(676e) Oxidative Dehydrogenation of Propane to Propylene over VOx/CaO-γAl2O3 Catalysts

Propylene is one of the important feed stocks for the chemical industry to produce different valuable products. There are three major commercial processes available for propylene production, including steam cracking, catalytic cracking (FCC) and catalytic dehydrogenation.Steam cracking process consumes a large amount of energy, which accounts for 70 % of the overall production cost. The coke formation during the cracking of heavy hydrocarbon molecules is another drawback of the catalytic cracking process. This causes severe process operational problems, especially fouling, which requires frequent plant shut-downs for cleaning. The catalytic dehydrogenation, also suffers from the problem of coke formation and high energy requirement as a result of the endothermic nature of the reaction.

In this regard the oxidative dehydrogenation (ODH) of propane to propylene is more attractive due to its low operational cost and minimal environmental impacts. The abundant availability of propane in natural gas and refinery off gases can make the propylene production by ODH propane even sustainable as compared to the conventional processes.The most important advantage is the exothermic nature of the reaction, which requires no additional energy to accelerate the reaction. In this study the ODH of propane to propylene is investigated with a new vanadium catalyst supported on CaO-γAl₂O₃ under gas phase oxygen free atmosphere. The catalysts are synthesized with different CaO/γAl₂O₃ ratios keeping vanadium loading at 10 percent. The prepared catalysts are characterized using various physicochemical techniques. Raman spectroscopy reveals that the catalyst have monovanadate and polyvanadate surface species of VO_x with minute crystal particles of V₂O₅. FTIR and XRD analysis confirm the presence of V₂O₅, CaO and Al₂O₃ in the catalyst. The catalysts shows stable reduction and re-oxidation behavior in repeated TPR and TPO cycles, respectively. NH₃-TPD shows that catalyst acidity decreases with increasing the CaO content. The NH₃-TPD kinetics analysis reveals that the activation energy of desorption increases with higher CaO, indicating higher active site-support interaction. The ODH of propane experiments are conducted in a fluidized CREC Riser Simulator under gas phase oxygen free conditions. Among the studied catalyst, VOx/CaO-ð?¾Al₂O₃ (1:1) displays highest propane conversion (65 %) and propylene selectivity (85%) and the low CO_x due to its excellent oxygen carrying capacity, balanced acidity and moderate active site-support interactions.