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 H-2-TPR. La0.9MnO3 sample exhibits superior activity, and a 50% NO conversion at 250 degrees 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 (44.8 kJ/mol) obtained in the kinetics tests indicates the same mechanism of NO oxidation operated on all the samples. (C) 2013 Elsevier B.V. All rights reserved.