Highly Selective Hydrogenation of Phenols to Cyclohexanone Derivatives Using a Palladium@N-Doped Carbon/SiO2 Catalyst

Abstract

A new palladium-based heterogeneous material was synthesized by means of immobilization of Pd(OAc)2/1,10-phenanthroline on commercially available SiO2 and subsequent pyrolysis at 600 °C for 2 h in air, namely, a Pd@N-doped carbon/SiO2 catalyst. The obtained catalyst was studied by X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), and X-ray photoelectron spectroscopy (XPS) techniques, and was effectively applied in the highly selective hydrogenation of phenols to give the corresponding cyclohexanone derivatives with 93–98% yields at 100 °C under 0.4 MPa H2 in EtOH. It was demonstrated that introducing nitrogen could effectively promote the Pd dispersion and enhance the electronic interaction of Pd, both of which facilitate the improvement of the catalytic activity and selectivity. The likely reaction pathway was outlined to elucidate the selective hydrogenation mechanism according to experimental results.