In Situ Variable-Temperature Multi-Nuclear NMR Studies of the Thermal Decomposition Mechanism of Ionic Liquid

doi:10.11938/cjmr20170204

Abstract

Abstract: In situ variable-temperature ¹H, ¹⁹F and ³¹P NMR spectroscopy was employed to study the thermal decomposition mechanisms of ionic liquid. At a temperature as low as 80℃, ionic liquid[C₄mim] [PF₅], composed of 1-butyl-3-methylimidazolium cation (C₄mim⁺) and hexafluorophosphate anion (PF₅^-), had a slow, but detectable decomposition. For dehydrated[C₄mim] [PF₅], the ionic liquid started to decompose at temperature higher than 80℃. Small amount of PF₅ and HF formed first. The proton in HF came from the proton at 2-position of 1-butyl-3-methylimidazolium cation ring. After losing the proton, a carbene structure was formed, which then formed complex with PF₅. Free PF₅ and PF₅/carbene complex reached equilibrium at a ratio of 7:3.

Key words: in situ variable-temperature multi-nuclear NMR, ionic liquid, thermal decomposition mechanism

CLC Number:

O482.53

LI Sen, ZHENG Jun-peng, GUO Ming-ming. In Situ Variable-Temperature Multi-Nuclear NMR Studies of the Thermal Decomposition Mechanism of Ionic Liquid[J]. Chinese Journal of Magnetic Resonance, 2017, 34(2): 156-163.

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