Highly Selective Cleavage Dehydrogenation of BPZ for Preparation of p-Phenylphenol over Efficient Pd–Cu/TiO2 Bimetallic Catalysts

Pd–Cu bimetallic catalysts were successfully synthesized for the dehydrogenation of Bisphenol Z (BPZ) by an impregnation-reduction method. The obtained catalyst was studied by XRD, HRTEM, XPS, BET, and NH3-TPD techniques and effectively applied in the highly selective cleavage dehydrogenation of BPZ to give PPP > 99% yield at 270 °C and atmospheric pressure in the solvent-free condition. It was demonstrated that the “synergistic effect” of the bimetallic catalysts could effectively promote the cleavage dehydrogenation reaction. Pd species served as the primary active sites for the adsorption and dissociation of H* and the activation of C–H bonds, while the introduced Cu species accelerated the breaking process of the C–H bond. This catalyst demonstrated remarkable stability and could be reused over ten cycles without obvious decrease both in yield and selectivity. The likely reaction pathway was outlined to elucidate the cleavage dehydrogenation mechanism according to experimental results.