Nanostructured catalysts for automotive exhaust treatment

To reduce NOx emissions in car exhaust new and better catalysts are being developed, among them the NOx storage reduction (NSR) catalysts. These NSR catalysts have the ability to store NOx inside the catalyst material in the form of metal-nitrates. For this storage materials like Ba or K are typically used. The storage material and a noble metal (e.g. Pt, Pd, Rh) are deposited on a support material (e.g. Al2O3 or CeO2).
With two nozzles FSP the location of the noble metal can be controlled, such that the noble metal is either deposited on the support or on the storage material [1]. The spillover distance and the surrounding of the catalysts influences the catalysts performance, for example direct contact of Pt to CeO2 will limit the propene reduction to temperatures above 350 °C [2]. A close contact of the noble metal to the storage material is preferred especially for the regeneration of NOx storage catalysts [1]. The effect of storage material type was investigated: Pure BaCO3 was not very effective, only the addition of Pt increased the storage capacity [3] while flame made K proved to have high storage capacity even at low temperatures [4].

With the two nozzle FSP also combinations of different noble metals, like Pt-Pd, and selective deposition on support or storage material [5] can be made. For the Rh-Pt system this helped to improve the tolerance against sulfur poisoning [6].

Recent relevant publications:

1. R. Büchel, R. Strobel, F. Krumeich, A. Baiker, S.E. Pratsinis, "Influence of Pt location on BaCO3 or Al2O3 during NOx storage reduction", Journal of Catalysis, 261, 201-207 (2009)
2. R. Büchel, R. Strobel, A. Baiker, S.E. Pratsinis, "Effect of the Proximity of Pt to Ce or Ba in Pt/Ba/CeO2 Catalysts on NOx Storage–Reduction Performance", Topics in Catalysis, 52, 1709-1712 (2009)
3. M.O. Symalla, A. Drochner, H. Vogel, R. Büchel, S.E. Pratsinis, A. Baiker, "Structure and NOx storage behaviour of flame-made BaCO3 and Pt/BaCO3 nanoparticles", Applied Catalysis B: Environmental, 89, 41-48 (2009)
4. R. Büchel, R. Strobel, A. Baiker, S.E. Pratsinis, "Flame-Made Pt/K/Al2O3 for NOx Storage–Reduction (NSR) Catalysts", Topics in Catalysis, 52, 1799-1802 (2009)
5. R. Büchel, S.E. Pratsinis, A. Baiker, "Influence of controlled spatial deposition of Pt and Pd in NOx storage-reduction catalysts on their efficiency" Appl.Catal.B:Environ., 101, 682-689 (2011)
6. R. Büchel, S.E. Pratsinis, A. Baiker, "Mono- and bimetallic Rh and Pt NSR-catalysts prepared by controlled deposition of noble metals on support or storage component", Applied Catalysis B-Environmental, 113, 160-171 (2012)