Understanding Palladium Hydrogenation Catalysts:When the Nature of the Reactive Molecule Controls the Nature of the Catalyst Active Phase

摘要

Catalytic hydrogenations are one of the most important processes in the chemical industry and selectivity is a timely issue.The presence of triple-bonded compounds in the alkene stream is undesirable in both chemical and polymer-grade propylene and ethylene,as they poison the polymerization catalysts.Starting with a mixture of alkynes and alkenes,palladium-based catalysts are known to be capable of selectively hydrogenating triple bonds,leaving the olefinic function intact.The presence of carbonaceous deposits was assumed to play a key role,influencing the performance of the catalyst.Although the origin of this behavior is unknown,very recently a relation between selectivity and subsurface chemistry has been established,showing that the population,by either hydrogen or carbon,of subsurface sites of palladium governs selective alkyne hydrogenation.Hydrogen in the subsurface is known to play a crucial role in hydrogenating surface species effectively.