The effect of sol-gel promoters on the characteristics of mixed V-Nb oxides and their catalytic properties in propane oxidative dehydrogenation

The hydrolytic preparation of systems with higher amount of Nb, 9:1 Nb/V and 4.5:1 Nb/V, does not require the addition of a complexing agent like citric acid. Sols containing higher amounts of Nb precursor are stable and turn rapidly into gels. In both 9:1 Nb/V and 4.5:1 Nb/V samples, there is no evidence of crystalline phases containing vanadium. Only the presence of crystalline Nb2O5 is detected by XRD. The effects of sol-gel additives and niobium amount on the morphological and catalytic properties are investigated. The 4.5:1 Nb/V sample shows both higher activity and selectivity to propene than the 1:1 Nb/V samples. The 9:1 Nb/V sample is found to behave similarly to pure Nb2O5, showing rather poor activity and higher selectivities to propene at increasing propane conversion.