Thermodynamic investigation of room temperature ionic liquid |
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Authors: | Z. H. Zhang T. Cui J. L. Zhang H. Xiong G. P. Li L. X. Sun F. Xu Z. Cao F. Li J. J. Zhao |
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Affiliation: | (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, C P,m (J K−1 mol−1) = 204.75 + 81.421X − 23.828 X 2 + 12.044X 3 + 2.5442X 4 [X = (T − 132.5)/52.5] for the solid phase (80–185 K), C P,m (J K−1 mol−1) = 368.99 + 2.4199X + 1.0027X 2 + 0.43395X 3 [X = (T − 230)/35] for the glass state (195 − 265 K), and C P,m (J K−1 mol−1) = 415.01 + 21.992X − 0.24656X 2 + 0.57770X 3 [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 ΔH g = 2.853 kJ mol−1 and ΔS g = 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 ΔH m = 20.67 kJ mol−1 and ΔS m = 73.34 J K−1 mol−1. |
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