A method and device for separating a mixture of toluene and ethanol

Abstract

The invention provides a method for separating toluene and ethanol mixture, comprising the steps of: (1) extracting ethanol in toluene with saline water, and then refining toluene with ordinary rectification; (2) extracting step (1) with xylene ) containing salt, water, ethanol, trace amount of toluene in the mixture of trace amounts of toluene, and the mixture containing xylene, toluene, trace amount of ethanol goes to step (1); (3) extracting step (2) containing salt, water, The ethanol in the ethanol mixture is separated from xylene and ethanol by ordinary rectification, and the water and salt mixture of ethanol are removed and recycled in step (1); (4) the xylene obtained by toluene refining and ethanol refining is reused. The method has complete separation and low energy consumption.

Description

technical field [0001] The invention belongs to the field of separation of chemical products, and relates to a method for separating a mixture of toluene and ethanol, in particular to a method for separating a mixture of toluene and ethanol by combining extraction, rectification, and salt addition. Background technique [0002] In chemical and pharmaceutical production processes, toluene and lower aliphatic alcohols are often used as solvents. For example, in the production processes of avermectin refining and liquid crystal intermediates, ethanol and toluene are used as solvents together. After use, these solvents It is used as a waste solvent and sent to a solvent recovery device for recovery. However, toluene and ethanol form an azeotrope. To obtain high-purity toluene and ethanol products at the same time, it cannot be achieved by ordinary distillation. Extractive distillation or azeotropic distillation is often used. Separation by the method, such as Hou Tao et al (extr...

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Problems solved by technology

[0002] In chemical and pharmaceutical production processes, toluene and lower aliphatic alcohols are often used as solvents. For example, in the production processes of avermectin refining and liquid crystal intermediates, ethanol and toluene are used as solvents together. After use, these solvents It is used as a waste solvent and sent to a solvent recovery device for recovery. However, toluene and ethanol form an azeotrope. To obtain high-purity toluene and ethanol products at the same time, it cannot be achieved by ordinary distillation. Extractive distillation or azeotropic distillation is often used. Separation by the method, such as Hou Tao et al (extractive distillation simulation and optimization of toluene-ethanol azeotropic system, Journal of Petrochemical Universities, 2008, 25 (4): 21-23, 28), studied the use of n-butylbenzene For the process of solvent extraction and rectification to separate toluene and ethanol, Zhang Huan et al. (Economic optimization design of pressure swing rectification separation toluene-ethanol system, Energy and Chemical Industry, 2014, 35(6): 31-34) studied pressure swing refinery Distillation and separation of toluene and ethanol; however, the investment and process energy consumption of these processes are relatively large

There is also the use of water as the extractant to extract ethanol from toluene. However, due to the presence of ethanol, the solubility of toluene to water increases, and the solubility of water to toluene also increases. Therefore, although the ternary system of toluene, ethanol, and water It can separate phases, but toluene still contains a large amount of ethanol and water, and water also contains a large amount of toluene, while toluene and water, water and ethanol, ethanol and toluene form a binary azeotrope, and toluene, ethanol, and water form a ternary azeotrope Boilers, so separation is difficult and consumes a lot of energy

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