A kinetic and mechanistic study of the thermal decomposition of copper(II) permanganate

Abstract

The thermal decomposition of copper(II) permanganate has been studied between 335 and 370 K. Isothermal yield—time curves for the evolution of product oxygen (1.27 mol O 2 per mol Cu(MnO 4) 2) were sigmoid shaped and data fitted the Avrami—Erofe'ev equation ( n = 2): [−1n(1 − α)] 1 2 = kt, between 0.03 < α < 0.93 (where α is the fractional reaction). The activation energy for decomposition was 115 ± 15 kJ mol −1. In the mechanistic discussion presented it is concluded that anion breakdown occurred at the interface between the crystalline reactant and an ill-crystallized, probably several constituent, disorganized mixture of residual products. Permanganate anion breakdown is believed to follow electron transfer to a Cu 2+ ion ( → Cu +) that is subsequently reoxidized. A principal motivation for the work was as a route for the preparation of a non-stoichiometric, imperfect, microcrystalline mixture of transition metal oxides. The product of the present reaction is being investigated to determine its value as a precursor for the preparation of active heterogeneous oxidation catalysts.