Effects of calcium substitute in LaMnO3 perovskites for NO catalytic oxidation

La1-x Cax MnO3 (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 La0.9 Ca0.1 MnO 3 sample showed the maximum conversion of 82% at 300 oC. The monodentate nitrates played a crucial role for the formation of NO2 . The reducibility of Mn 4+ ions and reactivity of activated oxygen were favorable for the catalytic performances of NO oxidation.     

Dynamic Oxygen Storage Capacity Measurements on Ceria-Based Material

The constant increase in the number of environ-mental protection regulations worldwide has broughtabout significant restrictions onthe nature and quantityof exhaust gases originating from mobile sources suchas automobile emissions .These increasingly dema…     

Effect of preparation method on MnOx-CeO2 catalysts for NO oxidation

The NO oxidation reaction was studied over MnO_x-CeO₂ catalysts prepared by co-precipitation, impregnation and mechanical mixing method, respectively. It was found that the co-precipitation was the most active and a 60% NO conversion was achieved at 250 °C. X-ray diffraction (XRD), Brumauer-Emmett (BET), H₂-temperature programmed reduction (H₂-TPR) and oxygen storage capacity (OSC) techniques were employed to characterize the physical and chemical properties of the catalysts. XRD results showed that amorphous MnO_x or Mn-O-Ce solid solution existed in co-precipitation and impregnation prepared sample, while crystalline MnO_x was found in mechanical mixing catalyst. A larger surface area was observed on co-precipitation prepared catalyst compared to those prepared by impregnation and mechanical mixing. The strong interaction between MnO_x and CeO₂ enhanced the reducibility of the oxides and increased the amount of Mn⁴⁺ and activated oxygen, which are favorable for NO oxidation to NO₂.