Recovering metals from spent hydroprocessing catalysts

Claim 1

A process to recover the metal values from spent hydroprocessing catalyst particles, said values including: (i) at least one metal value selected from the Group consisting of cobalt and nickel; and (ii) at least one metal value selected from the Group consisting of vanadium, molybdenum and tungsten; comprising: (a) roasting the particles in an atmosphere containing molecular oxygen at a temperature in the range of between 400° C. and 600° C.; (b) leaching the particles with a first aqueous solution of ammonia and an ammonium salt at a temperature less than the atmospheric boiling point of said first aqueous solution, forming a first pregnant liquor and once-leached particles; (c) separating the once-leached particles from the first pregnant solution; (d) leaching the once-leached particles with a second aqueous solution containing sulfur dioxide, forming a second pregnant liquor and twice-leached particles; (e) separating the second pregnant liquor from the twice-leached particles; (f) precipitating metal sulfides from the second pregnant liquor by the addition of hydrogen sulfide; and (g) roasting said precipitated metal sulfides with fresh spent catalyst in step (a); (h) transferring said molybdenum, tungsten and vanadium metal values from said first pregnant liquor into a first organic solution by means of a first organic liquid extractant comprising a quaternary ammonium compound; (i) stripping said first organic solution with a first aqueous ammonium bicarbonate stripping solution to form an aqueous solution containing said molybdenum, tungsten and vanadium metal values; (j) transferring nickel values from said first pregnant liquor into a second organic solution by means of an organic nickel extractant comprising an oxime; (k) reducing cobalt metal values in said pregnant liquor to divalent cobalt; (l) transferring cobalt metal values from said pregnant liquor into a third organic solution by means of an organic cobalt extractant selected from the group consisting of dioximes, hydroxy-oximes, and beta-diketones; (m) stripping each of said second and third organic solutions with aqueous stripping solutions to form a cobalt-containing aqueous solution and a nickel-containing aqueous solution.