Effect of metal oxide additives on the thermal decomposition of perchlorates, oxalates and hydroxides

Abstract

The effects of α-Fe 2O 3 and α-Al 2O 3 additives on the thermal decomposition of perchlorates, oxalates and hydroxides were investigated by means of DTA, TG and X-ray techniques. It was found that the oxide additives catalytically promoted the decomposition of perchlorates (NaClO 4, KClO 4 and Mg(ClO 4) 2) and resulted in a lowering of the initial decomposition temperature ( T i ). On the other hand, the oxides showed no significant effect on the decomposition of oxalates (FeC 2O 4 and CuC 2O 4) and hydroxides (Mg(OH) 2 and Al(OH) 3). The thermal decomposition of KClO 4 was chosen to compare the catalytic effect of twelve metal oxides. The results indicated that the transition metal oxides such as Cr 2O 3, α-Fe 2O 3 and CuO markedly accelerated the decomposition; these oxides resulted in a solid-phase decomposition before fusion of KClO 4, and the initial decomposition temperature ( T i) of KClO 4 with oxides was about 100–200°C lower than that without catalyst. The oxides such as α-Al 2O 3 and MgO resulted in a slight lowering of the temperature of the fusion and promoted the molten-phase decomposition of KClO 4, but their effects were not so remarkable as those of the transition metal oxides. The modified catalytic mechanisms of transition metal oxides were proposed by considering the electron transfer and the oxygen-abstraction models.