High-throughput study of the performance of NOxNOx storage and reduction catalysts as a function of cycling conditions and catalyst composition

NOxNOx storage and reduction (NSR) catalysts were studied both as a function of cyclic operating conditions and Pt, Ba, and Fe weight loadings via high-throughput experimentation using response surface analysis at T=648K. An empirical model was developed to predict the catalyst performance as a function of cycle time, lean fraction of cycle time, and catalyst composition. Using this empirical model for a 0.5 wt% Pt/7.5 wt% Ba/2.5 wt% Fe catalyst, it was found that maximum NOxNOx conversion and selectivity to N2N2 was obtained for cycle time between 60 and 125 s and a lean fraction <0.65<0.65. Fe was found to act as a promoter, extending the region of the complete NOxNOx conversion to lower Pt and Ba weight loadings, as well as acting as an oxidizing agent in the absence of Pt and a storage component in the absence of Ba. Finally, it was found that at higher lean fractions, the catalyst performance was governed by the rate at which the stored nitrates were reduced under fuel rich conditions.