| Abstract
| - Theoretical calculation using density functional B3LYP correlation-exchange is employed to study the structureof different sizes of the VAPO-5 clusters. The results indicate that the substitution of either the phosphorussite or the aluminum site of the aluminophosphate-5 framework with vanadium is generally not feasible. Thecalculated structures are comparable with those from the in-situ X-ray absorption (XANES and EXAFS) ofthe V K-edge. The isolated vanadium was found to exist as a mono-oxo (V4+ = O)(Of)4 species for reduced,dehydrated VAPO-5 and as a di-oxo V5+O4 species for calcined, dehydrated VAPO-5. The coordinationgeometry of the mono-oxo V4+ species is sensitive to the presence of water molecules, and the water moleculesmay exchange with the framework oxygens that are coordinated to the V4+ center.
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