Rare earths based oxides as alternative materials to Ba in NOx-trap catalysts

The reduction of NOx from Diesel Engines is a major issue of automotive catalysis. In this paper, we investigate basic rare earths oxides (such as La2O3, Nd2O3 or Pr6O11) used as NOx-trap sites in replacement of Ba. These species are intimately mixed with (CeZr) solid solutions and the thus obtained mixed oxides are considered as Pt carrier. Investigations on powder model Pt-(CeZr)/RE2O3 (or Pr6O11) catalysts show promising results. These model catalysts present high NOx storage capacity, especially at low temperature, and improved resistance to sintering at 700 °C under lean hydrothermal conditions. Moreover, they show total desulfation at 600 °C i.e. 150 °C lower than current Pt-(BaO/Al2O3) technologies and are thus considered as more durable technologies.