Hydrodesulfurization and hydrogenation on alumina-supported tungsten and nickel-promoted tungsten catalysts

摘要

Hydrodesulfurization (HDS) of radioactive ~(35)S-labeled dibenzothiophene was carried out over a series of alumina-supported W-based catalysts containing ca. 10-35 wt.% WO_3 and 0-9 wt.% NiO at temperatures in the range 220-400 deg C and under a reaction pressure of 50 kg cm~(-2). The catalytic activities of the catalysts changed depending on the W loadings and sulfidation temperature for W-Al_2O_3 catalysts. Moreover, the HDS and hydrogenation (HYD) activity of W-Al_2O_3 catalysts were remarkably enhanced with the addition of nickel. Further, the amount of labile sulfur (S_0) on the W-Al_2O_3 catalyst was much less than that on the corresponding Mo catalyst although the strength of the W-S bond is weaker than that of Mo-S. This is attributed to the fact that the sulfidation of the W-Al_2O_3 catalyst and the formation of the W-S bond are more difficult. On the other hand, S_0 and the rate constant of H_2S release (k_(RE)) increased significantly on addition of nickel, as in the case of the Co-Mo catalyst. Moreover, the Ni-promoted W-Al_2O_3 catalyst with higher Ni/W ratio (>= 0.6) also showed S_0 and k_(RE) comparable to those of the corresponding Co-Mo catalyst. These results suggested, therefore, that the promoting effect of nickel enhanced the relative ease of sulfidation of W catalysts and resulting in formation of more active sites simultaneously.