In-situ Monitoring of Reactive Intermediates in Heterogeneous Oxidation Catalysts via Ti L2,3-Edge NEXAFS

Ti-zeotypes play a major role in sustainable industrial oxidation catalysis. Despite large research efforts, to date, many aspects about this family of catalysts remain unclear, including the nature of the active site, in part due to the limited availability of direct (metal-centered) characterization techniques with molecular-level resolution. Peroxo adducts of Ti-zeotypes are being proposed as key intermediates in the epoxidation of propylene and ammoximation of ketones, but their precise molecular structure (mono or dinculear, hydroperoxo, etc.) is heavily debated. In this proposal, we aim to extend our previously developed Ti L2,3-edge NEXAFS methodology for molecular peroxo complexes to the industrial heterogenous catalyst. In situ characterization at the L2,3-edge of early transition metals has rarely been attempted, but is available at ID20. Resolving the structure of the peroxo-intermediate based on direct characterization will have a broad impact in the zeolite community.