Abstract: A process for reducing the nitrogen oxides present in a lean exhaust gas from an internal combustion engine by selective catalytic reduction on a reduction catalyst using ammonia, wherein a fraction of the nitrogen monoxide present in the exhaust gas is oxidized to nitrogen dioxide before the exhaust gas, together with ammonia, is passed over the reduction catalyst. The reduction catalyst contains a zeolite exchanged with transition metals and oxidation of the nitrogen monoxide is performed in such a way that the exhaust gas contains 30 to 70 vol. % of nitrogen dioxide before contact with the reduction catalyst.

Abstract: The invention relates to a method for desulfating a nitrogen oxide storage catalyst that contains stored nitrogen oxides and sulfur oxides and that forms part of an exhaust gas purification system of a lean-burn engine. The method provides that, to initiate desulfation, the temperature of the catalyst is increased to the point where thermal desorption of the nitrogen oxides stored in the catalyst sets in, and the onset of thermal desorption of the nitrogen oxides is used as the signal to enrich the air/fuel mixture to perform the desulfation.

Abstract: A process for reducing the nitrogen oxides present in a lean exhaust gas from an internal combustion engine by selective catalytic reduction on a reduction catalyst using ammonia, wherein a fraction of the nitrogen monoxide present in the exhaust gas is oxidized to nitrogen dioxide before the exhaust gas, together with ammonia, is passed over the reduction catalyst. The reduction catalyst contains a zeolite exchanged with transition metals and oxidation of the nitrogen monoxide is performed in such a way that the exhaust gas contains 30 to 70 vol. % of nitrogen dioxide before contact with the reduction catalyst.

Abstract: A method for removing nitrogen oxides and particulate matter from the lean exhaust gas of a combustion engine that also contains low concentrations of sulfur oxides. The exhaust gas stream is passed over a nitrogen oxide storage catalyst and a particulate filter, where nitrogen oxides and sulfur oxides are adsorbed by the storage catalyst under lean exhaust gas conditions and the particulate matter is deposited on the particulate filter. The storage catalyst is in a first cycle is periodically denitrated by enriching the exhaust gas regeneration of the particulate filter. Desulfurization of the nitrogen oxide storage catalyst is carried out in a second cycle by raising the temperature of the lean exhaust gas to a value at which the particulate matter combustion on the particulate filter is initiated and then the storage catalyst can be desulfurized by enriching the exhaust gas.

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: A process for reducing the nitrogen oxides present in a lean exhaust gas from an internal combustion engine by selective catalytic reduction on a reduction catalyst using ammonia, wherein a fraction of the nitrogen monoxide present in the exhaust gas is oxidized to nitrogen dioxide before the exhaust gas, together with ammonia, is passed over the reduction catalyst. The reduction catalyst contains a zeolite exchanged with transition metals and oxidation of the nitrogen monoxide is performed in such a way that the exhaust gas contains 30 to 70 vol. % of nitrogen dioxide before contact with the reduction catalyst.

Abstract: The invention provides a redox catalyst for the selective reduction of the nitrogen oxides present in exhaust gas from diesel engines using ammonia. The reduction catalyst contains a catalytically active material which is based on the solid acid system TiO2/WO3/MoO3V2O5/SiO2/SO3 and an oxidation catalyst based on the platinum group metals platinum and palladium. The reduction catalyst is present in the form of a cylindrical honeycomb catalyst with an inlet and an outlet end face. The oxidation catalyst is applied to a section of the reduction catalyst adjacent to the outlet end face. The redox catalyst is characterised in that the catalytically active material in the reduction catalyst is used as support material for the platinum group metals in the oxidation catalyst.

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 invention relates to a method for desulfating a nitrogen oxide storage catalyst that contains stored nitrogen oxides and sulfur oxides and that forms part of an exhaust gas purification system of a lean-burn engine. The method provides that, to initiate desulfation, the temperature of the catalyst is increased to the point where thermal desorption of the nitrogen oxides stored in the catalyst sets in, and the onset of thermal desorption of the nitrogen oxides is used as the signal to enrich the air/fuel mixture to perform the desulfation.

Abstract: A process for checking the operability of an exhaust gas purification catalyst for diesel engines, which has a light-off temperature and a degree of conversion rCO for carbon monoxide (CO), by direct measurement of the carbon monoxide concentration in combination with a temperature measurement. To evaluate the remaining catalytic activity of the catalyst the difference &Dgr;T between the current catalyst exit temperature TE of the exhaust gas and the light-off temperature TCO,50%,fresh of the fresh catalyst for carbon monoxide stored as a function of the speed and load &Dgr;T=TE−TCO,50%,fresh is determined and the degree of conversion rCO for carbon monoxide is ascertained.

Abstract: The present invention provides an exhaust gas treatment unit for an internal combustion engine. A first catalyst unit produces ammonia from corresponding constituents in a rich exhaust gas composition. A second catalyst unit that is located downstream of the first catalyst unit temporarily stores the ammonia produced by the first catalyst unit in the presence of a rich exhaust gas composition. In the presence of a lean exhaust gas composition, the nitrogen oxides present in the exhaust gas are subjected to a reduction reaction using the temporarily stored ammonia as reducing agent. The exhaust gas treatment unit also contains a third catalyst unit that is located between the other two catalyst units, and oxidizes the nitrogen oxides present in the exhaust gas at lean exhaust gas conditions to a such an extent that 25 to 75 vol. % of the nitrogen oxides entering the second catalyst unit consist of nitrogen dioxide.

Abstract: The invention provides a process for reducing the amounts of carbon monoxide, hydrocarbons and soot particles in the lean exhaust gas from an internal combustion engine using a particle filter, wherein the soot particles have a soot ignition temperature TZ and the particle filter is regenerated from time to time by raising the temperature of the particle filter to above the soot ignition temperature and burning the soot particles, wherein the temperature of the filter is increased to the temperature required to initiate soot ignition by burning additional fuel on the catalytic coating when the exhaust gas back pressure reaches a predetermined value. The process is characterised in that the particle filter is provided with a catalytic coating comprising a first group of components for reducing the ignition temperature of soot, said first group of components contains at least one oxygen storage component and at least one platinum group metal selected from the group consisting of platinum, palladium and rhodium.

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 bum-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: A structured catalyst for selective reduction of nitrogen oxides with ammonia using an ammonia-supplying compound. The catalyst is preferably used for exhaust gas treatment of diesel vehicles powered by diesel motors. The catalyst is characterized by the fact that it contains a reduction catalyst for selective reduction of nitrogen oxides with ammonia and a hydrolysis catalyst for the hydrolysis of urea, where the hydrolysis catalyst is applied in the form of a coating onto the reduction catalyst. By this arrangement of the two catalytic functions in one catalyst the exhaust gas system can be made very compactly and space saving. Moreover, advantageous synergistic effects result from the direct contact of the hydrolysis catalyst and the reduction catalyst.

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: A honeycomb body made from a ceramic material with improved radial pressure resistance that is of cylindrical shape and features a first and a second end face and a cylindrical shell and that is traversed from one end face to the other by axially parallel channels formed by channel walls and distributed across the cross section of the honeycomb body in a regular grid pattern, in which design an outer marginal zone of the honeycomb body, the thickness of which amounts to several channel diameters, encloses a central area. The increase in radial pressure resistance of the honeycomb body is achieved by reinforcing the ceramic material of the cylindrical shell and of the channel walls in the outer marginal zone of the honeycomb body by depositing on or in it one or several inorganic substances for the purpose of increasing its mechanical stability.

Abstract: The present invention is directed to the removal of soot particles from the exhaust of a diesel engine. A device is provided that comprises a wall-flow filter having inflow channels and outflow channels, which are connected by pores. Preferably the inflow channels and outflow channels are alternately closed on opposite sides. The flow channels that are closed on the outflow side form the inflow channels and the flow channels that are closed on the inflow side form the outflow channels of the filter. In the inflow channels and/or the outflow channels of the filter, exhaust treatment structures are provided. The walls of the flow channels, as well as the exhaust treatment structures, are preferably coated with a catalyst layer. Since the exhaust does not need to flow through these exhaust treatment structures, the catalyst deposited thereon is not covered by soot. The filter function and the catalytic function of the catalyst layer on the exhaust treatment structures are thus largely separated from one another.

Abstract: The present invention provides a process for regenerating the catalytic activity of catalysts that have oxidizing functions. A catalyst that is located in the exhaust gas line of a diesel engine that preferably contains a catalytically active coating on a honeycomb carrier that does not have a filter function and that has at least one oxidizing function is regenerated. As a result of time-restricted increases in the exhaust gas temperature upstream of the catalyst to a value greater than 450° C., the combustion of soot particles and hydrocarbons deposited on the catalyst is initiated, and thus, the catalytic activity of the catalyst is at least partly regenerated.

Abstract: The invention relates to a high performance catalyst containing a layer on an inert carrier body comprising noble metals from the platinum group deposited on support materials. The catalyst is characterised in that, the layer comprises platinum deposited in a washcoat consisting of Al2O3 which is stabilized with lanthana (La2O3), ceria (CeO2), which is stabilized with zirconia (ZrO2) and praseodymium (Pr6O11). The supprot is promoted by sulfur-containing compounds which come from at least one of following compounds: platinum sulfite (PtSO3), sulfuric acid (H2SO4), ammonium sulfate ((NH4)2SO4), titanium oxysulfate (TiOSO4), titanium sulfate (Ti2(SO4)3), and zirconium sulfate (Zr(SO4)2).

Abstract: A catalyst for purifying the exhaust gases of diesel engines, which catalyst contains at least one zeolite and, additionally, at least one of the support oxides aluminum oxide, silicon dioxide, titanium dioxide and aluminum silicate and at least one of the noble metals platinum, palladium, rhodium and iridium. In this catalyst the atoms of the noble metals have a mean oxidation number of less than +2.5, on average more than 3 metal ligands and less than 3 oxygen ligands and are present on the zeolites and support oxides in the form of crystallites having a mean particle size of from 1 to 6 nm.