Catalytic Effects of Lanthanide Oxides on the Thermal Decomposition of Barium Perchlorate

Abstract

Catalytic activities exerted by the lanthanide oxides Ln₂O₃ (Ln=La, Sm, Gd and Dy) (0.25 mol%) on the thermal decomposition of barium perchlorate were studied gasometrically at 718 K. The α vs. t plot for the salt alone displays (i) initial gas evolution (ii) an induction period, (iii) a short acceleratory stage and (iv) a long decay stage. For the mixtures with Ln₂O₃, phenomena (i) and (ii) are not observed. Ln₂O₃ enhances the rate of reaction in both the acceleratory and the decay stage, and increases the fraction decomposed, α, in the sequence La₂O₃>Gd₂O₃>Sm₂O₃,>Dy₂O₃.

The influence of Dy₂O₃ (0.25–2.0 mol%) on the decomposition of Ba(ClO₄)₂ at 718 K indicates that such admixture facilitates the process and the effect increases with increasing concentration.

The salt alone and the mixtures decompose through the same stages in the temperature range 703–733 K as at 718 K. The data on both types of samples fit well to the Prout-Tompkins and the Avrami-Erofeev mechanism, suggesting that nucleation takes place in a chain-branching manner and that the two-dimensional growth of the nuclei occurs during the process. Admixture enhances the rate of reaction marked without affecting the energy of activation .