Tandem Reduction–Reoxidation Augments the Catalytic Activity of Sn-Beta Zeolites by Redispersion and Respeciation of SnO₂ Clusters

High dispersion of Sn in beta (?) zeolites is pivotal to obtain highly active Sn? catalysts with high productivity. However, at higher loadings, and the activity per decrease. The present work highlights augmentation catalytic Baeyer–Villiger oxidation Meerwein–Ponndorf–Verley reactions as-synthesized loadings up 10 wt % by tandem reduction–reoxidation discusses effect terms Lewis acid (LA) density, dispersion, speciation, performance. To do so, nontreated, reduced, reduced–reoxidized are characterized N2 physisorption, X-ray diffraction (XRD), a multitude spectroscopic techniques such as temperature-programmed reduction-mass spectrometry (TPR-MS), probe Fourier transform infrared (FTIR), diffuse reflectance ultraviolet–visible (DRUV–vis), 119Sn Mössbauer, magic angle spinning nuclear magnetic resonance (MAS NMR), inductively coupled plasma-atomic emission spectroscopy (ICP-AES), photoelectron (XPS). Although not mutually exclusive, seems arise from different phenomena depending on loading. At lower content (<5 %), arises redispersion SnO2 clusters into smaller species, whereas (?5 improve based respeciation clusters.