Preparation, Structure, and Selected Catalytic Properties of the System LaMn1‐xCuxO3‐y

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Abstract
Samples of LaMn1‐xCuxO3‐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 La2CuO4 and CuO as well as the perovskite phase. Samples of LaMn1−x,Cux,O3−y supported on ceramic monoliths or when mixed with powdered A12O3 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 SO2, 2% H2O 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 Co3O4>Pt>LaMn1−xCuxO3−y (0.4≤x≤0.7)>copper chromite>La1−xSrx,MnO3≤ other substituted LaMnO3 materials, CuO, or La2CuO4. The perovskite catalyst is more stable than Co3O4 or copper chromite when heated in 10% H2+ 90% N2.