Bismuth-modified vanadyl pyrophosphate catalysts

A 1 bismuth-doped VPO catalyst was prepared by refluxing Bi(NO3)3 and VOPO4 ⋅ 2H2O in isobutanol. The incorporation of Bi into the VPO lattice lowered the overall V oxidation state from 4.24 to 4.08. It also lowered both the peak maximum temperature for the desorption of oxygen from the lattice from 1001K (undoped) to 964K with a shoulder at 912K and the peak maxima for H2 temperature-programed reduction from 863, 1011 and 1143K (undoped) to 798, 906 and 1151K. The total oxygen desorbed from the Bi-doped catalyst was only one-fourth that of the undoped catalyst, while the amount of oxygen removed by TPR was roughly the same for both catalysts. These results suggest that in anaerobic oxidation, the Bi-doped catalyst will have roughly the same activity as in undoped catalyst in C4 hydrocarbon oxidation but will have a higher selectivity to products such as olefins and maleic anhydride.