(629ar) Two-Nozzle Flame Synthesis of NOx Storage Reduction Catalysts

Fuel lean engines can increase the fuel efficiency of automobiles; however, produce more NO_x that cannot be reduced with traditional three way catalysts. Therefore new catalysts have been developed like the NO_x storage-reduction (NSR) catalysts that can store effluent NO_x in the form of a metal nitrate which is regenerated periodically. With a two-nozzle flame spray pyrolysis (FSP) system [1] highly efficient NSR catalysts can be made. Here we present the synthesis of a ternary catalyst consisting of Pt, BaCO₃ and Al₂O₃ whereby the location of the noble metal Pt is precisely controlled: So Pt could be selectively deposited on the support (Al₂O₃) or on the storage material (BaCO₃) allowing to investigate the support and the spillover effect during NSR catalysis [2]. With scanning electron microscopy (STEM) combined with Energy-dispersive X-ray spectroscopy (EDX) the successful control on the Pt location is proven. NSR behavior of these catalysts as well as of sequential setups of catalytic beds was investigated in a micro reactor by switching between lean and rich conditions. The preferential deposition of Pt on the Al₂O₃ support or BaCO₃ 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 the long run.  The powders were characterized by XRD, BET, TEM, DRIFTS and CO chemisorptions.

References:

[1]        R. Strobel, S.E. Pratsinis, A. Baiker, J. Mater. Chem. 15 (2005) 605.

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