Patent GB-796461-A (GB)
Title: Process for the manufacture of hydrogen peroxide
IPC: C01B15/023
Filed: 1956-07-05
Abstract: An anthraquinone compound is converted to an anthrahydroquinone compound by hydrogenation in an organic solvent, a metal of the Eighth Group of the Periodic Table supported upon an alkaline earth metal phosphate being employed as catalyst, in a process for the manufacture of hydrogen peroxide.  The term "anthrahydroquinone compound" includes anthra-quinone, its homologues, substitution products and nuclear hydrogenation products.  The term "anthraquinone compound" is defined to mean any corresponding anthraquinone. Anthraquinones mentioned include alkyl-aryl and aralkyl substituted anthraquinones such as 2-ethyl-, 2-isopropyl-, 2-sec.-butyl- and 2-tert.-butyl anthraquinones, 1,3-, 2,3- and 1,4-dimethyl anthraquinones, 2-benzyl- and 2-phenyl anthraquinones and the corresponding tetrahydroanthraquinones produced by the hydrogenation of the above compounds.  Solvents mentioned include cycloaliphatic esters of straight-chain aliphatic acids, anisole and aromatic hydrocarbon solvents, alcohols such as primary or secondary nonyl alcohols, cyclohexanol and methyl cyclohexanol, the latter being mixed with alkyl naphthalenes or other aromatic solvents mentioned. In the example a mixture of 2-ethyl anthraquinone and tetrahydro-2-ethyl anthraquinone dissolved in a solvent consisting of triethyl benzene and methyl cyclo hexyl acetate is continuously hydrogenated using a catalyst comprising palladium supported on calcium phosphate (see Group III).  Specifications 465,070, [Group IV], 508,081, 686,567, and 686,574, [all in Group III], are referred to.ALSO:In a method of manufacturing hydrogen peroxide by a process which includes hydrogenation of an anthraquinone compound in solution in an organic solvent therefor which is also a solvent for the resulting anthraquinone compound and oxidizing such resulting anthrahydroquinone compound while still in solution in such organic solvent by means of molecular oxygen to regenerate the anthraquinone compound and concomitantly form hydrogen peroxide, such hydrogenation is effected with elemental hydrogen in the presence as catalyst of a metal of the Eighth Group of the Periodic Table supported upon an alkaline earth metal phosphate. The term "anthrahydroquinone compounds" includes anthrahydroquinone, its homologues, substitution products and the nuclear hydrogenation products of said compounds. The term "anthraquinone compound" is defined as meaning any of the corresponding anthraquinones.  Anthraquinones mentioned include alkyl-, aryl- and aralkylsubstituted anthraquinones such as 2-ethyl-, 2-isopropyl-, 2-sec. butyl and 2-tert. butyl anthraquinones, 1,3-, 2,3- and 1,4-dimethyl anthraquinones, 2 - benzyl - and 2 - phenyl anthraquinones and the corresponding tetrahydroanthraquinones produced by hydrogenation of the above compounds.  Palladium is specified as the preferred catalytic metal and nickel and platinum are also mentioned.  The carrier may merely comprise a substantial amount of alkaline earth metal phosphate, e.g. as in tricalcium phosphates of the formula XCa3 (PO4)2.CaO, where X is greater than 3, usually from 6 to 10.  Other components may be carbon or calcium carbonate.  Bone char, optionally after heating, may be employed as support.  Other phosphates mentioned include magnesium, calcium-magnesium, and barium phosphates.  Solvents mentioned for use in the process include cycloaliphatic esters of straight chain aliphatic acids, e.g. esters of such acids and cyclohexanol or alkyl-substituted cyclohexanols containing up to 8 carbon atoms in the alkyl group, e.g. cyclohexyl acetate or propionate, methyl cyclohexyl acetate, propionate and butyrate.  Additional solvents which may be employed include anisole, aromatic hydrocarbon solvents, e.g. benzene, toluene, xylene, ethyl benzene di- and tri-ethyl benzenes, alcohols such as primary or secondary nonyl alcohols, cyclohexanol and methyl cyclohexanol, the latter usually being mixed with alkyl naphthalenes or other aromatic solvents mentioned above. In the example a mixture of 2-ethyl anthraquinone and tetrahydro-2-ethyl anthraquinone dissolved in a solvent consisting of triethyl benzene and methyl cyclohexyl acetate is continuously hydrogenated using a palladium catalyst supported on calcium phosphate, the resulting solution is oxidized with air and hydrogen peroxide is extracted from the product with water.  The catalyst is prepared by heating bone char to 600 DEG  C. in an inert atmosphere, treating the product succesively with sodium hydroxide solution and palladium chloride solution and reducing the palladium to the metallic state with hydrogen.  Comparative tests are carried out using catalysts prepared from bone char and a synthetic bone char which have been subjected to heat treatment in inert and oxidizing atmospheres. Additional solvents and alkylated anthraquinones suitable for use in the process are described in Specifications 465,070, 508,081, 686,567, 686,574 and U.S.A. Specifications 2,215,856 and 2,215,883.