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

H-1 MAS NMR, H-1 spin-echo MAS NMR with Al irradiation, Si-29 MAS NMR, and H-1 --> Si-29 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. (C) 2003 Elsevier Science (USA). All rights reserved.