OBSERVATION OF [AL(OH)N(H2O)6-N]N(MOO4) IN HYDROTREATING CATALYST PRECURSORS BY SOLID-STATE AL-27 NMR

A previously unobserved octahedral Al-27 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 the Al-27 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.