Improvements in or relating to the manufacture of catalysts

摘要

Palladium catalyst is prepared by adsorbing a palladium salt from solution on to an alumina carrier and treating with a water-soluble metal hydroxide or carbonate to form a hydrated palladium oxide or basic carbonate, which is thereafter reduced to metallic palladium. Activated gamma-alumina or gamma-alumina monohydrate of coarse or fine particle size is stirred for a short time with a solution of palladium chloride, nitrate, or acetate, the slurry is filtered and washed, the solid stirred with caustic soda solution and again filtered and washed; further treatments with palladium salt solutions may be given, using the filtrate from the first stage or solutions of higher concentration. The amount of acid in the palladium salt solution should be limited to that required for complete solution of the salt. The palladium content of the final catalyst is 0.01-10 per cent., varying with the particle size of the alumina. The catalyst is used in the hydrogenation stage of the cyclic process for the manufacture of hydrogen peroxide by autoxidation of anthraquinhydrones, for example as described in Specification 718,305; before use the catalyst is reduced with a mixture of hydrogen and nitrogen of increasing hydrogen content, or reduction may be effected in the hydrogenator. Regeneration of the catalyst may be carried out by thermal oxidation of the adsorbed organic matter, followed if necessary by reduction. Specification 508,081 also is referred to. The Provisional Specification refers also to the use of charcoal as the carrier.