Thermal hazard risk and decomposition mechanism identification of 1-Hexyl-2,3-dimethylimidazolium nitrate: Combined thermal analysis experiment and DFT emulation

Ionic liquids are extensively used in pharmaceutical, chemical and aerospace fields, and sometimes used in high temperature environments. Investigating the pyrolysis hazard characteristics and mechanism of ionic liquids is significant. 1-Hexyl-2,3-dimethylimidazolium nitrate ([Hmmim][NO₃]) as a new versatile ionic liquid has been systematically studied in this paper. The pyrolysis characteristics of [Hmmim][NO₃] in different conditions are researched by using thermogravimetric analyzer, differential scanning calorimetry and accelerating rate calorimeter technologies. Main thermodynamic parameters, safety parameters, and reaction pattern of [Hmmim][NO₃] pyrolysis process are acquired. The severity degree and possibility of [Hmmim][NO₃] runaway reaction is evaluated, which may result in serious damage to the plant. The microscopic mechanism of [Hmmim][NO₃] pyrolysis has been explored comprehensive utilization thermogravimetry-flourier transform infrared spectroscopy, thermogravimetric-photoionization mass spectrometry and quantum-chemical simulation. The primary noxious gas and reaction steps leading to the thermal hazards of [Hmmim][NO₃] are confirmed. This research provides a theoretical basis for improving the intrinsic safety of [Hmmim][NO₃] application and formulating corresponding safety preventive measures.