Intrinsic thiophene hydrodesulfurization kinetics of a sulfided NiMo/SiO2 model catalyst : volcano-type behavior

A realistic planar model of a silica-supported NiMo sulfide hydrotreating catalyst (i.e., a planar SiO2 single crystal spincoated with active metal oxides) was used to study the intrinsic kinetics of thiophene hydrodesulfurization over a broad temp. range at atm. pressure. The specific nonporous nature of the model catalysts excludes possible diffusion limitations, which are commonly encountered in kinetic studies of their industrial porous analogs. Measurement of the intrinsic chem. kinetics over a broad temp. range under these conditions, a Volcano-type behavior was obsd. for thiophene hydrodesulfurization. An optimum activity was obsd. at 648-783 K. An obsd. temp. dependence on the hydrodesulfurization activity results in a neg. apparent activation energy for thiophene HDS at high temp., which, in turn, relates to the intrinsic kinetic phenomenon on the catalyst surface. The specific kinetic parameters were discussed in terms of possible mechanisms. [on SciFinder (R)]