Synthesis method of 2-methylphenoxyacetic acid

Abstract

The invention discloses a synthesis method of 2-methyl phenoxy acetic acid. The method comprises: pouring o-cresol and caustic soda liquid into a reaction kettle according to a ratio of 1:1; controlling a certain temperature to start dropwise adding 73% chloroacetic acid aqueous solution while stirring, dropwise adding liquid caustic soda when the pH value of the feed liquid is 8-9, controlling the dropwise adding speed of the liquid caustic soda and chloroacetic acid, always maintaining the pH value of the feed liquid to be 9-10, and stopping dropwise adding the liquid caustic soda when the pH value of the feed liquid is adjusted to be 9-10 by using the liquid caustic soda; and carrying out thermal insulation for 0.5 h to obtain a sodium 2-methylphenoxyacetate solution, adding a certain amount of water, cooling to room temperature, dropwise adding hydrochloric acid to adjust the pH value of the feed liquid to 1-2, precipitating a large amount of white solid 2-methylphenoxyacetic acid,carrying out suction filtration, and washing with water to obtain the white 2-methylphenoxyacetic acid product. According to the method, saline water cooling and steam heating are not needed, the condensation yield is increased, and the defects that in a traditional synthesis process, a large amount of electric energy and a large amount of steam are consumed are overcome.

Description

technical field [0001] The invention relates to the technical field of organic chemical industry, in particular to a method for synthesizing 2-methylphenoxyacetic acid. Background technique [0002] The traditional synthesis process is to first react o-cresol with liquid caustic soda at 0-5°C to form sodium chloroacetate, and then add sodium chloroacetate dropwise to the sodium o-cresol solution for condensation reaction. Shortcoming one is that chloroacetic acid will release a large amount of heat when neutralizing, and the temperature of neutralization reaction can not be high again, otherwise it will cause chloroacetic acid to be hydrolyzed into sodium glycolate under alkaline conditions. Therefore just must control neutralization temperature at 0-5 ℃ with a large amount of frozen brine, so just certainly will consume a large amount of electric energy. The second is that during the condensation reaction, adding sodium chloroacetate to the condensation kettle needs to be ...

AI Technical Summary

Problems solved by technology

The synthesis method cleverly utilizes self-neutralization and condensation reaction heat release to maintain the energy required for the reaction. The entire reaction process does not require the use of frozen brine or steam, which overcomes the defects of consuming a large amount of electric energy and a large amount of steam in the traditional synthesis process. ; In addition, the preparation of high-concentration chloroacetic acid has also accelerated the reaction speed and reduced the amount of waste water

Images