Thermal Decomposition and Reaction Kinetics of Manganese(II) Sulfate and Manganese(IV) Oxide

Abstract

The kinetics of thermal decomposition of manganese (II) sulfate into trimanganese tetraoxide, and of manganese(IV) oxide into manganese(III) oxide under reduced pressure were studied by using a vacuum thermobalance on the basis of phase diagrams of the Mn-S-0 and Mn-O-T systems. The pressure in the reaction tube was kept at ca.10^-3mmHg and the weight loss was isothermally measured. For the analysis of the reaction rate, the heat transfer controlling model, the mass transfer controlling model, and the chemical reaction controlling model were examined, respectively.
(1) Thermal decomp osition of manganese (II) sulfate: The heat transfer controlling model and the mass transfer controlling model were not adopted. The chemical reaction on the interface was found to control the over-all reaction rate and the rate constant k was determined.
(2) Thermal decomposition of manganese(N) oxide: The heat transfer controlling model and the chemical reaction controlling model were not adopted. The mass transfer controlling model was found to express the over-all reaction rate and the effective diffusivity of oxygen gas within the solid particle was estimated.