Catalytic potential of carbon-supported NiMo-sulfide for ultra-deep hydrodesulfurization of diesel fuel

Carbon-supported NiMo-sulfide (NMC) catalysts were prepared using a variety of active carbons, whose surface area ranged from 916 to 3075 m(2) g(-1), in order to examine the effect of properties of the carbon support on hydrodesulfurization (HDS) activity to 4,6-dimethyldibenzothiophenes (4,6-DMDBT). The HDS activity, measured at 320 degreesC using an autoclave, tended to be enhanced with an increase in the surface area of the active carbon. The increase in the surface area enhanced dispersion of the catalytic active component. The active carbon of rich oxygen functional groups was negatively deflected from the tendency mentioned above because of the restricted dispersion of the active component. For this active carbon, reduction of the oxygen surface groups resulted in enhancing the HDS activity. NMC prepared using the best carbon, whose surface area was the largest (3075 m(2) g(-1)), catalyzed the hydrogenative HDS reaction of the refractory 4,6-DMDBT, as well as DBT, more than the conventional alumina-supported NiMo-sulfide (NMA). In HDS reaction of the real-feedstock using a down-flow tubular reactor with LHSV of 1.5 h(-1) under H-2 pressure of 5 MPa in volumetric H-2/oil ratio of 250 nl l(-1), the best NMC achieved 10 ppm-S at 337degreesC. For NMA, 10 ppm-S was not achieved at even the maximum temperature in the real HDS reaction, 350degreesC. The HDS rate constant was ca. four times larger for the best NMC than for NMA. (C) 2004 Elsevier B.V. All rights reserved.