Catalytic and Heating Behavior of Nanoscaled Perovskites under Microwave Radiation

Perovskite powders of the types La(0.5)Ca(0.5)Al(y)M(1-y)O(3-delta) (y = 0-0.8), M = Fe, Cr, Mn, Co and La(x)Sr(1-x)Mn(y)Co(1-y) (x = 0.5-1, y = 0-1) were prepared via a sol-gel route according to the modified Pechini method. Incineration of the resins was performed before final sintering at 1000 degrees C for 6 h. The phase composition of the samples was established by X-ray powder diffraction analysis, and the lattice parameters were calculated using Rietveld analysis. The shape and size of the particles were determined via scanning electron microscopy and the specific surface area of the powder perovskites was established by the BET method. The principal particles were ca. 100 nm in size and formed agglomerates larger than 1.0 mu m. The composition of the perovskites was established by EDX analysis. Following this, the catalytic behavior was tested by means of total oxidation of propane. The catalytic performance was measured at atmospheric pressure with 3 g of catalyst in a fixed-bed quartz reactor (i.d. = 18 mm) under thermal-assisted and microwave-assisted conditions. Initial results show a strong dependence of the catalytic and heating behavior on the nature of the M-atom and its number of unpaired d-electrons as well as on the particle size and its specific surface area. No significant difference in the results could be detected from comparison of the two heating methods.