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Publisher Summary This chapter focuses on the optimization of the hydrolytic sol–gel preparation method achieving the highest possible control of the molecular scale interdispersion of the mixed-oxide phases. More particularly, the effects of various promoters and higher Nb/V ratio on the hydrolytic sol–gel preparation are investigated. The possible relationship between the nature and interdispersion of the oxide phases present in the Nb–V systems, and the resulting catalytic performances in the oxidative dehydrogenation (ODH) of propane are presented. The sol–gel preparation of the 1:1 Nb/V systems led to the formation of gelatinous precipitates with the only exception of the sample obtained by adding citric acid as promoter, which turned into a gel. The sol–gel preparation of 4.5:1 and 9:1 Nb/V systems led in both cases to the formation of yellow coloured gels. From these preliminary results, it was concluded that a high Nb amount or the presence of a V complexing agent such as citric acid are necessary conditions for preparing Nb/V mixed gels, otherwise the solution of Nb and V precursors is not stable upon water addition, and a yellow gelatinous precipitate readily forms, independently of the water amount and/or the precursors concentration adopted. |
