Abstract: A process which solves the problem of supplying NO2 in accordance with requirements by means of temperature control of the precatalyst which is decoupled from the operating state of the engine. In an associated apparatus, a precatalyst which contains at least one oxidation component and whose temperature can be controlled independently of the operating state of the engine and an active SCR stage comprising an SCR catalyst with upstream metering facility for a reducing agent from an external source are arranged in series. A particle filter can be arranged between precatalyst and metering facility. The precatalyst preferably additionally contains a nitrogen oxide storage material.

Abstract: The adherence to future legally obligatory exhaust gas limit values for diesel vehicles in Europe, North America and Japan requires not only the removal of particles but also effective removal of nitrogen oxides from the exhaust gas (‘deNOx’). The ‘active SCR process’ is the preferred method for this. The nitrogen oxide conversions achieved by means of this process are particularly high when an optimal NO2/NOx ratio, preferably 0.5, is set upstream of the SCR catalyst. The invention proposes a process which solves the problem of supplying NO2 in accordance with requirements by means of temperature control of the precatalyst which is decoupled from the operating state of the engine.

Abstract: A process which solves the problem of supplying NO2 in accordance with requirements by means of temperature control of the precatalyst which is decoupled from the operating state of the engine. In an associated apparatus, a precatalyst which contains at least one oxidation component and whose temperature can be controlled independently of the operating state of the engine and an active SCR stage comprising an SCR catalyst with upstream metering facility for a reducing agent from an external source are arranged in series. A particle filter can be arranged between precatalyst and metering facility. The precatalyst preferably additionally contains a nitrogen oxide storage material.

Abstract: The reductive removal of nitrogen oxides from the exhaust gas from internal combustion engines operated predominantly under lean conditionstakes place in a selective catalytic reduction (SCR) of the nitrogen oxides by means of ammonia or a compound which can be decomposed into ammonia as reducing agent. Conventional SCR catalysts typically have a relatively narrow working temperature window, usually 350° C. to 520° C., in which good nitrogen oxide conversions can be achieved with sufficient selectivity. SCR catalyst formulations whose working window is in the temperature range from 150° C. to 350° C. generally not be used at higher temperatures since they oxidize the ammonia required as reducing 18 agent to nitrogen oxides at above 350° C. To cover the entire exhaust gas temperature range typical of vehicles having been operating internal combustion enginesextending from 200° C. to 600° C.

Abstract: Selective catalytic reduction with ammonia or a compound that decomposes to ammonia is a known method for the removal of nitrogen oxides from the exhaust gas of primarily lean-burn internal combustion engines. The vanadium-containing SCR catalysts that have long been generally used for this are characterized by a good conversion profile. However, the volatility of vanadium oxide can, at higher exhaust gas temperatures, lead to the emission of toxic vanadium compounds. Zeolite-based SCR catalysts, which are used in particular in discontinuous SCR systems, constitute a very cost-intensive solution for the problem. A method is proposed by which a homogeneous cerium-zirconium mixed oxide is activated for the SCR reaction in a defined manner by the introduction of sulphur and/or transition metal.

Abstract: The invention relates to a special device for the purification of diesel exhaust gases, which device comprises, in the flow direction of the exhaust gas, an oxidation catalyst, a diesel particle filter with catalytically active coating, and, downstream of a device for introducing a reducing agent from an external reducing agent source, an SCR catalyst. The oxidation catalyst and the catalytically active coating of the diesel particle filter contain palladium and platinum. The ratio of the noble metals platinum and palladium in the overall system and on the individual components, oxidation catalyst and catalytically coated diesel particle filter, are coordinated with one another in such a way as to obtain firstly an optimum NO/NO2 ratio in the exhaust gas upstream of the downstream SCR catalyst, and secondly optimum heating and HC conversion behaviour during an active particle filter regeneration.

Abstract: The present invention relates to a process for purifying NOx-containing exhaust gases formed in an internal combustion engine. In particular, the invention is directed at the purification of exhaust gases from an engine which produces a lean-burn exhaust gas, e.g. a diesel engine or a spark-ignition engine operated under lean conditions. Furthermore, the present invention relates to an appropriately equipped exhaust gas purification apparatus. The apparatus proposes a sequence of different catalysts for purifying primary axhaust gas of lean-burn engines, in which an oxidatively active particle filter (1) is followed by an oxidation catalyst (2) and this is in turn followed by an SCR catalyst, (3c) with the latter being arranged downstream of an addition of reducing agent (3a) located downstream of the oxidation catalyst (2).

Abstract: The adherence to future legally obligatory exhaust gas limit values for diesel vehicles in Europe, North America and Japan requires not only the removal of particles but also effective removal of nitrogen oxides from the exhaust gas (‘deNOx’). The ‘active SCR process’ is the preferred method for this. The nitrogen oxide conversions achieved by means of this process are particularly high when an optimal NO2/NOx ratio, preferably 0.5, is set upstream of the SCR catalyst. The invention proposes a process which solves the problem of supplying NO2 in accordance with requirements by means of temperature control of the precatalyst which is decoupled from the operating state of the engine.

Abstract: The invention relates to a special device for the purification of diesel exhaust gases, which device comprises, in the flow direction of the exhaust gas, an oxidation catalyst, a diesel particle filter with catalytically active coating, and, downstream of a device for introducing a reducing agent from an external reducing agent source, an SCR catalyst. The oxidation catalyst and the catalytically active coating of the diesel particle filter contain palladium and platinum. The ratio of the noble metals platinum and palladium in the overall system and on the individual components, oxidation catalyst and catalytically coated diesel particle filter, are coordinated with one another in such a way as to obtain firstly an optimum NO/NO2 ratio in the exhaust gas upstream of the downstream SCR catalyst, and secondly optimum heating and HC conversion behaviour during an active particle filter regeneration.

Abstract: The reductive removal of nitrogen oxides from the exhaust gas from internal combustion engines operated predominantly under lean conditions takes place in a selective catalytic reduction (SCR) of the nitrogen oxides by means of ammonia or a compound which can be decomposed into ammonia as reducing agent. Conventional SCR catalysts typically have a relatively narrow working temperature window, usually 350° C. to 520° C., in which good nitrogen oxide conversions can be achieved with sufficient selectivity. SCR catalyst formulations whose working window is in the temperature range from 150° C. to 350° C. generally not be used at higher temperatures since they oxidize the ammonia required as reducing 18 agent to nitrogen oxides at above 350° C. To cover the entire exhaust gas temperature range typical of vehicles having been operating internal combustion engines extending from 200° C. to 600° C.

Abstract: In exhaust gas purification units for decreasing nitrogen oxides in lean-burn exhaust gas of internal combustion engines by selective catalytic reduction by means of ammonia, introduction of excess ammonia leads to undesirable emissions of unused ammonia. These emissions can be decreased by means of ammonia barrier catalysts. In the ideal case, ammonia is oxidized to nitrogen and water by these catalysts. These require additional space in the exhaust gas purification unit which may have to be taken away from the space provided for the SCR main catalyst. In addition, the use of such ammonia barrier catalysts can result in overoxidation of the ammonia to nitrogen oxides. To overcome these disadvantages, a catalyst containing two superposed layers is proposed for the removal of nitrogen-containing pollutant gases from diesel exhaust gas. The lower layer contains an oxidation catalyst and the upper layer can store at least 20 milliliters of ammonia per gram of catalyst material.

Abstract: Selective catalytic reduction with ammonia or a compound that decomposes to ammonia is a known method for the removal of nitrogen oxides from the exhaust gas of primarily lean-burn internal combustion engines. The vanadium-containing SCR catalysts that have long been generally used for this are characterized by a good conversion profile. However, the volatility of vanadium oxide can, at higher exhaust gas temperatures, lead to the emission of toxic vanadium compounds. Zeolite-based SCR catalysts, which are used in particular in discontinuous SCR systems, constitute a very cost-intensive solution for the problem. A method is proposed by which a homogeneous cerium-zirconium mixed oxide is activated for the SCR reaction in a defined manner by the introduction of sulphur and/or transition metal.

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: Structured automotive catalysts which comprise a plurality of different catalytically active coatings arranged above one another on a support body and whose coatings contain transition metals and porous support materials are well known. Structured automotive catalysts of this type which do not belong to the group of three-way catalysts, in particular, frequently display large selectivity losses after thermal aging processes which can be attributed to the thermally induced migration of transition metal atoms from one layer into the neighbouring coating.

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: 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: 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: 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: A starter catalyst for the purification of the exhaust gases from internal combustion engines, which include palladium on aluminum oxide and of barium oxide, as well as a process for its production. The barium oxide and palladium are together deposited in a finely divided state on the supporting material aluminum oxide and the average particle size of the palladium crystallites is between 3 and 7 nm. The small crystallite size of palladium and the barium oxide likewise deposited in finely divided state on the supporting material impart to the catalyst a high activity and long-term stability to high temperature stresses.

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.