Recovering platinum and palladium from various carrier spent catalysts and other waste residues

Various types of supported catalysts are widely used in the chemical and petrochemical industries, such as the production of hydrogen peroxide by the anthraquinone method, the synthesis of urea, the removal of CO from the raw gas of ammonia synthesis, the hydrogenation of benzene to synthesize cyclohexane, the catalytic combustion of low-concentration organic volatiles, and the heavy oil refining in petroleum refining. Wholeness, isomerization, cracking, hydrogenation, dehydrogenation and other reactions.

Among various types of carriers, Al2O3 is mostly used, and a small amount of SiO2 and CaCO3 carriers are used. Platinum and palladium are mainly used to form two series: Pt/Al2O3 and Pd/Al2O3. Depending on the purpose of use, the platinum and palladium content of the catalyst is 0.01-0.5%, which is a low-grade waste. Al2O3 carrier spent catalysts are mostly 3-5mm spherical or cylindrical. The crystal structure of the carrier is divided into a type and y type. The acid solubility of the two is very different. The a type is insoluble in acid, while the y type is easily soluble in acid. acid. Various types of spent catalysts have simple components and only involve the recovery of a single platinum or palladium.

The key to regeneration and recovery technology is the effective separation of platinum or palladium from the carrier to extract platinum and palladium enrichments or refined metals. One method is to directly stir (or percolate, soak) with acid or other chemical reagents to leach platinum and palladium, and then use anion exchange, zinc (or iron, aluminum) replacement, activated carbon adsorption, sodium sulfide precipitation, and ethyl from the solution. Enriched by xanthate precipitation and other methods. The opposite method is to leach the carrier to obtain a residue enriched in platinum and palladium. After the platinum and palladium enrichments or crude metals are extracted by the two methods, there is no technical difficulty in further refining them into pure metals.