Catalytic Reduction of NO by CO over LaMn.sub.1-xFe.sub.xO.sub.3 and La.sub.0.8A.sub.0.2Mn.sub.0.3Fe.sub.0.7O.sub.3 Perovskite Catalysts

In this study, LaMn.sub.1-xFe.sub.xO.sub.3 (x = 0, 0.3, 0.5, 0.7, 1) and La.sub.0.8A.sub.0.2Fe.sub.0.7Mn.sub.0.3O.sub.3 (A = Sr, Cs, Ba, Ce) perovskite oxides were synthesized by sol-gel method and their activities were evaluated in catalytic reduction of NO by CO. Perovskite catalysts were characterized by XRD, BET, H.sub.2-TPR, XPS and SEM. Synthesized perovskites present a high activity for the catalytic reduction of NO by CO, LaMn.sub.0.3Fe.sub.0.7O.sub.3 Show the highest activity among LaMn.sub.1-xFe.sub.xO.sub.3 perovskite catalysts (71 % CO conversion and 82 % NO conversion at 350 °C). The effect of partial substitution of Sr, Cs, Ba and Ce in A-site was also examined on the structure and catalytic activity of LaMn.sub.0.3Fe.sub.0.7O.sub.3 perovskite catalyst. La.sub.0.8Sr.sub.0.2Fe.sub.0.7Mn.sub.0.3O.sub.3 and La.sub.0.8Ce.sub.0.2Fe.sub.0.7Mn.sub.0.3O.sub.3 present the highest activities among La.sub.0.8A.sub.0.2Fe.sub.0.7Mn.sub.0.3O.sub.3 perovskites. The introduction of Sr.sup.2+ and Ce.sup.4+ in A-site of perovskite change the reducibility of B-site cations and Fe.sup.4+/Fe.sup.3+ and Mn.sup.4+/Mn.sup.3+ ratios, and increase O.sub.ads/O.sub.latt ratio and these factors create structural defects in perovskite which lead to higher catalytic activities.