GB1059317A - A method of purifying the recycle solution used in the production of hydrogen peroxide by the anthraquinone process - Google Patents

Abstract

Active alkylanthraquinones (i.e. alkylanthraquinone and alkyltetrahydroanthraquinone compounds) obtained in a fraction by the distillation of a partly degenerated recycle solution used in the production of hydrogen peroxide by the anthraquinone process (see Division C1) are reduced in an aqueous alkaline medium to form the soluble alkali metal salts of alkylanthrahydroquinones, the undissolved components are then removed and the salts are converted by oxidation into the waterinsoluble alkylantraquinones which are recovered and used to fortify another portion of the recycle solution. The reducing agent used in the reduction step may be sodium dithionate or powdered zinc and this step is preferably performed in an inert atmosphere, e.g. nitrogen. An alkali metal hydroxide may be used for producing the aqueous alkaline solution and the oxidation may be effected with air in the presence of solvents. Recycle solutions containing 2-ethyl, 2-isopropyl-, 2-tert-butyl-, 2-amyl and 2-octyl anthraquinones or their mixtures are particularly referred to.ALSO:The recycle solution used in the production of hydrogen peroxide by the anthraquinone process is purified by fractionally distilling the partly degenerated recycle solution to obtain a first fraction containing solvents and a second higher temperature fraction containing the alkyl anthraquinone, the active alkylanthraquinones (i.e. alkylanthraquinone and alkyltetrahydroanthraquinone compounds) in the latter fraction are reduced in an aqueous alkaline medium to form the soluble alkali metal salts of alkylanthrahydroquinones, the undissolved components are then removed and the salts are converted by oxidation into water-insoluble alkylanthraquinones which are used to fortify another portion of the recycle solution. The reducing agent used in the reduction step may be sodium dithionite or powdered zinc and this step is preferably performed in an inert atmosphere, e.g. nitrogen. An alkali metal hydroxide may be used for producing the aqueous alkaline solution. The oxidation may be effected in the aqueous reaction solution with air in the presence of solvents, preferably those recovered in the preceding fractionation of the recycle solution, to form a solution which is then used to fortify the recycle solution. The recycle solution may first be subjected to regeneration by a method known per se.