Enhanced performance of fluorinated Co-Mo-S/AL2O3 and Ni-W-S/Al2O3 catalysts in hydrodesulfurization

Fluorinated Co-Mo-S/Al2O3 was tested as a catalyst for hydrodesulfurization (HDS) of dibenzothiophene and 4,6-dimethyldibenzothiophene, and fluorinated Ni-W-S/Al2O3 for HDS of thiophene and hydrocracking of n-heptane. Fluorine enhanced not only the HDS activity of the catalysts but also the hydrogenation and the cracking activities. The enhanced HDS activity was due to improved dispersion of the active phase, Co-Mo-S or Ni-W-S, in the catalysts caused by the fluorination as observed by temperature programmed reduction and UV-Vis diffuse reflectance spectra of the catalysts. Infrared observation of pyridine adsorbed on the catalysts indicated that the Bronsted acidity was increased by the fluorination, thus promoting the cracking activity of the catalysts.