(La0.8A0.2)MnO3 (A=Sr, K) perovskite catalysts for NO and C10H22 oxidation and selective reduction of NO by C10H22

摘要

In this work, we studied the catalytic activity of LaMnO3 and (La0.8A0.2)MnO3 (A=Sr, K) perovskite catalysts for oxidation of NO and C10H22 and selective reduction of NO by C10H22. The catalytic per-formances of these perovskites were compared with that of a 2 wt%Pt/SiO2 catalyst. The La site substitution increased the catalytic properties for NO or C10H22 oxidation compared with the non-substituted LaMnO3 sample. For the most efficient perovskite catalyst, (La0.8Sr0.2)MnO3, the results showed the presence of two temperature domains for NO adsorption:(1) a domain corre-sponding to weakly adsorbed NO, desorbing at temperatures lower than 270 °C and (2) a second domain corresponding to NO adsorbed on the surface as nitrate species, desorbing at temperatures higher than 330 °C. For the Sr-substituted perovskite, the maximum NO2 yield of 80%was observed in the intermediate temperature domain (around 285 °C). In the reactant mixture of NO/C10H22/O2/H2O/He, (La0.8Sr0.2)MnO3 perovskite showed better performance than the 2 wt%Pt/SiO2 catalyst:NO2 yields reaching 50%and 36%at 290 and 370 °C, respectively. This activity improvement was found to be because of atomic scale interactions between the A and B active sites, Sr2+cation and Mn4+/Mn3+redox couple. Thus, (La0.8Sr0.2)MnO3 perovskite could be an alternative free noble metal catalyst for exhaust gas after treatment.