Activity enhancement of core–shell Pd@mCeO2 catalysts for phenol hydrogenation to cyclohexanone by tuning metal-support interactions

Abstract

A core–shell catalyst composed of mCeO2 shell and Pd metal core was prepared by one-pot wet chemical method and used for the hydrogenation of phenol to cyclohexanone. The phenol conversion and cyclohexanone selectivity were 96.3 % and 95.3 % at reaction conditions of 50 min, 80 °C and 1 MPa H2. The effects of Ce species and Br species in the preparation of catalysts was studied, and the synthesis mechanism of core–shell Pd@mCeO2 catalysts was preliminarily revealed. By discussing the phenol adsorption mechanism and the redox properties of the catalyst, the activation of H2 by Pd sites and phenol by cerium oxide (CeO2) sites of the surface were studied. H2-TPR and XPS characterization were used to explain the effect of Ce species and Br species for the catalytic performance. These results indicated that the electronic structure of Pd was regulated by the interaction between Pd and Ce, and different O sites were generated around the Pd sites. In situ IR spectra indicated that phenol was adsorbed and dissociated on cerium to form phenoxy species and water, this synergistic catalytic pattern of carrier activated substrate and hydrogenation site promoted the hydrogenation of phenol and improved the catalytic efficiency.