Recovery of catalytically-useful cobalt and like metal moieties from their solid oxalates with EDTA salts

摘要

The solid oxalate of a catalytic metal such as cobalt, typically formed as an undesired and useless by-product during the liquid- phase oxidation of an organic compound, typically a hydrocarbon, in the presence of a homogeneous catalyst comprising said metal, is treated to convert the metal moiety to a reusable form by a process comprising leaching the metal oxalate with an aqueous solution of a soluble salt of ethylenediaminetetraacetic acid (EDTA). The resulting solution of EDTA- metal complex or chelate is then mixed with a soluble calcium salt to precipitate the oxalate moiety as insoluble calcium oxalate leaving the metal-EDTA complex in solution. After removing the resulting solid calcium oxalate, the remaining filtrate is acidified to convert the metal moiety to a simple salt which can be recycled to the liquid- phase oxidation, while the EDTA is precipitated as a solid which can also be recovered and re-used in the complexation step of the process.