High-dispersed Ni-Mo-S active phases within hierarchical pore materials by introducing the cationic protective shell during the impregnation process for hydrodesulfurization

A highly dispersed NiMo/Beta-FDU-12 catalyst was successfully synthesized by introducing the cationic protective shell (DTA(+), MTA(+) and CTA(+)) in the impregnation process in order to achieving the optimal interaction between Mo species and the support. Based on H-2-TPR, XRD, XPS and HRTEM characterization results, it could be proved that quaternary ammonium cationic salts served as effective shells to protect Mo species from aggregation in the hydrothermal treatment, thus decreasing the interaction between Mo species and support and improving the dispersion of Ni-Mo-S active phases. Compared with NiMo/BF-DTAB and NiMo/BF-MTAB catalysts, NiMo/BF-CTAB catalyst synthesized with longer alkyl-chain quaternary ammonium cationic species exhibited the best hydrodesulfurization performance of DBT, of which the conversion reached 98% at 10 h(-1) WHSV. Moreover, NiMo/BF-CTAB catalyst showed higher HYD/DDS ratio, which is nearly three times than that of NiMo/BF-IWI catalyst obtained through the traditional impregnation method. The high hydrodesulfurization activity of NiMo/BF-CTAB catalyst came down to the comprehensive effects of the best dispersion of active phases (f(Mo) = 0.32), the highest sulfidation degrees of active metals (S-Mo = 60.19%) and higher amounts of total acids.