Solid base catalysts for mercaptan oxidation

Aqueous alkali can be completely replaced in the mercaptan oxidation reaction by incorporating solid basic materials into the catalyst formulation. The ability to use a solid oxide base to replace aqueous alkali will have a positive environmental impact because aqueous alkalis, such as caustic, are becoming a serious disposal problems for petroleum refiners and chemical manufacturers. The basic oxide system used contains cobalt phthalocyanine (CoPc) supported on a metal oxide solid solution (MOSS). Although active for mercaptan oxidation, this catalyst does not meet the lifetime requirements for commercial application. Three deactivation mechanisms have been identified: rehydration of the MOSS back to the layered double hydroxide (LDH) (because this rehydration causes a reduction in the basicity of these materials), deactivation by adsorption of heavy hydrocarbon species in the feed, and irreversible adsorption of acidic species from the feed. Knowledge of the deactivation mechanisms has allowed the design of a process that meets the required catalyst lifetime requirements. This process represents one of the first applications of solid base catalysis to a commercial process. Catalyst performance, factors affecting deactivation, and methods of preventing deactivation are discussed. (C) 1998 Elsevier Science B.V. All rights reserved.