Catalytic properties of nitrided V/Al/O-mixed oxides in the ammoxidation of propane and new efficient preparation method for the catalysts

Synthesis of Vanadium Oxide Nanofibers with Variable Crystallinity and V5+/V4+ Ratios

Tailoring the morphological, chemical, and physical properties of vanadium oxides (VOx) is crucial to optimize their performance in current and future applications. The present contribution proposes a new route to obtain VOx nanofibers with different V⁴⁺/V⁵⁺ ratios and crystallinity. The method involves the exclusive electrospinning of water-free NH₄VO₃-saturated solutions including a reductant. Subsequent air-annealing under suitable conditions yields vanadium oxide fibers of 20-90 nm diameter and 10-50 m²/g surface area. The presence of the reductant gives rise to VOx nanofibers with a considerable proportion of V⁴⁺. Then, the right choice of the calcination heating rate and temperature permits to modify the V⁴⁺/V⁵⁺ ratio as well as the crystalline phase and crystallite size of the fibers. With the proposed methodology, long-range continuous single-phase orthorhombic V₂O₅ and monoclinic V₃O₇ nanofibers are obtained.