GB834154A - Improvements in the preparation of hydrogen peroxide - Google Patents

Abstract

In the production of hydrogen peroxide by a process comprising inter alia partial or complete catalytic reduction of an organic compound, e.g. a 2-alkyl anthraquinone or an azo benzene, in a solvent medium with hydrogen optionally containing an inert gas, regeneration is effected by periodically passing inert gas free from hydrogen, or containing hydrogen at a partial pressure less than that of the hydrogen in the reduction stage into contact with all or a portion of the catalyst in the presence of all or a portion of the reduced solution. The process comprises catalytic reduction with hydrogen of an organic compound in a solvent medium, oxidation with oxygen which may be pure or in the form of air of the reduced solution after removal of the catalyst, thereby regenerating the original organic compound and simultaneously producing hydrogen peroxide, and recycling of the oxidized solution to the reduction stage after extraction of the hydrogen peroxide with water. Normal hydrogenation, catalyst regeneration and oxidation may be carried out at substantially atmospheric pressure. The regeneration gas may comprise inert gas at a partial pressure of at least 0.1-0.3 atmos. and hydrogen at a partial pressure of not more than 0.7-0.9 atmos. Regeneration may be effected at a temperature of 50-150 DEG F., for a period of 1/3 -4 hours. Regeneration may take place in the hydrogenation vessel using a suspended or non-suspended catalyst. Solution and suspended catalyst may be withdrawn continuously or intermittently, and regeneration effected in a separate vessel. Inert gases specified are nitrogen, argon, helium, methane and ammonia. Quinones specified are 2-ethyl, 2-tert.-butyl, and 2-n-propyl anthraquinone, and 2-ethyl, and 2-tert.-butyl tetrahydroanthraquinone, and a mixture of 2-ethyl anthraquinone and 2-ethyl tetrahydroquinone. Solvent media specified are benzene, xylene, dichlorobenzene, cyclohexanol, methyl naphthalene, a mixture of alkyl benzenes having a boiling range of 365-415 DEG F., and a mixture comprising benzene, xylene, toluene, di- or tri-ethyl benzene, tetramethyl benzene, methyl naphthalene, diphenyl, or diphenyl oxide, and cyclohexanol, diisobutyl carbinol, monyl alcohol, hexanol, dibutyl phthalate, dibutyl sebacate, or di-isobutyl ketone. Catalysts specified are unsupported palladium and Raney nickel, and palladium supported on alumina, aluminium silicate, and bone char. Less than 50% of quinone may be converted to quinol. As catalyst activity decreases further catalyst may first be added. The catalyst may then be regenerated and a portion removed from the solution. An example is given.