Efficient separation of methyl ethyl ketone and water azeotrope using hydrophobic amino acid ester ionic liquids

Abstract

Background

Methyl ethyl ketone (MEK), an essential organic solvent, is commonly produced via the n-butene method, where water emerges as the principal impurity. The conventional distillation processes, which are necessitated by the azeotropic behavior between MEK and water, result in a substantial expenditure of energy. As a result, liquid-liquid extraction represents a promising alternative for energy-efficient separation.

Methods

In this work, three hydrophobic amino acid ester ionic liquids L-phenylalanine ethyl ester bis(trifluoromethylsulfonyl) imide ([Phe][NTf₂]), L-leucine ethyl ester bis(trifluoromethylsulfonyl) imide ([Leu][NTf₂]) and L-valine ethyl ester bis(trifluoromethylsulfonyl) imide ([Val][NTf₂]) were utilized as extractants for separation of the binary azeotrope methyl ethyl ketone and water. The effects of extraction time, extraction temperature, mass ratio of MEK-water mixture to ionic liquid and initial concentration of MEK on extraction efficiency were investigated.

Significant findings

The results demonstrate that the ionic liquid [Phe][NTf₂] exhibits superior extraction ability for the separation of the azeotrope methyl ethyl ketone and water. The maximum extraction yield of 99.86 % was achieved with the optimum extraction conditions of extraction time, 10 min, extraction temperature, 293.15 K, mass ratio of mixture to ionic liquid, 1:1 and initial concentration of MEK, 20 %. In addition, the relationship between the structure of ionic liquids and their extraction performance was revealed by quantum chemical calculations of ionic liquids with MEK and water. These ionic liquids were positioned as promising environmentally friendly alternatives to traditional organic solvents for the recovery of MEK from aqueous solutions, providing valuable insights for industrial applications.