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A method for continuous purification of 2-chloro-5-picoline by rectification-crystallization coupling process

A picoline and process technology, applied in the field of continuous purification of 2-chloro-5-picoline by simple rectification plus crystallization coupling process, can solve the problem of not being able to significantly improve the purity of 2-chloro-5-picoline Purification by rectification method, harsh selection of extractant, etc., to achieve the effect of increasing the difficulty of separation, improving the efficiency of separation and purification, and reducing the difficulty of operation

Active Publication Date: 2021-08-03
JIANGSU YANGNONG CHEM GROUP +3
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

During the production process of 2-chloro-5-picoline, isomeric 2-chloro-3-picoline will be generated. The relative volatility of the two is low, and the boiling point is close, so it is difficult to purify by rectification
The publication number is CN1403181A, and the invention patent titled "method for extracting and distilling 2-chloro-5-picoline and 2-chloro-3-picoline" uses extractive distillation to separate 2-chloro-5-methylpyridine Basepyridine and 2-chloro-3-picoline, using dihydric alcohol or trihydric alcohol as extraction agent for continuous separation, for extractive distillation, the selection of extraction agent is very harsh, and can not significantly improve the 2-chloro-3-methylpyridine The purity of 5-picoline, and the separation of the extractant in the later stage, the process is cumbersome and the operation is difficult
Xuan Richeng et al. (Journal of Zhejiang University of Technology, 2003, 31 (2): 208-211) by adopting the method for forming copper chloride complexes, first 2-chloro-5-picoline from the mixture with the complex The form is separated, and then the complex is hydrolyzed to obtain 2-chloro-5-picoline with a purity of 99.1%, but the copper salt complexation method will bring a high concentration of salt to the system and the saline wastewater is difficult to treat

Method used

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  • A method for continuous purification of 2-chloro-5-picoline by rectification-crystallization coupling process
  • A method for continuous purification of 2-chloro-5-picoline by rectification-crystallization coupling process
  • A method for continuous purification of 2-chloro-5-picoline by rectification-crystallization coupling process

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Experimental program
Comparison scheme
Effect test

Embodiment 1

[0027] Precipitation: The toluene-extracted oil layer was introduced into a desolventization distillation unit at a rate of 1000 g / h, and the content of 2-chloro-5-picoline in the extracted oil layer was 33.45%. Use a stirring device to make the solution have a stable gasification center, control the liquid phase temperature at 60-120°C, keep the vacuum at 5-15kPa, control the gas phase temperature at 20-40°C, and the reflux ratio of 2-3 to extract light component solvents , the output flow rate is 471g / h, and the composition of the solvent is 96.67% toluene and 3.01% dichloroethane. The heavy component is extracted at a certain flow rate, and the coke removal process shows that the content of 2-chloro-5-picoline is 63.2%.

[0028] Decoking: The desolventized material enters the decoking distillation system at a flow rate of 528g / h, and at the same time, the filtered mother liquor from the washing and separation step is added at a certain flow rate. Control the liquid phase t...

Embodiment 2-6

[0035] On the basis of Example 1, change the layer crystallization freezing temperature, sweating heating rate, sweating end point temperature, the obtained results are as follows:

[0036]

Embodiment 7-11

[0038] On the basis of example 5, change suspended crystal residence time, suspended crystal cooling temperature, sweating duration, obtained result is as follows:

[0039]

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Abstract

The invention provides a combination process of simple rectification-crystallization coupling, which is used to continuously remove isomers and other impurities in crude 2-chloro-5-picoline to achieve the purpose of high purification. Specifically, the extracted oil layer of 2-chloro-5-picoline is used as the starting material, and concentrated fractions are obtained through desolvation, decoking, and rectification, and then high-purity 2‑Chloro‑5‑picoline method.

Description

technical field [0001] The invention belongs to the technical field of petrochemical industry, and relates to a method for continuously purifying 2-chloro-5-picoline through a coupling process of simple rectification and crystallization. Background technique [0002] 2-Chloro-5-picoline is an important intermediate in the production of pesticides such as imidacloprid and ethimiprid (Acetamiprid). The creation of pesticides in my country and the pharmaceutical industry provide a useful intermediate, which provides an important raw material for the creation of successor varieties of heterocycles. During the production of 2-chloro-5-picoline, isomeric 2-chloro-3-picoline will be produced. The two have relatively low volatility and close boiling points, so it is difficult to purify by rectification. [0003] At present, the main separation methods of 2-chloro-5-picoline and 2-chloro-3-picoline include high vacuum distillation, extractive distillation, copper salt complexation, a...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): C07D213/61
CPCC07D213/61
Inventor 王刚张曦王根林丁克鸿徐林许越郭玉秀王浩廖强
Owner JIANGSU YANGNONG CHEM GROUP