Reduction of Nitrogen Oxides

The introduction of the Euro6 emission standards requires denitrification in addition to the reduction of diesel particulates. Tenneco has extensive experience in the reduction of nitrogen oxides (NOx) in exhaust aftertreatment. Currently, two technologies are used for passenger cars and commercial vehicles.

Lean nox trap: (LNT)
In a diesel oxidation catalyst, nitrogen monoxide (NO) will oxidize to nitrogen dioxide (NO2), which is stored as nitrate (e.g. Barium nitrate) in the coating in the downstream catalytic converter. When switching to rich operation, the NO is re-released and reduced to nitrogen (N2) in the vicinity of the coating component rhodium. In order to control this system NOx sensors and additional temperature sensors are needed.

Selective Catalytical Reduction (SCR)

In the SCR catalyst, NOx is continuously converted to nitrogen using ammonia in the presence of oxygen. Ammonia is obtained from urea injected directly into the exhaust system as a urea-water solution.

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SCR scheme

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