GB808731A - Preparation of platinum metal catalysts - Google Patents

Abstract

In the manufacture of a platinum metal-on-alumina catalyst by impregnating activated alumina with a solution of a compound of a platinum metal and reducing the compound to metal, the activated alumina before impregnation is treated with an aqueous solution having a pH in the range 4 to 10 and containing at least one of the following oxidizing agents: water-soluble permanganates, pervanadates, permolybdates, monopersulphates, and perphosphates, hydrogen peroxide, ozone, sodium or other alkali metal peroxide, perhydrates, e.g. sodium perborate or sodium carbonate perhydrate, halogens (especially chlorine and bromine) and oxygen-containing halogen compounds having oxidizing properties, e.g. alkali metal and alkaline earth metal hypochlorites and hypobromites, hypochlorous acid, chlorine dioxide, and the alkali metal chlorites; after treatment of the alumina, the oxidizing agent is substantially completely removed. The aqueous solution preferably contains 0.5-4 per cent by weight of the oxidizing agent and may be applied at a temperature above 50 DEG C. for 0.2 to 2 hours. The pH of the aqueous solution may be adjusted by addition of sodium bicarbonate or carbon dioxide. When the oxidizing agent contains halogen, washing with dilute hydrogen peroxide is desirable before impregnation and reduction. Reduction may be effected with formaldehyde, formates, hydrazine, or hydrogen. The activated alumina may constitute at least 50 per cent by weight of the catalyst support or may itself be supported on kieselguhr. In Example I activated alumina is treated with an aqueous solution of sodium hypochlorite and sodium bicarbonate, washed successively with water and aqueous hydrogen peroxide to remove soluble salts, suspended in water saturated with carbon dioxide, and an aqueous solution containing palladous chloride and hydrochloric acid is added; the slurry is heated, mixed with aqueous formaldehyde to reduce the palladium salt, sodium bicarbonate to adjust the pH, and aqueous hydrogen peroxide to destroy any catalyst poison; the catalyst is then filtered, washed, and dried. In Example III hydrogen peroxide is used as the oxidizing agent in place of sodium hypochlorite. In Examples V and VI the carrier is impregnated with platinum-palladium and palladium-ruthenium, respectively, using aqueous solutions containing chloroplatinic akcid and ruthenium chloride. The catalysts are tested by use in the hydrogenation of 2-t-butylanthraquinone to 2-t-butylanthrahydroquinone. The catalysts are useful in the production of hydrogen peroxide by alternately hydrogenating and oxidizing an alkylanthraquinone.ALSO:2-t-Butylanthrahydroquinone is formed by passing hydrogen into a solution of 2-t-butyl-anthraquinone in a mixture of methylnaphthalene and di-iso-butyl carbinol in the presence of a platinum metal on alumina catlyst, the alumina before impregnation with the platinum metal having been treated with an aqueous solution of an oxidizing agent (see Group III).