FEATURES OF RAMAN BAND SHIFTS OF MOO3 CATALYST EXCHANGED WITH O-18 TRACER AND ACTIVE-SITES FOR REOXIDATION

The oxide oxygens of MoO3 catalyst were exchanged with O-18 tracer by a reduction-oxidation method and by a catalytic oxidation of but-1-ene using O-18(2). The Raman band shifts of the MoO3 exchanged with O-18 by the methods were examined. The two bands at 823 and 670 cm(-1) of M oO3 were shifted to lower frequencies preferentially, while the band o f terminal Mo=O oxygen at 998 cm(-1) were not shifted very much initia lly. Applying the correlation between the Raman bands and the stretchi ng modes as described in the literature, the positions of oxide ions a nd the anion vacancies for reoxidation were estimated. The oxide ions and anion vacancies corresponding to the Mo-O species which have 1.73 and 1.94 Angstrom distances of Mo octahedra exhibited rapid diffusions . These anion vacancies also seem to be active sites for oxygen insert ion.