Metals recovery from spent catalyst

A method for separately recovering Group VIB and Group VB metal compounds from an aqueous mixture comprising Group VIB and Group VB metal compounds, the method comprising:

• contacting the Group VIB and Group VB metal compound aqueous mixture with an ammonium salt under metathesis reaction conditions effective to convert the metal compounds to ammonium Group VB metal and ammonium Group VIB metal compounds;
• subjecting the mixture comprising the ammonium Group VB metal compound to conditions effective to crystallize the ammonium Group VB metal compound;
• filtering and washing the crystallized ammonium Group VB metal compound with a saturated ammonium Group VB metal compound wash solution at a pre-selected wash temperature and separately recovering the ammonium Group VB metal compound and an ammonium Group VIB metal compound filtrate;
• heating the ammonium Group VB metal compound under conditions effective to release ammonia and separately recovering the Group VB metal compound and ammonia;
• contacting the ammonium Group VIB metal compound filtrate with an inorganic acid under conditions effective to form a Group VIB metal oxide compound precipitate and an ammonium salt of the inorganic acid;
• filtering and washing the Group VIB metal oxide compound precipitate with a saturated ammonium Group VIB metal oxide compound wash solution at a pre-selected wash temperature and recovering the Group VIB metal oxide compound precipitate.

A combined pyrometallurgical and hydrometallurgical method for recovering metals from a deoiled spent catalyst, the combined method comprising:

• heating a deoiled spent catalyst comprising a Group VIB metal, a Group VIII metal, and a Group VB metal under oxidative conditions at a first pre-selected temperature for a first time sufficient to reduce the levels of sulfur and carbon to less than pre-selected amounts and to form a calcined spent catalyst;
• contacting the calcined spent catalyst with a caustic leach solution to form a spent catalyst slurry at a pre-selected leach temperature for a pre-selected leach time and at a pre-selected leach pH;
• separating and removing a first filtrate and a first solid residue from the spent catalyst slurry, the first filtrate comprising a soluble Group VIB metal compound and a soluble Group VB metal compound and the first solid residue comprising an insoluble Group VIII/Group VIB/Group VB metal compound;
• drying the insoluble Group VIII/Group VIB/Group VB metal compound first solid residue;
• combining the dried Group VIII/Group VIB/Group VB metal compound first solid residue with anhydrous soda ash to form a solid residue/soda ash mixture;
• heating the metal compound solid residue/soda ash mixture at a second pre-selected temperature and for a second pre-selected time under gas flow conditions to form a soda ash calcine;
• contacting the soda ash calcine with water to form a soda ash calcine slurry at a temperature and for a time sufficient to leach a soluble Group VIB metal compound and a soluble Group VB metal compound from the soda ash calcine;
• separating and removing a second filtrate and a second solid residue from the soda ash calcine slurry, the second filtrate comprising the soluble Group VIB metal compound and the soluble Group VB metal compound and the second solid residue comprising an insoluble Group VIII metal compound;
• and
• recovering the soluble Group VIB metal compound and the soluble Group VB metal compound from the spent catalyst slurry first filtrate and from the soda ash calcine slurry second filtrate;
• combining the first filtrate and the second filtrate and contacting the aqueous mixture with an ammonium salt under metathesis reaction conditions effective to convert the metal compounds to ammonium Group VB metal and ammonium Group VIB metal compounds;
• subjecting the mixture comprising the ammonium Group VB metal compound to conditions effective to crystallize the ammonium Group VB metal compound;
• filtering and washing the crystallized ammonium Group VB metal compound with a saturated ammonium Group VB metal compound wash solution at a pre-selected wash temperature and separately recovering the ammonium Group VB metal compound and an ammonium Group VIB metal compound filtrate;
• heating the ammonium Group VB metal compound under conditions effective to release ammonia and separately recovering the Group VB metal compound and ammonia;
• contacting the ammonium Group VIB metal compound filtrate with an inorganic acid under conditions effective to form a Group VIB metal oxide compound precipitate and an ammonium salt of the inorganic acid;
• filtering and washing the Group VIB metal oxide compound precipitate with a saturated ammonium Group VIB metal oxide compound wash solution at a pre-selected wash temperature and recovering the Group VIB metal oxide compound precipitate.