Abstract
A previously unobserved octahedral27Al MAS NMR resonance has been detected in rehydrated calcined Mo/Al2O3 hydrotreating catalyst precursors. This resonance is attributed to the presence of hydrated forms of aluminum molybdate such as [Al(OH) n (H2O)6-n ] n (MoO4) (n = 1 or 2). The cross-polarization relaxation parameters, obtained from variable contact time experiments, yielded information on the relative sizes of the [Al(OH) n (H2O)6-n ] n (MoO4) domains in the catalysts with different molybdenum loadings. Analysis of the27A1 MAS NMR spectra of P-Mo(8)/Al2O3 and P-Mo(12)/Al2O3 (wt%P = 0.0–12.0) shows that a function of the phosphate in the 12 wt% Mo catalyst is to prevent the re-hydration of the molybdate phases on the calcined catalysts.
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Edwards, J.C., Decanio, E.C. Observation of [Al(OH) n (H2O)6-n ] n (MoO4) in hydrotreating catalyst precursors by solid-state27 Al NMR. Catal Lett 19, 121–130 (1993). https://doi.org/10.1007/BF00771746
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DOI: https://doi.org/10.1007/BF00771746