Multifunctional mesoporous silica-supported palladium nanoparticles for selective phenol hydrogenation in the aqueous phase

Abstract

A simple, efficient and recoverable palladium-based catalyst was successfully prepared by immobilizing palladium nanoparticles (Pd NPs) over hydrophobic core–hydrophilic shell structured mesoporous silica microspheres. The obtained catalyst was characterized by transmission electron microscopy (TEM), N₂ adsorption–desorption, Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA) and X-ray photoelectron spectroscopy (XPS). The as-prepared catalyst could rapidly convert phenol to cyclohexanone with 98.5% conversion and 97.1% selectivity under mild reaction conditions in the aqueous phase (1 atm H₂, 80 °C, 3 h). The excellent catalytic performance of the Pd/MS-C₃@MS-NH₂ catalyst was probably attributed to the enhanced synergistic effect between highly dispersed Pd NPs and significantly decreased phenol mass transfer resistance. In addition, it could be easily recovered by centrifugation and reused 5 times without any significant loss in activity and selectivity.