Catalytic engine exhaust gas treatment - with second oxidation catalyst before reduction catalyst and secondary air admission after it

摘要

The exhaust gases of an IC engine pass through an oxidn. catalyst to oxidize part of the hydrocarbons and CO and to reduce the O2 content before entering a redn. catalyst where the N oxides are reduced. A final oxidn. catalyst stage to oxidize the hydrocarbons and CO follows after secondary air has been admitted from a blower. This prevents premature brittle fracture of the redn. catalyst when exposed to a high temp. in presence of oxygen. The system prevents pollution of the atmos. both by N oxides, CO and hydrocarbons.