Verfahren zur Herstellung von Lösungen reiner Peressigsäure

Solutions of pure peracetic acid are obtained by reacting hydrogen peroxide and acetic acid in a molar ratio of >1 in the presence of an acid catalyst and distilling the peracetic acid and water off from the reaction mixture. The acid catalyst is a substance that is soluble in the reaction mixture, has no strong oxidising or reducing action, and produces solutions of the required pH. Sulphuric acid is preferred, other specified catalysts being sodium and potassium acid sulphates, ortho, meta and pyro-phosphoric acids and ion exchange resins containing sulphonic or phosphonic acid groups. The molar ratio of hydrogen peroxide to acetic acid is preferably between 5:1 and 15:1. The process is suitably carried out at 20 DEG to 80 DEG C. and preferably at 40 DEG -65 DEG C. and in a vacuum, in the presence of more than 3% of the catalyst by weight, and where this is sulphuric acid, advantageously from 10 to 30%. The process may be carried out continuously by constantly distilling the aqueous peracetic acid and feeding in the hydrogen peroxide rich reaction mixture, hydrogen peroxide and acetic acid in the molar ratio of 1:1. This method may conveniently be used to prepare solutions of peracetic acid in organic solvents which are not, or only slightly, soluble in water and which form an azeotropic mixture with water. The water-solvent azeotrope is distilled off and the peracetic acid solution is removed from the sump. During the process the peroxygen compounds may be stabilised by compounds such as esters of polyphosphonic acids or phosphonic acid. An example is provided.