Silver-modified perovskites as soot oxidation catalysts for Gasoline Particulate Filters
Résumé
European standards for Diesel cars restrict the particulate matter emissions by combining a limit number (PN: 6.0×1011 particulates/km) with a limit mass (PM: 4.5 mg/km) as well as durability of after-treatment system. From 2014, PN and PM limits are also introduced for the approval of gasoline-fuelled vehicles. While conventional Port Fuel Injection (PFI) gasoline vehicles can easily comply with these limits, their Direct Injection (GDI) counterparts are found to emit systematically above this threshold by up to 1.5 orders of magnitude [1,2]. The Euro 6b legislations will tolerate a PN limit at 6.0×1012 particulates/km for these GDI vehicles but this standard will be strengthened from 2017 (Euro 6c) to reach the level of Diesel cars. It is therefore expected that GDI vehicles may require the installation of Gasoline Particulate Filters (GPF). At the same time, the penetration of GDI vehicles is expected to rapidly grow in the near future in both the European and the US markets. This is due to their improved fuel efficiency compared to the conventional PFIs as well as their ability to be implemented in hydride cars. Therefore, it is of strong interest to develop catalysts for the regeneration of GPF. Comparing to Diesel ones, GDI exhausts contain much lower amounts of oxygen. The scientific issue consists in the development of catalysts effective for soot oxidation at low oxygen levels. For cost and sustainability reasons, it is also necessary to avoid the utilization of noble metals. This study examines the use of Ag-modified manganites and ferrites as soot oxidation catalysts for GPF.