On the umbrella model for supported vanadium oxide catalysts

An earlier-proposed model for the molecular structure of VO4 species on alumina was tested and compared with the pyramid model on a silica support. The model can be described as a chemisorbed O-support-V=O(O-2) species with a similar geometry as on alumina. Results of DFT calculations on this model are consistent with the experimental Raman and EXAFS data collected on low-loaded silica-supported vanadium oxide catalysts. The band observed at 915 cm(-1) is assigned to an O-O stretch vibration. The thermal motion of the bound O-2 molecule can explain the broadness of this band. These findings. in combination with our previous work. demonstrate that the umbrella model is a viable, internally consistent model for supported vanadium oxide catalysts at least at low loadings. (c) 2006 Elsevier Inc. All rights reserved.