Oxidative dehydrogenation of propane to propylene over VO_X/CaO-γ-Al₂O₃ using lattice oxygen

Oxidative dehydrogenation (ODH) of propane to propylene is studied using a new vanadium catalyst supported on CaO-γ-Al₂O₃ under a gas phase oxygen free atmosphere. The catalysts are synthesized with different CaO/γ-Al₂O₃ ratios, keeping the vanadium loading at 10 percent. The prepared catalysts are characterized using various physicochemical techniques. Raman spectroscopy reveals that the catalysts have monovanadate and polyvanadate surface species (VO_x) with minute crystal particles of V₂O₅. FTIR spectroscopy and XRD analysis confirm the presence of V₂O₅, CaO and γ-Al₂O₃ in the catalyst. The catalysts show stable reduction and re-oxidation behavior in repeated TPR and TPO cycles, respectively. NH₃-TPD shows that catalyst acidity decreases with increasing CaO content. The NH₃-TPD kinetics analysis reveals that the activation energy of desorption increases with higher CaO, indicating stronger active site-support interactions. The ODH of propane experiments are conducted in a fluidized CREC Riser Simulator under gas phase oxygen free conditions. Among the studied catalysts, VO_x/CaO-γ-Al₂O₃ (1:1) displays the highest propane conversion (65%) and propylene selectivity (85%) and a low CO_x due to its excellent oxygen carrying capacity, balanced acidity and moderate active site-support interactions.