A kind of refining method of chlorothalonil raw material isophthalonitrile

Abstract

The present invention relates to a kind of refining method of chlorothalonil raw material isophthalonitrile, described refining method is carried out according to the following steps: add isophthalonitrile and solvent in the refining kettle with reflux condenser and tail gas absorption tower; add Dehydration reaction of dehydrating agent; cool down, add water dropwise to quench the reaction, add washing water to the organic phase to stir and separate liquid, add water to the organic phase, heat up azeotropic distillation, separate the suspension of isophthalonitrile and water through solid-liquid separation, Phthalonitrile drying. The refining method proposed by the present invention has the following advantages: 1) Mild process conditions, no need for high temperature and high vacuum, no blockage of equipment, and less energy consumption 2) Directly transform impurities into products, which not only avoids solid hazardous waste after refining, but also The quantity of products is increased, and the economic benefit is high.

Description

technical field [0001] The invention relates to the field of pesticides, in particular to a method for refining chlorothalonil raw material isophthalonitrile. Background technique [0002] Chlorothalonil, i.e. tetrachloroisophthalonitrile, is a broad-spectrum, low-toxicity, low-residue, protective fungicide for agriculture and forestry. It has dual functions of prevention and treatment, long-lasting and stable, and can be used for wheat , rice, vegetables, fruit trees, peanuts, tea and other crops; in industry, it can be used as an antifungal agent for coatings, electrical appliances, leather, paper, cloth, etc. In industry, isophthalonitrile is used as raw material, chlorine gas is used as chlorinating agent, catalyzed by supported catalyst, high-temperature gas phase reaction is carried out in fixed-bed and fluid-bed reactors, and after the reaction is completed, it enters the trap for desublimation to obtain chlorothalonil product. [0003] Isophthalonitrile is industri...

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Problems solved by technology

But there are obvious disadvantages in this method: 1) Since the boiling point of isophthalonitrile is as high as 288°C, higher temperature and vacuum are required for distillation, and the highest distillation temperature is above 250°C. Since the melting point of isophthalonitrile is 163- 165°C, during the distillation process, it is very easy for the material to solidify and block the pipeline. The equipment needs to be dredged and cleaned frequently, resulting in low production efficiency

2) The solid residue produced after the distillation is a mixture of amide impurities, residual isophthalonitrile, and impurities generated by the decomposition of isophthalonitrile during high-temperature distillation, which cannot be recycled and can only be used as hazardous waste processing, which pollutes the environment and increases material consumption

[0005] In addition to distillation, isophthalonitrile can also be refined by recrystallization, but recrystallization is also a physical method like distillation, and the main impurities in isophthalonitrile, m-cyanobenzamide and m-cyanobenzamide, are not purified. Phthalamide is converted into isophthalonitrile by chemical reaction, and the solid residue produced after the solvent is recovered after refining is cyanobenzamide, isophthalamide, residual isophthalonitrile and other trace impurities as Hazardous waste treatment is not optimal in terms of clean production and cost savings

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