Hydrodesulfurization activity over supported sulfided ruthenium catalysts. Influence of the support

This work is aimed at optimizing Ru based catalysts for the hydrodesulfurization (HDS) of dibenzothiophene (DBT) by the modification of Ru loading as well as the selection of suitable support. Zirconium doped mesoporous silica (ZrMCM-41) was used as a support of Ru catalysts with different Ru loadings (1, 3, 7 and 11 wt%). The metal loading was incorporated by using the incipient wetness method, employing an aqueous solution of ruthenium(III) chloride. The catalysts were sulfided with a N2/H2S mixture (90/10%) at 400 °C for 2 h, and finally tested in the HDS reaction of DBT at a total pressure of 3.0 MPa. An increase in activity was observed when the Ru loading was increased up 7 wt%, whereas further addition of ruthenium produced a slight decrease. Once the optimum ruthenium loading (7 wt%) was established, the influence of the support on the catalytic performance was studied. For this comparative study, two different materials were used as supports of the Ru catalysts with the same metal content (7 wt%). These materials were a mesoporous silica (MCM-41) and a commercial γ-Al2O3. The catalyst supported on ZrMCM-41 displayed higher activity than catalysts supported on MCM-41 and Al2O3, suggesting that activity is favoured not only by the suitable textural and acidic properties of the support, but also the zirconium interaction with the ruthenium sulfide. Zirconium could act by stabilizing the Ru–S bond, an increasing its activity, thus impeding the reduction of ruthenium under the experimental conditions of the HDS reaction. This study concludes that the 7Ru–ZrMCM-41 catalyst, operating at 300 °C, with WHSV = 28 h−1 and H2 = 100 ml min−1 has the best activity, giving rise to a conversion of DBT of 84%.