Hydrocracking of vacuum residue using NiWS(x) dispersed catalysts

In this study, unsupported nickel-tungsten sulfide (NiWS(x)) particles, where x is the actual molar ratio of Ni/W (x = 0, 0.005, 0.01, 0.02), were prepared, characterized with XRD, XPS, TEM, and EDX elemental mapping, and applied as a dispersed catalyst for upgrading of extra-heavy oil into good-quality liquid products. The hydrocracking reaction of vacuum residue (VR) was carried out at 400 °C with an initial H₂ pressure of 70 bar. It was found that an increase in the Ni content increases the degree of sulfidation of tungsten, promotes formation of Ni-W-S phases, and enhances the overall catalytic activity. Among the NiWS(x) dispersed catalysts, the NiWS(0.02) catalyst showed the highest performance in total liquid product yield (87.0 wt.%), commercial fuel fraction yield (51.9 wt.%), API gravity value of liquid product (14.3°), and sulfur removal conversion (86.5%). In addition, coke formation (4.0 wt.%) was efficiently suppressed, and the C₅-asphaltene conversion (81.8%) was significantly raised.