ABSTRACT
Carbon particles generally are basic, and if they are sufficiently basic, it is unnecessary for them to be pretreated in order to effect precipitation of the precious metals. However, if the precious metals content is above 5%, it is preferable and safest to pretreat the catalyst support with alkali to expedite and make complete the precipitation. Regeneration of palladium or other precious metals on carbon is very difficult, and no general instructions are possible. If the deactivating agent is a wax, polymer, or high-boiling organic, the first scheme to try would be solvent extraction because the carbon support would also oxidize during an oxidation of the organic contaminant. "Decrepitate" refers to the breaking away of the exterior portion and the almost complete disintegration of the sphere into particulate matter. This decrepitation can be avoided by preliminary moisture treatment of the spheres with steam in the vapor phase at approximately 125°C.
