Abstract: The present invention provides a process and a device for regeneration of a nitrogen oxide storage catalyst in the exhaust system of a diesel engine. The process comprises a first and a second regeneration strategy. The first regeneration strategy is applied when the exhaust gas temperature is above a threshold value and comprises changing the air/fuel-ratio from a lean to a rich value during a first regeneration period. The second regeneration strategy is applied when the exhaust gas temperature is below a threshold value and comprises switching the air/fuel-ratio back and forth between lean and rich air/fuel-ratios, forming a sequence of between 2 and 10 rich pulses and between 2 and 10 lean pulses during a second regeneration period.

Abstract: The invention relates to particle filters having an open pore structure for separating particles from fluids, which, for modification of their properties or for treatment of the fluid to be filtered, are provided with additional metal oxides or mixed metal oxides and optionally with further catalytically active components. In particular, the invention relates to particle filters treated with a catalytically active material, which is used for the treatment of the waste gases from combustion processes, in particular for the treatment of the exhaust gases of internal combustion engines. By impregnation of the filter bodies in a solution of a metal oxide sol or a mixed metal oxide sol, the preformed sol particles are deposited on the pore surfaces. Consequently, catalytic activations of the filter with good temperature stability in combination with a moderate increase in the exhaust gas back-pressure are possible.

Abstract: The present invention relates to a method of removing nitrogen oxides from the exhaust gas of a lean-burn internal combustion engine by selective catalytic reduction (SCR) using ammonia. The exhaust gas is routed first over a platinum-containing pre-catalyst and then over an SCR catalyst. The ammonia needed for the selective catalytic reduction is added to the exhaust gas upstream of the pre-catalyst at an exhaust-gas temperature below 250° C., while it is supplied to the exhaust gas between the pre-catalyst and the SCR catalyst at an exhaust gas temperature above 150° C. By adopting this procedure, a very large temperature range for the selective catalytic reduction with high nitrogen conversion rates is obtained.

Abstract: The invention relates to a method and an apparatus of operating a drive system comprising an engine and an exhaust gas purification unit containing a catalyst, where the engine emits an exhaust gas having an exhaust gas temperature and the catalyst has a catalytic activity for the purification of the exhaust gas. In the method, an aging-induced decrease in the catalytic activity of the catalyst is compensated at least part of the time by increasing the exhaust gas temperature of the engine.

Abstract: The present invention relates to an exhaust gas cleaning catalyst comprising on a honeycomb carrier a catalytic coating. Said honeycomb carrier has an upstream end and a downstream end and a plurality of flow channels are running from the upstream end to the downstream end. The catalytic coating comprises catalytically active precious metal components of which at least one component exhibits a concentration profile along the honeycomb carrier starting with a low concentration at the upstream end which increases along the flow channels up to a maximum value and then decreases again to the downstream end.

Abstract: When a nitrogen oxide storage catalyst is being regenerated, the regeneration may be terminated for example as a result of a premature load change in the engine, which can lead to incomplete emptying of the storage catalyst. The residual filling level which remains in the catalyst following an incomplete regeneration of this nature is used as the starting value for calculation of the filling level during the next storage phase. After incomplete regeneration, the nitrogen oxide conversion rate is initially greater than would be expected, on account of the residual filling level. By taking this increased conversion rate into account when calculating the filling level during the storage phase, it is possible to further improve the accuracy of the calculation.

Abstract: An oxygen storage material comprising cerium oxide and at least one second oxide of a metal M1 is disclosed as well as a process for manufacturing the material and the use of this material in an exhaust gas cleaning catalyst. In a preferred embodiment the oxygen storage material comprises particles from a Ce/M1 mixed oxide solid solution coated with an oxide of another metal M2. Metal M1 e.g. can be calcium or zirconium while metal M2 most preferably is aluminum.

Abstract: This invention relates to a method of operating a catalyst for treating the exhaust gas of an internal combustion engine, the catalyst comprising, in addition to catalytically active noble metals, also storage components for storing hydrocarbons. During engine operating phases at low exhaust-gas temperatures, such a catalyst stores the hydrocarbons contained in the exhaust gas without burning them. When the exhaust-gas temperature rises, these hydrocarbons are desorbed again and then oxidized at the catalytically active noble metals. This process can lead to uncontrolled, vigorous combustion of the hydrocarbons stored on the catalyst and, therefore, damage to the catalyst. According to the invention, this damage is avoided by continuously calculating the respective loading of the storage components with hydrocarbons and repeatedly regenerating the storage components depending on the loading by temporarily raising the exhaust-gas temperature before damage to the catalyst can occur.

Abstract: An oxygen storage material based on cerium oxide with at least one other oxide of the metals silicon and zirconium, wherein the cerium oxide and the other oxides are present in the form of a mixed oxide. The material is obtainable in that hydroxidic precursors of the mixed oxide are first prepared in a manner known per se using a wet-chemical route, these precursors are optionally dried at temperatures between 80 and 300° C. and the dried precursors are then treated under a hydrogen-containing atmosphere at a temperature between 600 and 900° C. for a period of 1 to 10 hours. The reductive thermal treatment endows the material with a greatly improved dynamic behavior as compared with conventional calcination in air.

Abstract: The present invention describes an exhaust-gas purification system for an internal combustion engine made of an oxidation catalyst arranged close to the engine, a subsequent hydrocarbon adsorber and a particulate filter arranged downstream thereof and provided with another oxidation catalyst. The oxidation catalyst ensures that emission limits with respect to carbon monoxide and hydrocarbons are satisfied in normal driving mode. During operating states with exhaust-gas temperatures below about 200° C., the oxidation catalyst can no longer oxidize carbon monoxide and hydrocarbons. Instead, the hydrocarbons are adsorbed by the hydrocarbon adsorber during these operating phases. In order to initiate the periodical regeneration of the particulate filter, the exhaustgas temperature of the internal combustion engine is raised by engine modifications.

Abstract: The invention relates to a catalyst arrangement for purifying the exhaust gases of internal combustion engines operated under lean conditions. It is proposed that a thinwalled, porous carrier be coated on one side with a nitrogen oxide storage catalyst and on the other side with an SCR catalyst. When the exhaust gas is passed through the catalytic coatings and the support material, a significant improvement in the nitrogen oxide conversion is achieved compared to a series arrangement of the catalysts on separate carriers. Wall flow filters have been found to be useful as thin-walled carriers.

Abstract: The present invention relates to an exhaust-gas purification system for the selective catalytic reduction of nitrogen oxides. The system includes at least one catalyst having catalytically active components for the selective catalytic reduction (SCR components). An NOx storage catalyst (5) is arranged upstream of the SCR catalyst (3) in the exhaust-gas purification system. For performing the selective catalytic reduction, metering means (8) for supplying a compound decomposable into ammonia is provided between the NOx storage catalyst and the SCR catalyst (3). At low exhaust-gas temperatures, the NOx storage catalyst (5) adsorbs the nitrogen oxides contained in the exhaust gas and desorbs them only at rising exhaust-gas temperatures, so that they can afterwards be converted by the SCR catalyst (3) which is active then. This results in an altogether improved conversion rate for the nitrogen oxides.

Abstract: An oxygen storage material comprising cerium oxide and at least one second oxide of a metal M1 is disclosed as well as a process for manufacturing the material and the use of this material in an exhaust gas cleaning catalyst. In a preferred embodiment the oxygen storage material comprises particles from a Ce/M1 mixed oxide solid solution coated with an oxide of another metal M2. Metal M1 e.g. can be calcium or zirconium while metal M2 most preferably is aluminum.

Abstract: The present invention relates to a method of removing nitrogen oxides from the exhaust gas of a lean-burn internal combustion engine by selective catalytic reduction (SCR) using ammonia. The exhaust gas is routed first over a platinum-containing pre-catalyst and then over an SCR catalyst. The ammonia needed for the selective catalytic reduction is added to the exhaust gas upstream of the pre-catalyst at an exhaust-gas temperature below 250° C., while it is supplied to the exhaust gas between the pre-catalyst and the SCR catalyst at an exhaust gas temperature above 150° C. By adopting this procedure, a very large temperature range for the selective catalytic reduction with high nitrogen conversion rates is obtained.

Abstract: The invention relates to a method and an apparatus of operating a drive system comprising an engine and an exhaust gas purification unit containing a catalyst, where the engine emits an exhaust gas having an exhaust gas temperature and the catalyst has a catalytic activity for the purification of the exhaust gas. In the method, an aging-induced decrease in the catalytic activity of the catalyst is compensated at least part of the time by increasing the exhaust gas temperature of the engine.

Abstract: The present invention is directed to a particle filter to remove soot from the exhaust gas of a diesel engine. The particle filter contains a catalytically active coating on a filter body to accelerate burn-off during a regeneration phase of the soot particles collected on the filter. The particle filter comprises a catalytic coating containing compounds of barium, compounds of magnesium, and at least one element of the platinum group metals. The invention is further directed to a process for accelerated combustion of soot particles collected on the filter from lean exhaust gas of a diesel engine in which the soot particles have a soot ignition temperature and the particle filter is actively regenerated from time to time by raising the temperature of the particle filter above the soot ignition temperature and burning off the soot particles.

Abstract: The invention relates to a method of determining activity and aging behavior of a catalyst. For this purpose, two independent substreams of combustion offgases are produced and mixed before coming into contact with the catalyst. The first substream of combustion offgases is preferably produced by burning a motor fuel and forms the major part of the combustion offgases. The second substream of combustion offgases is produced by means of a gas burner whose air ratio can be adjusted within a wide range. Mixing of this second substream of combustion offgases into the first substream enables the composition of the total stream to be set in a defined manner.

Abstract: The present invention relates to a catalyst for the purification of exhaust gases from an internal combustion engine, which comprises a catalytically active coating on an inert ceramic or metal honeycomb body, said coating comprising at least one platinum group metal selected from the group consisting of platinum, palladium, rhodium and iridium on a fine, oxidic support material. As an oxidic support material, the catalyst comprises a low-porosity material on the basis of silicon dioxide that comprises aggregates of essentially spherical primary particles having an average particle diameter of between 7 and 60 nm.

Abstract: The invention relates to a process for the coating of a catalyst support with a catalytically active coat using a coating dispersion, the catalyst support containing at least two partial structures which differ in their absorptivity for the coating dispersion. The process is characterised in that the absorptivity of the partial structures is modified relative to one another by precoating of the catalyst support with a material which can be burnt out or with liquid, and the catalytic coat is then applied to the filter body in a known manner, dried and/or calcined.

Abstract: An oxygen storage material comprising cerium oxide and at least one second oxide of a metal M1 is disclosed as well as a process for manufacturing the material and the use of this material in an exhaust gas cleaning catalyst. In a preferred embodiment the oxygen storage material comprises particles from a Ce/M1 mixed oxide solid solution coated with an oxide of another metal M2. Metal M1 e.g. can be calcium or zirconium while metal M2 most preferably is aluminum.