(La(0.8)A(0.2))MnO3 (A = Sr, K) perovskite catalysts for NO and C10H22 oxidation and selective reduction of NO by C10H22
Résumé
In this work, we studied the catalytic activity of LaMnO3 and (La(0.8)A(0.2))MnO3 (A = Sr, K) perovskite catalysts for oxidation of NO and C10H22 and selective reduction of NO by C10H22. The catalytic performances 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 corresponding to weakly adsorbed NO, desorbing at temperatures lower than 270 degrees C and (2) a second domain corresponding to NO adsorbed on the surface as nitrate species, desorbing at temperatures higher than 330 degrees 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/O-2/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 degrees 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. (C) 2014, Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by Elsevier B.V. All rights reserved.