Separating benzene-cyclohexane by extractive distillation with salt

The influence of different extractant and salt on the relative volatility of benzene-cyclohexane azeotrope was determined. The effect of different mass fraction of salt and volume ratio of extractant to solvent on the relative volatility of benzene-cyclohexane systems and the influence of adding rate of extractant and reflux ratio on the extractive distillation with salt were studied. The experiment was repeated according to the experimental determination of optimum process conditions. The investigation shows that the cyclohexane with a purity of more than 98% can be obtained when dimethyl formamide (DMF) is as extractant, with adding rate of 6 mL/min, mass fraction of KAc added is 15%, volume ratio of extractant to solvent is 0.75, and reflux ratio is 3. Compared with the regular extractive distillation, the extractive distillation with salt can get a higher purity of cyclohexane with less volume ratio of extractant to solvent. By vacuum rectification of the bottoms, the benzene with mass fraction more than 99.5% and extractant with salt with the mass fraction of benzene less than 0.15% can be obtained.