Separation Of Azeotropic System Containing Alcohol By Using Imidazole ILs As Extractants Based On Hydrogen Bonding Mechanism And Process Optimization

In the process of fine chemical and pharmaceutical production,multi-component complex mixtures containing low-carbon alcohols will be produced,which makes the separation process of low-carbon alcohols system challenging.In this paper,imidazole ionic liquids(ILs)were used as extractants to separate three azeotropic systems of cyclohexane tert butyl alcohol,isopropyl ether isopropanol and n-heptane-n-propanol by liquid-liquid extraction.A multi-scale optimization method of extractants was proposed by coupling molecular simulation calculation,liquid-liquid equilibrium experiment and liquid-liquid extraction process design.The interaction mechanism between ILs and azeotrope components to be separated during extraction was studied.Based on COSMO-SAC model,the data group of?-profiles of ILs and low-carbon alcohol azeotropes was calculated to analyze the hydrogen bond distribution between the ILs and the extracted substances;At the same time,the total charge density,differential charge density,interaction energy,reduced density gradient function,electrostatic potential and hydrogen bond length between imidazole ILs and extracted substance were calculated based on quantum chemistry calculation.The optimal extractants for separating cyclohexane tert butyl alcohol,isopropyl ether isopropanol and n-heptane-n-propanol were determined as[BMIM][NTF₂],[EMIM][DCA]and[DMIM][MP]respectively.The phase equilibrium data of cyclohexane/tert butyl alcohol/imidazole ILs([BMIM][NTF₂],[BMIM][HSO₄],[BMIM][OTF])and isopropyl ether/isopropyl alcohol/Imidazole ILs([BMIM][OTF],[EMIM][OTF],[EMIM][DCA])were determined at 298.15 K and 1 atm.The binary interaction parameters were obtained by NRTL and UNIQUAC model regression data.The root mean square error(rmsd)was less than 0.02,and the experimental data passed the consistency test.The selectivity and partition coefficient of imidazole ILs were calculated.The results showed that[bmim][NTF2]was the best extractant for separating cyclohexane/tert butyl alcohol system,and the selectivity and partition coefficient were 11.8772 and 2.2470,respectively.[EMIM][DCA]was the best extractant for the separation of isopropyl ether/isopropyl alcohol system,with selectivity and partition coefficient of 15.0774 and 2.0355,respectively.Based on the binary interaction parameters of NRTL,the liquid-liquid extraction process was simulated and optimized with the objective of minimizing the total annual cost.The minimum annual cost of separating 8000 t/year cyclohexane/t-butanol system is 1.118×10⁵ dollars/year.The minimum annual cost of separating 8000 t/year isopropyl ether/isopropyl alcohol system is 1.265×10⁵ dollars/year.Based on the binary interaction parameters of NRTL,the liquid-liquid extraction process was simulated and optimized with the objective of minimizing the total annual cost.The minimum annual cost of separating cyclohexane/tert butyl alcohol system is1.118×10⁵$/year.The minimum annual cost of separating isopropyl ether/isopropyl alcohol system is 1.265×10⁵$/year.