METHOD OF PROCESSING EXHAUSTED CATALYSTS CONTAINING PLATINUM-GROUP METALS Russian patent published in 1999 - IPC

FIELD: precious metal recovery. SUBSTANCE: invention concerns catalysts, including motor-car catalysts, based on aluminum, silicon, and magnesium oxides containing platinum or palladium. Catalyst is broken to particle size -3 mm and subjected to acid treatment. Solid residue is blended with alkali metal hydroxide. Blend is caked, cake is leached with water, and platinum metal concentrate is filtered off. According to invention, acid treatment is carried out for 4-6 hr with 2-2.5 M sulfuric acid at 50-90 C at solids-to-liquid ratio 1:(3-5) in presence of inorganic reducing agent: cuprous compound, e.g. cuprous oxide with fineness -0.5 mm in amount corresponding to 0.2-0.5 their stoichiometric amount required for reduction of platinum group metal; alkali metal hydroxide (sodium or potassium hydroxide)-to-solid residue ratio in blend is (0.8-1.2):1; caking is carried out at 400 to 700 C for 1-2 hr; and cake leaching is conducted for 1-2 hr in presence of 10-20 g/l of alkali agent (sodium or potassium hydroxide) at solids-to-liquid ratio 1:(3-5). EFFECT: specified equipment and reduced platinum metal losses. 7 cl, 3 tbl