(544bw) Mechanistic Insights into the Role of Zr Dopants in Ceria Based Ketonization Catalysts

To generate fuel and chemicals from biomass feedstocks, many processes often generate high concentrations of oxygenated molecules, which require further processing/upgrading. Ketonization reactions have recently gained considerable attention as one of the many routes employed to upgrade biomass-derived oxygenates; in these reactions, two carboxylic acid molecules undergo C-C coupling while releasing CO₂ and H₂O. To facilitate these reactions, metal oxides specifically ceria-based, have been reported to be effective catalysts.^1-3 Moreover, these metal oxides have shown increased ketonization activity through the incorporation of dopants^4-5 such as Zr, Mn, Fe, etc., but little is known at the fundamental level on how dopants affect catalytic activity. Among various explanations, increased ketonization activity of these mixed metal oxides (MMOs) has been linked with change in oxygen vacancies, redox properties, coordinative unsaturated cations, etc.⁶

This study is focused on understanding the role of Zr in ceria-zirconia MMOs for facilitating the ketonization reaction. More specifically, this seminar will cover electronic and structural changes in epitaxial thin films of Ce_xZr_1-xO₂ grown in ultrahigh vacuum conditions on Pt(111) substrates as a function of % Zr content. These electronic characteristics will be discussed in the context of ketonization activity though correlation with vibrational data of carboxylic adsorbates measured with High-Resolution Electron Loss Spectroscopy (HREELS).