Low temperature selective chlorination of used catalysts for the recovery of transition and/or refractory metals
- INPL, Vandoeuvre (France)
- INASMET Centro Tecnologico de Materiales, San Sebastian (Spain)
Selective chlorination of unroasted and roasted spent hydrorefining catalysts was studied between 300 and 600 C using the following gas mixtures: Cl{sub 2} + CO, Cl{sub 2} + N{sub 2} and Cl{sub 2} + air. Such materials contain Co, Ni and Mo compounds supported by alumina and/or silica. They also contain variable amounts of V compounds, C, S, etc., accumulated during the life time of the catalyst. Direct oxychlorination of the C+S rich sample allows higher extraction rates than those obtained by the carbochlorination of the same roasted one. Cobalt and nickel chlorides were extracted from the chlorination residues by their dissolution with acidified water, whereas molybdenum and vanadium chlorinated compounds were recovered by selective condensation from the vapor phase. The recovery rates of valuable metals as well as the selectivity were higher for the chlorination of spent catalysts than results obtained by the hydrometallurgical processing of the same sample. The global recovery rates were about 88 pct of cobalt, 93 pct of molybdenum and 76 pct of vanadium. The carbochlorination was applied to the recovery of W and Ti from Denox catalyst that is a carbon and sulfur free one. Recovery rates higher than 99 pct at temperatures lower than 500 C could be obtained. This may indicate that the chlorination process can be applied to the treatment of various industrial wastes or by-product containing transition and/or refractory metal compounds. A flow sheet for the retreatment of these materials is proposed. 45 refs., 11 figs., 9 tabs.
- OSTI ID:
- 197262
- Report Number(s):
- CONF-951105--; ISBN 0-87339-318-X
- Country of Publication:
- United States
- Language:
- English
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