Abstract
A series of structural modified LaxMnO3 (x=0.9, 0.95, 1, 1.05, 1.11) perovskites used for NO oxidation was synthesized by a sol–gel method and characterized by XRD, BET, XPS, EPR and H2-TPR. La0.9MnO3 sample exhibits superior activity, and a 50% NO conversion at 250°C is obtained. XPS and EPR results reveal a higher Mn4+/Mn3+ ratio in Mn-rich samples, which induce more active oxygen bonding to Mn4+ due to the need for balancing the chemical states and stabilizing the structure. Easily regenerated oxygen associated with Mn4+ catalyzes the low-temperature NO oxidation. The constant activation energy (44.8kJ/mol) obtained in the kinetics tests indicates the same mechanism of NO oxidation operated on all the samples.
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