Promotion of Mo/Al2O3 sulfide catalyst by noble metals in simultaneous hydrodesulfurization of thiophene and hydrodenitrogenation of pyridine: a comparative study Original Research Article

Mo/Al2O3 catalyst was modified by small amounts (0.3–0.8 wt.%) of different noble metals (Rh, Ru, Pd and Pt). Their addition had positive effect on the rates of hydrodesulfurization (HDS) of thiophene and hydrodenitrogenation (HDN) of pyridine. Activity of the Mo/Al2O3 catalyst increased after addition of Rh by a factor 12 in HDS and after addition of Pt by a factor about 5 in HDN. The magnitude of the observed synergy was influenced by two factors. First, by the state of the Mo phase before deposition of a noble metal, whether oxidic or sulfided, and second, by the position of the noble metal in the periodic system. It was observed that all the catalysts prepared by deposition of noble metals on a presulfided Mo/Al2O3 matrix (S series) possessed substantially higher activities than those prepared from an oxidic Mo/Al2O3 catalyst (O series). The addition of metals of the second row, such as Rh, Ru and Pd, improved mainly HDS, while the metal of the third row (Pt) improved more HDN. The thiophene HDS activity of the Rh-Mo(S)/Al2O3 catalyst was the highest and substantially above the activities of conventional CoMo and NiMo/Al2O3 catalysts. The pyridine HDN activity of the Pt-Mo(S)/Al2O3 catalyst exceeded the activity of NiMo/Al2O3 catalyst.