Abstract
Industrial vanadium phosphate (VPO) samples (vanadyl phosphate hemihydrate precursor compound, freshly calcined and equilibrated vanadyl pyrophosphate solids) shaped with polysilicic acid (PSA) were characterized and used as catalysts for the ammoxidation of 3-picoline to nicotinonitrile. Catalyst characterization with N 2-adsorption, XRD, IR spectroscopy, UV–Vis-DRS and XPS provide information on BET surface area and pore size, crystalline properties and vanadium oxidation state data in bulk and near-to-surface region. BET surface area is dramatically increased by calcination of the precursor but catalytic operation drops the surface area again, moreover, deactivation by carbon deposits was observed. The deactivation is also demonstrated by decrease in V 5+ portion in the equilibrated catalyst. Ammoxidation test runs showed quite good performance for the calcined vanadyl pyrophosphate sample; the used and precursor sample revealed poor performance only. Interestingly, characterization of samples used in ammoxidation showed phase alteration in particular for precursor sample proving phase change towards NH 4-ion containing VPO phase.
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