In-situ 31P MAS NMR probing of the active centers in Ti silicalite molecular sieve

The investigation of the active centers in titanium zeolite was conducted by a probe reaction, the oxidation of trimethylphosphine. The different sites of TS-1 zeolite can be clearly distinguished through P-31 solid-state MAS NMR spectra of adsorbed trimethylphosphine. The results showed that only the trimethylphosphine bound to the coordinate-unsaturated framework Ti sites and the distorted tetrahedral Ti sites ofTS-1 zeolite could be easily oxidized by urea hydrogen peroxide. Diffuse Reflectance UV-Vis and Si-29 MAS NMR spectra further confirmed that the titanium peroxide species (TiOOH), which is formed through the solid-solid interaction between urea-H2O2 and TS-1 zeolite, could be catalytic active centers during the oxidation of trimethylphosphine. (C) 2015 Elsevier B.V. All rights reserved.