Method for preparing mercaptocarboxylic acid or derivatives thereof by aminolysis of thioureidocarboxylic acid or derivatives thereof

The invention relates to a method for preparing mercaptocarboxylic acid or derivatives thereof by aminolysis of thioureidocarboxylic acid or derivatives thereof. The method mainly comprises the following steps: 1, dissolving thioureidocarboxylic acid or a derivative thereof in ammonia water or a mixed solution of ammonia water and a cosolvent, heating the system to 40-150 DEG C, and reacting for long time until reaction of the thioureido salt is finished; 2, cooling the reaction system, neutralizing the reaction system by using acid, removing the solvent by using a solvent extraction system, and separating to obtain the mercaptocarboxylic acid or the derivative thereof; and 3, concentrating and filtering the residual water phase or organic phase, recycling the distilled water phase or organic phase, and taking the solid ammonium salt mixture as a nitrogen fertilizer. According to the method, the defects that pollutants are complex and difficult to treat, and the environment is pollutedin the prior art that me