Cyclic process for recovering metal values and alumina from spent catalysts
AssigneeAmax Inc.
InventorsEdward I. Wiewiorowski, Luther R. Tinnin, Ranko Crnojevich
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Abstract
Metal values and alumina are recovered from spent, usually oily, catalysts by oxygen pressure leaching with sodium hydroxide and/or sodium aluminate to dissolve molybdenum, vanadium and/or tungsten and provide a solid, filterable residue containing alumina and cobalt and/or nickel, the residue is digested with sodium hydroxide to give a sodium aluminate solution and a residue enriched in nickel and/or cobalt, alumina is recovered from the sodium aluminate solution as a solid and the remaining supernatant solution is recycled to the oxygen pressure leaching step wherein the alumina content of the aluminate solution is precipitated and a bleed for metals in the aluminate solution is provided.
Claims12
The process for treating spent alumina catalyst containing molybdenum, vanadium and at least one metal from the group consisting of nickel and cobalt to recover the constituents thereof which comprises the steps of:
- (a) oxygen pressure leaching an aqueous slurry of said catalyst at a temperature of at least about 300.degree. F. with an alkali from the group consisting of sodium aluminate and sodium hydroxide to dissolve molybdenum and vanadium selectively from said catalyst to provide, at the conclusion of the leach, an aqueous solution having a pH not greater than about pH 9 and containing no more than about 100 ppm aluminum while retaining alumina along with catalyst-contained nickel and cobalt in a residue;
- (b) separating the resulting aqueous solution containing said molybdenum and vanadium from said residue;
- (c) digesting said residue with sodium hydroxide in a concentration at least sufficient to dissolve alumina to provide a caustic solution containing said aluminum and a residue containing said nickel and cobalt;
- (d) separating said aluminum-containing solution from said residue;
- (e) precipitating alumina from said aluminum-containing solution;
- (f) separating said precipitated alumina from the supernatant caustic solution;
- and
- (g) recycling caustic solution from step (f) to said selective leaching step whereby soluble aluminum in said caustic solution is converted to an insoluble mineral.
The process for treating an oily, spent hydrodesulfurization catalyst containing aluminum, molybdenum, vanadium, at least one metal from the group consisting of nickel and cobalt, and sulfur which comprises slurrying said catalyst with an aqueous alkali solution from the group consisting of sodium hydroxide and sodium aluminate containing an amount of alkali stoichiometrically at least equivalent to convert the molybdenum, vanadium and sulfur contents of said spent catalyst to sodium molybdate, sodium vanadate and sodium sulfate, oxygen pressure leaching the resulting slurry at a temperature of at least about 200.degree. C. for a time sufficient to oxidize to carbon dioxide substantially all the carbon in said spent catalyst and to dissolve molybdenum and vanadium to provide, at the conclusion of the leach, an aqueous solution having a pH not exceeding about pH 9 and containing no more than about 100 ppm aluminum while producing a solid containing the aluminum, nickel and cobalt, separating the liquid containing said molybdenum and vanadium from said solid, digesting said solid with sodium hydroxide to produce a sodium aluminate solution and a residue containing said nickel and cobalt, removing alumina from said sodium aluminate solution by seeded crystallization and recycling sodium aluminate from said solution to said oxygen pressure leaching step.
Dependencies are inferred from the claim text.