Abstract
Vanadium was incorporated in the TUD-1 mesoporous matrix with 5 wt-% loading (V-TUD-1), either with or without addition of 5 wt-% Ti (V-Ti-TUD-1) or 5 wt-% Zr (V-Zr-TUD-1), respectively. As identified by XRD, N-2 ad/desorption, TPR and Raman spectroscopic analyses, at this relatively high loading of vanadia, an unprecedented dispersion in conclusively isolated vanadia sites on the silica matrix was obtained in the V-TUD-1 and V-Ti-TUD-1 catalysts, whereas a relatively ill-defined material was obtained in the case of V-Zr-TUD-1. Consequently, the V-TUD-1 and V-Ti-TUD-1 catalysts showed high activity and selectivity in propane ODH. Titania in the silica matrix was found to interact with the isolated vanadia centers, improving the selectivity at comparable conversion levels, while reducing the apparent reaction rate. On the other hand, Zr negatively affected the performance of V-TUD-1, due to i) the formation of V2O5 and or V2O5/ZrO2 crystals, and ii) an ill defined pore structure of the TUD-1 matrix.