Separation of Ethyl Acetate−Ethanol Azeotropic Mixture Using Hydrophilic Ionic Liquids

The separation of ethyl acetate and ethanol (EtOH) is important but difficult due to their close boiling points and formation of an azeotropic mixture. The separation of the azeotropic mixture of ethyl acetate and EtOH using the hydrophilic ionic liquids (ILs) 1-alkyl-3-methylimidazolium chloride (alkyl = butyl, hexyl, and octyl) ([Cnmim]Cl, n = 4, 6, 8) and 1-allyl-3-methylimidazolium chloride and bromide ([Amim]Cl and [Amim]Br) has been investigated. Triangle phase diagrams of five ILs with ethyl acetate and EtOH were constructed, and the biphasic regions were found as follows: [Amim]Cl > [Amim]Br > [C4mim]Cl > [C6mim]Cl > [C8mim]Cl. The mechanisms of the ILs including cation, anion, and polarity effect were discussed. The results showed that the hydrophilic ILs [Cnmim]Cl (n = 4, 6, 8), [Amim]Br, and [Amim]Cl could remove EtOH effectively from the azeotropic mixture of ethyl acetate and EtOH. Moreover, it was found that [Amim]Cl had the highest extraction efficiency, and the purity of ethyl acetate could reach 99.27 wt % after extraction twice. These hydrophilic ILs are easily synthesized and purified, are economically feasible, and caused no erosion to the equipment, which usually happened for ILs containing F. ILs could be recycled by simple distillation. The separating process can reduce the energy consumption greatly, and the total process is green and environmentally benign.