Heterogeneous decomposition of hydrazine. Part 1.—On a supported rhodium catalyst

Abstract

A study has been made of the kinetics of the decomposition of aqueous hydrazine solutions on a supported rhodium catalyst. The decomposition may be represented by the reaction: 2N₂H₄→ N₂+ H₂+ 2NH₃ and it has been shown, using N¹⁵ as a tracer, that the nitrogen molecule is formed from the two nitrogen atoms of one hydrazine molecule without N—N bond fission. The kinetics exhibit a change from one-half order at low concentrations of hydrazine to zero order at high concentrations of hydrazine. The activation energy of the reaction was calculated to be 41.28 ± 0.33 kJ mol^–1 and the pre-exponential factor 3.45 × 10² mole g^–1 s^–1. A reaction mechanism is postulated which involves the dissociative chemisorption of hydrazine followed by reaction between adsorbed NH radicals and molecularly adsorbed hydrazine molecules.