Heterogeneous oxidation of hydrazine by barium chromate

Abstract

The kinetics of the heterogeneous oxidation of hydrazine by barium chromate in aqueous suspensions has been studied. The results obtained on changing the concentration of hydrazine and the mass of barium chromate show that the reaction proceeds through a fast chemisorption equilibrium in which a complex is formed between chromium atoms on the surface of the particles and hydrazine. A Langmuir-type analysis of the data gave an adsorption equilibrium constant of 1.14 × 10² dm³ mol^–1 and a rate constant k for the decomposition of the adsorption complex of 1.1 × 10^–2 s^–1. A comparison between this heterogeneous reaction and the corresponding homogeneous reaction shows that the presence of the interface leads to acceleration by a factor of ca. 10⁶. It is shown that this acceleration is due in part to the increased concentration of the complex at the interface ([adsorption complex]/[complex]_hom= 10⁴) and to an increase in its reactivity (k_het/k_hom= 10²). A possible explanation for this enhanced reactivity is given.