| 摘要 |
Thioglycolic acid is made by contacting in a reaction zone at elevated pressure of H2S gas of at least 250 psig (1723 kPa) a mixture of monochloroacetic acid and dichloroacetic acid with a molar excess of an alkali metal or alkaline earth metal hydrosulfide to form the metal salt of thioglycolic acid, acidifying said salt and removing the free thioglycolic acid. The ratio of monochloroacetic acid to dichloroacetic acid is 99:1 to 75:25 by weight, the molar ratio of hydrosulfide to monochloroacetic acid is at least 2.1 and the under ratio of hydrosulfide to dichloroacetic acid is at least 3.1. A preferred process further requires separating any formed thiodiglycolic acid from the resultant liquid phase materials and recycling said acid to the reaction zone. |
