Recovery of Co, Ni, Mo, and V from Unroasted Spent Hydrorefining Catalysts by Selective Chlorination

摘要

Spent hydrorefining catalysts may contain 4 to 6 pct of CoO and/or NiO, 8 to 16 pct of MoO_3, and up to 10 pct of V_2O_5, generally supported by alumina..They also contain up to 25 pct of carbon, hydrocarbons, and sulfur. Selective chlorination of raw, unroasted samples with Cl_2 + air, Cl_2 + N_2, and Cl_2 + CO + N_2 gas mixtures have been investigated for the recovery of valuable elements. The fastest chlorination kinetics are obtained using the Cl_2 + CO + N_2 gas mixture, followed by Cl_2 + N_2. The best selective chlorination of spent hydrorefining catalysts is obtained using a Cl_2 + air gas mixture. At temperatures lower than 600℃, it is possible to recover more than 90 pct of the Ni and Co, about 99 pct of the Mo, and up to 75 pct of the V compounds. Cobalt and Nickel chlorides are extracted from the chlorination residues by their dissolution with water. Molybdenum and Vanadium chlorides and/or oxychlorides are recovered by selective condensation from the vapor phase. The chlorination of the catalyst support, Al_2O_3, can be limited to less than about 6 pct. A flow sheet is proposed.