Novel vanadium phosphate phases as catalysts for selective oxidation

Abstract

In our effort to induce novel modifications in the structure of some important vanadium phosphate phases used as selective oxidation catalysts, it has been observed that metal ions such as Zn²⁺, Ni²⁺, Pd²⁺can be incorporated into the vanadyl hydrogen phosphate VOHPO₄0.5H₂O phase in very different ways depending upon the medium of preparation. It has been found that the metal ions are either substituted into the lattice with retention of structure of the parent compound or intercalated between the layers of a new mixed-valent phase. These new metal-incorporated phases are catalytically active and the palladium incorporated compound in particular displays shape selective catalysis for different oxidation and reduction reactions. In another approach, the preparation of VOHPO₄0.5H₂O) has been modified to give a novel crystalline phase containing mixed-valentvanadium and having NH₃ species bound to the lattice. This phase could be a potential catalyst for ammoxidation reactions. In addition, novel mesostructured vanadium phosphate phases have been prepared using a long-chain amine as the templating agent involving a ligand templating mechanism of formation.