Metals recovery from spent catalyst

A method for recovering metals from a deoiled spent catalyst, the method comprising:

• heating a deoiled spent catalyst comprising a Group VIB metal, a Group Vill 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;
• wherein, the oxidative heating conditions comprise heating the deoiled spent catalyst at the first pre-selected temperature in the presence of air, or a gas mixture comprising no more than about 20 vol. % oxygen followed by heating the deoiled spent catalyst at the first pre-selected temperature under gas conditions comprising more than about 80 vol. % oxygen;
• or,
• wherein the gas flow conditions comprise an inert gas and are sufficient to remove any off-gases.