Catalytic Effect of Some Chromites on the Thermal Decomposition of KClO4. Mechanistic and non-isothermal kinetic studies

The catalytic effect of two different groups of chromites on the non-isothermal decomposition of KClO 4 was studied. TG and DSC curves of the thermal behaviour obtained for KClO 4 -alkaline earth chromites (Series 1) mixtures indicate the formation of K 2 Cr 2 O 7 , through a solid-solid interaction, before accelerating the decomposition stage of KClO 4 . Such an accelerating effect becomes more pronounced in the case of admixing KClO 4 with some transition metal chromites (Series 2). The results were discussed taking into consideration the electronic configuration of cations and the electrical properties of the chromite catalysts. The presence of coordinatively active cations, able to form surface complex with the oxygen of the perchlorate anion, was proved to be necessary for obtaining an active catalyst. The kinetic parameters and models describing the catalyzed thermal decomposition process of KClO 4 were evaluated by using a computer program that allows the analysis using five different methods. It was found that the adopted kinetic model for pure KClO 4 and that mixed with catalysts from Series 1 is one-dimensional movement of phase boundary. On the other hand, random nucleation mechanism was achieved in the presence of catalysts from Series 2. Finally, a tentative reaction mechanism consistent with the obtained results was suggested.