A New Method For Preparation Of Ionic Liquids

Ionic liquid as an important "green" solvent has become a hot research subject during the past decade. Traditional chemosynthesis methods such as metathesis and acid-base neutralization reactions have been used to prepare ionic liquid. However they have some shortcoming including low product purification, long reaction time at room temperature and the use of ordinary organic solvents, in a certain extent which causes a limitation of further production and application of ionic liquids. Based on the ionic liquid characterization and the electrodialysis (ED) theory, in this study, a new method of electrodialysis was proposed to prepare ionic liquids.Compared to three-compartment electrodialysis via a series of feasible experimental investigations, the four-compartment electrodialysis was preferred to prepare ionic liquids. Operation voltage, feed concentration and the type of ion-exchange membrane had important impacts on the performances of electrodialysis process such as average current efficiency, energy consumption and the product yield. Results showed that the electrodialysis process performance such as the average current efficiency and the product yield in the presence of selemion ion-exchange membrane was better than that in presence of heterogeneous ion-exchange membrane. The effect of operation voltage on the performances of electrodialysis process varied with the feed concentration, but higher operation voltage led to shorter operation time under the same feed concentration. Furthermore, at identical operation voltage, the higher the feed concentration was, the longer the operation time was needed. In order to shorten the operation time and decrease energy consumption, thus the electrodialysis process should be proceeded at a high operation voltage when the feed concentration was high.In a word, the electrodialysis method was more eco-friendly and economic relative to the traditional method of chemical synthesis. Less reaction time was needed though the reaction was taken at the room temperature. Higher purity was obtained by this new method. Especially the electrodialysis process was organic-solvent-free when preparing the water-soluble ionic liquids, and just used water as the solvent.