US Patent 7856809 Exhaust gas post treatment system

An exhaust gas post treatment system for nitrogen oxide and particle reduction of internal combustion engines operated with excess air, comprising a particle filter disposed in the exhaust gas stream of the internal combustion engine. The particle filter is a surface-type particle filter or a deep bed filter, and is charged on an outlet side with an SCR-active catalyst material for reducing nitrogen oxides. Ammonia or an ammonia-releasing reduction agent is supplied to the exhaust gas stream upstream of the particle filter.