Single-step flame-made Pt/MgAl2O4 - A NOx storage-reduction catalyst with unprecedented dynamic behavior and high thermal stability

One weight percentage of Pt/MgAl2O4, without any additional classical storage component (Ba or K), was synthesized by single-step flame spray pyrolysis. The catalyst consisting of nano-sized Pt dispersed on MgAl2O4 spinel showed superior dynamic performance in NO storage-reduction at short regeneration times (<30 s) compared to a standard 1%Pt-20%Ba/Al2O3 reference catalyst. The better NSR performance at short regeneration times of Pt/MgAl2O4 is limited to the use of hydrogen and H-2-CO mixtures as reductants, whereas with other reductants, CO or C3H6, the NSR performance was similar for both catalysts. The efficiency of the reduction agents decreased in the order H-2 > H-2 + CO > CO > C3H6. XRD and time-resolved in-situ DRIFT investigations indicate that bulk nitrate species are formed on Pt-Ba/Al2O3, whereas on the spinel-based Pt/MgAl2O4 catalyst predominantly surface species were formed. The superior dynamic performance of the spinel-based Pt/MgAl2O4 is attributed to the different adsorbed NOx species and their different stability under regeneration conditions. Pt/MgAl2O4 also showed higher thermal stability up to 800 degrees C and lower stability of sulfur-containing species. (C) 2010 Elsevier Inc. All rights reserved.