Preparation, Structure, and Selected Catalytic Properties of the System LaMn _1‐x Cu _x O _3‐y

Abstract

Samples of LaMn 1‐x Cu x O 3‐y in the range 0≤x≤0.8 were prepared from freeze‐dried solutions of the nitrates. Samples with x≤0.6 were single‐phase perovskites. At higher values of x , the samples contained La 2 CuO 4 and CuO as well as the perovskite phase. Samples of LaMn 1−x ,Cu x ,O 3−y supported on ceramic monoliths or when mixed with powdered A1 2 O 3 exhibit catalytic activity for the oxidation of CO. Greatest activity is shown for 0.4≤x≤0.7. Although the catalysts are severely poisoned by SO 2 , 2% H 2 O in the gas stream causes only slight deactivation. Activities of other oxide catalysts were also measured and compared. Rate constants per unit surface area at 200° to 400°C follow the order Co 3 O 4 >Pt>LaMn 1−x Cu x O 3−y (0.4≤x≤0.7)>copper chromite>La 1−x Sr x ,MnO 3 ≤ other substituted LaMnO 3 materials, CuO, or La 2 CuO 4 . The perovskite catalyst is more stable than Co 3 O 4 or copper chromite when heated in 10% H 2 + 90% N 2 .