The vapour pressure and the thermal stability of liquids are important material properties. For high boiling organic and ionic liquids (ILs), the determination of these properties is laborious and it is not easy to discriminate between evaporation and thermal decomposition. In this work, a simple but accurate method is presented to determine the parameters of decomposition and evaporation by thermogravimetrical analysis (TGA). The mass transfer coefficient was calculated based on a new correlation for the Sherwood number for cylindrical crucibles in overflow of a carrier gas. This correlation is valid for any diameter-to-height ratio and for any filling degree of the crucible and was derived from numerical simulations and proven by experiments with hexadecane, dodecane, and anthracene. The TGA analysis of two ILs was conducted. [EMIM][EtSO(4)] decomposes at ambient pressure without a measurable contribution of evaporation. To the contrary, [BMIM][NTf(2)] is relatively volatile. The vapour pressure of [BMIM][NTf(2)] and the kinetics of decomposition of both ILs were determined.

Ionic liquids (ILs) are widely discussed as alternative green solvents not only because of their unique chemical properties, but also because of their extremely low vapour pressure and -at least in some cases -relatively high thermal stability. Two complementary methods are analyzed and compared to determine both the rate constant of decomposition and the vapour pressure of four ILs: (1) thermogravimetrical analysis at ambient pressure (TG ap ) with an overflow of inert gases, and (2)

Ionic liquids (ILs) are widely discussed as alternative, sustainable solvents not only because of their unique chemical properties, but also because of their extremely low vapor pressure and – at least in some cases – relatively high thermal stability. In this work the vapor pressure data and kinetics of decomposition are presented for some selected pure and supported ionic liquids. Based on these results general strategies to determine the volatility and stability of pure and supported ILs as well as criteria for the maximum operation temperature with regard to decomposition and evaporation are introduced.

Six hygroscopic ionic liquids (ILs), [DMIM]­[DMPO4], [EMIM]­[MeSO3], [EMIM]­[EtSO4], [EMIM]­[Et­(EG)2SO4], [BMIM]­[BF4], and [choline]­[glycolate], were investigated with regard to their suitability as a drying agent for technical gas dehydration processes by absorption. Therefore, the density, viscosity, activity coefficient of water in the ILs, and the kinetic parameters of thermal and oxidative degradation were measured (if the respective values were not already reported in the literature). [EMIM]­[MeSO3] proved to be the most suitable candidate for industrial gas dehydration. This IL has a low activity coefficient, a high thermal and oxidation stability, an acceptably low viscosity as well as a very low vapor pressure. Thus, the influence of temperature on the activity coefficient of water and the diffusivity of water in this IL was also determined.

The low water vapor pressures of mixtures of water with the ionic liquids (ILs), [EMIM][EtSO 4 ] and [BEIM] [EtSO 4 ], indicate that a process of gas dehydration by absorption in ILs might be an alternative to the classical absorption process with triethylene glycol (TEG). The activity coefficient for an infinite dilution of water in the IL (x IL → 1), which should be low for efficient dehydration, is only about 0.2 for [EMIM][EtSO 4 ] compared to 0.6 for triethylene glycol. In contrast to TEG, losses by evaporation are excluded with ILs as solvents, because they have a negligible vapor pressure. The number of separation stages needed for the absorption in the IL and for the subsequent regeneration of the water-loaded IL is small, about six and eight, respectively. IL regeneration can be achieved by distillation of water out of the IL (e.g., at 120°C) and stripping with ambient air, which is not possible in the case of TEG (chemical attack by O 2 ).

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Continuous gas drying experiments with the hygroscopic ionic liquid [EMIM][MeSO3] show that it can be a very promising alternative drying agent to the absorbent triethylene glycol (TEG) commonly used in industrial gas drying processes. The HTU/NTU model in combination with the correlations of Onda et al. for mass transfer coefficients can be applied for the design of an absorption process with [EMIM][MeSO3]. The major advantage of this ionic liquid (IL) is that well‐known problems associated with the regeneration of the absorbent TEG can be avoided using [EMIM][MeSO3] due to extremely low vapor pressure and possible regeneration with air. The drying capacity of the IL system is about two times higher compared to TEG. Hence, a simple plant design comparable to that of industrial adsorption plants might be applied.