Effect of Activation Duration in 1% Oxygen in Nitrogen Balance on Vanadium Phosphate Catalysts Synthesized via Sesquihydrate Route

Abstract

Four vanadium phosphate catalysts were synthesized via vanadyl hydrogen phosphate sesquihydrate (VOHPO4•1.5H2O) route and activated at different duration (6, 18, 30 and 75 hours) in 1% oxygen/ nitrogen (1% O2/N2) mixture at 733K. The increased activation duration led to a decreased in the specific surface area of the catalysts. The increased activation duration increased the average oxidation state of vanadium. The surface morphologies of the catalysts exhibited plate-like crystals that agglomerated into clusters with folded edges. Temperature-programmed reduction (TPR) showed that increasing activation duration led to an increased in total amount of oxygen removed from the catalysts. Temperature-programmed desorption (TPD) showed that the total amount of oxygen desorbed from the catalysts increased as the activation duration increased. Catalytic performance revealed that all the catalysts produced possessed rather low in terms of activity but high in terms of selectivity.