Deactivation of supported copper metal catalysts for hydrogenation reactions Original Research Article

Laboratory and industrial results are used to elucidate the general features of the deactivation of supported copper metal catalysts in hydrogenation reactions. Hydrogenations with copper catalysts are milder than with their nickel or platinum counterparts, and they have selectivities that are exploited commercially. They are used in single stream plants for production of hydrogen via the low-temperature water shift gas reaction, and for methanol manufacture from synthesis gas, and also in hydrogenation of speciality organic compounds. Common catalyst types are based on Cu/Cr2O3 (copper chromite) or Cu/ZnO formulations that contain stabilisers and promoters such as alkaline earth oxides and Al2O3. These have several roles, including inhibition of sintering, and poison traps that prevent poisoning of the active metal surface. The best understood are Cu/ZnO formulations that have improved sulphur resistance due to formation of thermodynamically stable ZnS. Copper catalysts are susceptible to thermal sintering via a surface migration process and this is markedly accelerated by the presence of even traces of chloride. Care must be, therefore, taken to eliminate halides from copper catalysts during manufacture, and from the reactants during use. Operating temperatures must be restricted, usually to below 300°C when catalyst longevity is important with large catalyst volumes.