Effect of the Proximity of Pt to Ce or Ba in Pt/Ba/CeO2 Catalysts on NOx Storage-Reduction Performance

The effect of Pt location in Pt/Ba/CeO2 catalysts for NOx storage-reduction (NSR) was analyzed. The Pt location on BaCO3 or CeO2 support was controlled by changing the angle (phi) between the two flame sprays producing these two components. As-prepared flame-made catalysts contain PtOx which must be reduced during the fuel rich phase to become active for NOx storage and reduction of NOx. For Pt on BaCO3 this process was significantly faster than for Pt on CeO2. The increased reduction ability of Pt on Ba is reflected in the light off temperatures: for Pt on CeO2 temperatures around 330 degrees C were needed to combust 20% of C3H6 in air while for Pt on BaCO3 only 250 degrees C were required for the same conversion. The ability to control the location of Pt or other noble metals is, therefore, essential to optimize the catalysts for a given Pt/Ba/CeO2 weight ratio. The best performance was observed when most of the Pt constituent was located near Ba-containing sites.