Vanadyl(IV) phosphonates with the formula VOCnH2n+1PO3•xH2O (n = 0-4, x = 1 or 1.5) have been synthesized in organic medium by reaction of V2O5 with the corresponding phosphonic acid. The low-temperature magnetic susceptibility of vanadyl(IV) phosphite (n = 0) and n-butylphosphonate (n = 4) was indicative of antiferromagnetically exchangecoupled V2O9 vanadyl dimers similar to previously reported results for n = 1-3 phosphonates and vanadyl(IV) hydrogen phosphate hemihydrate (VOHPO4•0.5H2O). Raman spectroscopy of vanadyl(IV) phosphonates (n = 0-4) also suggested the similar local crystalline order in these solids. The close structural relationship between these phosphonates and VOHPO4•0.5H2O is further substantiated by the thermal transformation of the former phases in the presence of oxygen into vanadyl(IV) pyrophosphate. Kinetic measurements of the n-butane selective oxidation to maleic anhydride demonstrated that vanadyl methylphosphonate (n = 1) and phoshite (n = 0) produced vanadyl pyrophosphate catalysts with comparable (the methylphosphonate) and even superior performance (vanadyl phosphite) compared to the conventional unpromoted vanadium - phosphorus - oxide (VPO) catalyst.
All Science Journal Classification (ASJC) codes
- Chemical Engineering(all)
- Materials Chemistry