气液萃取精馏分离乙二醇中的高碳数杂醇

Separation of high-carbon-number diols from ethylene glycol bygas-liquid extractive distillation

二元醇混合物的分离是生物质基乙二醇工业应用的重要环节,但传统精馏技术的分离效率较低。通过引入气态萃取剂,使其与特定组分之间发生相互作用,选择性地促进这些组分的气化,从而提高精馏的分离效率。实验结果表明:一方面气态正丁醇与气膜内部及相界面处的丙二醇、丁二醇分子发生较强的相互作用,有效地促进了丙二醇、丁二醇从液相到气相的传质过程;另一方面,由于正丁醇与乙二醇的极性相差较大、相互作用较弱,其对乙二醇分子从液相到气相的迁移的促进作用较弱,故无助于乙二醇的气化。这种选择性促进作用使塔顶的丙二醇、丁二醇浓度得以提升,从而强化了精馏分离效果。在气态正丁醇的作用下,初始馏出物中丙二醇的质量分数从43%提高到50%,丁二醇的质量分数从14%提高到17%。与传统的萃取精馏技术相比,气液萃取精馏的萃取剂夹带量少,且所夹带的萃取剂易于去除,设备简单,能耗较低。本研究为特种精馏技术的发展提供了新思路。

The separation of mixed diols is a major challenge for the industrial application of biomassderived ethylene glycol,and traditional distillation techniques are inefficient in the separation of mixed diols.A gaseous extractant was introduced to strongly interact with specific components to selectively promote the gasification of these components,thereby improving the separation efficiency of distillation process.The experimental results showed that the gaseous n-butanol interacted strongly with propanediol and butanediol molecules in the gas film and at the interface between phases,effectively promoting the mass transfer of propanediol and butanediol from the liquid to gas phase.On the other hand,due to the large difference in polarity and weak interaction between gaseous n-butanol and ethylene glycol,the promotion effect of gaseous n-butanol on the migration of ethylene glycol molecules from the liquid to gas phase was too weak to facilitate the gasification of ethylene glycol.This selective promotion effect elevated the top concentrations of propanediol and butanediol.Therefore,the separation efficiency was improved,and distillation process was intensified.With the effect of gaseous n-butanol,the mass concentration of propanediol in the initial distillate was increased from 43%to 50%,and that of butanediol was increased from 14%to 17%.Compared with the traditional extractive distillation technique,the quantity of extractant entrained in the gas-liquid extractive distillation is small,and extractant entrained is readily to remove.The equipment is simple with relatively low energy consumed.This study is beneficial for the development of special distillation techniques.