Method for preparing high-quality thioglycolic acid from the tail liquid of producing o-alkyl-n-alkylthiocarbamate

Abstract

The invention discloses a method for preparing high-quality mercaptoacetic acid from a tail solution from O-alkyl-N-alkyl thinocarbamate production. The method comprises the following steps: (1) performing acidizing treatment on the tail solution by using an inorganic acid, and controlling the pH value to be 0.5-1.5; (2) leaving to stand for 6-48 hours, separating suspended organic matters, extracting by using an organic solvent, and extracting by using an extraction agent, thereby obtaining an extraction liquid, wherein the volume ratio of the total amount of the organic solvent to an acidifying liquid is (2.5:0.01)-(2.5:0.1), the organic solvent consists of 40-60wt% of glutaric acid diethyl ester and 40-060wt% of ethyl malonic acid diethyl ester, the volume ratio of the total amount of the extracting agent to a new acidifying liquid is (2:0.1)-(2:2), and the extracting agent is prepared by mixing n-amyl ether, isoamyl ether and sec-butyl methyl ether in a mass ratio of (1-3):(1-3):(1-3); (3) removing the solvent and water from the extraction liquid, thereby obtaining crude acid; (4) performing flash evaporation on the crude acid. The method is high in recycling rate, high in product purity, good in quality and simple in process.

Description

technical field [0001] The invention relates to a method for preparing high-quality mercaptoacetic acid from the tail liquid of O-alkyl-N-alkylthiocarbamate. Background technique [0002] Thioglycolic acid has both the reaction characteristics of hydroxy acid and the reaction characteristics of sulfhydryl, and the most important reaction is the reaction with disulfide. Especially under alkaline conditions, it reacts with cystine in hair, cuts the (-S-S-) bond of cystine, and generates cysteine ​​that is easy to curl. Thioglycolic acid is an intermediate in the production of thiomethoprene (caputolic), biotin, thiozincic acid, sodium dithiosuccinate and other pharmaceuticals, and it is also a synthetic cysteine, hormone agent, and industrial disinfectant And an important raw material for the synthesis of sulfuric acid. Ammonium and sodium thioglycolate are mainly used as curling agents, calcium salts as depilatory agents, polyvinyl chloride low-toxic or non-toxic stabilizer...

AI Technical Summary

Problems solved by technology

[0004] At present, the color of thioglycolic acid produced domestically using the tail liquid of thiourethane is relatively yellow and the purity is low. High-quality products can only rely on imports, which limits the application of thioglycolic acid.