III International Conference

PP-II-101ACTIVITY OF La 1-x Sr x MnO 3 SYSTEMS IN THE REACTION OF HIGHTEMPERATURE N 2 O DECOMPOSITIONPinaeva L.G., Isupova L.A., Ivanov D.V., Kulikovskaya N.A., Tsybulya S.V.,Gerasimov E.Yu., Prosvirin I.P.Boreskov Institute of Catalysis SB RAS, Novosibirsk, RussiaE-mail: pinaeva@catalysis.nsk.suLa 1-x Sr x MnO 3 mixed oxides were prepared and tested in the reaction of high temperatureN 2 O decomposition. Prominent increase of activity at x = 0.4÷0.8 (including the case of bothwater and oxygen presence in the reaction mixture) correlates well with formation oflaminated structure (La 1-x Sr x ) 2 MnO 4 consisting of alternating perovskite and SrO layers.Mixed oxides with perovskite structure LaMO 3 (where M is mostly 3d-transition metalelement, like Fe, Co, Mn) can be considered as very prospective systems for the hightemperatureN 2 O abatement due to their high thermal stability and presence of oxygenvacancies in perovskite structure, that are important sites for N 2 O adsorption. Moreover,perovskites possess enhanced lattice oxygen mobility at high temperatures thus promotingactive sites regeneration. Partial substitution of La or B cation with an ion of other valencegiving rise to abnormal valencies of B-site cation and/or additional oxygen vacancies is anadditional way to regulate both active sites concentration and lattice oxygen mobility. Themain objective of this study was the elucidation of the effect of La substitution by Sr inLa 1-x Sr x MnO 3 on the lattice structure, texture, oxygen mobility and activity in the reaction ofN 2 O decomposition.La 1-x Sr x MnO 3 mixed oxides were prepared by Pechini route by mixing saturated watersolutions of the nitrates of corresponding elements in necessary quantities with citric acid andethylene glycol to obtain desired La/Sr ratio followed by heating in air, first – up to about140-150 o C to decompose nitrates, and then - up to 900 o C or 1000 o C and kept at thesetemperatures for 4 h to form the perovskite. XRD, XPS and HREM have been used tocharacterize lattice structure of mixed oxides formed, texture of species, surface layerscomposition. Bulk oxygen mobility was characterized by TPR. Catalytic activity in thereaction of N 2 O decomposition was measured in a plug flow reactor at 900 o C and contacttime 0.001s. Inhibiting effect of H 2 O and O 2 on the reaction running was checked by addingup to 10 % vol. of O 2 or H 2 O into the reaction mixture composing of 0.15% vol. N 2 O in He.348