(318a) Two-Nozzle Flame Synthesis of NOx Storage Reduction Catalysts

Fuel lean engines can increase the fuel efficiency of automobiles; however, produce more NOx that cannot be reduced with traditional three way catalysts (TWC) as of the excess oxygen [1]. New catalyst as for example the NOx storage-reduction (NSR) catalyst can store effluent NOx in the form of metal nitrates which need to be regenerated periodically [2]. Such catalysts can be produced with a two-nozzle flame spray pyrolysis (FSP) system [3] whereby the material composition of the storage material and support can be precisely controlled and varied [4]. As storage material Ba, K and Mg were tested and as support Al2O3, MnO2, TiO2, Al2MgO4 and ZrO2 and CeO2 have been investigated so far and characterized by XRD, BET and CO chemisorption [5]. Different material combination give advantage for specific applications as for low or high temperature application or better stability against poisons as for example sulfur [6].

Additionally the location of the Pt on the support (e.g. Al2O3) or on the storage material (e.g. Ba) [7] can be adjusted with the two FSP setup allowing to investigate the support and the spillover effect during NSR catalysis [8]. The different Pt sites were elucidated by electron microscopy techniques. NSR behavior of these catalysts as well as of sequential setups of catalytic beds was investigated in a microreactor by switching between lean and rich conditions. The preferential deposition of platinum on the alumina support or Ba storage component corroborate that location of the Pt defines the performance of NSR catalysts. Various support elements can limit NSR activity, however, Pt directly deposited on BaCO3 increases the regeneration of the catalysts and is therefore better for long run experiments.

References:

[1] S. Matsumoto, Catal. Today 90 (2004) 183-190.

[2] N. Miyoshi, S. Matsumoto, K. Katoh, T. Tanaka, J. Harada, N. Takahashi, K. Yokota, M. Sugiura, K. Kasahara, SAE Technical Paper 950809 (1995)

[3] R. Strobel, M. Maciejewski, S.E. Pratsinis, A. Baiker, Thermochim. Acta 445 (2006) 23-26.

[4] T.J. Patey, R. Buchel, S.H. Ng, F. Krumeich, S.E. Pratsinis, P. Novak, 189 (2009) 149-154.

[5] R. Strobel, F. Krumeich, S.E. Pratsinis, A. Baiker, J. Catal. 243 (2006) 229-238.

[6] N. Takahashi, A. Suda, I. Hachisuka, M. Sugiura, H. Sobukawa, H. Shinjoh, Appl. Catal., B 72 (2007) 187-195.

[7] M.O. Symalla, A. Drochner, H. Vogel, R. Büchel, S.E. Pratsinis, A. Baiker, Appl. Catal., B 89 (2009) 41-48.

[8] R. Büchel, R. Strobel, F. Krumeich, A. Baiker, S.E. Pratsinis, J. Catal. 261 (2009) 201-207.