Selective Hydrogenation of Phenol and Derivatives over Polymer-Functionalized Carbon-Nanofiber-Supported Palladium Using Sodium Formate as the Hydrogen Source.

Selective hydrogenation of phenol to cyclohexanone over a catalyst of polyaniline-functionalized carbon-nanofiber-supported palladium (Pd-PANI/CNF) with sodium formate as the hydrogen source has been studied. Phenol conversion exceeding 99 % was achieved with a cyclohexanone selectivity of >99 % in aqueous media. In an extension to Pd-PANI/CNF, polymers such as polypyrrole (PPY), poly(4-vinylpyridine) (PVP), and poly(1-vinylimidazole) (PVI) were further applied to a catalyst of Pd-polymer/CNF for selective phenol hydrogenation. All of the Pd-polymer/CNF catalysts showed excellent to good performance toward selective phenol hydrogenation. However, Pd-PANI/CNF was considerably more active and selective to afford the desired cyclohexanone than Pd-PPY/CNF, Pd-PVP/CNF, and Pd-PVI/CNF. Moreover, a series of phenol-derived compounds were selectively hydrogenated in high yields under the investigated aqueous conditions. The research highlights an environmentally benign and effective process for the selective reduction of phenol derivatives with sodium formate as an alternative hydrogen source.