Auto-ignition Characteristics of Selected Ionic Liquids

• Published in: Procedia engineering 2014, Vol.84, p.285-292
• Main Authors: Chen, Yan-Ting, Chen, Chan-Cheng, Su, Chung-Hwei, Liaw, Horng-Jang
• Format: Article
• Language: English
• Subjects: ASTM E659 Method; Auto-ignition Temperature; Ionic Liquids
• ISSN: 1877-7058; 1877-7058
• DOI: 10.1016/j.proeng.2014.10.436

While being compared with commonly used organic solvents, ionic liquids are known of their low volatility. Thus they are usually considered to be green solvents to replace so far used organic solvent to eliminate the pollution of volatile organic compounds. Because of the low volatility, ionic liquids are also considered to be nonflammable in previous studies. However, recent studies do show ionic liquids are flammable. In this study, the auto-ignition characteristics of three ionic liquids, 1-Ethyl-3-methylimidazolium ethylsulfate, 1-Hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide and 1-Decyl-3-methylimidazolium bis(trifluoromethylsulfony)imide, are explored. Auto-ignition temperatures of these three ionic liquids are measured according to ASTM E659 method, and differential scanning calorimeter are used to investigate their thermal decomposition characteristics. Experimental results show that the auto-ignition temperatures of 1-Ethyl-3-methylimidazolium ethylsulfate, 1-Hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide and 1-Decyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide are 423.1̊C, 452.1̊C and 441.5̊C, respectively. According to the code of NFPA 70 (National Electrical Code), electric equipment for handling these ionic liquids should meet the requirement of T codes to be T2, T1 and T2 for 1-Ethyl-3-methylimidazolium ethylsulfate, 1-Hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide and 1-Decyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, respectively. The results of differential scanning calorimeter show that all these three ionic liquids decompose at the temperature below their auto-ignition temperature. It should be noted that the decomposition of 1-Ethyl-3-methylimidazolium ethylsulfate is endothermic, which clearly indicates that the combustion observed at is auto-ignition temperature is the oxidation reaction of the vapors of decomposition products rather than the oxidation reaction of the vapors of ionic liquids itself.