Relationship between structural/surface characteristics and reactivity in n-butane oxidation to maleic anhydride - The role of V3+ species

V/P/O-based catalysts were prepared by thermal treatments of VOHPO(4)0.5H(2 )O precursors prepared with the organic procedure. Different methods for pr ecursor dehydration led to compounds which were characterized by the prevai ling presence of crystalline (VO)(2)P2O7, but which also contained either V 5+ species or V3+ species. The catalytic performance of these compounds in n-butane oxidation under almost-equilibrated conditions was compared. It wa s found that the presence of either V3+ or V5+ enhances the specific activi ty in n-butane oxidation, while the selectivity to maleic anhydride at low n-butane conversion (30%) remains substantially unaffected. A fully equilib rated, well-crystallized (VO)(2)P2O7 was reduced with H-2. The reduced comp ound was more active than the fully equilibrated vanadyl pyrophosphate, whi le exhibiting comparable selectivity to maleic anhydride. (C) 2000 Elsevier Science B.V. All rights reserved.