Patent GB-864676-A (GB)
Title: Process for manufacturing hydrogen peroxide
IPC: C01B15/023
Filed: 1957-12-12
Abstract: A suspension of a solid anthraquinol in a water immiscible organic liquid is prepared by hydrogenation of a solution of a quinone in a water immiscible organic solvent which has a greater solubility for the quinone than for the quinol form (as defined) and which contains an amount of quinone in excess of that amount which corresponds to the maximum solubility of the corresponding quinol in the solvent, the hydrogenation being continued until the amount of quinol formed exceeds the solubility in the solvent and part precipitates to form the required suspension.  The degree of hydrogenation is preferably controlled so that the amount of quinol precipitated on hydrogenation is at least half the amount dissolved.  Hydrogenation is preferably carried out in the presence of a catalyst, which may comprise palladium either as a fine suspension in the reaction liquid, in which case it may be separated from the final quinol suspension by selective settling and filtration, or as a fixed surface e.g. as a metal gauze fitted in the reaction zone.  The quinol suspension thus produced is separated from entrained hydrogen and contacted with air or oxygen whereby the corresponding quinone is produced with generation of H2O2.  Hydrogen peroxide is extracted from the solution by washing with water and the extracted solution returned to the hydrogenation stage.  Anthraquinones e.g. 2-ethyl-, 2-isopropyl-, 2-sec-butyl, 2-tert-butyl-, 2-iso-propyl, 2-secamyl-, 1,2-; 1,3-; 1,4-and 2,7-dimethyl-anthraquinones in solutions in solvents e.g. chlorobenzenes; chloro-aliphatic hydrocarbons such as perchloroethylene, tetrachloroethane or ethylene dichloride; aromatic hydrocarbons such as benzene, xylene, sec-butyl benzene, toluene, ethyl benzene, triethyl benzene, a methyl naphthalene or tetrahydronaphthalene; diisobutyl ketone; n-hexyl ether; 2-ethyl hexyl acetate, methyl amyl acetate or methyl cyclohexanol acetate, are referred to.ALSO:<PICT:0864676/III/1> <PICT:0864676/III/2> <PICT:0864676/III/3> Hydrogen peroxide is produced by a process comprising hydrogenation of an anthraquinone in solution in a water immiscible organic solvent which has a greater solubility for the quinone than for the quinol form (as defined) of the anthraquinone the amount of anthraquinone being in excess of that amount which corresponds to the maximum solubility of the corresponding quinol in the solvent, the hydrogenation being continued until a suspension of quinol solids is produced, oxidising the suspended quinol until the complete resolution thereof is obtained, extracting the solution with water to remove hydrogen peroxide and recycling the extracted solution.  Solutions of an anthraquinone e.g. 2-ethyl-, 2-isopropyl-, 2-tert butyl-, 2-sec-butyl-, 2-sec-amyl-, 1,2 dimethyl-, 1,3-dimethyl-, 1,4 dimethyl-, or 2,7 dimethyl anthraquinone, in a solvent e.g. chloro-benzenes, chloro-aliphatic hydrocarbons such as perchloroethylene, tetrachloroethane or ethylene dichloride aromatic hydrocarbons such as benzene, xylene, sec-butyl benzene, toluene, ethyl benzene, triethyl benzene, a -methyl naphthalene or tetrahydronaphthalene, diisobutyl ketone 1-hexyl ether, 2-ethylhexyl acetate, methylamyl acetate or methyl cyclohexanol acetate are specified.  In operation, a solution of an anthraquinone is hydrogenated by contact with gaseous hydrogen preferably in the presence of a catalyst, which may comprise palladium either as a fine suspension in the reaction liquid, in which case it may be separated from the final quinol suspension by selective settling and filtration, or as a fixed surface e.g. as a metal gauze fixed in a suitable reaction vessel.  A suitable hydrogenation vessel comprises a cylindrical vessel 1 having a series of annular palladium wire baffles 4 secured to a liner 5 resting inside the vessel, a rotatable shaft 7 carrying a series of palladium wire mesh screens 8 each secured to a spider 9 keyed to a shaft 7, an inlet port 2 for hydrogen and solution and outlet port 3 for solution and entrained hydrogen.  The degree of hydrogenation is preferably controlled so that the amount of quinol precipitated on hydrogenation is at least half of the amount dissolved.  The resulting suspension of solid quinol is passed through a hydrogen disengager into an oxidiser where it is oxidised by agitation with air until complete resolution of the quinol, as quinone, is obtained.  Hydrogen separated in the disengager is recycled to the main hydrogen feed to the hydrogenator. The oxidised solution is washed with water in an extractor to isolate hydrogen peroxide and the extracted solution recycled to the hydrogenation step.