Effects of calcium substitute in LaMnO3 perovskites for NO catalytic oxidation

La1–xCaxMnO3 (x=0–0.3) perovskite-type oxides were synthesized by citrate sol-gel method. The physical and chemical properties were characterized by X-ray diffraction (XRD), Brumauer-Emmett-Teller method (BET), X-ray photoelectron spectroscopy (XPS), NO+O2-TPD (temperature-programmed desorption), activated oxygen evaluation and H2-TPR (temperature-programmed reduction) technologies. The results showed that NO catalytic oxidation activity was significantly improved by Ca substitution, especially for lower temperature activity. The La0.9Ca0.1MnO3 sample showed the maximum conversion of 82% at 300 °C. The monodentate nitrates played a crucial role for the formation of NO2. The reducibility of Mn4+ ions and reactivity of activated oxygen were favorable for the catalytic performances of NO oxidation.