A kinetic study of non-isothermal decomposition process of anhydrous nickel nitrate under air atmosphere

Abstract

The non-isothermal decomposition process of anhydrous nickel nitrate under air atmosphere was investigated. The kinetic analysis of decomposition process was performed using Friedman (FR), Kissinger-Akahira-Sunose (KAS) and Flynn-Wall-Ozawa (FWO) isoconversional methods. The kinetic model was determined by the Málek's method. The composite differential method I was used for checking the established reaction model. It was found that the value of Ea calculated by composite differential method (Ea=147.1 kJ mol-1) represents the medium value between the values of the apparent activation energy calculated by FR (Ea,FR=152.8 kJ mol-1) and FWO (Ea,FWO=143.1 kJ mol-1) methods. Using two special functions (y(α) and z(α)), it was found that the two-parameter autocatalytic model (Šesták-Berggren (SB) kinetic model) with kinetic exponents M=0.23 and N=1.14 is the most adequate one to describe the decomposition kinetics of the studied system at various heating rates. The obtained non-isothermal differential conversion curves from the experimental data show the results being accordant with those theoretically calculated. It was concluded that the SB kinetic model can be used for a quantitative description of non-isothermal decomposition process of anhydrous nickel nitrate which involves the partially overlapping nucleation and growth phases. © 2009 Elsevier B.V. All rights reserved.