A fluidizable VO_x/γ-Al₂O₃-ZrO₂ catalyst for the ODH of ethane to ethylene operating in a gas phase oxygen free environment

A new fluidizable VO_x/γ-Al₂O₃-ZrO₂ catalyst for the oxidative dehydrogenation (ODH) of ethane to ethylene is investigated. This catalyst operates in an oxygen free environment. The prepared catalyst is characterized using various physicochemical techniques. Nitrogen adsorption/desorption isotherm analysis shows a significant extent of monolayer coverage suggesting high active sites dispersion. TPR/TPO results demonstrate that the VO_x/γ-Al₂O₃-ZrO₂ catalyst is very reactive and displays consistent hydrogen consumption during repeated reduction and oxidation cycles. NH₃-TPD analysis indicates that the support acidity decreases after catalyst modification with ZrO₂. The estimated energy of ammonia desorption is found to be 75.4, 77.8 and 80.5 kJ/g for the Al₂O₃/ZrO₂ ratio of 2:1, 1:1 and 1:2, respectively. This higher energy of desorption with ZrO₂ content, it is assigned to the increased ZrO₂-support interaction. XRD patterns display the presence of a VO_x crystal phase on the support surface. When evaluated in a fluidized CREC (Chemical Reactor Engineering Center) Riser Simulator, the ZrO₂ modified catalyst shows at 600 °C close to 90% ethylene selectivity while the unmodified catalyst gave 42% ethylene only. Furthermore, ethylene selectivity remained stable with catalyst time-on-stream. It is concluded that ZrO₂ enhances metal-support interaction, influencing favorably the VO_x reducibility and ethylene selectivity.