Lanthanum-promoted Pd/Al2O3 catalysts for liquid phase in situ hydrogenation of phenol to cyclohexanone

Abstract

A series of lanthanum-promoted Pd/Al2O3 catalysts (Pd/La x –Al2O3), for the liquid phase in situ hydrogenation of phenol into cyclohexanone, was prepared by the incipient wetness impregnation method. Addition of lanthanum to Pd/Al2O3 enhances the TOF of the catalyst for the liquid phase in situ hydrogenation of phenol significantly. The conversion of phenol is highly dependent upon the atomic ratio of La/Pd, but the presence of lanthanum has little effect on the selectivity of cyclohexanone. The selectivity of cyclohexanone in the liquid phase in situ hydrogenation of phenol over the Pd/La x –Al2O3 catalyst is as high as 98%, which is quite higher than the hydrogenation using H2 (67.4%). Results from BET, EDS, CO chemosorption, XRD and H2-TPR suggest that the presence of suitable amounts of lanthanum improves the Pd dispersion on the support. The peak temperature for the reduction of PdO in the H2-TPR moves to higher in the presence of lanthanum. Additionally, the Pd particles could adhere to the lanthanum rather than the Al2O3.