GB786838A - Purification of crude aqueous hydrogen peroxide - Google Patents

Abstract

In a process for producing hydrogen peroxide by alternately hydrogenating a solution of an alkyl anthraquinone in a water-immiscible solvent and oxidizing the resulting solution of an alkylanthrahydroquinone to regenerate the solution of an alkylanthraquinone for recycling after separating the simultaneously formed hydrogen peroxide therefrom, wherein the hydrogen peroxide is separated in the form of a crude aqueous solution, the crude solution is subjected to liquid phase extraction with an inert hydrocarbon liquid having an atmospheric boiling point not exceeding 145 DEG C. and residual amounts of the hydrocarbon liquid are stripped from the resulting extracted hydrogen peroxide solution. Organic impurities and iron are removed from the solution. The extraction may be at a pressure and temperature such that the extracting hydrocarbon is liquid, and may be effected batchwise, or continuously countercurrent in a packed tower. Hydrocarbons, which should contain no aliphatic unsaturation, may be n-butane, n-pentane, isopentane, hexanes, heptanes, cyclopentane, cyclohexane, methyl-cyclohexane, benzene, toluene, or xylene. Preferred is the petroleum cut boiling at 97-101 DEG C. known as commercial heptane. The stripping may be effected by aeration with an inert gas, e.g. air, nitrogen, or steam, at normal pressure and temperature not exceeding 100 DEG C., preferably 30-50 DEG C., or by fractional distillation at a pressure not exceeding 200 mm. Hg., preferably a pressure not exceeding that corresponding to a boiling temperature of 100 DEG C. The stripping may be batch or continuous operations, preferably multistage, continuous, countercurrent operations. The aqueous solution may contain 10-50 per cent H2O2 and stripping by fractional distillation will effect some concentration. Stabilizers, e.g. sodium stannate or pyrophosphate, may be added. Specifications 686,567 and 686,572 are referred to.