Determination Of Low-Temperature Heat Capacity Performance For Ionic Liquids Exafluoride Antimonite

Since its discovery,ionic liquid has attracted wide attention from various industries due to its special physical and chemical properties.Especially in the fields of extraction separation,organic synthesis,catalytic reaction and so on,it shows great development prospect.In order to better develop and apply ionic liquids,their physical and chemical properties,especially thermochemical stability,should be supplemented and perfected.In this paper,the low temperature heat capacity of five alkyl imidazole hexafluoroantimonate ionic liquids was measured in the temperature range of 78 K³93 K,and their related thermodynamic functions were calculated according to the experimental data.In this paper,five alkyl imidazole hexafluoroantimonate ionic liquids with the same anions were synthesized by two-step synthesis:1-butyl 3-methyl imidazole antimonate six fluorine ionic liquid（[C₄mim][SbF₆]）,1-amyl-3-methyl imidazole antimonate six fluorine ionic liquid（[C₅mim][SbF₆]）,1-hexyl-3-methyl imidazole antimonate six fluorine ionic liquid（[C₆mim][SbF₆]）,1-butyl 3-ethyl imidazole antimonate six fluorine ionic liquid（[C₄eim][SbF₆]）,1-amyl-3-ethyl imidazole antimonate six fluorine ionic liquid（[C₅eim][SbF₆]）,and these products were characterized by ¹H NMR and ESI-MS.In this experiment,the samples were measured with a high-accuracy automatic adiabatic calorimeter imported from Dalian Institute of Chemical Physics Chinese Academy of Sciences.Before the measurement,the calorimeter should be calibrated to ensure the reliability and accuracy of the experimental data.The accuracy of the calorimeter is±0.164%,which is in accordance with the measurement standard.Then,low temperature heat capacities of[C₄mim][SbF₆]、[C₅mim][SbF₆]、[C₆mim][SbF₆]、[C₄eim][SbF₆]and[C₅eim][SbF₆]ionic liquids were measured in the temperature range of 78 K³92 K,78 K³91 K,79 K³93 K,80 K³87 K and 81 K³93 K,respectively.The least square method was used to fit the experimental heat capacities,and the polynomial fitting equation of five alkyl imidazole hexafluoroantimonate ionic liquids were obtained,and the relative deviation between the fitting heat capacities and the experimental heat capacities was calculated.Finally,H_T-H_298.15,S_T-S_298.1598.15 and G_T-G_298.1598.15 of the five ionic liquids in the temperature range of 298.15 K⁴00 K were calculated,and the influence of the length and position of cationic substituent chain on the heat capacity of the ionic liquids in the case of the same anions was discussed.