Thermal hazard of 1-butyl-3-methylimidazolium nitrate assessment via STA, ARC, TG–FTIR analysis and thermodynamic calculation

1-Butyl-3-methylimidazolium nitrate ([C4mim]NO3) is a versatile and novel solvent for the gas separation industry. However, [C4mim]NO3 may cause explosions or other safety problems under upset scenarios. This study investigated the thermal hazard of [C4mim]NO3 using simultaneous thermogravimetric analyzer (STA), accelerating rate calorimeter (ARC), and thermogravimetry coupled with Fourier transform infrared spectroscopy (TG–FTIR). The initial thermal decomposition temperature of [C4mim]NO3 was 244.0 °C under adiabatic conditions, which was significantly lower than that under nonisothermal conditions. The maximum operation temperature of [C4mim]NO3 was also predicted based on the results of dynamic experiments. A critical runaway reaction of [C4mim]NO3 would be produced once heat accumulated according to the ARC tests. The exothermic pressure extended 34.0 bar within 3.8 s, which confirmed the vulnerability of [C4mim]NO3 to undergo a catastrophic explosion. Furthermore, the thermal decomposition mechanisms of [C4mim]NO3 were obtained based on the TG–FTIR results. These results are vital for designing inherently safer processes of [C4mim]NO3 production, storage, and transportation.