The hydration and transformation of vanadyl pyrophosphate

The reaction of vanadyl pyrophosphate, (VO)2P2O7, with water was carried out at various temperatures and pressures in an autoclave and the resulting hydration products characterized using elemental analysis, powder X-ray diffraction, laser Raman spectroscopy and infrared spectroscopy. The hydration products were strongly dependent on the reaction conditions. At 150 °C (VO)3(PO4)2•6H2O was formed; at 200 °C VOHPO4•0.5H2O, and at 250 °C a phosphorus deficient, vanadium(III) phosphate (V1.23(PO4)(OH)0.69(H2O)0.31•0.33H2O or V5.12(PO4)4(OH)3.36(H2O)0.64•0.84H2O) was found to be the main product. The addition of 1-propanol to the reaction promotes the transformation of (VO)2P2O7 to the phosphorus deficient, vanadium(III) phosphate and the transformation to this phase is described in terms of the formation of extended glide shear defects due to the loss of lattice oxygen as well as the removal of phosphorus species from the catalyst lattice