Gasoline Particle Filter Development

Gasoline particle filter (GPF) development includes optimization of multiple, competing targets: low backpressure, high clean filtration, acceptable strength, high oxygen storage capacity, small size, and low cost. A three-way catalyst + GPF system needs to meet targets for hydrocarbons, carbon monoxide, and nitrogen oxides in addition to particle mass and/or particle number. GPFs behave differently than diesel particle filters (DPFs) in terms of regeneration and ash loading behavior due to vastly different operating conditions. In a relatively clean exhaust condition on GDI relative to diesel, an empty GPF can have filtration efficiencies on the order of 60%. This was improved to 80–90% with a small amount of soot and/or ash on the filter walls, or higher catalyst washcoat loading. In the course of this work, models were developed to predict backpressure, filtration, and chemical performance.