Patent GB-867679-A (GB)
Title: Improved process for the preparation of hydrogen peroxide
IPC: C01B15/023
Filed: 1959-09-01
Abstract: <PICT:0867679/III/1> In the production of hydrogen peroxide by the successive hydrogenation and oxidation of a 9:10-anthraquinone or 5:6:7:8-tetrahydro-9:10-anthraquinone alkylated in only the 1-, 2-, 3- or 4-position (or mixtures thereof) dissolved in an inert water-immiscible solvent followed by extraction of the hydrogen peroxide formed with water, oxidation with elemental oxygen is effected in the presence of between 0.002 and 0.25% by weight of the working solution of a water-soluble inorganic alkaline substance, whereby the oxidation of the corresponding tetrahydroanthrahydroquinone present is accelerated.  The alkyl group may be a methyl, ethyl, propyl or isobutyl group, and the alkaline substance may be sodium carbonate or ammonium, sodium, potassium, calcium or magnesium hydroxide.  The solvent may contain a component dissolving the quinone, e.g. benzene, toluene or xylene, a component dissolving the hydroquinone, e.g. cyclohexanol, methyl cyclohexanol, or amyl, octyl, nonyl or decyl alcohol, and a synergistic solvent such as acetophenone.  The initial working solution may contain a mixture of anthraquinone and tetrahydroanthraquinone only.  As shown, the working solution is introduced through line 1 into reduction chamber 2 maintained at 20-50 DEG C. under a pressure of 1-5 p.s.i.g. The hydrogenation catalyst, e.g. palladium or platinum on a solid support, preferably 5% by weight of palladium on a charcoal or alumina carrier, is also added through line 1.  Hydrogen is forced by pump 3 through line 4 into the bottom of chamber 2, and is released from the top through line 5 to the suction side of pump 3. Additional hydrogen is added via line 6.  The hydrogenated solution is discharged from chamber 2 through line 7 into a centrifuge 8 wherein the catalyst is separated and returned via line 9 to chamber 2, while the solution flows through line 11 into after-cooler 12 and then through line 13 into oxidation tower 14 filled with Berl saddles or glass beads.  The oxidation catalyst, preferably ammonium or sodium hydroxide, may be added through line 10 or introduced directly into tower 14.  Gas containing free oxygen, e.g. air, is introduced into tower 14 by compressor 15 and line 16, while exhausted gas is released through line 17 and valve 18.  Acid, such as sulphuric or phosphoric acid, to suppress emulsion-forming tendency is added through line 21 to the solution withdrawn through line 19.  The solution passes to centrifugal extractor 22 to which distilled water is fed via line 23, and the hydrogen peroxide solution is withdrawn via line 24, the remaining working solution passing back to chamber 2 via lines 25, 26, loss being replaced through line 27.  In Example 1, the working solution comprises (by weight) 34.1 parts acetophenone, 27.1 parts capryl alcohol, and 23.7 parts xylene, and contains 15.1% of a mixture of 2-ethyltetrahydroanthraquinone (61%) and 2-ethylanthraquinone (39%).  0.5% of a hydrogenation catalyst consisting of 5% by weight of palladium on a carbon carrier is used, while 0.03 parts by weight of sodium hydroxide is added to the working solution prior to oxidation.  0.05% of sulphuric acid is added to the oxidized solution.  Examples 2 to 6 are similar, Examples 3 and 4 using ammonia and Examples 5 and 6 using sodium carbonate.