Flammability, thermal stability, and phase change characteristics of several trialkylimidazolium salts
Flammability, thermal stability, and phase change characteristics of several trialkylimidazolium salts
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DOI：
10.1039/b308444b
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发表时间：
2003-01-01
期刊：
影响因子：
9.8
通讯作者：
Trulove, PC
中科院分区：
文献类型：
--
作者：
Fox, DM;Awad, WH;Trulove, PC
室温离子液体（RTIL）已成为可调的和潜在的“绿色”溶剂的许多应用。为了研究溶剂性质和作为热流体的潜在用途，开始研究以确定阴离子类型、C- 2氢取代和烷基链长度对1，2，3-三烷基咪唑鎓室温离子液体的可燃性、热稳定性和相变特性的影响。使用Setaflash闪点装置来确定RTIL的可燃性。对于任何基于咪唑鎓的RTIL，在低于200 ℃（仪器的最高温度）时没有检测到闪点。采用热重分析技术测定了RTIL的热稳定性。1，2，3-三烷基咪唑鎓化合物表现出比可比较的1，3-二烷基咪唑鎓化合物略高的热稳定性;具有亲核阴离子的RTIL的分解温度比具有大体积含氟阴离子的RTIL低约150 ℃;烷基链长对RTIL的热稳定性没有大的影响;并且热解分解通过与氧化分解不同的机理表现出更高的热稳定性。此外，发现尽管计算的起始温度高于350 ℃，但在低于这些温度100 ℃或更高时确实发生显著的分解。采用差示扫描量热法对几种咪唑类RTIL的相变行为进行了表征。RTIL的熔点随着烷基链长度的增加而增加。大多数研究的盐表现出显着的过冷度，随着烷基链长度的增加而减少。六氟磷酸盐和溴化物RTIL表现出多晶型和液晶行为的烷基链长度增加以上C10。与熔点温度相比，清亮点温度随着烷基链长度的增加而增加得更快。
Room temperature ionic liquids ( RTILs) have emerged as tunable and potentially " greener" solvents for a multitude of applications. To investigate the solvent properties and potential use as a thermal fluid, a study was initiated to determine the effects of anion type, C- 2 hydrogen substitution, and alkyl chain length on the flammability, thermal stability, and phase change characteristics of 1,2,3- trialkylimidazolium room temperature ionic liquids. A Setaflash flashpoint apparatus was used to determine the flammabilities of the RTILs. No flashpoints were detected for any of the imidazolium based RTILs below 200 degrees C, the maximum temperature of the instrument. The thermal stabilities of the RTILs were measured using the technique of thermogravimetric analysis. The 1,2,3- trialkylimidazolium compounds exhibit slightly higher thermal stabilities than the comparable 1,3- dialkylimidazolium compounds; RTILs with nucleophilic anions decompose about 150 degrees C lower than RTILs with bulky fluoride containing anions; the alkyl chain length does not have a large effect on the thermal stability of the RTILs; and the pyrolysis decomposition exhibits higher thermal stabilities via a different mechanism than the oxidative decomposition. In addition, it was found that although the calculated onset temperatures were above 350 degrees C, significant decomposition does occur 100 degrees C or more below these temperatures. The phase change behaviors of several imidazolium based RTILs were characterized by differential scanning calorimetry. The melting points of the RTILs increased with increasing alkyl chain length. Most of the salts studied exhibited significant undercooling, which decreased as the length of the alkyl chain was increased. The hexafluorophosphate and bromide RTILs exhibited polymorphic and liquid crystalline behaviors as the alkyl chain length was increased above C10. The clearing point temperatures increased more rapidly with alkyl chain length than the melting point temperatures.