Method for reducing dioxin in preparation of chloranil

Abstract

The invention relates to a method for reducing dioxin in preparation of chloranil. The preparation method of the chloranil comprises the steps of stirring a mixed raw material containing hydroquinoneand an appropriate amount of p-aminophenol for enabling the material to be dissolved in an acetic acid solution, wherein the mass ratio of acetic acid in the acetic acid solution is 20-80wt%, and themass ratio of the mixed raw material to the acetic acid solution is less than or equal to 15 wt%; then, introducing chlorine gas while stirring, carrying out a reaction at 50-90 DEG C, sampling in different periods, and stopping the introduction of the chlorine gas when the melting point of a target material is detected to be higher than or equal to 292 DEG C so as to obtain crystals of the chloranil and crystals of ammonia chloride; adding an appropriate amount of ammonium chloride during first kettle production, wherein the adding amount of the ammonium chloride and the controlling amount ofammonium chloride are the presence of ammonia chloride crystals in mother liquid at the chlorination reaction temperature; after a chlorination reaction is finished, heating up to 60-105 DEG C, wherein the temperature of the chlorination reaction is increased by 10-15 DEG C; filtering the chloranil material when the ammonium chloride salt crystals do not exist, and recovering the mother liquor obtained after filtration for the following use.

Description

1. Technical field [0001] The invention relates to a method for reducing dioxins in the preparation of compounds such as dyes, medicines, and agricultural intermediates, especially in the preparation of chloranil. 2. Background technology [0002] Chlorobenzoquinone, yellow powder, melting point 292°C, commonly used in industries such as pharmaceutical intermediates and permanent violet pigments, and some are exported. Chlorobenzoquinone chemical reaction formula and existing technological process are as follows: [0003] [0004] Raw material consumption: per ton of finished product of chlorobenzoquinone, 0.45 tons of hydroquinone and 1.44 tons of liquid chlorine are required; the mother liquor for chlorine flow is an aromatic hydrocarbon solution, and hydrogen chloride is recovered as hydrochloric acid at the same time. The target material must be washed with water before drying The liquid can be mixed into the mother liquor, and the subsequent water can be recycled. ...

AI Technical Summary

Problems solved by technology

Since the late 1990s, my country has generally adopted the hydroquinone method instead of the phenol method to produce chloranil products. Although the content is lower than the phenol process, it can reach the chemical concentration of dioxin ≤ 100ppb, but it cannot reach the dioxin toxicity equivalent (higher index than the detection chemical concentration) of high-standard products ≤ 100ppt

There is the technology that adopts hydrochloric acid and the organic solvent (such as chlorobenzene, o-dichlorobenzene and p-dichlorobenzene etc.) mixed solution of hydrochloric acid and insoluble in hydrochloric acid to prepare tetrachlorobenzoquinone in the patent disclosed in Japan early stage, these organic solvents of this technology and hydrochloric acid It is not compatible with each other. This is a two-phase solution. Under certain stirring conditions, the distribution of chlorine gas through the solution in the reactor is uniform, so the reaction speed is fast, the reaction efficiency is high, and the dioxin content is low; but due to separation The organic solvent adhering to the material cannot be washed with water. It needs to be washed with a hydrophilic solution such as alcohol and ketone, and then washed with water; After that, it can no longer be reused, so the production cost and wastewater treatment cost are very large

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