Elucidating the mechanism of heterogeneous Wacker oxidation over Pd-Cu/zeolite Y by transient XAS

We investigated the mechanism of ethylene oxidation over Pd-Cu/zeolite Y by means of transient X-ray absorption spectroscopic (XAS) combined with kinetic studies and chemometric analysis. Through this, the dynamic speciation of the metal centers in the catalyst under steady state and transient conditions involving oxygen switching experiments were determined. Mechanistic insights were extracted revealing a rapid redox reaction involving copper, demonstrating that copper is not only the site of oxygen activation, but is also involved in the formation of undesired carbon dioxide. Not only could we use this mechanistic information to design more energy-efficient catalysts, but the synergistic combination of the state-of-the-art techniques used in this study could also be potentially applied to investigate other catalytic processes. As the first XAS study ever on heterogeneous or homogeneous Wacker oxidation, this could set a precedent for more future studies that could fill the gaps in the understanding of the process.