SOLID-STATE NUCLEAR-MAGNETIC-RESONANCE SPECTROSCOPIC INVESTIGATION OF HYDROTREATING CATALYSTS AND RELATED MATERIALS

The solid state nuclear magnetic resonance spectroscopy of Mo-95, P-31, and Al-27 nuclei were used to investigate surface species on hydrotreating catalysts (NiPMo, PMo, and Mo) supported on gamma-alumina as a function of calcination temperature and hydration. The catalysts exhibited a reversible structural change brought about by hydration and calcination up to ca. 550-degrees-C which corresponds to calcination temperatures for industrial catalysts. On the other hand, the catalysts calcined at 700-degrees-C and higher temperatures result in the irreversible formation of a AlPO4 phase and a reversible Al2(MoO4)3 phase with respect to hydration and calcination. The AlPO4 and Al2(MOO,)3 phases were unreactive with respect to a subsequent sulfiding process. Following calcination of the catalyst supported on silica, it was observed by Mo-95 nuclear magnetic resonance spectroscopy, to have higher dispersion and weaker interaction with the support with regard to hydration compared to alumina supported catalysts.