Vanadyl ion-containing VAPO-5 and CoAPO-5 were prepared by contact with a vanadyl sulfate solution or by impregnation with aqueous vanadyl oxalate and characterized by powder XRD, ESR spectroscopy, and TPR. The resulting materials were evaluated as catalysts for propane oxidation. Framework vanadium can be reduced by hydrogen at a lower temperature than extraframework vanadium and vanadium in bulk V2O5. Oxyhydrogenation of propane over VAPO-5 samples showed that framework vanadium was the most active and selective species for propylene formation at 400°C, 5% conversion, and 72% selectivity. Extraframework Va species were less active and selective. Treatment of VAPO-5 with vanadyl sulfate solution enhanced the catalytic activity because vanadium is incorporated into the VAPO-5 framework during ion treatment. Va levels > 1 wt %, achieved by impregnation, resulted in the formation of extraframework vanadium.
ASJC Scopus subject areas
- Physical and Theoretical Chemistry