加盐萃取精馏分离苯-环己烷

Separating benzene-cyclohexane by extractive distillation with salt

测定不同萃取剂和盐对苯-环己烷共沸物相对挥发度的影响,研究不同质量分数的盐和萃取剂与原料液体积比对苯-环己烷体系相对挥发度的影响以及萃取剂加入速率和回流比对加盐萃取精馏的影响,按实验确定的最佳工艺条件进行重复实验。结果表明:采用N,N-二甲基甲酰胺(DMF)作为萃取剂,加入质量分数为15%的KAc,萃取剂与原料液体积比为0.75,萃取剂加入速率为6 mL/min,回流比为3,可得到纯度大于98%的环己烷。与常规萃取精馏相比,加盐萃取精馏所需萃取剂与原料液体积比小,所得环己烷的纯度较高。塔底釜液经减压精馏,可得质量分数大于99.5%的苯和苯质量分数小于0.15%的加盐萃取剂。

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.