Activity and synergetic effects of Mo sulfide catalysts promoted by Pd, Rh, Pt and Ru in HDS of benzothiophene
Advancing the chemical engineering fundamentals
Catalysis (T2-13P)
Keywords: Noble metal sulfides, Hydrodesulfurization, Benzothiophene
New promoters of active phases for hydrotreating have been often searched among noble metals. Their addition to sulfided Mo/Al2O3 catalyst led to substantial improvement of activity in hydrodesulfurization of thiophene and hydrodenitrogenation of pyridine. The aim of this work was to study the activity of Pd, Rh, Pt and Ru promoted catalysts in hydrodesulfurization of benzothiophene (BT) and to evaluate the effect of the noble metals.
Mo sulfide catalysts were promoted by small amounts of Pd, Rh, Pt and Ru (< 0.8 wt.%) and characterized by ICP/AAS, N2 adsorption and some of them by TEM. Their activity in hydrodesulfurization of benzothiophene (BT) was compared with activities of the conventional Mo/Al2O3 and CoMo/Al2O3 catalysts. HDS of BT was performed in a flow fixed bed reactor (330-390°C, 16 bars). HDS activity of the catalysts sulfided at 400°C/1h (10 % H2S/H2) was expressed by first-order rate constants for overall BT disappearance (kBT) and ethylbenzene (EB) formation (kEB). The synergetic effects in BT removal and EB formation were expressed by the kBT (kEB) ratios the promoted and the unpromoted Mo/Al2O3 catalysts.
The addition of noble metals led to the improvement of activity with synergetic effects up to about 4. The Pd promoted sample was the most active from all the noble metals based catalysts studied, but less active in comparison to the CoMo system. This can be explained by lower Pd loading than that of Co. On the other hand, the specific synergetic effect calculated per atom of noble metals was higher than that of Co and decreased in the order Pt > Rh > Pd > Ru. The synergetic effects observed for Pd and Pt promoted catalysts were less temperature dependent than those for Rh, Ru and the CoMo system, suggesting a different quality of the active sites participating in hydrodesulfurization.
Presented Wednesday 19, 13:30 to 15:00, in session Catalysis (T2-13P).
