M. Nagai et al., XPS study of nitrided molybdena/titania catalyst for the hydrodesulfurization of dibenzothiophene, J PHYS CH B, 103(46), 1999, pp. 10180-10188
The relationship between the molybdenum species of nitrided Mo/TiO2 catalys
ts and the HDS activity of the catalysts was studied by XPS and X-ray diffr
action. The HDS of dibenzothiophene was carried out in a fixed-bed microrea
ctor at 573 K and 10.1 MPa of total pressure, The 10.3% MsO3/TiO2 catalyst
was nitrided by a temperature-programmed reaction with ammonia at 4 L h(-1)
at various temperatures. The 1023 K nitrided catalyst held the highest TOF
(based on CO adsorption). From XPS analysis, it was found that the 1023 K
nitrided molybdenum catalyst was significantly difficult to sulfide the sur
face molybdenum species of the nitrided catalyst. The 773 K nitrided cataly
st had more sulfur accumulation and less nitrogen release than the 1023 K n
itrided catalyst. For the Mo/TiO2 nitrided above 973 K, titania was reduced
and nitrided to form TiO and TiN but was not transformed to rutile, The mo
lybdenum oxidation states of the nitrided Mo/TiO2 catalysts decreased with
increasing nitriding temperature, and Mo2+ and Mo-0 ions are predominant on
the surface of the 1023 K nitrided catalyst. The Mo2+ and Mo-0 ions were t
he most active for the HDS of dibenzothiophene.