Abstract:

The thermal stability, equilibrium vapor pressure, and standard enthalpy of vaporization of 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim][BF4]) ion liquid were investigated using both non-isothermal and isothermal thermogravimetric analysis (TGA) under high purity nitrogen as a carrier gas. The non-isothermal thermogravimetric (TG) curve showed that the onset and peak decomposition temperatures were 697 and 734 K, respectively. However, long-term isothermal TGA studies revealed that the highest application temperature for [bmim][BF4] was 513 K. Moreover, the temperature dependence of the equilibrium vapor pressure and the standard enthalpy of vaporization of [bmim][BF4] were also investigated by TG-based transpiration. In the temperature range of 503-543 K, the relationship between the equilibrium vapor pressure (pe) of [bmim][BF4] and temperature was lgpe=(16±1)+(-6.85±0.25)×103/T. The standard enthalpy of vaporization (△vapHΘ) of [bmim][BF4] was found to be (131±5) kJ·mol-1.

Key words: Ionic liquid, 1-Butyl-3-methylimidazoliumtetrafluoroborate, Thermal stability, Equilibrium vapor pressure, Standard enthalpy of vaporization