Extractive Separation Of Binary Azeotropic Systems Containing Lower Alcohols Using Imidazolium-based Ils

In this paper,the new green solvents ionic liquids(ILs)were used as extractant to separate the azeotropic systems cotaning lower alcohols(water-alcohols,ester-alcohols,alkane-alcohols).The COSMO-SAC model was used to calculate extraction capacity.The liquid-liquid equilibrium(LLE)data for nine different ternary systems were determined by experiments,the values of distribution coefficient and selectivity were calculated according to the experimental data to compare the extraction efficiency of different systems.For the system of alcohol and water,the IL of 1-decyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide([Dmim][NTf2])was used as extractant,the influence of temperature for extraction efficiency was studied,the results illustrate that the higher the temperature,the better the extraction efficiency,but if the temperature is too high,the systems will become homogeneous and the extraction operation cannot be performed.For the system of ester and alcohol,the ILs based on 1-alkyl-3methylimidazolium hexafluorophosphate([Cnmim][PF6])were used as extractant,the influence of alkyl chain length for cation,alcohol and ester on the extraction efficiency was studied.The results show that the longer the alkyl chain length for cation,the better the extraction efficiency.The shorter the alkyl chain length for ester and alcohol,the better the extraction efficiency.For the system of alkane and alcohol,the ILs of 1-hexyl-3-methylimidazolium tetrafluoroborate([Hmim][BF4])and 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide([Hmim][NTf2])were used as extractant,the influence of anion and alkyl chain length for alcohol on the extraction efficiency was studied.The results illustrated that the shorter the alkyl chain length for alcohol,the better the extraction efficiency,and for the same system of alkane and alcohol,the extraction efficiency for [BF4]-anion is better than the [NTf2]-anion.The NRTL and UNIQUAC models were used to correlate the experimental data,the binary interaction parameters which are suitable for the studied system were obtained.The UNIFAC model was used to predict the phase equilibrium data for the alkane-alcohol system,and the predicted resulted was compared with the experimental data to evaluate predictive ability of UNIFAC model.