Leaching cobalt, molybdenum, nickel, and vanadium from spent hydroprocessing catalysts

Abstract From the Canadian patent

A process is disclosed to extract metal values selected from the group consisting of cobalt molybdenum, nickel, tungsten, and vanadium from metal-containing particles, such as spent hydroprocessing catalyst particles containing carbon residue. In this process the, spent catalyst particles are roasted in an oxygencontaining gas at a temperature of from 400°C to 600°C and then the roasted catalyst particles are contacted with an aqueous solution of ammonia, ammonium salt and, hydrogen peroxide. That aqueous solution has an initial pH of at least 9.5 and an initial hydrogen peroxide concentration of from 0.02 to 0.2 M. That aqueous solution is maintained at a pH of greater than 9.5.