Flash point prediction of binary mixtures of ionic liquid and flammable solvent

Abstract

In chemical processes, ionic liquids (ILs) are commonly applied in mixtures with flammable solvents. To prevent fire and explosion hazards, flammability data regarding these mixtures are required, but these data are lacking in the literature. Moreover, no flash point prediction models have been developed for IL + solvent mixtures. This study developed a model to estimate the flash point of binary mixtures of ILs with flammable solvents. The model was developed based on fundamental theories of the flash point of mixtures and the contribution of IL decomposition to flammability. The proposed model was validated against empirical measurements of the flash points of mixtures of [C₆mim][Cl] + methanol/ethanol and [Emim][EtSO₄] + methanol/ethanol. Because the model includes the contribution of IL decomposition to flammability, the required activation energy for IL decomposition was estimated from the initial mass loss rate, which was obtained using thermogravimetric analysis. The model predictions agreed well with the empirical data for mixtures with various IL content. The flash point deviations were 5.2–8.3 °C for estimations of solvent nonideality by non-random two-liquid (NRTL) model; this was considered accurate for the wide flash point ranges of the studied mixtures of 142.2–165.4 °C. However, the deviation was large (18.4 °C) for [C₆mim][Cl] + ethanol when the NRTL binary interaction parameters from Carvalho et al. (2013)were used. For mixtures with low IL content and flash points well below the IL flash point, a previously developed binary aqueous–organic solution model also accurately describes the flash point.