CHARACTERIZATION OF V2O5 TIO2 CATALYSTS BY SOLID-STATE NMR OF V-51/

The catalysts V2O5 (8%)/TiO2 (EL10V8) and V2O5 (1%)/TiO2 (EL10V1) have been studied by solid state V-51 NMR spectroscopy using both wide-lin e (static samples) and MAS conditions (magic angle spinning samples). The experimental results, obtained using three different spectrometers and three experimental methods, are discussed and analysed. It is dem onstrated that the quadrupolar echo method allows a better detection o f the vanadium nuclei than the single pulse method if only a wide-line signal analysis is desired. It is also shown that the MAS method can detect small changes in the chemical shift of different species; howev er, in this case, very high spinning frequencies are necessary in orde r to separate the peaks from their spinning sidebands. In both samples , all experiments reveal that the majority of the surface vanadium ato ms are in a distorted octahedral environment similar to that of the va nadium in V2O5. Moreover, the use of high speed magic angle spinning s hows that a small quantity of another vanadium species is present on E L10V8 with a structure also nearly similar to V2O5.