Application Of Deep Eutectic Solvents In Extractive Distillation Of Benzene And Cyclohexane

It is the most difficult to separate benzene-cyclohexane binary components in aromatics and non-aromatics separation field and also has been one of the hot topics in the field of petrochemical separation.Extractive distillation is the common method in aromatics and aromatics separation process,the general extraction agent is dimethyl sulfoxide,sulfolane,et al.,but there are many disadvantages of extractant,such as relative large usage,volatility,high energy consumption,high investment.Therefore,the study of green and efficient extractant is a research hotspot in this field.The structure and properties of deep eutectic solvents can be changed according to the combination of hydrogen bond donor and hydrogen bond acceptor,there it has great potential in extractive distillation field.Three deep eutectic solvents(DES1,DES2 and DES3)are prepared in this work.The physical properties and structure of the deep eutectic solvents are systematically studied.And they were used in benzene-cyclohexane-extractant vapor-liquid phase equilibrium experiments under the atmospheric pressure at room temperature.The results showed that the best extractant was DES1,the best molar ratio for hydrogen bond acceptor and hydrogen bond donor was 1:2 and the optimum molar concentration is 0.1(solvent ratio,0.263).The extractive distillation effect of prepared deep eutectic solvents was evaluated:the relative volatility of ternary system with DES1(1:2)(0.1)is greater than 1 in all the range of concentration(?>1),having the best extraction effect.Three thermodynamic models(NRTL,Wilson,and UNIQUAC)were used to fit vapor-liquid phase equilibrium data.According to the result of correlation index R2,the best applicable thermodynamic model is NRTL and its model parameters were obtained:in the system of benzene-cyclohexane-DES1(1:2)(0.1),R2 is 0.8771;binary interaction parameters of NRTL model is:Aij,17.895;Aji,26.168;Bij,10000;Bji,-10000;Cij,0.1717(i=cyclohexane,j=benzene).Infrared spectrum and nuclear magnetic resonance spectrum show that the deep eutectic solvent which has extraction effect has hydrogen bonding and ?-? interaction with benzene,this interaction can break benzene and cyclohexane azeotrope.The deep eutectic solvent which has no extraction effect has weak hydrogen bonding and?-? interaction interaction with benzene and the interaction can not break the azeotrope.Therefor,deep eutectic solvent screening result was verified.