γ-Al2O3-Supported and Unsupported (Ni)MoS2 for the Hydrodenitrogenation of Quinoline in the Presence of Dibenzothiophene

Supported MoS2/gamma-Al2O3 and Ni-MoS2/gamma-Al2O3 as well as unsupported Ni-MoS2 were investigated in the hydrodenitrogenation (HDN) of quinoline in the presence of dibenzothiophene (DBT). The supported oxide catalyst precursors had a well-dispersed amorphous polymolybdate structure that led to the formation of a highly dispersed sulfide phase. In contrast, the unsupported catalyst precursor consisted of a mixture of nickel molybdate and ammonium nickel molybdate phases that formed stacked sulfide slabs after sulfidation. On all catalysts, the reaction pathway for the removal of N in quinoline HDN mainly followed the sequence quinoline -> 1,2,3,4-tetrahydroquinoline -> decahydroquinoline -> propylcyclohexylamine -> propylcyclohexene -> propylcyclohexane. The hydrodesulfurization of DBT proceeded mainly by direct desulfurization towards biphenyl. For both processes, the activity increased in the order MoS2/gamma-Al2O3< Ni-MoS2/unsupported< Ni-MoS2/gamma-Al2O3. The promotion of the MoS2 phase with Ni enhances the activity of the unsupported catalyst to a greater extent than the supported one. However, the multiply stacked unsupported Ni-MoS2 exhibited lower rates than Ni-MoS2/gamma-Al2O3 because of its lower dispersion.