CATALYSTS EXTRACTING VALUES FROM SPENT HYDRODESULFURIZATION

1425349 Recovery of metals and alumina from hydrodesulphurization catalysts UNION CARBIDE CORP 13 April 1973 [14 April 1972] 17853/73 Heading C1A A process for extracting alumina and at least one of the values selected from vanadium and molybdenum from a spent hydrodesulphurization catalyst comprises first calcining the spent catalyst to reduce its carbon content (e.g. at 725‹ C.) followed by roasting the calcined catalyst (at, e.g. between 525‹ C. and 925‹ C. for a time period between 1 and 4 hours), in the presence of sodium chloride in an amount at least stoichiometric for the reactions: to substantially convert the vanadium and/or molybdenum values to the water soluble form; water leaching of the spent catalyst solubilizes the vanadium and/or molybdenum values while the alumina is retained in the residue and separated. The solution may be further treated with a tertiary amine to extract the metal values followed by stripping with, e.g. sodium carbonate solution and the vanadium may then be recovered by precipitation with ammonium sulphate at a pH of about 8, i.e. as ammonium metavanadate; the molybdenum remaining in the aqueous raffinate can be extracted with a tertiary amine and stripped with ammonia followed by acidification at 80‹ C. to precipitate ammonium tetramolybdate. The alumina may be recovered from the residue, as the hydroxide, by treatment with sodium hydroxide to dissolve the aluminium values followed by treating the filtrate containing sodium aluminate with acid to precipitate aluminium hydroxide; cobalt and nickel values which may be present in the spent catalyst collect in the residue obtained in the sodium hydroxide leaching.