The Destiny of Palladium: Development of Efficient Palladium Analysis Techniques in Enhancing Palladium Recovery

The palladium-catalyzed cross-coupling reaction is a widely used protocol to build C–C or C–heteroatom bonds in organic synthesis in both academic research and industrial production. For the past decade, the use of palladium catalysts in the synthesis of fine chemicals, pharmaceutical intermediates, and active pharmaceutical ingredients has become more frequent. A serious problem results in residual palladium remaining in the final product, leading to the rising need for cost-effective ways to remove palladium contaminants. Along with the scarce nature of this precious metal, the demand for palladium recovery is critical for a cost-effective process. A recovery process using aqueous sodium bisulfite solution at elevated temperature offered 60–80% palladium recovery in the form of sodium palladium tetrasulfite dihydrate complex, Na6Pd­(SO3)4·2H2O. Modified neutron activation analysis technology was adapted to fully close the palladium mass balance. With this accurate palladium detection method, we were able to further optimize the palladium recovery process by a set of designed experiments.