Effect of Pd loading on ZrO 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 ZrO 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 ZrO support possessed mixed crystalline phase, the monoclinic ZrO and tetragonal ZrO. And the calcination temperature had a big impact on the composition of ZrO supports. Pyrolysis of UiO-66 at high temperature was favorable for the formation of monoclinic ZrO. Additionally, the introduction of Pd was induced the phase conversion from tetragonal to monoclinic of ZrO. 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/O and Pd/Pd on the surface. Importantly, the reaction pathway of CO oxidation over the 0.5Pd/Zr-700 was exposed.