Optimization of mixed Ag catalysts for catalytic conversions of NO and C3H6

In order to adjust the redox properties of perovskite-based silver catalysts to satisfy the requirements for their application under overstoichiometric oxygen conditions (lean burn), three mixtures were prepared [Mixture (I): 10% La0.88Ag0.12FeO(3) + 90% Al2O3; Mixture (II): 3% Ag/(10% La0.88Ag0.12FeO(3) + 90% Al2O3); Mixture (III): 10% La0.88Ag0.12FeO(3) + 90% (3% Ag/ Al2O3)]. Mixture (I) with only a 10% La0.88Ag0.12FeO(3) blend exhibited a NO reduction behavior similar to that of La0.88Ag0.12FeO(3) alone at stoichiometric oxygen (1% O-2). NO conversion of La0.88Ag0.12FeO(3) under an excess of oxygen (10% O-2) was however significantly improved by mixing with Al2O3 resulting in a value of similar to 30% at > 400 degrees C in the case of Mixture (I). Ag impregnation facilitated the NO catalytic reduction, leading to a better deNOx performance for Mixture (II) and Mixture (III) than that of Mixture (I). It was also found that those silver atoms associated with Al2O3 are more effective for NO transformation. Therefore, the optimal mixed catalyst was Mixture (III), which shows satisfactory NO reduction and C3H6 oxidation at 500 degrees C under the whole range of O-2 content from 1% to 10%.