(35e) Nanostructured, Single Site Titanium-Silicate Catalysts with Varying Support Connectivities – Correlating Site Structure with Activity in the Oxidation of Trimethylphenol to Benzoquinone

A family of atomically dispersed titanium in/on silicate catalysts has been prepared and characterized via DRUV, XAS (XANES and EXAFS), and chemical analyses (gravimetric and ICP).  In these catalysts the connectivity of titanium to silica (the number of Ti-O-Si bonds) around teach Ti center is systematically changed in the range of two to four (2C- to 4C-Ti).  Furthermore, both the porosity and site density can also be controlled via a sequential dosing synthetic strategy.  Exposure of all of the 4C-Ti catalyst to aqueous peroxide forms a six-coordinate peroxy complex (DRUV, EXAFS models).  All of these catalysts are stable to multiple cycles of catalysis in the oxidation of trimethylphenol to the corresponding benzoquinone.  The 2C-titanium catalyst is more active than the 3C and 4C-Ti catalysts by a factor of three and five, respectively.  The synthesis, characterization and correlations between the composition and site structure of each of these nanostructured catalysts and their reactivity will be described.