Operando Raman-GC study of supported alumina Sb- and V-based catalysts:: Effect of Sb/V molar ratio and total Sb+V coverage in the structure of catalysts during propane ammoxidation

Raman spectroscopy during propane ammoxidation is used to study VSbO4-based catalysts and the changes that occur in the catalyst structure and at its surface during propane ammoxidation. It is shown how the active rutile VSbO4 phase forms during catalytic operation. The rutile phase forms upon the reaction-induced interaction between surface vanadium and antimony oxide species. The acquisition of Raman spectra simultaneously to the measurement of the catalytic performance permits assessing direct correlations between structural and performance characteristic changes. Operando Raman-GC spectra show the transformation of surface vanadium oxide, antimony oxide, and Sb-V oxide phases, show the effect of total Sb+V coverage and of the SbN atomic ratio for propane ammoxidation performance during catalytic operation, and underline the relevance of the interplay between the rutile VSbO4 phase and segregated Sb oxide species and surface V5+ sites for propane ammoxidation.