Studies Of Ionic Liquids By Imidazolium Thermogravimetry Technique

Ionic liquids (ILs) are salts typically comprised from the combination of large organic cations with various substituents (alkyls, oligoethers, etc.) and inorganic or organic anions. As a replacer of versatile organic solvents, room ionic liquids are attracting scientist's more attention. In this dissertation, the properties of ionic liquids,which the thermal stability, equilibrium vapor pressure, tandard enthalpy of vaporization (ΔvapH°) or standard enthalpy of sublimation (ΔsubH°), apparent activation energy (Eact) and decomposition kinetics of imidazolium ionic liquids, were investigated using both non-isothermal and isothermal thermogravimetric analysis (TGA) under high pure nitrogen as carrier gas. Moreover, The effect of procedural variables on the decomposition was investigated. In this work, the procedural variables included heating rate and gas environment.The onset and the highest use temperature of 1-carboxyalkyl-3-methylimidazolium chloride ([cmmim]Cl) were 547 and 433 K, respectively. At the temperature range of 406-463 K, the relationship between temperature and equilibrium vapor pressure of [cmmim]Cl was ( )The standard enthalpy of sublimation (ΔsubH°) and isothermal vaporization activation energy (Eact) of [cmmim]Cl were found to be 52±1 kJ·mol^-1 and 53±2 kJ·mol^-1, respectively. The parameters of mechanism were: the best fit model was Cn which corresponds to the nth order reaction with auto catalysis, the reaction order was 1.33 and the function f(α) was f (α) = (1 -α)1 .33(1 + 1.5635)α. ddαT =βA e?RET(1 ?α)1 .33(1 + 1.5635)α,E=16 5kJ·mol^-1,A=1.23×1013 s^-1。Thermal stability, equilibrium vapor pressure, standard enthalpy of vaporization (ΔvapH°), apparent activation energy (Eact) and decomposition kinetics of 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim][BF4]) were investigated using both non-isothermal and isothermal thermogravimetric analysis (TGA) under high pure nitrogen as carrier gas. The onset and the highest use temperature of [bmim][BF4] were 697 and 513 K, respectively. At the temperature range of 503-543 K, the relationship between temperature and equilibrium vapor pressure of [bmim][BF4] was lgpe=(16±1)+(-6.85±0.25)×103/T. The standard enthalpy of vaporization (ΔvapH°) and isothermal vaporization activation energy (Eact) of [bmim][BF4] were found to be 131±5 kJ mol?1 and 147±10 kJ·mol^-1, respectively.The parameters of mechanism were: the best model was Cn which corresponds to the nth order reaction with auto catalysis, Thermal stability, equilibrium vapor pressure, standard enthalpy of vaporization (ΔvapH°), apparent activation energy (Eact) and decomposition kinetics of 1-butyl-3-methylimidazolium dihydrogenphosphate ([bmim][H2PO4]) were investigated using both non-isothermal and isothermal thermogravimetric analysis (TGA) under high pure nitrogen as carrier gas. The onset and the highest use temperature of [bmim][H2PO4] were 548 and 433 K, respectively. At the temperature range of 503-543 K, the relationship between temperature and equilibrium vapor pressure of [bmim][H2PO4] was ( )The standard enthalpy of vaporization (ΔvapH°) and isothermal vaporization activation energy (Eact) of [bmim][H2PO4] were found to be 121±7 kJ·mol^-1 and 123±6 kJ·mol^-1, respectively.The parameters of mechanism were: the best model was Cn which corresponds to the nth order reaction with auto catalysis,Thermal stability, equilibrium vapor pressure, standard enthalpy of vaporization (ΔvapH°), apparent activation energy (Eact) and decomposition kinetics of 1-butyl-3-methylimidazolium dicyanamide ([bmim][N(CN)2]) were investigated using both non-isothermal and isothermal thermogravimetric analysis (TGA) under high pure nitrogen as carrier gas. The onset and the highest use temperature of [bmim][N(CN)2] were 476 and 383 K, respectively. At the temperature range of 353-403 K, the relationship between temperature and equilibrium vapor pressure of [bmim][N(CN)2] was lg ( pe mPa ) = 10±1+ ? (2.461±T0.055)×103. The standard enthalpy of vaporization (ΔvapH°) and isothermal vaporization activation energy (Eact) of [bmim][N(CN)₂] were found to be 47±1 kJ·mol^-1 and 50±1 kJ·mol^-1, respectively.。The parameters of mechanism were: the best model were Fn which corresponds to the nth order reaction and Cn which corresponds to the nth order reaction with auto catalysis,n=2.77,respectively. ddαT =βA e?RET(1 ?α)₂.77and dd , respectively, E=149 kJ·mol^-1,A=9.77×1012 s^-1. Thermal stability, equilibrium vapor pressure, standard enthalpy of vaporization (ΔvapH°), apparent activation energy (Eact) and decomposition kinetics of 1-allyl-3-methylimidazolium dicyanamide ([amim][N(CN)₂]) were investigated using both non-isothermal and isothermal thermogravimetric analysis (TGA) under high pure nitrogen as carrier gas. The onset and the highest use temperature of [amim][N(CN)₂] were 551 and 443 K, respectively. At the temperature range of 503-543 K, the relationship between temperature and equilibrium vapor pressure of [amim][N(CN)₂] was lg ( pe mPa ) = 14±1+ ? (4.85±T0.16)×10³. The standard enthalpy of vaporization (ΔvapH°) and isothermal vaporization activation energy (Eact) of [amim][N(CN)₂] were found to be 93±3kJ·mol^-1 and95±4 kJ·mol^-1, respectively.。The parameters of mechanism were: the best model was Cn which corresponds to the nth order reaction with auto catalysis , n=1.70 ,This paper has two innovations. The first one, the long-term thermal stability of the five ILs were studied by the long-term isothermal thermogravimetric analysis (TGA) under high pure nitrogen as carrier gas for the first time, and the studies showed that the long-term stable temperature significantly lower than the onset decomposition temperature determined from scanning TGA experiments.The second, the temperature dependence of equilibrium vapor pressure and standard enthalpy of vaporization (sublimation) and apparent activation energy of the five ILs were investigaged by TG-based transpiration technique for the first time.In this paper, the thermal stability, equilibrium vapor pressure, standard enthalpy of vaporization (sublimation), apparent activation energy (Eact) and decomposition kinetics of imidazolium ionic liquids, was studied by thermogravimetry technique, and the effect of the heating rate and gas environment on the thermal decomposition was also investigated, which can provide useful information for high temperature applications which often require extended operations at elevated temperatures and negligible vapor pressure.