2-Ethyl-4-methylimidazolium Alaninate Ionic Liquid: Properties and Mechanism of SO2 Absorption

A functional 2-ethyl-4-methylimidazole alanine ([Emim][Ala]) ionic liquid was synthesized. Its density, viscosity, and surface tension were measured at the temperature range from 293.15 to 343.15 K at atmosphere pressure. The solubility of SO2 in pure [Emim][Ala] ionic liquid and the binary mixture of [Emim][Ala] and water was also investigated. The absorption\desorption mechanism of SO2 was proposed on the basis of 13C nuclear magnetic resonance and Fourier transform infrared spectroscopy. Results showed that SO2 was captured as ammonia sulfonic acid ester by pure [Emim][Ala], while for the binary mixture of [Emim][Ala] and water, the final product of SO2 absorption is alanine and [Emim]+[HSO3]−/[Emim]+2[SO3]2–.