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Method for separating 3, 4-dichloronitrobenzene crystallization mother liquor through extractive distillation

A technology of dichloronitrobenzene and crystallization mother liquor, applied in chemical instruments and methods, preparation of organic compounds, organic chemistry, etc., can solve the problems of increased tar, low oil consumption, low zeolite adsorption capacity, small processing capacity, etc. The effect of small equipment investment, low implementation difficulty and low energy consumption

Active Publication Date: 2013-01-16
JIANGSU YANGNONG CHEM GROUP +1
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

The boiling points of 3,4-dichloronitrobenzene and 2,3-dichloronitrobenzene are 255~256°C and 257~258°C respectively, and they are separated by conventional vacuum distillation method, which has many theoretical plates and high energy consumption
The main problems: low adsorption capacity of zeolite, small processing capacity, frequent regeneration, cumbersome process
However, there are several problems as follows: first, hydrogenation reduction requires a certain cost; second, dechlorination occurs during the reduction process, and tar is produced to increase low oil consumption; third, there are certain limitations in the application of 2,3-DCA obtained by separation, and 2,3-DCNB can be used to produce 2,3,4-trifluoronitrobenzene, an important intermediate of the "third generation" fluoroquinolones ofloxacin and lomefloxacin

Method used

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  • Method for separating 3, 4-dichloronitrobenzene crystallization mother liquor through extractive distillation
  • Method for separating 3, 4-dichloronitrobenzene crystallization mother liquor through extractive distillation
  • Method for separating 3, 4-dichloronitrobenzene crystallization mother liquor through extractive distillation

Examples

Experimental program
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Effect test

Embodiment 1

[0025] Such as figure 1 The separation process shown is composed of an extractive distillation tower and a solvent recovery tower. The extractive distillation tower has 50 theoretical plates (counted from top to bottom). Triethylene glycol is selected as the extraction agent. From the fifth block (from top to bottom), Bottom number) the theoretical plate enters the extractive distillation column, the flow rate is 100kg / h, the low oil enters from the 25th theoretical plate, the low oil composition is 3,4-DCNB 67.2% 2,3-DCNB 32.8%, low oil The flow rate is 50kg / h. The vacuum at the top of the extractive distillation tower is 10mmHg, and the reflux ratio is 2.0:1. At this time, the temperature at the top of the tower is 122.2°C, and the temperature at the bottom of the tower is 182.8-184.7°C.

[0026] The solvent recovery tower has 20 theoretical plates, and the material from the extractive distillation column comes out of the tower tank and enters from the fifth theoretical pla...

Embodiment 2

[0028]Other conditions are the same as in Example 1, tetraethylene glycol is selected as the extractant, the temperature at the top of the extractive distillation tower is 124.8° C., and the temperature at the bottom of the tower is 188.7-193.1° C. The bottom material of the extractive distillation tower enters the solvent recovery tower. The operating pressure of the solvent recovery tower is 7mmHg, the reflux ratio is 1.5:1, the temperature of the top of the tower is 127.0°C, and the temperature of the bottom of the tower is 184.1-191.5°C. The product in the bottom of the solvent recovery tower is returned to the extractive distillation tower for recycling. Under this condition, the gas chromatography analysis results of the extractive distillation tower and the solvent recovery tower top product are shown in Table 1.

Embodiment 3

[0030] Other conditions are the same as in Example 1, 2-naphthyloethanone is selected as the extractant, the temperature at the top of the extractive distillation tower is 124.7°C, and the temperature at the bottom of the tower is 186.5-190.1°C. The bottom material of the extractive distillation tower enters the solvent recovery tower. The operating pressure of the solvent recovery tower is 7mmHg, the reflux ratio is 2.0:1, the temperature at the top of the tower is 126.9°C, and the temperature at the bottom of the tower is 184.3-187.5°C. The product in the bottom of the solvent recovery tower is returned to the extractive distillation tower for recycling. Under this condition, the gas chromatography analysis results of the extractive distillation tower and the solvent recovery tower top product are shown in Table 1.

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Abstract

The invention relates to a method for separating 3, 4-dichloronitrobenzene from 2, 3-dichloronitrobenzene in 3, 4-dichloronitrobenzene crystallization mother liquor. Aiming at the characteristics of small isomer boiling point difference of the 3, 4-dichloronitrobenzene and the 2, 3-dichloronitrobenzene in low oil and difficulty in separation of the conventional method, alcohol, ketone, ester and aromatic hydrocarbon are used as an extraction agent to perform extractive distillation to obtain 3, 4-dichloronitrobenzene and 2, 3-dichloronitrobenzene distillates deviating from eutectic points, so that a foundation is laid for further purification.

Description

technical field [0001] The invention relates to a method for separating 3,4-dichloronitrobenzene and 2,3-dichloronitrobenzene in a 3,4-dichloronitrobenzene crystallization mother liquor, belonging to the technical application field. Background technique [0002] During the production process of preparing 3,4-dichloronitrobenzene (hereinafter referred to as 3,4-DCNB) by nitration of o-dichlorobenzene, 10-15% of 2,3-dichloronitrobenzene (hereinafter referred to as 2,3 -DCNB), more than 99% of 3,4-DCNB is obtained through sweat crystallization in industry, and 3,4-dichloronitrobenzene crystallization mother liquor (commonly known as "low oil" in industry), low oil 3,4- The mass ratio of DCNB to 2,3-DCNB is about 70:30. Normally, 1 ton of pure 3,4-DCNB has about 0.5 tons of low oil. The boiling points of 3,4-dichloronitrobenzene and 2,3-dichloronitrobenzene are 255~256°C and 257~258°C respectively, and they are separated by conventional vacuum distillation method, which has ma...

Claims

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Application Information

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IPC IPC(8): C07C205/11C07C201/16
Inventor 杨树斌徐林丁克鸿唐琴申高忠顾志强缪荣荣李斌任海兵沈杰杨帆
Owner JIANGSU YANGNONG CHEM GROUP
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