Effect of preparation method on the performance of Pd-MnOx/γ-Al2O3 monolithic catalysts for ground-level O3 decomposition

Abstract

MnOx +γ-Al2O3 and MnOx/γ-Al2O3 catalysts were prepared by the sol-gel and sequential precipitation methods, respectively. The same amount of Pd was loaded on these catalysts by incipient wetness impregnation. The two Pd-MnOx/γ-Al2O3 catalysts with different physicochemical properties were coated on cordierite. The catalysts were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, H2 temperature-programmed reduction, and N2 adsorption-desorption measurement. The preparation method and calcination temperature of MnOx have significant impact on the crystalline phase of MnOx, MnOx species and active oxygen species, and textural properties of the catalysts. The experimental results showed that 0.60 μL·L−1 of ozone was completely decomposed on these catalysts in the temperature range of 16 to 90°C at space velocities from 380000 to 580000 h−1. In particular, the activity for O3 decomposition was excellent on the Pd/MnOx+Pd/γ-Al2O3 catalyst that used MnOx prepared by the sol-gel method. Mnn+ is beneficial for O3 decomposition, and Mn2+, Mn3+, and Mn4+ were presented in a mole ratio of 1.7:1:3 on the surface of the catalyst.