Characteristic features of Raman band shifts of vanadium oxide catalysts exchanged with the [formula omitted] tracer and active sites for reoxidation

Abstract

The oxide oxygen ions of V 2O 5 catalyst were exchanged with 18 O tracer by a reduction–oxidation method and by a catalytic oxidation of n-butane using 18 O 2. The Raman band shifts of the V 2O 5 exchanged with 18 O by the methods were examined. The band at 700 cm −1 was shifted to lower frequencies more preferentially than the band of VO oxygen at 998 cm −1. Applying the correlation between the Raman bands and stretching modes as described in the literature, the positions of oxide ions and anion vacancies for reduction and reoxidation were estimated. The anion vacancies corresponding to the V–O species in the V square with 1.88 and 2.02 Å distances seem to be active sites for oxygen insertion. The similar conclusions were obtained for Mo containing V 2O 5 catalyst.