Long-term thermal stability of selected ionic liquids in nitrogen and hydrogen atmosphere

Approximately 30 ionic liquids with different cations and anions were manufactured and tested for their thermal stability. In addition to common cations (e.g., imidazolium and ammonium), novel cations such as several dications, a bicyclic amine, a benzimimidazolium, and an inorganic cation were applied. All liquids were heated to the desired temperature by applying a constant heating rate of 3 K/min. After the heating period, the temperature was held for at least 6 h in a nitrogen-atmosphere. Some ionic liquids based on the [NTf2]-anion tend to be stable up to 250 °C or even 300 °C in \{N2\} atmosphere. In particular, imidazolium and pyrrolidinium dicationic ionic liquids show a high thermal stability. The salt [Li][NTf2], which provides an inorganic cation, decomposes at temperatures between 250 and 300 °C. Additionally and with respect to technical application, the effect of hydrogen and nickel on the thermal stability of \{ILs\} was studied. Both nickel and hydrogen reduce the thermal stability, whereas the effect of hydrogen on the thermal stability of \{ILs\} is drastic.