Effect of Pd loading on ZrO₂ support resulting from pyrolysis of UiO-66: Application to CO oxidation

The effect of Pd loading (0.25, 0.5 and 1.0 wt%) and ZrO₂ support calcined at diverse temperatures (600, 700 and 800 °C) by pyrolysis of UiO-66 was investigated for CO oxidation in this work, respectively. The physicochemical properties of the samples were characterized by various characterization methods. The XRD results exhibited that all ZrO₂ support possessed mixed crystalline phase, the monoclinic ZrO₂ and tetragonal ZrO₂. And the calcination temperature had a big impact on the composition of ZrO₂ supports. Pyrolysis of UiO-66 at high temperature was favorable for the formation of monoclinic ZrO₂. Additionally, the introduction of Pd was induced the phase conversion from tetragonal to monoclinic of ZrO₂. The order of catalytic efficiency was as follows: 0.5Pd/Zr-700 > 0.5Pd/Zr-600 > 0.5Pd/Zr-800. Moreover, 0.5Pd/Zr-700 presented high stability and great reusability. The good catalytic performance of 0.5Pd/Zr-700 was ascribed to the better reduction ability at low temperature and high O_ads/O_lat and Pd⁰/Pd²⁺ on the surface. Importantly, the reaction pathway of CO oxidation over the 0.5Pd/Zr-700 was exposed.