用亲水性离子液体分离乙酸乙酯和乙醇 SEPARATIONS Separation of Ethyl Acetate-Ethanol Azeotropic Mixture Using Hydrophilic Ionic Liquids Dong L. Zhang,2,3 Yue F. Deng,2 Chuan B. Li,3 and Ji Chen*,2 Key laboratory of Rare Earth Chemistry and Physics, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun, 130022, China, and College of Chemistry, Jilin Normal UniVersity, Siping, 136000, China The separation of ethyl acetate and ethanol (EtOH) their close boiling points and formation of is important but difficult due to an the azeotropic mixture of ethyl acetate and azeotropic mixture. The separation of EtOH (ILs) using the hydrophilic chloride (alkyl 1-alkyl-3-methylimidazolium ionic liquids ) butyl, hexyl, and octyl) (C1-allyl-3-methylimidazolium nmimCl, n ) 4, 6, 8) and bromide been investigated. Triangle phase diagrams (AmimCl and Amim-Br) chloride and has of were constructed, and the biphasic regions five ILs with ethyl acetate and EtOH were found as follows: AmimCl > AmimBr > C4mimCl > C6mimCl > Cincluding cation, anion, and polarity effect 8mimCl. The mechanisms of the ILs were discussed. The results showed that the 8), hydrophilic remove AmimBr, ILs CnmimCl (n ) 4, 6, azeotropic EtOH and effectively AmimCl from could the EtOH. AmimCl Moreover, mixture of it ethyl was acetate and efficiency, could twice. reach and had the highest found extraction that 99.27 the purity wt % of ethyl acetate synthesized and purified, are economically These hydrophilic after ILs are extraction easily feasible, equipment, which usually happened for ILs and caused no erosion to the containing simple F. can distillation. ILs The could separating be recycled process by greatly, reduce and the the total energy process consumption environmentally benign. is green and potential Ionic liquids (ILs) have been widely recognized negligible vapor pressure, nonflammability, thermal stabilization, environmentally friendly solvents because as green and of their high dissolving ability for both polar and nonpolar compounds,1-3 and many variations of both cation and anion conformations.4 have been studied for chemical synthesis,5-7 ILs controlled processing of polymer materials,8 versatile diverse technologies, 9-14electrolytes for catalysis, and extraction processes.15-26 hydrogen-bonded solvents and have strong solvent effects on The imidazolium-based ILs are highly ordered chemical reactions and processes. Thus, the ability of a solute to form hydrogen bonds or other possible interactions with potential solvents is an important feature of their behavior.27 Therefore, the traditional volatile organic compounds (VOCs) to separate using imidazolium-based ILs as replacements for azeotropic extractive dimixtures and as an alternative to conventional of such ILs are shown in Table 1.stillation has been investigated widely; examples Although imidazolium-based ILs have shown a wide range of application in azeotropic mixture separation, some practical drawbacks cannot be neglected. First, the synthesis processes of some ILs listed in Table 1 are complex, such as C2mim-EtSOTable 4. Both the hydrophilic and hydrophobic ILs listed in 1 are prepared following standard procedures by metath- * To whom correspondence should be addressed. Tel.: +86-431-8526-2646. Fax: +86-431-8526-2646. E-mail: jchenciac.jl.cn.2 3 Chinese Academy of Science. Jilin Normal University. mixture systemstypes of ILreftoluene and heptaneC2mimI3, C4mimI319gasline octane boostersC2mimEtSO 21ethanol and heptanemimPF4 C623 1-hexene and trans-3-hexene mimPF6 C46, iBemimBF4 25 aromatic hydrocarbons and alkanes C2mimNTf2 26 esis or ion exchange of ILs containing halide anion with corresponding anions, which result in higher preparation prices.4 Second, ILs are required to be biodegradable or incinerable. In both cases F materials are undesirable.28 Finally, the higher viscosities of the hydrophobic ILs make the operating processes discommodious in practice. Compared with the ILs listed in Table 1, the hydrophilic ILs containing chloride and bromide anions, such as 1-alkyl-3-methylimidazolium chloride (alkyl ) butyl, hexyl, and octyl) (CnmimCl; n ) 4, 6, 8) and 1-allyl-3-methylimidazolium chloride and bromide (AmimCl and AmimBr) in this investigation, are easily prepared through one simple step, and are relatively lower in price and environ-mentally acceptable. The excellent properties of the hydrophilic ILs make them have extensive and practical applications in cellulose dissolution29,30 and azeotropic mixture separation. 31,32 The boiling points of ethyl acetate, EtOH, and their mixture are 78.5, 77.06, and 71.8 ?C, respectively. EtOH cannot be separated from the mixture of ethyl