Ocampo, F., Harle, V., Ohtake, N., Rohe, R. et al., "Innovative Hybrid Rare Earth and Barium Materials with Enhanced Properties for NOx Storage Applications," SAE Int. J. Engines 8(3):1136-1143, 2015, doi:10.4271/2015-01-0988.
The reduction of NOx to meet current diesel regulation standards has been achieved using two main technologies named NH3-SCR and LNT. In the forthcoming years, the implementation of new and colder test cycles such as “real driving emissions” (RDE), combined with CO2 targets (95 g/km is 2020 target in Europe) will require higher NOx storage capacity (NSC) in the low temperature region (120-350°C). On the other hand, lean-burn Gasoline vehicles, emitting exhaust gases at higher temperatures, will require improved NSC over a broader temperature range (200-500°C). Therefore, the development of more efficient NSC materials is an area of extensive study by original equipment manufacturers (OEMs), catalysts manufacturers, and raw materials suppliers. Today, ceria is a key component in the formulation of active NSC washcoats. It is often combined with barium in order to improve its high temperature NSC, but this also leads to a significant loss of specific surface area and thus a decrease in overall performance at low temperature. This paper reports recent progress made on NSC materials, with the aim to enlarge their operational temperature window. In this regard, Solvay has developed an innovative solution: rare earth and barium hybrid compounds as advanced NSC materials. synthetic gas bench tests performed on powder model catalysts show a significant increase in NSC at low temperatures and a very strong benefit in NSC at high temperatures, compared to current Solvay reference ‘High Stability Ceria’ or Ba-doped ceria.