Abstract
Amine-functionalized ionic liquids (ILs) have potential applications for CO2 capture. The CO2 capture process is generally operated at a relatively high temperature for a long term, so determining the thermal stability of amine-functionalized ILs is important. In this study, the thermal stability of an amine-functionalized IL 1,2-dimethyl-(3-aminoethyl) imidazolium tetrafluoroborate [aEMMIM][BF4] was investigated by thermogravimetric analysis (TGA), thermogravimetric mass spectroscopic analysis (TG-MS), 1H nuclear magnetic resonance (NMR) experiments and density function theory (DFT) calculation. Amine-functionalization was found to reduce the thermal stability of [aEMMIM][BF4] compared to the non-functionalized counterpart. Besides that, we found that [aEMMIM][BF4] favors a unimolecular substitution nucleophilic (SN1) decomposition reaction rather than bimolecular nucleophilic substitution (SN2) reaction. Vaporization and elimination processes are negligible due to amine functionalization. Moreover, an operational temperature, Toper, is proposed for evaluating the thermal stability of ILs. Results show that Toper of [aEMMIM][BF4] only reaches 138°C, much less than that of the onset decomposition temperature, Tonset (284°C). Evaluating thermal stability of amine-functionalized ILs by Toper is more practical than by Tonset.
Published Version
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