Vanadium-51 NMR characterization of V-contaminated aluminas and aluminosilicate gels

P. S. Iyer, H. Eckert, M. L. Occelli and J. M. Stencel

Abstract

Solid state (wideline and magic angle spinning (MAS)) V-51 NMR has been used to study the speciation of typical components (the gel, clay, and zeolite) of a fluid cracking catalyst (FCC) resulting from systematic variation in vanadium loading. Formation of V2O5 is seen at high vanadium concentrations and is observed to be dependent on the vanadium precursor and/or the conditions used in its preparation. In addition, at least three other species with different bonding environments can be distinguished based on differences in chemical shift and relaxation times. The relative proportions of these are observed to change as a function of vanadium concentration. The corresponding spectra are not only sensitive to the NMR experimental conditions but also to the presence of water coordination. Structural inferences are discussed in context with V-51 NMR studies of model compounds and previous laser Raman, ESR and X-ray investigations of these materials.