GB546530A - Improvements in the purification of aqueous hydrogen peroxide - Google Patents

Abstract

546,530. Distilling & purifying hydrogen peroxide. MATHIESON ALKALI WORKS. Dec. 28, 1940, No. 18182. Convention date, Dec. 29, 1939. [Classes 1 (ii) and 32] Concentrated solutions of hydrogen peroxide (30 per cent. peroxide) obtained in the oxidation of organic intermediates e.g. as described in Specifications 461,589, 501,385 and U.S.A. Specification 2,059,569 are purified with or without further concentration by first removing impurities of lower boiling point than the peroxide by vaporizing water from the solution and passing the solution in countercurrent to the steam produced, separating the vaporised impurities from the water component and returning the latter to the solution, then vaporising the whole of the hydrogen peroxide from the solution under reduced pressure and periodically removing the aqueous residues together with the accumulated impurities therein. The organic impurities include solvents, e.g. hydrocarbon oils, and intermediates, e.g. para-azo-toluene, and their decomposition products while the inorganic impurities include iron, nickel, copper, mercury, and their compounds and silica. The crude peroxide solution is charged to a flask 3 from which it is passed through a sight glass 5 to a packed column 6. The solution flows down the column to a flask 2 heated by a jacket 8 to vaporize the water but not the peroxide. The steam passing upwardly strips the crude solution of volatile impurities and the mixed vapours are condensed in cooler 14 and separated in receiver 16 into water containing a little peroxide, which is returned through line 17 to the column 6, and impurities, which are removed to receiver 19. The stripped solution is then passed through line 12 into a flask 1 maintained under reduced press by pump 22 and heated to such temperature that the hydrogen peroxide is vaporized to leave a residue in which the non-volatile impurities are concentrated and which is rejected at frequent intervals through line 27. The vapours are condensed and passed to receiver 33 and collection vessel 35. A stabilizer, e.g. sodium stannate, sodium pyrophosphate may be added through line 32.