The formation and physicochemical properties of magnesium manganates

The effects of calcination temperature, molar ratio and the doping by CeO2 on the solid-solid interactions, surface and catalytic properties of Mn/Mg mixed oxide system have been studied by XRD, nitrogen adsorption at -196 degrees C and the catalytic decomposition of hydrogen peroxide at 20, 30, and 40 degrees C. The results revealed that the manganese oxides interacted with magnesium oxide to yield well crystallized magnesium manganates at temperatures starting from 600 degrees C, this reaction found to be affected by the molar ratio of the reacted oxides present and also by the dopant content. However, the treatment of the Mn/Mg mixed oxide system with increasing amounts of manganese and cerium oxides followed by calcination at 400-800 degrees C brought about an increase in the catalytic activity of the resulting solids, whilst the opposite effect was observed in the surface area of the investigated solids. These treatments resulted in an increase in the particle size of MgO and a decrease in both the activation energy of sintering of the investigated system and that necessary for hydrogen peroxide decomposition reaction. (c) 2005 Published by Elsevier B.V.