Highly Dispersed Pd Clusters in Zeolite USY for Effective Hydrogenation of Naphthalene

Pd-based catalysts with different Pd species (Pd ions, Pd clusters, and Pd nanoparticles) in USY were synthesized for naphthalene hydrogenation reaction. Among the catalysts, Pd clusters were prepared by controlled aggregation of Pd ions during the hydrogenation reaction with the assistance of physically adsorbed water in zeolite micropore. The coordination state and electronic structure of Pd species on these catalysts were analyzed to reveal the structure–performance relationship. Due to the high dispersion and optimized electronic structure, Pd clusters showed the highest activity for naphthalene hydrogenation compared to Pd ions and Pd nanoparticles.