T1, the catalyst 2 still exhibits good overall conversion performance after the oxygen storage capacity has been reduced to the first target value. By continuing the process, the conversion performance can then be further reduced and, in particular, brought to the second target value.The process is thus carried out until the conversion rate reaches or falls below the second target value. Then both target values ​​are achieved through the oxygen storage capacity and the conversion rate, and catalyst 2 exhibits the desired limiting catalyst state.

[0045] Test bench 1, for example, has a Fig. 1. A measuring device (not shown in detail) is used to measure at least one further quantity, which characterizes the conversion performance. By measuring this further quantity, the conversion performance can be monitored, allowing, for example, the determination of a time at which the conversion performance is less than or equal to the second target value. The process can then be terminated, and the catalyst 2 will have reached the desired limit state. Reference symbol list 1 test bench 2 catalyst 3 Internal combustion engine 4 Exhaust system 5 first combustion chamber 6 second combustion chamber 7 Arrow 8 Diagram 9 Abscissa 10 ordinates 11 Course 12 Course 13 Lambda sensor 14 Lambda sensor L Length range M1 measuring point M2 measuring point T1 first sub-area T2 second sub-area

Claims

[1] Method for the targeted aging of a catalyst (2), wherein the method is carried out by means of a stationary test bench (1) comprising the catalyst (2) designed as a three-way catalyst and an internal combustion engine (3), different from a vehicle, wherein: - the internal combustion engine (3) has at least two combustion chambers (5, 6), namely a first combustion chamber (5) and a second combustion chamber (6); - the catalyst (2) is deliberately aged and thereby brought into a limiting catalyst state; and - an aging phase is carried out in which: ◯ the internal combustion engine (3) is operated, whereby the internal combustion engine (3) provides an overall lean exhaust gas, which forms an exhaust gas mass flow that is passed through the catalyst (2); ◯ during a first part of the aging phase, the internal combustion engine (3) is operated by firing the first combustion chamber (5) and the second combustion chamber (6), whereby the internal combustion engine (3) provides the overall lean exhaust gas, which forms the exhaust gas mass flow that has a base temperature of less than 900 degrees Celsius during the first part and is passed through the catalyst (2); and ◯ during a second part of the aging phase, the internal combustion engine (3) is operated by firing the first combustion chamber (5) and operating the second combustion chamber (6) unfired, whereby the internal combustion engine (3) provides the overall lean exhaust gas which forms the exhaust gas mass flow that is passed through the catalyst (2). [2] Method according to claim 1, characterized by , that during the aging phase the exhaust gas mass flow is less than 1000 kilograms per hour. [3] Method according to claim 1 or 2, characterized by , that after the aging phase a regeneration phase is carried out in which the internal combustion engine (3) is operated, whereby the internal combustion engine (3) provides an overall rich exhaust gas which forms an exhaust gas mass flow which is passed through the catalyst (2) and has a temperature which is less than 900 degrees Celsius. [4] Method according to claim 3, characterized by , that during the regeneration phase the internal combustion engine (3) is operated by firing the first combustion chamber (5) and the second combustion chamber (6). [5] Method according to claim 3 or 4, characterized by that the temperature is at most 800 degrees Celsius. [6] Method according to any one of claims 3 to 5, characterized by that the regeneration phase lasts at least two minutes. [7] Method according to any one of claims 3 to 6, characterized by that the regeneration phase is shorter than the aging phase. [8] Method according to any one of claims 3 to 7, characterized by , that during the regeneration phase an unfired operation of a combustion chamber of the internal combustion engine (3) does not occur. [9] Method according to any one of the preceding claims, characterized by that the aging phase lasts at least 60 minutes. [10] Method according to any one of the preceding claims, characterized by , that the second part of the aging phase causes at least a temporary peak temperature of the catalyst of more than 1000 degrees Celsius.

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