What processes are currently available to recover precious metals from spent catalysts?
Answers
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28/07/2007
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A:
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Trin Thomas, Heraeus, trin.thomas@heraeus.com
There are two proven methods for the recovery of precious metals from spent catalysts. Hydro-metallurgy is generally used as the best application resulting in highest precious metals yields when high surface alumina catalysts are being recovered. Typically, more than 50% of these catalysts contain the high value metal rhenium (Re) as well, which can only be recovered using this method. The use of either the alkaline or sulfuric acid leach process depends mainly on the infrastructure to dispose off Al by-products. At Heraeus the alkaline pressure leach is used in Hanau, Germany, to initiate the recovery process while sulfuric acid leach is used in Santa Fe Springs, California. Both methods produce similar results.
Pyro-metallurgy is generally used when zeolyte substrate catalysts are being recovered. This employs traditional ‘smelting’ technology. This method is also preferred when a gamma-based catalyst has been subjected to extreme temperatures during operation and subsequently suffered a major alumina phase change, rendering the substrate highly insoluble.
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