The NOx storage reduction (NSR) process is commonly envisaged for the NOx treatment of exhaust gas from lean-burn engine vehicles. NOx are firstly stored on the catalyst, which is periodically submitted to a reducing mixture for few seconds in order to reduce the stored NOx into N2. The on-board reducer is coming from the gasoline/Diesel fuel and, in fact, the NSR catalyst is submitted to a mixture of hydrocarbons, CO and H2 with various compositions depending on the lean/rich step. In this study, the influence of each reducer (C3H6, CO and H2) is evaluated separately, with a special consideration to the N2O selectivity. It is demonstrated that the N2O can be emitted during both lean and rich periods, with varying ratio depending on the considered reducer and the temperature of gas. For instance, at 300°C, a high N2O selectivity is observed when C3H6 is used, and near half of the N2O emission occurs during the storage phase in lean condition.
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 La 2 O 3 , Nd 2 O 3 or Pr 6 O 11 ) 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)/RE 2 O 3 (or Pr 6 O 11 ) 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/Al 2 O 3 ) technologies and are thus considered as more durable technologies.
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