Toluene Oxidation Over Manganese Oxide Doped Palladium-Based Monolithic Catalyst Prepared by Electroless Composite Plating Method

The manganese oxide doped palladium-base catalyst on cordierite honeycomb ceramics (CHC) substrate (Pd–MnO _x /CHC) was prepared by electroless composite plating method. The results of scanning electron microscopy (SEM), energy dispersion X-ray spectrometer (EDS) and X-ray diffraction (XRD) showed that Pd component nanoparticles were dispersed more uniformly and compactly on the surface of Pd–MnO _x /CHC compared to mono palladium catalyst (Pd/CHC). This indicated that the addition of MnO _x could effectively prevent Pd nanoparticles from migration and coalescence during calcination treatment. The Pd–MnO _x /CHC catalyst also exhibited better low-temperature catalytic activity in toluene complete oxidation reaction: the light-off temperature (T10) and the complete oxidation temperature (T99) decreased 13 °C and 20 °C respectively compared to Pd/CHC. The results of X-ray photoelectron spectroscopy (XPS) analysis further indicated that the activity was controlled by the synergistic effect of PdO and Pd⁰ states, and the addition of MnO _x was favorable to maintain higher Pd⁰/PdO state ratio for Pd–MnO _x /CHC catalyst. Finally the reaction mechanism of toluene complete oxidation over Pd–MnO _x /CHC catalyst was also presumed.