A hydrophobic gel for epoxidation of olefins with organic peroxides

The epoxidation of cyclooctene by tert-butyl hydroperoxide (t-BuOOH) over a TiO2-SiO2 xerogel made from a permethylated cyclooligosiloxane, tetraethylorthosilicate, and a Ti chloroalkoxide, was carried out in acetonitrile as the reaction solvent. The organic moieties of the hybrid gel (in this case, -CH3 groups) and the Ti content of the catalyst appear to be stable on prolonged exposure to the reaction medium. Besides very good stability, the hybrid catalyst in this study displays 100% selectivity toward cyclooctene epoxide production. Solid state Si-29 magic angle spinning NMR (Si-29 MASNMR), diffuse reflectance Fourier transform infrared spectroscopy (DRIFTS), and chemical analysis were used to monitor the stability of the hybrid material. The kinetics of olefin epoxidation was studied in a batch reactor in the 313-343 K range.