The effect of oxygen on the thermal stability and decomposition behaviours of 1,3-dimethylimidazolium nitrate for application using STA, ARC and FTIR

Abstract

The thermal decomposition and runaway reaction of 1,3-dimethylimidazolium nitrate ([Mmim]NO3), a typical nitrate IL, were studied by a simultaneous thermogravimetric analyzer (STA) and accelerating rate calorimeter (ARC). The STA results show that the thermal decomposition of [Mmim]NO3 is divided into two stages, and the decomposition behaviour is similar in nitrogen or oxygen. The experimental results under adiabatic conditions indicate that [Mmim]NO3 has higher Tmax and Pmax than other imidazolium ILs, which reflects the greater explosion hazard of [Mmim]NO3. The apparent activation energies of [Mmim]NO3 were 86 kJ/mol and 83 kJ/mol, as calculated by the F-W-O and K-A-S methods. The complete thermal decomposition gas products of [Mmim]NO3 were analyzed by thermogravimetry coupled with Fourier transform infrared spectroscopy (TG-FTIR), and the gas released by thermal decomposition of [Mmim]NO3 does not react with oxygen. Therefore, the decomposition reaction of [Mmim]NO3 was not positively related to the concentration of oxygen, which indicated that [Mmim]NO3 could play an active role in the reactions in the presence of oxygen. The results of this study may provide theoretical and experimental basis for [Mmim]NO3 safety precautions in storage and transportation.