CN1238318C - Process for separating ethandiol, mono methyl ether, isopropyl alcohol and water combined by extracting and axeotropy - Google Patents

Abstract

The present invention relates to a process for separating ethylene glycol monomethyl ether, isopropyl alcohol and water by the combination of extraction and azeotropy, which comprises the following procedures that glycerol and benzene are respectively used as an extraction agent of extractive distillation and an azeotropic agent of azeotropic distillation, a mixed solution of isopropyl alcohol, water and ethylene glycol monomethyl ether is separated by adopting a distillation apparatus, after separation, isopropyl alcohol and water are obtained at tower top, and water and ethylene glycol monomethyl ether are obtained at tower bottom; a distillate at the tower top is separated by an extractive distillation method, and glycerol is adopted as the extraction agent; after extractive separation, ethylene glycol monomethyl ether and water at the tower bottom are fed into an azeotropic distillation apparatus, and benzene is adopted as the azeotropic agent and is circularly used in the azeotropic apparatus. By adopting the method of the present invention, the content of isopropyl alcohol and ethylene glycol monomethyl ether after separation can reach more than 99.5%. After separation, the content of isopropyl alcohol and ethylene glycol monomethyl ether contained in water is lower than 0.23%, ethylene glycol monomethyl ether acetate can be obtained in one step. After separation, isopropyl alcohol is circularly used, ethylene glycol monomethyl ether can be returned to the raw material, and thus, no environment pollution is caused.

Description

Method for combining extraction and azeotropic separation of ethylene glycol monomethyl ether, isopropanol and water

technical field

The invention relates to a chemical separation process, in particular to a separation method combining extraction and azeotropy of ethylene glycol monomethyl ether, isopropanol and water.

Background technique

With the rapid development of my country's economic construction, people's demand for high-grade paint and coating solvent - ethylene glycol monomethyl ether acetate is increasing. It is estimated that the current annual demand is about 1 million tons, while the domestic annual output is only 100,000 tons. The production of ethylene glycol monomethyl ether acetate is mainly based on acid (solid acid or inorganic acid) as catalyst, and ethylene glycol monomethyl ether and acetic acid are used as catalysts for the production of ethylene glycol monomethyl ether acetate. The raw material adopts solid acid or inorganic acid as catalyst. In the synthesis process, excessive acetic acid or ethylene glycol monomethyl ether is generally used. The method of using excessive acetic acid is mature in all aspects and has been industrialized. However, excessive ethylene glycol monomethyl ether is used. Agent (isopropanol), water-carrying agent and ethylene glycol monomethyl ether and water all can form azeotrope, form the azeotrope and composition of azeotrope as shown in Table 1, substance Azeotropic temperature (°C) Azeotropic composition water + isopropanol 80.3°C 12.6% water, 87.4% isopropanol Water + ethylene glycol monomethyl ether 99.9°C 15.3% water, 84.7% ethylene glycol monomethyl ether

The azeotrope produced is (isopropanol + water + ethylene glycol monomethyl ether), therefore, whether isopropanol + water + ethylene glycol monomethyl ether can be effectively separated is related to the excess of ethylene glycol monomethyl ether Whether the law can be industrialized. At present, the separation of isopropanol+water+ethylene glycol monomethyl ether in industrial production generally uses desiccants (such as CaCl ₂ ) to dehydrate first, and then adopts rectification to separate isopropanol and ethylene glycol monomethyl ether. In industrial production The slurry produced by CaCl _dehydration is difficult to regenerate, and 2-3% (mass ratio) of isopropanol and ethylene glycol monomethyl ether are entrained in the slurry, which not only wastes resources, but also easily causes certain problems to the environment.

Contents of the invention

The invention adopts extraction and azeotropic phase combination method to separate isopropanol+water+ethylene glycol monomethyl ether, and after separation, isopropanol is recycled and ethylene glycol monomethyl ether can be returned to raw materials.

The technical scheme for completing the above-mentioned invention task is: use glycerin and benzene as the extractant of extractive distillation and the entrainer of azeotropic distillation, first adopt rectification device to separate the mixed solution of isopropanol+water+ethylene glycol monomethyl ether, After separation, the tower top is isopropanol+water, and the tower bottom is water+ethylene glycol monomethyl ether; Extractant, after extraction and separation, the water content of isopropanol can be reduced to less than 0.5%; the bottom ethylene glycol monomethyl ether + water is sent to the azeotropic distillation device, using benzene as the entrainer, and benzene circulates in the azeotropic device Using an azeotropic device can reduce the water content of ethylene glycol monomethyl ether to below 0.5%, therefore, ethylene glycol monomethyl ether can be returned to the raw material for reuse. The process flow of the separation process is shown in Figure 1. During the separation process, each device adopts optimized process conditions. After separation, the water content of isopropanol and ethylene glycol monomethyl ether can be removed to less than 0.5%, which can meet the requirements of recycling.

Advantages of the present invention: using the process shown in Figure 1 and optimized process parameters, the raw material isopropanol + water + ethylene glycol monomethyl ether, firstly separate T-1 through a rectification tower, and then extract the top and bottom of the tower respectively The device T-2 is separated from the azeotropic device T-3, and the content of isopropanol and ethylene glycol monomethyl ether can reach more than 99.5% after separation; the content of isopropanol and ethylene glycol monomethyl ether in the separated water is lower than Below 0.23%, compared with the currently used method, in the synthesis process of ethylene glycol monomethyl ether acetate, the excess ethylene glycol monomethyl ether and the reaction water can be separated at one time, and ethylene glycol monomethyl ether can be obtained at one time. Ether acetate, the isopropanol + water + ethylene glycol monomethyl ether azeotrope separated during the reaction process is separated by the extraction device and the azeotrope device, and can be recycled, which is not easy to cause problems to the environment.

In the separation process using the above method, each device adopts optimized process conditions, and the water content of isopropanol and ethylene glycol monomethyl ether can be removed to less than 0.5% after separation.

Description of drawings

Fig. 1 The technological process of combining extraction and azeotropy.

Detailed ways

The method of extraction and azeotropic separation of ethylene glycol monomethyl ether, isopropanol and water, with reference to the process shown in Figure 1 and the parameters shown in Table 2, raw material (F1) is ethylene glycol monomethyl ether+isopropanol+water Mixed liquid, the mass content of ethylene glycol monomethyl ether, isopropanol and water (Xf1, Xf2, Xf3) is 10%, 50%, 40% respectively, flow rate is 4.1Kg/h, precision rectifying tower T-1 top , low temperature are 80.4 ℃ and 87.5 ℃ respectively, the flow rate is 2.7Kg/h, 1.4Kg/h respectively, precision rectification column top reflux ratio (R1) is controlled at 4～6, the top and bottom composition of the column (x _Di , x _wi ) x _D1 =0.0000, x _D2 =0.7592, x _D3 =0.2407, x _w1 =0.2929, x _w2 =0.0000 x _w3 =0.7071; the tower top component is sent to the extractive distillation unit (T-2), and the extractant ( Glycerin) and the raw material ratio are 2.5: 1, and the top reflux ratio R2 is controlled at 4～6, and 99.6% isopropanol can be obtained at the top of the extractive distillation tower, and the extractant rich in water at the bottom of the tower is sent to the regeneration tower for regeneration, and then circulates Use; the precision rectification tower bottom stream is sent to the azeotrope device T-3, using benzene as the entrainer, after the blending tower overhead distillate is condensed by the condenser, the benzene layer is refluxed, the water layer is discharged, and the azeotrope tower More than 99.5% of ethylene glycol monomethyl ether can be obtained at the end. In the figure, 1, 4, 5, 8 are condensers; 3, 11 are reboilers; 2 is rectification tower; 6 is extraction tower; 7 is regeneration tower; 9 is stratified reflux tank; 10 is azeotrope tower . ①～⑨ are the names of streams (see Table 2).

Table 1 Process conditions of each tower T-1 Tower T-2 tower T-3 tower T-4 Tower ① Feed position reflux ratio (R ₁ ) Number of trays Tower top temperature (°C) Tower bottom temperature (°C) 274-65680.587-89 ② Feed position S Feed position Reflux ratio (R2) Number of trays Tower top temperature (°C) Tower bottom temperature (°C) 73114-58982-83137-141 ③ Feed position reflux ratio (R3) Number of trays Tower top temperature (°C) Tower bottom temperature (°C) 153-53169-100125-127 ④ Feed position reflux ratio Number of plates Tower top temperature (°C) Tower bottom temperature (°C) 194-53799-101167-171

Table 2 Separation Results stream name Flow(Kg/h) Composition (mass content) Isopropanol water Ethylene glycol monomethyl ether glycerin benzene ①②③④⑤⑥⑦⑧⑨ Raw material liquid (F ₁ ) tower T-1 Top discharge tower T-2 Top discharge tower T-2 Bottom discharge tower T-4 Top discharge tower T-4 Bottom discharge tower T-1 Bottom discharge tower T -3 top discharge tower T-3 bottom discharge 4.102.702.067.390.636.761.41.040.36 0.50120.76110.99680.00020.0023//// 0.41030.23890.00320.08640.99770.00150.74080.99920.0021 0.0885/////0.2592/0.9979 ///0.9133/0.9985/// ///////0.0008/

Claims (1)

1, a kind of extraction and azeotropic the steps include: in conjunction with the method for separating ethylene glycol monomethyl ether, Virahol and water

Adopting glycerine is the extraction agent of extracting rectifying, and adopting benzene is the entrainer of component distillation,

Adopt rectifier unit separating isopropanol+water+ethylene glycol monomethyl ether mixing solutions, after the separation, cat head is Virahol+water, is water+ethylene glycol monomethyl ether at the bottom of the tower;

Overhead distillate is delivered to the extracting rectifying device and is separated, and employing glycerine is extraction agent;

After the extracting and separating, ethylene glycol monomethyl ether+water is delivered to the component distillation device at the bottom of the tower, and employing benzene is entrainer, and benzene recycles in the azeotropic device.

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