RuS2-modified NiW/Al2O3 catalysts for refractory 4,6-dimethyl-dibenzothiophene hydrodesulfurization

Al2O3-supported noble metal (NM)-modified hydrodesulfurization (HDS) catalysts (W 15.8 wt% and Ni 3.5 wt%) were applied in refractory 4.6-dimethyl-dibenzothiophene elimination. Corresponding Ru-doped (0.5 and 0.7 wt%) materials were either dried (120 °C) or dried followed by calcining (400 °C) after NM deposition prior to activation (400 °C, 15/85H2S/H2 mixture). In solid at 0.5 wt% NM calcined after Ru deposition ruthenium was less dispersed (XRD and TPR) than over corresponding just dried one. Also, WS2 had higher dispersion (HR-TEM) on the latter. However, “NiWS” phase was enhanced (XPS) on the former material. NM-doped catalysts annealed before activation showed significantly enhanced activity (x2.4 and x1.6, solids with 0.5 and 0.7 wt% Ru, respectively) in refractory dibenzothiophene (DBT) HDS, as to that of pristine NiW/Al2O3. Enhanced hydrogenating properties of the former materials improved S elimination from sterically-hindered DBT. Conversely, Ru-doping was detrimental on NiW/alumina when non-annealed prior to activation. Unreduced Run+ and decreased pyrite-like RuS2 species (XPS) on those catalysts could be related to their strongly diminished HDS activity.