Refining method of isophthalonitrile serving as chlorothalonil raw material

Abstract

The invention relates to a refining method of isophthalonitrile serving as a chlorothalonil raw material. The refining method is performed according to the following steps: adding isophthalonitrile and a solvent into a refining kettle provided with a reflux condenser and a tail gas absorber; adding a dehydrant for a dehydration reaction; and carrying out cooling, dropwise adding water for a quenching reaction, then, adding washing water into an organic phase, carrying out stirring and skimming, adding water into the organic phase, carrying out heating for azeotropic distillation, carrying outsolid-liquid separation on a suspension of isophthalonitrile and water, and drying isophthalonitrile. The refining method provided by the invention has the following advantages: 1) the process condition is mild, high temperature and high vacuum degree are not needed, equipment is not blocked and the energy consumption is low; and 2) impurities are directly converted into a product, so that not only are solid wastes generated after refining, but also the amount of the product 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...

AI Technical Summary

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