Benzoic acid, 2-amino-4-hydroxy-

2-Hydroxy-4-aminobenzoic acid is a carboxylic acid derivative and an important intermediate in the synthesis of pharmaceuticals and dyes.

1. At room temperature, m-aminophenol reacts with sodium alcohol in alcohol for 0.8~1.2 hours to obtain an alcohol solution of m-aminophenol sodium salt; the molar ratio of m-aminophenol to sodium alcohol is 1:1~5 ;

2. put the alcohol solution of m-aminophenol sodium salt into an autoclave, pass the carbon dioxide recovery gas, and react under the supercritical condition of carbon dioxide for I~5 hours (preferably 3~5 hours), and the molar ratio of m-aminophenol sodium salt to carbon dioxide is 1:1~10 ;

At the end of the reaction, the resulting reaction solution is reduced to room temperature, filtered, and the filtrate is evaporated under reduced pressure to remove the solvent alcohol, to obtain a solid; add water to dissolve the solid (the amount of water is just enough to make the solid soluble), to obtain the solution; to the resulting solution, add inorganic acid to adjust the PH to 6~7, a solid is precipitated, and filtered again, and the resultant filter cake is 2-hydroxy-4-amino benzoic acid.