Recovery of Platinum and Palladium from the Spent Petroleum Catalysts by Substrate Dissolution in Sulfuric Acid

In this study, the recovery of platinum and palladium from petroleum catalysts has been elaborated using a method consisting mainly of dissolving alumina substrate in sulfuric acid thereby concentrating the precious metals in the residue. The effect of dissolution temperature and time, concentration of sulfuric acid, and pulp density on the dissolution of alumina substrate was investigated systematically. The optimum dissolution conditions for the platinum catalysts AR-405 and R-134 were: sulfuric acid 6.0mol/L, dissolution temperature 100 C, dissolution time 2 4 h, pulp density 220 g/L. The dissolution of R-134 catalyst the substrate consisting only of -Al2O3 phase was higher than that of AR405 which contained the mixture of -Al2O3 or -Al2O3. The optimum conditions for LD-265 are: sulfuric acid concentration 8.0mol/L, dissolution temperature 100 C, pulp density 220 g/L and time 18 h. It was found that platinum and palladium which was impregnated to alumina substrate as fine particles, also dissolved to some extent during sulfuric acid treatment. They could be recovered by a cementation process using aluminum powder. The complete recovery of Pt from AR-405 and R-134 catalysts was possible by the proposed method. Nevertheless, the method may not be applicable to LD-265 catalyst due to the time-consuming substrate dissolution process. [doi:10.2320/matertrans.M2010218]