With the introduction of limits for particle numbers besides particle mass emitted by light duty vehicles new pollution control devices like catalyzed gasoline particulate filters (GPF) might be required. GPFs need to address the challenge to provide sufficient particle number reduction at acceptable pressure drop in addition while having high conversion efficiencies for regulated pollutants.
The emission performance of gasoline particulate filters coated with a three-way functional washcoat was examined. The impact of the washcoat on particle filtration efficiency was investigated, as well as its impact on the conversion efficiencies for hydrocarbons, carbon monoxide and nitrous oxides. Moreover, it was found that the precious metal containing washcoat accelerates the regeneration of a filter when loaded with artificial soot.
In addition, an emission study was performed on exhaust systems comprising a three-way catalyst (TWC) on a flow through substrate and a gasoline particulate filter. The influence of precious metal distribution between TWC and GPF on hydrocarbon, carbon monoxide and nitrous oxides emissions will be discussed. With optimized distribution of precious metals between TWC and GPF tailpipe NOx emissions can be decreased substantially.
