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 va nadyl sulfate solution or by impregnation with aqueous vanadyl oxalate and characterized by powder X-ray diffraction, electron spin resonance spectros copy, and temperature-programmed reduction (TPR). Treatment of VAPO-5 with vanadyl ion results in incorporation of up to 1.0 wt% total vanadium into t he AFI framework by filling lattice vacancies. At vanadium contents above c a. 1 wt%, extraframework vanadium is also obtained. TPR results show that f ramework vanadium can be reduced by hydrogen at a lower temperature than ex traframework vanadium and vanadium in bulk V2O5. Oxydehydrogenation of prop ane over VAPO-5 samples reveals that framework vanadium is the most active and selective species for propylene formation (at 400 degrees C and 5% conv ersion, the selectivity is 72%); extraframework vanadium species are less a ctive and selective. (C) 2000 Academic Press.