Highly selective Pd@mpg-C3N4catalyst for phenolhydrogenation in aqueous phase

Abstract

The liquid phase selective hydrogenation of phenol to cyclohexanone has been investigated over polymeric mesoporous graphitic carbon nitride (mpg–C₃N₄) supported Pd catalysts (Pd@mpg-C₃N₄). This Pd@mpg-C₃N₄ is shown to be highly active and promotes the selective formation of cyclohexanone (∼99%), an industrially important compound, in a “one-step” method. The effects of different variables like solvent, reaction temperature, catalyst texture and catalyst pre-treatment are presented and discussed. The different adsorption capacity of mpg–C₃N₄ between the phenol and cyclohexanone is suggested to strongly promote the chemoselective reduction of phenol to cyclohexanone and avoid the deep hydrogenation of cyclohexanone to cyclohexanol. The hydrogenation kinetics has been adequately represented by a standard pseudo-first-order approximation, and isotopic tracing study and the transition state calculation were applied for the discussion of the possible reaction mechanism.