Production method of EDTA

Abstract

The invention discloses a production method of EDTA (ethylenediaminetetreacetic acid). The production method is characterized by preparing EDTA by taking sodium cyanide, ethanediamine, formaldehyde and liquid caustic soda as raw materials and comprises the following steps: (1) condensation reaction: adding part of a sodium cyanide solution, a liquid caustic soda solution and ethanediamine into a condensation reaction kettle, then starting stirring, then switching on a steam regulating valve, then increasing the temperature to 88-95 DEG C, dropwise adding formaldehyde and the remaining sodium cyanide solution, condensing the tail gas generated in the reaction process and absorbing the tail gas under negative pressure, adding hydrogen peroxide after the reaction is ended, and decolorizing to obtain a condensed material; (2) acidification reaction: adding the condensed material into an acidification reaction kettle, starting stirring, opening an acidification condenser, adding return water into the acidification condenser, adding hydrochloric acid into a reaction kettle till the pH of the reaction kettle is 2.1-4, carrying out centrifugal separation on the precipitated crystal to obtain an EDTA wet material, then carrying out airflow drying to obtain EDTA. Through the production method, the occurrence of side reactions is reduced; the purity of EDTA is improved; the conditions are provided for directly preparing sodium salt; the process steps are simplified.

Description

technical field [0001] The invention belongs to the technical field of preparation of ethylenediaminetetraacetic acid, in particular to a method for preparing ethylenediaminetetraacetic acid mainly using sodium cyanide, ethylenediamine, formaldehyde and liquid caustic soda as raw materials. Background technique [0002] Ethylenediaminetetraacetic acid (EDTA for short) is a white, tasteless, odorless crystal. As a chelating agent, EDTA is widely used in water treatment agents, detergents, metal cleaning agents, industrial cleaning agents, imaging chemicals, leather chemicals, paper chemicals, oil field chemicals, medicine, food, textiles, chemical fibers, dyes , synthetic resin, agrochemicals and analytical testing. [0003] Patent literature CN02133458.7 and US5208363 have introduced to take hydrocyanic acid, ethylenediamine, formaldehyde as raw material, generate ethylenediaminetetraacetonitrile in acidic environment, obtain EDTA by hydrolysis under acidic or alkaline cond...

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Problems solved by technology

[0003] Patent literature CN02133458.7 and US5208363 have introduced to take hydrocyanic acid, ethylenediamine, formaldehyde as raw material, generate ethylenediaminetetraacetonitrile in acidic environment, obtain EDTA by hydrolysis under acidic or alkaline conditions, because use gas hydrocyanic acid There are potential safety hazards for gas-liquid reaction, high equipment requirements, and can only be used for production near hydrogen cyanide production enterprises

Due to the formation of a considerable amount of ammonia and sodium sulfate in the synthesis process, the discharge of tail gas ammonia and the generation of sodium sulfate mother liquor are formed; if the tail gas ammonia and sodium sulfate mother liquor are not recycled well, serious pollution sources will be formed

In the existing production process, the recovery of tail gas ammonia can basically be solved, but the recovery and utilization of sodium sulfate mother liquor has become a recognized problem

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