Mechanism and kinetics of the oxidation of synthetic α-NiS

The results of an investigation of the mechanism and kinetics of the oxidation process of synthetic α-NiS are presented in this paper. The mecha- nism of α-NiS oxidation was investigated based on the comparative analysis of DTA-TG-DTG and XRD results, as well as the constructed phase stability dia- grams (PSD) for the Ni-S-O system. The kinetic investigations of the oxida- tion process were performed under isothermal conditions (temperature range 823-1073 K). The obtained degrees of desulfurization were used in the calcu- lation process according to the Sharp model and the kinetic parameters, inclu- ding the activation energies and the rate constants of the characteristic reac- tions, for the oxidation of α-NiS were determined. These results enabled the formulation of a kinetic equation for the desulfurization process: -ln (1 − α) = = k1τ = 27.89 exp(-9860/T)τ, with an activation energy of 82±4 kJ mol-1, for the first stage of the process and -ln (1 − α) = k2τ = 1.177 exp(-4810/T)τ, with an activation energy of 40±2 kJ mol-1, for the second stage.