Highly Efficient Phenol Hydrogenation to Cyclohexanone over Pd@CN-rGO in Aqueous Phase

Two-dimensional N-doped Pd/carbon for highly efficient heterogeneous catalysis

A novel two-dimensional ZIF-derived Pd@CN material prepared via one-step calcination exhibits outstanding catalytic activity in heterogeneous hydrogenation. Its well-developed porous structure, low dimensions and low density make active sites more accessible. This facile and effective strategy can guide the synthesis of highly active and durable Pd@CN catalysts with specific morphologies.

Highly selective hydrogenation of phenol to cyclohexanone over a Pd-loaded N-doped carbon catalyst derived from chitosan

A highly stable Pd-loaded N-doped carbon catalyst (ACN_pd) for phenol hydrogenation was prepared from chitosan by hydrothermal carbonization. ACN_pd does not require a reduction step before catalytic use due to the Pd in the as-prepared catalyst mainly exists in the form of Pd⁰ (80%). The carbon support involves N-containing groups such as pyridinic nitrogen and pyrrolic nitrogen, which could provide basic sites to adsorb phenol effectively. The as-fabricated ACN_pd shows high catalytic performance with turnover frequency (TOF) of 29.34 h^-1. Accordingly, a phenol conversion of 100% and a cyclohexanone selectivity of 99.1% are achieved in 5 h at 100 °C and 1 MPa H₂. This outstanding performance is attributed to the synergetic effects of the Pd particles, the N-functional groups, and the Lewis acid sites on the support. The carbon support presents intrinsic Lewis acid sites due to its electrophilicity, and Pd doping further increases the strength of such acid sites as it causes electron-deficient structural features. Moreover, the Lewis acid sites inhibit the over-hydrogenation from cyclohexanone to cyclohexanol. This study provides new insights into the application of functional biomass-based carbon materials as catalyst supports.