SOLID-SOLID INTERACTION BETWEEN MANGANESE CARBONATE AND ZINC CARBONATE AND THE DECOMPOSITION OF H2O2 OVER MIXED ZINC-MANGANESE OXIDE CATALYSTS

Pure mixed zinc carbonate and manganese carbonate with molar ratios 3:1, 1:1 and 1:3 with respect to ZnO:MnO2 were prepared. The thermal decomposition of pure salts was studied using DTA. Pure and mixed salts were subjected to thermal treatment at 250, 500, 750 and 1000 degrees C. The decomposition products were characterized by means of X-ray diffraction analysis. The results obtained were used to discuss the different structures of the thermal products of the pure and mixed oxides, at the temperatures under investigation and their catalytic activities were tested in H2O2 decomposition. The catalytic activity of these solids in hydrogen peroxide decomposition was found to increase with the increase of activation temperature passing through a maximum at 500 degrees C. The increase of calcination temperature above 500 degrees C was accompanied by a decrease of the activity in H2O2 decomposition. This may be attributed to sintering and/or formation of the inactive form of ZnMn2O4.