Nickel and cobalt promoted tungsten and molybdenum sulfide mesoporous catalysts for hydrodesulfurization

High-performance hydrodesulfurization (HDS) catalysts were prepared by incipient wetness impregnation of Ni–Mo(W) and Co–Mo(W) species over siliceous MCM-41 doped with zirconium. Catalysts with W and Mo loadings of 20 and 11 wt%, respectively, and with a Ni or Co loading of 5 wt%, were prepared. As a reference, a nickel–tungsten catalyst supported on a commercial γ-Al2O3 with a 5 and 20 wt% metal loadings, respectively has also been prepared. HDS reaction of dibenzothiophene (DBT) under 3.0 MPa of total pressure and with hourly space velocity (WHSV) of 28 h−1 was used to evaluate the activity of these sulfided catalysts. All the catalysts displayed a very good performance in the temperature range of 300–340 °C, with conversions between 49.0% and 92.6%. The Ni promoted catalysts displayed better performances than those of Co promoted catalysts in the HDS of DBT. On the other hand they show different selectivity to hydrogenation, thus, in Ni promoted catalysts, the hydrogenation (HYD) reaction contributes more to the conversion of DBT than Co promoted catalysts where the direct desulfurization (DDS) reaction is more important. The performance of this set of catalysts is similar to that observed with a Ni5W20–Al2O3 catalyst in the same range of temperature (300–340 °C). However, the selectivity to the HYD product, CHB, observed with nickel promoted catalysts (Ni5–Mo11 and Ni5–W20) is higher than that found for Ni5W20–Al2O3 catalyst probably due to a higher superficial area of the MCM-support and to the presence on the surface of zirconium species, which leading to a better dispersion and lower stacking of the active phases.