Analysis of the Emission Conversion Performance of Gasoline Particulate Filters Over Lifetime

Gasoline particulate filters (GPF) recently entered the market, and are already regarded a state-of-the-art solution for gasoline exhaust aftertreatment systems to enable EU6d-TEMP fulfilment and beyond. Especially for coated GPF applications, the prognosis of the emission conversion performance over lifetime poses an ambitious challenge, which significantly influences future catalyst diagnosis calibrations. The paper presents key-findings for the different GPF application variants. In the first part, experimental GPF ash loading results are presented. Ash accumulates as thin wall layers and short plugs, but does not penetrate into the wall. However, it suppresses deep bed filtration of soot, initially decreasing the soot-loaded backpressure. For the emission calibration, the non-linear backpressure development complicates the soot load monitoring, eventually leading to compromises between high safety against soot overloading and a low number of active regenerations. In the second part, a relevant share of ash deposits inside three-way catalysts (TWC) is depicted. In an experiment, the oxygen storage capacity (OSC) of a three-way catalyst was significantly lowered by ash, while a coated GPF showed little effects. A subsequent OSC regeneration of the TWC showed that the OSC drop is not necessarily permanent, reducing the selectivity between full useful life and borderline catalysts.