Phase and Chemical Equilibria of Biphasic Protic Ionic Liquid: Triethylamine–Acetic Acid

Abstract

Triethylamine−acetic acid, as a biphasic protic ionic liquid, typically contains both phase equilibrium and protontransferring chemical equilibrium, and these equilibria have been measured in this work. NMR and IR spectroscopy methods were applied to determine the neutral and ionic species in both lower and upper phases. At 298.15 K, the lower phase contained (25 ± 1) mol % molecular acetic acid, (10 ± 1) mol % molecular triethylamine, and (64 ± 1) mol % ionic species, while the upper phase contained (4.7 ± 0.2) mol % molecular acetic acid, (71.5 ± 0.5) mol % molecular triethylamine, and (24 ± 1) mol % ionic species. The temperature effect on the distributions of molecular and ionic species in biphasic triethylamine−acetic acid was also studied. The unique biphasic PIL containing both base-rich and acid-rich phases with different ionic concentrations (ionicity) should be of significant potential to be applied in industrial processes.

Solvent Effect on the Ionicity of Protic Ionic Liquid: 1-Methylimidazolium-Acetic Acid

“…The 3 mm NMR tube was sealed by the fuse method outside the glovebox. The measuring method used was the same as that reported in our recent work . Each measurement was repeated at least three times.…”

“…The ionicity concept has been recently challenged in the literature. For example, the ionicity was used to explain “the ionic nature of a PIL” or “how many free ions are in a PIL”, and some qualitative and quantitative approaches were also proposed to evaluate it. − In this paper, the ionicity was defined as the degree of proton transfer of a PIL, indicating a chemical equilibrium reaction, and some ionicities of several homogeneous and biphasic PILs have been obtained by spectroscopy methods. ,− …”

“…The measuring method used was the same as that reported in our recent work. 15 Each measurement was repeated at least three times.…”

Protic ionic liquids for sustainable uses

“…43 This is in line with the earlier discussion that it is easy to remove excess base from a PIL, but nearly impossible to remove an excess acid. 19 Finally, some authors have called the entire system a “biphasic ionic liquid”, 66 which is likely an overly liberal use of the term “ionic liquid”. In conclusion, despite the very easy synthetic procedure, it is crucial to adhere to full spectroscopic and thermal characterisation of prepared PILs, to ensure that their composition is correctly understood.…”

Effect of 2‐Pyrrolidone Protic Ionic Liquids on Removal of Pyridine from Fossil Fuel Model Mixtures

“…Typical ApILs can be synthesized by a two-step method, where the intermediate products are first synthesized with an alkylation reaction, and then the intermediate products are subjected to anion exchange [20][21][22]. PrILs can be prepared from Brønsted acids and bases through proton transfer reactions [23], which is more effective to form a hydrogen bond (H-bond) with heterocyclic aromatic compounds [24,25].…”