Chemistry Department Colloquium

Abstract: The large-scale availability of natural gas fuel sources has promoted considerable interest in methane conversion catalysts, either for after-treatment abatement applications or for conversion to higher value feedstock. In both cases, the activation of the CH4 molecule is hindered by its high stability and noble metal supported catalysts, such as Pd-CeO2, are often needed. However, the use of noble metals requires the optimization of the active phase in order to reach economic feasibility. In this talk, the successful application of a solvent-free mechano-chemical synthesis procedure will be presented, leading to highly active Pd-CeO2 catalysts for the conversion of methane under both excess and lean oxidative reaction conditions. Appropriate milling of palladium precursors and ceria powders (PdCeM) yielded novel Pd atomic sites closely interacting with the surface ceria lattice, resulting in enhanced selective oxidation of C-H bonds compared to traditional synthesized Pd-CeO2 catalysts (PdCeIW). Through a combination of activity evaluation tests in industrially relevant conditions and ex-situ and in-situ characterization techniques (XRD, XAFS, DRIFTS and AP-XPS analyses), we obtained insights in the enhanced reactivity of the PdCeM sample, highlighting the key roles of the nature of Pd sites as well as their interaction with the CeO2 lattice. These findings could aid in the rational design of Pd-based methane conversion catalysts.