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

Abstract

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.