Preparation, characterization and investigation of catalytic activity for NO plus CO reaction of LaMnO3 and LaFeO3 perovskites prepared via microemulsion method

Two typical perovskites LaMnO3 and LaFeO3 have been successfully prepared via microemulsion method both in the reverse and bicontinuous state. Pure perovskite crystal phases are achieved at final calcinations temperature of 800 degreesC. The specific surface areas (S-p) of the obtained materials were 24 and 12 m(2) g(-1) for the LaMnO3 prepared via reverse and bicontinuous phase and while the corresponding S-p for LaFeO3 were 30 and 14 m(2) g(-1). SEM images have shown that perovskites developed via reverse micelles have smaller particle size than those developed via the bicontinuous phase. The perovskites were tested for NO + CO reaction and exhibited higher catalytic activity than similar materials prepared via the ceramic method. The reactants NO and CO react in a 2:1 ratio at low temperature but they convert in a 1: 1 ratio at high temperatures. From the kinetic analysis the heat of NO adsorption is estimated. In the case of manganese-containing materials except for the S-p, the percentage of Mn3+-O-Mn4+ pairs seems to be another critical factor which influences the catalytic activity. (C) 2003 Elsevier B.V All rights reserved.