GB768675A - Improvements in or relating to production of hydrogen peroxide - Google Patents

Abstract

<PICT:0768675/III/1> In the production of hydrogen peroxide from an alkyl anthraquinone by successive reduction and oxidation, a solution of an alkyl anthraquinone is partially reduced with hydrogen in a reduction zone in the presence of a particle form hydrogenation catalyst, and the partially reduced solution is passed to an oxidation tower packed with an inert solid contact mass, and is contacted with a free oxygen-bearing gas at 30-80 DEG C. and 15-300 p.s.i.a. to produce hydrogen peroxide. Recycle 2-ethyl anthraquinone solution (8-15 per cent) in a mixture of tetralin and methyl cyclohexanol enters reduction tower 11 from pipe 10 and contacts a co-current of hydrogen entering at 13 from compressor 12. Tower 11 contains a fixed bed of particles of palladium or platinum on alumina of size 4-100 mesh. Reduction is effected at 30-80 DEG C. and 15-300 p.s.i.a. until 50-75 per cent conversion has occurred. The reduced solution passes through pipe 16, cooler 17, and pressure release 18 to oxidation tower 20, which is filled with pellets or granules of silica, alumina, asbestos, or porcelain of size 10-100 mesh, and contacts a countercurrent of air, oxygen, or oxygen-enriched air entering from compressor 22 through diffuser 23. The oxidized solution passes to recovery tower 25, and is stripped with steam entering at 26 to yield a hydrogen peroxide/water vapour mixture from 27, which is concentrated. Alternatively, water or dilute aqueous hydrogen peroxide may be used to extract hydrogen peroxide from the oxidized solution, and extraction may be continuous in several countercurrent stages. The stripped oxidized solution is recycled through pipe 28 and heat exchanger 29 to 10. The gas-liquid contact in the reduction tower may alternatively be countercurrent, while in the oxidation tower, which should be liquid-flooded, and in which an aqueous hydrogen peroxide phase should be maintained, liquid/gas contact may be concurrent. Other anthraquinones may be isopropyl, tert-butyl, tetramethylene, or 2-methyl anthraquinones, or mixtures, and other solvents may be mixtures of benzene and cyclohexanol, or of tetralin and cyclohexyl cyclohexanol. The hydrogenation catalyst may be prepared by treating activated alumina or alumina gel of 4-100 mesh size with hot concentrated nitric acid, and igniting at 1000 DEG C. The alumina is cooled, exposed to hydrazine vapour, and contacted with a platinum or palladium salt solution, which is reduced by the absorbed hydrazine, to deposit 0.05-5 per cent platinum or palladium on the alumina. The alumina is then washed by decantation, ignited in air at 500-700 DEG C., and reduced in hydrogen at 30-40 DEG C. The catalyst may be regenerated by ignition in air.