Transport properties of nitrile and carbonate solutions of [P66614][NTf2] ionic liquid, its thermal degradation and non-isothermal kinetics of decomposition

The electrical conductivity, density and diffusion coefficients of trihexyl(tetradecyl)phosphonium bis(trifluoromethylsulfonyl)amide ([P66614][NTf2]) ionic liquid and its binary solutions in acetonitrile, propionitrile, dimethyl and diethyl carbonates were measured in the temperature range of 293 – 348 K. Electrical conductivity – ionic liquid mole fraction dependencies for the binary solutions were fitted with the empirical Casteel−Amis equation. The temperature dependencies of electrical conductivities were analyzed using the Arrhenius, Litovitz and Vogel-Fulcher-Tammann approaches. The activation energies and pre-exponential factor calculated using the Arrhenius equation for different mole fractions of ionic liquid were fitted with the empirical equations proposed in the literature. The thermo-gravimetric analysis combined with mass spectrometry demonstrated the high thermal stability of [P66614][NTf2] up to 600 K. At higher temperatures the decomposition of [P66614][NTf2] proceeds via the elimination of alkyl radicals as a result of the nucleophilic attack of reactive intermediates to [P66614]+ cation with the formation of trialkylphosphines. The activation energies of thermal destruction of [P66614][NTf2] were calculated using Kissinger equation and non-linear integral isoconversional model.