The vapour pressure and thermal stability of ionic liquids (ILs) are important properties with regard to their application as solvents or homogeneous catalysts, where evaporation losses and the maximum allowable operation temperature to exclude decomposition should be well-known. This is not only true for pure ILs but also for supported ILs, e.g. used for the Solid Catalyst with Ionic Liquid Layer (SCILL) technology.Decomposition temperatures commonly reported as the onset of mass loss during thermogravimetric analysis should be handled with caution. Decomposition may already start at lower temperatures, e.g. if the treatment time is extended to a couple of hours. Hence, the kinetics of decomposition should be measured to quantify the mass loss at a certain temperature within a certain time span, e.g. 1% mass loss per year.ILs have extraordinary low vapour pressures. The amount of vapour pressure data is still limited, mainly because the determination is so onerous and decompo-si-tion may take place at temperatures, where the vapour pressure gets measurable with usual techniques.Regarding evaporation/decomposition of supported ILs, systematic investigations have not been published until just recently based on own ambient pressure thermogravimetrical analysis and high vacuum experi-ments with a magnetic suspension balance.The following ILs were used for the experiments on evaporation and decomposition of pure ILs: [DMIM][DMPO4], [EMIM][NTf2], [BMIM][NTf2], [EMIM][MeSO3], [EMIM][CF3SO3], and [EMIM][EtSO3]. For the supported systems, experiments with [DMIM][DMPO4], [EMIM][NTf2], and [EMIM][MeSO3] on silica as well as on a commercial Ni-catalyst were conducted.The presented results are attempts to give answers to at least three questions: (1) What is the best strategy to determine the vapour pressure and the kinetics of thermal degradation of pure and supported ILs, (2) Is the mass loss by evaporation altered for supported ILs compared to pure melts, and (3) does the support enhance or suppress decomposition.

Thermal stability and evaporation of pure and supported ionic liquid phases

248th National Meeting (2014)

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