Reduction kinetics and catalytic activity of VOx/γ-Al2O3-ZrO2 for gas phase oxygen free ODH of ethane

Abstract

Oxidative dehydrogenation (ODH) of ethane is investigated using VOx/Al2O3-ZrO2 catalysts in absence of gas phase oxygen under circulating fluidized conditions. In this approach, the catalyst particles also serve as a source of lattice oxygen. The fluidizable VOx/Al2O3-ZrO2 catalysts are prepared with various amount of VOx using a successive impregnation technique. XRF measurement confirms the consistency between the targeted and actual metal loading. Nitrogen adsorption shows type-v monolayer adsorption on VOx/Al2O3-ZrO2 surface. XRD and Raman confirm the presence of VOx species on the Al2O3-ZrO2 as a crystal phase. NH3-TPD measurement shows that the acidity of the catalysts decreases slightly with VOx loading. The VOx/Al2O3-ZrO2 catalysts are stable over repeated reduction (TPR) and oxidation (TPO) cycles. The TPR kinetics modeling reveals that the activation energy of catalyst reduction (oxygen release) increases with increasing the VOx loading. This is an indication of increasing difficulties of VOx reduction at higher VOx loading. The ODH of ethane experiments are established in a fluidized CREC-riser simulator at different temperatures (525–600°C) and reaction times (20–50s). Approximately, 89% ethylene selectivity is achieved with 10% VOx on Al2O3-ZrO2. The ethylene selectivity also remains stable over repeated ODH and catalyst regeneration cycles.