New insights into the role of Pd-Ce interface for methane activation on monolithic supported Pd catalysts: A step forward the development of novel PGM Three-Way Catalysts for natural gas fueled engines

摘要

This study reports a significant impact of the calcination temperature on the performances of Pd/Al2O3-CeO2 Three-Way-Catalysts to treat exhaust from natural gas fueled vehicles. Calcination from 550 degrees C to 950 degrees C led to Pd particles in the range 1.9-8.5 nm. It was found that PdO can be reduced to more active Pd-0 species under stoichiometric NGV conditions. More specifically, the 1.9 nm Pd particles, developing stronger Pd-Ce interaction were found more reducible and correspond to enhanced catalytic properties towards methane abatement. At high calcination temperature, corresponding to larger Pd particles, the deterioration of the Pd-Ce interface is accompanied with lower TOF jointly with higher activation barriers. Accordingly, the Pd-0-PdO interaction becomes prevalent to activate methane. Based on these observations, it was concluded that Pd-0-Ce and Pd-0-PdO interface related to the Pd particle size may be considered as criteria for identifying the performance of Pd-based NGV catalysts.