Features of Raman band shifts of MoO3 catalyst exchanged with 18O tracer and active sites for reoxidation

Abstract The oxide oxygens of MoO 3 catalyst were exchanged with 18 O tracer by a reduction-oxidation method and by a catalytic oxidation of but-1-ene using 18 O 2 . The Raman band shifts of the MoO 3 exchanged with 18 O by the methods were examined. The two bands at 823 and 670 cm −1 of MoO 3 were shifted to lower frequencies preferentially, while the band of terminal MoO oxygen at 998 cm −1 were not shifted very much initially. Applying the correlation between the Raman bands and the stretching modes as described in the literature, the positions of oxide ions and 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 A distances of Mo octahedra exhibited rapid diffusions. These anion vacancies also seem to be active sites for oxygen insertion.