Value recovery from spent alumina-base catalyst

A process for the recovery of aluminum and molybdenum from a spent hydrodesulfurization catalyst comprising molybdenum and at least one catalytically active metal selected from the group consisting of nickel and cobalt and carbonaceous matter deposited on a refractory alumina-containing inorganic oxide support, said process comprising adding about 1 to 3 parts concentrated H.sub.2 SO.sub.4 per part of hydrodesulfurization catalyst in a reaction zone at about 20.degree. to 200.degree. C. and in the presence of elemental sulfur or hydrogen sulfide gas at a pressure of between 2 and about 35 atmospheres, maintaining the resultant mixture in the reaction zone until the alumina in the catalyst is substantially completely dissolved, and a metal sulfide precipitate is formed from said molybdenum and said at least one other metal, and mechanically separating the resultant Al.sub.2 (SO.sub.4).sub.3 solution from the resultant metal oxide-containing solid residue.

A process for the recovery of solid molybdic acid from an aqueous slurry comprising sulfides of molybdenum and at least one other metal selected from the group consisting of cobalt and nickel, comprising oxidizing said sulfides at about 20.degree. to 200.degree. C. and in an oxygen atmosphere at a pressure between about 1 and about 35 atmospheres, mechanically separating the slurry to obtain resulting solid molybdic acid and an aqueous metal sulfate solution comprising dissolved molybdenum and said at least one other metal, and separating and recovering said at least one other metal from the sulfate solution containing the dissolved molybdenum.