Abstract: A process for preparing acrylic acid, in which heterogeneously catalyzed gas phase partial oxidation of at least one C3 precursor of acrylic acid with molecular oxygen over catalysts in the solid state of matter at elevated temperature affords a product gas mixture comprising acrylic acid, water vapor and secondary components, then the product gas mixture is directed into a condensation column equipped with separating internals, the product gas mixture is allowed to ascend into itself within the condensation column and undergoes fractional condensation, separating the product gas mixture into a bottoms liquid comprising conversion products and secondary components that are higher-boiling than acrylic acid, a crude acrylic acid comprising water and secondary components that have been depleted overall as target product, an acid water still comprising acrylic acid and secondary components, and a residual gas mixture comprising secondary components that are lower-boiling than water, the target product is conducte

Abstract: The invention relates to a catalyst comprising a small-pore zeolite that contains iron and copper and has a maximum ring size of eight tetrahedral atoms, characterized in that the channel width of the small-pore zeolite amounts to >3.8 ? (0.38 nm) in at least one dimension.

Abstract: The invention relates to a catalyst comprising a small-pore zeolite that contains iron and copper and has a maximum ring size of eight tetrahedral atoms, characterized in that the channel width of the small-pore zeolite amounts to >3.8 ? (0.38 nm) in at least one dimension.

Abstract: The present invention is directed to a process for the production of supported transition metals with high dispersion. The latter are deposited onto refractory oxides without using a further liquid solvent. Hence, according to this dry procedure no solvent is involved which obviates certain drawbacks connected with wet ion exchange, impregnation or other metal addition processes known in the art.

Abstract: A stream of exhaust gases from the combustion of hydrocarbon-containing fuels with a variable temperature can be produced by dividing the exhaust gases into two separate part-streams, cooling one part-stream and then combining the two part-streams again. The temperature of the exhaust-gas stream which has been combined again can be set to between the temperature of the combustion of the hydrocarbon-containing fuels and the temperature of the cooled exhaust-gas part-stream by corresponding throttling of the two part-streams before they are brought together again. The exhaust-gas stream produced in this way is preferably used for the defined ageing of automotive exhaust catalysts. In this context, it is particularly advantageous that the change in the temperature of the exhaust-gas stream has no influence on its air/fuel ratio.

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: The invention describes a method for determining the light-off temperature of a catalytic converter on board a vehicle. The aging condition of the catalytic converter is determined by means of the method. To test the catalytic converter, the latter is loaded for example with a CO/HC test pulse. During the combustion of the additional CO and HC on the catalytic converter, an axial temperature profile is generated. The position of the maximum of said temperature profile along the catalytic converter is dependent on the current light-off temperature. The temperature profile travels through the catalytic converter and can be measured at the outlet of the catalytic converter as a time-dependent profile. The original axial temperature profile can be inferred from the time-dependent profile. Using a calculation program, the current light-off temperature of the catalytic converter on the vehicle can be determined.

Abstract: The present invention relates to a method for purifying the exhaust gases of an internal combustion engine having a catalytic converter which comprises oxygen storage components. The invention is concerned particularly with the restoration of the optimum filling degree of the oxygen storage components for regulated stoichiometric operation after the engine has been operated under lean conditions for a relatively short or relatively long period of time.

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: A cost effective process is presented for carrying out catalytic, in particular also exothermic, endothermic or autothermal reactions with optimum yield and selectivity. The system used is a wall-flow monolith which forces a flow from the inlet channel through the porous wall into the outlet channel by reciprocal closure of the gas channels. This is operated such that mass transfer and heat transport are determined virtually exclusively by convection, and diffusion-related thermal conduction phenomena can be neglected.

Abstract: The invention describes a method for determining the light-off temperature of a catalytic converter on board a vehicle. The aging condition of the catalytic converter is determined by means of the method. To test the catalytic converter, the latter is loaded for example with a CO/HC test pulse. During the combustion of the additional CO and HC on the catalytic converter, an axial temperature profile is generated. The position of the maximum of said temperature profile along the catalytic converter is dependent on the current light-off temperature. The temperature profile travels through the catalytic converter and can be measured at the outlet of the catalytic converter as a time-dependent profile. The original axial temperature profile can be inferred from the time-dependent profile. Using a calculation program, the current light-off temperature of the catalytic converter on the vehicle can be determined.

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: 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: 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: 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: The present invention relates to the catalytic conversion of hydrocarbons for generating a gas that is rich in hydrogen, to the use of said apparatus and to a process for generating hydrogen. The apparatus comprises a reforming catalyst (5), as well as a means (8) for supplying hydrocarbons to the catalyst. The reforming catalyst is arranged in an exhaust pipe (3) through which the exhaust gases of combustion processes are passed.

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: A stream of exhaust gases from the combustion of hydrocarbon-containing fuels with a variable temperature can be produced by dividing the exhaust gases into two separate part-streams, cooling one part-stream and then combining the two part-streams again. The temperature of the exhaust-gas stream which has been combined again can be set to between the temperature of the combustion of the hydrocarbon-containing fuels and the temperature of the cooled exhaust-gas part-stream by corresponding throttling of the two part-streams before they are brought together again. The exhaust-gas stream produced in this way is preferably used for the defined ageing of automotive exhaust catalysts. In this context, it is particularly advantageous that the change in the temperature of the exhaust-gas stream has no influence on its air/fuel ratio.

Abstract: An exhaust gas treatment unit for the selective catalytic reduction of nitrogen oxides under lean exhaust gas conditions which contains at least one catalyst with catalytically active components for selective catalytic reduction (SCR components). The exhaust gas treatment unit is characterised in that the catalyst also contains, in addition to SCR components, at least one storage component for nitrogen oxides (NOx components).

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.