Study On The Green Process For Synthesis Of Thioglycolic Acid

Thioglycolic acid, abbreviated as TGA, have synonyms which are acetyl mercaptan,mercaptoacetate, mercaptoacetic acid,2-mercaptocaetic acid,2-thioglycolic acid and thiovanic acid. Because there are both carboxy group and hydrosulfide group in TGA, it is an important chemical raw material and was used widely in chemical industry, light industry, Pharmaceuticals industry, prtroleum extraction, mineral separation and so on. At present the methods of TGA industry production mainly include sodium hydrosulfide process, sodium thiosulfate process, sodium polysulfide process, sulfo carbamide process, joint production et al. But there are shortages in these processes. Some process need high-pressure system, some process need challenging operation, and others need reducing agent such as zinc and iron, which would introduce the pollution of environment and the increase of producing cost. The documentations about directly electroreduction of dithiodiglycollic acid, abbreviated as DTDGA, to prepare TGA are less, and the reports about the route based on sodium thiosulfate process in which the operation is more simple and the cost is more economical, followed by electrochemical reduction of the middle results or outgrowth DTDGA are much less. So in this paper the green new technology for synthesis TGA of the joint of sodium thiosulfate process and electrochemical reduction was studied. Monochloroacetic acid and sodium thiosulfate were raw materials.First, in order to determinate the content of DTDGA the analytical method of DTDGA must be founded. In this paper the theories of iodometric titration and total quickly reduction of DTDGA by zinc amalgam in the Jones reductor was employed, and the reductor was made by ourselves. The method is simple, rapid and accurate with average recovery of 100.12% and RSD of 1.63% (n=6).Then, TGA was synthesized by sodium thiosulfate process and with sodium chloroacetic acid and sodium thiosulfate as raw materials. The influence laws of the proportion of materiel, time, and temperature in nucleophilic substitutional reaction and the dosage of vitriol, time and temperature in hydrolyze reaction were studied on the yield of TGA by experimental tools such as orthogonal design method. Through...