FT-IR characterization of alkali-doped Pd catalysts for the selective hydrogenation of phenol to cyclohexanone

A detailed FT-IR investigation of CO, phenol and cyclohexanone adsorbed on alkali-doped Pd catalysts has been carried out in order to get information on the influence of the support and of the addition of promoters (alkali or alkaline earth metals) on the catalytic performance of Pd-supported catalysts in the selective hydrogenation of phenol. The obtained results are consistent with a mechanism that involves the reaction of phenol, adsorbed on the support as a phenolate species, located nearby Pd sites on which hydrogen is activated. The basicity of the support plays an important role in the adsorption of the phenol. Promoters have been found to modify the electronic properties of the palladium sites.