Characterization of Mo/Al2O3 sol-gel catalyst by Al-27 nuclear magnetic resonance spectroscopy

The Mo/Al2O3 catalysts at various molybdenum loading was prepared by adding (CH3COCH=C(O-)CH3)(2)MoO2 (Mo-acac), dissolved in ethanol, to the boehmite alumina sol driven from aluminum isopropoxide (AIP). The structural evolution of Mo/Al2O3 gel was investigated by using Al-27 nuclear magnetic resonance (NMR) spectroscopy and X-ray diffractometry (XRD). Al-27 NMR of Mo/Al2O3 has been compared with that of pure alumina. The addition of molybdenum species to alumina sol was to have no effect on the alumina structure when the molybdenum loading was lower than 20%. No incorporation of molybdenum species to alumina lattice was observed and the finely dispersed MoS2 crystallite on the support was obtained upon sulfidation. However, an Al-2(MoO4)(3) phase, which was an indication of the interaction between Al2O3 and MoO3, was formed on the alumina surface when molybdenum loading was higher than 20%. All molybdenum species were accessible by reactant molecules regardless of molybdenum loading.