Catalytic performances and correlations with metal oxide band gaps of metal-tungsten mixed oxide catalysts in propane oxydehydrogenation

Tungsten-based catalysts of the form X wt.% Na2WO4/support (where X = 5, 10, 50 or 75 and the support is either gamma-Al2O3 or SiO2) were prepared by impregnation method and tested for oxidative dehydrogenation of propane. The effects of Na2WO4 loadings on catalyst performances were more pronounced on gamma-Al2O3 supported sample. Individual first-row transition metals (V, Cr, Mn, Co, Ni or Zn) were doped on NaWSi. CoWSi exhibited the best improvement, with conversion of 10.7% and selectivity to propylene of 52.9% at 450 degrees C. The metal oxide band gaps were correlated with catalyst performances. At a constant propane conversion, strong correlations were observed between the band gaps and respective CO and CO2 yields. This offers insight into relationship between the species conductivities and the products distributions.