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

Authors: 
Büchel, R., ETH Zurich
Pratsinis, S. E., Swiss Federal Institute of Technology, Particle Technology Laboratory, ETH Zurich
Baiker, A., ETH Zurich


Fuel lean engines can increase the fuel efficiency of automobiles; however, produce more NOx that cannot be reduced with traditional three way catalysts. Therefore new catalysts have been developed like the NOx storage-reduction (NSR) catalysts that can store effluent NOx 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.