Insights into Microstructure and Surface Properties of Pd/C for Liquid Phase Phenol Hydrogenation to Cyclohexanone

Phenol hydrogenation over Pd/C is a promising technology to produce cyclohexanone, but how to select the carbon supports is not clear. Herein, three types of activated carbon, i.e., produced from coal (C-C), coconut shell (C-CS) and wood (C-W), were selected for the synthesis of Pd/C. The Pd/C catalysts show significant differences in the phenol hydrogenation, and the catalytic activity is in the order of Pd/C-W > Pd/C-CS > Pd/C-C. For example, the phenol conversion of Pd/C-W is 81.6% in dichloromethane, about 4 times higher than that of Pd/C-C. Moreover, Pd/C-W can achieve a phenol conversion of 97.2% with a cyclohexanone selectivity of 97.4% in n-hexane, and has good reusability during at least five reaction cycles. Larger surface area, higher surface N and O contents, more surface defects, abundant acidic and alkaline sites are the key reasons for the superior catalytic activity of Pd/C-W as compared to Pd/C-CS and Pd/C–C. Graphical Abstract: The type of activated carbon has a remarkable effect on the microstructure and surface properties of Pd/C, and the corresponding catalytic properties for the liquid phase phenol hydrogenation to cyclohexanone. Larger surface area, higher surface N and O contents, more surface defects, abundant acidic and alkaline sites are the key reasons for the superior catalytic activity of Pd/C-W as compared to Pd/C-CS and Pd/C-C. [Figure not available: see fulltext.]