Evaluation Of The Decomposition Characteristics And Thermal Hazards Of Four Imidazole Ionic Liquids With Multi-channel Thermal Analysis Technology

Ionic liquids（ILs）,as a salt that is liquid at room temperature,have broken a deep-rooted belief in salts by demonstrating that some of them can be ignited.Therefore,it is significant for intrinsically safe production to study the thermal decomposition characteristics and evaluate the thermal hazards of ionic liquids.In this study,the thermal stability and thermal effect of the special salts were evaluated,their decomposition products in different atmospheres were inferred from product analysis techniques,and their thermal hazard was assessed by accelerated adiabatic heating techniques.In this work,four typical and representative imidazole ionic liquids BMIMBF₄,BMIMDCN,BMIMNO₃ and BMIMOAc were selected as research objects.Specific research work and relevant conclusions are as follows:Their thermal stability and thermal effect were obtained by simultaneous thermogravimetric analyzer（STA）and differential scanning calorimetry（DSC）.According to T_onset of the same heating rate,the thermal stability can be ranked as BMIMOAc<BMIMNO₃<BMIMDCN<BMIMBF₄.According to the amount of heat release in nitrogen,the rankings are as follows:BMIMOAc<BMIMNO₃<BMIMBF₄<BMIMDCN.The thermogravimetric curves of the four selected IL are almost the same in air or nitrogen,but they are different in DSC experiment and show completely different thermal effects in the decomposition process.The endothermic phenomenon in nitrogen environment will be converted into exothermic phenomenon in air environment.In addition,the mechanism of exothermic phenomena of selected ionic liquids in air has positive feedback effect.The decomposition mechanism was studied by thermogravimetric analysis coupled with Fourier-transformed infrared spectrometry（TG-FTIR）.The results show that the thermal decomposition mechanism of the four selected ionic liquids in air is different from that in nitrogen.The initial decomposition products of BMIMBF₄ and BMIMDCN differed greatly in the presence of air or nitrogen.The decomposition products of BMIMNO₃ and BMIMOAc in air have more oxidation products than nitrogen.It is proved that the decomposition process of imidazole ionic liquid is as follows:liquid imidazole ionic liquids first decomposes into gaseous macromolecule organic matter at high temperature,and then gaseous macromolecule organic matter is oxidized and decomposed in oxidizing atmosphere and gives off a large amount of heat.In addition,the reducibility of intermediate decomposition products is proved to be responsible for the special thermal effects of these imidazole ionic liquids in different gas environments.The thermal runaway of four selected imidazoles BMIMBF₄,BMIMDCN,BMIMNO₃ and BMIMOAc in an adiabatic environment was simulated by accelerating the"HEAT-WAIT-SEEK"mode of the adiabatic adiabatic calorimeter（ARC）.The corrected adiabatic temperature rise valueΔT_ad,s of BMIMDCN,BMIMNO₃ and BMIMBF₄ were 348.853,219.250 and 190.500 ^oC,respectively,except that BMIMOAc had no obvious exothermic effect.The corrected arrival time of the maximum reaction rate value,TMR_ad,s were 49.988,25.420 and 26.625 min,respectively.BMIMDCN,BMIMNO₃ and BMIMBF₄ all belonged to class III unacceptable risk.Therefore,effective measures must be taken to reduce the possibility and severity of the risk.This work is innovative in studying the thermal effect and decomposition mechanism of imidazole ionic liquids.The research results provide certain safety guidance for the production,storage and transportation of imidazole ionic liquids,and eliminate the potential safety hazards of imidazole ionic liquids.Figure 28 Table 19 Reference 89...