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Separation of benzene and cyclohexane is one of the mostimportantand difficult processes in the petrochemical industry, especiallyfor low benzene concentration. In this work, three ionic liquids (ILs),[Bmim][BF4], [Bpy][BF4], and [Bmim][SCN], wereinvestigated as the solvent in the extraction of benzene from cyclohexane.The corresponding ternary liquid–liquid equilibria (LLE) wereexperimentally determined at T= 298.15 K and atmosphericpressure. The LLE data were correlated with the nonrandom two-liquidmodel, and the parameters were fitted. The separation capabilitiesof the ILs were evaluated in terms of the benzene distribution coefficientand solvent selectivity. The effect of the IL structure on the separationwas explained based on a well-founded physical model, COSMO-RS. Finally,the extraction processes were defined, and the operation parameterswere analyzed. It shows that the ILs studied are suitable solventsfor the extractive separation of benzene and cyclohexane, and theirseparation efficiency can be generally ranked as [Bmim][BF4] > [Bpy][BF4] > [Bmim][SCN]. The extraction processfora feed with 15 mol % benzene was optimized. High product purity (cyclohexane0.997) and high recovery efficiency (cyclohexane 96.9% and benzene98.1%) can be reached. [ABSTRACT FROM AUTHOR]

Abstract: In order to screen ionic liquids (IL) as suitable solvents for the separation of benzene and cyclohexane, the extraction efficiency of ILs (12 cations and 22 anions) was estimated based on COSMO-RS predictions of infinite dilution activity coefficients of benzene and cyclohexane in different ILs..[C4mim][AlCl4] was found to be the most promising solvent. To provide deep insight on how the IL structure influences the extraction efficiency, molecular interactions between IL ions and benzene were determined from DFT calculations. Moreover, liquid–liquid equilibrium data of the ternary system benzene–cyclohexane—[C4mim][AlCl4] were experimentally determined and used to fit parameters of the NRTL activity coefficient model. Based on the NRTL model the continuous extraction process was simulated and compared with a reference process using sulfolane as solvent. For the extraction process using [C4mim][AlCl4], high cyclohexane product purity (99.65wt%) and high benzene recovery efficiency (98.03%) can be reached with at much lower energy consumption and higher product yield compared to conventional extraction solvents. In conclusion, the ionic liquid [C4mim][AlCl4] is a promising solvent for the extractive separation of benzene and cyclohexane. [Copyright &y& Elsevier]

Abstract: In order to screen ionic liquids (IL) as suitable solvents for the separation of benzene and cyclohexane, the extraction efficiency of ILs (12 cations and 22 anions) was estimated based on COSMO-RS predictions of infinite dilution activity coefficients of benzene and cyclohexane in different ILs..[C4mim][AlCl4] was found to be the most promising solvent. To provide deep insight on how the IL structure influences the extraction efficiency, molecular interactions between IL ions and benzene were determined from DFT calculations. Moreover, liquid–liquid equilibrium data of the ternary system benzene–cyclohexane—[C4mim][AlCl4] were experimentally determined and used to fit parameters of the NRTL activity coefficient model. Based on the NRTL model the continuous extraction process was simulated and compared with a reference process using sulfolane as solvent. For the extraction process using [C4mim][AlCl4], high cyclohexane product purity (99.65wt%) and high benzene recovery efficiency (98.03%) can be reached with at much lower energy consumption and higher product yield compared to conventional extraction solvents. In conclusion, the ionic liquid [C4mim][AlCl4] is a promising solvent for the extractive separation of benzene and cyclohexane. [Copyright &y& Elsevier]

Abstract: In the catalytic hydrogenation of benzene to cyclohexane, the separation of unreacted benzene from the product stream is inevitable and essential for an economically viable process. In order to evaluate the separation efficiency of ionic liquids (ILs) as a solvent in this extraction processes, the ternary (liquid+liquid) equilibrium of 1-alkyl-3-methylimidazolium hexafluorophosphate, [C n mim][PF6] (n =4, 5, 6), with benzene and cyclohexane was studied at T =298.15K and atmospheric pressure. The reliability of the experimentally determined tie-line data was confirmed by applying the Othmer–Tobias equation. The solute distribution coefficient and solvent selectivity for the systems studied were calculated and compared with literature data for other ILs and sulfolane. It turns out that the benzene distribution coefficient increases and solvent selectivity decreases as the length of the cation alkyl chain grows, and the ionic liquids [C n mim][PF6] proved to be promising solvents for benzene–cyclohexane extractive separation. Finally, an NRTL model was applied to correlate and fit the experimental LLE data for the ternary systems studied. [Copyright &y& Elsevier]