Tailoring Locations and Electronic States of Rh Nanoparticles in KL Zeolite by Varying the Reduction Temperature for Selective Phenol Hydrogenation

In this study, we employed a top-down strategy, which entailed first the in situ encapsulation of Rh species within the one-dimensional KL channels and then the reduction of catalysts at different temperatures, to tailor the locations and electronic states of the Rh nanoparticles in KL channels for selective phenol hydrogenation under mild conditions. Kinetic studies revealed that with the reduction temperature increasing from 100 to 300 °C, Rh catalysts showed improved activity, while they demonstrated similar time profiles. The cyclohexanone selectivity of 82.4% could be obtained at the phenol conversion of 72.2%, which remained unchanged after recycling seven times. X-ray photoelectron spectroscopy (XPS) and in situ CO adsorption Fourier transform infrared spectroscopy (FT-IR) analyses indicated that the improved activity might be attributed to the more electron-rich chemical state of Rh nanoparticles as there were more probabilities to accept electrons from potassium when Rh nanoparticles migrated from the central location to the edge or surface of the KL zeolite.