A study on multistep thermal decomposition behavior and kinetics of magnesium nitrate hydrate

The multistep thermal decomposition behavior and kinetic feature of magnesium nitrate hydrate (MNH) were studied systematically in this study. Firstly, the multistep reaction processes in MNH pyrolysis were identified by Thermogravimetry-Fourier Transform Infrared analysis. Then, a common method of data processing, mathematical peak deconvolution, was used to separate such complex multistep reaction processes. Additionally, kinetic triplets of each separated process were determined by Friedman isoconversional method and Ozawa kinetic equation. Finally, kinetic features of each separated process were interpreted in terms of the physico-geometrical reaction mechanism. The results showed that MNH pyrolysis was a complex multistep reaction, including three reaction processes. The first two reaction processes were characterized by evolution of H2O, whereas the third reaction process was characterized by evolution of NO2. Three processes obeyed diffusion, order-based and nucleation and growth mechanisms, with E(apparent activation energy) = 80 ± 1, 137 ± 2, 227 ± 4 kJ/mol and A(pre-exponential factor)=(2.5 ± 0.2)×109, (1.5 ± 0.1)×1011 and (8.8 ± 0.2)×1015 s−1, respectively.