Experimental Study on Microwave–SiC-Assisted Catalytic Hydrogenation of Phenol

Catalytic hydrogenation provides an important pathway for converting environmentally toxic phenol into less oxygenated and more stable useful chemical feedstock for the production of nylon and multicomponent diesel fuel. In this study, an innovative microwave–SiC-assisted heating technology was adopted to induce the vapor-phase catalytic hydrogenation of phenol over a Pd catalyst supported on Zr/Ce oxide. The H2 flow rate, catalyst support, and reaction temperature influenced the phenol conversion as well as product yield and selectivity. At a modest reaction temperature of 200 °C, the hydrogenation of phenol produced a mixture of cyclohexanol (COL) and cyclohexanone (CONE), and the COL/CONE molar ratio was influenced by the catalyst supports in the following order: Pd/CeO2 > Pd/ZrCeO2 > Pd/ZrO2. Under identical experimental conditions, the microwave–SiC-assisted hydrogenation exhibited superior performance over conventional hydrogenation in terms of both the phenol conversion and product yield. Particularly, the product selectivity of COL was remarkably enhanced for all catalyst types, primarily attributed to the abundant H• radicals, which were induced by electron collision as a result of microwave–SiC interaction, facilitating the hydrogenation of CONE into COL. In general, our innovative microwave–SiC-assisted hydrogenation presented a significant advantage in converting phenol into less-oxygenated compounds, hence providing an important reference for industrial practice.