Thermal stability of low temperature ionic liquids revisited

The range of thermal stability of low temperature ionic liquids published in the literature (often >400 ◦C) is severely overrated. The decom-
position temperature calculated from fast TGA scans in a protective atmosphere does not imply a long-term thermal stability below that temper-
ature. Even at temperatures as low at 200 ◦C, 1-alkyl-3-methylimidazolium phosphates (alkyl = C4–C10) and 1-decyl-3-methylimidazolium
triflate showed a slow, but appreciable mass loss. On the other hand, 1-butyl-3-methylimidazolium triflate was stable at 200 ◦C. The carboniza-
tion occurred in most studies salts irrespectively of the nature of the anion (hexafluorophosphate, triflate), but the salts with a shorter side chain
(C4) did not show changes in their color after conditioning for 10 h at 200 ◦C in air. 1-Butyl-3-methylimidazolium triflate shows extremely
good wettability against aluminum oxide and silver at elevated temperatures. Addition of silica (amorphous or quartz) accelerates the thermal
decomposition of 1-alkyl-3-methylimidazolium phosphates and triflates at 200 ◦C, while the effect of other ceramic powders (titania, alumina)
is less significant.