Molecular level insight on thermal stability of ionic liquids

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Ionic liquids are considered as perspective novel solvents and reaction media. To provide a correct economic assessment of their potential large-scale application at elevated temperatures, the knowledge on thermal stability of ionic liquids is required. The decomposition kinetics, as well as possible decomposition mechanisms and products, are essential information necessary to describe the thermal stability. Most of the available experimental studies of the thermal stability of ionic liquids were carried out by fast scanning in the thermogravimetric technique. The resulting “decomposition temperatures”, decomposition rate constants, and activation energies correspond simultaneously to vaporization and decomposition of an ionic liquid. The subsequent evaluation of the decomposition kinetics, rates, and pathways from such unreliable data become irrelevant to describe the actual thermal stability of ionic liquids. Another problem is the theoretical evaluation of possible decomposition mechanisms and related characteristics. Most theoretical studies employ density functional levels of theory to calculate the difference in the energies in a gas phase at 0 K. Such simplified modeling is far from the finite temperature and phase conditions of ionic liquids decomposition. In this project, we would like to develop and improve the set of experimental setups to distinguishing and quantify the kinetic data of the decomposition and vaporization processes. Also, we would like to provide a deep insight into the molecular level of the thermally initiated decomposition pathways, their rate constants, and activation energies utilizing static and dynamic theoretical methods. The important part of such theoretical analysis is the evaluation of the kinetic parameters in bulk phase and bulk-gas interface. These improvements in experimental and theoretical descriptions will make the results of the decomposition kinetics comparable to each other. As an outcome of the project, the reliable and verified joint experimental and theoretical dataset and protocols will be proposed with simple prediction schemes. These will make possible a quantitative description of decomposition and vaporization rates to provide a reliable assessment of the thermal stability of ionic liquids.