Thermal decomposition behaviors of imidazolium-type ionic liquids studied by pyrolysis-gas chromatography.
Thermal decomposition behaviors of a series of imidazolium-type ionic liquid samples were studied by pyrolysis-gas chromatography at 550 degrees C using various detectors. As for the imidazolium halides, haloalkanes and 1-alkylimidazoles corresponding to the alkyl substituents were mainly formed through the nucleophilic attacks of halide ions to the alkyl groups followed by C-N bond cleavage, along with a minor amount of alkenes. Meanwhile, in the case of the ionic liquids with BF(4), PF(6) and CF(3)SO(3) anions, corresponding alkenes were predominantly produced along with 1-alkylimidazoles rather than haloalkanes. No boron-containing products were found even from the samples with BF(4) anion, whereas minor but clear peaks of phosphorous-containing products were observed in the pyrograms of the samples with PF(6) anions. As for the samples with longer alkyl group, the pyrolyzates reflecting the C-C bond scissions in the alkyl groups were also formed to some extent. Meanwhile, imidazole rings did not decompose under the experimental conditions at around 550 degrees C.
Department of Materials Science and Engineering, Graduate School of Engineering, Nagoya Institute of Technology, Japan. ohtani.hajime@nitech.ac.jp
Hajime
H
Ohtani
Shinji
S
Ishimura
Miyuki
M
Kumai