Identification of vanadium species involved in sequential redox operation of VPO catalysts

A vanadyl pyrophosphate (VPO) catalyst was investigated for its sequential reduction and oxidation ability for butane oxidation, using a novel oscilla ting microbalance reactor. Correlation of the redox kinetics with the ident ities of the vanadium species obtained by potentiometric titration methods suggests that only the near-surface oxygen is readily available for the oxi dation of butane; effective redox cycles can only occur between V5+ and V4; accumulation of V3+ species represents one mode of catalyst deactivation. (C) 2000 Elsevier Science B.V. All rights reserved.