NiMo catalysts supported on graphene-modified mesoporous TiO₂ toward highly efficient hydrodesulfurization of dibenzothiophene

The graphene-covered mesoporous TiO₂ (S_BET > 90 m² g^-1) were successfully prepared by using graphene oxide (GO) as graphene source via one-step hydrothermal reduction, and then were prepared supported NiMo catalysts for hydrodesulfurization (HDS) of dibenzothiophene (DBT). The active species were incorporated by incipient impregnation. Compared with the unmodified NiMo/TiO₂ catalyst, all modified catalysts exhibited higher HDS activity under mild conditions of 280 °C, 2.0 MPa, liquid hourly space velocity of 4 h^-1 and hydrogen/feed ratio of 400 (V/V). Among of them, the catalyst with the appropriate mass ratio of rGO/TiO₂(0.5) showed the highest DBT conversion of 99.9%. The prepared catalysts were characterized by various techniques (N₂ adsorption-desorption, XRD, Raman, Pyridine FT-IR, NH₃-TPD, H₂-TPR, CO uptake, SEM and TEM). The enhanced HDS activity can be ascribed to (i) The incorporation of rGO (reduced graphene oxide) induces proper enhanced Lewis acidity of the modified catalysts, which promotes the adsorption of DBT molecules and facilitates the hydrogenation route. (ii) The introduction of rGO changes the HDS product (H₂S) desorption behaviors, accelerating H₂S desorption rate from catalyst surface and promoting the efficiency of catalyst immediately.