GB803159A - Process for producing peracids from aliphatic carboxylic acids - Google Patents

Abstract

C2-3 aliphatic monopercarboxylic acids, specifically peracetic and perpropionic acids, are prepared by the reaction in the liquid phase of the corresponding carboxylic acid and aqueous hydrogen peroxide in the presence of an esterification catalyst and of an inert organic liquid having a b.p.760 of 50-130 DEG C. which is a solvent for the peracid and not for water and which forms with water preferentially a minimum-boiling, heterogeneous azeotrope containing in the aqueous layer of the distillate not more than 0.5 mol. of the peracid per mol. of water, and removing water from the reaction zone as the azeotrope at 20-90 DEG C. until an amount of water corresponding to all of the solvent water of the aqueous hydrogen peroxide and at least part of the water formed in the reaction has been removed. Azeotrope-forming solvents with a b.p. of 70-110 DEG C. are preferred. Suitable liquids include saturated lower aliphatic carboxylic esters, preferably those having at least 2 carbon atoms in each half of the molecule; saturated lower aliphatic ethers including stable chlorine and fluorine substituted ethers, e.g. those in which the carbon atom to which the halogen is attached is not adjacent to the ether-oxygen atom; halocarbons and aromatic hydrocarbons, e.g. benzene and toluene. The water removal operation may be carried out at pressures from 6 mm. Hg. absolute to 4 atmos. It is preferred to use the carboxylic acid and the hydrogen peroxide in stoichiometrically equivalent quantities. The aqueous hydrogen peroxide preferably contains about 25-90 per cent by weight of H2O2. Preferred esterification catalysts are H2SO4 and the alkyl and aryl sulphonic acids; others include H3PO4, alkyl hydrogen phosphates, trifluoroacetic acid, acetylsulphoacetic acid and ion-exchange resins. The amount of catalyst may be 0.2-5 parts by weight of carboxylic acid. The process may be operated continuously or batchwise at 20-90 DEG C. Examples describe the preparation of peracetic and perpropionic acids, azeotrope-formers used being chloroform, isopropyl acetate, ethyl acetate and n-propyl acetate. A polyphosphate sequestering agent is included in some examples. Reference has been directed by the Comptroller to Specification 776,758.