阅读说明：本技术 一种回收乙酸乙酯、正丁醇和正庚烷的废溶剂的方法 (Method for recovering waste solvent of ethyl acetate, n-butanol and n-heptane ) 是由 李向峰 李星星 高豹 黄安宁 桂园芬 马刚 王成林 于 2020-07-10 设计创作，主要内容包括：本发明公开了一种回收乙酸乙酯、正丁醇和正庚烷的废溶剂的方法,包括以下步骤：(1)将溶剂中水分的质量含量降低,得到只含有乙酸乙酯-正丁醇-正庚烷的混合物；(2)将所述乙酸乙酯-正丁醇-正庚烷的混合物通入第一精馏塔进行共沸精馏,塔釜得到正丁醇,塔顶为乙酸乙酯和正庚烷的共沸混合物；(3)将所述乙酸乙酯和正庚烷的共沸混合物通入第二精馏塔,加入萃取剂与离子液体组成的混合萃取剂,进行萃取精馏,塔顶得到正庚烷,塔釜为乙酸乙酯和混合萃取剂的混合物；(4)将所述乙酸乙酯和萃取剂的混合物连续通入溶剂回收塔,塔顶得到乙酸乙酯,塔釜为混合萃取剂。本发明能够高效分离乙酸乙酯、正丁醇和正庚烷。(The invention discloses a method for recovering a waste solvent of ethyl acetate, n-butanol and n-heptane, which comprises the following steps: (1) reducing the mass content of water in the solvent to obtain a mixture only containing ethyl acetate-n-butanol-n-heptane; (2) introducing the mixture of ethyl acetate, n-butanol and n-heptane into a first rectifying tower for azeotropic rectification, wherein n-butanol is obtained at the tower bottom, and the azeotropic mixture of ethyl acetate and n-heptane is obtained at the tower top; (3) introducing the azeotropic mixture of ethyl acetate and n-heptane into a second rectifying tower, adding a mixed extractant consisting of an extractant and an ionic liquid, and carrying out extractive distillation to obtain n-heptane at the tower top, wherein the mixture of ethyl acetate and the mixed extractant is in the tower kettle; (4) and continuously introducing the mixture of the ethyl acetate and the extracting agent into a solvent recovery tower, obtaining the ethyl acetate at the tower top, and obtaining the mixed extracting agent at the tower bottom. The invention can efficiently separate ethyl acetate, n-butanol and n-heptane.)

1. A method for recovering waste solvents of ethyl acetate, n-butanol and n-heptane, comprising the steps of:

(1) reducing the mass content of water in the solvent to less than 1% to obtain a mixture containing only ethyl acetate-n-butanol-n-heptane;

(2) introducing the mixture of ethyl acetate-n-butanol-n-heptane obtained in the step (1) into a first rectifying tower for azeotropic rectification, wherein n-butanol with the content of more than 99% is obtained at the tower bottom, and the azeotropic mixture of ethyl acetate and n-heptane is obtained at the tower top;

(3) introducing the azeotropic mixture of ethyl acetate and n-heptane obtained in the step (2) into a second rectifying tower, adding a mixed extracting agent consisting of an extracting agent and an ionic liquid, and carrying out extractive distillation to obtain n-heptane with the content of more than 99% at the tower top and a mixture of ethyl acetate and the mixed extracting agent at the tower bottom;

(4) and (4) continuously introducing the mixture of the ethyl acetate and the extracting agent obtained in the step (3) into a solvent recovery tower for separation, wherein the ethyl acetate with the content of more than 99% is obtained at the top of the tower, and the mixed extracting agent is obtained at the bottom of the tower.

2. The method for recovering a waste solvent of ethyl acetate, n-butanol and n-heptane as set forth in claim 1, wherein the step (1) of reducing the mass content of water in the solvent to less than 1% is carried out by continuously passing the water through a molecular sieve to remove the water from the waste solvent.

3. The process for recovering a used solvent of ethyl acetate, n-butanol and n-heptane as claimed in claim 1, wherein in the step (2), the azeotropic distillation is carried out under the conditions of atmospheric pressure, the temperature of the bottom of the column is 115 to 125 ℃, the temperature of the top of the column is 64 to 68 ℃ and the reflux ratio is 3 to 5.

4. The method for recovering waste solvent of ethyl acetate, n-butanol and n-heptane as described in claim 1, wherein in the step (3), the extractive distillation is carried out under conditions of a pressure of 1atm, a column bottom temperature of 130 to 160 ℃, a column top temperature of 45 to 65 ℃ and a reflux ratio of 3 to 5.

5. The method for recovering a used solvent of ethyl acetate, n-butanol and n-heptane as described in claim 1, wherein in the step (3), the mass ratio of the mixed extractant to the azeotropic mixture of ethyl acetate and n-heptane is 1.0 to 2.0.

6. The method for recovering a waste solvent of ethyl acetate, N-butanol and N-heptane according to claim 1 or 5, wherein the ionic liquid is N-methylpyridine dimethyl phosphate.

7. The method for recovering waste solvent of ethyl acetate, N-butanol and N-heptane according to claim 1 or 5, wherein the extractant is p-xylene or N-methylpyrrolidone.

8. The method for recovering waste solvent of ethyl acetate, n-butanol and n-heptane as described in claim 1, wherein in the step (4), the separation is carried out under a pressure of 1atm, a column bottom temperature of 150 to 170 ℃, a column top temperature of 40 to 60 ℃ and a reflux ratio of 3 to 5.

Technical Field

The invention relates to the field of chemical rectification and purification, in particular to a method for recovering a waste solvent of ethyl acetate, n-butanol and n-heptane.

Background

At present, ethyl acetate, n-butanol and n-heptane are widely applied in the fields of rubber, pharmacy, paint and the like, are often used as organic solvents in large quantities, and other substances, particularly water, are inevitably added in the using process. The mixed solvent like this has little harm to the environment, and is difficult to recover and difficult to handle due to more azeotropic components. In order to reduce environmental pollution and save resources, the waste liquid of the mixture needs to be recycled and utilized.

Under normal pressure, the n-butanol and water can form an azeotrope, the azeotropic temperature is 92.7 ℃, and the n-butanol in the azeotropic composition is: water 0.575: 0.425 (mole fraction), and ethyl acetate is also capable of forming a binary azeotrope with n-heptane having an azeotropic temperature of 75.75 ℃ and an azeotropic composition of n-heptane: ethyl acetate 0.265 (mole fraction). The ethyl acetate and the n-heptane azeotropic system can not be efficiently separated by adopting common rectification, and particularly n-butanol and various azeotropic components are contained in the waste solvent.

Therefore, it is desirable to provide a novel method for recovering waste solvents of ethyl acetate, n-butanol and n-heptane to solve the above problems.

Disclosure of Invention

The invention aims to provide a method for recovering waste solvents of ethyl acetate, n-butanol and n-heptane, and solves the problems that the mixture forms more azeotropes and the direct distillation cannot achieve the maximum utilization of waste recovery. According to the invention, the azeotropic composition of the waste solvent is found, water is removed firstly, and then the azeotropic distillation and the extractive distillation are combined, so that the ethyl acetate, the butanol and the n-heptane can be completely separated, and the high-efficiency separation is realized. Meanwhile, the invention adopts the mixed extractant composed of the common extractant and the ionic liquid, and can greatly reduce the loss of the common solvent, reduce the production cost, reduce the pollution to the environment and have good economic benefit based on the advantages of the ionic liquid.

In order to solve the technical problems, the invention adopts a technical scheme that: provided is a method for recovering a waste solvent of ethyl acetate, n-butanol and n-heptane, comprising the steps of:

(1) reducing the mass content of water in the solvent to less than 1% to obtain a mixture containing only ethyl acetate-n-butanol-n-heptane;

(2) introducing the mixture of ethyl acetate-n-butanol-n-heptane obtained in the step (1) into a first rectifying tower for azeotropic rectification, wherein n-butanol with the content of more than 99% is obtained at the tower bottom, and the azeotropic mixture of ethyl acetate and n-heptane is obtained at the tower top;

(3) introducing the azeotropic mixture of ethyl acetate and n-heptane obtained in the step (2) into a second rectifying tower, adding a mixed extracting agent consisting of an extracting agent and an ionic liquid, and carrying out extractive distillation to obtain n-heptane with the content of more than 99% at the tower top and a mixture of ethyl acetate and the mixed extracting agent at the tower bottom;

(4) and (4) continuously introducing the mixture of the ethyl acetate and the extracting agent obtained in the step (3) into a solvent recovery tower for separation, wherein the ethyl acetate with the content of more than 99% is obtained at the top of the tower, and the mixed extracting agent is obtained at the bottom of the tower.

In a preferred embodiment of the present invention, the method of reducing the mass content of water in the solvent to less than 1% in step (1) removes water from the spent solvent by continuous passage through a molecular sieve.

In a preferred embodiment of the present invention, in the step (2), the azeotropic distillation is carried out under the conditions of atmospheric pressure, the temperature of the bottom of the column is 115 to 125 ℃, the temperature of the top of the column is 64 to 68 ℃, and the reflux ratio is 3 to 5.

In a preferred embodiment of the present invention, in the step (3), the extractive distillation is carried out under conditions of a pressure of 1atm, a column bottom temperature of 130 to 160 ℃, a column top temperature of 45 to 65 ℃ and a reflux ratio of 3 to 5.

In a preferred embodiment of the present invention, in the step (3), the mass ratio of the mixed extractant to the azeotropic mixture of ethyl acetate and n-heptane is 1.0 to 2.0.

Further, the ionic liquid is N-methylpyridine dimethyl phosphate.

Further, the extractant is p-xylene or N-methylpyrrolidone. The solvent selection principle and the UNIFAC group contribution method are used for screening N-methyl pyrrolidone as an extracting agent for extraction and rectification, and meanwhile, the N-methyl pyrrolidone can break azeotropy through an ethyl acetate-N-heptane system under normal pressure and a gas-liquid balance experiment after the extracting agent N-methyl pyrrolidone is added. Similarly, p-xylene can break the azeotrope between ethyl acetate and n-heptane.

Further, the weight ratio of the extracting agent to the ionic liquid is 40-60%.

In a preferred embodiment of the present invention, in the step (4), the separation is carried out under a pressure of 1atm, at a column bottom temperature of 150 to 170 ℃, at a column top temperature of 40 to 60 ℃ and at a reflux ratio of 3 to 5.

The invention has the beneficial effects that:

(1) the invention comprises reducing the mass content of water in the waste solvent to below 1%, breaking the azeotropic composition with water, separating and recovering ethyl acetate, butanol and n-heptane by the continuous rectification method combining azeotropic rectification and extractive rectification, wherein the content of the recovered product reaches more than 99%;

(2) the extracting agent adopts a mixed extracting agent formed by the extracting agent and the ionic liquid, so that the extraction efficiency can be improved; the extractant breaks the azeotropy between ethyl acetate and n-heptane, and the ionic liquid is added to make up the defects of the organic solvent due to the characteristics of ultralow vapor pressure, good stability, high boiling point, recycling and the like of the ionic liquid, so that the energy consumption of the organic solvent is reduced. Based on the advantages of low melting point, easy operation, good solubility and the like of the ionic liquid, the rectification process usually adopts the mixed solution of common organic solvent and the ionic liquid as an extracting agent, so that the loss of the common solvent can be greatly reduced, the cost is reduced, and the quality is improved.

Detailed Description

The invention is further illustrated with reference to the following specific examples, which are not intended to be limiting.