Vibrational spectroscopy propenes

The various spectroscopic techniques had revealed that Ti4+ ions in TS-1, Ti-beta and, Ti-MCM-41 are 4-coordinate in the dehydrated state. Tetrapodal Ti(OSi)4 and tripodal Ti(OH)(OSi)3 are the main Ti species. Upon exposure to H20, NH3, H202, or TBHP, they increase their coordination number to 5 or 6. On samples in which the Ti4+ has been grafted onto the silica (referred to as Ti f MCM-41), a dipodal Ti species (Ti(OH)2(OSi)2) may also be present. As a result of interaction with the oxidant ROOH (R = H, alkyl), the formation of 7)1- and p2-peroxo (Ti-O-O-), hydroperoxo (Ti-OOH), and superoxo (Ti02 ) species has been observed experimentally (Section III). A linear correlation between the concentration of the p2-hydroperoxo species and the catalytic activity for propene epoxidation has also been noted from vibration spectroscopy (133). 

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