Nanosized-bulk V-containing mixed-oxide catalysts: a strategy for the improvement of the catalytic materials properties
A series of nanosized-bulk-supported Mo–V–Nb–Te catalysts was prepared. Using a new synthesis approach, nanocrystalline aggregates of the active phase were deposited on a support. This resulted in the formation of active and selective catalysts for propane oxidation in the acrylic acid reaction, which required a low amount of the active phase. In addition, the catalysts exhibit better mechanical properties and are more economical than their bulk counterparts. The presence of the nanocrystalline domains of the Mo–V–Te–Nb–O active phases (M1, M2 and rutile) for the supported-bulk catalyst was confirmed by HR-TEM, Raman spectroscopy and SAED. These nanoscaled materials presented excellent activity during the oxidation of propane into acrylic acid similar to those delivered by conventional bulk phase based catalysts. These values were much higher for the supported nanoscaled active phase after normalization to per gram of MoVNbTe oxide. When the active phase was stabilized in the nanoscale, it maximized the exposed fraction of active sites. In addition to their economic advantage compared to their bulk counterparts, the stabilization and higher exposure of the active phase and the alumina support endowed better mechanical resistance and an easier control to conform the catalyst pellets. In terms of the acrylic acid produced per amount of active phase required for catalyst production, the catalytic results indicated that the best catalytic performances were obtained for the supported-samples, indicating that this is a very promising route/concept for the preparation of catalytic materials.