On the role of niobium in nanostructured Mo/Nb-MCM-41 and NiMo/Nb-MCM-41 catalysts for hydrodesulfurization of dibenzothiophene

In the present work, Mo and NiMo catalysts were supported on the MCM-41 material modified with Nb2O5 and compared to similar catalysts supported on unmodified MCM-41 silica. Catalysts were characterized by different techniques and tested in the hydrodesulfurization of dibenzothiophene. Our interest was in clarifying the role of niobium in the above catalysts. It was observed that the Mo/Nb-MCM-41 and NiMo/Nb-MCM-41 catalysts were more active than their analogs supported on the MCM-41 material without niobia, and also they had higher hydrogenation ability. Based on the results of the characterization of calcined (oxide) and sulfided catalysts, it is proposed that niobium acts in the above catalysts as a support improving the dispersion of the MoS2 phase and increasing the amount of active sites and as a promoter, increasing the acidity of the Mo and NiMo catalysts. Although the promotion effect of niobium was not as strong as that of the nickel promoter. Also, the possibility of decoration of the edge surface of the Ni-Mo-S active sites with some Nb atoms cannot be excluded.