About the Purification Route of Ionic Liquid Precursors

Abstract

In this work a purification route of precursors for ionic liquids tailored to electrochemical energy storage systems is reported and described. The study was carried out on the N-butyl-N-methylpyrrolidinium bromide (PYR14Br) precursor, which represents the intermediate product of the synthesis process of the N-butyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide (PYR14TFSI) hydrophobic ionic liquid. The target is to develop an easy and cost-effective approach for efficiently purifying several kinds of ionic liquid precursors and determining their purity content. The PYR14Br precursor was synthesized through an eco-friendly preparation procedure, which requires water as the only processing solvent, and purified through sorbent materials, such as activated charcoal and alumina. The effect of the treatment/nature/content of sorbents and processing temperature/time was investigated. The impurity content was detected by UV-VIS spectrophotometry measurements. Additionally, a correlation between the measured absorbance and the content of impurities within the precursor was obtained. The purity level of the precursor was seen to play a key role in the electrochemical performance of the ionic liquids.