Pyrolysis mechanism and thermal hazard essence investigation using thermal analysis coupled with quantum-chemical DFT simulation for 1-butyl-2,3-dimethylimidazolium nitrate

1-Butyl-2,3-dimethylimidazolium nitrate ([Bmmim][NO₃]) is a functionality ionic liquid extensively used in industrial field. Under thermal disturbance scenarios or special high temperature conditions, [Bmmim][NO₃] may cause serious safety accidents due to thermal decomposition. To understand the thermal hazard characteristics and pyrolysis mechanism of [Bmmim][NO₃] more comprehensively, then determine the intrinsic reasons leading to its thermal hazard. In this paper, the thermal hazard characteristics of [Bmmim][NO₃] have been studied with differential scanning calorimetry, thermogravimetric analyzer and accelerating rate calorimeter. Thermal decomposition parameters, thermal safety parameters and decomposition reaction model of [Bmmim][NO₃] were obtained based on experimental results. The microscopic mechanism of [Bmmim][NO₃] pyrolysis was investigated using gas chromatography-mass spectrometer (GC–MS), thermogravimetry-flourier transform infrared spectroscopy (TG-FTIR), thermogravimetric-photoionization mass spectrometry (TG-MS), and quantum-chemical density functional theory (DFT) simulation. HCN, CO₂, C₂H₆, HCHO, and CH₃OH were the main harmful gases produced in the process of [Bmmim][NO₃] decomposition. In addition, the main reaction steps that result in the thermal hazard characteristics of [Bmmim][NO₃] were identified. This study may provide guidance for enhancing its security application and reducing or controlling its related hazardous accidents.