MAS NMR, TPR, and TEM studies of the interaction of NiMo with alumina and silica–alumina supports

1H MAS NMR, 1H spin-echo MAS NMR with Al irradiation, 29Si MAS NMR, and 1H→29Si CP MAS NMR were used to investigate the deposition of Mo and Ni species on the surface of alumina and silica–alumina. Mo and Ni species first occupy the alumina sites and then the silica sites. The results of temperature-programmed reduction show that the weaker interaction between the Mo and Ni species and the silica–alumina support leads to better reducibility of the metal oxides on silica–alumina than on Al2O3. Mo and Ni species also interact with each other. Transmission electron microscopy proved that, after sulfidation, higher stacks of MoS2 are formed on the silica–alumina support than on the Al2O3 support. The higher stacking is responsible for the higher hydrodenitrogenation activity of the NiMoS catalysts supported on silica–alumina.