PNNL

Abstract

Industrial low-temperature methane combustion catalyst Pd/Al2O3 suffers from H2O-induced deactivation. It is imperative to design new Pd catalysts free from this deactivation and with high atomic efficiency. Using a small-pore zeolite SSZ-13 as support, herein we report well-defined Pd catalysts with dominant active species as isolated Pd2+ cations, uniform PdO particles embedded inside the zeolite framework, or PdO particles decorating the zeolite external surface. Through detailed reaction kinetics, spectroscopic and microscopic studies, we show that isolated sites are much less active than PdO nanoparticles. We further demonstrate that H2O-induced deactivation can be readily circumvented by tuning the support hydrophobicity. Finally, we provide a few rational catalyst design suggestions for methane oxidation based on the new knowledge learned in this study.