Oxydehydrogenation of Propane over Vanadyl Ion-Containing VAPO-5 and CoAPO-5

Vanadyl ion-containing VAPO-5 and CoAPO-5 are prepared by contact with a vanadyl sulfate solution or by impregnation with aqueous vanadyl oxalate and characterized by powder X-ray diffraction, electron spin resonance spectroscopy, and temperature-programmed reduction (TPR). Treatment of VAPO-5 with vanadyl ion results in incorporation of up to 1.0 wt% total vanadium into the AFI framework by filling lattice vacancies. At vanadium contents above ca. 1 wt%, extraframework vanadium is also obtained. TPR results show that framework vanadium can be reduced by hydrogen at a lower temperature than extraframework vanadium and vanadium in bulk V2O5. Oxydehydrogenation of propane over VAPO-5 samples reveals that framework vanadium is the most active and selective species for propylene formation (at 400°C and 5% conversion, the selectivity is 72%); extraframework vanadium species are less active and selective.