Copper Phyllosilicate Nanotube Catalysts for the Chemosynthesis of Cyclohexane via Hydrodeoxygenation of Phenol

In the utilization of renewable resources derived from biomass, hydrodeoxygenation (HDO) is one of the most critical steps in the bio-oil upgrading process. Herein, a series of copper phyllosilicate nanotube (CuPSNT) catalysts were successfully prepared and applied in the chemosynthesis of cyclohexane via the phenol HDO reaction. Against the presumption that mono-metal copper was not active for the complete hydrogenation of aromatic compounds, a cyclohexane yield of 97.8% at the total conversion of phenol was achieved at 230 °C on the CuPSNT catalysts with a Cu/Si ratio of 1:1. The kinetic analysis suggested that further conversion of cyclohexanol to cyclohexane is the rate-determining step in the phenol HDO. Cu0 accounts for the hydrogenation, while Cu+ is responsible for the adsorption of phenol and cyclohexanol and in charge of further cyclohexanol dehydration. This conclusion is further confirmed by density functional theory calculations. This work demonstrates that the synergy between Cu0 and Cu+ species of CuPSNT catalysts plays a critical role in the HDO process of phenol, and mono-metal Cu can accomplish both the saturation of aromatic rings and the removal of oxygen groups.