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  • 1 Applied Chemistry Institute of R&D Center of PetroChina Pipeline Company, 51 Jinguang Road, 065000 Langfang, Hebei People’s Republic of China
  • | 2 PetroChina Pipeline Company, 51 Jinguang Road, 065000 Langfang, Hebei People’s Republic of China
  • | 3 Thermochemistry Laboratory, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, 116023 Dalian, People’s Republic of China
  • | 4 Faculty of Chemistry and Chemical Engineering, Liaoning Normal University, 116029 Dalian, People’s Republic of China
  • | 5 School of Chemistry and Environmental Engineering, Changsha University of Science and Technology, 410076 Changsha, People’s Republic of China
  • | 6 School of Physics and Optoelectronic Technology and College of Advanced Science and Technology, Dalian University of Technology, 116024 Dalian, People’s Republic of China
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Abstract  

The molar heat capacities of the room temperature ionic liquid 1-butyl-3-methylimidazolium hexafluoroborate (BMIPF6) were measured by an adiabatic calorimeter in temperature range from 80 to 390 K. The dependence of the molar heat capacity on temperature is given as a function of the reduced temperature (X) by polynomial equations, CP,m (J K−1 mol−1) = 204.75 + 81.421X − 23.828 X2 + 12.044X3 + 2.5442X4 [X = (T − 132.5)/52.5] for the solid phase (80–185 K), CP,m (J K−1 mol−1) = 368.99 + 2.4199X + 1.0027X2 + 0.43395X3 [X = (T − 230)/35] for the glass state (195 − 265 K), and CP,m (J K−1 mol−1) = 415.01 + 21.992X − 0.24656X2 + 0.57770X3 [X = (T − 337.5)/52.5] for the liquid phase (285–390 K), respectively. According to the polynomial equations and thermodynamic relationship, the values of thermodynamic function of the BMIPF6 relative to 298.15 K were calculated in temperature range from 80 to 390 K with an interval of 5 K. The glass transition of BMIPF6 was measured to be 190.41 K, the enthalpy and entropy of the glass transition were determined to be ΔHg = 2.853 kJ mol−1 and ΔSg = 14.98 J K−1 mol−1, respectively. The results showed that the milting point of the BMIPF6 is 281.83 K, the enthalpy and entropy of phase transition were calculated to be ΔHm = 20.67 kJ mol−1 and ΔSm = 73.34 J K−1 mol−1.

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