Clean Technology 2008
R. Büchel, R. Strobel, S.E. Pratsinis, A. Baiker
ETH Zurich, CH
Platinum, catalysts, flame process, Lean NOx trap, LNT
A novel two-nozzle flame spray pyrolysis (FSP) process is presented for one-step preparation of Pt/Ba/Al2O3 particles for NOx storage-reduction (NSR) catalysts. These storage catalysts are of particular interest for mobile engines operating under lean conditions where traditional three way catalysts cannot be used for NOx abatement. According to the NSR concept, NOx is stored under lean conditions in the form of alkali or alkaline-earth nitrates (in particular Ba(NO3)2) and reduced over a noble metal into N2 during fuel rich periods. The use of two separated nozzles, one as aluminum and the other as a barium/platinum source, resulted in individual Al2O3 and BaCO3 nanoparticles, exhibiting good NOx storage activity. Furthermore this setup allowed to produce preferential deposition of Pt either on alumina or on the storage component BaCO3. Our studies on the effect of the preferential deposition of platinum on the alumina support or Ba storage component corroborate that the remote control of the different constituents is a crucial factor for high performance of NSR catalysts. Flame synthesis based on a two-nozzle system was shown to be a suitable tool for controlling the proximity of storage and reduction components in NSR catalysts.