An active and selective hydrocarbon partial oxidation catalyst comprises an activated
partially-reduced polyoxometallate, preferably niobium polyoxomolybdate, that is
prepared from a suitable polyoxoanion, which has been exchanged with a suitable
cation and activated by heating to an activation effective temperature in the presence
of a suitable reducing agent such as pyridinium. C3 and C4 hydrocarbons
may be partially oxidized selectively to acrylic acid and maleic acid.
