Patent ID: 7371892
Filing Date: 2008-05-13
Classification: C07C

Abstract:
1. A process for working up 4-β-sulfatoethylsulfonylaniline-2-sulfonic acid from a solution in aqueous sulfuric acid, which comprises a first step of either precipitating the 4-β-sulfatoethylsulfonylaniline-2-sulfonic acid by addition of alkali metal, alkaline earth metal and/or ammonium salts, separating the precipitate from the solution and dissolving said precipitate in water, or precipitating the sulfuric acid by addition of calcium salts with the resulting calcium sulfate precipitate optionally being separated off, and a second step of adjusting the resultant solution to a pH between 1 and 5 by addition of alkali metal, alkaline earth metal or ammonium hydroxide, carbonate, bicarbonate and/or acetate, with any calcium sulfate precipitate still present being separated off, and thereafter isolating the 4-β-sulfatoethylsulfonylaniline-2-sulfonic acid from the solution.