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.

1-丁基-2,3-二甲基咪唑硝酸盐（[Bmmim][NO ₃ ]）是一种广泛应用于工业领域的功能性离子液体。在热扰动场景或特殊高温条件下，[Bmmim][NO ₃ ]可能因热分解而引发严重的安全事故。更全面地了解[Bmmim][NO ₃ ]的热危害特征和热解机理，进而确定导致其热危害的内在原因。在本文中，[Bmmim][NO ₃] 已经用差示扫描量热法、热重分析仪和加速量热仪进行了研究。根据实验结果，得到了[Bmmim][NO _{3 ]的热分解参数、热安全参数和分解反应模型。}[Bmmim][NO ₃ ] 热解的微观机理采用气相色谱-质谱 (GC-MS)、热重-弗洛里耶变换红外光谱 (TG-FTIR)、热重-光电离质谱 (TG-MS) 和量子化学密度泛函理论 (DFT) 模拟。HCN、CO ₂、C ₂ H ₆、HCHO和CH ₃ OH是[Bmmim][NO₃ ]分解。此外，还确定了导致[Bmmim][NO ₃ ] 热危险特性的主要反应步骤。本研究可为加强其安全应用和减少或控制其相关危险事故提供指导。