Correlation of ⁵¹V NMR Parameters with Local Environment of Vanadium Sites

Abstract

Vanadium oxide based catalysts are widely used in industry. Generally, the activity of heterogeneous catalysts is determined by the structure of active centers. For characterization of active vanadium species by ⁵¹V NMR spectroscopy the knowledge of correlation between parameters of NMR spectra and local structure of vanadium sites is necessary. It may be found successfully for individual vanadium compounds with known structure. Earlier, the correlation between the anisotropy of the chemical shielding tensor and the local environment of vanadium sites was demonstrated [1, 2], but for the detailed characterization of these sites the knowledge of other ⁵¹V NMR parameters is also necessary. Recently, SATRAS — the numeric analysis of spinning side bands intensities in MAS NMR spectra, was proposed by Skibsted et al.[3] This analysis allows the determination of magnitudes and relative orientation of ⁵¹V chemical shielding (CS) and quadrupling coupling (QC) tensors. In earlier reports all eight parameters of ⁵¹V NMR spectra were presented with high accuracy for some orthovanadates and alkali metal metavanadates [5], as well as for series of divalent metal metavanadates [6] and pyrovanadates [7].