Abstract
A new fluidizable VOx/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 VOx/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 80.5kJ/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 VOx 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 VOx reducibility and ethylene selectivity.
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