Deep Hydrodesulfurization of Dibenzothiophenes Over NiW Sulfide Catalysts Supported on Sol-Gel Titania-Alumina

This work showed that the use of Al2O3-TiO2 as carriers has a positive effect on the activity of supported NiW catalysts in the hydrodesulfurization of dibenzothiophene and 4,6-dimethyldibenzothiophene carried out in a batch reactor at 320 degrees C and total H-2 pressure of 5.5 MPa. Two Al2O3-TiO2 mixed oxides with Al/Ti atomic ratios of 10 and 2 were synthesized by sol-gel method together with the pure Al2O3 synthesized as reference support. For NiW/Al2O3-TiO2 and NiW/Al2O3 catalysts, a metal load of 17 and 5.5 wt% of W and Ni were considered respectively. It was found that both Al2O3-TiO2-supported catalysts exhibited higher activity than alumina-supported one. The catalyst with a largest TiO2 content (NiW/AT2) demonstrated to be 23 % more active with respect to NiW/Al2O3. Solids were characterized by temperature-programmed reduction (TPR), high resolution transmission electronic microscopy and X-ray photoelectronic spectroscopy (XPS) techniques. A decrease in support-metal interaction (from TPR) was observed when Ti content increased, which could lead to a higher amount of NiWS phase (from XPS). Besides, a slight increase in the slabs length in WS2 was observed for titania-containing catalyst with respect to NiW/Al2O3, indicating that the dispersion can still be optimized. The atomic ratio Al/Ti = 2 of the NiW/Al2O3-TiO2 catalyst proved to be a potential substitute for current catalysts for sulfur reduction in ultra-clean diesel.