Crystal Facet Structure Dependence and Promising Pd-Based Catalytic Materials for Resistance toward Deactivation and Catalytic Performance in Direct Oxidative Esterification
Hongxia Liu, Qiaoyun Qin, Jing Zhu, Jing Ma, Baohe Wang
Abstract
Designing an effective Pd-based catalytic material with higher stability and catalytic performance for direct oxidative esterification is a great challenge. In this work, a systematic study on the activation mechanism of H2O on the different crystal facets of monometallic Pd, bimetallic Pd–Pb(Bi), and trimetallic Pd–Pb–Bi catalysts was first performed, which showed that the (111) crystal facet of Pd–Pb–Bi had stronger stability of resistance toward deactivation induced by H2O. Further, a detailed direct oxidative esterification mechanism on the screened crystal facet was investigated, where Pd–Pb–Bi catalytic materials showed higher stability and intrinsic catalytic performance for direct oxidation esterification, which was attributed to a dimer Pd-active unit and the synergistic effect of Pb and Bi compared to that of Pd–Pb(Bi) and Pd and also applied to other aldehydes with electron-donating groups producing corresponding esters. Meanwhile, the essential relationship between structures of Pd-based catalytic materials and catalytic performance for direct oxidation esterification was obtained. This work opens up a new simultaneous path for improving the stability of resistance toward deactivation and catalytic performance for direct oxidative esterification of Pd-based catalytic materials, which can be realized by regulating the surface-active unit with dimer Pd adsorbed more O-preadsorbed using Pb and Bi promoters.