DENOX OF DIESEL ENGINE EXHAUST GASES USING A TEMPERATURE-CONTROLLED PRECATALYST FOR PROVIDING NO2 IN ACCORDANCE WITH THE REQUIREMENTS

摘要

Adherence to exhaust gas limit values for diesel vehicles requires removal of nitrogen oxides from exhaust gas. 'Active SCR process' is a preferred method. Nitrogen oxide conversions achieved by this process are particularly high when an optimal NO2/NOX ratio is set upstream of the SCR catalyst. The invention proposes a process which solves the problem of supplying NO2 in accordance with requirements by 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 can contain a nitrogen oxide storage material.