# US 4,394,355 A · Recovery of catalytically-useful cobalt and like metal moieties from their solid oxalates with EDTA salts > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 4,394,355 A - Document ID: US4394355A - Status: Granted - Kind: A - Application number: 06/354,251 - Filed: 1982-03-02 - Granted: 1983-07-19 - Earliest claimed: 1982-03-02 - Assignees: Celanese Corporation - Inventors: James D. Fruge' - Web page: https://patentgrep.com/patent/US4394355A ## CPC - C07C 51/412: {by conversion of the acids, their salts, esters or anhydrides with the same carboxylic acid part} - B01J 23/94: of catalysts comprising metals, oxides or hydroxides of the iron group metals or copper - C07C 51/418: {Preparation of metal complexes containing carboxylic acid moieties} - Y02P 20/584: Recycling of catalysts - C07C: ACYCLIC OR CARBOCYCLIC COMPOUNDS - B01J: CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS - Y02P: CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS ## Abstract 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. ## Claims ### Claim 1 In a process for treating a solid comprising the oxalate of a metal of the group consisting of cobalt, copper, and manganese to recover therefrom an aqueous solution containing a water-soluble salt of said metal substantially free from oxalate moiety, the improvement which comprises: leaching said solid with an aqueous solution of a water-soluble salt of ethylenediaminetetraacetic acid (EDTA) to form a leach liquor containing in solution the metal moiety of said metal oxalate in the form of the EDTA-metal complex; mixing said leach liquor with a solution containing dissolved calcium ions in a quantity at least stoichiometrically equivalent to the oxalate ions contained in said leach liquor to form a mixture comprising a precipitate of solid calcium oxalate and a solution containing said EDTA-metal complex; separating said calcium oxalate precipitate from said mixture to produce a clarified solution of said EDTA-metal complex; acidifying said clarified solution with an effective amount of a strong acid to decompose said complex to form solid EDTA and a dissolved salt of said metal; and removing said solid EDTA from said acidified solution leaving said metal salt dissolved therein. ### Claim 2 (depends on 1) The improvement of claim 1 wherein said solid comprising a metal oxalate comprises solid cobalt oxalate. ### Claim 3 (depends on 1) The improvement of claim 1 wherein said strong acid is a mineral acid other than sulfuric and wherein said metal is cobalt. ### Claim 4 (depends on 3) The improvement of claim 3 wherein said mineral acid is nitric acid. ### Claim 5 (depends on 2) The improvement of claim 2 wherein said solution containing dissolved calcium ions is calcium acetate dissolved in a liquid comprising predominantly acetic acid. ### Claim 6 (depends on 2) The improvement of claim 2 wherein said step of acidifying said clarified solution comprises adjusting the pH to about 0.0 to 0.5. ### Claim 7 (depends on 6) The improvement of claim 6 comprising the additional step of concentrating said clarified solution to a cobalt concentration of at least about 1% by weight after said separation of calcium oxalate precipitate and before said acidification step. ### Claim 8 In a process for oxidizing an organic feedstock with a catalyst comprising cobalt in a liquid phase comprising a carboxylic acid to produce a liquid oxidate comprising a carboxylic acid and wherein cobalt initially contained in said catalyst is converted to cobalt oxalate, in which process said cobalt oxalate is separated as a solid from said oxidate and converted to a cobalt salt which can be re-used as catalyst in said process, the improvement which comprises; leaching said solid with an aqueous solution of a water-soluble salt of ethylenediaminetetraacetic acid (EDTA) to form a leach liquor containing in solution the cobalt moiety of said cobalt oxalate in the form of the EDTA-cobalt complex: mixing said leach liquor with a solution containing a quantity of calcium ions sufficient to react with said complex to form a mixture comprising a precipitate of solid calcium oxalate and a solution containing said EDTA-cobalt complex; separating said calcium oxalate precipitate from said mixture to produce a remaining clarified solution of said EDTA cobalt complex; acidifying said clarified solution with an effective amount of a strong acid other than sulfuric acid to decompose said complex to form solid EDTA and a dissolved cobalt salt; removing said solid EDTA from said acidified solution leaving a clarified cobalt salt solution; and returning said clarified cobalt salt solution to said oxidation process for re-use as catalyst therein. ### Claim 9 (depends on 8) The improvement of claim 8 wherein said organic feedstock is an alkane or an aldehydoalkane and wherein said carboxylic acid is an oxygenated derivative of said alkane or aldehydoalkane.