Investigation of Phosphorus Loaded V₂O₅/ZrO₂ Catalysts for the Oxidative Dehydrogenation of Propane (ODH)

In this study, V₂O₅/ZrO₂ samples loaded with different wt% of V₂O₅, ranging between 0% and 20% (wt% = 2.5, 3.6, 7.5, 10, and 20), were prepared and studied in the dehydrogenation of 2-butanol in order to investigate their acid-basic properties and to select the most interesting sample, that was identified in the 3.6 wt%V₂O₅/ZrO₂. Such a catalyst was modified by adding phosphate at different atomic ratios (P/V = 0.5, 1, and 2) and further characterized by XRD, SEM-EDX, ESR, UV-Vis-PIR diffuse reflectance. Tests of catalytic dehydrogenation of 2-butanol were also performed. Then, the so-prepared samples were investigated in the oxidative dehydrogenation (ODH) of propane that represents the reaction of main interest in this study. It has been shown that the introduction of 3.6 wt%V₂O₅ and phosphate in the zirconia matrix enhances the stability of the tetragonal structure, improves acidity, and promotes ODH activity. Compared to the unpromoted 3.6 wt%V₂O₅/ZrO₂ catalyst, the addition of phosphate increases the overall propane conversion from 12% to 20%, and also the propylene selectivity from 54% to near 64%, in the experimental conditions F °_C3H8/F°_O2/F°_total (cm³/min): 3.6/1.8/60 at the temperature of 500 °C. The influence of the reaction mixture on the ODH, in particular the oxygen flow rate, was addressed. Highlights: Phosphorus loaded V₂O₅/ZrO₂ catalysts were prepared and investigated in the oxidative dehydrogenation of propane. Addition of V₂O₅ and phosphorus to ZrO₂ stabilized the tetragonal phase with respect to the monoclinic one. Among the prepared V₂O₅/ZrO₂ samples, the most active catalyst corresponds to 3.6 wt% of V₂O₅/ ZrO₂, The addition of phosphorus to 3.6 wt% V₂O₅/ZrO₂ improves acidity and selectivity to propylene. Correlation between catalysts acidity and oxidative dehydrogenation of propane was observed.