Vanadium-containing catalysts for oxidation reactions
Two sets of catalysts (VOx-SiO2 and VOx-Al2O3) were prepared by flame pyrolysis (FP) and tested for the oxidative dehydrogenation (ODH) of propane. Better vanadium dispersion and superior catalytic performances (in terms of propene selectivity) were achieved with FP-samples compared to catalysts obtained by impregnation. Similarly, two V-containing mesoporous catalysts (V-SBA-15 and V-MCF) were directly synthesized to obtain highly dispersed V species in the silica. The latter catalysts performed better in both ODH of propane and dichloromethane decomposition compared to impregnated ones. In addition, better results in the ODH of propane were obtained with V-MCF, while higher activity in dichloromethane decomposition was achieved with V-SBA-15. These findings seem to be related to the different porous network of the two catalysts.
Over the last few decades, vanadium-based catalysts have attracted growing interest because of their high potential in many oxidation processes, such as sulfuric acid production, oxidation of o-xylene to phthalic anhydride, ammoxidation of alkyl aromatics to aromatic nitriles and selective reduction of NOx with ammonia (1). Other oxidations may also occur with these catalytic materials, including Cl-VOCs decomposition (2), methanol oxidation, carbon monoxide oxidation and the partial oxidation of hydrocarbons (3). Furthermore, vanadium oxides (VOx) are catalytically active in the oxidative dehydrogenation (ODH) of propane (4) a promising alternative route to propene, since the overall reaction pathway is exothermic and the thermodynamic constraints of non-oxidative pathways are avoided (5, 6). The need for propene is expected to grow in the near future, leading to the necessity of new industrial processes. Most V-based catalysts consist of VOx deposited on oxide supports, such as SiO2, Al2O3, TiO2 and so on. Clearly, the support itself plays a key role during catalytic reactio ...