The present invention concerns a method for enhancing the activity of vanadium
phosphorus oxide (VPO) catalysts. Promoter reagents are grafted onto or reacted
with the catalyst surface. An optional calcination and activation heating cycle
transforms the catalyst precursor into a final active phase. A preferred VPO catalyst
produced has a ratio of molybdenum to vanadium on the surface of the catalyst to
molybdenum to vanadium in the overall bulk of the catalyst represented by the equation
(Mo/V) Surface1.10 (Mo/V) overall bulk.
