双阳离子型离子液体[C_4(MIM)_2][PF_6]_2的比热容测定及其模型化

Measurement and modeling of the molar heat capacity of the dicationic ionic liquid [C_4(MIM)_2][PF_6]_2

利用差示扫描量热计(DSC)测定了双阳离子型离子液体1,1′-(丁烷-1,4-二基)-双(3-甲基-1H-咪唑鎓-1-基)双六氟磷酸盐([C4(MIM)2][PF6]2)在293.15～513.15 K温区内的摩尔比热容。结果表明,在293.15～363.15 K和398.15～513.15 K温区内,该化合物无相变及其他热异常现象发生,比热容随温度变化符合二次方程。在363.15～398.15 K温区内,该物质发生固-液熔化相变,其熔化温度、熔化焓及熔化熵分别为384.71 K、28.243kJ/mol和73.414 J/(K.mol)。根据热力学函数关系式,计算出[C4(MIM)2][PF6]2相对于标准参考温度298.15 K的热力学函数值。采用基团贡献法对液相区的热容进行了估算,结果表明,估算值与实验值符合很好。

The molar heat capacity of the dicationic ionic liquid 1,1′-（butane-1,4-diyl）-bis（3-methyl-1H-imidazolium-1-yl） dihexafluorophosphate[C4（MIM）2][PF6]2 has been measured using a differential scanning calorimeter（DSC） at temperatures from 293.15K to 513.15K.No phase transition or other thermal anomaly was observed in the temperature ranges 293.15-363.15K and 398.15-513.15K,in which the molar heat capacities were fitted to two polynomials.The melting point,molar enthalpy and entropy of fusion were determined to be 384.71K,28.243kJ/mol and 73.414J/（K·mol）,respectively.The thermodynamic functions of [C4（MIM）2][PF6]2 relative to the reference temperature 298.15 K were derived based on the heat capacity data.A group contribution method was used to calculate the molar heat capacity of [C4（MIM）2][PF6]2 in the liquid region.The results showed that the calculated values are in good agreement with the experimental values.